Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

The impact of human actions on the environment is enormous. Due to a continuous increase in population and the growing industrialization of a globalized world man’s influence on the dynamic of ecosystems and biospheres is steadily expanding. As a result of these augmenting human activities, an increase in the input of atmospheric nitrogen (N) and phosphorus (P) is expected. In a field study in a tropical mountain rain forest in southern Ecuador – an area assumed to be limited in N – permanent plots are fertilized with low amounts of N (50kg/ha/year), P (10kg/ha/year) as well as N and P (50kg/ha/year and 10 kg/ha/year respectively), thereby simulating higher nutritional dispositions in the respective plots. Because varying nutritional dispositions have the greatest effect on seedlings, this thesis’ aim is to examine to what extent applications of N and P can influence the growth and abundance of seedlings, thus affecting the tree regeneration in tropical montane forests. A total of 626 plants between 5 and 150 cm in height have been measured. Among the most common families were Rubiaceae, Melastomataceae, Myrtaceae, Arecaceae and Euphorbiaceae. The most commonly encountered tree species were Graffenrieda emarginata Triana (Melastomataceae) and Myrcia spec. nov. (Myrtaceae). Considering the total number of measured seedlings, N in general seems to have a positive effect on tree regeneration. A generally increased growth in height and stem diameter on the Nand NP-plots proves that N is a limiting factor in this mountain rain forest. Additions of P, on the contrary, do not show any effects on the plants, wherefore P does not seem to be a controlling factor for tree regeneration in this tropical mountain rain forest. However, fertilization of N does not have a positive effect in growth on every family. Whereas the Euphorbiaceae and Melastomataceae families were able to increase their growth on Nand NP-plots, Arecaceae only show positive effects on NP-plots. Altogether without any gain from N-additions seem to be the Myrtaceae and Rubiaceae families. Moreover, the tree density of Rubiaceae was even significantly reduced on Nand NP-plots. Especially an increased leaf area loss on the Nand NP-plots presents an elevated risk for plant families such as Myrtaceae and Rubiaceae, because they do not seem to have the ability to compensate the increased leaf area loss by an augmented growth rate. However, a higher appearance and growth of Euphorbiaceae and Melastomataceae due to an increased nutritional input is to be expected in the future. In the long term this development might cause the extinction of their current habitat of the Myrtaceae and the Rubiaceae families, the latter being the currently most widely spread family. As a consequence, it is to be expected that G. emarginata will increasingly emerge as the dominant species, whereas Myrcia spec. nov. will probably play a minor role. Obviously the various tree species have a different need for N, which causes diverse thresholds in N-tolerance.

Abstract:

The thermal structure of a megadiverse mountain ecosystem in southern Ecuador is examined on the basis of temperature measurements inside the natural mountain forest and at open sites along an altitudinal gradient from 1700m to 3200m. The data is used to calculated maps of monthly average minimum, mean and maximum 2m air temperature for the period 1999-2007, needed by ecological projects. The maps are generated by combining the straightforward detrending technique by using a Digital Elevation Model and satellite-based land cover classification. The results reveal a clear thermal differentiation over the year, partly triggered by the change of synoptic weather situation but also by land cover effects. Thermal amplitudes are particularly low during the main rainy season when cloudiness and air humidity are high but markedly pronounced in the relative dry season when daily irradiance and outgoing nocturnal radiation causes distinct differences between the land cover units. Particularly the lower pasture areas gained by slash and burn of the natural forest exhibit the most extreme thermal conditions while the atmosphere inside the mountain forest is slightly cooler due to the regulating effects of the dense vegetation. Thus, clearing the forest clearly reduces the thermal regulation function (regulating ecosystem services) of the ecosystem which might become problematic under future global warming.

Abstract:

Forest-to-pasture conversion has been reported to increase soil organic matter (SOM) in mineral topsoils in the tropical mountain rainforest region of south Ecuador, with subsequent decreases following pasture abandonment. Until now the mechanisms behind these changes have not been fully understood. To elucidate their varied preservation patterns, we analysed root- and shoot-derived organic matter and assessed their contribution to the formation of SOM in topsoils (0?5 cm) on a chronosequence of pastures (Setaria sphacelata (Schumach.); C4) established after slash and burn of the natural forest (diverse C3 plant species) and an abandoned pasture site invaded by bracken fern (Pteridium arachnoideum (Kaulf.) Maxon.; C3). Cutin and suberin biomarkers of the two plant species (grass and bracken) and of forest litter were identified after saponification and their contribution to SOM was studied by compound-specific stable carbon isotope analyses. Our results showed specific root and shoot biomarkers for the two plant species and for forest litter, which often did not correspond to the classification of root-versus shoot-specific monomers reported in the literature. This illustrates the importance of direct biomarker determination rather than using results from studies with different plants. Shoot- as well as root-derived OM of forest and grass origin contributed to the stable SOM pool with decadal turnover times. Forest-derived monomers contributed more to the stable SOM pool compared with grass-derived monomers. ω-hydroxy carboxylic acids and α,ω-alkanedioic acids of forest origin may have been stabilized in these tropical soils by bonding to soil minerals. Rapid degradation of grass-derived lipids from the same compound classes suggests a saturation of the mineral binding capacity. In pasture soils, the accumulation of SOM was mainly driven by large inputs of root OM. The accumulated SOM during pasture use is, however, lost rapidly after abandonment.

Abstract:

The dependence of aboveground biomass and productivity of tropical forests on soil fertility is not fully understood, since previous studies yielded contrasting results. Here, we quantify aboveground biomass (AGB) and stem wood production, and examine the impact of soil chemistry on these parameters in mature tropical forest stands of the equatorial Andes in Ecuador. In 80 plots of 0.04 ha at four elevation levels (500, 1,000, 1,500 and 2,000 m a.s.l., total sample area = 3.2 ha), we measured ten important soil chemical parameters, inventoried all trees ¸10 cm dbh and monitored stem diameter growth with dendrometer tapes in 32 plots. Top canopy height and stem density signiWcantly decreased from 500 to 2,000 m, while tree basal area increased and AGB remained invariant (344 § 17 Mg DM ha¡1, mean § SE) with elevation. Wood speciWc gravity (WSG) showed a signiWcant, but small, decrease. Stem wood production decreased from 4.5 to 3.2 Mg DM ha¡1 year¡1 along the transect, indicating a higher biomass turnover at lower elevations. The only soil variable that covaried with AGB was exchangeable K in the topsoil. WSG increased with decreases in N mineralisation rate, soil pH and extractable Ca and P concentrations. Structural equation modelling (SEM) revealed that nitrogen availability acts on stem wood production only indirectly through a negative relation between N mineralisation rate and WSG, and a positive eVect of a lowered WSG on stem growth. The SEM analysis showed neither direct nor indirect eVects of resin-extractable P on wood production, but a negative P inXuence on AGB. We conclude that nitrogen availability signiWcantly inXuences productivity in these Andean forests, but both N and P are aVecting wood production mainly indirectly through alterations in WSG and stem density; the growth-promoting eVect of N is apparently larger than that of P.

Abstract:

In tropical mountains, trees are the dominant life form from sea level to above 4,000-m altitude under highly variable thermal conditions (range of mean annual temperatures: <8 to >28C). How light-saturated net photosynthesis of tropical trees adapts to variation in temperature, atmospheric CO2 concentration, and further environmental factors, that change along elevation gradients, is not precisely known. With gas exchange measurements in mature trees, we determined light-saturated net photosynthesis at ambient temperature (T) and [CO2] (Asat) of 40 tree species from 21 families in tropical mountain forests at 1000-, 2000-, and 3000-m elevation in southern Ecuador. We tested the hypothesis that stand-level averages of Asat and leaf dark respiration (RD) per leaf area remain constant with elevation. Standlevel means of Asat were 8.8, 11.3, and 7.2 lmol CO2 m-2 s-1; those of RD 0.8, 0.6, and 0.7 lmol CO2 m-2 s-1 at 1000-, 2000-, and 3000-m elevation, respectively, with no significant altitudinal trend. We obtained coefficients of among-species variation in Asat and RD of 20?53% (n = 10?16 tree species per stand). Examining our data in the context of a pan-tropical Asat data base for mature tropical trees (c. 170 species from 18 sites at variable elevation) revealed that area-based Asat decreases in tropical mountains by, on average, 1.3 lmol CO2 m-2 s-1 per km altitude increase (or by 0.2 lmol CO2 m-2 s-1 per K temperature decrease). The Asat decrease occurred despite an increase in leaf mass per area with altitude. Local geological and soil fertility conditions and related foliar N and P concentrations considerably influenced the altitudinal Asat patterns. We conclude that elevation is an important influencing factor of the photosynthetic activity of tropical trees. Lowered Asat together with a reduced stand leaf area decrease canopy C gain with elevation in tropical mountains.

Abstract:

The moth genus Eois Hu¨ bner (Lepidoptera: Geometridae: Larentiinae) comprises 254 validly described species, 211 of them (83%) occurring in the Neotropical region, 12% in the Asian-Australian region, and 5% in Africa. A checklist of Neotropical Eois is provided and some taxonomic changes are made. Aplogompha noctilaria (Schaus) is excluded from the genus, and Eois bermellada (Dognin) and Eois fragilis (Warren) are transferred to the genus. Further changes include Eois cellulata (Prout) stat. rev., Eois ambarilla (Dognin) stat. rev., and Eois telegraphica Prout stat. rev. By far, the majority of Eois species (82%) were described between 1891 and 1920; approximately half of all species by just two authors. Within the Neotropical region, the majority of species (55%) were described from the tropical Andes (Colombia, Ecuador, Peru, and Bolivia), followed by Central America and the Caribbean (28%), and the rest of South America (17%). Large regions such as the Amazon basin, eastern South America, but also northern Peru are heavily underrepresented. Regional diversity studies provide evidence that the wet tropical Andes are the diversity hotspot of Eois. From a forested elevational gradient (1,020Ð2,670 m above sea level) in southeastern Ecuador, 154 morphospecies are currently known, with only 12% of them described. Regional species richness in Central America is lower (Costa Rica, 66 observed morphospecies along a gradient from 40 to 2,730 m; 29% described). Total richness of the genus is estimated to be 1,000 species in the Neotropical region. If the low proportions of described species only partly recur in other groups of Neotropical geometrid moths, their number may exceed 19,000 species. A taxonomic revision of Eois will be a prerequisite for comparison of ecological data from different regions.

Abstract:

Caterpillar ensembles were sampled on 16 species of shrubs from the family Asteraceae and the genus Piper (Piperaceae) in open and forest habitats in the Andean montane forest zone of southern Ecuador between August 2007 and May 2009. Trophic affiliations of caterpillars to the host plants were confirmed in feeding trials. Overall, species richness of herbivorous caterpillars was high (191 species across all plants), but varied strongly between ensembles associated with different plant species (2–96 lepidopteran species per shrub species). Ensembles on Piper species were characterized by low effective species numbers and high dominance of one or two species of the Geometridae genus Eois Hübner. Low species number and high dominance were also found on latex-bearing Erato polymnioides, whereas ensembles on two other Asteraceae species were far more diverse and less strongly shaped by a few dominant species. The observed diversity patterns fit well to the concept that anti-herbivore defenses of plants are the major factors regulating associated insect ensembles. Local abundance and geographic range of host plants appear to have less influence. Lepidopteran species feeding on Asteraceae were found to be more generalistic than those feeding on Piper species. We conclude that caterpillar ensembles on most, but not all, studied plant species are defined by a small number of dominant species, which usually are narrow host specialists. This pattern was more distinct on Piper shrubs in forest understory, whereas Asteraceae in disturbed habitats had more open caterpillar ensembles.

Abstract:

While many studies analyse patterns of tropical land management with a backward-oriented approach that utilises data of the past, we propose to consider future-oriented modelling approaches to find sustainable land-use options. This proposal is illustrated with application examples for advanced growth modelling in tropical forests, a short overview on financial performance analyses for tropical land uses, and the introduction of a newmodelling approach. Thismodelling approach sees tropical land management as a financial portfolio of land-use options. Its advantage is the ability to make transparent effects of financial risk reduction that arise from mixing forestry and agriculture-based land-use options. The approach thus does not analyse land uses as stand-alone options, like most other analyses do. The land-use portfolio modelling shows that sustainable land use may also be financially attractive for farmers, if abandoned farm lands are reforested (with a native tree species in our case) and sustainable management in natural forests is carried out. We conclude that the combination of advanced growth with sound financial modelling may lead to improved bioeconomic models. Developed bioeconomic models are necessary to increase the biological realism and acceptability of the results obtained.

Abstract:

We usually have only limited knowledge about the economic consequences of land-use decisions, thus they are uncertain. We analyze the implications of this uncertainty on conservation payments (CP) to preserve wildlife-friendly shade coffee production in southwest Ecuador, when conversion to maize is the most profitable alternative. Our objective is twofold: First, we analyze the consequences of applying Stochastic Dominance (SD) to derive CP, an approach making only minimal assumptions about the preferences of farmers. Second, we investigate the effects of land-use diversification to reduce CP by allowing for shade coffee on part of a landholding, and maize production on what remains. CP derived by SD turned out to be at least twice the amount calculated by an alternative method which maximizes a concave utility function?US$ 166 to US$ 294 ha-1 year-1 instead of US$ 86 ha-1 year-1. Given this result, we doubt that the assumptions underlying SD are reasonable for farmers, who are known to be riskaverse. Allowing for land-use diversification has a significant impact on CP. The optimal portfolio share of shade coffee is 27 % and for maize 73 % for moderately risk-averse farmers?without any CP. A larger share of shade coffee is preferable for strongly risk-averse farmers?51 and 49 % maize. The amount of CP necessary to encourage the expansion of shade coffee to 75 %is US$ 40 ha-1 year-1 (for moderately risk-averse) and US$ 19 ha-1 year-1 (for strongly risk-averse farmers). Stimulating diversification may thus help to significantly reduce CP necessary to preserve less profitable agroforestry options.

Abstract:

Tropical mountain forest in the Andes of southeastern Ecuador is regularly destroyed to gain pasture land by cultivating the C4 grass Setaria sphacelata. After recurrent burning of the pastures, the grass is partly outcompeted by the C3 southern bracken (Pteridium arachnoideum). This competition represents the problematic of pasture degradation and increasing deforestation, due to the necessity of new pasture land. Because no information on the growth potential of both species in the Andes of Ecuador is available, a growth simulation model has been improved and properly parameterized with field observations. The measured speciesand site-specific physiological and edaphic parameters are presented in this paper, as well as the model validation with field observations of leaf CO2 assimilation. The validation showed deviations of simulated from observed leaf net assimilation lower than 5% of the observed values. The validated model was run with a fully realistic meteorological forcing of the year 2008 (10 min time step). The main result points to slightly higher growth potential of Setaria with 5879 g m-2 a-1, based on an annual CO2 net assimilation rate of 217 mol CO2m-2 a-1. The calculated growth potential of bracken was 5554 g m-2 a-1, based on the CO2 net assimilation of 197 mol CO2m-2 a-1. In addition, it was shown that decreasing incoming solar radiation and low temperature are favourable weather conditions for bracken in contrary to the pasture grass Setaria.

Abstract:

Tropical mountainous cloud forests belong to the most diverse ecosystems on earth. If you ask scientists which features characterize these ecosystems, then the answers are as diverse as is the flora and fauna within them: persistent cloud cover, reduced solar radiation due to cloud cover, distinctly structured vegetation forms, suppressed evapotranspiration as a consequence of high relative humidity, stripping of clouds by tree canopies and resulting large amount of throughfall, reduced canopy heights, high rainfall rates, gnarled tree trunks at increasing altitudes, substantial epiphyte biomass, moss-covered stems, organic rich and typically wet soils, and – last but not least – extremely high biodiversity with a paramount endemism (Bruijnzeel et al., 2011).

Abstract:

Landslides are a hazard for humans and artificial structures. From an ecological point of view, they represent an important ecosystem disturbance, especially in tropical montane forests. Here, shallow translational landslides are a frequent natural phenomenon and one local determinant of high levels of biodiversity. In this paper, we apply weighted ensembles of advanced phenomenological models from statistics and machine learning to analyze the driving factors of natural landslides in a tropical montane forest in South Ecuador. We exclusively interpret terrain attributes, derived from a digital elevation model, as proxies to several driving factors of landslides and use them as predictors in our models which are trained on a set of five historical landslide inventories. We check the model generality by transferring them in time and use three common performance criteria (i.e. AUC, explained deviance and slope of model calibration curve) to, on the one hand, compare several state-of-the-art model approaches and on the other hand, to create weighted model ensembles. Our results suggest that it is important to consider more than one single performance criterion. Approaching our main question, we compare responses of weighted model ensembles that were trained on distinct functional units of landslides (i.e. initiation, transport and deposition zones). This way, we are able to show that it is quite possible to deduce driving factors of landslides, if the consistency between the training data and the processes is maintained. Opening the ?black box? of statistical models by interpreting univariate model response curves and relative importance of single predictors regarding their plausibility, we provide a means to verify this consistency. With the exception of classification tree analysis, all techniques performed comparably well in our case study while being outperformed by weighted model ensembles. Univariate response curves of models trained on distinct functional units of landslides exposed different shapes following our expectations. Our results indicate the occurrence of landslides to be mainly controlled by factors related to the general position along a slope (i.e. ridge, open slope or valley) while landslide initiation seems to be favored by small scale convexities on otherwise plain open slopes.

Abstract:

Shallow landslides are an important type of natural ecosystem disturbance in tropical montane forests. Due to landslides, vegetation and often also the upper soil layer are removed, and space for primary succession under altered environmental conditions is created. Little is known about how these altered conditions affect important aspects of forest recovery such as the establishment of new tree biomass and species composition. To address these questions we utilize a process-based forest simulation model and develop potential forest regrowth scenarios. We investigate how changes in different trees species characteristics influence forest recovery on landslide sites. The applied regrowth scenarios are: undisturbed regrowth (all tree species characteristics remain like in the undisturbed forest), reduced tree growth (induced by nutrient limitation), reduced tree establishment (due to thicket-forming vegetation and dispersal limitation) and increased tree mortality (due to post-landslide erosion and increased susceptibility). We then apply these scenarios to an evergreen tropical montane forest in southern Ecuador where landslides constitute a major source of natural disturbance. Our most important findings are (a) On the local scale of a single landslide tree biomass recovers within the first 80 years after landslides for most scenarios, but it takes at least 200 years for the post-landslide forest to reach a structure (in terms of stem size distribution) similar to a mature forest. On this scale forest productivity is reduced for most regrowth scenarios. Changes in different tree species characteristics produce distinct spatio-temporal patterns of tree biomass distribution in the first decades of recovery within the landslide disturbed area. These patterns can potentially be used for identifying the dominant processes that drive forest recovery on landslide disturbed sites. (b) On the larger scale of the landscape overall tree biomass is reduced by 9?15% due to landslide disturbances. Overall forest productivity is only slightly reduced (<6%), but landslides increase landscape heterogeneity and produce hotspots of biomass loss and ?blind spots? of forest productivity. Thus landslides have a strong impact on the distribution of biomass in tropical montane forests. This study demonstrates that dynamic forest models are useful tools for complementing field based studies on landslides; they allow for testing alternative hypotheses on different sources of heterogeneity across spatial scales and investigating the influence of landslides on long-term forest dynamics.

Abstract:

Understanding pasture degradation processes is the key for sustainable land management in the tropical mountain rainforest region of the South Ecuadorian Andes. We estimated the stocks of total carbon and nutrients, microbial biomass and different P fractions along a gradient of land-uses that is typical of the eastern escarpment of the Cordillera Real i.e., old-growth evergreen lower montane forest, active pastures (17 and 50 years-old), abandoned pastures 10 and 20 years old with bracken fern or successional vegetation. Conversion of forest to pasture by slashand- burn increased the stocks of SOC, TN, P and S in mineral topsoil of active pasture sites. Microbial growth in pasture soils was enhanced by improved availability of nutrients, C:N ratio, and increased soil pH. Up to 39 %of the total P in mineral soil was stored in the microbial biomass indicating its importance as a dynamic, easily available P reservoir at all sites. At a 17 years-old pasture the stock of NH4F extractable organic P, which is considered to be mineralisable in the short-term, was twice as high as in all other soils. The importance of the NaOH extractable organic Ppool increased with pasture age. Pasture degradation was accelerated by a decline of this P stock, which is essential for the long-term P supply. Stocks of microbial biomass, total N and S had returned to forest levels 10 years after pasture abandonment; soil pH and total P 20 years after growth of successional bush vegetation. Only the C:N ratio increased above forest level indicating an ongoing loss of N after 20 years. Soil nutrient depletion and microbial biomass decline enforced the degradation of pastures on the investigated Cambisol sites.

Abstract:

The World Reference Base for Soil Resources (WRB) (FAO, IUSS Working Group WRB, 2007) at present does not acknowledge the spatial soil continuum, but provides a sound basis to do so. Using methods from statistical learning theory to develop digital soil maps is much more efficient and precise while regionalising soil diagnostic properties instead of complex entities such as the soil units assigned by the WRB. Particularly in providing spatial soil information displayed in digital soil maps, any aggregation of this spatial soil information to soil units means a loss of information. The soil landscape can be systematically described in its spatial continuum simply by the vertical order and extent of the WRB diagnostic horizons. The diagnostic horizons are related in their thickness to a standard depth and listed from top to bottom in order of appearance. Typical diagnostic horizon thickness and occurrence probability were predicted from terrain parameters by classification and regression trees (CART), throughout the research area in southern Ecuador. The two disadvantages of CART, abrupt prediction class boundaries and dependence on the dataset, were addressed by hundredfold model runs on different data subsets, leading to a range of possible predictions. Prediction uncertainty was included in the digital soil maps by calculating these predictions' means and standard deviations as well as by horizon occurrence probability prediction. Model performance was evaluated by means of hundredfold external cross validation. Terrain parameters were found to have a strong influence on diagnostic topsoil properties. However, no influence on the vertical profile differentiation was observed. Hence predicting horizon thickness and subsoil diagnostic properties was difficult. The systematic description of the soil continuum of this particular soillandscape resulted in histic and stagnic soil parts dominating the first 100 cm of the soil column for most of the area.

Abstract:

The main objective of this dissertation was to identify the rainfall runoff processes that control the discharge generation of the study areas. The research uses multi techniques including hydrometric data analysis, tracers (isotopes and chemical constituents) and conceptual modeling. The research questions were (i) in which way streamflow is controlled by micro-climate, precipitation pattern, slope, land cover and soil properties, amongst other catchment properties?, (ii) what are the main sources of water within the study areas?, and how the soil properties are influencing the runoff generation?, and (iii) could the identified conceptual model, using previous knowledge, be applied for the studied areas in the south of Ecuador?

Abstract:

Parallel to the proceeding destruction of the megadiverse mountain forests of Ecuador more and more plantations with exotic Pinus and Eucalyptus species are being established. An ecologically reasonable reforestation could help to solve the problem. Such a reforestation can only be achieved by using indigenous species. As the harvest of seeds is problematic, plant material has to be produced by means of vegetative propagation. However, we have been lacking a knowledge base and efficient methods for cloning native tree species so far. ? In the present thesis the potential to vegetatively propagate as well as the carbohydrate and phytohormone content of the following six tree species ? naturally occurring in the mountain forests of Southern Ecuador ? were examined: Clethra revoluta (Clethraceae), Heliocarpus americanus (Tiliaceae), Isertia laevis (Rubiaceae), Myrica pubescens (Myriaceae), Piptocoma discolor (Asteraceae) and Tabebuia chrysantha (Bignoniaceae). ? Despite variegated variations of the propagation conditions over 1 ½ years we did not succeed in obtaining rooted stem cuttings of adult trees. The plants withered rapidly. Measurements of stomatal leaf conductance show an insufficient regulation of the stomata associated with high transpiration rates. Although the production of rooted stem cuttings of adult trees by air-layering was successful, these plants withered after placing them in soil, too. ? The carbohydrate measurements resulted in annual fluctuations in several species concerning their starch and soluble sugar content ? especially for the raffinose family (Tabebuia); an increased inositol content during the drier months could also be observed in all species. Although the total carbohydrate content showed clear seasonal fluctuations in the leaves (Heliocarpus-, Myrica and Tabebuia plants) no definite fluctuations could be detected in the twigs at all. Whereas Heliocarpus and Tabebuia trees stored reserve carbohydrates with a content of 6 or 9.5 %, respectively (especially in the form of starch as well as glucose, fructose and sucrose) the low carbohydrate supply in the twigs of Clethra and Piptocoma during the whole year could have been detrimental to successful adventive rooting. ? It is presumed that the endogenous content of cytokinins (initiation of root primordia) and auxins (root growth) is especially important for the rooting of cuttings. The measured phytohormone status fluctuates depending on season and species. A hormone status suitable for the root formation (= a high auxin : cytokinin ratio) was found in Heliocarpus and Tabebuia in the months with the highest precipitation rates. On the contrary Clethra and Myrica contained hardly any auxin but relatively much cytokinin. Thus rooting seems to be especially difficult with these species. ? As it is not possible to interfere in the hormone status of adult trees, young plants were used as donor plants for their hormone and metabolic reserve status can be changed adequately by stressing treatments. We especially aimed at lowering the cytokinin level endogenously. For these experiments Heliocarpus and Tabebuia were selected and exposed to shortage of water, nutrients or root space as well as combinations of these stress factors. Additionally wildlings (saplings) were used. ? This strategy turned out to be successful because from all treatments 42 % of the Heliocarpus and 15 % of the Tabebuia cuttings rooted on average. The most successful cuttings originated from Heliocarpus treelets exposed to water shortage (70 % rooting) and from Tabebuia plants exposed to nutrient shortage (15 %). Wildlings of Tabebuia also grew roots effectively (45 %). Even better results in the two species were achieved by air-layering. ? The pretreatments resulted in an increase of the carbohydrate content (except for Tabebuia plants under water shortage). However, no statistically significant correlation aroused between the carbohydrate content of the differently stressed donor plants and the rooting percentage. ? As assumed the stressful pretreatment of the donor plants of both species caused a lower cytokinin level whereas at least in Tabebuia a significantly negative correlation between the rooting of cuttings and the cytokinin content of the donor plants was found (rs up to -0.93). ? The results of this thesis clearly show that even young twigs of adult tropical trees have virtually no rooting potential. In young plants this potential can be activated by stress whereas the accumulation of metabolic reserves and the decrease of the cytokinin level had a beneficial influence on the rooting percentage. This constellation was rather developed in Tabebuia than in Heliocarpus. ? Due to the possibility of making at least two cuttings from one donor plant the establishment of a cultivation of cloned material for reforestation is ? although time-consuming ? definitely feasible.

Abstract:

We investigated the role of carbon, nitrogen and phosphorus as limiting factors of microorganisms and microbial grazers (testate amoebae) in a montane tropical rain forest in southern Ecuador. Carbon (as glucose), nitrogen (as NH4NO3) and phosphorus (as NaH2PO4) were added separately and in combination bimonthly to experimental plots for 20 months. By adding glucose and nutrients we expected to increase the growth of microorganisms as the major food resource of testate amoebae. Th e response of microorganisms to experimental treatments was determined by analysing microbial biomass (SIR), fungal biomass and microbial community composition as measured by phospholipid fatty acids (PLFAs). We hypothesized that the response of testate amoebae is closely linked to that of microorganisms. Carbon addition strongly increased ergosterol concentration and, less pronounced, the amount of linoleic acid as fungal biomarker, suggesting that saprotrophic fungi are limited by carbon. Microbial biomass and ergosterol concentrations reached a maximum in the combined treatment with C, N and P indicating that both N and P also were in short supply. In contrast to saprotrophic fungi and microorganisms in total, testate amoebae suff ered from the addition of C and reached maximum density by the addition of N. Th e results indicate that saprotrophic fungi in tropical montane rain forests are mainly limited by carbon whereas gram positive and negative bacteria benefi t from increased availability of P. Testate amoebae suff ered from increased dominance of saprotrophic fungi in glucose treatments but benefi ted from increased supply of N. Th e results show that testate amoebae of tropical montane rain forests are controlled by bottom?up forces relying on specifi c food resources rather than the amount of bacterial biomass with saprotrophic fungi functioning as major antagonists. Compared to temperate systems microbial food webs in tropical forests therefore may be much more complex than previously assumed with trophic links being rather specifi c and antagonistic interactions overriding trophic interactions.

Abstract:

We investigated changes in diversity and density of testate amoebae in epiphytes of trees in tropical montane rain forests of southern Ecuador. Local ? microscale [height on tree trunk of 0 (base of tree trunk), 1 and 2 m; TH I, TH II and TH III, respectively] and regional ? macroscale (forests at 1000, 2000 and 3000 m) changes were investigated. At the macroscale diversity and density of testate amoebae peaked at 2000 m. At the microscale diversity reached a maximum at TH I, whereas density reached a maximum at TH III. The percentage of empty shells at the macroscale was at a maximum at 2000 m and at the microscale at TH I, whereas the percentage of live cells was at a maximum at 3000 m and at TH III. The diversity of testate amoebae in epiphytes found in the present study was high (113 species). However, only two to nine species were dominant representing 54?85 percent of total living testate amoebae. The results suggest significant variations in density and diversity of testate amoebae at both the micro- and macroscale. However, for testate amoebae density the macroscale appears most important whereas changes in diversity are more pronounced at the microscale.

Abstract:

Litter quality and diversity are major factors structuring decomposer communities. However, little is known on the relationship between litter quality and the community structure of soil protists in tropical forests. We analyzed the diversity, density, and community structure of a major group of soil protists of tropical montane rainforests, that is, testate amoebae. Litterbags containing pure and mixed litter of two abundant tree species at the study sites (Graffenrieda emarginata and Purdiaea nutans) differing in nitrogen concentrations were exposed in the field for 12 months. The density and diversity of testate amoebae were higher in the nitrogen-rich Graffenrieda litter suggesting that nitrogen functions as an important driving factor for soil protist communities. No additive effects of litter mixing were found, rather density of testate amoebae was reduced in litter mixtures as compared to litterbags with Graffenrieda litter only. However, adding of high-quality litter to low-quality litter markedly improved habitat quality, as evaluated by the increase in diversity and density of testate amoebae. The results suggest that local factors, such as litter quality, function as major forces shaping the structure and density of decomposer microfauna that likely feed back to decomposition processes.

Abstract:

The tropical Andes in southern Ecuador constitute a hotspot of plant (especially trees and bryophytes) and animal (especially birds, bats, arctiid and geometrid mothes) diversity. However, data on small animals such as testate amoebae as an important component of the soil and aboveground community are lacking. Variations in density, diversity and community structure of testate amoebae along altitudinal transects in tropical regions are largely unknown. Testate amoebae colonize almost any habitat but are most abundant and diverse in soils with high humidity, high organic content and slow rates of decomposition. They preferentially feed on certain bacteria thereby affecting the taxonomic composition and metabolic activity of microbial communities. By altering microbial activity testate amoebae affect nutrient cycling in particular in ecosystems where earthworm populations are depleted. The present thesis investigates the density and diversity of testate amoebae in litter, soil and aboveground habitats along an elevational gradient of tropical mountain rain forests in southern Ecuador, evaluates correlations with biotic and abiotic factors, and proves the role of nutrient limitation.

Abstract:

Global biodiversity is threatened by climate and land cover change. The research unit "Biodiversity and Sustainable Management of a Megadiverse Mountain Ecosystem in South Ecuador" (FOR 816) funded by the German research council (Deutsche Forschungsgemeinschaft, DFG) is working in one of the hottest hotspots of biodiversity of the world. In this region the pressure from the local population on the environment is severe resulting in a high deforestation rate. Sustainable management systems have to be developed on a regional scale to counteract the loss of livelihood of the local population. Numerical models are capable to investigate the changes of the mentioned future land cover changes and its response to climatic and hydrologic variability. The chance to test numerously land use scenarios without interfering into the real environment offers the possibility to investigate and to evaluate the proposed management strategies. The presented work targets at an analysis of the impact of the predicted land cover changes in respect of the ecosystem services of climate and water regulation. Therefore a state-of-the-art land surface model called "Community Land Model" (CLM) is setup in a regional scale. The parametrization of the vegetation is implemented using plant functional types (PFT). The PFTs are defined a priori with vegetation classes based on ecological field surveys. Three central hypotheses are formulated to support the parametrization of the model. The completed work offers a regionalized model setup to analyze different land cover developments in reference to energy and water fluxes between the soil, the vegetation and the atmosphere under changing climatic conditions. Besides the appraisal of the stated hypotheses other innovative contributions are made. The new values for the pre-installed CLM-PFT of tropical evergreen trees add to the current improvements made to the CLM.

Abstract:

Tropical forests are well known for their exceptional species richness ? high diversity of plant species constitute the basis for an equivalently rich fauna. An astonishing variety of plant life strategies has evolved, manifesting itself also in different compositions of life history traits in trees. This thesis investigates the role of tree life history traits (growth, mortality and recruitment) on different processes structuring species-rich forests. Our study system is a montane rainforest located in the Tropical Andes hotspot of biodiversity in southern Ecuador. Here, we find a mosaic of steep ridges and deeply incised valleys, covered with predominantly broadleaf forest. Forest structure and species composition differ considerably depending on altitude and topographic position. The forest cover is frequently interrupted by scars of landslides, which constitute an important type of natural disturbance in this ecosystem. We utilize ecological models as tools to gain deeper insights into key processes driving the maintenance of tree species richness and affecting forest recovery after landslides. The first part of this thesis concerns the question of species coexistence. We develop a theoretical model to analyze how different trade-offs between life history traits (tree growth, seed dispersal, tree mortality) affect tree species coexistence. We find that the considered trade-offs alone are not sufficient to explain long-term species coexistence. Additional ?stabilizing? mechanisms seem to be indispensable to facilitate coexistence in species-rich forests. Such mechanisms could result from biotic interactions, that alter the relation between inter- and intra-specific competition depending on (local) species abundances (e.g. density-dependent mortality). Other possible coexistence mechanisms likely to be relevant to our particular study system are driven by external, abiotic factors like a complex topography resulting in locally differing habitat types (each supporting a different set of species), or the character of a prevailing disturbance regime (e.g. shallow landslides). In the second part of the thesis, we investigate the growth dynamics of the ridge forest in our study system. To this end, we utilize the process-based forest growth model FORMIND. We show that after calibration, the model successfully reproduces forest dynamics on different levels of complexity (e.g. basal area and stem size distribution). We then use this forest model to investigate the influence of landslide disturbances on forest dynamics both on the local scale of a single landslide and on the landscape scale. On landslide sites, changes in environmental conditions might lead to changes in different tree life history traits. We analyze scenarios with changes in different traits (tree recruitment, tree growth, tree mortality) and find that while tree biomass can recover within the first hundred years after a landslide, the time until forest structure and species composition is restored is considerably longer (approximately 200 years). Changes in different traits result in differing spatial distributions of tree biomass: reduced tree growth leads to a more homogeneous distribution of biomass, whereas reduced recruitment and increased mortality yield a more heterogeneous biomass distribution (?patchy? vegetation). On the landscape level, overall forest biomass is substantially reduced by landslides (8 - I 14%), compared to only 2 -3% of the area marked by visible traces of landslides. Thus this particular type of disturbance considerably influences the total forest carbon balance. In a complementary investigation we study abiotic and biotic factors that potentially trigger landslide occurrence in our study system. For this, we develop an extension of a standard physically-based model of slope stability. We find that due to the predominantly shallow tree roots, some of the observed landslides might be triggered by the vegetation itself. This thesis demonstrates that ecological models are useful tools to gain deeper insights into important processes shaping forest communities. They can be applied for theoretical questions such as the question of species coexistence, as well as for more applied, management related questions like predicting forest recovery after disturbances.

Abstract:

The tropical mountain rain forests in Southern Ecuador belong to one of the five global hot spots of biodiversity. At the same time it is one of the most endangered ecosystems in the world due to the continuous and accelerated deforestation over the last 50 years. The aim of this study was to contribute to a sustainable use of natural resources as well as to ask for sustainable strategies of land use in the tropical mountain rain forest, analyzing the use and the management of natural resources (forest, soil and water) by the Saraguros and Mestizos in the watershed of Tambo Blanco. The study area (115 Km²) is located in the Eastern Andes between 1,680 - 3,400 m a.s.l., representing an example of a new colonized region in the 1960s, which is part of the protected forest area Corazón de Oro and the Biosphere Reserve Podocarpus - El Cóndor. The investigation focused on the following topics: land use change since the beginning of the agricultural colonization, the use and the management of natural resources, the practices and strategies for the conservation of natural resources by the local people, as well as the evaluation of the use of natural resources forest, soil, and water under the terms of sustainability. The qualitative and quantitative land use change was analyzed for the years 1976, 1987 and 2001, through the use of remote sensing and geographical information system (GIS). Use and management of natural resources by the local people was evaluated on the basis of further geographical methods like observations, interviews (100 half standardized interviews, 20 expert interviews) and land use mapping. The results of land use change showed, that the tropical mountain rain forest had been reduced about 22 % (1,695.597 ha) during 25 years, representing an average of 67.82 ha/year, mainly due to the transformation of natural forests into pasture land. Páramo areas over 3,000 m a.s.l. remained almost unchanged. That indicates that the land use change was concentrated in the tropical mountain forest between 1,600 and 2, 800 m a.s.l. Overall, between 1976 and 2001, the rate of deforestation (0.99 %) was very high. How-ever, the first period between 1976 and 1987 showed a higher deforestation rate (1,16 %) than the last period between 1987 and 2001 (0,86 %). The main reasons for a decreasing deforestation rate seemed to be the establishment of livestock farming as well as the concomitant reduction of forestry, as a result of a deficiency of precious wood and a price decline of timber. Despite a diminishing timber industry over the last years, the establishment of livestock farming as the new principal economic activity has lead to a continuing deforestation of tropical mountain forests. The concentration in only one economical activity, like livestock farming does not resolve the problems of poverty in the investigation area. In addition, the local people depend mainly on one single economic activity and on the prices dictated by external markets. For SUMMARY 186 these reasons there is a continuous loss of traditional practices such as the cultivation in chacras und huertas for the subsistence of the family and, not least, a loss of biodiversity in the tropical mountain forests of Southern Ecuador. Despite these negative scenarios, it must be recognized, that the local people have also development practices and strategies for the conservation of natural resources throughout the accumulated experience of many decades. This includes, for example, reforestation, planting of ?living fences?, conservation of particular forest areas, introduction of silvopastoral systems, weed control with the machete instead of burning, sowing of fast growing grasses, rotation of pastures, use of organic fertilizer, etc. For a sustainable development within the study area, the solution of ecological and economical problems like poverty, unemployment and lack of education will be required. Therefore the cooperation of governmental and non-governmental organizations, research institutions and local people is very important. Despite the problems for sustainable development in tropical mountain forests, practical measures to overcome the problems can be identified, including reforestation with native tree species, the implementation of appropriate grazing systems like silvopastoral systems, and the conservation of water resources, at least in the higher parts of the watershed of Tambo Blanco. An economical sustainability could be achieved by the diversification of employment and income through the establishment of local trades and business, ecotourism and educational tourism, etc. Not least, the responsibility of the local people to protect the tropical mountain forest and their resources, including the development of environmental principles, the setting of limits concerning the use of natural resources and an implementation of environmental education, can contribute to the development of a social sustainability. Institutional sustainability can be achieved by resolving institutional conflicts, the utilization of the potential synergy of all organizations and the collaborations for sustainable development in Southern Ecuador as a common goal. For a successful and sustainable management within the Podocarpus - El Cóndor biosphere reserve, the integration of local knowledge and practical experience represent the main trigger, which form a basis for the sustainable use of natural resources in the tropical mountain forests.

Abstract:

We reconstructed the palaeoenvironmental conditions of the last ca. 8000 years in the Tres Lagunas region of the Quimsacocha volcanic basin (ca. 3800 m a.s.l.) in the southwestern Ecuadorian Andes. By means of a pollen and charcoal record, we analysed vegetation, fire, and climate history of this area, which is sensitive to climatic changes of both the Pacific as well as of the eastern Andes and Amazon region. Sediment deposits, pronounced increase of pollen and charcoal concentrations, and pollen taxa reflect warmer and drier conditions in the early to mid-Holocene (~8000 to 3900 cal B.P.). During the late Holocene (2250 to -57 cal B.P.), 5 warm and cold-phases occurred at Quimsacocha. The most prominent cold phase possibly corresponds to the globally recognized Little Ice-Age (LIA; ~600 to 100 cal B.P.). The cold phase signal at Quimsacocha was characterized by a higher abundance of Poaceae, Isoëtes and Gentianella, which favour cold and moist conditions. Frequent charcoal particles can be recorded since the early to mid-Holocene (~7600 B.P.). The high Andean tree species Polylepis underwent several phases of degradation and re-establishment in the basin, which can indicate the use of fire by pre-Columbian settlers to enhance the growth of preferred herb species. The Tres Lagunas record suggests that human populations have been influencing the environment around Quimsacocha since the last ca. 8,000 years.

Abstract:

The new structure of the planned research platform is visualized. For the first time scientists report about the income of small farms as well as about their plant and land use which were analyzed by thorough interviews. Members of the Research Unit show how the forest responds to elevated nitrogen deposition and display nitrogen, nitrous oxide and nitric oxide fluxes. They also explain climate-growth-relationships in trees, and describe the factors which are affecting the spatial distribution of trees. The data warehouse manager introduces how to filter and aggregate tabular values. Our partner NCI reports about a mayor breakthrough in the conservation of people and biodiversity in Perú. EDIT partners analyzed the distribution of ants and partners from the UTPL introduce a study that will be conducted to sample geo-information in South Ecuador.

Abstract:

The montane and premontane rainforests of southern Ecuador constitute a hotspot of biodiversity (cf. Brehm et al. 2008; Barthlott et al. 2007, Neill 2007). The use of plant resources from these forest areas is a fundamental part of the portfolio of livelihood activities of the local population. Increasing human activity however results in biodiversity loss. The extension of pastures and fields, logging, mining and the construction of roads represent the main threats to biodiversity in southern Ecuador. In order to develop conservation strategies it is of utmost importance to understand the plant and forest-use patterns of the inhabitants of this region. In this way, it will be possible to develop alternatives that consider local claims while conserving biodiversity (cf. Pohle et al. 2010). In this study ethnoecological and agrogeographical research methods have been used to make a qualitative analysis of the ethnospecific plant knowledge and plant use of the three main ethnic groups of southern Ecuador, namely the Shuar, the Saraguros and the Mestizos. This is followed by a discussion of the feasibility in the study sites of four so-called instruments for biodiversity conservation: agroforestry, ecotourism, payments for environmental services, and bioprospecting. The resulting ethnobotanical inventory includes 644 useful species and 16 main use categories. Edible and medicinal plants are the most important use categories. Ten percent of the identified species (64) has not been mentioned in the Encyclopaedia of the useful plants of Ecuador (de la Torre et al. 2008) so far. Herbs and trees represent the most common life forms used by all studied ethnic groups. The Shuar are traditional forest dwellers and have a comprehensive knowledge of plants: 316 different plant species with a total of 493 uses have been recorded. They are traditionally engaged in a number of livelihood activities that include fishing, hunting, and the gathering of wild plants. They get more than 40% of the plant species they use from the forests. In addition, they cultivate plant species which cannot be sufficiently (e.g. edible plants) or promptly (e.g. medicinal plants, ritual and mythical plants, fish poisons) extracted from the forest. The high number and variety of uses (ranging from edible fruits to shampoos and insecticides) reflect their wide plant knowledge. Similar to other Amazonian cultures, the traditional subsistence system of the Shuar is based on a combination of home gardens, slash and burn cultivation in forest gardens and the extraction of resources from the forest. In recent times the Shuar have entered the market economy through the small-scale production of cash crops, cattle ranching, and logging. At present population levels, the traditional home and forest gardens represent sustainable production systems and places of great agrobiodiversity (Pohle et al. 2010; Pohle & Gerique 2008; 2006). Increased production of cash crops could however result in habitat destruction. In addition, cattle ranching and logging have a negative impact. Pasture land competes with forest for land and requires the clearing of large tracts of forest. Due to the logging commercial timber, species such as Terminalia amazonia, Platymiscium pinnatum or Cedrelinga cateniformes have been over-exploited. The Shuar have apparently over-exploited game species as well, a factor that may have consequences in plant diversity: The zoochory or dispersion of seeds and other diaspores by wild animals could have been negatively affected. The possible over-use of certain non-timber forest products such as palm hearts remains unclear. Without being ?ecologically noble savages? (cf. Alvard 1993) the Shuar are effective partners for biodiversity conservation. Their land use system can be considered sustainable (Pohle et al. 2010; Pohle & Gerique 2008; 2006; Rudel et al. 2002). The inventory of the Saraguros of El Tibio and El Cristal comprises 230 plant species with a total of 310 uses; among the Mestizo of Los Guabos, Sabanilla, El Retorno, and La Fragancia 312 useful species with a total of 409 uses has been recorded. The ethnobotanical knowledge of the Saraguro and the Mestizo settlers is generally similar. They make little use of forest plant resources; less than 10% of the species used by the Saraguros and 5% of the species used by the Mestizos are forest plants, mostly timber species. The forest is considered a reserve for new pasture and maize production. In contrast to the Shuar, who mainly use wild species collected in the forest, the Saraguros and the Mestizos make an extended use of wild species that grow in disturbed sites and pastures. Most relevant are cultivated species, which represent half of the plants used by both ethnic groups. Cultivated plants are used in cattle ranching (e.g. fodder species, shade trees, living fences), and secure and diversify food supplies and plant remedies. Both groups make an extended use of cultivated ornamental plants. In recent times some families have introduced new ornamental species and sell them outside the communities. The ethnobotanical survey suggests that ongoing acculturation processes result in the loss of plant knowledge. Their integration into the market economy has probably replaced traditional self-made products with goods acquired in market places, which results in a loss of plant knowledge among younger generations (Reyes García et al. 2005; Benz et al. 2000; Putsche 2000). Most Saraguros and Mestizos have arrived in the area of study over the past six decades; the first settlers were poor landless farmers searching for land. The removal of trees for grazing and agricultural lands was a basic requirement to prove possession of land in order to get property titles from the Ecuadorian State (Barsky 1988). As a result, large areas of montane forest were cleared by burning. In this way, both ethnic groups have transformed most of the pristine vegetation of their communities into pastures. The construction of the road between Loja and Zamora during the 1960s attracted more settlers; they worked as day laborers or, if they had enough capital, bought existing fincas (Pohle & Gerique 2006). The road also allowed the exploitation of timber, mainly of the romerillo species (Podocarpus oleifolius and Prumnopitys montana). While the basic food supply is guaranteed by cultivation in fields and home gardens, cattle raising is market oriented. Today it represents the main land use system among Saraguros and Mestizos and fulfills multiple objectives: the production of beef and dairy products provides households with a regular income, it awards a prestigious social status, and represents a way of accumulating wealth. However, the forest is basically considered to be a reserve for new land for pastures and agriculture. The Saraguros and the Mestizos jeopardize in this way the sustainability of their economic systems; the forest, which is its own resource base, is being reduced. On the basis of these findings, the implementation of the above mentioned instruments for biodiversity conservation is discussed. In the case of the Shuar, ways must be found to conserve their traditional ecological knowledge during their inevitable transition to modernity and the market economy. It is necessary to foster additional sources of income that improve human well being and the conservation of biodiversity, and that make non-traditional, non-sustainable practices such as cattle ranching unnecessary. Without sustainable income alternatives, market forces and the demographic pressure would lead to an intensification of logging, large scale agriculture, and mining activities. Community-based ecotourism appears, in the short term, to be the most promising sustainable source of alternative income, followed by the implementation of agroforestry systems in the medium term. Other options such as payments for environmental services (e.g. REDD programs) and bioprospecting ventures appear less attractive, as they are hostage to political interests, bad image and unclear legislation. In the case of the Saraguros and Mestizos, the actual land use system based on cattle ranching turns out to be incompatible with the conservation of forest resources and long term household prosperity. Its significance in local economies should thus be reduced through diversification. An agroforestry system that includes reforestation, restoration and connection of forest patches, and sustainable selective logging could be implemented in the medium term (cf. Günter et al. 2009; Knoke et al. 2009a; 2009b; Stimm et al. 2008; Weber et al. 2008; Aguirre et al. 2006; Cabrera et al. 2006). In the short term, improved pasture management (including leguminous trees and living fences with useful species), and the small-scale production of niche products in home gardens could be alternatives to cattle ranching (Pohle et al. 2010). Market surveys should be conducted to determine the niche products, and economic safety nets that secure the introduction and viability of alternative sustainable land use activities need to be put in place. Payments for environmental services (e.g. payments for watershed protection or the Ecuadorian Socio Bosque Program) are an example of a way of generating the seed money for such projects. A network of long-distance trails could represent another way of generating alternative income in the region through ecotourism. Finally, to reduce the high scepticism towards conservation, improved environmental education and a readjustment of the borders of disputed protective forest areas must be considered. The realignment needs to take into consideration the demands of long-term inhabitants to gain credence among the local population.

Abstract:

In this study, the Mean Transit Time and Mixing Model Analysis methods are combined to unravel the runoff generation process of the San Francisco River basin (73.5 km2) situated on the Amazonian side of the Cordillera Real in the southernmost Andes of Ecuador. The montane basin is covered with cloud forest, sub-páramo, pasture and ferns. Nested sampling was applied for the collection of streamwater samples and discharge measurements in the main tributaries and outlet of the basin, and for the collection of soil and rock water samples. Weekly to biweekly water grab samples were taken at all stations in the period April 2007–November 2008. Hydrometric data, Mean Transit Time and Mixing Model Analysis allowed preliminary evaluation of the processes controlling the runoff in the San Francisco River basin. Results suggest that flow during dry conditions mainly consists of lateral flow through the C-horizon and cracks in the top weathered bedrock layer, and that all subcatchments have an important contribution of this deep water to runoff, no matter whether pristine or deforested. During normal to low precipitation intensities, when antecedent soil moisture conditions favour water infiltration, vertical flow paths to deeper soil horizons with subsequent lateral subsurface flow contribute most to streamflow. Under wet conditions in forested catchments, streamflow is controlled by near surface lateral flow through the organic horizon. Exceptionally, saturation excess overland flow occurs. By absence of the litter layer in pasture, streamflow under wet conditions originates from the A horizon, and overland flow. Copyright © 2011 John Wiley & Sons, Ltd.