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

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Linking nutrient balances and flows to soil nutrient stocks creates a valuable indicator for sustainability assessment in agricultural land-use systems. Therefore, we investigated the impact of management on soil fertility at farm/field scale using the Nutmon approach. A detailed methodology for the adaptation of the difficult-to-quantify flows to the local conditions is described. Research was carried out in the three farming systems of Yantzaza (low-external-input), El Tambo (irrigated cash crops) and San Lucas (integrated nutrient management) in southern Ecuador. For each land-use within a farm (annual and perennial crops, pasture, forest), soil nutrient balances and flows were modeled with Nutmon and soil nutrient stocks were calculated for NPK. Soil nutrient balances were evaluated using potential socio-economic and soil fertility explanatory variables. Balances for the different land-uses in the three research areas varied between -151 to 66 kg ha-1 a-1 for N, -4 to 33 kg ha-1 a-1 for P and -346 to 39 kg ha-1 a-1 for K and were mainly negative. Up to 70 % of the balances’ variability was explained by soil fertility variables and financial flows. Highest external inputs existed in land-uses with a strong market orientation. Land-uses benefiting from a surplus of within-farm flows had the highest soil nutrient stocks. The focus on N fertilization induced highly negative PKbalances in annual crops of El Tambo. In contrast, the application of organic fertilizers and nutrient recycling in San Lucas resulted in positive NP balances particularly for perennial crops. NP balances in annual crops of Yantzaza were most negative due to nonexistent fertilization, leaching and burning of crop residues. A non-sustainable landuse of annual crops in Yantzaza was illustrated by total N stock decreases of 4.9 % a-1 and decreased soil organic carbon stocks to 85 % of adjacent forest sites. Results indicated a potential risk regarding sustainable management of soils in the research area and provide a basis for policy and decision makers to develop appropriate management strategies.

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1. Ridges of tropical mountains often differ strikingly from neighbouring ravines in terms of forest structure, productivity and species composition. This heterogeneity is poorly understood despite its critical role in biodiversity maintenance, carbon and nutrient budgets. 2. We examined measures of tree biomass and productivity, foliage and litter quality (nutrient concentrations, specific leaf mass, phenolics), herbivory and leaf litter decomposition in each six plots laid out in upper and lower slope position in a tropical montane moist forest in southeastern Ecuador. 3. Productivity, quality of foliage and litter as well as herbivory were significantly lower in upper slope position, and closely correlated with soil nutrient concentrations and accumulated humus. The decomposition of upper slope leaf litter (decomposition rate k) was substantially lower than in litter from lower slope forest, whereas the site of decomposition (slope position) only had a marginal effect on the decomposition rate. 4. Our results suggest that the differences in stand structure, productivity, foliar quality, herbivory and decomposition between slope positions are ultimately due to stronger nutrient limitations in upper slope forest. We propose a general conceptual model that explains origin and maintenance of contrasting forest types along topographical gradients through down-slope fluxes of nutrients and water, and a nutrient-driven positive feedback cycle.

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Atmospheric sulfur deposition above certain limits can represent a threat to tropical forests, causing nutrient imbalances and mobilizing toxic elements that impact biodiversity and forest productivity. Atmospheric sources of sulfur deposited by precipitation have been roughly identified in only a few lowland tropical forests. Even scarcer are studies of this type in tropical mountain forests, many of them megadiversity hotspots and especially vulnerable to acidic deposition. In these places, the topographic complexity and related streamflow conditions affect the origin, type, and intensity of deposition. Furthermore, in regions with a variety of natural and anthropogenic sulfur sources, like active volcanoes and biomass burning, no source emission data has been used for determining the contribution of each source to the deposition. The main goal of the current study is to evaluate sulfate (SO? 4 ) deposition by rain and occult precipitation at two topographic locations in a tropical mountain forest of southern Ecuador, and to trace back the deposition to possible emission sources applying back-trajectory modeling. To link upwind natural (volcanic) and anthropogenic (urban/industrial and biomass-burning) sulfur emissions and observed sulfate deposition, we employed state-of-the-art inventory and satellite data, including volcanic passive degassing as well. We conclude that biomass-burning sources generally dominate sulfate deposition at the evaluated sites. Minor sulfate transport occurs during the shifting of the predominant winds to the north and west. Occult precipitation sulfate deposition and likely rain sulfate deposition are mainly linked to biomass-burning emissions from the Amazon lowlands. Volcanic and anthropogenic emissions from the north and west contribute to occult precipitation sulfate deposition at the mountain crest Cerro del Consuelo meteorological Station and to rain-deposited sulfate at the upriver mountain pass El Tiro meteorological station.

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This paper describes a method of low-altitude remote sensing in combination with in situ measurements (leaf area, spectroscopy, and position) to monitor the postfire canopy recovery of two competing grassland species. The method was developed in the Andes of Ecuador, where a tethered balloon with a digital camera was deployed to record a time series of very high spatial resolution imagery ( nominal resolution = 2cm ) of an experimental plot covered by two competing species: 1) the pasture grass, Setaria sphacelata; and 2) the invasive southern bracken, Pteridium arachnoideum. Image processing techniques were combined to solve geometric issues and construct high-quality mosaics for image classification. The semiautomatic and object-oriented classification method was based on geometrical and textural attributes of image segments and showed promising results for detecting the invasive bracken fern in Setaria pastures (performance by area under the curve, AUC = 0.88). Valuable insights are given into vegetation monitoring applications using unmanned aerial vehicles, which produces a time series of species-specific maps, including foliage projective cover (FPC) and leaf area index (LAI). This new method constitutes an important and accessible tool for ecological investigations of competing species in pastures and validation of remote sensing information on mountain environments.

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Questions: To assess the relationship between modern pollen rain and Andean montane forest vegetation for diversity, and provide a basis for interpretations of palaeoecological data in the northern Andes, we asked: (1) can the reduction of plant and pollen data to family level preserve information about diversity in both data sets; (2) how precisely do tree pollen and spore types represent richness patterns along an altitudinal gradient on tropical mountains; and (3) how similar are tree pollen and spore family richness in relationship to tree family richness? Location: Tropicalmontane rain forests, Podocarpus National Park in the Andes of South Ecuador (3°S, 79°W, 1000–3000 ma.s.l.). Methods:We analysed tree diversity and species composition in three different rain forest types: Premontane (PMF), lowermontane (LMF) and uppermontane (UMF).We investigated modern pollen rain using pollen traps. After testing the reliability of a taxonomic surrogacy on the plant data, we compared abundance and representation, as well as diversity of the two data sets at family level. This was done using rarefaction and Sørensen indices. Results: The correlation between tree species and families was high (r = 0.81, P < 0.001). Sample rarefaction on tree pollen and plant family data revealed highest pollen diversity on sites of the UMF, but highest tree diversity on LMF and PMF sites. The Sørensen indices indicate down-drift of pollen from higher altitudes in PMF and LMF and up-drift in UMF. Between 1% and 50% of pollen taxa of each sample originate fromoutside the plot. Conclusions: Taxonomic surrogacy at family level is a good tool for comparing presence–absence patterns of plant and pollen data in tropical regions with high tree diversity. On a family basis, pollen presence–absence data represent the corresponding tree vegetation data, but uncertainties increase with decreasing altitude. The higher diversity in pollen data of the UMF, but slightly lower diversity in the LMF and PMF, can at least partly be explained by wind patterns, local abundance of shrubs and herbs and differences in evenness.

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Aims: In acid tropical forest soils (pH <5.5)increased mobility of aluminum might limit aboveground productivity. Therefore, we evaluated Al phytotoxicity of three native tree species of tropical montane forests in southern Ecuador. Methods: An hydroponic dose-response experiment was conducted. Seedlings of Cedrela odorata L., Heliocarpus americanus L., and Tabebuia chrysantha(Jacq.) G. Nicholson were treated with 0, 300, 600, 1200, and 2400 ?M Al and an organic layer leachate. Dose-response curves were generated for root and shoot morphologic properties to determine effective concentrations (EC). Results: Shoot biomass and healthy leaf area decreased by 44 % to 83 % at 2400 ?M Al, root biomass did not respond (C. odorata), declined by 51 % (H. americanus), or was stimulated at low Al concentrations of 300 ?M (T. chrysantha). EC10 (i.e. reduction 10 %) values of Al for total biomass were 315 ?M (C. odorata), 219 ?M (H. americanus), and 368 ?M (T. chrysantha). Helicarpus americanus, a fast growing pioneer tree species, was most sensitive to Al toxicity. Negative effects were strongest if plants grew in organic layer leachate, indicating limitation of plant growth by nutrient scarcity rather than Al toxicity. Conclusions: Al toxicity occurred at Al concentrations far above those in native organic layer leachate.

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Lowered temperatures may reduce the root water uptake of tropical trees at high elevations through several mechanisms; however, field studies to test their relevance are lacking. We measured sap flux density (J) in small-diameter tree roots across a 2000-m elevation transect in a tropical mountain forest for quantifying the effects of temperature, VPD and soil moisture on root water flow and uptake at different elevations. Recently developed miniature heat balance-sap flow gauges were applied to roots of about 10mm in diameter in mountain forest stands at 1050, 1890 and 3060m a.s.l. in the Ecuadorian Andes and the measured flow was related to anatomical properties of the root xylem. Between 1050 and 3060 m, mean J decreased to about a third. VPD was the most influential environmental factor controlling J at 1050 and 1890 m, while Ta was the key determinant at 3060 m. Large vessels were absent in the root xylem of high-elevation trees which resulted in a 10-fold decrease of theoretical hydraulic conductivity (kh theor) between 1050 and 3060 m. We conclude that both physical limitations (reduced VPD, increased viscosity of water) and biological constraints (large decrease of kh theor) result in a significantly reduced J and root water uptake of the trees in high-elevation tropical forests.

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It is generally assumed that tree growth in tropical low-elevation forests is primarily limited by phosphorus while nitrogen limitation is more prominent in tropical montane forests where temperature is lower and the soils are poorly developed. We tested this hypothesis in mountain rainforests of South Ecuador by investigating the growth response of tree fine roots to N, P and K fertilization in ingrowth cores exposed at 1050 m (pre-montane) and 3060 m (upper montane) elevation. Root growth into unfertilized ingrowth cores (control treatment) was about 10 times slower at 3060 m than at 1050 m. At 1050 m, root growth was stimulated not only by P, but also by N and K. In contrast, N was the only element to promote root growth at 3060 m. The N concentration in fine root biomass dropped to nearly a third between 1050 and 3060 m, those of P, K, Ca and Mg decreased as well, but to a lesser degree. According to a 15NO3 15NH4 tracer study along the slope, tree fine roots accumulated nitrate and ammonium in root biomass at similar rates between 1050 and 3060 m, despite lower temperatures higher upslope.We conclude that the nature of nutrient limitation of tree fine root growth changes with elevation from an apparent co-limitation by P together with N and K at 1050 m to predominant N limitation at 3060 m, which is also reflected by low foliar N concentrations. Increasing N limitation may have caused the high fine root biomass and root/shoot ratio in the high elevation forest, while the capability of the roots to acquire mineral N apparently was not affected by lower temperatures at high elevations.

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Rural households in agricultural economies are vulnerable to several environmental risks such as fires, floods, and droughts that may affect their productivity in whole or in part. These hazards are especially relevant in developing countries where farmers have few or no access to traditional risk-transfer techniques, such as insurance and finance, and where low governmental investments in rural infrastructure, risk assessment techniques, or early warning systems makes the aftermath of such hazards more expensive and results in slower recovery for those who are affected. In this paper, we use historical satellite data (Terra) of burned areas in South America to fit a semiparametric spatial model, based on kernel smoothing and on a nonlinear relationship between average time between events and damage, to assess the environmental hazard affecting the land’s productivity. The results were twofold: first, we were able to develop a spatial assessment of fire hazard, and second, we were able to evaluate how much a farmer may lose in terms of productivity per hectare due to the environmental hazard. The methodology may be easily adapted to other world regions; to different environmental hazards such as floods, windbreak, windthrow, or related land-use changes; or to integrate various environmental hazards simultaneously, as long as they can be monitored via remote sensing (e.g., satellite imagery, aerial photographs, etc).

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The precise estimation of precipitation quantities in tropical mountain regions is in great demand by ecological and hydrological studies, due to the heterogeneity of the rainfall distribution and the lack of meteorological station data. This study uses radar images and ground station data to provide the required high-resolution precipitation maps. Also wind data are taken into account, due to its influence on the precipitation formation and to demonstrate the relation between synoptic wind, topography and the precipitation distribution inside small mountain valleys. The study analyses the rainfall distribution and amounts of 4 days inside the San Francisco Valley, a small catchment in the tropical Andes of southern Ecuador, representing different seasons and the typical atmospheric flows, which are correlated to the annual precipitation map. The results show that the rainfall distribution and amounts are generally defined by the wind direction and velocity, besides the topographic location in relation to the main barriers and pathways. The dominant wind direction causes a division of the catchment in a wetter eastern and a dryer western part. Moreover, the annual seasons are reversed; the main rainy season for the eastern part occurs between June and August, while the western part reaches the precipitation maximum between January and March. This may have influence on the species composition at the different slopes and the annual hydrological cycle inside the catchment.

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Increased nitrogen (N) depositions expected in the future endanger the diversity and stability of ecosystems primarily limited by N, but also often co-limited by other nutrients like phosphorus (P). In this context a nutrient manipulation experiment (NUMEX) was set up in a tropical montane rainforest in southern Ecuador, an area identified as biodiversity hotspot. We examined impacts of elevated N and P availability on arbuscular mycorrhizal fungi (AMF), a group of obligate biotrophic plant symbionts with an important role in soil nutrient cycles. We tested the hypothesis that increased nutrient availability will reduce AMF abundance, reduce species richness and shift the AMF community toward lineages previously shown to be favored by fertilized conditions. NUMEX was designed as a full factorial randomized block design. Soil cores were taken after 2 years of nutrient additions in plots located at 2000 m above sea level. Roots were extracted and intraradical AMF abundance determined microscopically; the AMF community was analyzed by 454-pyrosequencing targeting the large subunit rDNA. We identified 74 operational taxonomic units (OTUs) with a large proportion of Diversisporales. N additions provoked a significant decrease in intraradical abundance, whereas AMF richness was reduced significantly by N and P additions, with the strongest effect in the combined treatment (39% fewer OTUs), mainly influencing rare species. We identified a differential effect on phylogenetic groups, with Diversisporales richness mainly reduced by N additions in contrast to Glomerales highly significantly affected solely by P. Regarding AMF community structure, we observed a compositional shift when analyzing presence/absence data following P additions. In conclusion, N and P additions in this ecosystem affect AMF abundance, but especially AMF species richness; these changes might influence plant community composition and productivity and by that various ecosystem processes.

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A digital soil mapping approach is applied to a complex, mountainous terrain in the Ecuadorian Andes. Relief features are derived from a digital elevation model and used as predictors for topsoil texture classes sand, silt, and clay. The performance of three statistical learning methods is compared: linear regression, random forest, and stochastic gradient boosting of regression trees. In linear regression, a stepwise backward variable selection procedure is applied and overfitting is controlled by minimizing Mallow’s Cp. For random forest and boosting, the effect of predictor selection and tuning procedures is assessed. 100-fold repetitions of a 5-fold cross-validation of the selected modelling procedures are employed for validation, uncertainty assessment, and method comparison. Absolute assessment of model performance is achieved by comparing the prediction error of the selected method and the mean. Boosting performs best, providing predictions that are reliably better than the mean. The median reduction of the root mean square error is around 5%. Elevation is the most important predictor. All models clearly distinguish ridges and slopes. The predicted texture patterns are interpreted as result of catena sequences (eluviation of fine particles on slope shoulders) and landslides (mixing up mineral soil horizons on slopes).

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Systematic investigations of the upper forest line (UFL) primarily concentrate on mid and high latitudes of the Northern Hemisphere, whereas studies of Neotropical UFLs are still fragmentary. This article outlines the extraordinary high tree diversity at the UFL within the Andean Depression and unravels the links between the comparatively low position of the local UFL, high tree-species diversity, and climate. On the basis of Gentry?s rapid inventory methodology for the tropics, vegetation sampling was conducted at 12 UFL sites, and local climate (temperature, wind, precipitation, and soil moisture) was investigated at six sites. Monotypic forests dominated by Polylepis were only found at the higher located margins of the Andean Depression while the lower situated core areas were characterized by a species-rich forest, which lacked the elsewhere dominant tree-species Polylepis. In total, a remarkably high tree-species number of 255 tree species of 40 different plant families was found. Beta-diversity was also high with more than two complete species turnovers. A non-linear relationship between the floristic similarity of the investigated study sites and elevation was detected. Temperatures at the investigated study sites clearly exceeded 5.5°C, the postulated threshold value for the upper tree growth limit in the tropics. Instead, quasi-permanent trade winds, high precipitation amounts, and high soil water contents affect the local position of the UFL in a negative way. Interestingly, most of the above-mentioned factors are also contributing to the high species richness. The result is a combination of a clearly marked upper forest line depression combined with an extraordinary forest line complexity, which was an almost unknown paradox.

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Weekly samples from surface waters, springs, soil water and rainfall were collected in a 76.9 km² mountain rain forest catchment and its tributaries in southern Ecuador.Time series of the stable water isotopes (oxygen-18 and deuterium) were used to calculate mean transit times (MTTs) and the transit time distribution functions (TTDs) solving the convolution method for seven lumped-parameter models. For each model setup, the generalized likelihood uncertainty estimation (GLUE) methodology was applied to find the best predictions, behavioral solutions and parameter identifiability. For the study basin, TTDs based on model types such as the linear–piston flow for soil waters and the exponential–piston flow for surface waters and springs performed better than more versatile equations such as the gamma and the two parallel linear reservoirs. Notwithstanding both approaches yielded a better goodness of fit for most sites, but with considerable larger uncertainty shown by GLUE. Among the tested models, corresponding results were obtained for soil waters with short MTTs (ranging from 2 to 9 weeks). For waters with longer MTTs differences were found, suggesting that for those cases the MTT should be based at least on an intercomparison of several models. Under dominant baseflow conditions long MTTs for stream water ? 2 yr were detected, a phenomenon also observed for shallow springs. Short MTTs for water in the top soil layer indicate a rapid exchange of surface waters with deeper soil horizons. Differences in travel times between soils suggest that there is evidence of a land use effect on flow generation.

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Quantification of nutrient stocks and their temporal changes are considered of prime importance in farm-ing systems of the humid tropics to answer the question of sustainable management. The research areain the Southern Ecuadorian Andes included forest, annual (0–5 years old) and different aged perennial(0–5, 6–10, 11–20, 21–30) and pasture (0–5, 6–10, 11–20, 21–30, >30) sites. Soil organic carbon (SOC),total and plant available soil nutrient stocks and nutrient balances were investigated to assess temporalsoil nutrient dynamics in relation to management activities. Forest conversion by slash-and-burn caused a decrease in SOC stocks in all three land-uses amounting between 14% and 19%. This was mainly due tothe absence of an organic layer and losses in the upper five cm of the mineral soil. Stocks of exchangeablebases and pH values increased in annuals which however, had the most negative nutrient balance of allland-uses amounting to ?128, ?25 and ?226 kg ha?1 a?1 for N, P and K, respectively. The abandonmentof annual sites after five years was linked to a shortage of available N and P due to low-external-input management which caused SOC stock decreases. Major soil nutrient changes in perennials and pasturesdid not occur directly but 6–20 years after forest conversion with increases in stocks for total N, P, S and exchangeable bases above forest level. SOC stocks of medium aged perennials and pastures increased above forest level in the mineral soil. Easily available inorganic N and P stocks remained low throughout the chronosequence in perennials and pastures, indicating a quick uptake by plant roots and microor-ganisms. Compared to medium aged sites, oldest perennials and pastures showed a strong decrease in SOC (?28% and ?16%) and soil nutrient stocks. Stocks for total N, P, S and exchangeable bases were up to50% below those of medium aged sites in oldest perennials and pastures.

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A tropical smallholder cash crop farming system in a semi-arid Inter-Andean valley of Ecuador was investigated. Intensive irrigated agriculture with up to 400 kg of urea-N fertilization ha?1·a?1 prevails in colluvial sites whereas urea application in the steep eroded sites is lower. Farmers did recently introduce manure to partly replace urea fertilization. Knowledge about the effects of mineral and organic fertilizers on nitrogen and carbon cycling needs to be improved to maintain sustainable agriculture in the research area. Therefore, a laboratory incubation experiment was conducted to investigate effects of urea and guinea pig manure on microbial activity of colluvial foot slope and eroded upper slope soils. Soil samples were treated with 200 kg·N·ha?1 either applied as urea, guinea pig manure or a combination of both and compared to a control. Urea fertilizer was labeled with 15N to trace its fate. Microbial biomass and basal respiration were determined in different time intervals. Urea fertilization induced an acceleration of soil organic matter (SOM) mineralization (positive priming effect) in the first seven days of incubation. The combined fertilization served as a positive alternative to the present urea management since it increased the amount of microbial biomass and provided mineral nitrogen for immediate plant uptake. Moreover, low recovery rates suggested an immobilization of fertilized nitrogen into the microbial biomass inducing an efficient and sustained nutrient release throughout the entire growing season. SOM stocks in colluvial soils were 40% below those of eroded soils which was partly due to the positive priming effect after urea fertilization. Microbial activity and efficiency were not reduced by soil erosion.

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The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara dust inputs particularly increasing Ca deposition. We added CaCl2 to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 × 5 kg ha–1 Ca annually as CaCl2) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al concentrations and speciation in soil solutions. After 1 y of Ca addition, we assessed fine-root biomass, leaf area, and tree growth. Only < 3% of the applied Ca leached below the acid organic layer (pH 3.5–4.8). The added CaCl2 did not change electrical conductivity in the root zone after 2 y. In the second year of fertilization, Ca retention in the canopy of the Ca treatment tended to decrease relative to the control. After 2 y, 21% of the applied Ca was recycled to soil with throughfall and litterfall. One year after the first Ca addition, fine-root biomass had decreased significantly. Decreasing fine-root biomass might be attributed to a direct or an indirect beneficial effect of Ca on the soil decomposer community. Because of almost complete association of Al with dissolved organic matter and high free Ca2+ : Al3+ activity ratios in solution of all plots, Al toxicity was unlikely. We conclude that the added Ca was retained in the system and had beneficial effects on some plants.

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Water-bound nitrogen (N) cycling in temperate terrestrial ecosystems of the Northern Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to the environment. In little-industrialized and remote areas, in contrast, a larger part of N cycling occurs as dissolved organic N (DON). In a north Andean tropical montane forest in Ecuador, the N cycle changed markedly during 1998–2010 along with increasing N deposition and reduced soil moisture. The DON concentrations and the fractional contribution of DON to total N significantly decreased in rainfall, throughfall, and soil solutions. This inorganic turn of the N cycle was most pronounced in rainfall and became weaker along the flow path of water through the system until it disappeared in stream water. Decreasing organic contributions to N cycling were caused not only by increasing inorganic N input but also by reduced DON production and/or enhanced DON decomposition. Accelerated DON decomposition might be attributable to less waterlogging and higher nutrient availability. Significantly increasing NO3-N concentrations and NO3-N/NH4-N concentration ratios in throughfall and litter leachate below the thick organic layers indicated increasing nitrification. In mineral soil solutions, in contrast, NH4-N concentrations increased and NO3-N/NH4-N concentration ratios decreased significantly, suggesting increasing net ammonification. Our results demonstrate that the remote tropical montane forests on the rim of the Amazon basin experienced a pronounced change of the N cycle in only one decade. This change likely parallels a similar change which followed industrialization in the temperate zone of the Northern Hemisphere more than a century ago.

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The sloping mire landscape of the investigation area, in the southern Andes of Ecuador, is dominated by stagnic soils with thick organic layers. The recursive partitioning algorithm Random Forest was used to predict the spatial water stagnation pattern and the thickness of the organic layer from terrain attributes. Terrain smoothing from 10 to 30m raster resolution was applied in order to obtain the best possible model. For the same purpose, several model tuning parameters were tested and a prepredictor selection with the R-package Boruta was applied. Model versions were evaluated and compared by 100 repetitions of the calculation of the residual mean square error of a five-fold cross-validation. Position specific density functions of the predicted soil parameters were then used to display prediction uncertainty. Prepredictor selection and tuning of the Random Forest algorithm in some cases resulted in an improved model performance.We therefore recommend testing prepredictor selection and tuning to make sure that the best possible model is chosen.This needs particular emphasis in complex tropical mountain soil-landscapes which provide a real challenge to any soil mapping approach but where Random Forest has proven to be successful due to the testing of model tuning and prepredictor selection.

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Species diversity of geometrid moths (Lepidoptera, Geometridae) has previously been shown to be extremely and constantly high along a continuously forested elevational gradient in the Andes of southern Ecuador. We analysed samples taken from 32 sites between 1999 and 2011 in northern Podocarpus National Park and adjacent areas from 1020 to 2916 m a.s.l. We conjecture that high elevation habitats were historically mostly colonised by species from lower elevations, and that environmental filtering (e.g. through host plant specificity or temperature tolerance) constrained colonisation from lower elevations, which would yield a pattern of elevationally decreasing phylogenetic diversity. We analysed elevational phylogenetic patterns by means of: 1) the nearest-taxon index (NTI), 2) DNA barcode-based terminal branch lengths (TBLs) from maximum-likelihood phylogeny, 3) the subfamily composition of the local assemblages, and 4), the rarefied number of morphologically defined genera per site. We counted a total of 1445 species. NTI values significantly increased with elevation, both in a conventional and a rarefaction approach. TBLs decreased significantly with elevation. Subfamily composition profoundly changed with elevation, particularly expressed as an increased proportion of the subfamily Larentiinae and decreased fractions of Sterrhinae and Geometrinae. The number of genera in equally rarefied species resamples significantly decreased with elevation. We conclude that environmental filtering indeed contributed to an altitudinal decrease in moth phylodiversity, but these constraints prevented only relatively few clades from colonising high elevation habitats.

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Approaches to reconciling food production with climatic and environmental protection often require agricultural intensification. The production of more food per unit of agricultural land through "sustainable intensification" is intended to enable the protection of natural ecosystems elsewhere (land sparing). However, there are problems associated with agricultural intensification; such as soil erosion, eutrophication or pollution of water bodies with chemicals, landscape homogenization and loss of biodiversity; for which solutions have not yet been found. Reuse of abandoned agricultural lands – which are abundant throughout the world – to address the rising demand for food is a potentially important alternative, which up to now has been widely ignored. To test the power of this alternative, equilibrium economic land allocation to various land-use practices by risk-avoiding tropical farmers in Ecuador was simulated. The reestablishment of pastures on abandoned cattle lands lowered prices for pasture products, and also triggered conversion of existing pasture into cropland. The resulting land-use change increased total annual food production in a moderate scenario from the current level of 17.8–23.1 petacalories (10^15 calories), which amounted to a production increase of 30%. At the same time, there was a 19% reduction in the amount of payments to farmers required to preserve tropical forests – one of the world’s greatest terrestrial carbon stores.

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Future increase of atmospheric nitrogen deposition in tropical regions is expected to have negative impacts on forests ecosystems and related biogeochemical processes. In tropical mountain forests topography causes complex streamflow and rainfall patterns, governing the atmospheric transport of pollutants and the intensity and spatial variability of deposition. The main goal of the current study is to link spatio-temporal patterns of upwind nitrogen emissions and nitrate deposition in the San Francisco Valley (eastern Andes of southern Ecuador) at different altitudinal levels. The work is based on Scanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) retrieved-NO2 concentrations, NOx biomass burning emissions from the Global Fire Emissions Database (GFEDv3), and regional vehicle emissions inventory (SA-INV) for urban emissions in South America. The emission data is used as input for lagrangian atmospheric backward trajectory modeling (FLEXTRA) to model the transport to the study area. The results show that NO3 À concentrations in occult precipitation samples are significantly correlated to long-range atmospheric secondary nitrogen transport at the highest meteorological stations (MSs) only, whereas for NO3 À concentrations in rain samples this correlation is more pronounced at the lower MSs. We conclude that ion concentrations in occult precipitation at the uppermost MSs are mainly linked to distant emission sources via the synoptic circulation impinging the more exposed higher sites. Lower correlations close to the valley bottom are due to a lower occult precipitation frequency and point to a contamination of the samples by local pollution sources not captured by the used emission data sources.

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In the anthropogenic fire-disturbed ecosystem of the San Francisco Valley in the Andes of southeastern Ecuador, dense stands of an aggressive invasive weed, the southern bracken fern (Pteridium arachnoideum and Pteridium caudatum), dominate the landscape. To secure sustainable land management in the region, a comprehensive understanding of bracken spatial-distribution patterns and life cycle dynamics is crucial. We investigated the possibility of detecting bracken-infested areas and frond status (live, fungi-infected, and dead) by means of a high-resolution QuickBird scene from October 2010 and spectral signatures based on field spectroscopy. After image pre-processing, a two-step classification procedure first delineates the bracken-infested area by means of a maximum-likelihood hard classification. The probability-guided unmixing classifier with field-derived end-members is applied in the second step to obtain the fractional cover of the different frond statuses per pixel. The results showed that the areas infested by bracken could be distinguished from the other land-cover classes with high accuracy (overall accuracy of 0.9973). Also, the three frond statuses could be accurately classified at the sub-pixel level. The ‘dead’ class was the dominant frond status at the time of image acquisition (October 2010). We conclude that the extreme dry spell in October 2010 was particularly responsible for this dominance.

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Previous research from the tropics indicates that AMF may be well adapted to organic soils and even represent the dominant mycorrhizal form, though the extraradical part of the symbiosis was omitted as in most other tropical studies. Our study aims at characterizing the extraradical part of arbuscular mycorrhizal fungi (AMF) in a highly organic tropical montane forest soil in Southern Ecuador. Based on recent studies on the interaction of AM fungal hyphae and litter we hypothesized that within the organic layer AM hyphae grow in close contact with decomposing material. To test this idea, AM fungal hyphal distribution in the organic layer was determined by directly staining roots and decomposing leaves and extracting hyphae from the remaining particulate organic material. AM and non-AM fungal hyphae were analyzed, as well as root colonization patterns. Our results showed that AMF indeed represented the dominant mycorrhizal form with an average root colonization of 43%. The extraradical AM hyphal length ranged from 2 to 34 m g?1 soil with a mean of 10.4 m g?1 soil (equals 3.1 m cm?3 soil), and therefore exceeded root length about 13-fold. As hypothesized, 29% of AM extraradical hyphae were closely attached to decomposing leaves. These hyphae were mainly located at the leaf surface, though in some parts leaf veins and inner leaf tissues were colonized. More than half of AM hyphal biomass was detected on the root surface, a pattern potentially driven by the predominant Paris-type AMF. Non-AM fungal hyphae colonized decomposing material to a significantly greater extent, though hyphal length attached to roots was equal. This study supports the adaptation of AMF to highly organic soils in the tropics and the existence of a widespread extraradical mycelium, which is not readily detectable by standard methods. The close association with decomposing leaves most likely improves direct nutrient uptake from decomposed material and points to a potential indirect contribution of AMF to the decomposition process.

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Arbuscular mycorrhizae are important for growth and survival of tropical trees. We studied the community of arbuscular mycorrhizal fungi in a tropical mountain rain forest and in neighbouring reforestation plots in the area of Reserva Biológica San Francisco (South Ecuador). The arbuscular mycorrhizal fungi were analysed with molecular methods sequencing part of the 18S rDNA. The sequences were classified as Operational Taxonomic Units (OTUs). We found high fungal species richness with OTUs belonging to Glomerales, Diversisporales and Archaeosporales. Despite intensive sampling, the rarefaction curves are still unsaturated for the pristine forest and the reforestation plots. The communities consisted of few frequent and many rare species. No specific interactions are recognizable. The plant individuals are associated with one to ten arbuscular mycorrhizal fungi and mostly with one to four. The fungal compositions associated with single plant individuals show a great variability and variety within one plant species. Planted and naturally occurring plants show high similarities in their fungal communities. Pristine forest and reforestation plots showed similar richness, similar diversity and a significantly nested structure of plant-AMF community. The results indicate that small-scale fragmentation presently found in this area has not destroyed the natural AMF community, at least yet. Thus, the regeneration potential of natural forest vegetation at the tested sites is not inhibited by a lack of appropriate mycobionts.

Resumen:

Species diversity of geometrid moths (Lepidoptera, Geometridae) has previously been shown to be extremely and constantly high along a continuously forested elevational gradient in the Andes of southern Ecuador. We analysed samples taken from 32 sites between 1999 and 2011 in northern Podocarpus National Park and adjacent areas from 1020 to 2916 m a.s.l. We conjecture that high elevation habitats were historically mostly colonised by species from lower elevations, and that environmental filtering (e.g. through host plant specificity or temperature tolerance) constrained colonisation from lower elevations, which would yield a pattern of elevationally decreasing phylogenetic diversity. We analysed elevational phylogenetic patterns by means of: 1) the nearest-taxon index (NTI), 2) DNA barcode-based terminal branch lengths (TBLs) from maximum-likelihood phylogeny, 3) the subfamily composition of the local assemblages, and 4), the rarefied number of morphologically defined genera per site. We counted a total of 1445 species. NTI values significantly increased with elevation, both in a conventional and a rarefaction approach. TBLs decreased significantly with elevation. Subfamily composition profoundly changed with elevation, particularly expressed as an increased proportion of the subfamily Larentiinae and decreased fractions of Sterrhinae and Geometrinae. The number of genera in equally rarefied species resamples significantly decreased with elevation. We conclude that environmental filtering indeed contributed to an altitudinal decrease in moth phylodiversity, but these constraints prevented only relatively few clades from colonising high elevation habitats.