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

Abstract:

Management of natural forestsmight be one option to reduce the high deforestation rate in Ecuador. We therefore evaluated the response of water and nutrient cycles in a natural tropical montane forest to improvement fellings with the aim of favoring economically valuable target trees which will later be harvested with additional ecosystem impacts not considered here. The study was conducted at ca. 1900?2200 m above sea level in the south Ecuadorian Andes on the east-exposed slope of the east cordillera. In June 2004, one of two paired ca. 10-ha large catchments was thinned by felling 10.2% of the initial basal area (dbh longer than 10 cm) on 30% of the catchment. The stems remained in situ. We measured ecosystem fluxes from rainfall via throughfall and stemflow to soil solution (litter leachate, soil solution at 15 and 30 cm depth) and stream flow between May 2004 and May 2005. After the fellings, soil solutions were extracted from the gaps created by the felled trees and the forest next to the gaps. We determined aboveground water fluxes by direct measurement and soil water fluxes with a budget approach. In the solutions, we measured concentrations of NH4-N, NO3-N, total dissolved N, PO4-P, total dissolved P, Ca, Mg, K, Na, and Cl-. Fluxes were calculated as volumeweighted mean (vwm) concentrations times water fluxes. Dry deposition was estimated using chloride as inert tracer. The fellings increased concentrations of N, K, Ca, and Mg in the organic layer of the resulting gaps compared with the forest next to the gaps (vwm concentrations of N: 6.4 mg/l in the forest next to the gap/8.7 mg/l in the gaps, K: 9.8/11, Mg: 1.8/3.0, Ca: 3.4/5.8). Lower nutrient concentrations and fluxes in the mineral soil of the gaps than in forest next to the gaps suggested that these nutrientswere taken up by ground vegetation and target trees. The paired modified and undisturbed catchments had similar water and nutrient budgets. The fellings did not have a significant impact on the water and nutrient budget at the catchment scale.

Abstract:

We tested the hypothesis that concentrations of chemical constituents in stream water can be explained by the depth of water flow through soil. Therefore, we measured the concentrations of total organic carbon (TOC), NO3-N, NH4-N, dissolved organic nitrogen (DON), P, S, K, Ca, Mg, Na, Al and Mn in rainfall, throughfall, stemflow, litter leachate, mineral soil solution and stream water of three 8-13 ha catchments on steep slopes (1900-2200 m above sea level) of the south Ecuadorian Andes, from April 1998 to April 2003. Peak C (14-22 mg litre
1), N (0.6-0.9 mg litre
1), K (0.5-0.7 mg litre
1), Ca (0.6-1.0 mg litre
1), Mg (0.3-0.5 mg litre
1), Al (110-390 mg litre
1) and Mn (3.9-8.4 mg litre
1) concentrations in stream water were associated with lateral flow (fast near-surface flow in saturated topsoil) while the greatest P (0.1-0.3 mg litre
1), S (0.3-0.7 mg litre
1) and Na (3.0-6.0 mg litre
1) concentrations occurred during low baseflow conditions. All elements had greater concentrations in the organic layer than in the mineral soil, but only C, N, K, Ca, Mg, Al and Mn were flushed out during lateral-flow conditions. Phosphorus, S and Na, in contrast, were mainly released by weathering and (re-)oxidation of sulphides in the subsoil. Baseflow accounted for 32% to 61% of P export, while > 50% of S was exported during intermediate flow conditions (i.e. lateral flow at the depth of several tens of cm in the mineral soil). Near-surface water flow through C- and nutrient-rich topsoil during rainstorms was the major export pathway for C, N, Al and Mn (contributing > 50% to the total export of these elements). Near-surface flow also accounted for one-third of total base metal export. Our results demonstrate that near-surface flow related to storm events markedly affects the cycling of many nutrients in steep tropical montane forests.

Abstract:

We explored the influence of biomass burning in Amazonia and northeastern Latin America on N, C, P, S, K, Ca, Mg, Al, Mn, and Zn cycles of an Andean montane forest in south Ecuador exposed to the Amazon basin between May 1998 and April 2003. We assessed the response of the element budget of three microcatchments (8?13 ha) to the variations in atmospheric deposition between the intensive burning season and outside the burning season in Amazonia. There were significantly elevated H, N, and Mn depositions during biomass burning. Elevated H deposition during biomass burning caused elevated base metal loss from the canopy and the organic horizon and deteriorated already low base metal supply of the vegetation. N was only retained during biomass burning but not during nonfire conditions when deposition was much smaller. We conclude that biomass burning-related aerosol emissions in Amazonia are large enough to substantially increase element deposition at the western rim of Amazonia. Particularly the related increase of acid deposition impoverishes already base metal scarce ecosystems. As biomass burning is most intense during El Nin?o situations, a shortened El Nin?o?Southern Oscillation cycle because of global warming likely enhances the acid deposition at our study forest.

Abstract:

We sampled the diversity of epiphytes (lichens, bryophytes, vascular plants) and moths (Geometridae, Arctiidae) in mature and recovering forest and in open vegetation in the montane belt in Ecuador. No uniform pattern of change in species richness was detected among the different taxonomic groups with increasing disturbance. Species richness of epiphytic bryophytes and vascular plants declined significantly from mature forest towards open vegetation. In contrast, species richness of epiphytic lichens did not change with increasing forest alteration, while that of geometrid moths was significantly higher in recovering forest compared with mature forest and open habitats. Arctiidae were significantly more species-rich in recovering forest and open vegetation than mature forest. Hence, for some organisms, modified habitats may play an important role for biodiversity conservation in the Andes, whereas others suffer from habitat disturbance. However, trends of changes in species composition following deforestation were surprisingly concordant across most studied epiphyte and moth taxa.

Abstract:

The rapid conversion of tropical forests poses the question as to the fate of the rich epiphyte communities of these forests. This paper presents results of our recent investigations on deforestation and epiphytes along disturbance gradients in mountain forest areas in Bolivia, Ecuador and Costa Rica. Species losses following disturbance vary considerably among the different groups of epiphytes and are particularly severe among orchids, bromeliads and filmy ferns. Moreover, shade epiphytes of the forest understory are more strongly impacted than sun epiphytes of the forest canopy. Species turnover along the disturbance gradient is high in all epiphyte groups and recovery of the epiphyte communities in the regenerating secondary forests is very slow. Canopy closure and microclimate are principal factors predicting epiphyte diversity changes along the disturbance gradient. In addition, changes in tree species composition and host tree characteristics play an important role. The lichen / bryophyte species ratio is a powerful indicator of the degree of human disturbance in tropical moist forests.

Abstract:

The impact of human disturbance on colonisation dynamics of vascular epiphytes is poorly known. We studied abundance, diversity and floristic composition of epiphyte seedling establishing on isolated and adjacent forest trees in a tropical montane landscape. All vascular epiphytes were removed from plots on the trunk bases of Piptocoma discolor. Newly established epiphyte seedlingswere recorded after 2 years, and their survival after another year. Seedling density, total richness at family and genus level, and the number of families and genera per plot were significantly reduced on isolated trees relative to forest trees. Seedling assemblages on trunks of forest trees were dominated by hygrophytic understorey ferns, those on isolated trees by xerotolerant canopy taxa. Colonisation probability on isolated trees was significantly higher for plots closer to forest but not for plots with greater canopy or bryophyte cover. Seedling mortality on isolated trees was significantly higher for mesophytic than for xerotolerant taxa. Our results show that altered recruitment can explain the long-term impoverishment of post-juvenile epiphyte assemblages on isolated remnant trees.We attribute these changes to a combination of dispersal constraints and the harshermicroclimate documented by measurements of temperature and humidity. Although isolated trees in anthropogenic landscapes are considered key structures for themaintenance of forest biodiversity inmany aspects, our results show that their value for the conservation of epiphytes can be limited.We suggest that abiotic seedling requirementswill increasingly constitute a bottleneck for the persistence of vascular epiphytes in the face of ongoing habitat alteration and atmospheric warming.

Abstract:

Question: Disturbance effects on dry forest epiphytes are poorly known. How are epiphytic assemblages affected by different degrees of human disturbance, and what are the driving forces? Location: An inter-Andean dry forest landscape at 2300 m elevation in northern Ecuador. Methods: We sampled epiphytic bryophytes and vascular plants on 100 trees of Acacia macracantha in five habitats: closed-canopy mixed and pure acacia forest (old secondary), forest edge, young semi-closed secondary woodland, and isolated trees in grassland. Results: Total species richness in forest edge habitats and on isolated trees was significantly lower than in closed forest types. Species density of vascular epiphytes (species per tree) did not differ significantly between habitat types. Species density of bryophytes, in contrast, was significantly lower in edge habitat and on isolated trees than in closed forest. Forest edge showed greater impoverishment than semi-closed woodland and similar floristic affinity to isolated trees and to closed forest types. Assemblages were significantly nested; habitat types with major disturbance held only subsets of the closed forest assemblages, indicating a gradual reduction in niche availability. Distance to forest had no effect on species density of epiphytes on isolated trees, but species density was closely correlated with crown closure, a measure of canopy integrity. Main conclusions: Microclimatic changes but not dispersal constraints were key determinants of epiphyte assemblages following disturbance. Epiphytic cryptogams are sensitive indicators of microclimate and human disturbance in montane dry forests. The substantial impoverishment of edge habitat underlines the need for fragmentation studies on epiphytes elsewhere in the Tropics.

Abstract:

Multidisciplinary research projects bear a great potential for the exploration and understanding of complex interrelations e. g. between ecosystem and atmospheric processes. On the other hand, cooperating scientist often face the problem of finding effective yet time inexpensive ways of data and knowledge transfer between the individual working groups in order to maximize synergetic effects and consequently to succeed in research. Based on the experience within different multidisciplinary research projects, the authors introduce two different concepts for central data services and discuss the related advantages and disadvantages using the DFG research unit 402 and 816 as an exemplarily case. In general, it can be established that the required degree of interaction between the working group is a good indicator for choosing between the different central data service concepts.

Abstract:

To date, the annual and diurnal pattern of low clouds touching the ground in tropical mountains is widely unknown. This holds true for the valley of the Rio San Francisco in southern Ecuador, and is mainly due to a lack of routine cloud observations, which is symptomatic for remote areas in tropical high mountains. A method to use a simple and cost-effective WebCam system for a quantitative analysis of cloud frequency as a proxy for the occurrence of low-cloud bases touching the ground is introduced. An interactive classification tool is developed, which is applied to a comprehensive dataset of 32 452 images (during the years 2002?2004) archived at 5 min intervals. The results point to a rapid increase of cloud frequency at altitudes >2600 m asl both during the day and the year, mainly caused by advective clouds veiling the crests of the Cordillera del Consuelo. Even if the formation of radiation fog directly at the valley bottom is nearly negligible with regard to the whole dataset, scatterometer measurements suggest that valley fog formation on the slopes is a regular process during the night, causing a clear drop in the cloud base around sunrise. The interaction of low-radiative and high-advective clouds is supposed to be the driving factor for a rainfall maximum at the valley bottom around sunrise. Higher values of cloud frequency still exist at the crest level around noon: these originate from well-developed upslope-breeze systems.

Abstract:

The water budget of forested catchments controls the local water supply and influences the regional climate. To assess anthropogenic impact on the water cycle we constructed a water budget for three ~10 ha catchments under lower montane forest on the east-facing slope of the Andes in south Ecuador at 1900-2150 m elevation. We used field hydrological measurements and modeled surface flows with TOPMODEL, a semi-distributed catchment model. We measured incident precipitation, throughfall, stemflow, and surface flow between May 1998 and April 2002 in hourly to weekly resolution, and determined all variables needed to parameterize TOPMODEL. On average of the four monitored years and three catchments, incident precipitation was 2504±s.d.123 mm, throughfall 1473±197 mm, and stemflow 25±2 mm yr-1. Fog water input was negligible. Mean annual interception loss in the forest was 1006±270 mm, and mean annual surface flow, calculated with TOPMODEL in an hourly resolution was 1039±48 mm. The resulting mean annual evapotranspiration was 1466±161 mm of which 32% (=471±162 mm) was transpiration if evaporation from the soil was neglected. Our study catchments show a high evapotranspiration attributable to the strong solar insolation near the equator, the small impact of fog, the generally low intensity of incident precipitation and additional wind-driven advective energy input.

Abstract:

SIR ? Your Editorial ?Markets can save forests? proposes integrating deforestation into the international carbon market (Nature 452, 127?128; 2008), but it is unlikely that money alone can solve the problem. The process of tropical deforestation presents a dilemma: enormous economic value more than US$ 2,000 a year per hectare is lost in favour of small private benefits (often less than US$ 100 a year per hectare). In a true market, an increased, scarcity-signalling price should provide an incentive to boost the supply of the scarce commodity. So far, this has not worked in the case of tropical forests. Real financial flows received for the provision of ecosystem services are vanishingly small, if they exist at all ? only a few beneficiaries have been convinced to pay for environmental services. This illustrates the essentially theoretical character (at least, up till now) of economic values generated by ecosystem services. Payments for ecosystem services (PES) are supposed to save tropical forests. But even if it were possible to mobilize substantial PES, tropical farmers wouldn?t be prepared to stand by and twiddle their thumbs while receiving these payments to protect the forest. They need a field of activity, so sustainable land-use concepts should address the social environment and needs of people as well. These concepts could be linked and possibly financed by PES. If the people who use tropical lands are disregarded, we don?t believe that PES will solve the problem of disappearing tropical forests. What is needed is an economic system that keeps people gainfully employed in an activity that is ultimately productive, not destructive.

Abstract:

In forests, complex canopy processes control the change in volume and chemical composition of rain water. We hypothesize that (i) spatial patterns, (ii) the temporal stability of spatial patterns, and (iii) the temporal course of solute concentrations can be used to explore these processes. The study area at 1950 m above sea level in the south Ecuadorian Andes is far away from anthropogenic emission sources and marine influences. It received ca. 2200 mm of rain annually. We collected rain and throughfall on an event and within-event basis for five precipitation periods between August and October 2005 at up to 25 sites and analyzed the samples for pH and concentrations of , , , , , , , , and total N ( ), P ( ), and organic C ( ). Cumulative throughfall amounted to 79% of rainfall. Compared with other tropical forests, rainfall solute concentrations were low and throughfall solute concentrations similar. Volumes and solute concentrations of rainfall were spatially and temporally little variable. The spatial coefficient of variation for throughfall volumes was 53%, for solute concentrations 28–292%, and for deposition 33–252%. Temporal persistence of spatial patterns was high for throughfall volumes and varied among solutes. Spatial patterns of , and concentrations in throughfall were highly persistent. The spatial patterns of throughfall fluxes were less stable than those of concentrations. During a monitoring time of 72 hours, solute concentrations in throughfall of selected rain events remained at a similar level indicating that the leachable element pool in the canopy was not exhausted. Our results demonstrate that the passage of rain through the canopy of a tropical montane forest in Ecuador results in a spatially heterogeneous throughfall pattern with a considerable stability during three months. There is a large leachable element pool in the canopy, which is not depleted by the typical light rain within 72 hours.

Abstract:

In tropical montane forests, soil properties change with altitude and tree growth decreases. In a tropical montane forest in Ecuador, we determined soil and tree properties along an altitudinal transect between 1960 and 2450 m above seal level. In different vegetation units height, basal area, and diameter growth of trees were recorded, and all horizons of three replicate profiles at each of eight sites were sampled. We determined pH and total concentrations of Al, C, Ca, K, Mg, Mn, N, Na, P, S, Zn, polyphenols, and lignin in all soil horizons and in the mineral soil additionally the effective cation-exchange capacity (ECEC). The soils were Cambisols, Planosols, and Histosols. The concentrations of Mg, Mn, N, P, and S in the O horizons and of Al, C, and all nutrients except Ca in the A horizons correlated significantly negatively with altitude. The C/N, C/P, and C/S ratios increased and the lignin concentrations decreased in O and A horizons with increasing altitude. Forest stature, tree basal area, and tree growth decreased with altitude. An ANOVA analysis indicated that macronutrients (e.g., N, P, Ca) and micronutrients (e.g., Mn) in the organic layer and in the soil mineral A horizon were correlated with tree growth. Furthermore, lignin concentrations in the organic layer and the C/N ratio in soil affected tree growth. These effects were consistent, even if the effect of altitude was accounted for in a statistical hierarchical model. This suggests a contribution of nutrient deficiencies to reduced tree growth possibly caused by reduced organic matter turnover at higher altitudes.

Abstract:

[1] We quantified base metal deposition to Amazonian montane rainforest in Ecuador between May 1998 and April 2003 and assessed the response of the base metal budget of three forested microcatchments (8-13 ha). There was a strong interannual variation in deposition of Ca [4.4-29 kg ha-1 yr-1], Mg [1.6-12], and K [9.8-30]). High deposition changed the Ca and Mg budgets of the catchments from loss to retention, suggesting that the additionally available Ca and Mg was used by the ecosystem. Increased base metal deposition was related to dust outbursts of the Sahara and an Amazonian precipitation pattern with trans-regional dry spells allowing for dust transport to the Andes. The increased base metal deposition coincided with a strong La Niña event in 1999/2000.

Abstract:

In order to study the stability and dynamics of mountain rainforest and paramo ecosystems, including the biodiversity of these ecosystems, the Holocene and late Pleistocene climate and fire variability, and human impact in the southeastern Ecuadorian Andes, we present a high-resolution pollen record from El Tiro Pass (2810m elevation), Podocarpus National Park. Palaeoenvironmental changes, investigated by pollen, spores and charcoal analysis, inferred from a 127cm long core spanning the last ca. 21 000 cal. yr BP, indicate that grass-paramo was the main vegetation type at the El Tiro Pass during the late Pleistocene period. The grass-paramo was rich in Poaceae, Plantago rigida and Plantago australis, reflecting cold and moist climatic conditions. During the early Holocene, from 11200 to 8900 cal. yr BP, subparamo and upper mountain rainforest vegetation expanded slightly, indicating a slow warming of climatic conditions during this period. From 8900 to 3300 cal. yr BP an upper mountain rainforest developed at the study site, indicated by an increase in Hedyosmum, Podocarpaceae, Myrsine and Ilex. This suggests a warmer climate than the present day at this elevation. The modern subparamo vegetation became established since 3300 cal.yr BP at El Tiro Pass. Fires, probably anthropogenic origin, were very rare during the late Pleistocene but became frequent after 8000 cal. yr BP.

Abstract:

Two data sets representing atmospheric moisture are available for the high Andes of Ecuador, (i) cloud frequency obtained from weather satellites, and (ii) interpolated rainfall estimates obtained from global climate observations. We analyzed their correlation to vascular plant species composition at 18 Ecuadorian superpa´ ramo study sites. Of particular interest was whether cloud frequency could be used as a proxy for precipitation. Cloud frequency had distinct seasonal and spatial variation among the sites. The spatial gradient of cloudiness was strongest during June–August and weakest around the equinoctials. Interpolated rainfall estimates also showed seasonal and spatial variation among the sites, but there was no correlation between them and cloudiness. Cloud frequency during June–August was the only significant variable in the canonical correspondence analysis (CCA) of the species composition, whereas rainfall estimates, geology, presence of glaciers, and size and altitudinal range of the superpa´ ramos were not significant. When the spatial components were filtered out from the species composition data by employing partial CCA, cloud frequency during December–February became the only significant variable. Our results suggest that cloud frequency data may be a useful tool in mountain ecology research, serving as an indicator of habitat humidity when exact precipitation data are lacking.