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

Abstract:

Theory predicts positive effects of species richness on the productivity of plant communities through complementary resource use and facilitative interactions between species. Results from manipulative experiments with tropical tree species indicate a positive diversity–productivity relationship (DPR), but the existing evidence from natural forests is scarce and contradictory. We studied forest aboveground productivity in more than 80 humid tropical montane oldgrowth forests in two highly diverse Andean regions with large geological and topographic heterogeneity and related productivity to tree diversity and climatic, edaphic and stand structural factors with a likely influence on productivity. Main determinants of wood production in the perhumid study regions were elevation (as a proxy for temperature), soil nutrient (N, P and base cation) availability and forest structural parameters (wood specific gravity, aboveground biomass). Tree diversity had only a small positive influence on productivity, even though tree species numbers varied largely (6–27 species per 0.04 ha). We conclude that the productivity of highly diverse Neotropical montane forests is primarily controlled by thermal and edaphic factors and stand structural properties, while tree diversity is of minor importance.

Abstract:

A new satellite-based algorithm for rainfall retrieval in high spatio-temporal resolution fo Ecuador is presented. The algorithm relies on the precipitation information from the Integrated Multi-SatEllite Retrieval for the Global Precipitation Measurement (GPM) (IMERG) and infrared (IR) data from the Geostationary Operational Environmental Satellite-16 (GOES-16). It wa developed to (i) classify the rainfall area (ii) assign the rainfall rate. In each step, we selected the most important predictors and hyperparameter tuning parameters monthly. Between 19 April 2017 and 30 November 2017, brightness temperature derived from the GOES-16 IR channels and ancillary geo-information were trained with microwave-only IMERG-V06 using random forest (RF). Validation was done against independent microwave-only IMERG-V06 information not used for training. The validation results showed the new rainfall retrieva technique (multispectral) outperforms the IR-only IMERG rainfall product. This offers using the multispectral IR data can improve the retrieval performance compared to single-spectrum IR approaches. The standard verification scored a median Heidke skill score of ~0.6 for the rain area delineation and R between ~0.5 and ~0.62 for the rainfall rate assignment, indicating uncertainties for Andes’s high elevation. Comparison of RF rainfall rates in 2 km2 resolution with daily rain gauge measurements reveals the correlation of R = ~0.33.

Abstract:

Background: Since the 1990’s, afforestation programs in the páramo have been implemented to offset carbon emissions through carbon sequestration, mainly using pine plantations. However, several studies have indicated that after the establishment of pine plantations in grasslands, there is an alteration of carbon pools including a decrease of the soil organic carbon (SOC) pool. The aim of this study is to investigate the impact of the establishment of pine plantations on the carbon stocks in different altitudes of the páramo ecosystem of South Ecuador. Results: At seven locations within an elevational gradient from 2780 to 3760 m a.s.l., we measured and compared carbon stocks of three types of land use: natural grassland, grazed páramo, and Pinus patula Schlltdl. & Cham. plantation sites. For a more accurate estimation of pine tree carbon, we developed our own allometric equations. There were significant (p < 0.05) differences between the amounts of carbon stored in the carbon pools aboveground and belowground for the three types of land use. In most of the locations, pine plantations revealed the highest amounts of aboveground and belowground carbon (55.4 and 6.9 tC/ha) followed by natural grassland (23.1 and 2.7 tC/ha) and grazed páramo sites (9.1 and 1.5 tC/ha). Concerning the SOC pools, most of the locations revealed significant lower values of plantations’ SOC in comparison to natural grassland and grazed páramo sites. Higher elevation was associated with lower amounts of pines’ biomass. Conclusions: Even though plantations store high amounts of carbon, natural páramo grassland can also store substantial amounts above and belowground, without negatively affecting the soils and putting other páramo ecosystem services at risk. Consequently, plans for afforestation in the páramo should be assessed case by case, considering not only the limiting factor of elevation, but also the site quality especially affected by the type of previous land use.

Abstract:

Morphological traits provide the interface between species and their environment. For example, body size affects the fitness of individuals in various ways. Yet especially for ectotherms, the applicability of general rules of interspecific clines of body size and even more so of other morphological traits is still under debate. Here we tested relationships between elevation (as a proxy for temperature) and productivity with four ecologically relevant morphological traits of orthopteran assemblages that are related to fecundity (body size), dispersal (wing length), jumping ability (hind femur length), and predator detection (eye size). We measured traits of 160 orthopteran species that were sampled along an extensive environmental gradient at Mt. Kilimanjaro (Tanzania), spanning elevations from 790 to 4,410 m above sea level (a.s.l.) with different levels of plant productivity. For traits other than body size, we calculated the residuals from a regression on body length to estimate the variation of traits irrespective of body size. Bayesian analyses revealed that mean body size of assemblages, as well as the means of relative wing length, hind femur length, and eye size, decreased with increasing elevation. Body size and relative eye size also decreased with increasing productivity. Both phylogenetic relationships, as well as species‐specific adaptations, contributed to these patterns. Our results suggest that orthopteran assemblages had higher fecundity and better dispersal and escape abilities, as well as better predator detection at higher temperatures (low elevations) than at low temperatures (high elevations). Large body sizes might be advantageous in habitats with low productivity because of a reduced risk of starvation. Likewise, large eye size might be advantageous because of the ability to detect predators in habitats with low vegetation cover, where hiding possibilities are scarce. Our study highlights that changes in temperature and productivity not only lead to interspecific changes in body size but are also related to independent changes of other morphological traits that influence the ecological fit of organisms in their environment.

Abstract:

Habitat loss and landscape fragmentation are important drivers of changes in biodiversity. In fragmented landscapes, bird species are able to use multiple forest patches that may therefore share an important portion of the regional biodiversity. In turn, these patches are linked through their shared bird diversity (i.e. species-habitat networks). Identifying the importance of nodes (e.g. forest patches) in species-habitat networks is increasingly important to improve conservation planning. Within this network approach, the relative importance of patches for birds can be identified via centrality indices-measures of the magnitude of shared bird diversity of patches across the entire network (i.e. patch centrality). Here, we tested for changes in patch centrality within bird species-patch networks of two habitat guilds, forest specialists and generalists, in relation to patch area, patch shape irregularity and within-patch habitat characteristics across 15 Polylepis woodland patches in a páramo landscape of southern Ecuador. Patch centrality for forest specialists decreased with greater influence of surrounding páramo plants, i.e. an increasing proportion of bunch-grasses and small shrubs, in the within-patch habitat and was unaffected by either patch area or patch shape irregularity. On the other hand, patch centrality for generalists was positively influenced by patch shape irregularity but was unaffected by patch area or the influence of surrounding páramo plants in the within-patch habitat. Patch centrality reveals that the relative importance of Polylepis woodlands lies in their habitat quality. Forest specialists are dependent on mature Polylepis woodland patches, while generalists benefit from the natural irregular shape of the woodlands. Finally, a species-habitat network approach facilitates the recognition of important Polylepis patches and their characteristics for conservation of the Andean bird community at a landscape scale.

Abstract:

The Random Forest (RF) algorithm, a decision-tree-based technique, has become a promising approach for applications addressing runoff forecasting in remote areas. This machine learning approach can overcome the limitations of scarce spatio-temporal data and physical parameters needed for process-based hydrological models. However, the influence of RF hyperparameters is still uncertain and needs to be explored. Therefore, the aim of this study is to analyze the sensitivity of RF runoff forecasting models of varying lead time to the hyperparameters of the algorithm. For this, models were trained by using (a) default and (b) extensive hyperparameter combinations through a grid-search approach that allow reaching the optimal set. Model performances were assessed based on the R2, %Bias, and RMSE metrics. We found that: (i) The most influencing hyperparameter is the number of trees in the forest, however the combination of the depth of the tree and the number of features hyperparameters produced the highest variability-instability on the models. (ii) Hyperparameter optimization significantly improved model performance for higher lead times (12- and 24-h). For instance, the performance of the 12-h forecasting model under default RF hyperparameters improved to R2 = 0.41 after optimization (gain of 0.17). However, for short lead times (4-h) there was no significant model improvement (0.69 &lt; R2 &lt; 0.70). (iii) There is a range of values for each hyperparameter in which the performance of the model is not significantly affected but remains close to the optimal. Thus, a compromise between hyperparameter interactions (i.e., their values) can produce similar high model performances. Model improvements after optimization can be explained from a hydrological point of view, the generalization ability for lead times larger than the concentration time of the catchment tend to rely more on hyperparameterization than in what they can learn from the input data. This insight can help in the development of operational early warning systems.

Abstract:

Tropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projec- tions how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing between response traits that determine the resistance of species to environmental changes and efect traits that are relevant for species’ interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research framework that uses a trait-based response-efect-framework (REF) to quantify relationships between abiotic conditions, the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity- LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.

Abstract:

Tropical Mountain Forest (TMF) provides important ecological functions like evapotranspiration (ET) that supplies moisture and energy to the atmosphere. ET observations are scarce and difficult to accomplish particularly in areas of high heterogeneity where TMF are. Remote sensing (RS) allows to quantify and to determine ET spatial variation at the landscape level. Detail imaginary improves high spatial variability retrieval. Thought the greater detail introduces cast shadows by trees which hamper image interpretation. The objective of this study is to characterize ET estimation for the TMF of the southern Ecuadorian Andes by combining meteorological data with high-resolution satellite images. Shadows from high resolution images were masked out by applying focal statistics. The analysis included two meteorological periods typical of the area; a wet period when rain prevails and a dry period when precipitation is more sporadic. The reference evapotranspiration (ET0) was calculated using the FAO-Penman Montheid method by applying data obtained from an automatic weather station. The enhanced vegetation index (EVI) was derived from 2 m resolution WorldView2 satellite images. Results showed a lower ET mean value during the wet period: 1.54 mm day−1 compared to 2.37 mm day−1. Two forest types, differentiated from its structural composition and topographical position (ravine and ridge), marked ET spatial variation. Ravine forest that has a more dense and closed canopy showed higher ET values for both meteorological conditions. A comparison between ET estimations and ET field measurements from a scintillometer device showed a good agreement (coefficient of correlation r = 0.89) that proves the validity of the method. This study demonstrates that the application of high spatial resolution improves ET estimation in TMF especially when shadows are removed. Also, emphasizes the importance of analysing spatial heterogeneity to properly assess ecosystem water flux terms.

Abstract:

Forest plantations with exotic species in southern Ecuador have mostly been characterized as having negative externalities in both ecological and economic terms. After ten years of research in mountain forests in southern Ecuador on restoration and reforestation, several native tree species with good growth responses (e.g. Handroanthus chrysanthus, Cedrela montana and Juglans neotropica) have been identified in open field conditions. Some species (e.g. Podocarpus oleifolius and P. sprucei) were able to grow under the shelter provided by Pinus and Alnus trees.

Abstract:

Ratios of stable oxygen isotopes in tree rings (δ18O) are a valuable proxy for reconstructing past climates. Such reconstructions allow us to gain better knowledge of climate dynamics under different (eg warmer) environmental conditions, which also forms the basis for effective risk management. The latter aspect is particularly relevant for our study site on the western flanks of the Andes in Southern Ecuador, since the region is frequently affected by droughts and heavy precipitation events during the rainy season (January to April), leading to enormous social and economic losses. In particular, we focus on precipitation amounts and moisture source regions as they are known to influence the δ18O signature of tree rings. Moisture source regions are based on 240 h backward trajectories that were calculated with the trajectory model LAGRANTO for the rainy seasons 2008 to 2017. A moisture source diagnostic was applied to the air parcel pathways. The resulting moisture source regions were analyzed by calculating composites based on precipitation amounts, season, and calendar year. The precipitation amounts were derived from data of a local Automatic Weather Station (AWS). The analysis confirms that our study site receives its moisture both, from the Atlantic and the Pacific Oceans. Heavy precipitation events are linked to higher moisture contributions from the Pacific, and local SST anomalies along the coast of Ecuador are of higher importance than those off the coast toward the central Pacific. Moreover, we identified increasing moisture contributions from the Pacific over the course of the rainy season. This change and also rain amount effects are detectable in preliminary data of δ18O variations in tree rings of Bursera graveolens. These signatures can be a starting point for investigating atmospheric and hydroclimatic processes, which trigger δ18O variations in tree rings, more extensively in future studies.

Abstract:

(1) We investigated the variation in tree fine root traits and their functional diversity along a local topographic gradient in a Neotropical montane forest to test if fine root trait variation along the gradient is consistent with the predictions of the root economics spectrum on a shift from acquisitive to conservative traits with decreasing resource supply. (2) We measured five fine root functional traits in 179 randomly selected tree individuals of 100 species and analyzed the variation of single traits (using Bayesian phylogenetic multi‐level models) and of functional trait diversity with small scale topography. (3) Fine roots exhibited more conservative traits (thicker diameters, lower specific root length and nitrogen concentration) at upper slope compared to lower slope positions, but the largest proportion of variation (40‐80%) was explained by species identity and phylogeny. Fine root functional diversity decreased towards the upper slopes. (4) Our results suggest that local topography and the related soil fertility and moisture gradients cause considerable small‐scale variation in fine root traits and functional diversity along tropical mountain slopes, with conservative root traits and greater trait convergence being associated with less favorable soil conditions due to environmental filtering. We provide evidence of a high degree of phylogenetic conservation in fine root traits.

Abstract:

The response of organic carbon (C) concentrations in ecosystem solutions to environmental change affects the release of dissolved organic matter (DOM) from forests to surface and groundwaters. We determined the total organic C (TOC) concentrations (filtered <1–7 μm) and the ratios of TOC/dissolved organic nitrogen (DON) concentrations, electrical conductivity (EC), and pH in all major ecosystem solutions of a tropical montane forest from 1998 to 2013. The forest was located on the rim of the Amazon basin in Ecuador and experienced increasing numbers of days with >25°C, decreasing soil moisture, and rising nitrogen (N) deposition from the atmosphere during the study period. In rainfall, throughfall, mineral soil solutions (at the 0.15- and 0.30-m depths), and streamflow, TOC concentrations and fluxes decreased significantly from 1998 to 2013, while they increased in stemflow. TOC/DON ratios decreased significantly in rainfall, throughfall, soil solution at the 0.15-m depth, and streamflow. Based on Δ14C values, the TOC in rainfall and mineral soil solutions was 1 year old and that of litter leachate was 10 years old. The pH in litter leachate decreased with time, that in mineral soil solutions increased, while those in the other ecosystem solutions did not change. Thus, reduced TOC solubility because of lower pH values cannot explain the negative trends in TOC concentrations in most ecosystem solutions. The increasing TOC concentrations and EC in stemflow pointed at an increased leaching of TOC and other ions from the bark. Our results suggest an accelerated degradation of DOM, particularly of young DOM, associated with the production of N-rich compounds simultaneously to changing climatic conditions and increasing N availability. Thus, environmental change increased the CO2 release to the atmosphere but reduced DOM export to surface and groundwater.

Abstract:

Litterfall is the most easily and most frequently measured part of net primary productivity (NPP) of forests. It has been shown that litterfall accounts for about one third of total NPP and thus serves as a proxy for the total productivity of forests. Moreover, litterfall carries nutrients from the forest canopy to the soil and therefore is also a major vector of nutrient cycling. I reviewed the published literature about litterfall rates and chemical properties in Andean forests and found reports from 44 forest sites, which I evaluated together with unpublished data from 12 sites in a lower montane forest in Ecuador. I found many more reports from tropical (52 sites) than from temperate Andean forests (4 sites). In the humid tropical north Andes, litterfall showed a hump-shaped elevational distribution. It increased from premontane to lower montane forests and decreased to upper montane forests. The tropical lower montane forest had a similar productivity than tropical lowland forests. The litterfall of the temperate southern beech forests was similar to that of the tropical upper montane forests. The C/N and C/P ratios of litterfall decreased with increasing elevation, while the N/P ratios were not correlated with elevation. This illustrates that the forests become increasingly nutrient efficient with increasing elevation, while there is no indication of a general change in the kind of nutrient limitation. There was a negative correlation between litterfall and soil organic layer thickness (r = −0.61, p < 0.001) illustrating that the organic matter input via litterfall is a less important driver of organic matter accumulation on top of the mineral soil than other, mainly abiotic properties including temperature and soil waterlogging. My evaluation suggests that there are systematic relationships between abiotic conditions and litterfall, which could be used to predict litterfall in the Andes. However, the data coverage particularly of the southern Andes (Bolivia, Chile, Argentina), the Andean dry forests, and the widespread tree plantations is poor. The observed elevational influence on litterfall in the humid tropical Andes suggests that the forest productivity will likely respond to climate change driving the vegetation belts to higher elevation with an unknown overall effect on C sequestration of these forests.

Abstract:

Interest in atmosphere-surface flux modeling over the mountainous regions of the globe has increased recently, with a major focus on the prediction of water, carbon and other functional indicators in natural and disturbed conditions. However, less research has been centered on exploring energy fluxes (net radiation; sensible, latent and soil heat) and actual evapotranspiration (ETa) over the Neotropical Andean biome of the páramo. The present study assesses the implementation and parameterization of a state-of-art Land-Surface Model (LSM) for simulation of these fluxes over two representative páramo catchments of southern Ecuador. We evaluated the outputs of the LSM Community Land Model (CLM ver. 4.0) with (i) ground-level flux observations from the first (and highest) Eddy Covariance (EC) tower of the Northern Andean páramos; (ii) spatial ETa estimates from the energy balance-based model METRIC (based on Landsat imagery); and (iii) derived ETa from the closure of the water balance (WB). CLM’s energy predictions revealed a significant underestimation on net radiation, which impacts the sensible and soil heat fluxes (underestimation), and delivers a slight overestimation on latent heat flux. Modeled CLM ETa showed acceptable goodness-of-fit (Pearson R = 0.82) comparable to ETa from METRIC (R = 0.83). Contrarily, a poor performance of ETa WB was observed (R = 0.46). These findings provide solid evidence on the CLM’s accuracy for the ETa modeling, and give insights in the selection of other ETa methods. The study contributes to a better understanding of ecosystem functioning in terms of water loss through evaporative processes, and might help in the development of future LSMs’ implementations focused on climate / land use change scenarios for the páramo.

Abstract:

Environmental studies regularly use the net present value (NPV) to value benefits and costs of projects. However, the NPV disregards whether the stream of net benefits is steady or volatile and ignores the distribution of net benefits among different groups of people. Here we test alternatives to NPV, building on two example cases: 1) We use discounted utility (DU) to evaluate land-use projects and calculate opportunity costs for avoided deforesta-tion. 2) We simulate decision-making on tropical deforestation, whereby we use multiple decision criteria to consider the distribution of net benefits between two groups: farmers and conservationists. Results show considerable differences in the ranking of projects between DU and NPV, when projects are not marginal. Compared to DU, NPV regularly overestimates the value of forest plantations. Moreover, NPV tends to overstate the opportunity costs of avoiding deforestation in terms of saved carbon emissions. Not accounting for the distribution of net benefits in optimizing land-use allocation leads to suboptimal simulated deforestation scenarios. We therefore suggest that future studies should either also use DU to value economic consequences of projects or that they use the NPV as only one among several socio-economic and ecological decision criteria.

Abstract:

Diversified agricultural landscapes have been shown to provide a wide range of ecosystem services. It is often stated that the main motivation behind growing multiple crops within a farm is to buffer farm income against market and climate risks. However, household characteristics, particularly the amount of off-farm income may also influence farm diversity. While the drivers of diversifying farm income have been investigated extensively,the ecologically important level of land-use diversity on a farm has seldom been used as a dependent variable. Based on data from 163 households, this paper analyzes the impact of social, economic and demographic household characteristics on crop diversification for farms located around the Laipuna Reserve in the dry forests of southern Ecuador. Using a Heckman two-step regression model, we identified factors that influence a) the probability that a farm will be diversified (PD) and b) the degree of diversification at the farm level (LUD), quantified by the Shannon index. We found that PD is positively related to the percentage of household members who depend on family income but do not work (economic dependence ratio), as well as river access and available family labor force. PD is inversely related to access to financial support (i.e. social payments and credits) and off-farm income. LUD is positively related to the number of household members and the age of the head of the household, and correlates negatively with labor force, financial support and off-farm income. Our results demonstrate that land-use diversification is not only a strategy to reduce risk, but it is also driven by farmers’ efforts to meet household, mainly subsistence, needs. Moreover, we also demonstrate that when households have access to financial support and off-farm income, the pressure to diversify their crops diminishes. Finally, we argue that forest and agricultural policies should impose instruments to support land-use diversification financially, while acknowledging the importance of financial support and off-farm income for household economies. Strategies to reduce poverty should be accompanied by direct support of land-use diversification, infrastructure development and agricultural training.

Abstract:

In tropical regions insect herbivores are considered one of the key players in the ecosystem function by effecting the nutrient cycle as well as the carbon sequestration of these systems. However, their feeding is strongly influenced by abiotic factors, like temperature, leading to a lower performance and abundance of herbivores under lower temperature, as well as biotic factors, like plant defence mechanisms (e.g. tougher leaves or a higher concentration of secondary metabolites). But plants are facing a constant trade-off between growth and defence, which is stronger under harsher environmental conditions. The resulting differences in defence further lead to a big variability in the rate of herbivory between the plants. Although several studies investigated the interaction between herbivory, biotic and abiotic factors, most of them concentrate on single species and systems. However, since herbivory varies between species and has high impacts on the whole ecosystem by influencing plants viability and the carbon sequestration, it is crucial to investigate the interaction on community level. We therefore assessed herbivory across an elevational gradient of 1000 m to 3000 m a.s.l. on a community level, i.e. by measuring 313 representative tree species. To determine the biotic interaction we measured leaf traits using both conventional and remote sensing methods, to look for the applicability of remote sensing for extrapolation of community patterns. Our study shows, that herbivory decreased with increasing elevation. Furthermore, sulphur showed a positive association with herbivory and SLA, nitrogen and tannin showed a negative association. The influence of carotenoid on herbivory changed from a positive to a negative one with elevation and anthocyanin showed the opposite pattern. Phylogeny thereby had the same effect on both conventional and remote sensing measured leaf traits. Our results showed, that the influence of the abiotic factors especially at higher elevations were strong, leading to the conclusion, that community level herbivory is more effected by the abiotic interaction along the elevational gradient than the biotic interaction. Moreover, the models of conventionally and remote sensing determined leaf traits had a strong congruence regarding the influence of abiotic and biotic factors on herbivory, although they comprise different leaf traits. Consequently we can state, that remote sensing can be used to predict herbivory on a community level in a tropical mountain forest.

Abstract:

The new issue of the Tabebuia Bulletin of the RESPECT Research Unit presents the new biodiversity land surface model Hydroatmo Unified Model of BiOtic interactions and Local Trait Diversity (HUMBOL-TD) and how it integrates hydrologic, biodiversity-related and atmospheric parameters. The bulletin summarises the research results of the individual projects that could be achieved despite the COVID-19 pandemic which overshadowed the entire work. Researchers report about responses and feedback effects of climate and land-use changes on abiotic drivers, biodiversity and ecological processes in this hotspot area. In details this Bulletin covers: • Hyperspectral data products that can be used to parameterize and test the LSMAtmo model • Partitioning net ecosystem exchange into gross primary productivity and ecosystem respiration • Simulating response and effect mechanisms of global change on hydrological processes • Response of nutrient supply to climate and land-use changes • Implementing biotic interactions into a process-based dynamic vegetation model • Functional traits: Effects of phylogeny and elevation and the relation to tree growth • Plant functional types that can be differentiated by their response to transitory drought events • Radial variability of wood functional traits in the pioneer tree Heliocarpus americanus • Evapotranspiration as an essential variable bridging climatology, soil science and plant ecophysiology • Reproductive traits of fleshy-fruited plants • How plant traits and arthropod communities influence herbivory Beyond, the bulletin reports on establishment and repair of field infrastructure, recent advances of the data warehouse and the reconstruction of climate time series. Finally, research projects from Ecuadorian counterparts and milestones reached by the infrastructure providers round off the issue.

Abstract:

Tropical dry forests (TDFs) are often degraded and fragmented through human impact, which is also the case in Southern Ecuador, where land-use pressure is high. In this context we studied tree species composition and forest structure in a protected and adjacent disturbed TDF at altitudes between 560-1080 m asl. Fabaceae and Malvaceae were identified as the most important tree families in both forest types. The disturbed forest displayed lower tree species richness than the protected forest, and the gap in species richness between the two forest types increased with increasing altitude. Ten species of the protected forest were not recorded in the disturbed forest, two of them endemic. The disturbed site was further characterized by a lower number of stems but with larger diameters, in comparison with the protected forest. The majority of the most abundant tree species in the disturbed forest had rather low wood densities, but also the combination of high wood density with browsing tolerance and high resprouting capacity was encountered, and seems to be advantageous for getting established in such sites. Although certain tree species were well represented in the disturbed forest, some endemic species with relatively low abundances (e.g. Simira ecuadorensis, Prockia crucis) should receive more conservation attention.

Abstract:

Many forests restoration programs and efforts depend on seeds. Particularly in the Andes, further information regarding seed germination requirements and seed storage behavior is necessary. The aim of this study was to evaluate the effects of storage conditions on the germination percentage, the viability and the coefficient of velocity of germination for seeds of three native tree species (Cedrela montana, Weinmannia fagaroides and Oreocallis grandiflora). Under controlled conditions, the seeds were exposed to three levels of seed moisture content and storage temperatures (5 °C, 10 °C and room temperature at approx. 19 °C) for 3, 6 and 12 months. The results showed that at 3–6 months of seed storage under temperatures of 5 and 10 °C, the seeds had a high percentage of germination, viability and germination speed for C. montana and W. fagaroides compared to those stored at room temperature. At 12 months of storage, there was a marked reduction in seed germination in all treatments for both species. Furthermore, the seed germination and viability of O. grandiflora was not influenced by any of the above storage treatments. However, at the end of the experiment a slight decrease was observed, hence this species might be tolerant to medium- and long-term storage conditions. Though limited to just three co-occurring species, the study provided insight into the variability in responses to storage, with preliminary indications of appropriate storage conditions to maximize storability of seeds for restoration programs. Importantly, the study demonstrated the need for empirical testing of storage responses (temperature and duration) of seeds before subjecting untested species to a particular storage regime.

Abstract:

In nutrient-poor tropical forests litter decomposition is essential for the supply of nutrients to plants. This process is in turn controlled by nutrient availability. Beside nitrogen (N) and phosphorus (P) other elements may co-limitate litter decomposition. Studies revealed a relationship between sodium (Na) shortage and reduced litter decomposition which can decrease the mineralization of stored carbon (C). Investigations of element fluxes of a Na-poor tropical montane rainforest in southern Ecuador have shown low atmospheric deposition rates since 1998. Additionally, Na was retained in different parts of the ecosystem. A study found that the Na-retention in the canopy was related to the Na demand of the microorganisms in the phyllosphere. Because the Na budget of the organic layer was also positive, it was assumed that decomposers may experience a lack of Na due to low atmospheric deposition. Thus, one main goal was to investigate whether Na fertilization accelerates litter decomposition. Based on the assumption of a higher Na demand of soil fauna than of microorganisms, it was also tested whether the stimulation of soil organisms by Na is limited to the soil fauna. To test these hypotheses, a combined litter decomposition and Na fertilization experiment was conducted in an evergreen premontane rainforest and a montane rainforest in south Ecuador. Fresh litter was incubated in the field and fertilized weekly with different Na concentrations which were similar to the natural deposition rates. Litterbags with different mesh sizes allowed to study the effects of Na fertilization on microbes and mesofauna separately. Additionally, a bait lamina experiment was installed in the organic layer to study the uptake of Na fertilized baits by soil organisms. Differences of the bait loss between the fertilized and the control group should indicate a potential stimulation of the soil organisms by a Na-addition. The statistical analysis confirmed the stimulation of litter decomposition by Na additions. The comparison of both sites revealed a slightly stronger effect of Na additions in the premontane forest than in the montane forest. The accelerated litter decomposition was related to an increased activity of the soil fauna. However, a significant stimulation of microorganisms by Na additions could not be detected. The bait lamina experiment confirmed the results of the litter decomposition experiment and showed a marginally significant increase of the activity of soil organisms by Na fertilization. Sodium can stimulate the decomposition of the organic layer in the studied premontane and montane rainforest, thus affecting ecosystem functioning. Na supply is of higher importance in the ecosystem than usually assumed and its relevance for the C turnover in the organic layer may increase if the atmospheric Na deposition remains on the present low level.

Abstract:

Herbivores play a key role for ecosystem functioning, but the current destruction of late-successional primary forests might negatively affect herbivore-mediated ecosystem processes. Understanding herbivore patterns between different succession stages is crucial for setting conservation priorities. Here we examined insect herbivore biomass and functional community composition along a successional gradient in a tropical montane rainforest in southern Ecuador. The insects were sampled off 42 tree individuals via canopy fogging. The trees comprised three succession stages (9 early, 25 intermediate, 18 late) and 16 species. Insect herbivores were identified on order level and assigned to one of three feeding guilds (leaf chewers, rostrum chewers, sapsuckers). Overall, we collected almost 16 000 herbivore individuals. Herbivore dry mass was not significantly affected by tree succession stage for almost all groups surveyed, except for caterpillars which weighed less on late- than on early-successional tree species. Furthermore, herbivore community composition was neither explained by tree succession stage nor by tree phylogeny. We conclude that solely conserving forests of late succession is not always expedient and that factors need to be identified which predict herbivory and herbivore community composition in tropical montane rainforests.

Abstract:

Being the most important herbivores in the tropics, insects play a key role in the trophic cascades and nutrient cycles of rainforest ecosystems. It is not fully understood, however, which drivers influence the biomass, abundance, individual size and functional community structure of these secondary consumers. In this study, we investigate the effects of morphological leaf traits such as leaf thickness, water content, physical resistance and specific leaf area on folivorous insect communities in the canopy of a primary tropical montane rainforest in South Ecuador. Via canopy fogging, we collected 52 community samples. Insects were assigned to five feeding guilds and their total and relative biomass, abundance and individual weights were modelled using leaf traits of the respective trees. We found that tree species identity was the main predictor of community structure. Leaf thickness and water content also played a significant role, the latter especially reducing the share of caterpillars within the community. Feeding guilds were differently affected by leaf characteristics: e.g. coleoptera and orthoptera showed no significant reaction to food quality parameters. Caterpillars again were the only group in which individual sizes were affected by leaf parameters. We assume that they respond more directly because of their need for efficient energy extraction and fast biomass accumulation rates. As water content was a main predictor in many of our models, we suggest that it be used as a measure of food quality in future research rather than N levels per dry mass because it better predicts nutrient levels in the fresh weight of leaves and it is fresh leaves that canopy-inhabiting folivorous insects consume.

Abstract:

Due to the high deforestation and climate change, the forests of Ecuador are endangered. In the future, there will be increasing drought, which is why the necessary afforestation have to be carried out with native tree species that meet these requirements. Therefore, it has to be clarified which tree species and provenances are suitable for this purpose. This thesis deals with the drought tolerance of Cedrela montana and Juglans neotropica in the greenhouse. The seeds of the plants come from four different regions in Ecuador. Ger-mination was carried out in two different temperature chambers. In the greenhouse, the two-year-old plants were divided into three groups that were supplied with different amount of water. During the drought stress-experiment group A received 100% of its water require-ment, group B 50% and group C 25%. After 14 weeks all groups were supplied with 100% of their water needs during the resilience-experiment. After three times of rehydration the desiccation-experiment started, in which the trees of all groups were no longer supplied with water. During the experiment series, water consumption, predawn and afternoon leaf water-potential and leaf status were documented. In addition, at the end of the test series, the growth and the root-shoot ratio were determined. Both tree species reacted very similar to the drought. There were hardly any differences in water consumption and water-potential. Only Cedrela montana had a higher number of leaves. The provenance and different germination temperatures had no significant influence. All groups reacted quickly to irrigation, so the afternoon water-potential were very similar in all groups. In the leaf status the gradation of the groups was still visible, but group B and C formed more leaves as the irrigation continued. Cedrela montana also had a higher number of leaves than Juglans neotropica. The germination treatment or provenance did not signif-icantly affect resilience. In the subsequent desiccation-experiment Group C of Juglans was best at dealing with the renewed dryness. This was evident in all parameters taken. All groups of Cedrela continued to behave similar. Significant differences could now be noted between germination treatments and provenances. In the aboveground growth, the grading of the groups was clearly recognizable, so in both tree species group A grew the most and group C the least. The root-shoot ratio behaved exactly the other way round. Group A had the lowest value on average, group C the highest. Again, significant differences between provenances and germination treatments were found.Both tree species showed a similar reaction over the course of the experiment, therefor both can be recommended for reforestation. The effects of germination conditions on the response to drought are not clear. For the species Cedrela montana, the provenance Barabon, and for Juglans neotropica, the Provenance Jipiro are considered to be suitable. As these have the largest root-shoot ratio, what makes them better equipped for increasing drought.