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

Abstract:

Nutrient deposition to tropical forests is increasing, which could affect soil fluxes of nitrous oxide (N2O), a powerful greenhouse gas. We assessed the effects of 35–56 months of moderate nitrogen (N) and phosphorus (P) additions on soil N2O fluxes and net soil N-cycling rates, and quantified the relative contributions of nitrification and denitrification to N2O fluxes. In 2008, a nutrient manipulation experiment was established along an elevation gradient (1000, 2000, and 3000 m) of montane forests in southern Ecuador. Treatments included control, N, P, and N+P addition (with additions of 50 kg N ha?1 yr?1 and 10 kg P ha?1 yr?1). Nitrous oxide fluxes were measured using static, vented chambers and N cycling was determined using the buried bag method. Measurements showed that denitrification was the main N2O source at all elevations, but that annual N2O emissions from control plots were low, and decreased along the elevation gradient (0.57 ± 0.26–0.05 ±0.04 kg N2O-N ha?1 yr?1). We attributed the low fluxes to our sites' conservative soil N cycling as well as gaseous N losses possibly being dominated by N2. Contrary to the first 21 months of the experiment, N addition did not affect N2O fluxes during the 35–56 month period, possibly due to low soil moisture contents during this time. With P addition, N2O fluxes and mineral N concentrations decreased during Months 35–56, presumably because plant P limitations were alleviated, increasing plant N uptake. Nitrogen plus phosphorus addition showed similar trends to N addition, but less pronounced given the counteracting effects of P addition. The combined results from this study (Months 1–21 and 35–56) showed that effects of N and P addition on soil N2O fluxes were not linear with time of exposure, highlighting the importance of long-term studies.

Abstract:

Nitrogen deposition to tropical forests is predicted to increase in future in many regions due to agricultural intensification. We conducted a seedling transplantation experiment in a tropical premontane forest in Ecuador with a locally abundant late-successional tree species (Pouteria torta, Sapotaceae) aimed at detecting species-specific responses to moderate N and P addition and to understand how increasing nutrient availability will affect regeneration. From locally collected seeds, 320 seedlings were produced and transplanted to the plots of the Ecuadorian Nutrient Manipulation Experiment (NUMEX) with three treatments (moderate N addition: 50 kg N ha?1 year?1, moderate P addition: 10 kg P ha?1 year?1 and combined N and P addition) and a control (80 plants per treatment). After 12 months, mortality, relative growth rate, leaf nutrient content and leaf herbivory rate were measured. N and NP addition significantly increased the mortality rate (70 vs. 54% in the control). However, N and P addition also increased the diameter growth rate of the surviving seedlings. N and P addition did not alter foliar nutrient concentrations and leaf N:P ratio, but N addition decreased the leaf C:N ratio and increased SLA. P addition (but not N addition) resulted in higher leaf area loss to herbivore consumption and also shifted carbon allocation to root growth. This fertilization experiment with a common rainforest tree species conducted in old-growth forest shows that already moderate doses of added N and P are affecting seedling performance which most likely will have consequences for the competitive strength in the understory and the recruitment success of P. torta. Simultaneous increases in growth, herbivory and mortality rates make it difficult to assess the species' overall performance and predict how a future increase in nutrient deposition will alter the abundance of this species in the Andean tropical montane forests.

Abstract:

The theory of portfolio selection has often been applied to help improving decisions on the environment. The information required to apply this theory includes data on covariance of the uncertain returns between all combinations of the economic options and normally distributed returns. As it may be problematic to fulfil all data requirements and assumptions, the paper proposes a variant of robust portfolio optimization as an alternative. It considers future uncer-tainties in a non-stochastic fashion by means of possible deviations from the nominal return of land-use alternatives. The maximization of the economic return of the land-use portfolio is conditional to meeting an inclusive set of constraints. These demand that the same, whenever possible high, proportion of a required return threshold is achieved by means of the robust solution for each deviation scenario considered. The paper compares the land-use portfolios derived non-stochastically with portfolios generated by classical stochastic mean-variance op-timization. Based on data for eight agricultural crops typical for the Ecuadorian lowlands the results show that, depending on the deviation scenario assumed, the robust portfolios show a greater Shannon index compared to classical portfolios. For the same standard deviation of returns (derived through the classical sum of all covariances) the robust portfolios show no more than 2-5% loss in economic return in most cases. Occasionally, the loss has been higher, up to 20%. In this case the Shannon index was about 2.5 times higher compared with that of the conventional portfolio. The highly diverse portfolio achieved a much better protection against low relative performance. The results obtained show that the non-stochastic derivation of land-use portfolios is a good alternative to the classical stochastic model, whenever eco-nomic information is scarce.

Abstract:

Tabebuia Bulletin Issue no 4, December 2015 The issue presents a bunch of Science and Knowledge-Transfer News. The first full-length paper in this journal shows in a model how the equilibrium between the pasture grass (Setaria) and the competing weed (bracken) depends on the temperature of the site, in other words on the elevation of the pasture. In the mountain rainforest, tree roots and the mycorrhiza fungi respond species-specifically to nutrient manipulations. Phosphate liberating soil enzymes depend on climatic conditions and thus on the altitudinal gradient. A study of the altitudinal gradient of tree assemblages disproved the general validity of the Tropical Conservatism Hypothesis. Using water use efficiency of the leaves and the total water consumption of the tree allows determination of its daily carbon uptake. Sodium availability could play an essential role in litter decomposition. In the dry forest different tree functional types can be recognized by quantification of their water relations. How to create a soil map for remote or less accessible areas? The Transfer News present a sampling design for digital soil mapping that closes the gap between the statistical desired quality of samples and operational applicability. The high resolution climate indicator system can be used to recognize climate change in southern Ecuador. In a workshop on the National Bird Day researchers from the Platform shared their dedication to bird diversity and seed dispersal with students from Zamora Chinchipe. Two more workshops transferred knowledge about science-directed advances in ecosystem monitoring and about the rehabilitation of abandoned areas for production and protection. More than 50% of the visits of the Data Warehouse are from outside the Research Consortium and climate data are expectedly the champions of downloads. News from the ECSF research station, the infrastructure provider NCI as well as the successful completion of three PhD thesis by Ecuadorian students round off this issue.

Abstract:

Deforestation and fragmentation are major components of global change; both are contributing to the rapid loss of tropical forest area with important implications for ecosystem functioning and biodiversity conservation. The forests of South Ecuador are a biological 'hotspot' due to their high diversity and endemism levels. We examined the deforestation and fragmentation patterns in this area of high conservation value using aerial photographs and Aster satellite scenes. The registered annual deforestation rates of 0.75% (1976–1989) and 2.86% (1989–2008) for two consecutive survey periods, the decreasing mean patch size and the increasing isolation of the forest fragments show that the area is under severe threat. Approximately 46% of South Ecuador's original forest cover had been converted by 2008 into pastures and other anthropogenic land cover types. We found that deforestation is more intense at lower elevations (premontane evergreen forest and shrubland) and that the deforestation front currently moves in upslope direction. Improved awareness of the spatial extent, dynamics and patterns of deforestation and forest fragmentation is urgently needed in biologically diverse areas like South Ecuador.

Abstract:

With respect to sampling for regression-based digital soil mapping (DSM), the above all aim is to ensure that the spatial variability of the soil is well-captured without introducing any bias, while the design remains feasible according to operational constraints such as accessibility, man power and cost. Representativeness of the sample concerning the population to be sampled needs to be guaranteed in any regression-based modelling approach. Four selected sampling designs were adapted to show that basically any design may be optimised to represent the n-dimensional predictor space of a particular area, while selecting points is only permitted from a small accessible sub-area or from outside the area. Sampling efficiency may be evaluated based on the representation of the predictor space. However, not only each predictor’s probability function but also the interaction between predictors may have to be considered, to select a representative sample. Instead of sampling a previously un-sampled area with limited accessibility, the four sampling designs may also be used to subsample an existing dataset and, thereby, optimise a suboptimal dataset based on the predictor space of the area which shall be mapped by DSM.

Abstract:

From 10 selected tree species, Bursera graveolens and Maclura tinctoria exhibited distinct annual and crossdatable tree-rings. It was possible to synchronize individual tree-ring series and to establish two tree-ring chronologies of 203 and 87 years length, respectively. The characteristic ENSO frequency band is reflected in wavelet power spectra of both chronologies. Both species showa strong correlation between ringwidth and precipitation of thewet season (January–May). Strong El Niño events (1972, 1983 and 1998) lead to strong growth responses in the tree-ring chronologies, whereas ‘normal’ ENSO events do not trigger long-lasting growth responses. The first ring-width based wet-season precipitation reconstruction for the past 103 years was developed. Statistical and spatial correlation analysis verified the skills of the reconstructed precipitation which captures a great part of the Rainfall Index over the land area of Ecuador and the equatorial Pacific. Furthermore, teleconnections with central Pacific precipitation and SST patterns were found.

Abstract:

The increasing anthropogenic influence on the environment on a global scale has led to a shift in nutrient cycles which are not fully understood yet. These shifts could alter the properties of ecosystems and therefore change habitats and species composition. Therefore it is crucial to understand nutrient cycles and how ecosystems react to these nutrient availability shifts. Especially the phosphorus and nitrogen cycles are highly important because of their direct influence on plant growth as primary macronutrients. Even in some so far undisturbed regions, a human caused rise in atmospheric input of phosphorus-containing particles is expected. One of the reasons therefor is land-use change in rural areas with associated combustions, from which the particles are transported downwind. This study simulates the prognosticated increased nutrient input and focuses on the following fate of the phosphorus in soil. For this, in 2008 a nutrient manipulation experiment was established to fertilize an old-growth tropical montane forest with moderate phosphorus (10 kg P ha-1 yr-1) and/or nitrogen additions (50 kg N ha-1 yr-1). This experimental setup was conducted for the first time at three altitudes (1000m a.s.l., 2000m a.s.l., 3000m a.s.l.) to compare the effects along an altitudinal gradient. After seven years the total phosphorus and bioavailable phosphorus concentrations of these locations were investigated in litterfall, the organic layer and in mineral soil to see if the added phosphorus is retained and enriched. The results showed that the application of the phosphorus fertilizer resulted in increased total and bioavailable phosphorus concentrations mainly in the organic layer. The phosphorus increase in mineral soil was not significant and indicated that the added phosphorus is not leached, but retained in the ecosystems. There were no effects on phosphorus concentrations after nitrogen addition. The altitudinal gradient referred to a pronounced difference between 1000m and the other altitudes (2000m and 3000m), due to the accumulated organic matter at the higher altitudes. Overall this study shows that the sustainable anthropogenic phosphorus increase may cause a change in the ecosystem’s characteristics and nutrient cycles.

Abstract:

After the coordinators’ updating of the state of research and introducing the new name of this publication, they summarize the important elements of the program for knowledge transfer to stakeholders. The local advisory board informs about a landslide which hit research grounds. Science papers in this issue • compare tropical montane elevation transects in Ecuador and Peru • analyze the relationship of decomposer communities and leaf litter types • demonstrate how fertilization influences the amount of bio-available phosphorus • reveal that nutrient availability stimulates mineralization of dissolved organic matter • show that image textures can supersede functional biodiversity analysis • provide insights into the transformation from abandoned sites to valuable pasture land. A report presents the completed construction of the last radar of the RadarNet Sur that is situated on a mountain peak and is the highest operating weather radar worldwide. The Data Warehouse manager describes the results of a survey taken to increase data quality and usability. And two workshops transferred gained knowledge on how to perform terrain analyses with the geographical information system SAGA.

Abstract:

Within this chapter relative air humidity, evaporation, transpiration, evapotranspiration, hydrologic cycle and water balance are discussed for the Tropics. In general, atmospheric water is of high climatological importance due to its capacity to control precipitation as well as to its influence on absorption and reflection of solar and terrestrial radiation. When water changes its state of aggregation, energy is either produced or consumed. This is crucial for the tropical atmosphere where the condensation of large amounts of water vapor leads to the release of latent heat energy. The global hydrosphere consists of a couple of different water reservoirs which are connected by water fluxes in various phases. From these reservoirs, water moves in a great series of continuous interchanges of both physical state and geographical position, known as the hydrologic cycle. Evapotranspiration is one of the most important factors for the water budget and physical processes in the tropics. It specifies the total flow of water into the atmosphere which is composed of two processes: evaporation and transpiration.

Abstract:

Within this chapter the Hadley Circulation, the Monsoon System, Easterly Waves, Tropical Cyclones and the Walker Circulation are discussed. While the Hadley Circulation and the Monsoon System explain different air flow systems in a mainly meridional sense, a secondary system of latitudinal wind flow is governed by the Walker circulation which is decisive for the formation of La Niña and El Niño events. Apart from the long-term seasonal and nonseasonal variations of the tropical atmosphere, the climate of the Tropics is also affected by more frequent tropical weather disturbances. One of them are large-scale planetary waves which produce greater amounts of rainfall in many maritime tropical regions. These disturbance lines sprawl in a meridional direction from east to west and are called easterly waves.

Abstract:

A main character of the entire tropics are the very low longitudinal gradients of air temperature of only 1 °C/1,000 km. In Fig. 1 (above) this is indicated by the broad reddish sector around the equator between 30°N and S and even beyond. A closer look at the upper image reveals darker patterns and hence the globally "hottest ecozone" over the Sahel and southern Sahara to the SE of the Arabian Peninsula. By far most of this section is part of the outer tropics. This "heat crest" north of the equator represents a thermal asymmetry and is linked to the large dimension of landmass in the northern half of Africa. Vertical termperature gradients in tropical mountains as well as changing meridional gradients of temperature amplitudes between the outer and inner tropics are presented by Figs. 2 and 3, resp. Diurnal an seasonal cycles are illustrated by thermoisopleths for different altitudes and under arid up to perhumid conditons (Figs. 4 and 5), which are also exampled for soil and surface temperatures (Fig. 6). Impacts of cold as well as of dry air intrusions (Figs. 7-9) are related to plant reactions and phenological aspects (Fig. 10).

Abstract:

Within this chapter different aspects of radiation and heat are discussed for the tropics. On a global scale the amount of annual solar radiation reaching the Earth's surface is determined by atmospheric and astronomical factors and the average energy budget of the Earth could be explained by the global radiation budget. Within the tropics the net radiation varies clearly across the different climatic regions. In the humid tropics the amount of net radiation shows an almost uniform annual pattern with two maxima per annum. In contrast to this, the horizontal course of the isopleths in a radiation isopleths diagram for the marginal tropics still indicates a marked diurnal cycle. At the Earth's surface, the total incoming radiation is transformed into different heat fluxes which are either directed towards the ground or to the atmosphere. In the tropical rainforests, only 10 % of the incoming radiation reaches the ground, and only a weak flow of sensible and latent heat exists from the forest canopy towards the forest ground and vice versa.

Abstract:

Large scale moisture patterns subdevide the year-round tropics from perarid up to perhumid subzones, which are combined with different degrees of cloudiness (Fig. 1) with convective heap clouds being of most importance (Figs. 2, 3, 4 and 5). A rather clear seasonal distribution of rainfall frequency and intensity (Fig. 7) governs the rythm of plant growth. Areas of highest precipitation amounts on the globe are concentrated on the inner parts of the tropics (Fig. 8), where thunderstorms are a typical feature of weather occurence. Long enduring droughts in wet as well as extraordinary rainfall intensities in arid regions are concentrated on distinct areas (Figs. 11 and 12). Most of the tropical high mounts show obvious "bulges" of enhanced rainfall rates at mid-elevations (Fig. 15).

Abstract:

Microclimatic differences between site conditions of forest ecosystems and farmlands are accented to clarify the significant importance of tree canopies for ecosystem services and agroforestry. An analyis of the climate within a tropical rainforest and its impact on epiphytic structure is given by Fig. 2. After forest conversion into farmland, radiation turnovers and energy flows as well as precipitation rates change dramatically (Figs. 3 and 4). Furthermore, clear-cuts of tropical forests enhance in destructive erosion processes during tropical downpours (Figs. 5, 6, and 8), which can reach impressive amounts during hurricane events (Fig. 7).

Abstract:

One of the most important climate criteria of the tropics is the absence of thermic seasons. Thus, hygric seasons become more relevant for ecosystem functioning and are of special importance for plant growth. Within this chapter different climate types of the tropics are discussed on the basis of their annual water budget. The humid climate type appears across the rain equator within or close to the ITCZ. It is distinguished by a clear water surplus and all months show a positive water balance in the long-term mean. The semi-humid climate type prevails at a certain distance from the Equator and the ITCZ. It is characterized by a distinct rainfall seasonality and the occurrence of more than 3 -4 arid months. In terms of the arid climate type the arid period is in general longer than the humid period and precipitation amounts decrease almost towards zero within the desert areas.

Abstract:

In this chapter, different aspects of climate variability at different time and spatial scales and their possible influences on ecosystems and biodiversity are discussed. A comprehensive full survey on climate change is presented in the fifth IPCC(Intergovernmental Panel on Climate Change) assessment report 2013/2014.

Abstract:

Unlike the high latitudes and most of the mid-latitudes, the tropical ecozone benefits from a constant radiation surplus. In daytime, the sunrays descend at a steep angle up to 90° at noon between the tropics twice per year. Hence,long-term shaded slopes in mountain landscapes do not exist. Lengths of day and night stay almost the same at the equator (approx. 12 h.), while at the Tropics of Cancer and Capricorn, minimum and maximum day lengths vary within a time span from 10.5 to 13.5 h. As a result marked thermal seasons are absent in the tropical climates.

Abstract:

Differences in the thermic and hygric seasonalities cause decisive distinctions between extratropical and tropical plant growth features. Around the tropics of Capricorn and Cancer noticeable seasonal cycles of temperature still occur, which are of minor importance within the megatherm inner tropics. Two classification systems offer a subdivision of the tropical climates. Compared to the frequently used Koeppen-approach, that one of Lauer is prefered here due to its clearly defined hygrothermal regimes. Altitudinal climate belts in the tropics are presented by a general scheme, while climate and vegetation profiles reflect a realistic situation alongside the neotropical Cordilleras.

Abstract:

This paper presents a method to extrapolate wind-speed data and to calculate wind-speed and dynamic pressure maps for the complex topography of a mountain rainforest area in the tropical Andes of southeastern Ecuador. The spatial differentiation of dynamic wind pressure in this area is claimed to be a major determinant of the altitude of the tree-line ecotone and to affect the tree line’s physiognomy. The paper presents a hybrid method encompassing statistical data analysis using the Weibull distribution and a digital terrain analysis, taking topographical shelter effects into account. The method is used to derive mean and maximum wind-speed and dynamic pressure maps to reveal whether the tree-line ecotone is influenced by direct wind effects. On average, the tree-line ecotone on the eastern slopes shows a clear average depression of ~50 m. These slopes are affected by higher dynamic wind stress, so have a more disturbed canopy. These altered vegetation structures may be caused mainly by direct wind effects and to a smaller extent by indirect effects, such as high humidity.

Abstract:

In the megadiverse tropical mountain forest in the Andes of southern Ecuador, a global biodiversity hotspot, the use of fire to clear land for cattle ranching is leading to the invasion of an aggressive weed, the bracken fern, which is threatening diversity and the provisioning of ecosystem services. To find sustainable land use options adapted to the local situation, a profound knowledge of the long-term spatiotemporal patterns of land cover change and its drivers is necessary, but hitherto lacking. The complex topography and the high cloud frequency make the use of remote sensing in this area a challenge. To deal with these conditions, we pursued specific pre-processing steps before classifying five Landsat scenes from 1975 to 2001. Then, we quantified land cover changes and habitat fragmentation, and we investigated landscape changes in relation to key spatial elements (altitude, slope, and distance from roads). Good classification results were obtained with overall accuracies ranging from 94.5% to 98.5% and Kappa statistics between 0.75 and 0.98. Forest was strongly fragmented due to the rapid expansion of the arable frontier and the even more rapid invasion by bracken. Unexpectedly, more bracken-infested areas were converted to pastures than vice versa, a practice that could alleviate pressure on forests if promoted. Road proximity was the most important spatial element determining forest loss, while for bracken the altitudinal range conditioned the degree of invasion in deforested areas. The annual deforestation rate changed notably between periods: ~1.5% from 1975 to 1987, ~0.8% from 1987 to 2000, and finally a very high rate of ~7.5% between 2000 and 2001. We explained these inconstant rates through some specific interrelated local and national political and socioeconomic drivers, namely land use policies, credit and tenure incentives, demography, and in particular, a severe national economic and bank crisis.

Abstract:

In undisturbed tropical montane rainforests massive organic layers accommodate the majority of roots and only a small fraction of roots penetrate the mineral soil. We investigated the contribution of vegetation to slope stability in such environments by modifying a standard model for slope stability to include an organic layer with distinct mechanical properties. The importance of individual model parameters was evaluated using detailed measurements of soil and vegetation properties to reproduce the observed depth of 11 shallow landslides in the Andes of southern Ecuador. By distinguishing mineral soil, organic layer and aboveground biomass, it is shown that in this environment vegetation provides a destabilizing effect mainly due to its contribution to the mass of the organic layer (up to 973 t ha
1 under wet conditions). Sensitivity analysis shows that the destabilizing effect of the mass of soil and vegetation can only be effective on slopes steeper than 37.9. This situation applies to 36% of the study area. Thus, on the steep slopes of this megadiverse ecosystem, the mass of the growing forest promotes landsliding, which in turn promotes a new cycle of succession. This feedback mechanism is worth consideration in further investigations of the impact of landslides on plant diversity in similar environments.