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

Abstract:

This study examines the seasonal and diurnal dynamics of convective cloud entities?small cells and a mesoscale convective complex?like pattern?in the foothills of the tropical eastern Andes. The investigation is based on Geostationary Operational Environmental Satellite-East (GOES-E) satellite imagery (2005?2007), images of a scanning X-band rain radar, and data from regular meteorological stations. The work was conducted in the framework of a major ecological research program, the Research Unit 816, in which meteorological instruments are installed in the Rio San Francisco valley, breaching the eastern Andes of south Ecuador. GOES image segmentation to discriminate convective cells and other clouds is performed for a 600 3 600 km2 target area, using the concept of connected component labeling by applying the 8-connectivity scheme as well as thresholds for minimum blackbody temperature, spatial extent, and eccentricity of the extracted components. The results show that the formation of convective clouds in the lowland part of the target area mainly occurs in austral summer during late afternoon. Nocturnal enhancement of cell formation could be observed from October to April (particularly February?April) between 0100 and 0400 LST (LST 5 UTC 2 5 h) in the Andean foothill region of the target area, which is the relatively dry season of the adjacent eastern Andean slopes. Nocturnal cell formation is especially marked southeast of the Rio San Francisco Valley in the southeast Andes of Ecuador, where a confluence area of major katabatic outflow systems coincide with a quasi-concave shape of the Andean terrain line. The confluent cold-air drainage flow leads to low-level instability and cellular convection in the warm, moist Amazon air mass. The novel result of the current study is to provide statistical evidence that, under these special topographic situations, katabatic outflow is strong enough to generate mainly multiconvective complexes (MCCs AU1 ) with a great spatial extent. The MCC-like systems often increase in expanse during their mature phase and propagate toward the Andes because of the prevailing upper-air easterlies, causing early morning peaks of rainfall in the valley of the Rio San Francisco. It is striking that MCC formation in the foothill area is clearly reduced during the main rainy season [June?August (JJA)] of the higher eastern Andean slopes. At a first glance, this contradiction can be explained by rainfall persistence in the Rio San Francisco Valley, which is clearly lower during the time of convective activity (December?April) in comparison to JJA, during which low-intensity rainfall is released by predominantly advective clouds with greater temporal endurance.

Abstract:

The Andes of Ecuador are known for their outstanding biodiversity but also as the region with the highest deforestation rate in South America. This process is accompanied by accelerating degradation and loss of environmental services. Despite an extraordinary richness in native tree diversity, more than 90% of all forest plantations established in Ecuador consist of exotic species, primarily Eucalyptus spp. and Pinus spp. This is mainly due to the lack of information about the autecological and synecological requirements of the native species. The present study aims at providing basic knowledge on the early height development of native species in comparison to exotics. 12,000 seedlings of exotic and native species were planted in experimental trials at three sites of different successional stages: recently abandoned pastures (Setaria sphacelata), bracken (Pteridium arachnoideum) and shrubs. The results presented in this study refer to the status of the seedlings 3 years after planting. Soil data were revealed from soil core analysis from a total of 1008 soil samples distributed systematically over all plots. Soil chemical data were derived from a subsample of 125 randomly selected soil core sites. Soil properties in the study area emerged to be extremely heterogeneous. More than 60% of all plots presented two or more soil clusters. Soils in general were very poor in plant available N. Soil heterogeneity affected extractable Mn and Mg, dominating vegetation cover in turn affected Mn and P. Differences in soil properties had a strong effect for Eucalyptus saligna and Alnus acuminata. Manual above ground weeding showed species-specific effects: Tabebuia chrysantha and Heliocarpus americanus showed improved height growth, while that of Cedrela montana was reduced. There is evidence that A. acuminata can compete in growth with exotic species. Early successional species and exotics performed best on pasture dominated sites. Height growth of the mid-successional species C. montana was facilitated by bracken fern under certain soil conditions, and shrubs facilitated growth of T. chrysantha. The results indicate that reforestation with native species in Ecuador is possible but requires intensive consideration of interactions with soil properties and accompanying vegetation. Macroscopic soil core analysis can be a suitable instrument for detecting small-scale variation of soil properties. Nevertheless, a characterisation of both small-scale variation as well as variation on higher spatial scales, for instance by aerial photographs, is essential for effective planning of reforestation measures in the Andes.

Abstract:

Late Pleistocene and Holocene vegetation, climate and fire dynamics of mountain forest and paramo ecosystems, as well as human impact, are presented from the Cocha Caranga area, at 2710 m elevation in the Podocarpus National Park, southeastern Ecuadorian Andes. Palaeoenvironmental changes, inferred from two sediment cores and a soil core were investigated by pollen, spore, algae and charcoal analyses. During the transition from late Pleistocene to early Holocene between ca. 14,500 to 9700 cal yr BP upper mountain forest vegetation expanded, suggesting increasing temperature and moisture. This expansion abruptly stopped with increasing fires at ca. 9700 cal yr BP and open grassy vegetation became established. The period from ca. 9700 to 1300 cal yr BP of strong fire intensity indicate that vegetation components, mainly Weinmannia and Myrica, react sensitively to past, probably human caused fires. During the last few centuries modern vegetation established, characterised by open grassy areas with forest patches and small mires. The green algae Botryococcus braunii, Isoetes and Cyperaceae were used to identify lake level fluctuation to reconstruct Holocene wet/dry phases. Drier climatic conditions occurred from ca. 9700 to 6900 cal yr BP and from ca. 4200 to 1300 cal yr BP. From ca. 6900 to 4200 cal yr BP and from ca. 1300 cal yr BP to modern times, wetter climatic conditions occurred.

Abstract:

If tropical farmers cannot be provided with sustainable land-use systems, which address their subsistence needs and keep them gainfully employed, tropical forests will continue to disappear. We looked at the ability of economic land-use diversification ? with reforestation of tropical ?wastelands? as a key activity ? to halt deforestation at the farm level. Our ecological?economic concept, based on land-use data from the buffer area of the Podocarpus National Park in southern Ecuador, shows that stopping deforestation after 10 years is possible without violating subsistence demands. Tropical, farm-level diversification may not only reduce total deforestation by 45%, but also increase farmers? profits by 65%, because the formerly unproductive wastelands have been returned to productive land use. We therefore conclude that a ?win?win? scenario is possible: the subsistence needs of people can be reconciled with conservation objectives. However, inexpensive microcredits (at interest rates below 6%) and experience on alternative land-use opportunities must be offered to farmers.

Abstract:

A land-cover classification is needed to deduce surface boundary conditions for a soil?vegetation?atmosphere transfer (SVAT) scheme that is operated by a geoecological research unit working in the Andes of southern Ecuador. Landsat Enhanced Thematic Mapper Plus (ETM + ) data are used to classify distinct vegetation types in the tropical mountain forest. Besides a hard classification, a soft classification technique is applied. Dempster?Shafer evidence theory is used to analyse the quality of the spectral training sites and a modified linear spectral unmixing technique is selected to produce abundancies of the spectral endmembers. The hard classification provides very good results, with a Kappa value of 0.86. The Dempster?Shafer ambiguity underlines the good quality of the training sites and the probability guided spectral unmixing is chosen for the determination of plant functional types for the land model. A similar model run with a spatial distribution of land cover from both the hard and the soft classification processes clearly points to more realistic model results by using the land surface based on the probability guided spectral unmixing technique.

Abstract:

Successful conservation of tropical montane forest, one of the most threatened ecosystems on earth, requires detailed knowledge of its biogeochemistry. Of particular interest is the response of the biogeochemical element cycles to external influences such as element deposition or climate change. Therefore the overall objective of my study was to contribute to improved understanding of role and functioning of the Andean tropical montane forest. In detail, my objectives were to determine (1) the role of longrange transported aerosols and their transport mechanisms, and (2) the role of short-term extreme climatic events for the element budget of Andean tropical forest. In a whole-catchment approach including three 8-13 ha microcatchments under tropical montane forest on the east-exposed slope of the eastern cordillera in the south Ecuadorian Andes at 1850-2200 m above sea level I monitored at least in weekly resolution the concentrations and fluxes of Ca, Mg, Na, K, NO3-N, NH4-N, DON, P, S, TOC, Mn, and Al in bulk deposition, throughfall, litter leachate, soil solution at the 0.15 and 0.3 m depths, and runoff between May 1998 and April 2003. I also used meteorological data from my study area collected by cooperating researchers and the Brazilian meteorological service (INPE), as well as remote sensing products of the North American and European space agencies NASA and ESA. My results show that (1) there was a strong interannual variation in deposition of Ca [4.4-29 kg ha-1 a-1], Mg [1.6-12], and K [9.8-30]) between 1998 and 2003. 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. There were also significantly elevated H+, N, and Mn depositions during the annual biomass burning period in the Amazon basin. Elevated H+ deposition during the biomass burning period caused elevated base metal loss from the canopy and the organic horizon and deteriorated already low base metal supply of the vegetation. Nitrogen was only retained during biomass burning but not during non-fire conditions when deposition was much smaller. Therefore biomass burning-related aerosol emissions in Amazonia seem 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 Niño situations, a shortened ENSO cycle because of global warming likely enhances the acid deposition at my study forest. (2) Storm events causing near-surface water flow through C- and nutrient-rich topsoil during rainstorms were 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. This demonstrates that storm-event related near-surface flow markedly affects the cycling of many nutrients in steep tropical montane forests. Changes in the rainfall regime possibly associated with global climate change will therefore also change element export from the study forest. Element budgets of Andean tropical montane rain forest proved to be markedly affected by long-range transport of Saharan dust, biomass burning-related aerosols, or strong rainfalls during storm events. Thus, increased acid and nutrient deposition and the global climate change probably drive the tropical montane forest to another state with unknown consequences for its functions and biological diversity.