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

Resumen:

Montane ecosystems are known for their high numbers of endemic species, unique climate conditions, and wide variety of ecosystem services such as water supply and carbon storage. Although many ecohydrological and climatic studies of montane environments have been carried out in temperate and boreal regions, few have been done in Neotropical regions. Hence, the objective of this review is to synthesize the existing literature on the main factors (biotic and abiotic) that influence vegetation distribution, functional traits, and ecohydrological processes and feedbacks in tropical montane ecosystems and to identify key knowledge gaps. Most of the literature used includes work conducted in Neotropical montane rainforests, cloud forests, and grass/scrublands (e.g., páramos, punas, and campos de altitude/rupestres). Fog is a major cli- matic attribute in tropical montane habitats. We found that fog regimes (frequency and intensity of fog events) influence both water inputs (i.e., canopy interception and foliar water uptake) and outputs (evapotranspiration) and represent an important driver of local species composition, dominance of plant functional types, and ecological functioning. The stability and conservation of tropical montane ecosystems depends on such ecohydrological fluxes, which are sensitive to increases in air temperature and changing precipitation and fog regimes. Furthermore, to better inform effective conservation and restoration strategies, more work is needed to elucidate how key ecohydrological processes are affected by land use conversion to agriculture and pasture lands, as human activities influence the water budgets in Neotropical montane watersheds not only at regional?scales but also globally. KEYWORDS

Resumen:

As part of an interdisciplinary research programme, the spatial and temporal variability of precipitation in southern Ecuador has been investigated since January 2002. The study site is located at the northern margin of the Podocarpus National Park in the vicinity of Loja, about 500 km south of Quito, at altitudes ranging from 1800 to 3200 m.a.s.l. Due to its low density, the conventional rainfall station network fails to register the highly variable spatial distribution of rain, whereas contributions by fog are not accounted at all. Hence, for the first time in a tropical montane forest setting, a weather radar was used, covering a radius of 60 km and reaching from the Amazon Basin to the coastal plains of the region. Furthermore, a network of sampling stations supplies data about the altitudinal gradient of fog and rainwater inputs. The precipitation distribution in the study area proves to be far more variable than previously thought and is strongly coupled to the orographic characteristics and the special topographical setting of the landscape. Maxima in precipitation occur especially in the eastern parts of the radar range on slopes exposed to advected moisture from the Amazon Basin, whereas the highest crests of the Andes receive less precipitation. The study area has two cloud condensation levels, occurring at 1500?2000 and 2500?3500 m.a.s.l., respectively. At 1800?2000 m.a.s.l., fog is estimated to contribute an additional input of 5% of conventionally measured rainfall, increasing to about 35% at the highest measurement station (3200 m.a.s.l.). In contrast to some other tropical mountains, there seems to be no maximum zone of water input, although the gradient remains positive up to the highest altitudes. The unusual precipitation distribution is thought to reflect the contrasting climatological influences operating in the study area.