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:

In dieser Arbeit wird die Fauna von Arthropoden auf der lebenden Rinde von Bäumen im Podocarpus Nationalpark Südecuadors auf ihre räumliche und altitudinale (Höhengradient) Verteilung hin untersucht. Die Proben wurden mit Hilfe von ?barkspraying? gewonnen, die zu untersuchenden Bäume wurden standardisiert im unteren Stammbereich mit Insektenspray besprüht, und die herabfallenden Arthropoden mit einer Folienplane, die direkt am Baumfuß angebracht wurde, aufgefangen. Die Proben wurden in einem kurzen Zeitraum 17.09.2007 - 03.10.2007 innerhalb von 6 Probeflächen (plots) erfasst, um eine andere Probenzusammensetzung aufgrund jahreszeitlicher Unterschiede ausschließen zu können. Die 71 beprobten Bäume waren über drei verschiedene Höhenlagen des Andenosthangs (Höhengradient, Bombuscaro 1000m (2 plots), ECSF 2000m (3 plots) und Cajanuma 3000m (1 plot) verteilt. Die Proben, die insgesamt 4361 Arthropoden enthielten, wurden von der Autorin auf Ordnungsniveau bestimmt bzw. sortiert und dokumentiert, um im Anschluss verschiedene Analysen durchführen zu können. So wurde zum einen die Verteilung der Individuenzahl auf die jeweiligen Arthropodengruppen betrachtet. Die Coleoptera (Käfer) stellten die größte Gruppe, gefolgt von den Collembolen (Springschwänze), den Acari (Milben) und den Diptera (Zweiflüglern). Weiterhin wurde die Verteilung der Arthropoden innerhalb der jeweiligen Probeflächen (plots) und die Unterschiede zwischen den einzelnen plots betrachtet. Die Individuenzahl und die Zusammensetzung der Fauna der verschiedenen plots unterscheidet sich je nach Standort, und insbesondere die altitudinale Verteilung wies spezielle Muster auf. Zum Beispiel sank die Individuenzahl der Schaben mit zunehmender Höhenlage stark ab. Vergleicht man die Individuendichte der Arthropoden auf der Baumrinde normiert auf Zentimeter des Brusthöhen-Durchmessers, wird ersichtlich, dass sich die geringste Individuendichte in Höhenlage 1000m gefolgt von Höhenlage 3000m findet, während die höchste Individuendichte sich im Bergregenwald in 2000m Höhenlage (ECSF) befindet, wo nach aktueller Literatur (BECK & KOTTKE, 2008; NÖSKE ET AL, 2008) im Höhengradienten auch die höchste Artenzahl bei vielen Arthropodengruppen zu finden ist. Eine Korrespondenzanalyse aller 71 samples (barkspray-Proben) bildet einen klaren Höhengradienten ab, dem die Lebendgemeinschaften auf der Rinde folgen.