Abstract booklet - gtö – Society for Tropical Ecology

28 PARALLEL SESSION HALL H III: THE ANDEAN BIODIVERSITY HOTSPOTPARALLEL SESSION HALL H III: THE ANDEAN BIODIVERSITY HOTSPOT 29MONDAY 16:30 Hall H IIIACCESSIBILITY PREDICTS THE DEGREE OF DEGRADATIONOF ANDEAN POLYLEPIS FORESTSJohanna Toivonen 11University of Turku, Turku, FI, jomito@utu.fiHigh mountain forests of the central Andes are formed almost purely by treesof the genus Polylepis. These forests occur nowadays as scattered remnantpatches of a more continuous past distribution. Apparently, the destruction ofPolylepis forests has mainly been caused by millennia of human disturbance,although forest distribution may also have fluctuated according to prevailingclimatic conditions. Nowadays, the remaining Polylepis forest stands are stillthreatened byanthropogenic disturbance, which gradually degrades the forests. The aim ofour study was to examine Polylepis forest structure and regeneration in relationto elevation in dry and humid climates and totest the relationship of human accessibility on the forest structure andregeneration in the Cordilleras Vilcanota and Vilcabamba, Cuzco, Peru. Wefound relations of forest structural parameters and regeneration with elevationopposite to those expected in dry areas, whereas in humid areas the parametersmostly followed general elevational patterns. We also found that accessibility -quantified as geographical distance to the nearest village, to the nearest pavedroad or railway station, or to the nearest regional market centre - was closelyrelated to forest structure and regeneration in both dry and humid areas, butthat the relationships of these variables differed between the areas. Thesefindings presumably reflect regional differences in human occupation betweendry and humid areas. Our results also indicate that simple geographicalpredictors can be used for rapid spatial estimation of the degree of Polylepisforest degradation. These estimations are advantageous in the identificationof the areas, where Polylepis forests are potentially the most degraded andconservation activities are urgently needed.RESPONSE OF A TROPICAL MONTANE FORESTAT THE RIM OF THE AMAZON BASIN IN SOUTH ECUADORTO LOW-LEVEL N, P, AND CA AMENDMENTSWolfgang Wilcke 1 , Hans Wullaert 2 , Judith Minker 3 , Carlos Valarezo 4 ,Jürgen Homeier 51University of Berne, Berne, CH, wolfgang.wilcke@giub.unibe.ch, 2 JohannesGutenberg University Mainz, Mainz, DE, 3 Westfalian Wilhelms University Münster,Münster, DE, 4 National University of Loja, Loja, EC, 5 Georg August UniversityGöttingen, Göttingen, DEFor the near future increasing deposition of nutrients including N, P, and basemetals is expected in the tropics because of the economic development andclimate change.In a multidisciplinary effort, we conducted a field experiment in undisturbedtropical montane forest at ca. 2100 m a.s.l. in south Ecuador which is exposedto the Amazon basin to explore the effect of increasing nutrient deposition.In 2007, we started to amend low amounts of N (50 kg ha-1), P (10 kg ha-1),N+P (50+10 kg ha-1), and Ca (10 kg ha-1) split between two annual fertilizingdates to soil in a fourfold replicated randomized block design that also includedunfertilized control plots. In the soil scientific subproject we focused on elementfluxes with throughfall, litterfall, and soil water at different depths in soil (belowthe organic layer and at the 0.15 and 0.30 m mineral soil depths).There was little leaching of the added nutrients into the mineral soil (1-10%of the fertilized amount) indicating that the elements were taken up by thevegetation or microbially immobilized in the soil solution. The latter was furthersupported by the fact that part of the fertilized elements appeared in litterfallsoon after nutrient application (2-2.5%). Furthermore, the fertilizer applicationreduced the net retention of N, P, and Ca in the canopy based on a canopybudget approach suggesting a reduced demand of the vegetation for thesenutrients.Overall, the element cycling in the forest responded quickly to all addednutrients in a similar way.MONDAY 16:45 Hall H IIIgtöSociety for Tropical Ecology | Gesellschaft für Tropenökologie e.V. Status and future of tropical biodiversity | Frankfurt, 21 - 24 February 2011gtö