Publikationen
Es wurden 5 Publikationen gefunden
Wilcke, W.; Velescu, A.; Leimer, S.; Bigalke, M.; Boy, J. & Valarezo, C. (2019): Temporal Trends of Phosphorus Cycling in a Tropical Montane Forest in Ecuador During 14 Years. Journal of Geophysical Research: Biogeosciences 124, 1370-1386.
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DOI: 10.1029/2018JG004942
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Abstract:
Abstract:
Increased bioavailability of P can have a negative impact on plant biodiversity. In an approximately 9‐ha catchment under N + P‐limited megadiverse tropical montane forest in Ecuador, we budgeted all major P fluxes and determined whether the P fluxes changed from 1999 to 2013. Furthermore, we assessed which external drivers (rainfall, total P and acid deposition) caused this potential change. Mean (±SD) annual P deposition (bulk+dry) was 240 ± 270 mg/m2, with the SD reflecting the interannual variation. The annual P flux to the soil via throughfall+stemflow+litterfall was 1,400 ± 170 mg/m2 of which 18 ± 9.2% was leached to below the organic layer. The mineral soil retained 80 ± 12% of the P leached from the organic layer. The mean annual P weathering rate was 79 ± 63 mg/m2. The sum of P fluxes was approximately 5 times larger above than below the mineral soil surface, illustrating that P was tightly cycled in the biological part of the forest. The mean annual canopy budget was negative (−120 ± 280 mg/m2); that is, P was leached from the canopy. Throughfall was the largest source of dissolved P. The P catchment budget (total deposition‐streamflow) was positive (200 ± 270 mg/m2); that is, P was retained, mainly in the soil organic layer. From 1999 to 2013, P fluxes with throughfall, stemflow, and streamflow increased significantly. The strongest driver of the P budgets of the canopy and the catchment was total P deposition. Our results demonstrate that mainly biological processes retained deposited P in the vegetation and the organic layer enhancing the internal P cycle.
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Keywords: |
litterfall |
temporal trends |
catchment budget |
weathering rates |
phosphorus fluxes |
Wilcke, W.; Velescu, A.; Leimer, S.; Bigalke, M.; Boy, J. & Valarezo, C. (2017): Biological versus geochemical control and environmental change drivers of the base metal budgets of a tropical montane forest in Ecuador during 15 years. Biogeochemistry 136, 167-189.
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DOI: 10.1007/s10533-017-0386-x
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Abstract:
Abstract:
To assess the susceptibility of the base metal budget of a remote tropical montane forest in Ecuador to environmental change, we determined the extent of biological control of base metal fluxes and explored the impact of atmospheric inputs and precipitation considered as potential drivers of ecosystem change on the base metal fluxes. We quantified all major base metal fluxes in a ca. 9.1 ha forested catchment from 1998 to 2013. Mean (±s.d.) annual flux to the soil via throughfall+ stemflow+litterfall was 13800±1500 mg m-2 Ca, 19000±1510 mg m-2 K, 4690±619 mg m-2 Mg and 846±592 mg m-2 Na of which 22±6%, 45±16%, 39±10% and 84±33%, respectively, were leached to below the organic layer. The mineral soil retained 79-94% of this Ca, K and Mg, while Na was released. Weathering rates estimated with three different approaches ranged from not detected (ND) to 504 mg m-2 yr-1 Ca, ND-1769 mg m-2 yr-1 K, 287-597 mg m-2 yr-1 Mg and 403-540 mg m-2 yr-1 Na. The size of mainly biologically controlled aboveground fluxes of Ca, K and Mg was 1-2 orders of magnitude larger than that of mainly geochemically controlled fluxes (sorption to soil and weathering). The elemental catchment budgets (total deposition-streamflow) were positive for Ca (574±893 mg m-2) and K (1330±773 mg m-2), negative for Na (-370±1300 mg m-2) and neutral for Mg (1.89±304 mg m-2). Our results demonstrate that biological processes controlled element retention for Ca, K and Mg in the biological part of the ecosystem. This was different for Na, which was mainly released by weathering from the study catchment, while the biological part of the ecosystem was Na-poor. The deposition of base metals was the strongest driver of their budgets suggesting that the base metal cycling of the study ecosystem is susceptible to changing deposition.
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Keywords: |
throughfall |
litterfall |
stem flow |
alkaline dust deposition |
acid deposition |
catchment budget |
stream flow |
weathering rates |
Wagner, F.H.; Bräuning, A.; Homeier, J.; Spannl, S.; Volland, F. & et, a. (2016): Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests. Biogeosciences 13, 2537–2562.
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DOI: 10.5194/bg-13-2537-2016
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Abstract:
Abstract:
The seasonal climate drivers of the carbon cycle
in tropical forests remain poorly known, although these
forests account for more carbon assimilation and storage than
any other terrestrial ecosystem. Based on a unique combination
of seasonal pan-tropical data sets from 89 experimental
sites (68 include aboveground wood productivity measurements
and 35 litter productivity measurements), their associated
canopy photosynthetic capacity (enhanced vegetation
index, EVI) and climate, we ask how carbon assimilation
and aboveground allocation are related to climate seasonality
in tropical forests and how they interact in the seasonal
carbon cycle. We found that canopy photosynthetic capacity
seasonality responds positively to precipitation when rainfall
is < 2000mm/yr (water-limited forests) and to radiation
otherwise (light-limited forests). On the other hand, independent
of climate limitations, wood productivity and litterfall
are driven by seasonal variation in precipitation and
evapotranspiration, respectively. Consequently, light-limited
forests present an asynchronism between canopy photosynthetic
capacity and wood productivity. First-order control by
precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000mm/yr.
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Keywords: |
climate |
tree growth |
litterfall |
Ahlers, J. (2016): Variabilität der Feinstreuquantität und -qualität sowie die Auswirkungen einer kontinuierlichen N und P Düngung entlang eines Höhengradienten im tropischen Bergregenwald Südecuadors University of Goettingen, bachelor thesis
Eugster, A. (2014): Streueintraege und Umsatzzeiten von Schwermetallen in einem suedecuadorianischen Regenwald University of Berne, bachelor thesis
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Schwermetalle sind im Gegensatz zu Hauptnährelementen wie N, P oder S im Ökosystem gering angereichert, jedoch wirken diese schon bei kleinen Gehalten toxisch für Organismen wie Pflanzen und Tiere. Schwermetalle sind im Boden stabil und werden nicht abgebaut, nur die Verbindungen, die sie enthalten. Es kann auch zur Anreicherung von Schwermetallen in den Pflanzen, vor allem in Wurzeln und Blättern, kommen. Die Motivation der Bachelorarbeit besteht darin, sowohl die Flüsse der Schwermetalle in der Streu als auch deren Umsatzzeiten in der organischen Auflage des Waldbodens zu bestimmen. Es wurden Streuproben des Zeitraums Juli 2012 bis Februar 2013 aufgeschlossen und die Gehalte der Elemente As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V und Zn gemessen. Ausgewertet wurden jedoch die Messresultate der Proben von August 2011 bis Juli 2012. Die benötigten Daten zur Berechnung der Umsatzzeiten wurden von der Gruppe für Bodenkunde zur Verfügung gestellt. Die Schwermetallgehalte in der Streu dienten als Grundlage zur Berechnung der Monats- und Jahresflüsse sowie der Umsetzungsquotienten. Die Gehalte der Schwermetalle in der Streu zeigen kaum eine Variabilität über die Zeit. Die jährlich regelmässigen Schwankungen der Monatsflüsse sind auf die periodisch unterschiedlichen Streufallmengen zurückzuführen, die jeweils 2 Maxima und 1 Minimum aufweisen. Erstaunlich sind sowohl die hohen Kupfergehalte in der Streu als auch die hohen Umsetzungsquotienten für As, V und Fe. Die hohen Umsatzzeiten lassen sich durch Vermischung des Mineralbodenhorizonts mit der organischen Auflage erklären. Die Ursache der hohen Kupfereinträge konnte nicht abschliessend erläutert werden, jedoch wurden mögliche Lösungsansätze formuliert.
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Keywords: |
litterfall |
organic layer |
trace metals |
residence time |
element cycling |