TY - JOUR

T1 - Temporal Trends of Phosphorus Cycling in a Tropical Montane Forest in Ecuador During 14 Years

AU - Wilcke, Wolfgang

AU - Velescu, Andre

AU - Leimer, Sophia

AU - Bigalke, Moritz

AU - Boy, Jens

AU - Valarezo, Carlos

N1 - Funding information: We thank E. Beck, K. Müller? Hohenstein, M. Richter, and W. Zech for coinitiating the long?term study; K. Fleischbein, R. Goller, M. Meyer? Grünefeldt, M. Sequeira, H. Wullaert, S. Yasin, and numerous undergraduate students for data acquisition during parts of the observation period; W. Schädler for providing RFA data of rock macro element concentrations; the Ecuadorian Environmental Ministry for the research permits; and Naturaleza y Cultura Internacional (NCI) in Loja for providing the study area and the research station and the Deutsche Forschungsgemeinschaft (DFG) for funding (FOR402 and FOR816). The original data are included in the supporting information.

PY - 2019/5/30

Y1 - 2019/5/30

N2 - 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/m 2, with the SD reflecting the interannual variation. The annual P flux to the soil via throughfall+stemflow+litterfall was 1,400 ± 170 mg/m 2 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/m 2. 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/m 2); 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/m 2); 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.

AB - 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/m 2, with the SD reflecting the interannual variation. The annual P flux to the soil via throughfall+stemflow+litterfall was 1,400 ± 170 mg/m 2 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/m 2. 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/m 2); 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/m 2); 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.

KW - catchment budget

KW - litterfall

KW - phosphorus fluxes

KW - temporal trends

KW - weathering rates

UR - http://www.scopus.com/inward/record.url?scp=85066472148&partnerID=8YFLogxK

U2 - 10.1029/2018jg004942

DO - 10.1029/2018jg004942

M3 - Article

VL - 124

SP - 1370

EP - 1386

JO - Journal of Geophysical Research: Biogeosciences

JF - Journal of Geophysical Research: Biogeosciences

SN - 2169-8953

IS - 5

ER -