Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments

FOREST ECOLOGY AND MANAGEMENT

卷:260

Article

Wullaert, H.²  Valarezo, C.^3,4  Wilcke, W.¹ 

[1] Univ Bern, Inst Geog, CH-3012 Bern, Switzerland

[2] Johannes Gutenberg Univ Mainz, Earth Syst Sci Res Ctr, Inst Geog, Mainz, Germany

[3] Univ Gottingen, Albrecht von Haller Inst Plant Sci, Gottingen, Germany

[4] Univ Natl de Loja, Direcc Gen Invest, Sector La Argelia, Loja, Ecuador

关键词: Tropical montane forest;    Nutrient cycle;    Leaching losses;    N deposition;    P deposition;    Environmental change;   

DOI  :  10.1016/j.foreco.2010.07.021

来源: Elsevier

【 摘 要 】

Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a consequence of increasing human activities in the next decades. In the literature, it is frequently assumed that tropical montane forests are N-limited, while tropical lowland forests are P-limited. In a low-level N and P addition experiment, we determined the short-term response of N and P cycles in a north Andean montane forest on Palaeozoic shists and metasandstones at an elevation of 2100 m a.s.l. to increased N and P inputs. We evaluated experimental N. P and N + P additions (50 kg ha(-1) yr(-1) of N, 10 kg ha(-1) yr(-1) of P and 50 kg + 10 kg ha(-1) yr(-1) of N and P. respectively) and an untreated control in a fourfold replicated randomized block design. We collected litter leachate, mineral soil solution (0.15 and 0.30m depths), throughfall and litterfall before the treatment began (August 2007) until 16 months after the first nutrient application (April 2009). Less than 10 and 1% of the applied N and P. respectively, leached below the organic layer which contained almost all roots and no significant leaching losses of N and P occurred to below 0.15 m mineral soil depth. Deposited N and P from the atmosphere in dry and wet form were retained in the canopy of the control treatment using a canopy budget model. Nitrogen and P retention by the canopy were reduced and N and P fluxes in throughfall and litterfall increased in their respective treatments. The increase in N and P fluxes in throughfall after fertilization was equivalent to 2.5% of the applied N and 2% of the applied P. The fluxes of N and Pin litterfall were up to 15% and 3%, respectively, higher in the N and N + P than in the control treatments. We conclude that the expected elevated N and P deposition in the tropics will be retained in the ecosystem, at least in the short term and hence, N and P concentrations in stream water will not increase. Our results suggest that in the studied tropical montane forest ecosystem on Palaeozoic bedrock, N and P are co-limiting the growth of organisms in the canopy and organic layer. (C) 2010 Elsevier B.V. All rights reserved.

【 授权许可】

Free