Wullaert, H.; Homeier, J.; Valarezo, C. & Wilcke, W. (2010): <b>Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments</b>. <i>Forest Ecology and Management</i> <b>260</b>, 1435-1445.
Resource Description
Title:
Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments
email:
wolfgang.wilcke <at> kit.edu
Karlsruhe Institute of Technology
Institute of Geography and Geoecology
Reinhard-Baumeister-Platz 1
76131 Karlsruhe
Baden-Württemberg
Germany
Abstract:
Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a<br/>
consequence of increasing human activities in the next decades. In the literature, it is frequently assumed<br/>
that tropical montane forests are N-limited, while tropical lowland forests are P-limited. In a low-level N<br/>
and P addition experiment, we determined the short-term response of N and P cycles in a north Andean<br/>
montane forest on Palaeozoic shists and metasandstones at an elevation of 2100m a.s.l. to increased N<br/>
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<br/>
of P and 50 kg + 10 kg ha−1 yr−1 of N and P, respectively) and an untreated control in a fourfold replicated<br/>
randomized block design. We collected litter leachate, mineral soil solution (0.15 and 0.30m depths),<br/>
throughfall and litterfall before the treatment began (August 2007) until 16 months after the first nutrient<br/>
application (April 2009). Less than 10 and 1% of the applied N and P, respectively, leached below the<br/>
organic layer which contained almost all roots and no significant leaching losses of N and P occurred<br/>
to below 0.15m mineral soil depth. Deposited N and P from the atmosphere in dry and wet form were<br/>
retained in the canopy of the control treatment using a canopy budget model. Nitrogen and P retention<br/>
by the canopy were reduced and N and P fluxes in throughfall and litterfall increased in their respective<br/>
treatments. The increase in N and P fluxes in throughfall after fertilization was equivalent to 2.5% of the<br/>
applied N and 2% of the applied P. The fluxes of N and P in litterfall were up to 15% and 3%, respectively,<br/>
higher in the N and N+ P than in the control treatments. We conclude that the expected elevated N and P<br/>
deposition in the tropics will be retained in the ecosystem, at least in the short term and hence, N and P<br/>
concentrations in stream water will not increase. Our results suggest that in the studied tropical montane<br/>
forest ecosystem on Palaeozoic bedrock, N and P are co-limiting the growth of organisms in the canopy<br/>
and organic layer.
Keywords:
| tropical montane forest | nutrient cycle | leaching losses | N deposition | P deposition | environmental change |
