کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
88724 159317 2009 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Soil N cycling in old-growth forests across an Andosol toposequence in Ecuador
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم کشاورزی و بیولوژیک بوم شناسی، تکامل، رفتار و سامانه شناسی
پیش نمایش صفحه اول مقاله
Soil N cycling in old-growth forests across an Andosol toposequence in Ecuador
چکیده انگلیسی

Nitrogen (N) deposition in the tropics is predicted to increase drastically in the next decades. The sparse information on N cycling in tropical forests revealed that the soil N status of an ecosystem is the key to analyze its reactions to projected increase in N input. Our study was aimed at (1) comparing the soil N availability of forest sites across an Ecuadorian Andosol toposequence by quantifying gross rates of soil N cycling in situ, and (2) determining the factors controlling the differences in soil N cycling across sites. The toposequence was represented by five old-growth forest sites with elevations ranging from 300 m to 1500 m. Our results provide general insights into the role of elevation-mediated factors (i.e. degree of soil development and temperature) in driving patterns of soil N cycling. Gross rates of N transformations, microbial N turnover time, and δ15N signatures in soil and leaf litter decreased with increasing elevation, signifying a decreasing N availability across the toposequence. This was paralleled by a decreasing degree of soil development with increasing elevation, as indicated by declining clay contents, total C, total N, effective cation exchange capacity and increasing base saturation. Soil N-cycling rates and δ15N signatures were highly correlated with mean annual temperature but not with mean annual rainfall and soil moisture which did not systematically vary across the toposequence. Microbial immobilization was the largest fate of produced NH4+ across all sites, and nitrification activity was only 5–11% of gross NH4+ production. We observed a fast reaction of NO3− to organic N and its role for N retention deserves further attention. If projected increase in N deposition will occur, the timing and magnitude of gaseous N losses may follow the pattern of N availability across this Andosol toposequence.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Forest Ecology and Management - Volume 257, Issue 10, 30 April 2009, Pages 2079–2087
نویسندگان
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