Recuperation of nitrogen cycling in Amazonian forests following agricultural abandonment.
Phosphorus (P) is generally considered the most common limiting nutrient for productivity of mature tropical lowland forests growing on highly weathered soils. It is often assumed that P limitation also applies to young tropical forests, but nitrogen (N) losses during land-use change may alter the stoichiometric balance of nutrient cycling processes. In the Amazon basin, about 16% of the original forest area has been cleared, and about 30-50% of cleared land is estimated now to be in some stage of secondary forest succession following agricultural abandonment. Here we use forest age chronosequences to demonstrate that young successional forests growing after agricultural abandonment on highly weathered lowland tropical soils exhibit conservative N-cycling properties much like those of N-limited forests on younger soils in temperate latitudes. As secondary succession progresses, N-cycling properties recover and the dominance of a conservative P cycle typical of mature lowland tropical forests re-emerges. These successional shifts in N:P cycling ratios with forest age provide a mechanistic explanation for initially lower and then gradually increasing soil emissions of the greenhouse gas nitrous oxide (N(2)O). The patterns of N and P cycling during secondary forest succession, demonstrated here over decadal timescales, are similar to N- and P-cycling patterns during primary succession as soils age over thousands and millions of years, thus revealing that N availability in terrestrial ecosystems is ephemeral and can be disrupted by either natural or anthropogenic disturbances at several timescales.
Davidson
Eric A
EA
The Woods Hole Research Center, 149 Woods Hole Road, Falmouth, Massachusetts 02540-1644, USA. edavidson@whrc.org
de Carvalho
Cláudio J Reis
CJ
Figueira
Adelaine Michela
AM
Ishida
Françoise Yoko
FY
Ometto
Jean Pierre H B
JP
Nardoto
Gabriela B
GB
Sabá
Renata Tuma
RT
Hayashi
Sanae N
SN
Leal
Eliane C
EC
Vieira
Ima Célia G
IC
Martinelli
Luiz A
LA
D000383:Agriculture; D001938:Brazil; D017753:Ecosystem; D009584:Nitrogen / Q000378:metabolism*; D009609:Nitrous Oxide / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D012987:Soil / Q000032:analysis; D013997:Time Factors; D014197:Trees / Q000378:metabolism*
D012987:Soil; D010758:Phosphorus; D009609:Nitrous Oxide; D009584:Nitrogen