02556naa a2200325 a 450000100080000000500110000800800410001902400290006010000200008924501170010926000090022650000330023552016390026865000130190765000160192065000130193665000160194965300110196570000260197670000200200270000180202270000240204070000190206470000170208370000190210070000160211970000210213570000220215677300520217814090002022-11-23       2007    bl uuuu     u00u1 u    #d7 a10.1038/nature059002DOI1 aDAVIDSON, E. A.  aRecuperation of nitrogen cycling in Amazonian forests following agricultural abandonment.h[electronic resource]  c2007  aDisponível também on-line.  aPhosphorus (P) is generally considered the most common limiting nutrient for productivity of mature tropical lowland forests growing on highly weathered soils1, 2, 3, 4, 5. 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 cleared6, and about 30?50% of cleared land is estimated now to be in some stage of secondary forest succession following agricultural abandonment7. 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 (N2O). 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.  aAmazonia  aAgricultura  aFloresta  aNitrogênio  aBrasil1 aCARVALHO, C. J. R. de1 aFIGUEIRA, A. M.1 aISHIDA, F. Y.1 aOMETTO, J. P. H. B.1 aNARDOTO, G. B.1 aSABÁ, R. T.1 aHAYASHI, S. N.1 aLEAL, E. C.1 aVIEIRA, I. C. G.1 aMARTINELLI, L. A.  tNaturegv. 447, n. 7147, p. 995-998, Jun. 2007.