Recuperation of nitrogen cycling in Amazonian forests following agricultural abandonment. Nature

The Woods Hole Research Center, 149 Woods Hole Road, Falmouth, Massachusetts 02540-1644, USA.
Nature (Impact Factor: 41.46). 07/2007; 447(7147):995-8. DOI: 10.1038/nature05900
Source: PubMed


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.

Download full-text


Available from: Cláudio José Reis de Carvalho, Apr 02, 2014
  • Source
    • "esse elemento na serapilheira . Ao estudar o acúmulo e decomposição da serapilheira em quatro formações florestais , Cunha Neto et al . ( 2013 ) , também constataram maiores teores e conteúdos de N na formação florestal da Leguminosae Acacia mangium , e relacionaram os maiores valores nessa formação à capacidade da espécie em fixar nitrogênio . Já Davidson et al . ( 2007 ) , relatam que as florestas tropicais são limitadas por N nas etapas iniciais da sucessão , com maior ciclagem interna e perda reduzida desse nutriente . Assim , essas evidências acima podem explicar os maiores valores de N na FSEA e os menores na FSEM . Diferindo da expressividade do elemento N na FSEA , na FSEM o Ca se configurou com"

  • Source
    • "Both denitrification and leaching depends on our simulated soil nitrate content and soil moisture. (3) Removal of nitrogen from soils and vegetation from LULUC disturbance including slash burning and decay from product pools (Fig. 7l) as also documented in earlier studies [Davidson et al., 2007; Herbert et al., 2003; Mathers et al., 2006; Schipper et al., 2007]. In summary, our model simulations suggest that large areas of secondary forests will not respond to CO 2 fertilization as strongly as they would when adequate nitrogen was available to meet the plant demands. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In the latest projections of future greenhouse gas emissions for the Intergovernmental Panel on Climate Change (IPCC), few Earth System Models included the effect of nitrogen limitation, a key process limiting forest regrowth. Few included forest management (wood harvest). We estimate the impacts of nitrogen limitation on the CO2 emissions from land use and land-use change (LULUC), including wood harvest, for the period 1900-2100. We use a land-surface model that includes a fully coupled carbon and nitrogen cycle, and accounts for forest regrowth processes following agricultural abandonment and wood harvest. Future projections are based on the four Representation Concentration Pathways used in the IPCC Fifth Assessment Report, and we account for uncertainty in future climate for each scenario based on ensembles of climate model outputs. Results show that excluding nitrogen limitation will underestimate global LULUC emissions by 34-52 PgC (20-30%) during the 20th century (range across three different historical LULUC reconstructions) and by 128-187 PgC (90-150%) during the 21st century (range across the four IPCC scenarios). The full range for estimated LULUC emissions during the 21st century including climate model uncertainty is 91 to 227 PgC (with nitrogen limitation included). The underestimation increases with time because: (1) Projected annual wood harvest rates from forests summed over the 21st century are 380-1080% higher compared to those of the 20th century, resulting in more regrowing secondary forests, (2) Nitrogen limitation reduces the CO2 fertilization effect on net primary production of regrowing secondary forests following wood harvest and agricultural abandonment, and (3) Nitrogen limitation effect is aggravated by the gradual loss of soil nitrogen from LULUC disturbance. Our study implies that: (1) Nitrogen limitation of CO2 uptake is substantial and sensitive to nitrogen inputs, (2) If LULUC emissions are larger than previously estimated in studies without nitrogen limitation, then meeting the same climate mitigation target would require an equivalent additional reduction of fossil fuel emissions, (3) The effectiveness of land-based mitigation strategies will critically depend on the interactions between nutrient limitations and secondary forests resulting from LULUC, and (4) It is important for terrestrial biosphere models to consider nitrogen constraint in estimates of the strength of future land carbon uptake.
    Global Biogeochemical Cycles 08/2015; DOI:10.1002/2015GB005086 · 3.97 Impact Factor
  • Source
    • "The karst region of Southwest China covers an area of 550,000 km 2 (Li et al., 2002), and is one of the main regions involved in the 'Grain-for-Green' project. These abandoned agricultural lands are experiencing a change from crop to forest or other secondary vegetation states, which are accompanied by changes in ecosystem structure, processes, and functions (Davidson et al., 2007; Zhang et al., 2010). Since the 1990s, government policies have forced farmers to abandon fields in parts of the karst area where erosion losses were especially high. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Vegetation succession enhances the accumulation of carbon in the soil. However, little is known about the mechanisms underlying soil organic carbon (SOC) accumulation in different vegetation types in the karst region of Southwest China. The goal of this study was to identify and prioritize the effects of environmental parameters, including soil physico-chemical properties, microbial biomass, enzyme activities, and litter characteristics, on SOC accumulation along a vegetation succession sere (grassland, shrubland, secondary forest, and primary forest) in the karst landscape of Southwest China. Relationships between these parameters and SOC were evaluated by redundancy analysis. The results showed that SOC accumulation was significantly different among vegetation types (P<0.01) and increased with vegetation succession (from 29.10g·kg(-1) in grassland to 73.92g·kg(-1) in primary forest). Soil biochemistry and physical characteristics significantly affected the accumulation of SOC. Soil microbial biomass showed a predominant effect on SOC in each of the four vegetation types. In addition, the soil physical property (especially the silt content) was another controlling factor in the early stages (grassland), and urease activity and saccharase activity were important controlling factors in the early-middle and middle-late stages, respectively. Litter characteristics only showed mild effects on SOC accumulation. Variation partitioning analysis showed that the contribution of sole main factors to SOC variation decreased, while the interaction effect among parameters increased along the succession gradient. Copyright © 2015 Elsevier B.V. All rights reserved.
    Science of The Total Environment 07/2015; 521:52-58. DOI:10.1016/j.scitotenv.2015.03.074 · 4.10 Impact Factor
Show more

Similar Publications