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
    • "Additionally, unfavorable frame conditions like low return yields, poor technical support, inadequate development policies, and unsecure property rights make the production systems unsustainable. In the end, high fence restoration costs and forage scarcity on the plots force farmers to simply abandon their pastures because further restoration investment is economically not justifiable, anymore (Buschbacher et al., 1988; Müller et al., 2004; Davidson et al., 2007; Dias-Filho, 2011). Besides frequent weeding, the traditional way to increase forage quantity and quality on tropical pastures is to apply Pfertilizer for forage grasses or to plant multi-purpose forage legumes (Gutteridge and Shelton, 1994; Skerman et al., 1988; Cook et al., 2005; Hohnwald et al., 2005). "
    [Show abstract] [Hide abstract]
    ABSTRACT: In northeastern Pará, smallholder agriculture systems are still based on secondary forest fallows, nationally called "capoeira", presumed to contain a remarkable amount of underutilized valuable woody species, for instance as supplementary forage for cattle. We tested five promising capoeira species, namely Phenakospermum guyannense, Cecropia palmata, Attalea maripa, Inga edulis, and Abarema jupunba by comparing its relative palatability- i.e. the palatability differences between the tested species and the reference forage legumes, forage grass, and between the other tested species-, heights, biomass production, and main nutritive values with the well-known tropical forage legumes Cratylia argentea and Flemingia macrophylla. Additionally, the locally common domesticated species Tithonia diversifolia, Mangifera indica, and Racosperma mangium were also included in the trial, all implemented in a randomized block design on a Brachiaria-pasture (n=2000 saplings, 8 replication blocks). After two years of establishment, four steers with an average body mass of 506 kg browsed the trial (2 AU/ha). The relative palatability testing showed that A. jupunba, M. indica and also surprisingly R. mangium (all >20% of its respective total biomass) matched the consumed biomass of F. macrophylla., while C. palmata (>60%) even surpassed very palatable C. argentea. R. mangium also had the highest biomass production, while the other species showed just regular growth and establishing rates. Protein contents of all species were above 6%, most of them higher than 10% and in the case of T. diversifolia even above 20%. Thus, all tested species almost reached the quality of the reference legumes. However, as plant secondary compounds were not regarded in this trial, recommendations as supplementary forage plants can only be given with reservations. The results suggest that smallholders possess cheap forage supplement alternatives on their farms and even on their pasture plots, which simply have to be tolerated by just pruning them into accessible heights for animals. However, sapling transplantation from shady capoeiras on old slightly degraded pastures for biomass enrichment cannot be recommended.
    Full-text · Article · Feb 2016 · Agriculture Ecosystems & Environment
  • 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"

    Full-text · Article · Sep 2015
  • 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.
    Full-text · Article · Aug 2015 · Global Biogeochemical Cycles
Show more