Article

Stoichiometric controls of nitrogen and phosphorus cycling in decomposing beech leaf litter

Department of Chemical Ecology and Ecosystem Research, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
Ecology (Impact Factor: 5). 04/2012; 93(4):770-82. DOI: 10.2307/23213726
Source: PubMed

ABSTRACT Resource stoichiometry (C:N:P) is an important determinant of litter decomposition. However, the effect of elemental stoichiometry on the gross rates of microbial N and P cycling processes during litter decomposition is unknown. In a mesocosm experiment, beech (Fagus sylvatica L.) litter with natural differences in elemental stoichiometry (C:N:P) was incubated under constant environmental conditions. After three and six months, we measured various aspects of nitrogen and phosphorus cycling. We found that gross protein depolymerization, N mineralization (ammonification), and nitrification rates were negatively related to litter C:N. Rates of P mineralization were negatively correlated with litter C:P. The negative correlations with litter C:N were stronger for inorganic N cycling processes than for gross protein depolymerization, indicating that the effect of resource stoichiometry on intracellular processes was stronger than on processes catalyzed by extracellular enzymes. Consistent with this, extracellular protein depolymerization was mainly limited by substrate availability and less so by the amount of protease. Strong positive correlations between the interconnected N and P pools and the respective production and consumption processes pointed to feed-forward control of microbial litter N and P cycling. A negative relationship between litter C:N and phosphatase activity (and between litter C:P and protease activity) demonstrated that microbes tended to allocate carbon and nutrients in ample supply into the production of extracellular enzymes to mine for the nutrient that is more limiting. Overall, the study demonstrated a strong effect of litter stoichiometry (C:N:P) on gross processes of microbial N and P cycling in decomposing litter; mineralization of N and P were tightly coupled to assist in maintaining cellular homeostasis of litter microbial communities.

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Available from: Florian Hofhansl, Aug 10, 2015
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    • "This can explain the observed lower N/P ratio (19.1 in surface litter or 20.0 in buried litter) after 12 months of incubation. Our results suggest that the dynamics in litter stoichiometry during different incubation periods accounted for the patterns of N and P loss rates well (Mooshammer et al. 2012). In addition, the N/P ratio of simulated standing litter over 6 months of incubation Table 2 Pearson correlation analyses between 13 traits of green leaves and initial leaf litter and k values of litter decomposition for different litter positions, and Chi-square statistic and P values (n=51). "
    01/2015;
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    • "The positive effects of N deposition on primary productivity, however, are stoichiometrically governed by the relative availability of other elements, such as phosphorus (P) (Peñuelas et al. 2012; Vitousek et al. 2010), as well as ecosystem management practices, such as defoliation due to mowing (for hay production) or grazing in the grasslands (Gruner et al. 2008; Ziter and MacDougall 2012). Plant C:N:P stoichiometry plays an important role in mediating many ecological processes through its effects on plant growth and substrate quality for organisms at other trophic levels (Koerselman and Meuleman 1996; Mooshammer et al. 2011). Consequently , it is critical to understand the responses of both individual plant species and whole communities to increasing N availability in managed landscapes under an ecological stoichiometry framework. "
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    ABSTRACT: Abstract Background and aims Stoichiometric relations drive powerful constraints on many ecosystem processes. However, our understanding of the hierarchical responses of plant C:N:P stoichiometry at different levels of biological organization to global change factors remains limited. Methods we examined the plant C:N:P stoichiometric responses to N deposition and mowing (hay making) at both species- and community-level by carrying out a 4-year field experiment in the temperate steppe of northern China. Results Our results showed that N addition and mowing resulted in higher plant N concentrations, lower C:N, and higher N:P at both species- and community-level. Mowing had a limited negative influence on the effects of N addition. We observed divergent responses of both plant P concentrations and C:P to N addition at species-level and community-level: N addition led to higher plant P and lower C:P at species-level, but this effect was not observed at the community-level. Conclusions Our results indicate that stoichiometric responses at community-level to N addition and mowing diverge from more traditionally examined species-specific responses. Our results suggest that the hierarchical responses of plant stoichiometry to anthropogenic disturbance deserves more attention when we model the interactions of terrestrial ecosystem C, N, and P cycling under scenarios of increasing N availability concomitantly occurring with active land management.
    Plant and Soil 05/2014; 382(1-2). DOI:10.1007/s11104-014-2154-1 · 3.24 Impact Factor
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    • "To evaluate how differences in life-history traits between microbial groups drive community shifts in response to input stoichiometry, we run the model with two functional groups at initial litter C : N ratios from 15 to 95. One of the two Figure 2 Comparison of model output with data from a litter incubation study (Wanek et al. 2010; Mooshammer et al. 2012). Beech litter of four sampling sites in Austria differing in litter stoichiometry had been incubated for up to 65 weeks. "
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    ABSTRACT: Under the current paradigm, organic matter decomposition and nutrient cycling rates are a function of the imbalance between substrate and microbial biomass stoichiometry. Challenging this view, we demonstrate that in an individual-based model, microbial community dynamics alter relative C and N limitation during litter decomposition, leading to a system behaviour not predictable from stoichiometric theory alone. Rather, the dynamics of interacting functional groups lead to an adaptation at the community level, which accelerates nitrogen recycling in litter with high initial C : N ratios and thus alleviates microbial N limitation. This mechanism allows microbial decomposers to overcome large imbalances between resource and biomass stoichiometry without the need to decrease carbon use efficiency (CUE), which is in contrast to predictions of traditional stoichiometric mass balance equations. We conclude that identifying and implementing microbial community-driven mechanisms in biogeochemical models are necessary for accurately predicting terrestrial C fluxes in response to changing environmental conditions.
    Ecology Letters 03/2014; 17(6). DOI:10.1111/ele.12269 · 13.04 Impact Factor
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