期刊
FRONTIERS IN FORESTS AND GLOBAL CHANGE
卷 4, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/ffgc.2021.686945
关键词
nitrogen limitation; litter decomposition; microbial model; carbon use efficiency; C/N ratio; microbial stoichiometry; extracellular enzymes
资金
- Swedish Research Council Vetenskapsradet [2020-03910]
- Swedish Research Council FORMAS [2015-00468]
- Vinnova [2015-00468] Funding Source: Vinnova
- Formas [2015-00468] Funding Source: Formas
- Swedish Research Council [2020-03910] Funding Source: Swedish Research Council
Microbial decomposers encounter challenges when feeding on nutrient-poor plant residues, adopting different strategies to adapt to nutrient limitation and affect the release of C and N from litter. Model studies show that different resource use modes may lead to similar litter decomposition trajectories, making it impossible to determine dominant modes through standard data.
Microbial decomposers face large stoichiometric imbalances when feeding on nutrient-poor plant residues. To meet the challenges of nutrient limitation, microorganisms might: (i) allocate less carbon (C) to growth vs. respiration or excretion (i.e., flexible C-use efficiency, CUE), (ii) produce extracellular enzymes to target compounds that supply the most limiting element, (iii) modify their cellular composition according to the external nutrient availability, and (iv) preferentially retain nutrients at senescence. These four resource use modes can have different consequences on the litter C and nitrogen (N) dynamics-modes that selectively remove C from the system can reduce C storage in soil, whereas modes that delay C mineralization and increase internal N recycling could promote storage of C and N. Since we do not know which modes are dominant in litter decomposers, we cannot predict the fate of C and N released from plant residues, in particular under conditions of microbial nutrient limitation. To address this question, we developed a process-based model of litter decomposition in which these four resource use modes were implemented. We then parameterized the model using similar to 80 litter decomposition datasets spanning a broad range of litter qualities. The calibrated model variants were able to capture most of the variability in litter C, N, and lignin fractions during decomposition regardless of which modes were included. This suggests that different modes can lead to similar litter decomposition trajectories (thanks to the multiple alternative resource acquisition pathways), and that identification of dominant modes is not possible using standard litter decomposition data (an equifinality problem). Our results thus point to the need of exploring microbial adaptations to nutrient limitation with empirical estimates of microbial traits and to develop models flexible enough to consider a range of hypothesized microbial responses.
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