Background and aims: We determined the relationship between site N supply and decomposition rates with respect to controls exerted by environment, litter chemistry, and fungal colonization. Methods: Two reciprocal transplant decomposition experiments were established, one in each of two long-term experiments in oak woodlands in Minnesota, USA: a fire frequency/vegetation gradient, along which soil N availability varies markedly, and a long-term N fertilization experiment. Both experiments used native Quercus ellipsoidalis E.J. Hill and Andropogon gerardii Vitman leaf litter and either root litter or wooden dowels. Results: Leaf litter decay rates generally increased with soil N availability in both experiments while belowground litter decayed more slowly with increasing soil N. Litter chemistry differed among litter types, and these differences had significant effects on belowground (but not aboveground) decay rates and on aboveground litter N dynamics during decomposition. Fungal colonization of detritus was positively correlated with soil fertility and decay rates. Conclusions: Higher soil fertility associated with low fire frequency was associated with greater leaf litter production, higher rates of fungal colonization of detritus, more rapid leaf litter decomposition rates, and greater N release in the root litter, all of which likely enhance soil fertility. During decomposition, both greater mass loss and litter N release provide mechanisms through which the plant and decomposer communities provide positive feedbacks to soil fertility as ultimately driven by decreasing fire frequency in N-limited soils and vice versa.
Bibliographical noteFunding Information:
Acknowledgments We are grateful to Chris Bolton and Bill Wroblewski for their help in sample collection and processing and to Cathleen McFadden at the University of Nebraska for litter chemistry analyses. Rebecca Montgomery, Deborah Allan, and two anonymous reviewers provided helpful comments on previous versions of the manuscript. Funding was provided though the National Science Foundation-funded Cedar Creek Long Term Ecological Research program (DEB-0080382, DEB-0620652). The fungal molecular work was funded by a SUNY Brockport Scholarly Incentive Award to M. Norris.
- Fertilization gradient
- Fire frequency gradient
- Fungal colonization
- Soil N availability
- Soil fertility