Abstract
Dry woodlands frequently experience fire, and the heterogeneous spatial patterning of vegetation cover and fire behavior in these systems can lead to interspersed burned and unburned patches of different vegetation cover types. Biogeochemical processes may differ due to fire and vegetation cover influences on biotic and abiotic conditions, but these persistent influences of fire in the months or years following fire are not as well understood as the immediate impacts of fire. In particular, leaf litter decomposition, a process controlling nutrient availability and soil organic matter accumulation, is poorly understood in drylands but may be sensitive to vegetation cover and fire history. Decomposition is responsive to changes in abiotic drivers or interactions between abiotic conditions and biotic drivers, suggesting that decomposition rates may differ with vegetation cover and fire. The objective of this study was to assess the role of vegetation cover and fire on leaf litter decomposition in a semi-arid pinyon-juniper woodland in southern New Mexico, USA, where prescribed fire is used to combat increasing woody cover. A spatially heterogeneous prescribed burn led to closely co-located but discrete burned and unburned patches of all three dominant vegetation cover types (grass, shrub, tree). Decomposition rates of leaf litter from two species were measured in mesh litterbags deployed in factorial combination of the three vegetation cover types and two fire treatments (burned and unburned patches). For both litter types, decomposition was lower for unburned trees than for unburned grass or shrubs, perhaps due to greater soil–litter mixing and solar radiation away from tree canopies. Fire enhanced litter mass loss under trees, making decomposition rates similarly rapid in burned patches of all three vegetation cover types. Understanding decomposition dynamics in spatially heterogeneous vegetation cover of dry woodlands is critical for understanding biogeochemical process responses to fire in these systems.
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Acknowledgements
We thank the staff of the San Andres National Wildlife Refuge, in particular M. Weisenberger, for facilitating work at this site. We appreciate field and laboratory assistance from J. Fitzgerald, D. Hewins, and J. Smith. Funding for this work was from the International Arid Lands Consortium and the United States National Science Foundation (DEB 0815808 and 0953864). We appreciate constructive comments from two anonymous reviewers.
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Communicated by Paul M. Ramsay.
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Throop, H.L., Abu Salem, M. & Whitford, W.G. Fire enhances litter decomposition and reduces vegetation cover influences on decomposition in a dry woodland. Plant Ecol 218, 799–811 (2017). https://doi.org/10.1007/s11258-017-0730-1
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DOI: https://doi.org/10.1007/s11258-017-0730-1