Drought inhibits synergistic interactions of native and exotic litter mixtures during decomposition in temperate grasslands
Background and aims
Leaf litters commonly interact during decomposition in ways that can synergistically increases rates of decay. These interactions have been linked to moisture availability, suggesting that drought could slow decomposition rates by disrupting litter interactions. Slowed decomposition may reduce competitive ability of exotic species that exploit rapid decomposition rates as part of niche construction mechanisms. Here, we evaluated the impacts of drought on interactions between native and exotic species’ litter decomposition.
We considered litter mixtures of Lupinus polyphyllus (exotic N-fixing forb), Trifolium pratense (native N-fixing forb), Senecio inaequidens (exotic non-N-fixing forb), and Senecio jacobaea (native non-N-fixing forb) with the native grass Alopecurus pratensis and evaluated the difference between the observed rate of decay and the one expected based on species decomposing in monocultures. Litters were deployed in Belgium and Germany and exposed to a 56 day drought, which resembled local millennium drought (statistical recurrence of duration in local precipitation series >1000 years).
Litter interactions reduced mass remaining by 81% in Belgium and 15% in Germany, averaged across mixtures. Similarly, litter interactions reduced N remaining by 93% in Belgium and 14% in Germany. Drought consistently removed these interactions and resulted in additive litter decay. Litters of native and exotic species did not differ in their response to drought.
These findings support moisture availability as a key regulator of interactions between litters during decomposition. Thus, increasing frequency of drought may slow nutrient cycling to a greater extent than previously thought.
KeywordsNon-additive effect Mixture Climate change Precipitation Litter Invasion Invasive
We would like to thank members of the SIGNAL collaboration (http://www.bayceer.uni-bayreuth.de/signal/) for use of their Belgian and German sites and Geert Bernaerts for assistance with environmental monitoring at the Belgian site. SIGNAL was funded by the ERA-Net BiodivERsA, with the national funders Belgian Science Policy Office (BELSPO), Bulgarian Science Fund (BNSF), Ministère de l’Écologie, du Développement durable et de l’Énergie de la République Française (MEDDE) and German Federal Ministry of Education and Research (BMBF), as part of the 2011 − 2012 BiodivERsA call for research proposals. MJS was advised by Jeffrey S. Dukes and supported by USDA Agro-ecosystem Services National Needs Fellowship and International Research Travel Allowance. We would also like to thank two anonymous reviewers for their role in improving the manuscript.
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