Few effects of plant functional group identity on ecosystem properties in an annual desert community
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Desertification is leading to large-scale changes in vegetation structure resulting from increased grazing pressure and drought which may, in turn, have further effects on ecosystem functioning. We examine how the changing functional group identity of plants may influence a range of biotic and abiotic ecosystem properties. To explore this question, we use a functional group removal experiment in which single functional groups (graminoids, legumes and non-leguminous forbs) were experimentally removed from an annual plant community in the Negev Desert, Israel. We conducted the experiment in both a high- and a low-resource environment to determine if identity effects are context dependent. We found full biomass compensation by remaining functional groups for the removal of any functional group, often with more, rather than larger, individuals comprising the compensatory growth. We also found few effects overall of functional group identity on ecosystem properties, with some dependence on environmental context. We found that the functional group with the largest proportional biomass often, but not always, had the largest effect on ecosystem properties. We contrast these results with those from previous removal experiments, the majority of which have been conducted in perennial ecosystems, and hypothesize that the transient nature of annual communities leads to fewer plant–soil interactions in the long term, and as a result fewer effects on ecosystem properties.
KeywordsRemoval experiment Functional group Mass ratio hypothesis Biomass compensation Ecosystem properties
This research was supported by the Natural Sciences and Engineering Research Council of Canada (Discovery Grant to R.T. and scholarship to J.R.M.), Sigma Xi, and Western Ag Innovations. Many thanks to the staff at the Blaustein Institute for Desert Research for logistical and other support. The authors are grateful to Lusine Ghazaryan, Hadas Hawlena, Valeria Hochman and Tania Acuna for help in the field and A. Darrouzet-Nardi, J.C. Cahill and an anonymous reviewer for comments on an earlier version of this manuscript. This is publication #915 of the Mitrani Department of Desert Ecology.
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