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Abstract
The population and community level consequences of positive interactions between plants
remain poorly explored. In this study we incorporate positive resource-mediated interactions
in classic resource competition theory and investigate the main consequences for plant
population dynamics and species coexistence. We focus on plant communities for which
water infiltration rates exhibit positive dependency on plant biomass and where plant
responses can be improved by shading, particularly under water limiting conditions.
We show that the effects of these two resource-mediated positive interactions are
similar and additive. We predict that positive interactions shift the transition points
between different species compositions along environmental gradients and that realized
niche widths will expand or shrink. Furthermore, continuous transitions between different
community compositions can become discontinuous and bistability or tristability can
occur. Moreover, increased infiltration rates may give rise to a new potential coexistence
mechanism that we call controlled facilitation.
Copyright 2009 Elsevier Inc. All rights reserved.