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Herberich, MM; Gayler, S; Anand, M; Tielborger, K.
(2020): Biomass-density relationships of plant communities deviate from the self-thinning rule due to age structure and abiotic stress
OIKOS. 2020; 129(9): 1393-1403. FullText FullText_BOKU

A pertinent debate in plant ecology centers around the generality of the self-thinning rule. However, studies focused on highly simplified settings such as even-aged monospecific populations or optimal conditions. This neglects the fact that most natural communities, to which the classical self-thinning slope is often applied, are age-structured, composed of multiple species and exposed to various types of abiotic stress. With the help of an individual-based model, we relax these simplified assumptions and systematically test for changes in the biomass-density relationships of uneven-aged, functionally diverse plant communities across a complete stress gradient, using excessive to insufficient soil water as a case study. We show that frequent recruitment, which resulted in an uneven-aged community, and stress intensity caused predictable changes in the entire biomass-density trajectory. Increasing stress resulted in steeper (more negative) slopes and increased the intercept in the classical self-thinning section irrespective of excessive or insufficient soil water as a stress type. Recruitment steepened the slope, too and enabled a novel section in the biomass-density trajectory. This novel section represented a quasi-steady state of the density-dependent dynamics of new generations which occurred locally within patches of recruitment. At the community level, the slope of the biomass-density relationship at quasi-steady state had a significantly flatter slope of -1.1 under optimal soil water conditions. Functional diversity showed little impact on density-dependent mortality. Namely, it resulted in an earlier onset of mortality but not in changes in the values of the slope and intercept. We conclude that the classical -3/2 slope is not useful to describe the biomass-density relationship in natural and semi-natural plant communities. The magnitude and direction of variation in the slope are related to the age-structure and abiotic stress intensity in the plant community.
Authors BOKU Wien:
Herberich Maximiliane

Find related publications in this database (Keywords)
abiotic stress
individual-based modelling
plant community

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