Temporal changes in randomness of bird communities across Central Europe

• Published in: PloS one Vol. 9; no. 11; p. e112347
• Main Authors: Renner, Swen C, Gossner, Martin M, Kahl, Tiemo, Kalko, Elisabeth K V, Weisser, Wolfgang W, Fischer, Markus, Allan, Eric
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 11.11.2014; Public Library of Science (PLoS)
• Subjects: Analysis; Animal behavior; Animal populations; Animals; Biodiversity; Biology and Life Sciences; Birds; Climate change; Communities; Community composition; Data processing; Ecology; Ecology and Environmental Sciences; Ecosystem; Ecosystem biology; Ecosystems; Europe; Forest communities; Forest management; Forests; Habitats; Land use; Life sciences; Plant communities; Plant populations; Plant sciences; Population Dynamics; Random processes; Randomness; Regression analysis; Spatial analysis; Spatial distribution; Species composition; Stochastic models; Stochastic processes; Stochasticity; Studies; Sustainable forestry; Temporal variations; Trees; Variation; Europe; Switzerland; Central Europe; Germany
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0112347

Many studies have examined whether communities are structured by random or deterministic processes, and both are likely to play a role, but relatively few studies have attempted to quantify the degree of randomness in species composition. We quantified, for the first time, the degree of randomness in forest bird communities based on an analysis of spatial autocorrelation in three regions of Germany. The compositional dissimilarity between pairs of forest patches was regressed against the distance between them. We then calculated the y-intercept of the curve, i.e. the 'nugget', which represents the compositional dissimilarity at zero spatial distance. We therefore assume, following similar work on plant communities, that this represents the degree of randomness in species composition. We then analysed how the degree of randomness in community composition varied over time and with forest management intensity, which we expected to reduce the importance of random processes by increasing the strength of environmental drivers. We found that a high portion of the bird community composition could be explained by chance (overall mean of 0.63), implying that most of the variation in local bird community composition is driven by stochastic processes. Forest management intensity did not consistently affect the mean degree of randomness in community composition, perhaps because the bird communities were relatively insensitive to management intensity. We found a high temporal variation in the degree of randomness, which may indicate temporal variation in assembly processes and in the importance of key environmental drivers. We conclude that the degree of randomness in community composition should be considered in bird community studies, and the high values we find may indicate that bird community composition is relatively hard to predict at the regional scale.