Different aged stands of a riparian foundation tree species in a chronosequence support different arthropod communities: Biodiversity and restoration implications

We addressed the hypothesis that landscape heterogeneity, in the form of a chronosequence, affects biodiversity. It is widely accepted that landscape heterogeneity leads to increased biodiversity. Heterogeneous landscapes offer a wider variety of microhabitats, microclimates, refugia, resources and thus niches to support more diverse communities than do homogenous landscapes. We examined the specific hypothesis that the arthropod communities differ significantly between stands in a chronosequence of trees. The variation in tree age in a chronosequence inherently increases landscape heterogeneity for arthropods, supporting a more diverse overall arthropod community. We tested this by nondestructively sampling the arboreal arthropod communities in several different aged stands (seven, five and two years old) of Fremont cottonwood (Populus fremontii) planted for habitat restoration. We found that the arthropod communities were significantly different in 1) community composition, 2) species richness, 3) species diversity, 4) evenness, and 5) indicator species. These clear differences indicate that increased landscape heterogeneity leads to increased biodiversity, both directly through supporting increased arthropod diversity, and indirectly by supporting this prey resource important for other vertebrate animals. While the concept of increased heterogeneity supporting increased biodiversity is not novel, finding this link between an arthropod community and a chronosequence of a long-lived foundation riparian tree species is. Because a landscape of mixed stands supports greater biodiversity than monocultures of equal-aged stands, by incorporating varied stand age into restoration designs managers can effectively increase the biodiversity of the dependent community. This may be especially important in threatened ecosystems like the riparian Southwest.