Interannual variation in land-use intensity enhances grassland multidiversity

Abstract

Although temporal heterogeneity is a well-accepted driver of biodiversity, effects of interannual variation in land-use intensity (LUI) have not been addressed yet. Additionally, responses to land use can differ greatly among different organisms; therefore, overall effects of land-use on total local biodiversity are hardly known. To test for effects of LUI (quantified as the combined intensity of fertilization, grazing, and mowing) and interannual variation in LUI (SD in LUI across time), we introduce a unique measure of whole-ecosystem biodiversity, multidiversity. This synthesizes individual diversity measures across up to 49 taxonomic groups of plants, animals, fungi, and bacteria from 150 grasslands. Multidiversity declined with increasing LUI among grasslands, particularly for rarer species and aboveground organisms, whereas common species and belowground groups were less sensitive. However, a high level of interannual variation in LUI increased overall multidiversity at low LUI and was even more beneficial for rarer species because it slowed the rate at which the multidiversity of rare species declined with increasing LUI. In more intensively managed grasslands, the diversity of rarer species was, on average, 18% of the maximum diversity across all grasslands when LUI was static over time but increased to 31% of the maximum when LUI changed maximally over time. In addition to decreasing overall LUI, we suggest varying LUI across years as a complementary strategy to promote biodiversity conservation.

Grassland management intensification weakens the associations among the diversities of multiple plant and animal taxa

“…To make all plots comparable through a common land-use metric and due to high correlation between them, the three land-use factors were aggregated into a compound land-use intensity index (LUI; Blu¨thgen et al 2012) that summed the three land-use components, each standardized by its mean value within each region (Appendix A). This index has been found to be a better predictor of biodiversity responses in these grasslands than its individual components (Blu¨thgen et al 2012, Allan et al 2014). …”

“…We then divided grasslands into smaller groups based upon their land-use intensity and examined how land-use intensity altered these relationships. Finally, we assessed the correlation of the biodiversity of each taxa with a new metric of total ecosystem diversity, multidiversity (Allan et al 2014).…”

Ecosystem structure, function and composition in rangelands are negatively affected by livestock grazing

“…However, the relatively modest effects we found can be explained by the weak influence of grazing on the richness component of the compositional metric, probably due to idiosyncratic responses of many different taxa to grazing. For example, intensive grazing associated with agricultural activities has been shown to substantially reduce richness of plants, lichens, and insects (e.g., Orthoptera and Lepidoptera), but not Diptera, arbuscular mycorrhizal fungi or bats (Allan et al 2014). Grazing-induced increases in ants of the dominant Dolichorine group could buffer reductions in cryptic, grazing-sensitive species, resulting in no net change in richness (Bromham et al 1999, Seymour and Dean 1999, Nash et al 2004.…”

Consistent drivers of plant biodiversity across managed ecosystems

“…Managed ecosystems are, however, subject to spatio-temporal changes in species numbers [8], especially if management intensity varies over time [9]. For example, cessation of management such as fertilizer or pesticide input may lead to increases in plant biodiversity from species-poor states [10].…”