Responses to changes in precipitation of plant species vary by functional groups on understories of temperate forests in central Japan

Abstract

Climate change has one of the most dramatic impacts on plant species diversity at the global scale. However, compared to global warming, there are few reports of the effects of changes in long-term precipitation patterns on plant community diversity in areas other than moisture-limited areas, for example temperate areas. In temperate forests, understory plant communities constitute a large proportion of plant diversity. It is crucial to investigate effects of change in long-term precipitation patterns and the other important environmental changes on plant species composition of understories in temperate forests for making the conservation strategy. The important changes that may have particularly affected plant composition in recent years include the followings; temperature rise, increase of large herbivores, change of habitat area, and changes in the cover of canopy and understory-abundant species according to the land use change. Vulnerability to the above environmental changes may be higher for species groups that are less adapted to their current habitat and have shrinking population sizes (e.g., grassland species on understories in abandoned secondary forests). The aim of this study was to estimate the effects of precipitation and the above-mentioned factors on changes in cover of individual species on understories in temperate forests from the 1980s to the 2000s. In the analysis, we took into account the differences in the functional groups of the species (grassland herbaceous species, forest herbaceous species, and woody species). Grassland herbaceous species responded more sensitively to precipitation, temperature, cover of dwarf bamboo, and deer habitat use than other functional groups. In the 1980s, the cover of grassland herbaceous species tended to be higher in places with lower precipitation, higher temperatures, and lower cover of dwarf bamboo and canopy, in association with climatic conditions and past land-use history. Over the last 20 years, increased precipitation and deer habitat use had particularly strong effects on the decline of grassland herbaceous species. This study found that precipitation variability is becoming a driving factor for biodiversity change through decline of vulnerable species groups in temperate areas. We should continue to monitor the precipitation effects on the ecosystems.