Effects of long-term climatic variability and harvest frequency on grassland productivity across five ecoregions

Abstract

The degree to which grassland aboveground biomass responds to climatic variability (e.g. annual and growing season precipitation and temperature) as well as management practices (e.g. harvest frequency) has attracted considerable interest in ecological studies. This understanding is important for maintaining ecosystem stability and sustainable delivery of ecosystem services under climate change. Here, we analyzed grassland biomass observations in 31 study sites in 5 ecoregions (i.e. cold steppe, humid savanna, humid temperate, savanna, and temperate dry steppe) to examine the effects of growing season and annual climatic variability and harvest frequency on aboveground biomass productivity. Annual aboveground biomass productivity showed significant increasing trends in humid temperate and savanna, but the changes of annual biomass in cold steppe, humid savanna, and temperate dry steppe ecoregions were insignificant. Single harvest aboveground biomass in cold steppe, humid savanna and humid temperate ecoregions increased with higher growing season precipitation and temperature. Although annual precipitation had positive effects on annual biomass, we found growing season precipitation sum was a more important determinant in all ecoregions. Impacts of mean annual and growing season temperature on annual biomass in humid temperate were significantly positive, while significant adverse impacts of mean growing season temperature and mean annual temperature were found in savanna and temperate dry steppe ecoregions, respectively. Irrespective of climatic variability, annual biomass consistently increased with increasing harvest frequency across ecoregions. Our study found significant gains in grassland aboveground biomass across ecoregions with increased precipitation and harvest frequency, and significant loses of biomass in savanna and temperate ecoregions with increased temperature. Our results help improve the understanding of the differences in the responses of grassland productivity to climate variability and harvest frequency across various ecoregions, which is of importance to achieve sustainable grassland management in different geographical regions.