Aim Climate-driven changes affecting ecosystem primary production have been well documented for many vegetation types, while the effects of climate on plant populations remains unclear. Herein, we address the relationships between climatic variables and shoot density, reproductive allocation and shoot biomass in Leymus chinensis on a large-scale climatic gradient in 2000.
Location Nine sites experiencing similar light regimes, but differing in longitude, precipitation and altitude were selected on the North-east China Transect (NECT) from 115° to 124°E, around a latitude of 43.5°N.
Methods Densities of total, vegetative and reproductive shoots and of shoot biomass were measured twice over the growing season in each site. Climatic data were taken from the climate database of the Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences and from the local weather stations throughout the NECT.
Results Densities of total, vegetative and reproductive shoots increased significantly from the west to the east and from dry to moist along the NECT, and were strongly correlated with annual precipitation (r2 = 0.934, 0.943 and 0.863, respectively) and an aridity index (r2 = 0.809, 0.816 and 0.744, respectively). The average total shoot density at the east end (470/m2) was about three times that at the west (160/m2). Reproductive allocation and shoot biomass for both vegetative and reproductive shoots increased with precipitation and declined with the aridity index along the NECT. There were positive correlations between shoot biomass and annual precipitation for vegetative shoots (P < 0.05, R2 = 0.604) and March precipitation for reproductive shoots (P < 0.05, R2 = 0.533), respectively.
Main conclusions These findings suggest that L. chinensis adjusts to decreasing precipitation/increasing aridity by alterations in shoot density, reproductive allocation and shoot biomass along the drought gradient of the NECT.