Patterns of plant biomass allocation in temperate grasslands across a 2500-km transect in northern China

Abstract

Plant biomass allocation between below- and above-ground parts can actively adapt to the ambient growth conditions and is a key parameter for estimating terrestrial ecosystem carbon (C) stocks. To investigate how climatic variations affect patterns of plant biomass allocation, we sampled 548 plants belonging to four dominant genera (Stipa spp., Cleistogenes spp., Agropyron spp., and Leymus spp.) along a large-scale (2500 km) climatic gradient across the temperate grasslands from west to east in northern China. Our results showed that Leymus spp. had the lowest root/shoot ratios among the each genus. Root/shoot ratios of each genera were positively correlated with mean annual temperature (MAT), and negatively correlated with mean annual precipitation (MAP) across the transect. Temperature contributed more to the variation of root/shoot ratios than precipitation for Cleistogenes spp. (C4 plants), whereas precipitation exerted a stronger influence than temperature on their variations for the other three genera (C3 plants). From east to west, investment of C into the belowground parts increased as precipitation decreased while temperature increased. Such changes in biomass allocation patterns in response to climatic factors may alter the competition regimes among co-existing plants, resulting in changes in community composition, structure and ecosystem functions. Our results suggested that future climate change would have great impact on C allocation and storage, as well as C turnover in the grassland ecosystems in northern China.

Figure 1. Locations of the sampling sites along the transect across the temperate grasslands of northern China.

Figure 2. Root/shoot ratios (mean ±1 SE) of four grasses genera (Stipa, Cleistogenes, Agropyron, and Leymus).

Bars with dissimilar letters denote signiffcant difference (p<0.01).

Figure 3. Allometric relationship between root biomass and shoot biomass.

Stipa spp. (A), Cleistogenes spp. (B), Agropyron spp. (C), and Leymus spp. (D). Red lines are the standardized major axis regression curves (for a summary of regression statistics, see Table 5). Green lines are isometric lines with slope equal to 1 and y-intercept equal to that of the corresponding red lines.