Patterns of Plant Biomass Allocation in Temperate Grasslands across a 2500-km Transect in Northern China

Wentao Luo,Mai-He Li,Xiaotao Lü,Zhuwen Xu,Yong Jiang,Edith Bai,Xue Wang,Xingguo Han,Ben Bond-Lamberty

doi:10.1371/journal.pone.0071749

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.

Highlights

Below-ground carbon (C) is the primary component of C stocks in grassland ecosystems, accounting for .80% of plant C stocks [1,2,3]
This paper only presents the results of mean annual precipitation (MAP) and mean annual temperature (MAT), since the effects of GSP and GST were not different from those of MAP and MAT
Indirect path coefficient means the indirect dependency of root/shoot ratios on certain climate factor and R is the correlation coefficient between the climate factors and the root/shoot ratios. doi:10.1371/journal.pone.0071749.t004

Summary

Introduction

Below-ground carbon (C) is the primary component of C stocks in grassland ecosystems, accounting for .80% of plant C stocks [1,2,3]. The below-ground system plays an important role in controlling terrestrial C sequestration and cycling. Compared to the above-ground system, knowledge of the belowground system is still limited [4]. Root/shoot ratios have been used to calibrate and estimate C storage from the more measurable aboveground biomass [5]. Root/shoot ratios have been incorporated into terrestrial ecosystem C modeling [6,7]. Quantifying root/shoot ratio and its relationships with climatic factors is important for improving our understanding of biomass allocation in terrestrial ecosystems, and critical for predicting global C sequestration and cycling under climate change. Few studies have investigated the influences of variations in climate on root/shoot ratios across geographical scales [8]

Methods

Results

Conclusion