High Below-Ground Productivity Allocation of Alpine Grasslands on the Northern Tibet

Ben Niu; Chaoxu Zeng; Xianzhou Zhang; Yongtao He; Peili Shi; Yuan Tian; Yunfei Feng; Meng Li; Zhipeng Wang; Xiangtao Wang; Yanan Cao

doi:10.3390/plants8120535

High Below-Ground Productivity Allocation of Alpine Grasslands on the Northern Tibet

Plants (Basel). 2019 Nov 22;8(12):535. doi: 10.3390/plants8120535.

Authors

Ben Niu¹, Chaoxu Zeng^{1

2}, Xianzhou Zhang¹, Yongtao He¹, Peili Shi¹, Yuan Tian^{1

2}, Yunfei Feng³, Meng Li^{1

2}, Zhipeng Wang^{1

2}, Xiangtao Wang^{1

2}, Yanan Cao^{1

2}

Affiliations

¹ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
² University of Chinese Academy of Sciences, Beijing 100049, China.
³ Department of Resource Management, Tangshan Normal University, Tangshan 063000, China.

Abstract

The allocation of net primary production (NPP) between above- and belowground components is a key step of ecosystem material cycling and energy flows, which determines many critical parameters, e.g., the fraction of below ground NPP (BNPP) to NPP (f_BNPP) and root turnover rates (RTR), in vegetation models. However, direct NPP estimation and partition are scarcely based on field measurements of biomass dynamics in the alpine grasslands on the Northern Tibetan Plateau (NTP). Consequently, these parameters are unverifiable and controversial. Here, we measured above- and belowground biomass dynamics (monthly from May to September each year from 2013 to 2015) to estimate NPP dynamics and allocations in four typical alpine grassland ecosystems, i.e., an alpine meadow, alpine meadow steppe, alpine steppe and alpine desert steppe. We found that NPP and its components, above and below ground NPP (ANPP and BNPP), increased significantly from west to east on the NTP, and ANPP was mainly affected by temperature while BNPP and NPP were mainly affected by precipitation. The bulk of BNPP was generally concentrated in the top 10 cm soil layers in all four alpine grasslands (76.1% ± 9.1%, mean ± SD). Our results showed that f_BNPP was significantly different among these four alpine grasslands, with its means in alpine meadow (0.93), alpine desert steppe (0.92) being larger than that in the alpine meadow steppe (0.76) and alpine steppe (0.77). Both temperature and precipitation had significant and positive effects on the f_BNPP, while their interaction effects were significantly opposite. RTR decreased with increasing precipitation, but increased with increasing temperature across this ecoregion. Our study illustrated that alpine grasslands on the NTP, especially in the alpine meadow and alpine desert steppe, partitioned an unexpected and greater NPP to below ground than most historical reports across global grasslands, indicating a more critical role of the root carbon pool in carbon cycling in alpine grasslands on the NTP.

Keywords: Net primary productivity; alpine grasslands; below ground biomass; model parameters; partitioning; root turnover rate.