Hong Jiangtao, Ma Xingxing, Wang Xiaodan
Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China; University of Chinese Academy of Sciences Beijing 100049 China.
Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China.
Ecol Evol. 2016 Mar 4;6(8):2325-32. doi: 10.1002/ece3.2059. eCollection 2016 Apr.
Grazing and fencing are two important factors that influence productivity and biomass allocation in alpine grasslands. The relationship between root (R) and shoot (S) biomass and the root:shoot ratio (R/S) are critical parameters for estimating the terrestrial carbon stocks and biomass allocation mechanism responses to human activities. Previous studies have often used the belowground:aboveground biomass ratio (M b/M a) to replace the R/S in alpine ecosystems. However, these studies may have neglected the leaf meristem biomass, which belongs to the shoot but occurs below the soil surface, leading to a significant overestimation of the R/S ratio. We conducted a comparative study to explore the differences between the R/S and M b/M a at both the species (Stipa purpurea, Carex moorcroftii, and Artemisia nanschanica) and community levels on a Tibetan alpine grassland with grazing and fencing management blocks. The results revealed that the use of the M b/M a to express the R/S appeared to overestimate the actual value of the R/S, both at species and community levels. For S. purpurea, the M b/M a was three times higher than the R/S. The M b/M a was approximately two times higher than the R/S for the species of C. moorcroftii and A. nanschanica and at the community level. The relationships between the R-S and M b-M a exhibited different slopes for the alpine plants across all the management practices. Compared to the fenced grasslands, the plants in the grazing blocks not only allocated more biomass to the roots but also to the leaf meristems. The present study highlights the contribution of leaf meristems to the accurate assessment of shoot and belowground biomasses. The R/S and M b/M a should be cautiously used in combination in the future research. The understanding of the distinction between the R-S and M b-M a may help to improve the biomass allocation mechanism response to human disturbances in an alpine area.
放牧和围栏是影响高寒草原生产力和生物量分配的两个重要因素。根系（R）与地上部分（S）生物量之间的关系以及根冠比（R/S）是估算陆地碳储量和生物量分配机制对人类活动响应的关键参数。以往研究在高寒生态系统中常使用地下生物量与地上生物量之比（Mb/Ma）来替代R/S。然而，这些研究可能忽略了属于地上部分但位于土壤表层以下的叶分生组织生物量，导致对R/S比值的显著高估。我们进行了一项比较研究，以探讨在有放牧和围栏管理分区的青藏高原高寒草原上，物种（紫花针茅、高山嵩草和南祁连蒿）和群落水平上R/S与Mb/Ma之间的差异。结果表明，无论是在物种水平还是群落水平上，用Mb/Ma来表示R/S似乎都高估了R/S的实际值。对于紫花针茅，Mb/Ma比R/S高3倍。对于高山嵩草和南祁连蒿以及群落水平，Mb/Ma比R/S大约高2倍。在所有管理措施下，高寒植物的R-S与Mb-Ma之间的关系呈现出不同的斜率。与围栏草地相比，放牧分区的植物不仅将更多生物量分配到根系，还分配到叶分生组织。本研究突出了叶分生组织对准确评估地上和地下生物量的贡献。在未来研究中应谨慎联合使用R/S和Mb/Ma。理解R-S与Mb-Ma之间的区别可能有助于改进高寒地区生物量分配机制对人为干扰的响应。
