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To identify the patterns of aboveground biomass (MA) and belowground biomass (MB) partitioning of a tall perennial herbal plant, Rheum tanguticum Maxim. ex Balf. (R. tanguticum), we determined MA, MB, total biomass (MT), and below- to aboveground biomass ratio (MB/MA) through three consecutive sampling campaigns during 2016–2018 on the Qinghai-Tibetan plateau. We then documented MA, MB, MT, and MB/MA, and their log–log relationship with environmental factors using data from 47 sites. MB/MA showed a significant negative relationship with mean annual precipitation (MAP) and altitude but a positive relationship with mean annual temperature (MAT), soil total nitrogen content (TN), and soil humidity (SH). While MT increased with altitude and decreased with MAT, TN, and SH, but the relationship between MAP and MT was not significant. Reduced major axis analysis revealed a slope of the log–log relationship between MA and MB to be 1.16, supporting an allometric partitioning pattern of R. tanguticum. Furthermore, the scaling exponent revealed different changes to different environmental factors. Specifically, scaling exponent was sensitive to the gradient of MAP and SH, but not to the gradient of altitude, MAT, or TN. This indicated that the scaling exponent was affected by water availability. [ABSTRACT FROM AUTHOR]

Biomass partitioning has been explored across various biomes. However, the strategies of allocation in plants still remain contentious. This study investigated allocation patterns of above- and belowground biomass at the community level, using biomass survey from the Tibetan Plateau. We explored above- and belowground biomass by conducting three consecutive sampling campaigns across shrub biomes on the northeast Tibetan Plateau during 2011–2013. We then documented the above-ground biomass (AGB), below-ground biomass (BGB) and root: shoot ratio (R/S) and the relationships between R/S and environment factors using data from 201 plots surveyed from 67 sites. We further examined relationships between above-ground and below-ground biomass across various shrub types. Our results indicated that the median values of AGB, BGB, and R/S in Tibetan shrub were 1102.55, 874.91 g m-2, and 0.85, respectively. R/S showed significant trend with mean annual precipitation (MAP), while decreased with mean annual temperature (MAT). Reduced major axis analysis indicated that the slope of the log-log relationship between above- and belowground biomass revealed a significant difference from 1.0 over space, supporting the optimal hypothesis. Interestingly, the slopes of the allometric relationship between log AGB and log BGB differed significantly between alpine and desert shrub. Our findings supported the optimal theory of above- and belowground biomass partitioning in Tibetan shrub, while the isometric hypothesis for alpine shrub at the community level. [ABSTRACT FROM AUTHOR]

The dried root of Rheum tanguticum plays an important role in formulations and prescriptions in traditional Chinese medicine and Kampo medicine. Due to over-exploitation, R. tanguticum resources have decreased sharply in recent years. The main objective of our investigation (a 3-year field experiment) was to explore the effect of different levels of phosphorus (superphosphate) and potassium (potassium sulfate) fertilizer on the biomass (root fresh weight, root increment, and root dry weight), yield, dry matter content, and anthraquinone content of this plant at different harvesting stages (green stage, growth stage, and wilting stage) under alpine conditions. The root fresh weight and root dry weight increased significantly at the wilting stage following treatment with 90 kg P 2 O 5 /ha (100% and 59%, respectively) in 2016 and 75 kg K 2 O/ha (43% and 41%, respectively) in 2015 compared to the control. The yield of root dry weight obtained from three-year-old R. tanguticum plants was 9200 kg/ha when 90 kg P 2 O 5 /ha of phosphorus fertilizer was applied, and 10,400 kg/ha when 75 kg K 2 O/ha of potassium fertilizer was applied. This yield reached a maximum at the wilting stage. The anthraquinone content of two-year-old R. tanguticum plants had already reached the standard level of the Chinese Pharmacopoeia ; however, three-year-old plants had double the anthraquinone content of two-year-old plants. Phosphorus and potassium fertilizers had no obvious influence on the anthraquinone content of R. tanguticum at the same harvesting stage. [ABSTRACT FROM AUTHOR]