Responses of biomass allocation across two vegetation types to climate fluctuations in the northern Qinghai–Tibet Plateau

Abstract

The Qinghai–Tibet Plateau (QTP) is particularly sensitive to global climate change, especially to elevated temperatures, when compared with other ecosystems. However, few studies use long‐term field measurements to explore the interannual variations in plant biomass under climate fluctuations. Here, we examine the interannual variations of plant biomass within two vegetation types (alpine meadow and alpine shrub) during 2008–2017 and their relationships with climate variables. The following results were obtained. The aboveground biomass (AGB) and belowground biomass (BGB) response differently to climate fluctuations, the AGB in KPM was dominated by mean annual precipitation (MAP), whereas the AGB in PFS was controlled by mean annual air temperature (MAT). However, the BGB of both KPM and PFS was only weakly affected by climate variables, suggesting that the BGB in alpine ecosystems may remain as a stable carbon stock even under future global climate change. Furthermore, the AGB in PFS was significantly higher than KPM, while the BGB and R/S in KPM were significantly higher than PFS, reflecting the KPM be more likely to allocate more photosynthates to roots. Interestingly, the proportion of 0–10 cm root biomass increased in KPM and PFS, whereas the other proportions both decreased, reflecting a shift in biomass toward the surface layer. Our results could provide a new sight for the prediction how alpine ecosystem response to future climate change.

Moderate grazing promotes the root biomass in Kobresia meadow on the northern Qinghai–Tibet Plateau

“…Thus, there is a sense of urgency to determine a suitable stocking rate in the alpine grassland for restoring degraded grassland and improving livestock production both at the local and at the landscape scale (Barcella, Filipponi, & Assini, ; Metera, Sakowski, Słoniewski, & Romanowicz, ). In this study, we found that the maximum value of BGB occurred in moderate levels of grazing disturbance (i.e., 7.5 sheep/ha), suggesting that such stocking rates may be an optimal grassland management strategy for the alpine meadow in terms of root production, especially considering the BGB almost accounts for more than 80% biomass of plants (Dai, Guo, Du, Ke, et al, ; Dai, Guo, Zhang, et al, ; Dai, Ke, et al, ), which could provide new insight for local people and policy‐makers in government. However, it should be noted that the species richness shows the lowest value in MG in spite of the BGB peaked in MG.…”

“…The region has a characteristic plateau continental monsoon climate, with a mean annual air temperature of −1.7°C, and maximum and minimum air temperatures in July (9.8°C) and January (−14.80°C), respectively. The average annual precipitation is approximately 618 mm, with almost 80% falling in the growing season (i.e., from early May to late September; Dai, Guo, Du, Ke, et al, ; Dai, Guo, Du, Zhang, et al, ; Dai, Guo, Zhang, et al, ; Dai, Ke, et al, ). The soil is classified as Mat cryo‐sod soil on the basis of the Chinese National Soil Survey and Classification System (Institute of Soil Science, CAS, 2001).…”

“…The Qinghai–Tibetan Plateau (QTP) is the main region of alpine meadow and alpine steppe, with an area of approximately 2.5 million km 2 of alpine grassland representing one of the world's largest areas of alpine grassland (Dai, Guo, Du, Ke, et al, ; Dai, Guo, Zhang, et al, ; Dai, Ke, et al, ; Lu et al, ; Wesche et al, ). Most importantly, the QTP is the one of the most important natural pastures in China and has provided the main pastures for Tibetan communities for many years (Klein, Harte, & Zhao, ).…”

Biomass allocation and productivity–richness relationship across four grassland types at the Qinghai Plateau

“…For instance, in the desert ecosystem, the plant in low precipitation condition could allocate less biomass to the leaf to avoid more moisture loss via evapotranspiration and allocate more biomass to the root to obtain more moisture and soil nutrients from a greater volume of soil (Fan et al, ; Wu et al, ). However, in the alpine ecosystem with low temperature and short growth season, the nutrient content was less as the soil nutrient supplement of the alpine ecosystems is strongly determined by nutrient mineralization (Dai, Ke, Du, Zhang, et al, ; Dai, Ke, Guo, et al, ).Therefore, there may exist trade‐off between belowground organ to capture soil nutrient and aboveground organ to capture more carbon, according to the carbon is fixed by leaves and the water or mineral nutrients were absorbed by root (McConnaughay & Coleman, ); that is, the plant might choose to obtain more biomass to plant organs that associated with the acquisition of that resource at the cost of reducing the structures biomass associated with acquisition of another resource. Moreover, this evidence was supported by the seasonal dynamics of AGB and BGB in the alpine ecosystem in a previous study (Dai, Guo, Du, et al, ).…”

Nitrogen controls the net primary production of an alpine Kobresia meadow in the northern Qinghai‐Tibet Plateau

“…Although ANPP was positively related to precipitation at large scales (Sala, Parton, Joyce, & Lauenroth, ), caution should be used when considering the differences in climate conditions of individual sites. For instance, the plants in our alpine ecosystem were limited by the low temperature and short growing season (Dai, Ke, et al, ). Moreover, the soil moisture was relative abundance relatively abundant during the growing season due to the replenishment from precipitation and thawing of seasonally frozen soil (Dai et al, ).…”