Effect of altitude and soil properties on biomass and plant richness in the grasslands of Tibet, China, and Manang District, Nepal

Abstract

Citation: Bhandari, J., and Y. Zhang. 2019. Effect of altitude and soil properties on biomass and plant richness in the grasslands of Tibet, China, and Manang District, Nepal.Abstract. A positive relationship between plant species richness and biomass has often documented in temperate grassland systems but is still largely lacking in the Himalayan region. Considering altitude and soil properties as major factors influencing species richness and biomass in the Himalayan grasslands, we tested the hypothesis that peak aboveground biomass and species richness increase with higher levels of soil nutrients and decrease with altitude. Our study was conducted in the grasslands of Tibet, China, and Manang District, Nepal, which represent, respectively, the northern and southern slopes of the central Himalayan grasslands. During the growing seasons, we measured vegetation aboveground biomass and soil properties along an altitudinal gradient on the northern slope in 2011 and 2012, and on the grasslands of the southern slope in 2017. Data were analyzed with a Spearman correlation analysis, classification and regression tree model, and the structural equation modeling (SEM) to identify the key factors determining aboveground biomass and species richness. The results demonstrated that aboveground biomass and species richness on the southern slope were significantly greater at the lowest altitude zone compared to middle and higher zones, whereas on the northern slope, aboveground biomass and species richness were not significantly different at three altitudinal zones. There was a significant positive correlation between aboveground biomass and species richness on both northern and southern slopes. However, the slope was found higher in grasslands of southern slope compared to the grasslands of northern slope. Classification and regression tree analysis and SEM indicated that altitude is most closely associated with large-scale variations in aboveground biomass and species richness. The Spearman correlation analysis revealed that altitude and soil pH were negatively related to aboveground biomass in these grasslands. This study demonstrates that on northern and southern slopes of the Himalayan Range, a positive relation between plant species richness and biomass is determined more by altitude than soil nutrients.

Simulating the spatiotemporal variations in aboveground biomass in Inner Mongolian grasslands under environmental changes

“…Here, extrapolations of such a relationship between CO 2 concentration and AGB to larger extents of CO 2 concentrations can lead to substantial uncertainties in estimations of AGB. Second, the local soil (Fay et al, 2012) and climatic (Brookshire and Weaver, 2015) factors can modify the actual CO 2 enrichment effect on AGB, which may also result in large uncertainties in the quantified AGB. For example, any stimulation in plant growth is constrained by the availability of other resources required by plant growth (Reyes-Fox et al, 2014) such as soil water availability (Brookshire and Weaver, 2015).…”

“…Second, the local soil (Fay et al, 2012) and climatic (Brookshire and Weaver, 2015) factors can modify the actual CO 2 enrichment effect on AGB, which may also result in large uncertainties in the quantified AGB. For example, any stimulation in plant growth is constrained by the availability of other resources required by plant growth (Reyes-Fox et al, 2014) such as soil water availability (Brookshire and Weaver, 2015). Consequently, the magnitude of the increases in AGB induced by CO 2 enrichment estimated in this study, particularly under RCP8.5, can be largely overestimated due to possible deficiencies of either nutrients or water required by plant growth (S. .…”

“…S4a). The growing CO 2 concentrations can either increase AGB through enhanced photosynthetic rates (Fay et al, 2012;Lee et al, 2010) or have limited influences because of other environmental constraints on plant growth (Brookshire and Weaver, 2015). In this study, we deduced future AGB dynamics both including and not including the effect of CO 2 enrichment on grassland AGB.…”

“…the enhanced water limitations resulting from climate warming. The actual effects of CO 2 enrichment on AGB, however, depend substantially on local environmental factors such as water availability (Brookshire and Weaver, 2015) and soil texture (Polley et al, 2019).…”

Aboveground biomass in Inner Mongolian temperate grasslands decreases under climate warming

“…Evidences from the datasets independent of remote sensing products may help to disentangle the mysterious spatiotemporal dynamics of AGB at the regional scale. Moreover, existing studies have seldom considered the possible co-regulating effects of soil properties (Jia et al, 2011;Bhandari and Zhang, 2019), grassland types and grazing intensity (Eldridge and Delgado-Baquerizo, 2017) on AGB, which might lead to large uncertainties and biases in these estimations. In addition, little is known about the consequences of the likely future climate change on AGB dynamics across time and space, which is a substantial concern in the context of global warming.…”