Effects of Grazing on Above- vs. Below-Ground Biomass Allocation of Alpine Grasslands on the Northern Tibetan Plateau

Abstract

Biomass allocation is an essential concept for understanding above- vs. below-ground functions and for predicting the dynamics of community structure and ecosystem service under ongoing climate change. There is rare available knowledge of grazing effects on biomass allocation in multiple zonal alpine grassland types along climatic gradients across the Northern Tibetan Plateau. We collected the peak above- and below-ground biomass (AGB and BGB) values at 106 pairs of well-matched grazed vs. fenced sites during summers of 2010–2013, of which 33 pairs were subject to meadow, 52 to steppe and 21 to desert-steppe. The aboveground net primary productivity (ANPP) was represented by the peak AGB while the belowground net primary productivity (BNPP) was estimated from ANPP, the ratio of living vs. dead BGB, and the root turnover rate. Two-ways analyses of variance (ANOVA) and paired samples comparisons with t-test were applied to examine the effects of pasture managements (PMS, i.e., grazed vs. fenced) and zonal grassland types on both ANPP and BNPP. Allometric and isometric allocation hypotheses were also tested between logarithmically transformed ANPP and BNPP using standardized major axis (SMA) analyses across grazed, fenced and overall sites. In our study, a high community-dependency was observed to support the allometric biomass allocation hypothesis, in association with decreased ANPP and a decreasing-to-increasing BNPP proportions with increasing aridity across the Northern Tibetan Plateau. Grazing vs. fencing seemed to have a trivial effect on ANPP compared to the overwhelming influence of different zonal grassland types. Vegetation links above- and below-ground ecological functions through integrated meta-population adaptive strategies to the increasing severity of habitat conditions. Therefore, more detailed studies on functional diversity are essentially to achieve conservation and sustainability goals under ongoing climatic warming and intensifying human influences.

Modeling impacts of climate change and grazing effects on plant biomass and soil organic carbon in the Qinghai–Tibetan grasslands

“…Generally, natural grassland is the major food source for the livestock in the QTP. Compared with 1949, the number of livestock has increased by almost 3 times from 7.49 × 10 6 (Zhang, 2011) to the peak number of 22.19 × 10 6 head in 2005 at the study area (QPBS, 2005(QPBS, , 2015.…”

“…Qinghai Province supports over 40 % of the population of the QTP, but it has about 29 % of its total area, and thus it plays an important role in the whole QTP (X. L. Piao et al, 2012). This area is recognized as one of the most ecologically fragile and sensitive areas to global climate change and human disturbance (Piao et al, 2012;Wang et al, 2002;Zeng et al, 2015;Harris, 2010). Moreover, this area is also the largest animal husbandry production region in China, and it also contains the headwaters of the two major rivers in China, i.e., the Yellow River and the Yangtze River, and thus it plays a vital role in ecological conservation in China (Zeng et al, 2015).…”

Combining livestock production information in a process-based vegetation model to reconstruct the history of grassland management

“…europa.eu/mars/About-us/AGRI4CAST/Data-distribution/ AGRI4CAST-Interpolated-Meteorological-Data), or WorldClim database (Hijmans et al, 2005). Three additional datasets used in this study present NPP measurements from 30 sites across China (Zeng et al, 2015;Y. Bai, personal communication, 2015) and 16 sites across western Siberia (Peregon et al, 2008; with data updated to 2012).…”

Identifying the Relative Contributions of Climate and Grazing to Both Direction and Magnitude of Alpine Grassland Productivity Dynamics from 1993 to 2011 on the Northern Tibetan Plateau

“…Livestock husbandry is the dominant economic activity and the major source of income for the herdsman families in this region, generally accounting for 74%-93% of their annual gross income [22]. Livestock grazing is an extensive anthropogenic disturbance in NTP, so this region is increasingly accepted as the most ideal region for studying feedback between vegetation, climate, and grazing on the Qinghai-Tibetan Plateau [23][24][25]. Across NTP, plants generally start to grow in early May and to senesce in late September, with up to 85% of annual precipitation falling and mean daily temperature being over 5.0 • C during this period [24].…”