Effects of different intensities of long-term grazing on plant diversity, biomass and carbon stock in alpine shrubland on the Qinghai-Tibetan Plateau

Grazing is the main grassland management strategy applied in alpine shrubland ecosystems on the Qinghai-Tibetan Plateau. However, how different intensities of long-term grazing affect plant diversity, biomass accumulation and carbon (C) stock in these ecosystems is poorly understood. In this study, alpine shrubland with different long-term (more than 30 years) grazing intensities (excluded from grazing for 5 years (EX), light grazing (LG), moderate grazing (MG) and heavy grazing (HG)) on the Qinghai-Tibetan Plateau were selected to study changes in plant diversity, aboveground biomass and C accumulation, as well as distribution of C stock among biomass components and soil depths. A structural equation model was used to illustrate the impact of grazing on the soil carbon stock (SOC). The results showed that the Shannon–Wiener diversity index and richness index of herbaceous plants, shrubs, and communities first significantly increased and then decreased with increasing grazing intensity, reaching maxima at the LG site. The aboveground and belowground and litter biomass of understory herbaceous plants, shrubs and communities decreased with increasing grazing intensity, reaching maxima at the EX site. The aboveground and belowground biomass C storage decreased with increasing grazing intensity, reaching maxima at the EX site. The SOC stock and total ecosystem C stock decreased with increasing grazing intensity, reaching maxima at the EX and LG sites. A structural equation model showed that grazing-induced changes in the belowground biomass of understory herbaceous plants greatly contributed to the SOC stock decrease. Thus, considering the utilization and renewal of grassland resources, as well as local economic benefits and ecological effects, LG may be a more rational grazing intensity for species diversity conservation and ecosystem C sequestration in alpine shrubland. Our results provide new insights for incorporating grazing intensity into shrub ecosystem C stock and optimizing grazing management and grassland ecosystem C management.

Fire and forage quality: post-fire regrowth quality and pyric herbivory in subtropical grasslands of Nepal.

Indiscriminate fire is rampant throughout subtropical South and Southeast Asian grasslands. However, very little is known about the role of fire and pyric herbivory on the functioning of highly productive subtropical monsoon grasslands lying within Cwa-climatic region. We collected grass samples from 60 m x 60 m plots and determined vegetation physical and chemical properties at regular 30-day intervals from April to July 2020, starting from 30 days after fire to assess post-fire regrowth forage quality. We counted pellet groups for the same four months from 2 m x 2 m quadrats that were permanently marked with pegs along the diagonal of each 60 m x 60 m plot to estimate grazing intensity to the progression of post-fire regrowth. We observed strong and significant reductions in crude protein (mean value 9.1 to 4.1 [55% decrease]) and phosphorus (mean value 0.2 to 0.11 [45% decrease]) in forage collected during different time intervals i.e., from 30 days to 120 days after fire. Mesofaunal deer utilised the burned areas extensively for a short period, i.e., up to two months after fire when the burned areas contained short grasses with a higher level of crude protein and phosphorus. Grazing intensity of chital (Axis axis) to post-fire regrowth differed significantly over time since fire, with higher intensity of use at 30 days after fire. Grazing intensity of swamp deer (Rucervus duvaucelii) did not differ significantly until 90 days after fire, however, decreased significantly after 90 days since fire. Large-scale indiscriminate single event fires thus may not fulfil nutritional requirements of all species in mesofaunal deer community in these subtropical monsoon grasslands. We recommend for a spatio-temporal manipulation of fire to reinforce grazing feedback and to yield for the longest possible period a reasonably good food supply for the conservation of mesofaunal deer.

Carbon variation of dry grasslands in Central Asia in response to climate controls and grazing appropriation

Quantification of grassland carbon (C) variations is necessary for understanding how grazing and climate change interact to regulate carbon capture and release. Central Asia (CA) has the largest temperate grassland belt in the world and unique temperate dryland ecosystems, which experienced severe climate change and grazing-induced disturbances. However, the impact of grazing on C dynamics is highly uncertain owing to climate variations. Here, an arid ecosystem model (AEM) supplemented with a grazing module that specifically addressed physiological and ecological characteristics of dryland vegetation was developed to quantitatively simulate grassland C dynamics in response to changes in precipitation, temperature, grazing intensity, and CO2 level in the past decades. The regional simulation results showed that net primary productivity (NPP) was affected mainly by precipitation (in 59% of the studied area). Grazing had a negative effect on NPP and C stocks, whereas overcompensation occurred in 25.71% of the studied area, mainly in the dry western parts. The complex interaction effects of climate, CO2, and grazing negatively affected productivity, with a grassland NPP decrease of − 1.14 g C/m2/a and high interannual variability. We found that the temporal pattern of cumulative C sequestration, especially total C and vegetation C (VEGC), closely followed the annual fluctuations of precipitation. VEGC stocks decreased from 182.22 to 177.82 g C/m2, with a very low value between 1998 and 2008, when precipitation significantly decreased. The results indicate that southern Xinjiang and the Turgay Plateau of Kazakhstan are ecologically fragile areas due to grassland degradation.

An inverse relationship between moisture and grazing intensity in an arid mountain-basin system

Precipitation has been suggested as a crucial influencing factor in the primary productivity in arid and semi-arid regions, yet how moisture fluctuation in an arid mountain-basin system of the north Qinghai–Tibetan Plateau has affected human activities is poorly understood. Here, we reconstruct the variations of grazing intensity in high elevations and regional humidity based on independent and high-resolution records of Sporormiella-type coprophilous fungal spores and pollen grains in the same well-dated sediment core from Lake Tian’E in the western Qilian Mountains over the past 3500 years. We find that stronger grazing activity was associated with low regional effective moisture, and propose that the drier regional climate pushed people and their livestock into the mountainous areas. A notable exception was a reduction of human and grazing activities in arid region with high mountains during 380–580 CE caused by centennial-length dry and cold conditions. In addition, it is also noteworthy that intensified grazing activity occurred during 580–720 CE and after ∼1920 CE, corresponding to a warmer and wetter climate and diverse subsistence strategies with social developments in the lowlands of the Hexi Corridor. Our findings potentially provide a historical reference for understanding how ancient people adapted to the climate change in arid region with high mountains.

The effect of grassland transfer on herders' livestock production and grazing intensity in Inner Mongolia and Gansu, China

Purpose The purpose of this study is to understand the impact mechanism of grassland transfer on herders' production behaviour in pastoral areas. The impact of grassland transfer on herders' livestock production and grazing intensity is quantified.Design/methodology/approach Using the survey data collected for 356 herder households from Inner Mongolia and Gansu, China, quantile regression is employed to assess the heterogeneous effects of grassland transfer on livestock production and grazing intensity. To correct the potential self-selection bias of grassland transfer, the propensity score matching technique is used.Findings Results show that labour, percentage of livestock income and livestock stock are the main factors affecting herders' choice to transfer grassland. The positive effect of grassland transfer on livestock numbers on behalf of those who rented additional grassland is statistically significant but declines with livestock numbers. The sustainability-enhancing effect of grassland transfer on grazing intensity is significant, and the effect becomes larger amongst herder households with higher grazing intensity. The analysis on the impact mechanism shows that grassland transfer significantly promotes the adoption of sustainable grazing modes, such as rotational and seasonal rest grazing, which in turn increases herders' livestock numbers and decreases grazing intensity.Originality/value Few studies have empirically analysed the influence of grassland transfer on livestock numbers and grazing intensity. This study fills this gap by employing a quantile regression to assess the heterogeneous effects of grassland transfer on livestock numbers and grazing intensity, while accounting for self-selection bias. In addition, the authors have examined the influencing mechanisms under which grassland transfer impacts on livestock numbers and grazing intensity.

Restoration of Degraded Grassland Significantly Improves Water Storage in Alpine Grasslands in the Qinghai-Tibet Plateau

Alpine grassland has very important water conservation function. Grassland degradation seriously affects the water conservation function; moreover, there is little understanding of the change of water state during grassland restoration. Our study aims to bridge this gap and improve our understanding of changes in soil moisture during the restoration process. In this study, the water storage, vegetation, and meteorology of a non-degradation grassland (grazing intensity of 7.5 sheep/ha) and a severely degraded grassland (grazing intensity of 12–18 sheep/ha) were monitored in the Qinghai-Tibet Plateau for seven consecutive years. We used correlation, stepwise regression, and the boosted regression trees (BRT) model analyses, five environmental factors were considered to be the most important factors affecting water storage. The severely degraded grassland recovered by light grazing treatment for 7 years, with increases in biomass, litter, and vegetation cover, and a soil-water storage capacity 41.9% higher in 2018 compared to that in 2012. This increase in soil-water storage was primarily due to the increase in surface soil moisture content. The key factors that influenced water storage were listed in a decreasing order: air temperature, litter, soil heat flux, precipitation, and wind speed. Their percentage contributions to soil-water storage were 50.52, 24.02, 10.86, 7.82, and 6.77%, respectively. Current and future climate change threatens soil-water conservation in alpine grasslands; however, grassland restoration is an effective solution to improve the soil-water retention capacity in degraded grassland soils.

Current condition of populations and spatial-environmental features of habitats of russet ground squirrel Spermophilus major

The russet ground squirrel (Spermophilus major ) is known in the literature as a numerous widespread ground squirrel species. In recent decades, a decline in its abundance was found in some parts of its range. We have assessed the condition of this species in most parts of its distribution area based on our observations and interviews with local people. Spatial, landscape and vegetation cover parameters of S. major settlements have been studied. The research results showed a decline in the number, disappearance of settlements and a decrease in suitable habitats for this species. Small and medium-sized settlements with relatively low density of burrows, associated with low grass meadow communities typical for pastures and cattle grazing, prevail among the found settlements. One of the main factors for the decline in the number and disappearance of settlements of russet ground squirrel is, apparently, a decrease of pasture cattle grazing intensity. The continuing trend of degradation of pasture ecosystems may pose a threat to the existence of this species.

Estimation of Energy Expenditure in Breeding Cows Grazing Rangelands with Different Herbage Allowance

The energy partitioning between total heat production (HP) and retained energy (RE) on the efficiency of energy use was evaluated throughout the annual production cycle (gestation-lactation) of 46 multiparous beef cows grazing on two herbage allowances (HA) of Campos grassland (4 vs. 7 kg dry matter/kg body weight; BW; LO vs. HI). Total RE was greater (P < 0.01) for HI than LO cows and presented minimum values during early gestation and maximum values during early lactation associated to the greater (P = 0.02) RE-milk in the former ones. Whole-animal HP, estimated by the heart rate-O2 pulse technique, and cow metabolized energy (ME) intake did not differ between HA treatments, but relative to BW0.75, HP was greater (P = 0.04) for LO than HI cows. Total HP and ME intake were minimum in gestation and maximum in early lactation and ME intake was greater during early lactation for HI than LO cows, and per unit of BW0.75, tended (P < 0.10) to be less for HI than LO cows in winter. The energy efficiency of the annual cycle was not affected by treatments (0.19 vs. 0.12 ± 0.02 for HI and LO respectively; P > 0.10) and there were no differences between treatments in terms of grams of calf per MJ of ME intake (P > 0.10). Management of grazing intensity of Campos grasslands with high herbage allowance improved energy balance of the beef cow-calf system through partitioning of cow ME intake towards RE instead of maintenance.