Glomalin-related soil protein (GRSP) is a recalcitrant glycoprotein mainly produced by arbuscular mycorrhizal fungi and contributes to soil carbon sequestration. Human activities (grazing, fertilization, etc.) can change plant productivity, soil carbon pool, and microbial community in an alpine grassland ecosystem. However, no study has reported on the effect of human activities on GRSP. Besides, the effect of the interaction between environmental factors and human activities on GRSP is unknown. This study assessed GRSP response to grazing intensity gradients and fertilization in an alpine grassland (Qinghai-Tibet Plateau). The result showed that livestock grazing changed GRSP stability in alpine grassland. Moreover, the content of total GRSP and easily extractable GRSP were gradually decreased with increasing grazing intensities in both surface and subsurface soils. GRSP was highly positively correlated with soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP) but negatively correlated with the soil inorganic carbon (SIC) and PH (P<0.001). GRSP promoted SOC by 3.7-14.18%. In contrast, N and P addition for five years did not affect SOC and GRSP contents. Therefore, GRSP is a stable organic carbon essential for SOC fixation. Short-term distractions cannot affect GRSP stability, while long-term overgrazing can gradually reduce GRSP stability. This study provides new insights into soil carbon pool and ecological stoichiometry in the grassland succession process on the Qinghai-Tibet plateau.

Water use efficiency is an important indicator of drought tolerance of plants. The response was still unclear of water use efficiency to different grazing intensity and its adaptive mechanisms in alpine meadow. Here, we analyzed water use efficiency of plant dominant species, coexisting species and functional group level plants to grazing intensity by δ13C index in alpine meadow. Furthermore, this study revealed the driven factors of water use efficiency combined available nitrogen, soil bulk density, soil organic carbon, soil water content and evapotranspiration. Grazing increased plants δ13C by 3.37%. Moderate grazing significantly increased the δ13C of Gramineae by 4.84% (P<0.05), and increased δ13C of Cyperaceae, Leguminosae, and Forb by 3.45%, 0.81%, and 1.40% respectively. Some dominant species and coexisting species have the highest δ13C value under moderate grazing. This study indicated that moderate grazing significantly improved the water use efficiency of alpine meadows. Path analysis resulted showed that the water use efficiency was negatively correlated with evapotranspiration (P<0.05), soil water content, soil organic carbon, and soil bulk density. It was positively correlated with available nitrogen. Our study provides new insights that moderate grazing help to increase water use efficiency in alpine meadows. In addition, evapotranspiration may be the main driving factor affecting the water use efficiency of alpine meadow.

Dew is closely related to the micro-use of water and to large-scale hydrological processes. Dew formation on grasslands plays a particularly vital role in maintaining the ecohydrological cycle, however, its characteristics and sources were rarely reported. Here, stable isotope for dew, ambient water vapor, soil water, plant water, creek water, and precipitation were tracked to determine the characteristics of dew from ecohydrological processes in the meadow. The structural equation model was used to investigate how environmental factors affect dew formation. The Mix SIAR model in R was used to determine the sources of dew, and explore the dew transport route of six species of the graminoid-Kobresia meadow in an alpine graminoid-Kobresia meadow in northern Qinghai-Tibet Plateau. Our results showed that the annual amount was about 37.92 ± 1.03 mm, acounting for 7.13% of precipitation. Both atmospheric pressure and temperature showed significant positive effects on dew formation, while wind speed had a negative effect. Evapotranspiration indirectly affected dew formation. The contribution rates of soil water, plant water, and ambient water vapor to dew formation were 48.20±5.46%, 38.30±5.07%, and 13.50±1.82%, respectively. The proportion of dew utilization by graminoid and Kobresia species showed no significant species differences, the mean value was 10.5±3.8%. Our statistical analysis determines the role of dew in an alpine graminoid-Kobresia meadow in the northern Qinghai-Tibet Plateau, which provides an improved understanding of dew formation based on a stable isotope technology.

Dew is closely related to the micro-use of water and to large-scale hydrological processes. Dew formation on grasslands plays a particularly vital role in maintaining the ecohydrological cycle. Stable isotope information for dew, ambient water vapor, soil water, plant water, creek water, and precipitation were tracked to determine the role of dew in ecohydrological processes in the meadow. The structural equation modeling was used to investigate how environmental factors affect dew formation. The Mix SIAR model in R was used to determine the source of dew, and explore the dew transport route of six species of the graminoid-Kobresia meadow in an alpine graminoid-Kobresia meadow in northern Qinghai-Tibet Plateau. Our results showed that the amounts of dew ranged from 0.002 mm to 0.22 mm, the frequency of dew was 42.86%-45.83% during summer in 2020 and 2021. Both atmospheric pressure and temperature showed significant positive effects on dew formation, while wind speed had a negative effect. Evapotranspiration indirectly affected dew formation. The contribution rates of soil water, plant water, and ambient water vapor to dew formation were 48.20±5.46%, 38.30±5.07%, and 13.50±1.82%, respectively. The proportion of dew utilization by graminoid and Kobresia species showed no significant species differences. Our statistical analysis determines the role of dew in an alpine graminoid-Kobresia meadow in the northern Qinghai-Tibet Plateau, which provides an improved understanding of dew formation based on a stable isotope technology.

Mini-patches are considered indicators of an ecosystem’s response to interference, particularly those in alpine meadow ecosystems. Thus, monitoring the characteristics of mini-patches can elucidate the organization of an ecosystem’s components, the strategies it employs to survive interference, and the mechanisms whereby it maintains stability. In this research, we used multivariate statistical analysis methods to investigate the characteristics of the plant community and the micro-topography of mini-patches in alpine meadows on the Qinghai-Tibet Plateau from August 2012 to August 2013. Our findings show that (1) mini-patches were distributed in alpine meadows with different levels of degradation and the effects of meteorological characteristics (accumulated temperature above 0°C and accumulation of precipitation) and geographical characteristics (altitude, longitude, and latitude) contributed less than 20% to their distribution and characteristics; (2) alpine meadows maintained aboveground biomass within a certain range under a relative larger range of grazing intensity, illustrating their ability to regulate community structure and components under various intensities of disturbance and showing that alpine degradation could itself counteract grazing disturbance; and (3) overgrazing is the main driver of multi-steady stage coexistence in alpine meadows, as the mini-patches that remain involved in plant community succession function, and as a source of germplasm in the plant community regime shift under different grazing intensities damaged alpine meadows.

Studying the interrelation of soil water and plant water is essential for an in-depth understanding of eco-hydrological processes. However, water use relationships and comparative studies between shrubs and alpine grassland of the northern Qinghai-Tibet Plateau remain poorly understood. In this study, we compared δ18O and δ2H values of water from soil, plant, precipitation, and groundwater between P. fruticosa shrub and alpine grassland locations at two neighboring sites in order to better understand the interface between plant and surrounding soils of shrubs and grasslands in the northern Qinghai-Tibet Plateau. Our results showed that δ18O and δ2H of soil water, precipitation, and plant water varied significantly over time and water sources in P. fruticosa shrub and alpine grassland sites. Both soil evaporation and plant transpiration at the P. fruticosa shrub site were relatively lower than they were at the alpine grassland site. Alpine grassland plant water had a stronger dynamic fractionation effect in the process of transportation and was more sensitive to environmental conditions. However, plants at the P. fruticosa shrub site displayed more flexible water use patterns, shifted their water sources between shallow soil water and deep soil water. Shrubs from alpine grassland leaded to changes in grassland water use, thereby changing soil water storage. The results of this study will provide theoretical basis for improving the availability and sustainability of soil water, provide guidance for meadow management from ecohydrological processes on the northern Qinghai-Tibet Plateau.

The impacts of human-driven environmental changes on the stability of natural grasslands have been assessed by comparing differences between manipulative warming and grazing plots and reference plots. However, little is known about whether or how ambient climate regulates the effects of manipulative treatments. A 36-year observational dataset shows that there is a nonlinear response of community stability to ambient climate. Manipulative warming and grazing decrease community stability with experiment duration through an increase in legume coverage and/or decrease in species asynchrony, due to exceeding the threshold of background annual mean air temperature with decreasing background annual mean air temperature through time during the 10-year experiment period. Moreover, the temperature sensitivity of community stability is more sensitive under the ambient treatment than under the manipulative treatments. Therefore, our study emphasizes the importance of the context dependency of the response of community stability to human-driven environmental changes.

Accurate estimates of evapotranspiration (ET) are of great importance for water balance and energy exchange processes, as ET constitutes the key component of the terrestrial water cycle. Although many applicable reference evapotranspiration (ET0) models have been developed to estimate the ET, these are largely focused on low altitude regions, with little attention to alpine meadow. In this paper, we evaluate the performance of 13 ET0 models by comparison with large weigh lysimeter measurements. Specifically, we use three combination models, seven radiation-based models and three temperature-based models driven with data from 8 June 2017 to 18 September 2018 in a humid alpine meadow, northeastern Qinghai-Tibetan Plateau. The daily ET was also obtained by large weighing lysimeters located in an alpine Kobresia meadow. Results show that the performances of the 13 ET0 models, ranked on the basis of their RMSE (root mean square error), decreased in the order: DeBruin-Keijman>Priestley-Taylor> 1963 Penman> FAO-24 Penman>Hargreaves>Hargreaves2>Hargreaves1>IRMAK1>FAO-56Penman-Monteith>Makkink>Makkink (1967)>Makkink (1957)>IRMAK2. Overall, the radiation-based models performed best, with RMSEs ranging from1.03 to 1.47 mm d−1 and averaging 1.09 mm d−1, followed by the combination models (RMSE from 1.19 to 1.36 mm d−1 and averaging 1.26 mm d−1) and temperature models (RMSE from 1.28 to 1.32 mm d−1 and averaging 1.29 mm d−1). The best radiation-based model (DeBruin-Keijman) was more accurate than the best combination model (1963 Penman) and temperature model (Hargreaves) by 16.67% and 25.49%, respectively. The better performance of the radiation-based models over the other two types may be attributed to their inclusion of the dominant factors affecting ET, such as net radiation (Rn). All models tended to underestimate measured ET during periods of larger evaporative demand (i.e. growing season) and overestimate measured ET during lower evaporative demand (i.e. non-growing season). Our results could help in the selection of a suitable ET model for alpine ecosystems, thereby benefitting water irrigation management.

A document by Licong Dai. Click on the document to view its contents.

In recent decades, alpine grassland has been serimously degraded across the Qinghai Tibetan Plateau (QTP), although grazing exclusion has been widely adopted to restore degraded QTP grassland. It remains unknown whether this management approach is effective for all degraded alpine grasslands. In this study, plots with three grazing management treatments (free grazing, FG; reduced grazing, RG; grazing exclusion, GE) and four degradation stages (non-degradation, ND; light degradation, LD; moderate degradation, MD; heavy degradation, HD) were compared. Our results showed that the total aboveground biomass (AGB) and species richness (SR) were reduced while total belowground biomass (BGB) increased with increasing degradation, and the responses of SR, AGB and BGB to grazing management varied with the degree of degradation. The total AGB in the LD, MD and HD stages reduced significantly after 6 years under RG and GE, but there was no significant change of AGB in the ND stage. Meanwhile, SR reduced significantly after 6 years under RG and GE across all degradation stages except for HD. Furthermore, the responses of plant functional groups to grazing management varied. After 6 years under RG and GE, the Gramineae AGB increased significantly across all degradation levels; that of the sedges decreased (except in the MD stage); and that of the forbs increased significantly in LD and HD but decreased significantly in ND. Our result suggested that the light degradation grassland can be restored by reducing grazing, and moderate degradation and heavy degradation grassland can restored by grazing exclusion.