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Kobresia meadows are the main pastures for animal husbandry on the Qinghai–Tibet Plateau, and may represent alternative steady states associated with different grazing intensities. The ability of other plant communities to succeed these meadows remains unclear. In this study, the historical data of plant communities were analyzed in terms of the soil profile, and the present characteristics were identified by investigating their plant communities. Four types of steady states were identified, corresponding to grazing intensities of >11, 8–11, 5.5–8 and

To analyze the genetic diversity of 9 species of Clematis from 31 different populations, we extracted DNA by the improved CTAB method, used ISSR-PCR for amplification, and then selected 9 primers with clear amplified bands from amongst 220 primers. A total of 127 clear bands were amplified, of which 126 were polymorphic bands, yielding a ratio of 99.2%. The polymorphism information index (PIC) of the primers ranged from 0.9326 to 0.9649. The Nei’s genetic diversity index (H) was 0.2750, the total gene diversity (Ht) was 0.2845, and the genetic differentiation coefficient (Gst) was 0.6696, indicating high genetic differentiation among populations of Clematis. After cluster analysis, the 31 Clematis populations were divided into 3 categories. Principal coordination analysis (PCoA) of 9 Clematis species then showed that the genetic relationship between samples of the same Clematis germplasms was closer than that of samples from the same region. The mantel test revealed a significant positive correlation between genetic distance and geographical distance among the populations. The population clustering results are broadly consistent with the clustering graphs of UPGMA and PCoA. We can conclude the polymorphism of the 9 primers is good, and that the genetic diversity of 31 Clematis populations is rich. Individual Clematis germplasms are closely related and will gather together preferentially.

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.

The alpine grassland shrubbization of the northern Qinghai-Tibet Plateau on the background of global change and overgrazing, is a prominent and serious problem. However, the water competition ability of shrubs and alpine grasslands is rarely reported. Here, we tracked the δ O and δ H of soil water, plant water, precipitation, and groundwater, analysed sources of water use in shrub and grassland by Mix SIAR model. Our results showed that both δ O and δ H in soil, precipitation, and plant varied significantly over time, groundwater remained relatively stable in P. fruticosa shrub and alpine grassland sites during observation. Considering groundwater, precipitation, soil water, and plant water, a progressive enrichment in δ O or δ H existed from groundwater and precipitation to soil water to plant water for each month. Alpine grassland was more susceptible to drought stress, had a stronger partitioning effect in dynamic transport than shrub. The P. fruticosa shrub displayed more flexible water utilisations, and was more competitive for water than grasslands. Furthermore, the plants in alpine shrub and grassland reached water use balance in August. Shrubs degraded from alpine grassland changed water use pattern of grassland, thereby changing soil water storage. These results contribute to in-depth understanding the alpine grassland shrubbization from water use patterns of grassland and shrub plants on the northern Qinghai-Tibet Plateau.

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.

The terrestrial methane budget varies between different vegetation types and soil conditions and is highly uncertain for alpine grasslands. This work used eddy covariance techniques to continuously measure CH4 flux (NEEm) over a semiarid alpine meadow on the northeastern Qinghai-Tibetan Plateau from January 2017 to August 2019. The diel NEEm averaged 0.14 ± 0.98 nmol CH4 m−2 s−1 (mean ± S.D.), with a rough pattern of daytime release and nocturnal uptake. The 8-day NEEm exhibited a similar sinusoid variation, with a peak of 6.8 mg CH4 m−2 d−1 at the end of April and a minimum of −1.5 mg CH4 m−2 d−1 at the end of August. The maximum release probably coincided with the thawing of frozen soil in the root zone, and the peak uptake may be related to high soil temperature. Monthly CH4 uptake was highest from June to September and consumed 51.7 mg CH4 m−2 from the atmosphere. CH4 production in the other months totaled 647.6 mg CH4 m−2. The semiarid alpine meadow thus acted as a weak net CH4 source, releasing ca 0.6 g CH4 m−2 year−1 to the atmosphere. The boosted regression trees analysis shows that the sensible heat flux (H) is positively related to half-hour NEEm and accounted for 34% of its variability. The piecewise structural equation models reveal that the magnitude of the effects from soil temperature and vapor pressure deficit on 8-day and monthly NEEm were almost equal, but acted in opposite directions. Vegetation growth and soil moisture exerted little direct influence on NEEm variability at half-hour, 8-day, or monthly scales. Our results show that CH4 emissions of the nongrowing season dominate the annual methane budget for this alpine meadow area. Methane consumption during the growing season was significantly constrained by low soil temperature and high soil water content. These findings imply that semiarid alpine meadows may consume more methane during the growing season if soil temperatures increase and soil moisture levels decrease as projected by future warming scenarios, thus constituting a climate change negative feedback.

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.

In recent decades, an increasing proportion of alpine shrub meadow has become severely degraded owing to the combined effects of global climate warming and rodent infestation, with significant impacts on soil water retention. The present paper investigates the patterns and controlling factors of soil water retention of alpine shrub meadow under different degrees of degradation, to help inform decisions on the management of degraded alpine shrub meadow. Four degradation stages were defined: non-degradation (ND); light degradation (LD); moderate degradation (MD) and higher degradation (HD). Pearson correlation and redundancy analysis were used to examine the relationships between soil physical properties and soil hydraulic properties. Sand content increased while clay content decreased with increasing degree of degradation. In HD treatment, the available nitrogen and soil bulk density of surface soil layer was significantly lower than that in the other three stages, whereas the soil organic matter content and soil total porosity of surface soil layer was increased significantly, the soil compaction of 0–10 cm soil depth in HD was reduced significantly. The soil water retention of 0–60 cm soil depth first decreased and then increased with increasing degradation, with the maximum values occurring in HD, and the soil organic matter has an overwhelming effect on soil water retention than soil texture. As the degree of degradation increased, the surface soil structure deteriorated, and available nitrogen reduced while soil organic matter increased sharply in higher degradation, which leads to the highest soil water retention in higher degradation. Our results suggested that the soil water retention in degraded alpine grassland was largely determined by soil organic matter, and the soil organic matter parameters should be incorporated in hydrological models of degraded alpine ecosystem.

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 soil seepage is an important component for quantifying hydrological processes while remains unclear in high-altitude alpine meadows. The shallow soil seepage was continuously measured by an auto-logged micro-lysimeter (diameter = 30 cm, depth = 30 cm) from July 2018 to June 2019 in a piedmont summer pasture of alpine meadow on the Northeastern Qinghai-Tibetan Plateau. The results showed that all the shallow soil seepage events occurred during the non-frozen period from April to September and the accumulative amount was 106.8 mm, which consumed about 1/5 annual precipitation. The maximum and minimum monthly soil seepage was 30.7 mm in September and 1.0 mm in April, respectively. The binary Logistic model revealed that daily half-hour rainfall frequency (R2 = 0.37, individual explanatory power) and amount played significant roles in the daily soil seepage odds (R2 = 0.50). The best subsets regression analysis showed that the same-day rainfall amount (R2 = 0.59), the first 3-day rainfall frequency, and the first 4-day solar radiation accounted for 73% of variations in the daily soil seepage amount. Monthly soil seepage correlated with monthly rainfall frequency significantly (R2 = 0.74, p = 0.005). Our results highlighted that precipitation, including its amount and frequency, was the key determinant of the probability and amount of the shallow soil seepage in the piedmont summer pasture of alpine meadow. These findings would be helpful for improving predictions of the water budgets of piedmont alpine meadows.

Satellite data indicate significant advancement in alpine spring phenology over decades of climate warming, but corresponding field evidence is scarce. It is also unknown whether this advancement results from an earlier shift of phenological events, or enhancement of plant growth under unchanged phenological pattern. By analyzing a 35‐year dataset of seasonal biomass dynamics of a Tibetan alpine grassland, we show that climate change promoted both earlier phenology and faster growth, without changing annual biomass production. Biomass production increased in spring due to a warming‐induced earlier onset of plant growth, but decreased in autumn due mainly to increased water stress. Plants grew faster but the fast‐growing period shortened during the mid‐growing season. These findings provide the first in situ evidence of long‐term changes in growth patterns in alpine grassland plant communities, and suggest that earlier phenology and faster growth will jointly contribute to plant growth in a warming climate., Climate change reshapes plant growth patterns by shifting phenology earlier, enhancing growth rate, and shortening growth period in a Tibetan alpine grassland over 35 years. The changes in growth patterns alters seasonal, but not annual, biomass production.

Aboveground biomass (AGB) and belowground biomass (BGB) allocation and productivity–richness relationship are controversial. Here, we assessed AGB and BGB allocation and the productivity–richness relationship at community level across four grassland types based on the biomass data collected from 80 sites across the Qinghai Plateau during 2011–2012. The reduced major axis regression and general linear models were used and showed that (a) the median values of AGB were significantly higher in alpine meadow than in other three grassland types; the ratio of root to shoot (R/S) was significantly higher in desert grassland (36.06) than intemperate grassland (16.60), alpine meadow (13.35), and meadow steppe (19.46). The temperate grassland had deeper root distribution than the other three grasslands, with about 91.45% roots distributed in the top 30 cm soil layer. (b) The slopes between log AGB and log BGB in the temperate grassland and meadow steppe were 1.09 and 1, respectively, whereas that in the desert grassland was 1.12, which was significantly different from the isometric allocation relationship. A competitive relationship between AGB and BGB was observed in the alpine meadow with a slope of −1.83, indicating a trade‐off between AGB and BGB in the alpine meadow. (c) A positive productivity–richness relationship existed across the four grassland types, suggesting that the positive productivity–richness relationship might not be affected by the environmental factors at the plant location. Our results provide a new insight for biomass allocation and biodiversity–ecosystem functioning research., The median values of aboveground biomass (AGB) were significantly higher in alpine meadow than in other three grassland types. The temperate grassland had deeper root distribution than the other three grasslands, with about 91.45% roots distributed in the top 30 cm soil layer. A positive productivity–richness relationship existed across the four grassland types.

Net primary production (NPP) is a fundamental property of natural ecosystems. Understanding the temporal variations of NPP could provide new insights into the responses of communities to environmental factors. However, few studies based on long‐term field biomass measurements have directly addressed this subject in the unique environment of the Qinghai‐Tibet plateau (QTP). We examined the interannual variations of NPP during 2008–2015 by monitoring both aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP), and identified their relationships with environmental factors with the general linear model (GLM) and structural equation model (SEM). In addition, the interannual variation of root turnover and its controls were also investigated. The results show that the ANPP and BNPP increased by rates of 15.01 and 143.09 g/m2 per year during 2008–2015, respectively. BNPP was mainly affected by growing season air temperature (GST) and growing season precipitation (GSP) rather than mean annual air temperature (MAT) or mean annual precipitation (MAP), while ANPP was only controlled by GST. In addition, available nitrogen (AN) was significantly positively associated with BNPP and ANPP. Root turnover rate averaged 30%/year, increased with soil depth, and was largely controlled by GST. Our results suggest that alpine Kobresia meadow was an N‐limited ecosystem, and the NPP on the QTP might increase further in the future in the context of global warming and nitrogen deposition.

The freeze-thaw cycle in the active soil layer plays a crucial role in cold-region hydrological processes, yet the effect of vertical water migration caused by the soil frost on shallow groundwater remains poorly quantified. The shallow groundwater level (GWL), soil frost depth and main environmental controls were monitored in a humid alpine meadow on the northeastern Qinghai-Tibetan Plateau from 2012 to 2017. GWL fluctuated with two seasonal maxima and minima during soil frost-centric year from November to October. GWL declined remarkably from the strong peak (3.9 ± 0.2 m, Mean ± S.D.) in mid-January to the strong minimum (4.8 ± 0.1 m) in mid-May, and then increased to the second peak (4.2 ± 0.2 m) in late August. This seasonal variability in GWL was mainly attributed to the freeze-thaw processes of the lower layer soil frost from November to late June both at a ∼45-day delay, respectively. The clear increasing GWL from mid-November to mid-January was probably related to the melted upper layer soil frost, which was detained in subsoil layers because of the high thermal isolating effect in topsoil Mattic Epipedon (dense organic-rich turf) and the associated negative subsoil profile temperature gradient from mid-May to late August. The seasonal N-type in GWL was thus hysteretically determined by the soil freeze-thaw processes and the related subsoil profile temperature gradient. Annually, GWL was significantly correlated with air temperature (R2 = 0.88, P = 0.003, N = 6), suggesting the shallow groundwater recharges would be weakened under the warming scenario. Annual GWL was not directly connected with annual precipitation (P = 0.81), likely owing to the high water holding capacity of the topsoil Mattic Epipedon and the similarity between precipitation input and evapotranspiration loss. This critical buffering function of the topsoil Mattic Epipedon in vertical moisture movement should be taken into consideration when modeling regional water dynamics in humid alpine meadows.

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.

Deep soil water infiltration is a key hydrological process in seasonally frozen regions, and displays a distinct behavior from that in other unfrozen regions; however, the seasonal dynamics and key controls of deep soil water infiltration in the seasonally frozen region of the Qinghai-Tibet plateau (QTP) are still poorly understood. In this study, we examine the seasonal dynamics of deep soil water infiltration, and attempt to quantitatively assess the relative influences of several driving factors by applying a random forests statistical analysis. The following key results were obtained. Deep soil water infiltration shows marked seasonal variation. Rainfall intensity exerts little effect on the seasonal dynamics of deep soil water infiltration as almost all rainfall returns to the atmosphere via evapotranspiration. No infiltration occurred when the depth of lower layer frozen soil reached 29 cm, whereas deep infiltration increased during the thawing of soil frost, suggesting that deep infiltration is impeded by soil freezing. Overall, the observed seasonal dynamics of deep soil water infiltration and volumetric soil moisture content were similar during the freeze-thaw process. Furthermore, deep soil water infiltration was more strongly influenced by deep volumetric soil moisture than by shallower volumetric soil moisture. Our results suggest that the topsoil Mattic Epipedon, soil organic matter content, and root systems’ role in vertical moisture movement should be taken into consideration when modeling hydrological processes in alpine meadows.

Large uncertainties exist in carbon-water-climate feedbacks in cold regions, partly due to an insufficient understanding of the simultaneous effects of climatic and biotic controls on water and carbon dynamics. The 10-year growing season flux data were analyzed to evaluate the relative contributions of climatic and biotic effects on the variability of water vapor (ET) and net ecosystem CO2 (NEE) exchanges over a humid alpine deciduous shrubland on the northeastern Qinghai-Tibetan Plateau. The results showed that the alpine shrubland ecosystem acted as a water source and a carbon sink during the growing season, and its potential ET and NEE ranged from 161.4 mm and –41.0 g C·m−2 to 408.0 mm and –278.4 g C·m−2 at a 95% confidence interval, respectively. The average 8-day ET and NEE during the early growing season (June to July) were both significantly (P

With the vigorous development of MOOC open online courses, low completion rate of courses has become an important side effect factor which is affecting the promotion and application of MOOC courses in worldwide. Through analysis of edX open data sets, it is found that loss of learners is one of the factors which are leading to low completion rate of MOOC courses, and also there is a close correlation between learning behavior and final scores with loss of learners. Based on this challenge, some research results show that low completion rate of MOOC courses can be greatly improved by predicting the relationship between learning behavior and scores. This article focuses on application of Deep Neural Network (DNN) in prediction and analysis of MOOC learners' learning behavior. First, data analysis of course performance and learning behavior are discussed, then prediction model based on DNN is given for learning behavior and final scores. Second, experiment is done for DNN model, the results show that DNN can be used for analysis and prediction of complex correlation between learning behavior and final scores, thus which can realize more accurate prediction, reduce loss of learner, and carry out individualized teaching intervention to potential learners.

Biomass temporal stability plays a key role in maintaining sustainable ecosystem functions and services of grasslands, and climate change has exerted a profound impact on plant biomass. However, it remains unclear how the community biomass stability in alpine meadows responds to changes in some climate factors (e.g., temperature and precipitation). Long-term field aboveground biomass monitoring was conducted in four alpine meadows (Haiyan [HY], Henan [HN], Gande [GD], and Qumalai [QML]) on the Qinghai-Tibet Plateau. We found that climate factors and ecological factors together affected the community biomass stability and only the stability of HY had a significant decrease over the study period. The community biomass stability at each site was positively correlated with both the stability of the dominant functional group and functional groups asynchrony. The effect of dominant functional groups on community stability decreased with the increase of the effect of functional groups asynchrony on community stability and there may be a 'trade-off' relationship between the effects of these two factors on community stability. Climatic factors directly or indirectly affect community biomass stability by influencing the stability of the dominant functional group or functional groups asynchrony. Air temperature and precipitation indirectly affected the community stability of HY and HN, but air temperature in the growing season and nongrowing season had direct negative and direct positive effects on the community stability of GD and QML, respectively. The underlying mechanisms varied between community composition and local climate conditions. Our findings highlighted the role of dominant functional group and functional groups asynchrony in maintaining community biomass stability in alpine meadows and we highlighted the importance of the environmental context when exploring the stability influence mechanism. Studies of community stability in alpine meadows along with different precipitation and temperature gradients are needed to improve our comprehensive understanding of the mechanisms controlling alpine meadow stability.

Alpine grasslands play important functions in mitigating climate change and regulating water resources. However, the spatiotemporal variability of their carbon and water budgets remains unquantified. Here, 47 site-year observations of CO