The Plant Interspecific Association in the Revegetated Alpine Grasslands Determines the Productivity Stability of Plant Community Across Restoration Time on Qinghai-Tibetan Plateau.

Grassland cultivation is the key measure for restoring "Black Beach," the extremely degraded alpine meadow in the Three River Headwater Area of the Qinghai-Tibetan Plateau. In this study, we examined the inter-specific relationship in the vegetation community of cultivated grasslands with different restoration times through the network analysis method. The results showed that with the extension of restoration time, the development of cultivated grassland would lead to increasing neutral interactions among the plant species. The proportion of species with positive and negative associations in the community decreased, while the number of species-independent pairs increased significantly. The complexity of plant interspecific association (species network density) had more influence on community stability with the extension of recovery time, which can be used to quantify the characteristics of community structure.

[Application of a multiple linear regression model of FEV1 in pulmonary function test].

OBJECTIVE: To construct a multiple linear regression model of forced expiratory volume in 1 second (FEV1) for estimating FEV1 in special populations unable to receive or uncooperative in pulmonary ventilation function tests. METHODS: The multiple linear regression model of FEV1 was constructed based on the data of 813 individuals undergoing pulmonary function tests in First Affiliated Hospital of Zhejiang Chinese Medical University between September, 2017 and September, 2019, and was validated using the data of another 94 individuals from the same hospital between January and July, 2020. FEV1 of the individuals was measured by pulmonary ventilation function test, and respiratory resistance (Rrs) was measured using forced oscillation technique (FOT). Pearson correlation analysis was used to assess the correlation between the factors, and the model equation was established by multiple stepwise regression analysis. The calculated FEV1 based on the model was compared with the measured FEV1 among both the individuals included for modeling and validation. RESULTS: FEV1 was not significantly correlated with BMI (r=-0.026, P=0.457), poorly correlated with body mass (r=0.382, P=0.000), positively correlated with height (r=0.723, P=0.000), and negatively correlated with Rrs (r=-0.503, P=0.000) with an obvious gender differences (t=18.517, P=0.000). FEV1 was positively correlated with age among individuals below 25 years of age (r=0.578, P=0.000) and was negatively correlated with age among those beyond or at the age of 25 (r=-0.589, P=0.000). For individuals beyond or at the age of 25 years, the variables of height, gender, age and Rrs were included in the model, and the calculated FEV1 did not differ significantly from the measured values in either the modeling sample (n=751; t=1.293, P=0.196) or the verification sample (n=83;t=-1.736, P=0.086), and the two values were well correlated in the verification sample (r=0.891, P=0.000). For individuals below 25 years, only height was included in the model, and the calculated FEV1 and the measured values showed no significant difference in the modeling sample (n=62; t=-0.009, P=0.993) or the verification sample (n=11; t=-0.635, P=0.540) with a good correlation in the verification sample (r=0.795, P=0.003). CONCLUSIONS: The multiple linear regression model for calculating FEV1 constructed in this study is suitable for clinical application.

Eco-physiological processes are more sensitive to simulated N deposition in leguminous forbs than non-leguminous forbs in an alpine meadow of the Qinghai-Tibetan Plateau.

Increased nitrogen (N) deposition can affect ecosystem processes and thus influence plant eco-physiological processes in grasslands. However, how N deposition affects eco-physiological processes of leguminous and non-leguminous forbs in alpine grasslands is understudied. A long-term field experiment using a range of simulated N deposition rates (0, 8, 24, 40, 56, and 72 kg N ha-1 year-1) was established to examine the effects of N deposition on various eco-physiological parameters in leguminous and non-leguminous forbs in an alpine meadow of the Qinghai-Tibetan Plateau. We found that the responses of leguminous and non-leguminous forbs to simulated N deposition varied. Net photosynthetic rate of leguminous and non-leguminous forbs exhibited different response patterns, but chronic increases in simulated N deposition rates may lead to negative effects in both functional groups. Neither functional group responded differently in aboveground biomass under the highest N addition level (72 kg N ha-1 year-1) compared to the control. Differences in aboveground biomass of leguminous forbs were observed at intermediate N levels. Short-term simulated N deposition significantly promoted N uptake of both functional groups. In leguminous forbs, simulated N deposition affected net photosynthetic rates (PN) and aboveground biomass (AGB) mainly via stomatal conductance (gs), water use efficiency (WUE), and plant N uptake. In non-leguminous forbs, simulated N deposition affected PN and AGB mainly through WUE and plant N uptake. Our findings suggest that leguminous and non-leguminous forbs have differential response mechanisms to N deposition, and compared with non-leguminous forbs, leguminous forbs are more sensitive to continuing increased N deposition. The obvious decline trend in photosynthetic capacity in leguminous forbs is likely to exacerbate the already divergent ecological processes between leguminous and non-leguminous forbs. More importantly, these changes are likely to alter the future composition, function, and stability of alpine meadow ecosystems.

Cooperative grassland management practices promoted by land tenure system transformation benefit social-ecological systems of pastoralism on the Qinghai-Tibetan plateau, China.

China has recently implemented the latest rural land tenure reform with the "Separating Three Property Rights" as non-tradable land ownership, non-tradable land contracting right and tradable land use right, leading to a dramatic change in grassland management strategies in vast pastoral areas. However, the impact of this new reform on grassland management practices is widely debated by scholars and policy analysts. To identify the factors impacting the pastoralists' choice of grassland management practice and the social, economic and ecological benefits derived from different grassland management practices, we conducted a field survey of pastoralists (n = 259) in 7 counties on the Qinghai-Tibetan Plateau. The results showed that respondents' gender, grassland area, scale and location of the village, grassland condition perception significantly exerted positive influence on pastoralists' willingness to participate in cooperative grassland management practices, while grassland fence and urban life expectation negatively influenced the willingness. We found that cooperative grassland management practices led to significantly higher household incomes, more equal gender relationships and better-managed grasslands than individual ones. In spite of this, there were still a large number of pastoralists who chose individual grassland management practices due to their long-term customary operations. In conclusion, this new rural land tenure reform has facilitated pastoralists' choice for diverse grassland management practices and the promoted voluntary large-scale cooperative grassland management practices benefit the social-ecological system of pastoralism.

Different responses of multifaceted plant diversities of alpine meadow and alpine steppe to nitrogen addition gradients on Qinghai-Tibetan Plateau.

Qinghai-Tibetan Plateau (QTP), >4000 m known as the "third pole of the earth" and is highly sensitive to nitrogen (N) deposition, understanding the effects of N deposition on multifaceted plant diversity (taxonomy diversity, functional diversity and phylogenetic diversity) in the alpine grasslands of Qinghai-Tibet Plateau are vital for the conservation of alpine plant diversity and the sustainability of alpine grasslands ecosystem services. We added N of different gradients to test the effects of soil acidification, soil eutrophication, and phosphorus limitation independently, and interactively on the multifaceted plant richness and evenness in both an alpine meadow and an alpine steppe of the QTP. We found that all the p-value of taxonomy diversity, functional diversity and phylogenetic diversity were >0.05 and values of R2 of fixed factors by nitrogen addition gradients was low (<0.10). In contrast to the alpine steppe, diversity of alpine meadow is more sensitive to soil factors than alpine steppe. Soil acidification caused by nitrogen deposition changed taxonomic evenness (p < 0.05), while eutrophication associated with nitrogen deposition altered taxonomic richness and phylogenetic evenness (p < 0.05) in the alpine meadow and functional richness (p < 0.05) in the alpine steppe. These findings suggest that the effects of N deposition on the multifaceted plant diversity (taxonomic, functional and phylogenetic diversity) varied with N deposition gradients and ecosystem types. Rational adaptation and mitigation techniques should be considered for different types of alpine grasslands on the QTP according to their different responses to the nitrogen deposition gradients in the future.

Effects of simulated N deposition on photosynthesis and productivity of key plants from different functional groups of alpine meadow on Qinghai-Tibetan plateau.

Nitrogen (N) deposition may alter physiological process of plants in grassland ecosystem. However, little is known about the response mechanism of individual plants in alpine regions to N deposition. We conducted a field experiment, and three treatments including 0 kg Nha-1year-1 (CK), 8 kgNha-1year-1 (Low N), and 72 kg N ha-1 year-1 (High N) were established to simulate N deposition in alpine meadow of Qinghai-Tibetan plateau. Our objectives were to determine the influence of N deposition on photosynthesis of different functional types of herbage species in alpine meadow, and finally characterize the links of plant productivity and photosynthesis with soil nutrients. The results showed that responses of alpine plants were species-specific under N deposition. Compared with grass species Agropyron cristatum and forb species Thalictrum aquilegifolium, the sedge species Carex melanantha was much more sensitive to N deposition; a lower N load (8 kgNha-1year-1) can cause a negative effect on its photosynthesis and productivity. Additionally, N deposition can promote plant N uptake and significantly decreased the C (carbon)/N (nitrogen) ratio. Compared with CK and low N deposition, high N deposition inhibited the photosynthesis and growth of the forb species Thalictrum aquilegifolium and sedge species Carex melanantha. In all three functional types of herbage species, the grass species A. cristatum tended to show a much higher photosynthetic capacity and better growth potential; thus, suggesting that grass species A. cristatum will be a more adaptative alpine plants under N deposition. Our findings suggested that plant photosynthetic responses to N deposition were species-specific, low N deposition was not beneficial for all the herbage species, and N deposition may change plant composition by the differential photosynthetic responses among species in alpine grassland. Plant composition shift to grass-dorminant in alpine regions might be attributed to a much higher photosynthetic potential and N use efficiency of grass species.

Effects of Warming and N Deposition on the Physiological Performances of Leymus secalinus in Alpine Meadow of Qinghai-Tibetan Plateau.

Warming and Nitrogen (N) deposition are key global changes that may affect eco-physiological process of territorial plants. In this paper, we examined the effects of warming, N deposition, and their combination effect on the physiological performances of Leymus secalinus. Four treatments were established in an alpine meadow of Qinghai-Tibetan plateau: control (CK), warming (W), N deposition (N), and warming plus N deposition (NW). Warming significantly decreased the photosynthetic rate (Anet ), stomatal conductance (gs ), intercellular CO2 concentration (Ci ), and transpiration rate (Tr ), while N deposition and warming plus N deposition significantly increased those parameters of L. secalinus. Warming significantly increased the VPD and Ls , while N deposition and warming plus N deposition had a significant positive effect. Warming negatively reduced the leaf N content, Chla, Chlb, and total Chl content, while N deposition significantly promoted these traits. Warming, N deposition, and their combination significantly increased the activity of SOD, POD, and CAT. Besides, warming and warming plus N deposition significantly increased the MDA content, while N deposition significantly decreased the MDA content. N deposition and warming plus N deposition significantly increased the Rubisco activity, while warming showed no significant effect on Rubisco activity. N deposition and warming plus N deposition significantly increased the Fv/Fm, ΦPSII, qP, and decreased NPQ, while warming significantly decreased the Fv/Fm, ΦPSII, qP, and increased NPQ. N deposition strengthened the relations between gs , Chl, Chla, Chlb, Rubisco activity, and Anet . Under warming, only gs showed a significantly positive relation with Anet . Our findings suggested that warming could impair the photosynthetic potential of L. secalinus enhanced by N deposition. Additionally, the combination of warming and N deposition still tend to lead positive effects on L. secalinus.