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It can provide a basis for decision making for the conservation and sustainable use of forest ecosystems in mountains to understand the stoichiometric properties and nutrient allocation strategies of major tree species. However, the plant nutrient allocation strategies under different environmental gradients in forest systems of arid and semi-arid mountains are not fully understand. Therefore, three typical regions in the Qilian Mountains on the eastern edge of the Qinghai-Tibet Plateau were selected based on precipitation and temperature gradients, and the stoichiometric characteristics and nutrient allocation strategies of Qinghai spruce (Picea crassifolia) of the dominant tree species under different environmental gradients were investigated. The results showed that (1) the stoichiometric characteristics of plant tissues were different in the three regions. (2) The importance of each tissue in the plant nutrient allocation varied in different regions, showing that the plant roots are more important in the warm-wet region, while the plant leaves, branches and trunks are more important in the transition and hot-dry regions. (3) The influencing factors affecting plant nutrient allocation strategies were inconsistent across regions, which showed that plant nutrient allocation strategies in the warm-wet and transition region were mainly influenced by soil factors, while they were more influenced by climatic factors in the hot-dry region. The patterns of plant nutrient allocation strategies and drivers under different environmental gradients could help us better understand the ecological adaptation mechanism and physiological adjustment mechanism of forest ecosystem in mountains. [ABSTRACT FROM AUTHOR]

Understanding the resource allocation strategies of dominant conifer species in mountain forest ecosystem can provide decision-making basis for mountain ecosystem conservation and sustainable use. However, the resource allocation trade-offs of different tree species under the heterogeneous environments in arid and semi-arid mountains were not fully understood. Therefore, we analyzed the stoichiometric characteristics of two dominant conifer species in the Qilian Mountains at the eastern margin of the Tibetan Plateau with three altitudes and four typical regions to explore the resource allocation strategies of ecological adaptations of dominant tree species under different environmental gradients. The results showed that there were differences in stoichiometric characteristics for different tree species, altitudes and regions. 1) Compared with Qinghai spruce, Qilian juniper stored more nutrients in the underground part when it was resistant to drought. 2) Plants tended to invest more N and P to compensate for reduced physiological efficiency as altitude increases and temperatures decrease. 3) Different dominant conifer species stored more nutrients in the roots in the western section under drought stress. However, in the eastern section with favorable moisture and temperature they invested nutrients in the leaves and stems. 4) Mean annual temperature (MAT), mean annual precipitation (MAP) and soil water content (SWC) were the common controlling factors affecting stoichiometric characteristics of the different tree species, altitudes and regions. The findings of this study provided a theoretical basis for understanding of plant adaptation mechanisms at different spatial and temporal scales and species effects, as well as technical support for forest ecological control and restoration in ecologically sensitive and fragile areas. [Display omitted] • There were differences in stoichiometric characteristics for different tree species, altitudes and regions. • Qilian Juniper stored more nutrients in the underground part when it was resistant to drought. • The results of this study support the Temperature-Plant Physiology Hypothesis. • In the eastern section with favorable moisture and temperature they invested nutrients in the leaves and stems. • MAT, MAP and SWC were the common controlling factors. [ABSTRACT FROM AUTHOR]

• Coupling coordination degree can better evaluate the water-carbon function. • Water conservation trended downward, while carbon reserve trended upward. • The level of water-carbon coupling coordination on the Tibetan Plateau is low. • Climate is an important cause of the water-carbon coupling coordination level. • Ecological management should be adapted to water-carbon mechanism and dynamic tend. The Qilian Mountains on the eastern edge of the Tibetan Plateau are an important ecological security barrier in northwestern China and an extremely critical water-carbon conservation area. The water and carbon cycles are closely linked, and the water-carbon coupling process has become further complicated under global climate change and through the intensification of human activities. A better understanding of the impacts and potential mechanisms of water-carbon interactions is the key to improving the efficiency of water-carbon resource utilization. To rationalize the relationship between water and carbon, we used data from statistical almanacs, land use, DEM and various climatic elements to estimate the water-carbon nutrition in the Qilian Mountains from 2000 to 2020 based on the InVEST model and the Coupled Coordination Degree Model (CCDM) and to explore the coupling mechanism of water-carbon, spatial-temporal dynamics, and the influencing factors. The results showed that: 1). the average annual water and carbon storage in the Qilian Mountains are 63.21 × 108 m3 and 77.82 × 107 t, respectively, showing a spatial distribution pattern of high in the northeast and low in the southwest. The inter-annual changes in water (y =-0.451x+968.920) and carbon (y = 0.082x-87.808) showed different trends. 2). The annual average of the water-carbon coupling coordination degree of 0.280 in the Qilian Mountains was low in general, and the trends declined over time from 0.273 in 2000 to 0.264 in 2020. However, the spatial distribution was relatively clustered, and the spatial correlation improved from 0.69 in 2000 to 0.74 in 2020. 3). Precipitation, potential evapotranspiration and temperature were important elements driving water-carbon coupling. Among them, precipitation was significantly positively correlated with water-carbon coupling (r = 0.88), and potential evapotranspiration (r =-0.56) and temperature (r =-0.39) showed significant negative correlations with water-carbon coupling. This study can provide information for management and decision-making in carbon sequestration, water resource utilization, ecological protection and climate change, and promote the study of the spatial and temporal coupling functions of water and carbon with in the Qilian Mountains. Meanwhile, this study can provide a reference for the environmental management and protection of the Qilian Mountain ecosystem. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to establish an animal model of chronic pulmonary hypertension with a single-dose intraperitoneal injection of monocrotaline (MCT) in young Tibet minipigs, so as to enable both invasive and noninvasive measurements and hence facilitate future studies. Methods: Twenty-four minipigs (8-week-old) were randomized to receive single-dose injection of 12.0 mg/kg MCT (MCT group, n = 12) or placebo (control group, n = 12 each). On day 42, all animals were evaluated for pulmonary hypertension with conventional transthoracic echocardiography, right heart catheterization (RHC), and pathological changes. Findings of these studies were compared between the two groups. Results: At echocardiography, the MCT group showed significantly higher pulmonary arterial mean pressure (PAMP) compared with the controls (P<0.001). The pulmonary valve curve showed v-shaped signals with reduction of a-waves in minipigs treated with MCT. In addition, the MCT group had longer pulmonary artery pre-ejection phases, and shorter acceleration time and ejection time. RHC revealed higher mean pulmonary arterial pressure (mPAP) in the MCT group than in the control group (P<0.01). A significant and positive correlation between the mPAP values and the PAMP values (R = 0.974, P<0.0001), and a negative correlation between the mPAP and ejection time (R = 0.680, P<0.0001) was noted. Pathology demonstrated evidence of pulmonary vascular remodeling and higer index of right ventricular hypertrophy in MCT-treated minipigs. Conclusion: A chronic pulmonary hypertension model can be successfully established in young minipigs at six weeks after MCT injection. These minipig models exhibited features of pulmonary arterial hypertension that can be evaluated by both invasive (RHC) and noninvasive (echocardiography) measurements, and may be used as an easy and stable tool for future studies on pulmonary hypertension. [ABSTRACT FROM AUTHOR]