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Background: Understanding the stoichiometric characteristics and nutrient allocation strategies of dominant tree species in montane forest systems can provide a basis for decision-making in relation to montane system management. Therefore, according to precipitation and temperature gradients, we selected three typical areas in the Qilian Mountains on the eastern margin of the Qinghai-Tibet Plateau to analyse the spatial relations of plant-soil stoichiometric characteristics and nutrient allocation strategies of plant tissues for Qinghai spruce (Picea crassifolia) along different environmental gradients. Results: 1) The plant and soil stoichiometric characteristics had similar spatial patterns. The C content of plants and soils tended to decrease with increasing latitude, and the N and P contents and the N:P ratio tended to increase with increasing latitude. 2) The stoichiometric characteristics of the plant tissues also interacted with each other and showed synergistic trade-offs. Nutrient allocation in the eastern section of the Qilian Mountains was similar to that in the western section, while more N and P in the plant stems were allocated to maintain plant growth in the relatively arid western Sect. 3) The nutrient allocation strategies in the plant tissues were mainly regulated by soil and climate. Conclusions: Information on plant-soil stoichiometric characteristics along different gradients can help us better understand the nutrient patterns and dynamics of forest ecosystems under arid and semiarid conditions at a wide geographic scale from the perspective of plant nutrient partitioning. [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]

• Effects of engineering enclosures on soil quality in alpine grasslands are evaluated. • PCA combined with minimum data set is used to explore the soil quality change. • Soil quality index are built to assess soil quality with different enclosure years. • Long-term engineering enclosures improve soil quality of alpine grasslands. The soil quality assessment is the basis for evaluating the soil quality restoration status of degraded grassland and improving soil management in the enclosure areas. However, the evaluation of the effects of different long-term ecological engineering enclosures on soil quality in alpine grassland areas is still lacking. This study took soil samples of alpine grassland from the Tibet Plateau to examine the soil quality of alpine grassland and analyze the main influencing factors of soil quality under different enclosure years. Based on the soil samples from different and corresponding control plots for 10, 11, and 12 years, principal component analysis was used to screen the minimum data set (MDS) of the 12 physical and chemical properties of the soil samples. The soil quality index (SQI) was constructed to quantitatively evaluate the soil quality by the MDS with different closure years. Results show: (1) The respective grades of the soil fertility levels of nitrogen in the sample plots fenced for 10, 11, and 12 years were 4, 5, and 5. The soil fertility level of the other indicators was grade 6. (2) The 12 soil indicators had medium and low degrees of variation. Only the available phosphorus was at a strong variation level in the sample plots for 12 years. (3) The soil quality in the different enclosure years compared with the corresponding control plots became better. The different enclosure years indicated SQI (0.59 ± 0.11) of 10 years > SQI (0.50 ± 0.04) of 12 years > SQI (0.44 ± 0.05) of 11 years. (4) The MDS of soil quality assessment was composed of total nitrogen, total potassium, silt and total porosity. Compared with the full data set, the MDS could better replace the full data set for soil quality assessment (P < 0.01). This study found that the long-term ecological engineering enclosures have improved the soil quality of alpine grasslands. Total nitrogen and total potassium, total potassium and silt, and total potassium and silt were the main factor affecting the soil quality in 10, 11 and 12 enclosure years, respectively. [ABSTRACT FROM AUTHOR]