The response of radial growth to climate and the climate sensitivity of tree growth at different ages in different drought conditions are essential for predicting forest dynamics and making correct forest management policies. In this study, we analyzed the growth responsiveness of Picea crassifolia Kom. to climate and explored the relationship between age and climate sensitivity of radial growth at the individual tree scale in the wetter eastern area and drier western area of the Qilian Mountains. Pearson correlation coefficients were calculated between the chronology of each tree and climatic factors to examine the climate-growth relationships. Linear fitting, quadratic polynomial fitting and exponential fitting were used to test the relationships between age and mean sensitivity, standard deviation and radial growth’s response to climate. Trees in the wetter eastern area showed a weaker response to climate than those in the drier western area and were significantly correlated with precipitation and mean temperature in the previous and current mid-late summer. Trees in the drier western area were mainly limited by precipitation of the previous August, the current May and June, as well as limited by temperature in the previous and current early-middle summer. In the wetter area, the younger trees were more sensitive to both precipitation and temperature than the older trees. In the drier area, younger/older trees showed a stronger sensitivity to precipitation in the current August and September/May, whereas trees 120–140 years old showed a stronger correlation with temperature factors in the summer. It was determined that mature trees in the drier area were more strongly influenced by the climate, especially in the context of increasing temperature. These trees should be paid special attention in forest management.

The climate changed from warm-dry to warm-wet during the 1960s in northwest China. However, the effects of climate change on the response of radial growth from different age-class trees have been unclear. We assessed the age-effect radial growth responses in three age-classes (ml-old: ≥200 years, ml-middle: 100–200 years and ml-young: <100 years) of Schrenk spruce (Picea schrenkiana Fisch. et Mey.) in the eastern Tianshan Mountains. The primary conclusions were as follows: the developed chronologies of the three age-class trees contained significant climate information and exhibited high similarity as shown by calculating the statistical parameter characteristics and Gleichlaufigkeit index. The three age-class trees were consistent for annual variation trends of radial growth under climate change, showing similar fluctuations, tree-ring width chronology trends, time trends of cumulative radial growth, and basal area increment. In addition, the old and middle trees were found to be more sensitive to climate variability by analyzing Pearson correlations between radial growth from three age-class trees and climate factors. As a result, the drought caused by reduced total precipitation and higher mean temperature was a limiting factor of tree radial growth, and the trees with ages of up to 100 years were more suitable for studies on the growth-climate relationships. Thus, the studies on age-effect radial growth responses of Schrenk spruce can help not only in understanding the adaptive strategies of different-age trees to climate change, but also provide an accurate basis for climate reconstruction.

Environmental heterogeneity in temperature, moisture, and soil fertility caused by elevation gradients can affect the trade-offs in the survival strategies of tree species. There is uncertainty about the allocation of resources to different tissues of trees in response to the elevation gradient with respect to carbon (C), nitrogen (N), and phosphorus (P). Here, the C, N, and P content of leaves, branches, trunks, and thick and fine roots of Picea crassifolia (Qinghai spruce) and their stoichiometric changes across three different elevations were investigated in the Qilian Mountains. We found that N:P of Qinghai spruce was <14 in all tissues at most elevations, indicating that Qinghai spruce was more susceptible to N limitation. Meanwhile, the N content and N:P of Qinghai spruce each were significantly negatively correlated with temperature (p < 0.05), and its P content was lower at high elevation. The contribution of soil–climate interactions on the elevation gradient to each tissue type was 34.02% (leaves), 16.84% (branches), 67.78% (trunks), 34.74% (thick roots), and 49.84% (fine roots), indicating that interacting climate and soil factors on the elevation gradient predominately drove the C, N, and P content and stoichiometry variation in each tissue type of Qinghai spruce trees. The results of this study clarify that the elevation gradient regulates the elemental content and resource allocation in Qinghai spruce, providing basic data and an important timely reference for future forest management in the regions where coniferous trees grows. These findings also help improve our understanding of elevational patterns of forest ecosystem stoichiometry in arid and semiarid regions.

The upper Yellow River Basin is an important ecological security barrier and a water conservation area in northwest China. The sustainability of its water yield services has generated much concern and debate. Spatial and temporal patterns of water yield factors are considered to be important scientific data. Therefore, the climate and land data of the upper Yellow River Basin in Maqu County are studied. Water yield for the period 1990–2020 was estimated using the water yield module in the InVEST model. Impacts and contribution weights of climate and land use/cover change on regional water yield were also quantified under 12 scenarios. The results indicate that (1) the average water yield in Maqu County has fluctuated and increased in the past 30 years. The increase in rainfall was more pronounced than the increase in potential evapotranspiration. Grassland areas continue to increase and unutilized land areas continue to decrease. (2) The average water yield for different types of land use during this period also varied. It showed grassland > unutilized land > forest > construction land > waterbody > cropland. (3) Climate change has a greater impact on water yield in Maqu County and further increases its contribution to regional water yield. The impact of land use/cover change was smaller and the contribution was smaller.

Water resources are the material basis for human social development. They play an essential role in human production and life. They are vital for the healthy growth of ecosystem services. The quantitative assessment of the water conservation (WC) function is of great significance to the management of regional ecosystems and the construction of ecological civilization. Gannan is an influential water supply area in the upper Yellow River Basin. Understanding the current status and future changes of its WC function can provide scientific support for the stable use and sustainable development of water resources in the upper Yellow River Basin; its ecological status is highly important. The present study quantitatively assesses the WC function of Gannan based on the InVEST model. It aims to explore the regional ecological compensation mechanism, enhance regional ecological regulation capacity and increase water supply by studying the trend in changes in the WC function and the influence mechanism. The results show that: (1) The overall trend in WC capacity in Gannan increased during the period 2000–2020. (2) The spatial distribution of WC in Gannan varies from year to year, but there is some similarity, showing a high degree in the southwest and a low degree in the northeast. (3) Climatic factors are the dominant factors underlying the spatial and temporal distribution of WC in Gannan. (4) The important areas of WC are located in the southwest and southeast of Gannan.