The crown closure of Platycladus orientalis forests has a wide-ranging impact on vegetation and soil, thereby affecting the overall functioning of the ecosystem. There is limited research on the effects of the Platycladus orientalis forest crown closure on changes in community plant functional traits, and their interactions are not yet clear. Therefore, we investigated 50 plots of different types of Platycladus orientalis crown closure, and we measured the functional traits of nine shrub species and 68 herb species in 50 plots under five different densities of Platycladus orientalis forests in the Loess Plateau. The consequence of Pearson’s correlation analysis showed significant positive correlations between LC and LTD, LN and LP, LN and LNP, LN and LV, LN and H, LP and LV, LP and H, and SLA and LV (p < 0.05). LC was significantly negatively correlated with LP, LC with SLA, LC with LV, LN with LTD, LP with LNP, LP with LTD, and LTD with H (p < 0.05). Only the soil phosphorus content (SP) and soil water content (SWC) showed a significant positive correlation with multiple plant functional traits. The crown closure of Platycladus orientalis forests increased significantly, as did the plant functional features. Changes in the Platycladus orientalis forest crown closure significantly increased the LC, LV, LN, LP, and SLA in plant functional traits. An increase in Platycladus orientalis forest crown closure significantly increased the soil organic carbon (SC), soil phosphorus content (SP), soil nitrogen content (SN), soil water content (SWC), field capacity (FC), and soil porosity (PO). Based on a structural equation model, we found that, while changes in the Platycladus orientalis forest crown closure did not directly affect plant functional traits, they could indirectly influence these traits through soil factors, primarily the soil water content (SWC) and soil phosphorus content (SP) (p < 0.05). Additionally, the mechanisms of the Platycladus orientalis forest crown closure’s impact on different functional traits vary. The research results provide scientific elements for the ecological restoration of Platycladus orientalis forests on the Loess Plateau.

Soil moisture is an important component of the soil–vegetation–atmosphere terrestrial hydrological cycle and is an important factor affecting terrestrial ecosystems. In the context of extensive vegetation greening on the Tibetan Plateau (TP), it is important to investigate the effect of vegetation greening on soil moisture to maintain ecosystem stability and protect the sustainability of ecological restoration projects. To evaluate the effect of vegetation greening on soil moisture on the TP, the spatial distribution and trends of soil moisture and vegetation on the TP were analyzed using GIMMS NDVI data and ERA5 soil moisture data from 1982 to 2015. The effects of grassland NDVI, precipitation, and temperature on SM were also explored using multiple regression apparent and SEM. The main results are as follows: from 1982 to 2015, both grassland NDVI and SM showed a stable increasing trend. Precipitation was the most important factor influencing SM changes on the TP. In the context that vegetation greening is mainly influenced by temperature increase, vegetation plays a dominant role in SM changes in soil drying and soil wetting zones. In this paper, the climate–vegetation–soil moisture coupling mechanism of grasslands on the TP is investigated, and the related results can provide some theoretical references and suggestions for global ecosystem conservation and the sustainable development of ecological restoration projects.

Plant functional traits (PFTs) can reflect the response of plants to environment, objectively expressing the adaptability of plants to the external environment. In previous studies, various relationships between various abiotic factors and PFTs have been reported. However, how these factors work together to influence PFTs is not clear. This study attempted to quantify the effects of topographic conditions, soil factors and vegetation structure on PFTs. Four categories of variables were represented using 29 variables collected from 171 herb plots of 57 sites (from different topographic and various herb types) in Xindian SWDP. The partial least squares structural equation modeling showed that the topographic conditions and soil properties also have a direct effect on plant functional traits. Among the topographic conditions, slope (SLO) has the biggest weight of 0.629, indicating that SLO contributed the most to plant functional traits and vegetation structure. Among soil properties, maximum water capacity (MWC) contributes the most and is followed by soil water content (SWC), weighted at 0.588 and 0.416, respectively. In a word, the research provides new points into the quantification of the correlation between different drivers that may be important for understanding the mechanisms of resource utilization, competition and adaptation to the environment during plant recovery.

Runoff and sediment (RAS) are important indicators of soil erosion in a watershed, playing a significant role in the migration of surface material and landform development. Previous studies have extensively documented the effects of trees, shrubs, herbs, and soil on runoff and sediment during erosive rainfall; however, the precise interactions among these factors and their influence on RAS yield within the vegetation hierarchy remain unclear. Using the random forest algorithm and the structural equation model, this research aimed to quantify the interaction of numerous variables within diverse vegetation hierarchies and how they affect RAS, as well as to identify critical indicators that influence RAS. The structural equation model results show that the grass properties have a direct effect on soil properties, and the grass properties and soil properties both affect the canopy properties directly; the soil properties and canopy properties are the main factors influencing runoff and sediment directly. In addition, the grass properties could affect RAS by influencing the soil properties indirectly, and the soil properties could also affect RAS indirectly by influencing the canopy properties. Height difference (HD) between two layers of vegetation had the highest weight of 1.043 among the canopy variables, showing that HD has a substantial effect on RAS. Among the soil properties, soil bulk density and maximum field capacity have a significant impact on RAS. We conclude that canopy properties have the greatest impact on RAS. In the future, more Caragana microphylla Lam and Robinia pseudoacacia Linn plants should be planted to prevent soil erosion. This study provides a scientific basis for vegetation planting management and soil erosion control on the Loess Plateau.

Climatic warming advances the start of the growing season (SOS) and sequentially enhances the vegetation productivity of temperate forests by extending the carbon uptake period and/or increasing the growth rate. Recent research indicates that the vegetation growth rate is a main driver for the interannual changes in vegetation carbon uptake; however, the specific effects of an earlier SOS on vegetation growth rate and the underlying mechanisms are still unclear. Using 268 year-site PhenoCam observations in temperate forests, we found that an earlier SOS reduced the vegetation growth rate and mean air temperature during the green-up period (i.e., from the SOS to the peak of the growing period), but increased the accumulation of shortwave radiation during the green-up period. Interestingly, an earlier-SOS-induced reduction in the growth rate was weakened in the highly humid areas (aridity index ≥ 1) when compared with that in the humid areas (aridity index < 1), suggesting that an earlier-SOS-induced reduction in the growth rate in temperate forests may intensify with the ongoing global warming and aridity in the future. The structural equation model analyses indicated that an earlier-SOS-induced decrease in the temperature and increase in shortwave radiation drove a low vegetation growth rate. Our findings highlight that the productivity of temperate forests may be overestimated if the negative effect of an earlier SOS on the vegetation growth rate is ignored.