Afforestation brings lots of water‐related benefits, including reducing soil erosion and improving water conservation, simultaneously; it is considered to be a land use activity, which threatens water resources security. Characterizing the response of soil moisture to revegetation is important for the sustainability of water and plants on the Loess Plateau of China. In this study, we conducted a meta‐analysis of 1,262 observations from 66 published studies to evaluate the effect of land use on the soil moisture of forest, shrubland, and grassland regions at a depth of 5 m in different ecological zones of the Loess Plateau. The results indicated that (a) Soil moisture content (SMC) decreased after land use conversion in all three ecological zones and was inconsistent among different soil layers. (b) Except for other grassland species, changes in the response size for soil moisture were not significant among any tree species, including Pinus tabuliformis, Robinia pseudoacacia, other forest species, Caragana korshinskii, other shrubland species, and Medicago sativa. (c) Soil moisture changes varied with different restoration types and ages. (d) The change in response to precipitation was not significant, whereas the change in response to temperature was significant. In addition, the responses of the initial soil moisture levels exhibited a negative correlation with revegetation. These results indicate that it is vital for scientific afforestation in the Loess Plateau to complement local climate conditions and soil properties.

Background: Under the background of drought and nitrogen deposition, global climate change is changing the supply of resources and environmental conditions that are crucial to plant growth, and plants respond to climate change by environmentally induced phenotypic changes. Aims: The objective of this study was to assess the differences in the plasticity responses of the morphological, photosynthetic, fluorescence and antioxidant parameters of Robinia pseudoacacia seedlings under water, nitrogen and phosphorus interaction conditions. Methods: We analyzed the above parameters of R. pseudoacacia seedlings using methods of morphological measurements, gas exchanges, fluorescence emission and antioxidant assays under two water levels (75% and 55% of field capacity), four nitrogen levels (no urea; 0.2 g kg−1, 0.4 g kg−1, 0.8 g kg−1), and two phosphorus levels (no superphosphate, 0.6 g kg−1). Results: The results showed that drought stress significantly reduced the morphological parameters, actual photochemical efficiency of photosystem II (ΦPSII), superoxide dismutase (SOD) activity, peroxidase (POD) activity and catalase (CAT) activity of R. pseudoacacia seedlings, and significantly increased nonphotochemical quenching (NPQ) and the malondialdehyde (MDA) content. Excessive application of nitrogen (N) fertilizer inhibited plant growth, and phosphorus (P) deficiency significantly weakened the positive effect of the high nitrogen treatment on morphological parameters under drought stress. The high nitrogen treatment effectively weakened the inhibitory effect of drought and phosphorus deficiency on chlorophyll formation. Proper N and P fertilizers increased the SOD, POD and CAT activities and decreased the MDA content under drought stress. The mean plasticity index of POD and CAT activities in response to water, nitrogen and phosphorus was the highest, which indicated that R. pseudoacacia seedlings can adapt to changes in water and nutrients mainly by adjusting their POD and CAT activities. Conclusions: These results may explain the better survival of R. pseudoacacia under the condition of limited water and nutrient resources, which is helpful for understanding the response mechanism of R. pseudoacacia to changes in environmental factors in the future. The results also provide scientific data and a theoretical basis for vegetation restoration and sustainable development of the regional ecological environment.