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In the presence of limited phosphorus (P) in terrestrial ecosystems, exploring how land use change (LUC) affects phosphatase enzyme activity and microbial communities is important for managing soil P, because microorganisms carry out the majority of P cycling in the soil through producing phosphatase enzymes. In this study, we explored the impact of LUC on P availability, phosphatase enzyme, the abundance of phosphatase-encoding genes, and microorganisms. We collected 168 soil samples at soil depths of 0–20 cm and 20–40 cm from seven sampling sites, each of which represented by four different land uses: artificial forests (AF), farmlands (FL), natural forests (NF), and shrubland (SL). We analyzed phosphatase-encoding genes and microbes from metagenome datasets. Results indicated that P availability substantially increased following NF to FL conversion. In contrast, phosphatase enzyme activity significantly decreases when NF is converted to different land uses, due to the decline of soil organic carbon (SOC), moisture content (MC) and total nitrogen (TN). We have also detected 13 P solubilizing and mineralizing genes. The phoD and gcd were the dominant mineralizing and solubilizing genes, respectively. Farmland had higher gcd gene abundance, while NF had significantly higher phoD gene abundance. The gcd gene abundance were mainly governed by pH and total P, whereas pH and available P were the primary factors controlling phoD gene. MC, SOC and TN regulated other genes detected in this study. With regard to the dominant gcd-harboring phyla, Acidobacteria, Proteobacteria, Bacteroidetes and Gemmatimonadetes were the dominant, while Proteobacteria, Acidobacteria, Actinobacteria, and Candidatus_Rokubacteria were the dominant phoD-harboring phyla. The majority of gcd and phoD-harboring microorganisms were primarily controlled by pH, available P and total P. However, some phyla also regulated by MC, SOC, and TN. In general, our findings suggested that LUC significantly alters phosphatase enzymes and the abundance of phosphate-encoding genes and microbes. These changes have significant implications for soil P cycling.

Land use change has a significant effect on soil nutrient cycling. However, data on soil phosphorus (P) fractions following land use change are scarce, especially in the subalpine ecosystem of China. Here, we investigated the influence of land use change on soil P fractions in the subalpine ecosystem of the Southeast margin of Qinghai-Tibet Plateau, Southwest China. In total, we took 168 soil samples from four land use types, including natural forest (NF), artificial forest (AF), farmland (FL), and shrubland (SL), at a depth of 0–20 and 20–40 cm. Phosphorus fractions were determined using Hedley fractionation procedures. The results showed that land use change and soil depths had a significant impact on the status of P fractions (p≤0.05). Organic P (Po) fraction significantly decreased following land use change but varied among land use types. Farmland soils showed the highest losses of Po fractions ranging from 23 to 54%, due to organic material reduction. Total P also decreased by 9.63% after the conversion of NF to AF (p≤0.05). Conversely, total P and inorganic P (Pi) fractions were significantly higher in FL soil than in other land uses (p≤0.05), likely due to the application of chemical fertilizers. Organic P extracted by NaOH was the dominant total Po fraction in all land uses, accounting for 63.3 to 73.14% of total Po, while Pi extracted by HCl was the dominant Pi fraction in FL soil, accounting for 42.74% of total P. Soil moisture content, pH, soil organic carbon (SOC), total nitrogen (total N), and calcium were key soil properties governing soil P fractions. Organic P fractions were strongly positively correlated with SOC and total N, implying that soil organic matter (SOM) plays a vital role in maintaining the soil P reserves. Generally, our findings shed light on how land use changes significantly affected P fractions. This result may have substantial implications for soil P management to maintain soil P reserves by reducing SOM losses.

Changes in global climate patterns and human activity have the potential to alter key components of terrestrial ecosystems, such as the productivity of grasslands. The Qinghai–Tibetan Plateau is one of the most sensitive regions and is affected by substantial climatic changes and intensive human activities. In this study, the spatial distribution and temporal variation in grassland productivity from 1980 to 2015 were examined using the proxy net primary productivity (NPP). Trend and redundancy analyses were used to determine the contributions of driving indicators (climate change and human interventions) to the changes in NPP. During the past 35 years, the trend in grassland productivity across the Qinghai–Tibetan Plateau was one of significant increasing trend (increase of 1.08 g C/m2/year). A trend of increase of NPP was observed for approximately 82.79% of the total grassland area, with most of this area distributed in the central region. However, a trend of degradation was observed in the northwestern region of the plateau. The primary reason for the complex spatial pattern and distribution of vegetation productivity was unsynchronized changes in temperature and precipitation. Therefore, temperature and water content (precipitation and melting water) were not good indicators for trends in NPP in this area. Moreover, although variation in rainfall and temperature explained 9.75% of the variation in grassland productivity, the effects of human interventions were greater (23.48%). According to the redundancy analysis, the positive contribution of ecological restoration projects (reducing the negative effects of humans) was the most important indicator in the entire study area, followed by temperature (conducive to vegetation growth and acceleration of melting glaciers). Most conservation policies produced significant positive effects on the restoration of grasslands and prevented or reversed the degradation of grasslands on the plateau. Under increases in temperature and moisture on the Qinghai–Tibetan Plateau, the ecological restoration policies in conservation areas demonstrate an “increasing trend in grassland productivity.”

The interactive effect of soil cooling and nitrogen (N) addition can accurately simulate climatic and anthropogenic effects on terrestrial and other land-based ecosystems, but direct empirical measurements on the effects of cooling and N addition on soil carbon (C) and N are lacking. Hence, transplanting soils into colder regions was used to evaluate the effects of cooling and N addition on soil C and N. We used PVCs of 30 cm in height and 8 cm in diameter to extract soil samples. Soil C and N were significantly (P < 0.05) increased by transplanting soils into colder regions. In contrast, cooling has insignificantly (P > 0.05) increased the soil dissolved organic C (DOC) and dissolved organic (DON), but the effect was negatively significant on soil pH compared to the C/N ratio. Similarly, N addition significantly increased the measured soil N stock. However, the effect was negatively significant on soil pH (P < 0.05) compared to the C/N ratio (P > 0.05). Nevertheless, the interaction of cooling and N addition did not affect the soil C and N storage. A similar effect was observed on the soil DOC and DON. The results presented here illustrate that transplanting soils into colder regions and N deposition has perfectly simulated the effects of climate-forcing factors on soil C and N storage in terrestrial and other land-based ecosystems. Accordingly, this study suggests that low temperatures have stimulated the accumulation of the measured soil organic and dissolved properties, but the effect is less consequential when low temperature interacts with N addition in high-elevation areas where ecosystem structures and functions are limited by temperature and may serve as a baseline for future research on land feedbacks to the climate system., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)