Yaxin Han

Canopy SPAD index is a practical indicator for evaluating the photosynthetic status and health of Malus sieversii, an endangered wild apple resource in Xinjiang. To develop a rapid and non-destructive monitoring approach, 255 canopy samples were collected across the flower fading stage, fruit stage, and fruit mature stage using synchronized UAV hyperspectral imaging and ground SPAD measurements. Spectral preprocessing, feature-band selection, regression modeling, and SHAP interpretation were evaluated using training-set optimization and independent test-set validation. SG-FD produced the strongest preprocessing response, with a maximum absolute correlation coefficient of 0.70. SiPLS reduced 220 effective bands to 84 wavelengths; subsequent CARS, GA, and SPA screening retained 28, 8, and 12 wavelengths, respectively. The SiPLS-CARS-based Transformer-LSTM model achieved the best performance, with R² = 0.91 and RMSE = 2.12 in training and R² = 0.86 and RMSE = 2.47 in testing. SHAP results indicated that red-edge wavelengths and visible sensitive bands contributed most to prediction. The proposed UAV hyperspectral and Transformer-LSTM framework provides an interpretable proof-of-concept method for canopy SPAD index estimation in Malus sieversii and supports non-destructive monitoring of wild fruit forest health.

Understanding how soil arthropod communities respond to nutrient enrichment is important for assessing grassland ecosystem health, but such knowledge remains limited for degraded Sophora alopecuroides grasslands. To address this gap, a two-year field experiment was conducted in the Tuhulusu grassland (Xinjiang, China) with four treatments: nitrogen (N) addition, phosphorus (P) addition, combined N and P (NP) addition, and an unamended control (CK). Soil arthropod communities and environmental variables were monitored during the flowering, maturity, and senescence stages of S. alopecuroides. Across all treatments, three taxa—Oppiidae, Hypoaspidae, and Rhagidiidae—remained dominant, indicating wide ecological tolerance. Nutrient addition significantly altered arthropod individual density (response variable) and soil properties, including total phosphorus, available phosphorus, nitrate−N, ammonium−N, and pH (all p < 0.001), and these effects were strongly linked to plant phenology. The dominance, evenness, and Shannon diversity indices ranked as NP > CK > P > N. The key environmental drivers varied by treatment: total phosphorus and soil moisture under N addition, soil moisture under P and NP addition, and pH and electrical conductivity under CK. Collectively, these findings provide evidence that soil arthropod communities in S. alopecuroides grasslands are sensitive to nutrient enrichment in a phenology−dependent manner, with soil moisture content emerging as a critical limiting factor under nutrient−added conditions.

Grassland degradation, exacerbated by climate change and anthropogenic disturbances, poses a substantial barrier to ecological restoration, largely due to the invasion of toxic weeds. In the degraded grasslands of the Ili River Valley, Xinjiang, Sophora alopecuroides has emerged as the dominant toxic species; yet, its expansion mechanisms and sensitivity to management interventions remain poorly understood. This study utilized a three-year (2023–2025) field experiment to evaluate the impacts of nitrogen addition (N), mowing (M), and their combination (NM) on the stoichiometric characteristics and homeostasis of the plant–soil system. The results demonstrated that while M suppressed aboveground biomass, it facilitated the accumulation of root carbon (RC) and phosphorus (RP). Nitrogen enrichment significantly lowered soil C:N and C:P ratios, thereby alleviating phosphorus limitation. Crucially, the NM treatment effectively counteracted N-induced weed proliferation and mitigated M-induced biomass reductions. Analysis of stoichiometric homeostasis revealed that NM optimized plant adaptive strategies, maintaining strict homeostasis for RC and RP (H > 4) while preserving the sensitivity of the root N:P ratio of S. alopecuroides (RN:P). Structural equation modeling further indicated that soil C:P and N:P indirectly regulated total biomass by modulating the root C:P ratio of S. alopecuroides (RC:P). Consequently, stoichiometric coupling within the plant–soil system is essential for maintaining ecosystem functions. Integrated management (NM) optimizes soil nutrient balance and harnesses compensatory growth to suppress weed expansion, providing a robust scientific framework for the restoration of S. alopecuroides-invaded grasslands.