Lizhu Guo

Drought is becoming more frequent and severe under global climate change. Bouteloua dactyloides (Nutt.) (hereafter, B. dactyloides) is a dioecious, drought

Whether invasive species retain ancestral climatic niches or undergo niche shifts remains a central question in invasion ecology, directly affecting the reliability of risk predictions based solely on native-range data. We integrated ensemble species distribution models (SDMs) with the Centroid Shift, Overlap, Unfilling, and Expansion (COUE) framework and multivariate environmental similarity surface (MESS) analysis to quantify global invasion risk and climatic niche dynamics of Solanum rostratum across four major invaded regions: China, Australia, Eastern Europe, and Western Europe. The species exhibits a heat-dominated yet precipitation-constrained niche. Annual mean temperature and extreme heat were the principal limiting factors, whereas excessive precipitation imposed an upper threshold on habitat suitability. Cross-regional comparisons revealed a continuum of niche dynamics rather than a uniform invasion strategy, shaped by invasion history, environmental availability, and adaptive processes. Australian populations showed near-complete niche conservatism (Stability = 0.98), indicating long-term persistence within historical introduction limits. European populations displayed pronounced niche unfilling (Western Europe: Unfilling = 0.69), likely reflecting dispersal constraints and environmental heterogeneity. In contrast, Chinese populations exhibited substantial niche expansion (Expansion = 0.48), suggesting adaptive shifts into colder and drier climates beyond native conditions. These findings demonstrate that ignoring niche dynamics leads to systematic underestimation of invasion risk. We propose a region-specific assessment framework that explicitly incorporates dynamic niche processes, thereby improving predictive accuracy and informing precision management of invasive plants under ongoing global change.

The reintroduction of grassland plant species is widely used to restore degraded cropland, yet the species-specific effects on soil microbial diversity remain poorly understood. Understanding how individual plant species shape microbial communities is critical for improving restoration outcomes. To address this, we established experimental plots with 11 plant species on abandoned cropland and evaluated their impacts on soil bacterial diversity. Our results revealed marked variations in soil bacterial diversity across species. Richness indices (ACE and Richness) were positively correlated with soil total phosphorus (TP) and pH, while evenness indices (Simpson and Pielou) were negatively correlated with the proportion of water-stable aggregates (WSA). By classifying soil bacteria into ecological groups via co-occurrence network analysis, we found that bacterial diversity was positively correlated with the relative abundance of keystone and low-frequency taxa, but negatively correlated with peripheral taxa and other taxa. Further analysis indicated that stochastic processes following plant reintroduction promoted the emergence of low-frequency taxa, while deterministic processes contributed to a higher relative abundance of other taxa. Taken together, these findings suggest that species such as Elymus sibiricus (E. sibi) enhance soil bacterial diversity by shifting community assembly toward more stochastic processes, accompanied by an increase in low-frequency taxa and a reduction in the relative abundance of other taxa. Our results provide critical insights for selecting plant species that enhance microbial diversity for the restoration of abandoned cropland. Graphical Abstract Our study demonstrates a dual-pathway mechanism by which plant species regulate soil bacterial diversity: (i) by modifying soil properties (e.g., pH, TP, WSA), which filter the microbial community; and (ii) by modulating the abundance and assembly of key ecological groups within the microbial network. The selection of plant species determines the balance between these pathways, ultimately shaping the diversity outcome.

Sandbur [Cenchrus longispinus (Hack.) Fernald] is a major invasive weed in the agro-pastoral ecotone of northern China. It propagates via seeds encased in spiny burs. Each bur encloses a pair of seeds, and the larger M-type seeds germinate first, functioning as pioneer plants, while smaller P-type seeds remain dormant. Thus, the rapid germination of M-type seeds is pivotal for population sustenance. In this study, we investigated the transcription response involved in the germination of C. longispinusus M-type seeds during four stages (drying, imbibition, exposure, and sprouting). A total of 24,399 DEGs were identified by comparing two consecutive germination stages, with most DEGs found in the imbibition stage. GO enrichment analysis showed that the DEGs were mainly enriched in substance metabolic and regulatory processes. Correspondingly, KEGG enrichment analysis indicated that the functions of DEGs were significantly concentrated in secondary metabolite synthesis pathways, as well as substance and energy metabolic pathways. Notably, the expression of starch-and-sugar metabolism-related genes increased as germination progressed. Additionally, ABA synthesis-related genes were notably downregulated, while those regulating ABA catabolism were significantly upregulated. Moreover, GA synthesis-related genes were activated, especially in the imbibition stage, with nine GA20ox genes highly expressed. These research findings help us gain a deeper understanding of the seed germination mechanism of C. longispinus.

Xanthium spinosum (X. spinosum) is a highly invasive weed native to South America and distributed in 17 provinces (municipalities) of China. It has severely negative influences on ecosystems, agriculture, and husbandry. However, few studies have reported on the impact of human activity and climate change on the future distribution and centroid shift of X. spinosum. This study aimed to investigate the potential geological distribution of X. spinosum in China, as well as the distribution pattern, centroid shift, and key environmental factors influencing its distribution, under four future climate scenarios (SSP1-26, SSP2-45, SSP3-70, and SSP5-85) based on the biomod2-integrated model. The results indicated that the suitable habitats for X. spinosum would expand in the future, mainly in Inner Mongolia, Northeast China, and the plateau regions (e.g., Xinjiang and Xizang). Under future climate scenarios, the centroid would shift toward the northwest or northeast part of China, with the SSP2-45-2050s scenario showing the maximum shift distance (161.990 km). Additionally, the key environmental variables influencing the distribution of X. spinosum, including human impact index, bio5, bio7, and bio12, were determined, revealing that most of them were related to human activities, temperature, and precipitation. This study enhances the understanding of the influence of human activity and climate change on the geographic range of X. spinosum. It provides references for early warning and management in the control of X. spinosum.

Xanthium spinosum (X. spinosum) is a highly invasive weed native to South America and distributed in 17 provinces (municipalities) of China. It has severe negative influences on ecosystems, agriculture, and husbandry. However, few studies have reported on the impact of human activity and climate change on the future distribution and centroid shift of X. spinosum. This study aimed to investigate the potential geological distribution of X. spinosum in China, as well as the distribution pattern, centroid shift, and key environmental factors influencing its distribution, under four future climate scenarios (SSP1-26, SSP2-45, SSP3-70, and SSP5-85) based on the biomod2 integrated model. The results indicated that the suitable habitats for X. spinosum would expand in the future, mainly in Inner Mongolia, Northeast China, and the plateau regions (e.g., Xinjiang and Xizang). Under future climate scenarios, the centroid would shift toward the northwest or northeast part of China, with the SSP2-45-2050s scenario showing the maximum shift distance (161.990 km). Additionally, the key environmental variables influencing the distribution of X. spinosum, including human impact index, bio5, bio7, and bio12, were determined, revealing that most of them were related to human activities, temperature, and precipitation. This study enhanced the understanding of the influence of human activity and climate change on the geographic range of X. spinosum. It provided references for early warning and management in the control of X. spinosum.

Soil bacterial diversity often shows different trends due to changes in dominant plant species. However, the potential key drivers of processes that reveal bacterial diversity per se have not been clearly elucidated. We established a field experiment with 9 native grassland species and assessed the relationship between soil bacterial diversity and ecological taxa classified by network construction. A co-occurrence network of 1065 points and 10023 edges, among 9 native grasses, was established to classify microbial ecological taxa. The results showed that the relative abundance of ecological taxa classified as peripherals, which is influenced by soil urease activity, inhibited bacterial diversity. Conversely, the relative abundance of specific taxa directly controlled by plants was positively related to bacterial diversity. Further, the composition of peripherals was not affected by soil physicochemical properties, while the composition of specific taxa was affected by NO₃^-, TP, AP, SU, TC and AK. The composition of peripherals and specific taxa have different responses to soil properties due to their sensitivity to environmental changes. Our findings reveal that plant-dominated bacterial diversity is closely linked to the abundance of peripheral and specific taxa. Understanding these mechanisms may provide a new insight in to the management of grassland soil microbes through the selection of grass species following disturbance and subsequent restoration.

Plant-microbial interactions (PMI) play a crucial role in plant growth, fitness and productivity, primarily through the mutualism and antagonism interactions between plants and soil microorganisms. The colonization of arbuscular mycorrhizal (AM) fungi and pathogen are often used to speculate on the effects of microorganisms on plant growth, i.e. plant-microbial interactions (PMI). However, empirical studies demonstrate the relationship between AM fungi or pathogen and PMI effects remains limited, especially under different biotic and abiotic conditions. Here, we evaluated the colonization rates of AM fungi and pathogen across 13 grassland species under individual or communal conditions, in both overgrazed and restored soil. Furthermore, we investigated the relationship between AM fungi or pathogen and PMI. Our results showed that forbs exhibited significantly higher rates of AM fungal colonization compared to graminoids in community condition and overgrazed soil while graminoid roots showed higher pathogen infestation compared to forbs in individual condition and overgrazed soil. Generally, there was a positive correlation between PMI and AM fungal colonization but a negative correlation between PMI and pathogen disease. The PMI of graminoids exhibited a negative correlation with pathogen disease in individual condition and overgrazed soil, but showed no correlation with AM fungal colonization. On the other hand, the PMI of forbs showed a positive correlation with AM colonization in both restored and overgrazed soil, as well as in both individual and community experiments. However, there was no correlation between PMI of forbs and pathogen disease. The PMI of graminoids and forbs in grassland ecosystems can be driven by distinct soil microorganisms. These insights enable us to better understand how soil mutualists and pathogen mediate PMI effects on plant growth, with implications for grassland management and restoration.

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] has become the most widely cultivated warm-season turfgrass in northern China because of its low-maintenance requirements. Nitrogen (N) can be applied to plants in a range of formulations. However, preference of nitrogen uptake and the effects of N form on plant growth and nitrogen accumulation has not been established in buffalograss. In this study, we evaluated the effects of different inorganic nitrogen forms (NO₃⁻-N, NH₄⁺-N, and NO₃⁻-N: NH₄⁺-N = 1:1) on growth and nitrogen accumulation in buffalograss seedlings. Results showed that supply of three N forms significantly increased buffalograss seedlings growth, biomass, and N contents of all plant organs compared with the seedlings receiving free nitrogen. Plants achieved better growth performance when they received nitrate as the sole N source, which stimulated stolon growth and increased the biomass of ramets, spacers, and aboveground and total plant biomass, and also allocated more biomass to ramets and more N to spacers. Meanwhile, those plants supplied with the treatment +NH₄NO₃ displayed a significantly greater N content in the ramet, ¹⁵N abundance, and ¹⁵N accumulation amount in all organs. These data suggest NO₃⁻-N supplied either singly or in mixture increased vegetative propagation and thus facilitates buffalograss establishment. However, applications of ammonium caused detrimental effects on buffalograss seedlings growth, but +NO₃⁻ could alleviate NH₄⁺-induced morphological disorders. Thus, recommendations to increase vegetative propagation and biomass accumulation in buffalograss seedlings should consider increasing NO₃⁻-N in a fertility program and avoiding applications of nitrogen as NH₄⁺-N.

Plant leaf stoichiometry reflects its adaptation to the environment. Leaf stoichiometry variations across different environments have been extensively studied in grassland plants, but little is known about intraspecific leaf stoichiometry, especially for widely distributed species, such as Stellera chamaejasme L. We present the first study on the leaf stoichiometry of S. chamaejasme and evaluate its relationships with environmental variables. S. chamaejasme leaf and soil samples from 29 invaded sites in the two plateaus of distinct environments [the Inner Mongolian Plateau (IM) and Qinghai-Tibet Plateau (QT)] in Northern China were collected. Leaf C, N, P, and K and their stoichiometric ratios, and soil physicochemical properties were determined and compared with climate information from each sampling site. The results showed that mean leaf C, N, P, and K concentrations were 498.60, 19.95, 2.15, and 6.57 g kg⁻¹; the average C:N, C:P, N:P, N:K and K:P ratios were 25.20, 245.57, 9.81, 3.13, and 3.21, respectively. The N:P:K-ratios in S. chamaejasme leaf might imply that its growth is restricted by K- or K+N. Moreover, the soil physicochemical properties in the S. chamaejasme-infested areas varied remarkably, and few significant correlations between S. chamaejasme leaf ecological stoichiometry and soil physicochemical properties were observed. These indicate the nutrient concentrations and stoichiometry of S. chamaejasme tend to be insensitive to variations in the soil nutrient availability, resulting in their broad distributions in China’s grasslands. Besides, different homeostasis strength of the C, N, K, and their ratios in S. chamaejasme leaves across all sites were observed, which means S. chamaejasme could be more conservative in their use of nutrients improving their adaptation to diverse conditions. Moreover, the leaf C and N contents of S. chamaejasm were unaffected by any climate factors. However, the correlation between leaf P content and climate factors was significant only in IM, while the leaf K happened to be significant in QT. Besides, MAP or MAT contribution was stronger in the leaf elements than soil by using mixed effects models, which illustrated once more the relatively weak effect of the soil physicochemical properties on the leaf elements. Finally, partial least squares path modeling suggested that leaf P or K contents were affected by different mechanisms in QT and IM regions, suggesting that S. chamaejasme can adapt to changing environments by adjusting its relationships with the climate or soil factors to improve its survival opportunities in degraded grasslands.