Shrub encroachment can alter the structure and function of grassland ecosystems, leading to their degradation. Therefore, population regeneration dynamics after shrub encroachment on the influence of grassland should not be ignored. H. rhamnoides, as a pioneer species, has significantly encroached with large areas onto the Qinghai-Tibetan Plateau (QTP) due to climate change and over-grazing. However, few studies have focused on the dynamics of population regeneration following successful encroachment. Therefore, we studied H. rhamnoides natural population in the alpine grasslands, investigating population regeneration pattern, seed, bud production and storage, and limitation imposed by microhabitats (soil, light and feeding). Our aim was to explore population regeneration strategies and identify key limiting factors for population regeneration after successful encroachment. Our findings revealed several key points: (i) H. rhamnoides entered the alpine grassland by relying on seeds, it would seize resources by low-cost clonal reproduction, then increase sexual reproduction to improve genetic diversity. (ii) The production and storage of seeds and buds was sufficient, seed vigor was high, seed emergence rate was higher duo to mechanical restriction of hard seed coat was weakened by the water transport channels in the palisade layer, and formation of seedlings was less restricted. (iii) H. rhamnoides population regeneration was mainly limited by microhabitats light and feeding. However, light and feeding significantly affected seedlings photosynthesis and carbon storage, their interaction significantly reduced the seedlings survival, and further restricted population regeneration. The results can provide theoretical basis for the restoration and management of alpine grassland degradation caused by shrub encroachment.

The extensive afforestation efforts on the Loess Plateau, incurring hundreds of billions of CNY, trigger heightened vegetation cover, depleting soil water, and imperiling ecosystem sustainability. Widespread debate persists over the feasibility and optimal locations for afforestation. However, what has been overlooked is the potential presence of alternative stable states within ecosystems, a captivating system equilibrium behavior. This study integrates remote sensing, minimal model, and environmental data to investigate the equilibrium behavior (quantified by tree cover) of forest ecosystems on the Loess Plateau and its implications. The findings suggest a threshold relationship between tree cover and annual precipitation, with a significant increase observed up to 400 mm. Beyond this threshold, alternative stable states emerge, characterized by high tree cover (forest, >35%) and medium tree cover (open woodland, 7%~35%). The equilibrium behavior of the forest ecosystem combines thresholds and alternative stable states. Increasing spatial heterogeneity, especially the positive feedback between vegetation and precipitation, results in advancing transition thresholds with higher annual precipitation. Regime shifts from forest to open woodland increase carbon stock but decrease water yield, revealing a trade-off between carbon sequestration and water resources. This nuanced understanding of equilibrium enhances both theoretical comprehension and practical planning for afforestation on the Loess Plateau, promoting the functions and services of the forest ecosystem.

Predicting how seeds persist in the soil seed bank based on easy-to-measure traits is of prime importance to improve management strategies in grazing, farming, and species invasion. We found that seeds that are smaller and rounder are more likely to form persistent seed banks at a global scale, using the 1303 species. The relationship between seed bank persistence and seed mass and shape was not affected by phylogeny or mean annual precipitation. However, the relationships is not significant in woody perennials. Species with smaller seeds are more likely to form persistent seed banks at sites with low soil sand content, in grassland systems or at low mean annual temperatures. Species with rounder seeds are more likely to form a persistent seed bank at higher latitudes. Our results suggest that seed burial mechanics exert environmental filtering on seed traits, and help improve to assess vegetation restoration capacity.