Diversity patterns of cushion plants on the Qinghai-Tibet Plateau:A basic study for future conservation efforts on alpine ecosystems

The Qinghai-Tibet Plateau(QTP)is an important cushion plant hotspot.However,the distribution of cushion plants on the QTP is unknown,as are the factors that drive cushion plant distribution,limiting our understanding of the evolution of cushion species in the region.In this study,we assessed spatial patterns of total cushion plant diversity(including taxonomic and phylogenetic)over the entire QTP and compared patterns of diversity of cushion plants with different typologies(i.e.,compact vs.loose).We also examined how these patterns were related to climatic features.Our results indicate that the southern QTP hosts the highest total cushion plant richness,especially in the south-central Hengduan Mountains subregion.The total number of cushion species declines from south to north and from southeast to northwest.Compact cushion plants exhibit similar patterns as the total cushion plant richness,whereas loose cushion plants show random distribution.Cushion plant phylogenetic diversity showed a similar pattern as that of the total cushion plant richness.In addition,cushion plant phylogenetic community structure was clustered in the eastern and southwestern QTP,whereas random or overdispersed in other areas.Climatic features represented by annual energy and water trends,seasonality and extreme environmental factors,had significant effects on cushion plant diversity patterns but limited effects on the phylogenetic community structure,suggesting that climatic features indeed promote the formation of cushion plants.Because cushion plants play vital roles in alpine ecosystems,our findings not only promote our understanding of the evolution and formation of alpine cushion plant diversity but also provide an indispensable foundation for future studies on cushion plant functions and thus alpine ecosystem sustainability in the entire QTP region.

Non-Linearity of Visual Sensitivity and Pursuit Velocity during Smooth Pursuit Eye Movements

During pursuit eye movements, whether the relationships among the visual sensitivity, pursuit velocity, and target velocity are linear or non-linear is an old issue. In this study, we reexamined their relationships with seven speeds by a simple character discrimination task using an infrared eye tracker. Our results found that the pursuit velocity and accuracy were non-linearly related with the target velocity. Besides, the perceptual sensitivity was not linearly related with the pursuit velocity either. A significant difference existed between lower （less than 20 deg/s） and higher speeds （greater than 20 deg/s）. In addition, we found there was no position bias of visual sensitivity between ahead of and behind the pursuit target, but there was a significant perceptual dissymmetry between horizontal and vertical directions at lower pursuit speeds.

Allelopathic potentials of surrounding vegetation on seedling establishment of alpine cushion Arenaria polytrichoides Edgew

When facilitating other species and sustaining plant community structures and biodiversity,alpine cushion plants simultaneously experience negative feedback effects from surrounding vegetation.However,the impact of surrounding vegetation on cushion dynamics remains poorly understood,particularly in terms of allelopathic potentials.To investigate the allelopathic potentials of surrounding vegetation on seedling establishment of the typical cushion plant Arenaria polytrichoides Edgew.along an elevational gradient,we extracted potential allelopathic compounds and tested their impacts on seed germination and seedling growth of A.polytrichoides.In addition,exclusion experiments using activated carbon were conducted to further elucidate these effects.Our results demonstrate that surrounding vegetation exhibits certain allelopathic potentials on A.polytrichoides seedling establishment,with variations observed based on elevation,source and concentration of allelopathy compounds,as well as growing season.Specifcally,low-elevation vegetation exerts pronounced suppression on seedling establishment.Conversely,higher-elevation vegetation generally shows no effect on seed germination but stimulates seedling growth through allelopathy mechanisms.Moreover,aboveground vegetation predominantly inhibits both seed germination and seedling growth in low-elevation communities;however,the effects of belowground vegetation depend on elevation and extract concentration levels.The identifed allelopathic potentials of surrounding vegetation signifcantly infuence the population dynamics of cushion A.polytrichoides by potentially accelerating population degeneration in lower-elevation communities while ensuring consistent population recruitment and expansion in higher-elevation communities.