基于Maxent模型的青藏高原优势种草分布格局模拟研究

以青藏高原嵩草、苔草、针茅3种优势种草为研究对象,通过植物标本库查询得到草地标本点位数据,选取气候、土壤质地、地形为环境因子,运用Maxent模型模拟出每种优势种草的分布格局,并运用刀切法筛选出主导环境因子,探讨主导环境因子对不同优势种草分布的影响与内在机制。结果表明,最冷季降水量、温度季节性变化标准差、年降水量、海拔是嵩草分布的主导环境因子(累计贡献率>80%);最冷季降水量、最暖季均温、年降水量、海拔对苔草分布贡献较大(累计贡献率82.55%);最暖季降水量、年均温、坡度、海拔对针茅分布影响较大(累计贡献率73.47%)。土壤质地对3种草分布影响很小(累计贡献率<5%)。总体上,生长季水热综合条件是制约青藏高原优势物种分布的最主要气候因子。

Herbivores alleviate the negative effects of extreme drought on plant community by enhancing dominant species

Aims Both extreme drought and insect herbivores can suppress plant growth in grassland communities.However,most studies have examined extreme drought and insects in isolation,and there is reason to believe that insects might alter the ability of grasslands to withstand drought.Unfortunately,few studies have tested the interactive effects of extreme drought and insect herbivores in grassland communities.Methods Here,we tested the drought–herbivore interactions using a manipulative experiment that factorially crossed extreme drought with the exclusion of insect herbivores in a temperate semiarid grassland in Inner Mongolia.Important Findings Our results demonstrated that both extreme drought and insect herbivores separately decreased total plant cover.When combined,insect herbivores reduced the impact of drought on total cover by increasing the relative abundance of drought-resistant dominant species.Our results highlight that the negative effect of extreme drought on total plant cover could be alleviated by maintaining robust insect herbivore communities.

Changes in vegetation and soil properties following 6 years of enclosure in riparian corridors

Aims Riparian corridors play vital roles in the maintenance of biodiversity.Nonetheless,plant species diversity and vegetation coverage in riparian corridors are seriously threatened by increasing pressure owing to livestock consumption and anthropogenic disturbance;even the stability of river courses has been threatened.The establishment of enclosures is a widely used strategy to restore degraded grassland ecosystems,but its impact on degraded herbaceous riparian vegetation and soil properties remains unclear.The aim of this study was to evaluate whether species composition,richness,diversity,and soil properties can be recovered by the enclosure.Methods Twenty long-term monitoring sample plots were set in the Liaohe main stream river,Liaohe main stream river was enclosed for grazing and farmland exclusion in 2012.The height,coverage and individual numbers of plant were recorded for species richness and diversity evaluation from 2012 to 2017;soil nutrients were measured for comparative analysis in 2012 and 2017.We examined the effects of the establishment of enclosures on plant species diversity and soil properties from 2012 to 2017 in the riparian corridors of the Liaohe River system in China.Important Findings Plant species richness and diversity significantly increased from 2012 to 2017.The dominance of Asteraceae plants increased,while the abundance of Gramineae plants decreased over time.The difference in abundance increased each year since enclosure was implemented in 2012.The concentrations of phosphorus and potassium in the soil significantly decreased as a result of the combined effects of vegetation restoration and prohibition of farming practices following the establishment of enclosures.There was also a lag time related to the response of soil organic matter to the establishment of enclosures.In conclusion,our study provides new evidence regarding the response of species diversity,species composition and soil properties following riparian vegetation restoration efforts through enclosure development.

Above-and belowground trait linkages of dominant species shape responses of alpine steppe composition to precipitation changes in the Tibetan Plateau

Aims Human activities and global changes have led to alterations in global and regional precipitation regimes.Despite extensive studies on the effects of changes in precipitation regimes on plant community composition across different types of grassland worldwide,few studies have specifically focused on the effects of precipitation changes on high-altitude alpine steppe at community and plant species levels in the Tibetan Plateau.Methods We investigated the effects of growing-season precipitation changes(reduced precipitation by 50%,ambient precipitation,enhanced precipitation by 50%)for 6 years on plant community composition in an alpine steppe of the Tibetan Plateau by linking above-to belowground traits of dominant species.Important Findings We found that reduced precipitation shifted community composition from dominance by bunchgrass(primarily Stipa purpurea)to dominance by rhizomatous grass(primarily Leymus secalinus).Roots and leaf traits of L.secalinus and S.purpurea differed in their responses to reduced precipitation.Reduced precipitation enhanced root vertical length and carbon(C)allocation to deep soil layers,and decreased the leaf width in L.secalinus,but it did not change the traits in S.purpurea.Moreover,reduced precipitation significantly enhanced rhizome biomass,length,diameter and adventitious root at the rhizome nodes in L.secalinus.These changes in traits may render rhizomatous grass greater competitive during drought stress.Therefore,our findings highlight important roles of above-and belowground traits of dominant species in plant community composition of alpine steppe under precipitation change.