阿拉斯加苔原植被优势种地理分布的未来模拟

北极地区被认为是气候变化最为敏感的地区之一,苔原生态系统在北极生态系统中扮演着至关重要的角色。本研究利用生态位模型MaxEnt,基于物种分布点和环境数据,模拟阿拉斯加苔原植被六个优势种当前(1970—2000年)潜在分布,并预测2021—2040年SSP1-2.6、SSP2-4.5、SSP3-7.0、SSP5-8.5情景下的变化,根据各因子贡献率大小确定主导因素。研究结果表明:影响物种分布的最主要环境因子是温度,优势种适生区变化存在空间异质性。相较于当前气候,在2030年四种气候情景下,矮灌木优势种北极果面积均减小,地衣优势种鹿蕊和莎草优势种白毛羊胡子草总面积均增大。在低强迫情景(SSP1-2.6)下,北极果和匍匐矮灌木优势种仙女木适生区总面积增大,然而在中、中高和高辐射强迫情景下,全球变暖加剧,适生区面积减小。半匍匐矮灌木优势种四棱岩须和苔藓优势种塔藓在不同气候情景下适生区总面积无规律性变化,但低适生区面积均减小,向中、高适生区转移。同时,优势物种会向更高纬度和更高海拔地区移动。

黑河下游绿洲植被优势种生物量空间分布及蒸腾耗水估算

基于典型样点试验,建立了研究区植被优势种柽柳、胡杨与苦豆子地上生物量与其生态参数关系模型;利用高分辨率遥感影像Geoeye-1对植被优势种进行分类得到生态参数,实现了其地上部分生物量空间分布估算;最后利用生物量与蒸腾系数关系,估算植被优势种蒸腾耗水。结果显示:植被优势种总生物量为2.53×106t,河流距离对生物量影响显著。根据试验测得的植被优势种蒸腾系数估算出总蒸腾耗水量为10.89×108t,柽柳、胡杨与苦豆子所占比例分别为12.94%,82.93%与4.13%。

民勤绿洲青土湖植被优势种地上生物量估算

青土湖区域属于绿洲—荒漠过渡带,生态系统脆弱,极易发展为荒漠。梭梭、白刺和芦苇为青土湖区域的植被优势种,对其生态系统稳定与健康发展起着关键作用。以青土湖区域梭梭、白刺和芦苇为研究对象,利用空间分辨率为0.5 m的高分辨率遥感影像Worldview-2,采用辅以纹理特征的面向对象分类方法,提取梭梭和白刺的冠幅面积以及芦苇的分布面积;根据野外试验数据,建立梭梭和白刺地上生物量与冠幅面积、芦苇地上生物量与分布面积关系模型。利用关系模型、冠幅面积以及分布面积对青土湖区域植被优势种地上生物量进行了估算,实现了植被优势种地上生物量估算由“点”到“面”的转换。结果表明:(1)采取辅以纹理特征的面向对象分类方法取得了较高的分类精度,总体Kappa系数为87.9%,总体精度达到91.3%。(2)研究区植被优势种地上生物量总量为3.17×103 t,其中梭梭地上生物量为0.54×103 t,白刺地上生物量为0.90×103 t,芦苇地上生物量为1.73×103 t,地上生物量芦苇>白刺>梭梭。该研究可以为深入研究青土湖区域生态恢复与碳储量提供参考。

元谋干热河谷冲沟发育阶段与植被优势种关系探讨

对元谋干热河谷区冲沟的立地条件和形成原因等方面进行研究,运用重要值方法对4个样区53条冲沟的植被优势种进行筛选和判断,利用SPSS软件分析植被优势种与冲沟发育阶段间的联系。结果表明:该研究区冲沟发育阶段与乔灌草优势种间关系表现为一定的线性关系:发育阶段=0.310+0.943盖度值(灌木优势种)+0.702盖度值(草本优势种),同时两者相关系数达到0.872,相关性显著。冲沟发育过程中,灌木优势种种类逐步增多,而草本逐步变少,并慢慢趋于稳定,由此可以初步判断冲沟的发育阶段,为该区生态恢复提供科学指导。

银滩黄河湿地植被优势种光合作用影响因子识别

对兰州市银滩黄河湿地10种植被优势种千屈菜、芦苇、酸模叶蓼、稗草、龙葵、反枝苋、曼陀罗、红豆草、藨草、水莎草的光合作用影响因子进行了分析，探讨了多种生理、生态因子对湿地植被优势种净光合速率（Pn ）的影响程度。采用主成分分析法对兰州银滩黄河湿地10种植物优势种的光合作用影响因子进行了分析，反枝苋提取了前3个主成分，其他9种植物提取了前2个主成分。结果表明，影响植物光合作用因子的主要成分中，第1主成分里光强和温度对湿地植物净光合速率的贡献很大，第2主成分里蒸腾速率（Tr ）、胞间 CO2浓度（Ci ）、气孔导度（Gs ）对净光合速率的影响较大，每天10：00～15：00各植物影响光合作用的因子主成分得分排序较高，说明强烈的太阳辐射是引起一天中空气温度、相对湿度等一系列环境条件变化的根本原因，进而通过影响气孔导度和蒸腾速率等生理因子影响植物的净光合速率。

Study on the Characteristics of Main Vegetation Communities in the Limestone Region of Taihang Mountain

[Objective] The aim was to study the characteristics of main vegetation communities in the limestone region of Taihang Mountain,so as to lay foundation for the further improvement of site conditions and the scientific breeding of vegetation used to restore the mountain field in limestone region.[Method] Based on the investigation of various vegetation communities in controlled test area,forbidden region and barren hillsides in Daqing Mountain basin,Beishui Valley,Mancheng County,Hebei Province,the difference among controlled region,forbidden region and barren hillsides could be found through data analysis and composite score,and the modes of vegetation communities in controlled region and forbidden region were compared to select predominant species of arbor,shrub and grass in limestone region.[Result] Under the similar site conditions,nutrient content and physical properties of soil in controlled region and forbidden region were superior to those of barren hillsides,and persimmon had high nutrient content and better physical properties compared with oriental arborvitae in controlled region;soil water maintenance and litter characters in controlled region and forbidden region improved more obviously than that of barren hillsides,and shrubbery in forbidden region was the most excellent,arborvitae and persimmon in controlled region the second;the biomass and the coverage rate of vegetation communities in controlled region and forbidden region were higher than those of barren hillsides,and those of shrubbery in forbidden region were better than tussock in closing hill,while persimmon was better than arborvitae in controlled region.The predominant species of arbor,shrub and herbage were obtained through composite score.[Conclusion] From the aspects of soil nutrient,physical properties,soil water maintenance,litter characters,vegetation biomass,canopy density and coverage,controlled region and forbidden region were superior to barren hillsides,and the selection of predominant species of arbor,shrub and herbage considered both ecological and economic benefits.

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.