Scale dependence of plant species richness and vegetation-environment relationship along a gradient of dune stabilization in Horqin Sandy Land, Northern China

Ecological patterns and processes in dune ecosystems have been a research focus in recent years, however the information on how dune stabilization influences the spatial scale dependence of plant diversity is still lacking. In this study, we measured the plant species richness, soil properties and altitude across four spatial scales （1, 10, 100 and 1,000 m2） at three different dune stabilization stages （mobile dune, semi-fixed dune and fixed dune） in Horqin Sandy Land, Northern China. We also examined the relationships between plant species richness, community composition and environmental factors along the gradient of dune stabilization. Our results showed that plant species richness increased with the increase of spatial scales in each dune stabilization stage, as well as with the increase of dune stabilization degrees. Canonical correspondence analysis （CCA） showed that plant distribu- tions in the processes of dune stabilization were determined by the combined environmental gradient in relation to soil organic carbon （SOC）, total nitrogen （TN）, carbon/nitrogen （C/N）, pH, electrical conductivity （EC）, soil water content （SWC）, fine sand （FS）, very fine sand （VFS）, silt and clay （SC）, and altitude. Plant species richness was significantly and positively correlated to SOC and TN in mobile dune, and significantly and positively correlated to SOC, TN, C/N, VFS and SC in semi-fixed dune. However, no significant correlation between plant species richness and environmental factors was observed in fixed dune. In addition, plant species richness in different dune stabili- zation stages was also determined by the combined gradient of soil properties and altitude. These results suggest that plant species richness has obvious scale dependence along the gradient of dune stabilization. Soil resources depending on dune habitats and environmental gradients caused by dune stabilization are important factors to de- termine the scale dependence of species diversity in sand dune ecosystems.

Relationship between diversity of forest plant species and environmental gradient in eastern mountainous area of Heilongjiang Province, China

Twenty-three secondary forest communities with different structure were selected in Mao＇er Mountain National Park of Heilongjiang Province, China to study the relationship between diversity of forest plant species and environmental gradient. The forest plant species diversity was analyzed by the diversity index, and the environmental factors was quantified by the method of Whittaker＇s quantification of environmental gradient. Meanwhile, β-diversity indexes of communities were calculated with similar measurements. The results showed that the Shannon-wiener diversity index of forest plant species increased with the increase of the environmental gradient, and the β-diversity indexes of communities showed a liner increase along with the change of environmental gradient.

Floristic composition and structure of the Kibate Forest along environmental gradients in Wonchi,Southwestern Ethiopia

Dry evergreen montane forests in Ethiopia are severely threatened.The status of species composition and structure of forest vegetation are important indicators to understand the trends of threats on local plant communities.In the present study,we examined the floristic composition and structure of the Kibate Forest,Wonchi Highland,Ethiopia along environmental gradients.Sixty-six(30 m×30 m)plots were established every 100 m interval along altitudinal gradients(2811‒3073 m a.s.l.)in five transect lines for vegetation and environmental data collection.In total,125 vascular plant species belonging to 104 genera and 52 families were identified.Eighteen species(14%)were endemic to Ethiopia and Eritrea.The two most dominant families,Asteraceae(29 species)and Lamiaceae(eight species)accounted for 30%of the total number of species.The highest number of species(54%)was herbs.Four major community types(viz.,Olinia rochetiana-Myrsine melanophloeos,Ilex mitis-Galiniera saxifraga,Erica arborea-Protea gaguedi,and Hagenia abyssinica-Juniperus procera)were identified.The highest species richness,evenness,diversity,and importance value index were in community types 2 and 4.About 82%of the species and all endemic taxa except five were recorded in these two community types.The most dominant woody species were O.rochetiana,E.arborea,Olea europaea subsp.cuspidata,Myrica salicifolia,I.mitis var.mitis,and H.abyssinica with different patterns of population structure.The results show that there was a weak correlation between species richness and altitude.Our findings confirm that environmental variables both with interactions(such as altitude)and without interactions(such as livestock grazing)significantly(p<0.05)affect species richness.Anthropogenic activities and overgrazing by livestock appear to be the main threat in community types 2 and 3.Urgent management practices and conservation measures such as prohibiting forest clearing and overgrazing and planting indigenous trees through community participation should be considered in community types that are rich in endemic species but are highly threatened.

Ecological thresholds of phytoplankton community across environmental gradients in the harmful algal blooms-frequently-occurring,subtropical coastal waters,East China Sea

Phytoplankton communities can response immediately and directly to environmental changes,and thus have been applied as reliable biotic indicators in aquatic systems.This study provided insights into the relationships concerning ecological thresholds of phytoplankton communities and individual taxon in response to environmental changes in coastal waters of northern Zhejiang Province,East China Sea.Results demonstrated that there existed seasonal variations of phytoplankton community ecological thresholds of which spring being higher than those in summer.As for individual species,Prorocentrum donghaiense and Noctiluca scintillans were identified as the most tolerant and sensitive indicator species in spring and summer,respectively.They exhibited strong indications in response to environmental changes.These findings highlighted that phytoplankton community structure in this region was stable when environmental gradients were below the thresholds of sensitive species,whereas potential harmful algal blooms may occur when environmental gradients exceeded the thresholds of tolerant species.

Response of reed community to the environment gradientwater depth in the Yellow River Delta, China

We investigated and monitored a reed community in the fields.Data on the bio-ecological characteristics and β-diversity of reed communities in different environmental gradients(mainly based on water depth)of the Yellow River Delta were collected through multianalysis,extremum analysis and β-diversity index analysis.In accordance with the square sum of deviations(Ward)cluster analysis,10 sampling plots were divided into six types with the dominant plants in different plots varying according to the change in environmental gradients.The dominant plants in these plots varied from aquatic plants to xerophytes and salt tolerant plants as water depth decreased.The average height and diameter of the reeds at breast level were significantly correlated with the average water depth.The fitness curves of average density and coverage with average water depth were nonlinear.When the average water depth was 0.3 m,the average density and coverage of reeds reached the apex value,while the height and diameter of the reeds at breast level increased with the water depth.There were obvious changes to the environmental gradient in the Yellow River Delta.The transitional communities were also found to exist in the Yellow River Delta by β-diversity analysis.Vicarious species appeared with the change in water depth.The occurrence of substitute species is determined by the function of common species between adjacent belts.The different functions of common species led to differences in community structure and function and differences in dominant plants.The result reflects the variations of species present in different habitats and directly reflects environmental heterogeneity.The values of β-diversity indices of adjacent plots were higher than those of nonadjacent plots.There are transition zones between the xerophytes and aquatic plants in the Yellow River Delta.In an aquatic environment,the similarity of reed community is higher than that of xeromorphic plants.The β-diversity index can reflect plant succession trends caused by the change in environmental gradients in the Yellow River Delta.The β-diversity index reveals plant responses to changes in environmental gradient and is helpful in observing changes in patterns of species diversity in relation to environmental gradient change and evolving trends in the future,which in turn plays a prominent role when environmental water requirements of wetland are discussed.

长白山园池湖岸湿地生态系统碳氮储量沿环境梯度空间分异规律

【目的】探究湖泊沿岸湿地生态系统碳氮储量沿湖岸至高地的空间分异规律及形成机制,将有助于减少湿地碳储量估算的不确定性。【方法】采用相对生长方程、碳/氮分析仪,同步测定长白山园池沿湖岸至高地环境梯度依次分布的6种沼泽类型(芦苇沼泽L、草丛沼泽C、杜香沼泽D、落叶松泥炭藓沼泽LN、落叶松藓类沼泽LX、落叶松苔草沼泽LT)的生态系统碳、氮储量(植被和土壤)及其相关环境因子(水位、水位波动幅度、土壤有机质、全氮和全磷等),揭示其空间分异规律及其形成机制。【结果】(1)植被碳、氮储量(2.17~69.98 t/hm^(2)和0.058~0.940 t/hm^(2))沿湖岸至高地环境梯度均呈递增规律(LT≈LX>LN>D>C>L),且均以优势植被层占主体地位(73.72%~93.37%和71.57%~85.24%);(2)土壤碳、氮储量(67.45~243.21 t/hm^(2)和2.44~13.53 t/hm^(2))沿该环境梯度呈阶梯式递减规律(L>C>D≈LN>LX≈LT)且其碳储量垂直空间分异存在先恒定后递减(L)、先增后降(C、D和LN)和递减(LX和LT)3种类型,其氮储量垂直空间分异与碳储量基本一致(仅C和LX略有不同);(3)生态系统碳、氮储量(122.20~245.38 t/hm^(2)和3.31~13.58 t/hm^(2))沿该环境梯度分别呈先降低后恒定型或阶梯式递减型变化规律,且其土壤碳、氮储量占比呈递减趋势(50.27%~99.11%和73.48%~99.57%),而植被碳、氮储量占比却呈递增趋势(0.89%~49.73%和0.43%~26.52%);(4)生态系统碳储量在湖岸至高地水分环境梯度的下、中、上部生境地段依次受水位促进、水位抑制和水位波动幅度抑制,而氮储量在相应生境地段上依次受水位促进、水位波动幅度抑制和土壤全氮促进。【结论】园池沿岸湿地生态系统碳氮储量沿湖岸至高地水分环境梯度存在明显的空间分异规律,且其形成机制为微地形引起的水位梯度和植被类型分布决定着各沼泽类型的碳氮储存能力,故准确测定湖岸带各沼泽类型碳氮储量将有助于减少集水区尺度上碳氮储量估算的不确定性。

不同纬度植物群落系统发育与功能性状结构研究

研究植物群落系统发育和功能性状结构有助于了解植物多样性维持机制及物种间的亲缘关系。甘肃省地理环境复杂,显著而多变的气候梯度形成了区域植被和环境差异,丰富了栖息地类型,具有显著的纵向连通性和纬度隔离性,以甘肃省典型纬度梯度植物群落为研究对象,通过对其进行群落学调查和功能性状测定,计算净亲缘关系指数(Net relatedness index, NRI)和平均成对性状距离(Mean pairwise trait distance, PW)来分析植物群落系统发育结构和功能性状格局对不同纬度的响应。结果表明:(1) Shannon-Weiner多样性指数,物种丰富度,谱系α多样性指数表现出随纬度增加而显著降低的变化趋势(P<0.05),Pielou均匀度指数随纬度的升高没有显著的变化趋势;(2)系统发育结构在高、低纬度上趋于发散状态(NRI<0),在中纬度上又表现出聚集(NRI>0)的谱系结构,表明种间竞争作用减弱,环境过滤作用逐渐增强,随纬度继续升高相似性限制作用在物种聚集过程中占优势;而群落的功能性状结构随着纬度增加表现出与谱系结构相反的状态,因此植物群落的系统发育和功能性状结构不一致;(3)植物高度表现出微弱的系统发育信号(P<0.05),其他性状均未表现出显著的系统发育信号,表明植物功能性状受环境因素影响大,与系统发育关系不大。总体而言,甘肃省典型纬度梯度植物群落物种多样性维持机制由确定性过程主导,支持生态位理论,其中环境过滤和竞争排斥作用在大多数群落物种聚集过程中占优势地位。土壤含水量、土壤酸碱度和年平均气温等环境因子对植物性状格局影响较大,本研究有助于了解不同气候带植物多样性的地理分布格局和潜在的生态维持机制。

伊犁河谷草地生物量碳的变化研究

通过研究不同海拔高度下草地生物量碳的分布规律,可以评估不同海拔高度下生态系统的碳储量,为生态系统碳平衡和碳管理提供科学依据。探究了伊犁河谷不同海拔高度下草地地上生物量碳与土壤环境因子的分布特征及相关关系,结果表明:①随着海拔上升,土壤温度呈现波动下降趋势,土壤含水量与盐分呈波动上升趋势。H1-H10(海拔1000~2500 m)土壤温度、含水量与盐分分别处于10.87~19.97℃、8.42%~40.17%与0~1.31 g/kg。②草地地上生物量碳储量在5月份随着海拔的升高,呈“降低-增加-降低”的变化趋势,H9(海拔2100~2200 m)时最大,为234 gC/m^(2),7月份呈“增加-降低-增加”的变化趋势,H2(海拔1200~1300 m)时最大,为296.44 gC/m^(2);空间分布上,5月份地上生物量碳储量呈现“西高东低”分布,7月份呈相反趋势。③H8(海拔2000~2100 m)时地上生物量碳储量与土壤温度呈显著负相关,与土壤水分和植被叶面积指数都呈显著正相关(P<0.05)。

Characterization of Soil Quality Under Vegetable Production Along an Urban-Rural Gradient

Human activity and urbanization result in urban-rural environmental gradients. Understanding effect of the gradients on soil properties is necessary for management of the soils around urban areas. In this study, soil quality of some vegetable fields was characterized along an urban-rural gradient in Shaoxing County, Zhejiang Province. Fifteen soil physical and chemical properties were evaluated by using principal component analysis.Results showed that there was a great variation in the soil quality along the gradient. From rural to urban zones, soil organic matter, water-stable aggregates, cation exchangeable capacity (CEC), total N and P, and available K increased, whereas soil pH value decreased. In addition, Pb, Cu, Ni, Co, Zn and Cr in the soils tended to be accumulated toward the urban zone. Sequential chemical extraction showed that mobility of all the heavy metals in the soils tended to increase from the rural to the urban zones. The variation of soil properties accounted for by the first principal component was significantly explained by the difference in application rates of municipal wastes.

南四湖出湖口沉积物-水界面中营养盐分布特征分析及释放风险评估

为了解决南四湖出湖口沉积物-水界面中磷酸盐、氨氮和硝态氮等营养盐释放风险控制缺乏科学依据的问题,利用薄膜扩散梯度技术、高分辨率孔隙水采样技术分析南四湖出湖口沉积物-水界面中营养盐浓度的垂直剖面分布特征,并根据有效态磷、有效态氨氮和有效态硝态氮的浓度,计算三者的净扩散通量,评估三者的释放风险。结果表明:非泄洪期南四湖出湖口上覆水中的溶解态磷浓度低于孔隙水中的,表明沉积物孔隙水中的溶解态磷可能会因浓度梯度的存在而向上覆水中扩散;根据连续分级提取法,钙结合态磷是南四湖出湖口沉积物中磷元素的主要赋存形态,表层沉积物中的不稳定磷元素含量高于深层沉积物中的;有效态磷与有效态铁呈显著正相关,说明南四湖出湖口沉积物-水界面中有效态磷的释放受铁氧化物还原释放影响;有效态磷、有效态氨氮和有效态硝态氮的净扩散通量分别为17.58、1.16、-40.72 ng/(cm^(2)·d),说明有效态磷和有效态氨氮有从沉积物向上覆水中释放的潜在风险。

Regeneration dynamics of dominant tree species along an altitudinal gradient in moist temperate valley slopes of the Garhwal Himalaya

The present study was undertaken in moist temperate forest of Mandal-Chopta area in the Garhwal region of Uttarakhand, India. The aim of the present study was to understand the regeneration dynamics of the dominant tree species along an altitudinal gradient in naturally regen- erating, restricted access forest. The overall regeneration status was fairly high in the study area. Most of the native canopy and undercanopy domi- nants had frequent reproduction and expanding populations, which sug- gests the stability of forest structure/composition and further expansion of dominant species. The overall regeneration of trees in the forest had a greater contribution of middle and understurey species. Because of infre- quent rep＇roduction and declining populations of some of the dominant native species viz., Abies pindrow, Alnus nepalensis and Betula alnoides, structural/compositional changes in the future are expected in respective forests dominated by them..4bies pindrow and Taxus baccata need im- mediate attention by forest managers for their survival in the area. Seed- lings were found to be more prone to competition from herb and shrubs than saplings.

大型综合环境试验箱试验设计及速度场研究

大型综合环境试验箱作为大型设备环境适应性及可靠性试验的重要设备之一,对产品的性能及评估优化具有重要作用。本文的目的是通过系统阐述大型综合试验箱的工作原理及设计,为后续的系统优化提供依据;同时利用CFD数值模拟计算得到不同送风速度下的速度场分布。数值模拟计算结果表明,空箱运行时,试验箱内会形成回旋涡流现象;但增加振动台及试验件时,这一现象消失,但送风侧的速度下降;随着高度地升高,气流速度呈现先下降后上升的趋势;增加振动台及试验件时,对速度场的扰流作用较大。

Tropical tree community composition and diversity variation along a volcanic elevation gradient

Unraveling the factors that determine variation of diversity in tropical mountain systems is a topic for debate in plant ecology.This is especially true in areas where topography is complex due to volcano elevational gradients and where forests are vulnerable to human activity.In this study we used a set of climatic(temperature,rainfall,and radiation solar),topographic(elevation,slope aspect,and slope orientation)and human disturbance variables to determine their effect on diversity and composition patterns of a tree community,considering three slope aspects of a tropical volcano in southeastern Mexico.We sampled trees in seventy 0.1-ha plots distributed on three slope aspects of the Tacanávolcano along an elevational gradient of 1500 to 2500 m.We determined diversity patterns(general tree richness,exponential of Shannon index,and pioneer species richness)with linear regression models,and for beta diversity,we used a dissimilarity index(within and between elevational bands 100 m wide).The effect of a set of environmental and human disturbance variables on tree diversity and community composition was analyzed with general linear models and multivariate analyses,respectively.We registered 2,949 individual trees belonging to 176 species and 58families.The average species richness and alpha diversity per plot were 13(standard deviation±6)and 9(±5),respectively.General tree richness and alpha diversity increased in the middle part(unimodal patterns)of the elevational gradient,but pioneer species richness decreased linearly with elevation.The variance explained by general linear models was greater in richness(32%)than in alpha diversity(25.3%).The most important predictor variables were temperature(elevational gradient),which explained the unimodal pattern(richness and alpha diversity increase at intermediate levels of temperature),and slope orientation,which explained the increase in richness and alpha diversity toward the geographic north.Only temperature had a significant effect on pioneer species diversity(22%).For community composition,all the predictor variables evaluated had a significant effect,but the most important were slope aspect and temperature.Assemblages were almost completely different in plots that were farther apart along the elevation gradient and had different slope aspects.Finally,the forests at lower elevations(1500–1900 m)were those that had the most human disturbance.Our study reveals the importance of considering a set of environmental variables related to climate,topography(e.g.,slope aspect),and human disturbance to understand variation in diversity and composition of a tree community on a tropical volcano.With this information,we believe that it is important to implement conservation and restoration measures in the forests of the lower parts of the Tacanávolcano,complemented by studies that contribute to designing better conservation strategies.

Plankton community composition in the Three Gorges Reservoir Region revealed by PCR-DGGE and its relationships with environmental factors

To explore the relationships between community composition and the environment in a reservoir ecosystem, plankton communities from the Three Gorges Reservoir Region were studied by PCR-denaturing gradient gel electrophoresis fingerprinting. Bacterial and eukaryotic operational taxonomic units （OTUs）, generated by DGGE analysis of the PCR-amplified 16S and 18S rRNA genes, were used as surrogates for the dominant ＂biodiversity units＂. OTU composition among the sites was heterogeneous; 46.7% of the total bacterial OTUs （45） and 64.1% of the eukaryotic OTUs （39） were identified in less than half of the sampling sites. Unweighted pair group method with arithmetic averages （UPGMA） clustering of the OTUs suggested that the plankton communities in the Xiangxi Rive sites were not always significantly different from those from the Yangtze River sites, despite clear differences in their environmental characterizations. Canonical correspondence analysis （CCA） was applied to further investigate the relationships between OTU composition and the environmental factors. The first two CCA ordination axes suggested that the bacterial community composition was primarily correlated with the variables of NO3^--N, dissolved oxygen （DO）, and SiO3^2--Si, whereas, the eukaryotic community was mainly correlated with the concentrations of DO, PO4^3--P, and SiO3^2--Si.

Application of Hydrogen Peroxide as an Environmental Stress Indicator for Vegetation Management

Adaptive vegetation management is time-consuming and requires long-term colony monitoring to obtain reliable results. Although vegetation management has been widely adopted, the only method existing at present for evaluating the habitat conditions under management involves observations over a long period of time. The presence of reactive oxygen species （ROS） has long been used as an indicator of environmen- tal stress in plants, and has recently been intensely studied. Among such ROS, hydrogen peroxide （H202） is relatively stable, and can be conveniently and accurately quantified. Thus, the quantification of plant H202 could be applied as a stress indicator for riparian and aquatic vegetation management approaches while evaluating the conditions of a plant species within a habitat. This study presents an approach for elucidating the applicability of H202 as a quantitative indicator of environmental stresses on plants, particularly for vegetation management. Submerged macrophytes and riparian species were studied under laboratory and field conditions （Lake Shinji, Saba River, Eno River, and Hii River in Japan） for H202 formation under various stress conditions. The results suggest that H202 can be conveniently applied as a stress indicator in environmental management.

A size-gradient hypothesis for alpine treeline ecotones

Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.

典型荒漠灌木叶片功能性状特征随降水梯度的变化研究

自然降水是干旱地区植被重要的水分来源,为了探明荒漠灌木叶片在降水变化的应对对策,以典型荒漠灌木为研究对象,测定不同降水条件下叶片形态性状和化学计量指标,分析其叶片功能性状的总体特征及各个功能性状与环境因子的关系。结果表明:(1)红砂(Reaumuria soongorica)叶片肉质化程度和含水量随自然降水量的减少呈逐渐增大的趋势;盐爪爪(Kalidium foliatum)叶片组织密度随自然降水量的减少整体呈增大的趋势;(2)红砂和白刺(Nitraria tangutorum)C含量、白刺和珍珠猪毛菜(Salsola passerina)叶片N含量随自然降水量的减少整体呈增大的趋势;珍珠猪毛菜和盐爪爪叶片N∶P均小于14,即其在生长发育中主要受氮素限制;(3)红砂、白刺和盐爪爪叶片组织密度与年均降水量呈正相关关系;红砂、白刺的比叶面积与海拔呈负相关关系,红砂、白刺、珍珠猪毛菜的P含量与海拔呈负相关关系。综上所述,在干旱环境中,不同的植物表现出不同的生态适应策略,其中盐爪爪通过减小比叶面积、增加叶组织密度,白刺和珍珠猪毛菜通过增加叶片N含量,红砂通过增加叶片的肉质化程度和含水量等来适应干旱少雨的荒漠环境;年均降水量和海拔是影响植物生长发育的主要限制环境因子。

集聚、迁徙与动态均衡:嵩山周边史前聚落的空间格局

运用GIS空间分析和环境指标测试方法,探讨嵩山周边的颍河上中游地区(龙山晚期,约4.2~4.0 ka B.P.)、双洎河上游地区(新砦时期,约4.0~3.8 ka B.P.)和洛阳盆地的伊河—洛河中游地区(二里头时期,约3.8~3.5 ka B.P.)的3个遗址群的时空特征。结果表明:(1)标准差椭圆分析和核密度分析结果显示,颍河上游聚落群和二里头聚落群的空间集聚特征显著,集聚度分别为0.21,0.66;而新砦聚落群的集聚度仅为0.04,聚落呈显著的离散特征。(2)Voronoi资源域分析显示,从龙山晚期到二里头时期聚落的资源域逐渐减小,由6.83 km 2减少至0.36 km 2,表明单位土地的农业效率显著提高。(3)聚落的位序-规模拟合结果显示,颍河上游聚落和二里头聚落的首位度突出,核心聚落规模较大,空间集聚维数大于1,反映两个时期聚落规模的两极分化较为显著。(4)集聚是史前聚落空间均衡的一般模式,随着生产力发展而表现出不同的空间格局。

Elevational diversity gradients across seed plant taxonomic levels in the Lancang River Nature Reserve： role of temperature, water and the mid-domain effect

It remains unclear whether the elevational diversity gradients observed in seed plants across different taxonomic levels （family, genus, and species） are driven by the same macro-environmental variables. In this study, seed plant elevational distribution data from the Lancang River Nature Reserve （Yunnan, China） were used to investigate spatial patterns in diversity and their environ- mental correlates, comparing across taxonomic levels. Environmental variables included energy availability, climate seasonality and environmental heterogeneity. All taxonomic levels （family, genus, and species） were found to have strong elevational richness gradients, with the strength of the gradient weakening at higher taxonomic levels. Spatial patterns in richness were explained by a combination of contemporary environmental variables and the mid-domain effect at all taxonomic levels. The independent effects of temperature- and precipitation-related variables were similar in explaining geographical patterns of family, genus and species richness. Energy, seasonality and heterogeneity variables influenced seed plant spatial richness at different taxonomic levels in similar ways.

DEVELOPMENT OF A TROPICAL CYCLONE IN BAROTROPIC ENVIRONMENTAL FLOWS

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