Two Ultraviolet Radiation Datasets that Cover China

Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.

神农架国家公园体制试点特色与建议

神农架完好保留了我国北亚热带山地丰富独特的物种多样性和生态系统类型及其生物生态学过程,是公认的全球生物多样性保护关键地区,也是具有地理标志意义的最重要的国家生态安全屏障区之一。神农架自然地域总面积12,837.42km2,其中,湖北省有11,050.60km2,占总面积的86.1%;重庆市有1,498.23km2,占11.7%;陕西省有288.59 km2,占2.2%。海拔1,000m以下的区域有4,618.91 km2,占总面积的36.0%;1,000–1,500m有6,945.75 km2,占54.1%;2,000–3,000 m有1,271.88 km2,占9.9%;3,000m以上仅有0.88km2(徐文婷等,2019)。

重度砍伐后极小种群野生植物崖柏群落结构动态

砍伐导致濒危植物种群个体数量减少,群落结构改变,加剧物种灭绝风险。崖柏(Thuja sutchuenensis)为典型极小种群野生植物,森林砍伐是导致其种群数量急剧下降的主要原因。但是,到目前为止,有关崖柏种群及其群落对砍伐的响应鲜有报道。本研究以重度砍伐后的崖柏群落为研究对象,基于对崖柏群落固定样地的调查和两次复查,对比分析了伐后崖柏种群径级结构、种群生存力、物种多样性及其群落结构动态等特征。结果表明:崖柏残存群落伐后13年崖柏种群个体数量增加了22.58%,其中幼苗幼树占85.71%,而崖柏种群生存率下降25.43%,种群死亡密度和危险率分别增加了24.12%和28.62%。崖柏群落物种丰富度和Shannon-Wiener指数分别增加96.43%和33.35%。研究结果表明,砍伐使崖柏种群生存力及其在群落中的优势度持续下降,崖柏占优势的针阔混交林有向阔叶林演替的趋势,崖柏种群受到严重威胁,亟需采取紧急保护措施。

Asymmetric competition for light varies across functional groups

Aims Asymmetric competition for light may depress the growth rates(GRs)to different extents for different-sized tree individuals.Various responses of different functional groups to light availability result that tree individuals of different functional groups may experience different competition intensities,e.g.canopy and deciduous species grow faster and demand more light than understory and evergreen species.In this study,we estimated the effects of asymmetric competition for light using individual GRs and explored the effects of asymmetric competition on growth among different functional groups(e.g.canopy vs.understory species and deciduous vs.evergreen species).Methods We measured growth in circumference to determine the radial increments of a total of 2233 stems with diameter at breast height≥5.0 cm in a permanent plot(140×80 m^(2))located in a typical evergreen and deciduous broadleaved mixed forest on Mt Shennongjia,China.All of the measurements were carried out at~6-month intervals every April and October from 2012 to 2014,and biomass of each individual was calculated based on its diameter and species-specific allometry.We then calculated GRs of annual biomass growth(growth between October and the next October).Considering the hypothesis that asymmetric competition for light among trees of different sizes may result in a steeper allometric growth curve with increasing tree size,we further divided the sampled trees into different subsets according to their height,at intervals of 1 m,and then fitted the scaling relationship between the logarithm of the biomass GR(logGR)and the logarithm of diameter(logD)for each height class using standardized major axis regression.Finally,we used simple linear regression to test whether the scaling exponent was related to tree height.The above analyses were conducted for the annual growth of all tree species,canopy species,understory vs.treelets species and deciduous vs.evergreen species.Important findings We observed a concave curve for the relationship between logGR and logD with an increase in the scaling exponent between logGR and logD with increasing tree height.This pattern held for the annual growth of canopy species and deciduous species but not for the annual growth of understory species,treelets or evergreen species.These results suggest that asymmetric competition for light is more important in regulating the GRs of the fast-growing species,such as canopy species and deciduous species,than those of shade-tolerant species,such as understory species,treelets and evergreen species.

C:N:P stoichiometry of Ericaceae species in shrubland biomes across Southern China:influences of climate,soil and species identity

Aims Carbon(C),nitrogen(N)and phosphorus(P)stoichiometry strongly affect functions and nutrient cycling within ecosystems.However,the related researches in shrubs were very limited.In this study,we aimed to inves-tigate leaf stoichiometry and its driving factors in shrubs,and whether stoichiometry significantly differs among closely related species.Methods We analyzed leaf C,N and P concentrations and their ratios in 32 species of Ericaceae from 161 sites across southern China.We examined the relationships of leaf stoichiometry with environmen-tal variables using linear regressions,and quantified the interactive and independent effects of climate,soil and species on foliar stoi-chiometry using general linear models(GLM).Important Findings The foliar C,N and P contents of Ericaceae were 484.66,14.44 and 1.06 mg g−1,respectively.Leaf C,N and P concentrations and their ratios in Ericaceae were significantly related with latitude and altitude,except the N:P insignificantly correlated with latitude.Climate(mean annual temperature and precipitation)and soil properties(soil C,N and P and bulk density)were significantly influenced element stoichiom-etry.The GLM analysis showed that soil exerted a greater direct effect on leaf stoichiometry than climate did,and climate affected leaf traits mainly via indirect ways.Further,soil properties had stronger influ-ences on leaf P than on leaf C and N.Among all independent factors examined,we found species accounted for the largest proportion of the variation in foliar stoichiometry.These results suggest that species can largely influence foliar stoichiometry,even at a lower taxonomic level.

中国植被图(1:1000000)现实性更新

植被图是生物多样性保护、生态学研究、植被管理与恢复和国家决策的重要辅助信息源.我国上一代植被图,即中国植被图(1:1000000),是由逾250位生态学家组成的团队自20世纪80年代花了20多年完成的.但是,随着过去30多年间的快速发展,我国的植被分布与植被类型发生了剧烈的变化,对上一代植被图进行现实性更新已成为迫在眉睫的需求.本文使用了一种"众源采集-变化检测-遥感分类-专家审核"的策略尝试对中国植被图(1:1000000)进行现实性更新.本研究共收集了203024条地面调查数据,并有50余位植被生态学家参与到专家审核的工作中.更新后的植被图包含12个植被型组、55个植被(亚)型和866个(亚)群系类别,精度在植被型组、植被(亚)型和(亚)群系水平上分别为64.8%,61%和40%.与上一代植被图相比,过去30多年间的人类活动和气候变化导致了我国约330万km^2植被类型发生了变化.更新后的植被图将会有助于理解和管理我国的陆地生态系统.

Distribution of shrublands in relation to soil and climate in mid-subtropical China

Aims Understanding relationships between vegetation and environments is of importance for ecosystem restoration and management.However,information on how environments influence the floristic patterns of shrublands is lack,especially in the subtropical China.In this study,we explored how environments regulate species composition of shrublands at landscape scale in mid-subtropical China.Methods We investigated species composition and measured the climate and soil environments for 207 shrubland plots in mid-subtropical China(24°39′-30°08′N,108°47′-114°15′E).We applied a hierarchical cluster analysis and indicator species analysis based on the Bray-Curtis similarity index to identify the main shrubland types and employed principal coordinate analysis(PCoA)to explore the relationship between floristic composition and environment.Important Findings We identified four shrubland types occurring in different environmental conditions.Montane shrubland,dominated by species suitable for cool climates(e.g.Rhododendron simsii),were distributed in steep areas at comparatively high altitudes;foothill shrubland,dominated by mesophilous species(e.g.Loropetalum chinense),were distributed in low mountains and hills;pioneer shrubland,dominated by fast grow and short-life cycles species(e.g.Rhus chinensis),were distributed at low altitudes with dense population;and finally,limestone shrubland,dominated by calcicole plants(e.g.Coriaria nepalensis),were distributed in the extensive karst areas.Communities occurring in high pH soils were completely separated from those in low pH soils according to the hierarchical cluster analysis.PCoA ordination associated the four types with distinct edaphic and climatic gradients.Soil pH explained 63.3%of variation in PCoA,followed by soil depth and soil bulk density.

环境因子对叶氮、磷含量异速生长关系的属水平差异的影响

植物叶片中氮(N)、磷(P)含量的异速生长关系表明了植物对这两种元素的相对投入。而,现有的研究很少关注这一关系在分类单元之间的差异及其成因。本研究基于来自全国1733个样地,属于46个木本被子植物属的2483个叶片样品,利用异速生长方程([N]=α[P]β)分别计算了各属的叶氮、磷含量异速生长指数(β_(L))。然后利用谱系路径分析检验了这些属的气候和土壤生态位条件如何影响属间的β_(L)的差异。生活在贫磷土壤中的属更可能表现出更高的β_(L),即相对于氮而言更强的磷积累,这可能表明了植物对磷限制的抵抗倾向。此外,各属的β_(L)与相对应的土壤氮、磷含量异速生长指数(β_(S))正相关,这可能表明了叶养分的变化受制于作为来源的土壤养分的变化。最后,包括温度和湿度在内的气候因子不会直接影响β_(L)的属间变化,但可能通过调节土壤养分水平发挥间接的作用。谱系关系不会影响各属β_(L)随环境梯度的变化。这些结果揭示了植物对氮、磷摄取的权衡关系可能受属生态位,特别是土壤生态位的影响,表明了β_(L)可以作为一项反映植物养分利用特征如何响应生态位差异的功能属性。

Strong restrictions on the trait range of co-occurring species in the newly created riparian zone of the three Gorges Reservoir Area, china

Aims community assembly links plant traits to particular environmental conditions.Numerous studies have adopted a trait-based approach to understand both community assembly processes and changes in plant functional traits along environmental gradients.In most cases these are long-established,natural or semi-natural environments.However,increasingly human activity has created,and continues to create,a range of new environmental conditions,and under-standing community assembly in these‘novel environments’will be increasingly important.Methods Built in 2006,the three Gorges Dam,largest hydraulic project in china,created a new riparian area of 384 km^(2),with massively al-tered hydrology.this large,newly created ecosystem is an ideal platform for understanding community assembly in a novel environment.We sampled environment variables and plant communities within 103 plots located in both the reservoir riparian zone(RRZ)and adjacent non-flooded and semi-natural upland(Upland)at the three Gorges Reservoir Area.We measured six traits from 168 plant species in order to calculate community-level distribution of trait values.We expected that the altered hydrology in RRZ would have a profound effect on the community assembly process for the local plants.Important Findingsconsistent with previous work on community assembly,the dis-tribution of trait values(range,variance,kurtosis and the standard deviation of the distribution neighbor distances)within all plots was significantly lower than those from random distributions,indicat-ing that both habitat filtering and limiting similarity simultaneously shaped the distributions of traits and the assembly of plant commu-nities.considering the newly created RRZ relative to nearby sites,community assembly was different in two main ways.First,there was a large shift in the mean trait values.compared to Upland commu-nities,plant communities in the RRZ had higher mean specific leaf area(SLA),higher nitrogen per unit leaf mass(Nmass),and lower max-imum height(MH).Second,in the RRZ compared to the Upland,for the percentage of individual plots whose characteristic of trait values was lower than null distributions,the reductions in the community-level range for SLA,Nmass,nitrogen per unit leaf area(Narea)and phos-phorus per unit leaf area(Parea)were much larger,suggesting that the habitat filter in this newly created riparian zone was much stronger compared to longer established semi-natural upland vegetation.this stronger filter,and the restriction to a subset of plants with very similar trait values,has implications for predicting riparian ecosystems’responses to the hydrological alterations and further understanding for human’s effect on plant diversity and plant floras.

Structures and topographical pattern of the tree layer of Fagus engleriana-Cyclobalanopsis oxyodon community in Shennongjia area, Hubei Province, China

Shennongjia represents an area of considerable plant biodiversity,not only for China but for the whole world.The numerous species are distributed along an altitude gradient.The genus Fagus,commonly known as Beeches,constitutes one of the dominant woody species of the humid temperate forests in China.This paper deals with the community structure of a mixed,broadleaved deciduous-evergreen beech forest dominated by the Fagus engleriana and Cyclobalanopsis oxyodon,which occurs along an altitude gradient range in this area.The community consists of 46 woody species,belonging to 22 families and 27 genera.The tree layer can be divided into three sub-strata.The upper layer is composed of deciduous trees,80.7%of which is F.engleriana.The second and third layers are dominated by the evergreen species,such as C.oxyodon and the Rhododendron hypoglaucum.These species increase from 55.9%in the second layer to 80.5%in the third,and regeneration at that rate allows us to assume that the stability of the community may be guaranteed.The micro-site heterogeneity plays an important role in maintaining species diversity in plant communities.In this research,a terrain surface of 0.96hm 2 was simulated using the digital elevation model(DEM)in order to analyze the influence of the topography on plant community structures on a small scale.The slope relief aspect obtained with the DEM showed an accentuated heterogeneity.Semivariance analysis was used to measure the heterogeneity scale.The range and nugget variance of the semivariograms for slope were 285.8 and 280.5,respectively;for aspect,were 21.8 and 498,respectively.The elevated value of the nugget variance suggested that even on a small scale,the topographic variations influenced the species distribution.Twenty-four species were selected to estimate the correlation coefficient between the slope,aspect,and orientation.Then based on the correlation results using the Square Euclidean Distance cluster analysis,the 24 species were divided into four groups.

The Janzen-Connell effect on the population dynamics of a Fagus engleriana- Cyclobalanopsis oxyodon community in a subtropical zone of China

The Janzen-Connell(J-C)hypothesis provides a mechanism explaining the high species diversity in tropical rainforests.It postulates that predation could cause greater mortality on seeds and seedlings near their parental trees.In this study,we tested the hypothesis in a subtropical zone,a mixed evergreen-deciduous broad-leaved forest dominated by the Fagus engleriana and Cyclobalanopsis oxyodon.The study area was in the Shennongjia region,a key area of biodiversity conserva-tion in both China and the world.The recruitment probability index was used to detect the J-C effect on nine species of the community,which were more than 50 individuals.Six large adults of each species were selected,and the numbers of saplings and adults were counted at the distance intervals of 0–5,5–10,10–15,15–20,and 20–25m from each focal tree.Two species in saplings stage and six in adult stage supported the J-C hypothesis,but theirχ2 was not significant.Three species,the F.engleri-ana,Rhododendron hypoglaucum,and Toona sinensis,showed a strong Hubbell pattern in the adult stage.Because of these results,we reject the J-C hypothesis and conclude that species could recruit near the conspecific trees in subtropical forest.The reasons why the J-C hypothesis fails to explain the species diversity in this community are the shortage of seed-consuming agents of subtropical forest and the influence of microsite topo-graphic variation.