Growth-form regulates the altitudinal variation of interspecific seed mass of woody plants in Mt. Dalaoling,the Three Gorges Region,China

Aims Seed size is one of the most important characteristics of plant seeds, and has significant implications in plant ecological functions. Exploring the altitudinal pattern of seed size would help to detect environmental constraints on species distribution and understand the linkage between plant ecological function traits Methods The present study measured the quantitative features of seed size, including weight of 1 000 grain seeds, lengths of longer and shorter axes, and analyzed the relationships between seed size and altitude, as well as the influence of growth form. Seed samples were all collected from 201 locally common woody plants (belonging to 59 families and 87 genera) in the Dalaoling Natural Reserve in Yichang City, Hubei Province.Important findings Measured values of the seed mass, the longer axis, and the shorter axis of the 201 woody plant species all follow the lognormal distribution. Measurements of seed mass vary across five orders of magnitude. Significant correlation was found between seed mass, seed length of the longer and shorter axes (R² = 0.755; 0.819; 0.630, p < 0.01). Moreover, seed mass of trees and small trees are significantly heavier than those of shrubs and woody vines. Seed mass values of evergreen broad leaved species are significantly heavier than those of deciduous broad leaved species and needle leaved species. Seed mass of all 201 species shows a slightly but statistically significant decreasing trend with the increase of altitude. In addition, altitudinal patterns of seed mass varied between species with different growth form. Our results indicated the variation of altitudinal trends of seed mass for different structural components of plant communities, implying the local community structure as a critical aspect of variation in macro-ecological patterns.     

山西关帝山森林群落物种、谱系和功能多样性海拔格局

探索和揭示生物多样性的空间格局和维持机制是生态学和生物地理学研究的热点内容, 但综合物种、系统进化和功能属性等方面的多样性海拔格局研究很少。该文以关帝山森林群落为研究对象, 综合物种、谱系和功能α和β多样性指数, 旨在初步探讨关帝山森林群落多样性海拔格局及其维持机制。研究结果表明: 随着海拔的升高(1 409-2 150 m), 关帝山森林群落物种丰富度指数(S)、谱系多样性指数(PD)和功能丰富度指数(FRic)整体上表现出上升的趋势, 特别是海拔1 800 m以上区域。随着海拔的升高, 总β多样性(β_total)和更替(β_repl)上升趋势明显, 而丰富度差异(β_rich)则逐渐下降。不同生活型植物的物种、谱系和功能多样性海拔格局差异较大。随着海拔的升高, 草本植物S和物种多样性指数(H′)上升趋势高于木本植物。影响草本植物S分布的主要因素是地形因子, 而影响木本植物S分布的主要因素是历史过程。随着海拔的升高, 木本植物β_total上升趋势要比草本植物明显。随着海拔的升高, 木本植物β_repl和β_rich分别表现出单峰格局和“U”形格局, 而草本植物β_repl和β_rich则分别表现出单调递增和单调递减的格局。随着环境差异和地理距离的增加, 群落间物种、谱系和功能β多样性显著增加。环境差异(环境过滤)对木本植物的β多样性具有相对较强的作用; 而环境差异(环境过滤)和地理距离(扩散限制)共同作用于草本植物的β多样性。     

Growth-form regulates the altitudinal variation of interspecific seed mass of woody plants in Mt. Dalaoling,the Three Gorges Region China北大核心CSCD

Aims: Seed size is one of the most important characteristics of plant seeds, and has significant implications in plant ecological functions. Exploring the altitudinal pattern of seed size would help to detect environmental constraints on species distribution and understand the linkage between plant ecological function traits. Methods: The present study measured the quantitative features of seed size, including weight of 1 000 grain seeds, lengths of longer and shorter axes, and analyzed the relationships between seed size and altitude, as well as the influence of growth form. Seed samples were all collected from 201 locally common woody plants (belonging to 59 families and 87 genera) in the Dalaoling Natural Reserve in Yichang City, Hubei Province. Important findings: Measured values of the seed mass, the longer axis, and the shorter axis of the 201 woody plant species all follow the lognormal distribution. Measurements of seed mass vary across five orders of magnitude. Significant correlation was found between seed mass, seed length of the longer and shorter axes (R2 = 0.755; 0.819; 0.630, p > 0.01). Moreover, seed mass of trees and small trees are significantly heavier than those of shrubs and woody vines. Seed mass values of evergreen broad leaved species are significantly heavier than those of deciduous broad leaved species and needle leaved species. Seed mass of all 201 species shows a slightly but statistically significant decreasing trend with the increase of altitude. In addition, altitudinal patterns of seed mass varied between species with different growth form. Our results indicated the variation of altitudinal trends of seed mass for different structural components of plant communities, implying the local community structure as a critical aspect of variation in macro-ecological patterns.     

Distribution of Vascular Plant Species Richness Along an Elevational Gradient in the Dongling Mountains, Beijing, China

Quantifying spatial patterns of species richness and determining the processes that give rise to these patterns are core problems In blodlveralty theory. The aim of the present paper was to more accurately detect patterns of vascular species richness at different scales along altitudinal gradients in order to further our understanding of biodlverslty patterns and to facilitate studies on relationships between biodiversity and environmental factors. Species richness patterns of total vascular plants species, including trees, shrubs, and herbs, were measured along an altitudinal gradient on one transect on a shady slope in the Dongling Mountains, near Beijing,China. Direct gradient analysis, regression analysis, and geostatistics were applied to describe the spatial patterns of species richness. We found that total vascular species richness did not exhibit a linear pattern of change with altitude, although species groups with different ecological features showed strong elevational patterns different from total species richness. In addition to total vascular plants, analysis of trees, shrubs, and herbs demonstrated remarkable hierarchical structures of species richness with altitude (i.e. patchy structures at small scales and gradients at large scales). Species richness for trees and shrubs had similar spatial characteristics at different scales, but differed from herbs. These results indicated that species groups with similar ecological features exhibit similar biodlveraity patterns with altitude, and studies of biodiversity based on species groups with similar ecological properties or life forms would advance our understanding of variations in species diversity. Furthermore, the gradients or trends appeared to be due mainly to local variations in species richness means with altitude. We also found that the range of spatial scale dependencies of species richness for total vascular plants, trees, shrubs, and herbs was relatively large. Thus, to detect the relationships betweenspecies richness with environmental factors along altitudinal gradients, it was necessary to quantify the scale dependencies of environmental factors in the sampling design or when establishing non-linear models.     

Resorption proficiency and efficiency of leaf nutrients in woody plants in eastern China

Aims (i) To explore variations in nutrient resorption of woody plants and their relationship with nutrient limitation and (ii) to identify the factors that control these variations in forests of eastern China.Methods We measured nitrogen (N) and phosphorus (P) concentrations in both green and senesced leaves of 172 woody species at 10 forest sites across eastern China. We compared the nutrient resorption proficiency (NuRP) and efficiency (NuRE) of N and P in plant leaves for different functional groups; we further investigated the latitudinal and altitudinal variations in NuRP and NuRE and the impacts of climate, soil and plant types on leaf nutrient resorptions.Important findings On average, the leaf N resorption proficiency (NRP) and P resorption proficiency (PRP) of woody plants in eastern China were 11.1mg g ? 1 and 0.65 mg g ? 1, respectively; and the corresponding N resorption efficiency (NRE) and P resorption efficiency (PRE) were 49.1% and 51.0%, respectively. Angiosperms have higher NRP (are less proficient) values and lower NRE and PRE values than gymnosperms, but there are no significant differences in NRP, PRP and PRE values between species with different leaf habits (evergreen vs. deciduous angiosperms). Trees have higher NRE and PRE than shrubs. Significant geographical patterns of plant nutrient resorption exist in forests of eastern China. In general, NRP and PRE decrease and PRP and NRE increase with increasing latitude/altitude for all woody species and for the different plant groups. Plant functional groups show more controls than environmental factors (climate and soil) on the N resorption traits (NRP and NRE), while site-related variables present more controls than plant types on PRP and PRE. NRP increases and PRP and NRE decrease significantly with increasing temperature and precipitation for the overall plants and for most groups, except that significant PRE–climate relationship holds for only evergreen angiosperms. Leaf nutrient resorption did not show consistent responses in relation to soil total N and P stoichiometry, probably because the resorption process is regulated by the relative costs of drawing nutrients from soil versus from senescing leaves. These results support our hypothesis that plants growing in P-limited habitats (low latitudes/altitudes or areas with high precipitation/temperature) should have lower PRP and higher PRE, compared with their counterparts in relatively N-limited places (high latitudes/altitudes or areas with low precipitation/temperature). Our findings can improve the understanding of variations in N and P resorption and their responses to global change, and thus facilitate to incorporate these nutrient resorption processes into future biogeochemical models.     

湖北星斗山地形变化对不同生活型植物叶功能性状的影响

探究地形变化对不同生活型植物叶功能性状的影响有助于深入理解森林群落物种组成的维持特征。该研究以湖北星斗山常绿落叶阔叶混交林为研究对象, 测量了50个样地中224种木本植物的叶面积、叶厚度、叶干质量、叶干物质含量和比叶面积, 运用单因素方差分析揭示了乔木、灌木和木质藤本的叶功能性状变异特征, 并采用偏曼特尔检验分别从群落水平和物种水平分析了地形变化对不同生活型木本植物叶功能性状的影响。研究发现: 不同生活型植物叶性状变异系数分布范围为23.42%-110.45%; 不同生活型之间的植物叶功能性状差异明显。群落水平上, 海拔与乔木叶干质量、灌木叶面积和木质藤本叶厚度显著正相关, 坡度仅对灌木和木质藤本比叶面积具有显著影响, 坡向与灌木叶厚度、叶干质量和比叶面积显著正相关。物种水平上, 海拔比坡度和坡向对植物叶功能性状影响更为显著, 且不同物种对地形变化的敏感度不一致; 在控制空间结构影响后, 地形因子对植物叶功能性状的影响降低。该研究结果表明, 不同生活型植物的叶功能性状对地形变化的响应格局不同, 这可能是星斗山常绿落叶阔叶混交林植物多样性的主要维持机制。     

Morphological variation and floral abnormalities in a trigger plant across a narrow altitudinal gradient

Local adaptation in alpine plants has been demonstrated across wide altitudinal gradients, but has rarely been examined across the alpine‐to‐montane transition that often encompasses only a few hundred metres. Here we characterize morphological variation in leaf and floral characteristics of the trigger plant Stylidium armeria along a narrow altitudinal gradient in the Bogong High Plains in Victoria. Across this gradient, which encompasses the high‐elevation limit of this species, linear changes were found for floral scape height, leaf length and flower number. All these traits decreased with increasing altitude, whereas the frequency of abnormal flowers increased. When plants were grown in a common garden environment, an altitudinal pattern for flower abnormalities was no longer detected. However, altitudinal patterns for leaf length and scape height were maintained, albeit weaker than in the field. This indicates heritable variation for these morphological traits; the altitudinal patterns are likely to reflect the effects of selection by environmental factors that vary with altitude. Selection pressures remain to be identified but have generated both cogradient and countergradient patterns of variation.     

The nutritional status of plants from high altitudes

Summary Are plants at high altitudes short in nutrients? In order to answer this question the mineral nutrient content of leaves from over 150 plant species from 9 different mountain areas of all major climatic zones were analyzed (Kjeldahl nitrogen in all, phosphate in half of the samples, K, Mg, Mn, Ca in the Alps only). The majority of data are from herbaceous perennials, but shrubs and trees were studied as well. N-partitioning was studied in 45 herbaceous species from contrasting altitudes in the Alps. The survey falls into three categories: (1) comparisons of whole communities of species from contrasting altitudes, (2) analysis of altitudinal gradients, and (3) additional collections from high altitude sites alone. Unlike the other mineral nutrients, nitrogen content follows consistent altitudinal and latitudinal trends. The higher altitude sample always had higher N content per unit leaf area, irrespective of life form, wherever comparable plants (the same or related species) were investigated at contrasting altitudes. N content per unit dry weight (%) increased with altitude in herbaceous plants (in some species >4%), but was remarkably stable in evergreen woody plants (around 1%). The mean fraction of total plant N allocated to leaves of herbaceous plants in the Alps was the same at low and high altitude (1/3 of total). Leaf N (%) from the regional upper limits of higher plant life reveals a latitudinal decrease from subarctic to equatorial mountains, which may be related to the duration of annual leaf activity. Since mean N content per leaf area hardly differs between the uppermost sites, life span expectation (sink-duration) seems to control carbon investments rather than N input per leaf area. The growth of leaves at high altitude seems to be controlled in a way that leads to comparatively high nutrient contents, which in turn support high metabolic activity. Inherent developmental growth constraints inhibit nutrient dilution in the plant body and thus defy the application of classical concepts of plant-nutrient versus soil-nutrient relations developed for lowlands and in particular for cultivated plants. The results re-emphasize the global significance of links between nitrogen content, leaf sclerophylly, leaf longevity and photosynthetic capacity.Dedicated to Prof. Walter Larcher on the occasion of his 60th birthday, with thanks for leading me to comparative plant ecology     

Altitudinal variation in stomatal conductance,nitrogen content and leaf anatomy in different plant life forms in New Zealand

Summary This study is part of a series of investigations on the influence of altitude on structure and function of plant leaves. Unlike most other mountain areas, the Southern Alps of New Zealand provide localities where physiologically effective moisture stress occurs neither at high nor at low elevation, but the changes in temperature and radiation with elevation are similar or even steeper than in most other regions. In comparison with results from other mountains, where moisture may impair plant functioning at low elevation, this study allows an estimation of the relative role of water for the expression of various leaf features typically associated with alpine plants. Maximum leaf diffusive conductance (g), leaf nitrogen content (LN), stomatal density (n) and distribution, as well as area (A), thickness (d) and specific area (SLA) of leaves were studied. Three different plant life forms were investigated over their full altitudinal range (m): trees, represented by Nothofagus menziesii (1,200 m), ericaceous dwarf shrubs (1,700 m), and herbaceous plants of the genus Ranunculus (2,500 m). In all three life forms g, LN, and n increased, while SLA and A decreased with elevation. Recent investigations have found similar trends in other mountains from the temperate zone, but the changes are larger in New Zealand than elsewhere. Herbs show the greatest differences, followed by shrubs and then trees.It is concluded that g is dependent upon light climate rather than water supply, whereas SLA and related structural features appear to be controlled by the temperature regime, as they show similar altitudinal changes under different light and moisture gradients. The higher leaf nitrogen content found at high elevations in all three life forms, suggests that metabolic activity of mature leaves is not restricted by low nitrogen supply at high altitude. In general, the leaves of herbaceous plants show more pronounced structural and functional changes with altitude than the leaves of shrubs and trees.     

Plant species and growth form richness along altitudinal gradients in the southwest Ethiopian highlands

Questions: Do growth forms and vascular plant richness follow similar patterns along an altitudinal gradient? What are the driving mechanisms that structure richness patterns at the landscape scale? Location: Southwest Ethiopian highlands. Methods: Floristic and environmental data were collected from 74 plots, each covering 400 m². The plots were distributed along altitudinal gradients. Boosted regression trees were used to derive the patterns of richness distribution along altitudinal gradients. Results: Total vascular plant richness did not show any strong response to altitude. Contrasting patterns of richness were observed for several growth forms. Woody, graminoid and climber species richness showed a unimodal structure. However, each of these morphological groups had a peak of richness at different altitudes: graminoid species attained maximum importance at a lower elevations, followed by climbers and finally woody species at higher elevations. Fern species richness increased monotonically towards higher altitudes, but herbaceous richness had a dented structure at mid‐altitudes. Soil sand fraction, silt, slope and organic matter were found to contribute a considerable amount of the predicted variance of richness for total vascular plants and growth forms. Main Conclusions: Hump‐shaped species richness patterns were observed for several growth forms. A mid‐altitudinal richness peak was the result of a combination of climate‐related water–energy dynamics, species–area relationships and local environmental factors, which have direct effects on plant physiological performance. However, altitude represents the composite gradient of several environmental variables that were interrelated. Thus, considering multiple gradients would provide a better picture of richness and the potential mechanisms responsible for the distribution of biodiversity in high‐mountain regions of the tropics.     

Species richness and phylogenetic diversity of different growth forms of angiosperms across a biodiversity hotspot in the horn of Africa

Woody and herbaceous plants are differentially influenced by the environment, with non‐random association with the evolutionary history of these taxa and their traits. In general, woody plants may have climate‐dominated niches, whereas herbaceous plants may have edaphic and microhabitat‐dominated niches. Here, we explored and mapped how the patterns of species richness, phylogenetic diversity, and structures of total, woody, and herbaceous plants vary across the geographical regions and with respect to 12 environmental variables across Ethiopia and Eritrea, in the horn of Africa. Our result showed that both richness and phylogenetic diversity had almost the same tendency in total woody and herbaceous plants, in which they showed positive relationships with annual precipitation, precipitation annual range of climate, all the three variables of topography, and total nitrogen and total extractable phosphorus of soil, and negative relations with mean annual temperature. Compared with the total and herbaceous plants, the environmental variables explained greater variance both in the standardized effect size phylogenetic diversity and net relatedness index for woody plants. Our results highlight that, on the large spatial scales, the environmental filtering process has played a greater role in structuring species into local communities for woody plants than for herbaceous plants.     

Resorption efficiency of leaf nutrients in woody plants on Mt. Dongling of Beijing,North China

Aims To explore resorption efficiency of nitrogen (NRE) and phosphorus (PRE) of woody plants in relation to soil nutrient availability, climate and evolutionary history, in North China.Methods We measured concentrations of nitrogen ([N]) and phosphorus ([P]) in both full expanded mature green and senescent leaves of the same individuals for 88 woody species from 10 sites of Mt. Dongling, Beijing, China. We built a phylogenetic tree for all these species and compared NRE and PRE among life forms (trees, shrubs and woody lianas) and between functional groups (N-fixers and non-N-fixers). We then explored patterns of NRE and PRE along gradients of mean annual temperature (MAT), soil inorganic N and available P, and phylogeny using a general linear model.Important findings Mass-based NRE (NRE m) and PRE (PRE m) averaged 57.4 and 61.4%, respectively, with no significant difference among life forms or functional groups. Neither NRE m nor PRE m exhibited significant phylogenetic signals, indicating that NRE m and PRE m were not phylogenetically conserved. NRE m was not related to [N] in green leaves; PRE m was positively correlated with [P] in green leaves; however, this relationship disappeared for different groups. NRE m decreased with [N] in senescent leaves, PRE m decreased with [P] in senescent leaves, for all species combined and for trees and shrubs. NRE m decreased with soil inorganic N for all species and for shrubs; PRE m did not exhibit a significant trend with soil available P for all species or for different plant groups. Neither NRE m nor PRE m was significantly related to MAT for overall species and for species of different groups.     

31种木本植物开花物候与系统发育的关系

植物物候通常被认为是由环境因素,如降水、温度和日照长度所决定,然而环境因素是否是物候唯一的决定因素仍然存在很大争议。谱系结构表征了植物在进化上的顺序,该发育时序是否对物候产生影响,当前仍然未知。在调查2016年春季新疆乌鲁木齐市最常见的31种木本植物的初始开花时间、败花时间和开花持续时间的基础上,通过分析植物开花物候的分布特征、开花物候在乔灌木间的差别、以及植物谱系距离与开花物候距离间的关系,试图揭示植物的开花物候和物种谱系(进化)顺序间的关系。结果表明:(1)新疆乌鲁木齐市31种木本植物的初始开花时间为4月18日±9d、败花时间为5月5日±12d、开花持续时间为(16±8)d;(2)乔木的初始开花时间和败花时间的标准差分别均低于灌木,乔木开花物候相对灌木更稳定;(3)乔木的初始开花和败花时间均显著早于灌木(P0.05),但开花持续时间在两者间未有显著性差异(P0.05);(3)31种木本植物间的初始开花时间距离、败花时间距离和开花持续时间距离均与物种谱系距离存在显著线性回归关系(P0.05)。综上可知:乔灌木在垂直空间上的分化使得木本植物的开花物候在植物生活型间存在不同。对植物的开花物候,除已被证明的降水、温度和日照长度等环境因素的影响外,物种进化顺序也可能造成了它在植物种间、时间和空间上的变异。     

Trade-offs between flowering time,plant height,and seed size within and across 11 communities of a QingHai-Tibetan flora

Flowering timing is of fundamental biological importance for its tight association with pre-flower growth states and subsequent reproduction success. Here, we selected plant height and seed size to represent plant growth and reproduction states, respectively, and analyzed their associations with flowering time in 11 communities together representing a QingHai-Tibetan flora. Trait associations were examined using Pearson correlation analyses (TIPs) and phylogenetically independent contrasts (PICs) within individual communities and meta-analyses across all communities. The results of TIPs-based and PICs-based analyses were generally congruent, although fewer contrasts were significant with PICs, probably because of low statistical power. Overall, flowering time was negatively correlated with seed size and plant height (i.e., plants with larger seeds and stature started flowering earlier) in various woody communities, but correlations were neutral or positive in herbaceous communities. The seed size–flowering time relationship was negative for woody and herbaceous perennials but not for annual herbs in most communities. The relationship between plant height and flowering time was negative for woody but positive for herbaceous plants. Moreover, the lack of difference in time–size relationships between anemophilous and entomophilous plants suggests that pollination type may only be a secondary force in controlling flowering phenology. Our studies demonstrate that environmental conditions, community structure, and plant life history strategies may affect community flowering time singly or in combination.     

不同植物类群物种丰富度垂直格局分形特征的比较

格局和过程一直是生态学的核心问题,该文应用“非布朗运动随机分形”模型,在北京东灵山远离人为干扰地区的阴坡设置了两条宽2 m的样带,描述和比较了暖温带落叶阔叶林区乔木、灌木、草本以及总的植物物种丰富度在不同尺度上沿海拔梯度变异特征,以及相关的生态过程。研究结果表明:1)直接梯度法刻画了植物物种丰富度在海拔梯度上的总体变化趋势,并不能从中获得更多的信息。“非布朗运动随机分形”模型揭示了不同尺度上物种丰富度的空间变化并能和生态过程相联系,研究表明该模型适合对乔木、灌木和草本植物物种丰富度的垂直梯度格局特征进行描述,但对总的植物物种丰富度有一定的局限性。2)乔木物种丰富度在海拔梯度上的变化主要受两种生态过程的控制,小尺度上分形维数接近于2,主要受独立的不具有长程相关的生态过程控制,呈近随机分布;大尺度上分形维数接近于1,主要受自相关范围大、具有长程关联特性的生态过程控制,随海拔上升呈近似单调下降的趋势。灌木和草本物种丰富度在海拔梯度上的变化主要受3种生态过程的控制,小尺度和大尺度上的特征与乔木相似;但在中等尺度上,分形维数接近于1.5,它们以近似布朗运动的形式变化。虽然乔木和灌木物种丰富度在海拔梯度上变化的尺度范围相似,但决定它们的主要生态过程完全不同,或相同的生态过程以截然不同的方式作用于两种不同的植物类群。总的植物物种丰富度在整个尺度范围内呈现标度不变性,这可能是由于决定其变化的生态过程作用尺度紧密相关,也可能因为该文研究范围的局限性。     

Correspondence analysis of functional groups in a riparian landscape

We used multivariate analysis and ordinations to characterize thecomposition and distribution of woody vegetation within the Ozark NationalScenic Riverways (ONSR), Missouri, USA. The objectives of the study were to: 1)evaluate patterns of woody species distributions along existing environmentalgradients; 2) determine if different classes of woody plants (i.e., dominantoverstory trees, all trees, understory trees, and shrubs) responded similarlytothe same suite of environmental variables; and 3) determine if discreteecotonaland/or ecoclinal vegetation patterns were present across the landscape. Woodyvegetation was sampled from 94 plots along 35 transects positioned at rightangles to the river channel. Sample plots were analyzed with DetrendedCorrespondence Analysis (DCA), Canonical Correspondence Analysis (CCA), andTWINSPAN. Overall, woody vegetation was correlated with several environmentalgradients, including elevation of the plot above the river, soil pH, soilmoisture, and soil particle size. Responses to secondary gradients differedamong the four classes of plants analyzed, however. CCA biplots of understorytrees indicated that patterns of those species were strongly correlated withslope through the plot and sand content of soil. CCA biplots of shrubs showedthat CCA axes were most strongly correlated with soil organic matter content,soil moisture, and silt content. Further, there was limited evidence fordiscrete assemblages of woody species, with the exception of streamsidevegetation. Instead, mixing of woody species was observed across a broadtransition zone. Because there is little correspondence between vegetationlayers, our results demonstrate including plant classes other than a subset ofcanopy dominant trees can provide additional resolution in characterizingvegetation responses along complex environmental gradients.     

Extinction risk of Chinese angiosperms varies between woody and herbaceous species

Aim

Understanding how species' traits and environmental contexts relate to extinction risk is a critical priority for ecology and conservation biology. This study aims to identify and explore factors related to extinction risk between herbaceous and woody angiosperms to facilitate more effective conservation and management strategies and understand the interactions between environmental threats and species' traits.

Location

China.

Taxon

Angiosperms.

Methods

We obtained a large dataset including five traits, six extrinsic variables, and 796,118 occurrence records for 14,888 Chinese angiosperms. We assessed the phylogenetic signal and used phylogenetic generalized least squares regressions to explore relationships between extinction risk, plant traits, and extrinsic variables in woody and herbaceous angiosperms. We also used phylogenetic path analysis to evaluate causal relationships among traits, climate variables, and extinction risk of different growth forms.

Results

The phylogenetic signal of extinction risk differed among woody and herbaceous species. Angiosperm extinction risk was mainly affected by growth form, altitude, mean annual temperature, normalized difference vegetation index, and precipitation change from 1901 to 2020. Woody species' extinction risk was strongly affected by height and precipitation, whereas extinction risk for herbaceous species was mainly affected by mean annual temperature rather than plant traits.

Main conclusions

Woody species were more likely to have higher extinction risks than herbaceous species under climate change and extinction threat levels varied with both plant traits and extrinsic variables. The relationships we uncovered may help identify and protect threatened plant species and the ecosystems that rely on them.     

高黎贡山种子植物物种丰富度沿海拔梯度的变化

物种丰富度沿海拔梯度的分布格局成为生物多样性研究的热点。为探讨中尺度区域物种丰富度沿海拔梯度的分布,本文以高黎贡山为研究对象,利用该地区的地方植物志资料,结合通过GIS生成的区域数字高程模型(DEM)数据,分析了该区域全部种子植物和乔木、灌木、草本三种生活型种子植物物种丰富度的垂直分布格局以及物种密度沿海拔梯度的变化特征。结果表明：(1)全部种子植物和不同生活型植物物种丰富度随着海拔的升高呈现先增加后减小的趋势,最大值出现在海拔1500—2000m的范围;(2)物种密度与海拔也呈现单峰曲线关系;(3)物种丰富度和物种密度分布格局的形成主要受海拔所反映的水、热状况组合以及物种分布的边界影响。     

What causes geographical variation in the species–area relationships? A test from forests in China

The increase of species richness with sampling area and the decrease with latitude and altitude are two of the most frequently studied patterns in biogeography. However, few studies have simultaneously examined these two patterns to investigate how species–area relationships (SAR) vary with latitude and altitude. In this study, we explore the spatial patterns of SAR in forests in China by investigating numbers of species by life form group (trees, shrubs and herbs) in 32 nested plots from 12 mountains ranging from 18.7°N to 51.9°N in latitude and from 300 to 3150 m in altitude. The slopes of the power law SAR (z‐values) decreased with increasing latitude for all life forms except herbaceous plants, and also decreased with increasing altitude for all life forms but not for shrubs. Latitude and altitude, as well as their interactions, together explained 65.4, 61.8, 48.9 and 45.3% of the variation in z‐values for overall species, trees, shrubs and herbaceous plants, respectively. In addition, actual evapotranspiration affected SAR significantly, but this effect varied significantly among life forms. We concluded that there are significant geographical patterns of SAR for China's forests, which is primarily controlled by energy availability.     

Spatial variability in woody species richness along altitudinal gradient in a lowland-dryland site, Lokapel Turkana, Kenya

The woody species richness patterns in three 2–4 km long transects, approximately 1–3 km apart in a lowland (600–700 m) dryland around Lokapel in Turkana northern Kenya was analyzed in 2003 at 200–500 m intervals using the Point-Centred Quarter (PCQ) method involving 51 observation points. Transect 1 and 2 were set along ephemeral runoff channels locally known as lagga with wet season flow westwards from the Lokapel Hills to the Turkwell River. Transect 3 was a cross-cutting profile dissecting the area initially downhill from the Lokapel Hills and later gently uphill eastwards towards Lokichar. The altitude at each of the 51 observation sites was recorded using a GPS and the woody species identified through local knowledge and taxonomic aids. The results showed that the overall integrated altitudinal gradient for the three transects was approximately 100 m. A total of 43 species of trees and shrubs were identified. The Shannon index showed that Transect 2 had the highest diversity of woody species followed by Transect 1 and Transect 3 while the Sorensen’s index indicated qualitative dissimilarity between all the transects. The results of regression analysis indicated that woody species richness increased linearly with elevation in only one transect but regression analysis of height of woody plants and altitude indicated that only about 20% of the variation in the height of woody plants was accountable by altitude. The spatial analysis of woody species-richness and altitudinal gradient showed a dual peak pattern with the main richness peak in low lying areas below 700 m which was mainly within or close to the riparian floodplain environment of the Turkwell River. A minor richness peak was also identified in higher lying areas around the Lokapel hills. The species richness pattern was similar to the hump-shaped altitudinal species-richness pattern which has been recorded widely around the world but mainly in large-scale studies.