黄河首曲-玛曲县高寒草甸沙化演替进程中群落结构及种群生态位特征

以甘肃省玛曲县高寒沙化草甸为对象,应用空间序列代替时间序列的方法,对其不同沙化演替阶段植物群落主要种群结构及其生态位特征进行了研究.结果表明:(1)随着沙化演替的进行,物种组成数呈单峰式曲线变化规律,在轻度沙化阶段物种数最多(43种),禾草类和豆科类物种的重要值和生态位宽度均呈逐渐减少规律,优势度逐渐减弱;在极度沙化阶段(除垂穗披碱草外)几乎完全消失,莎草类和杂类草一些物种的重要值和生态位宽度则均呈逐渐增大规律,优势度逐渐增加,并在重度或极度沙化阶段成为优势种、次优势种或重要伴生种;随沙化演替进程,蒲公英、狼毒和乳白香青等物种则表现出波动性,最后消失,物种组成和数量的变化导致沙化演替进程中高寒草甸草场质量逐渐降低.(2)相邻沙化演替阶段植物群落的物种组成相似性指数较高,而相距较远的沙化演替阶段植物群落的物种组成相似性指数较小,沙化演替系列两个极端阶段的植物群落的物种组成相似性指数最小.(3)垂穗披碱草在整个沙化演替过程中重要值和生态位宽度均逐渐减小,但其值都较大.(4)生态位总宽度占前5位的物种依次是:垂穗披碱草、莓叶委陵菜、矮嵩草、高山唐松草和苔草,其值分别为1.653、1.438、1.387、1.295和1.204.(5)种群之间生态位重叠系数的平均值随沙化程度加深呈单峰式曲线变化规律,轻度沙化阶段种群的生态位重叠程度较高,为0.824.     

The shift from plant–plant facilitation to competition under severe water deficit is spatially explicit

The stress‐gradient hypothesis predicts a higher frequency of facilitative interactions as resource limitation increases. Under severe resource limitation, it has been suggested that facilitation may revert to competition, and identifying the presence as well as determining the magnitude of this shift is important for predicting the effect of climate change on biodiversity and plant community dynamics. In this study, we perform a meta‐analysis to compare temporal differences of species diversity and productivity under a nurse plant (Retama sphaerocarpa) with varying annual rainfall quantity to test the effect of water limitation on facilitation. Furthermore, we assess spatial differences in the herbaceous community under nurse plants in situ during a year with below‐average rainfall. We found evidence that severe rainfall deficit reduced species diversity and plant productivity under nurse plants relative to open areas. Our results indicate that the switch from facilitation to competition in response to rainfall quantity is nonlinear. The magnitude of this switch depended on the aspect around the nurse plant. Hotter south aspects under nurse plants resulted in negative effects on beneficiary species, while the north aspect still showed facilitation. Combined, these results emphasize the importance of spatial heterogeneity under nurse plants for mediating species loss under reduced precipitation, as predicted by future climate change scenarios. However, the decreased water availability expected under climate change will likely reduce overall facilitation and limit the role of nurse plants as refugia, amplifying biodiversity loss.     

荒漠草原沙漠化植物群落及土壤物理变化

沙漠化是草地退化最严重的形式之一。以空间代替时间的方法,通过对宁夏中北部荒漠草原沙漠化过程中植物群落特征和土壤物理特性的研究,探讨草地植物群落与土壤物理特性对沙漠化的响应机制。结果表明:(1)潜在沙漠化阶段草地以牛枝子、猪毛蒿、中亚白草为优势种,轻度沙漠化阶段草地以中亚白草、苦豆子为优势种,中度沙漠化阶段草地以狗尾草、虫实为优势种,重度沙漠化阶段草地以沙米、赖草、狗尾草为优势种,极度沙漠化阶段草地以沙米为优势种。(2)随着沙漠化程度的加剧草地植物群落生物量、Shannon-Wiener指数、丰富度指数、盖度均呈降低趋势,但轻度沙漠化阶段草地植被生物量比潜在沙漠化增加了23%。(3)草地沙漠化导致土壤容重和土壤粗砂粒含量增加,而土壤水分,土壤细砂粒和粘粉粒含量降低。荒漠草原沙漠化导致了土壤环境和植被明显退化,草地生产力明显降低。     

Plant Species Redundancy and the Restoration of Faunal Habitat: Lessons from Plant‐Dwelling Bugs

Restoring disturbed lands is essential for conserving biodiversity. In floristically diverse regions, restoring all plant species following anthropogenic disturbance is financially costly and it is unknown if this can be achieved. However, re‐creating faunal habitat may not require reinstating all plant species if there is a high degree of redundancy. Here, we assess whether there is redundancy among a subset of native plant species chosen to restore fauna habitat following a severe disturbance. Additionally, we determine if reestablished plants support similar faunal assemblages as the same plant species in less disturbed forest. We sampled plant‐dwelling Hemiptera from 1,800 plants across 16 species. We found 190 species of Hemiptera, with most plant species in the forest having distinct hemipteran assemblages. Returning these plant species to areas undergoing restoration reinstated 145 hemipteran species, including the dominant species. Recalcitrant plant species (difficult to propagate and reestablish in restored areas) had different hemipteran assemblages from all other species. There was only one plant species that did not have a distinct assemblage and thus was considered redundant. We conclude that there is little redundancy in this study. For plant‐dwelling Hemiptera (with good powers of dispersal) to recolonize restored areas, restoration efforts will need to reinstate at least 13 of the 16 species of host plant of appropriate age and structure. Consequently, to meet the goal of restoring fauna habitat when there is no knowledge of which plant species are redundant, restoration projects should aim to reinstate all plant species present in less disturbed reference areas.     

Plant traits enabling survival in Mediterranean badlands in northeastern Spain suffering from soil erosion

Question: This study analysed the effect of severe soil erosion on species composition of plant communities by favouring species showing certain growth forms, root‐sprouting and clonal growth abilities. Location: The study area was located between the middle Ebro Valley and the Pre‐Pyrenees (northeastern Spain). Methods: Root‐sprouting and shoot‐rooting abilities, clonal reproduction and growth form were assessed for the 123 most common plant species from eroded lands in the study area. We obtained 260 vegetation relevés in three different substrata (gypsum outcrops, Miocene clays and Eocene marls) on areas with different degrees of soil erosion. The frequency of every plant trait in each relevé was estimated according to species presence. The effect of soil erosion on the frequency of plant attributes was assessed by correlation analyses. Results: Bipolar, non‐clonal plants and annual species decreased their frequency with increasing soil erosion in the three substrata analyzed, whereas root‐sprouters and woody plants (mostly sub‐shrubs) increased their frequency in most of the substrata analysed. Conclusions: Woody sub‐shrubs, root‐sprouters and clonal species are favoured in eroded lands in NE Spain. Bipolar species and annual plants might not be plastic enough to survive the high stress and frequent disturbances prevailing in such eroded areas.     

毛乌素沙地南缘沙漠化临界区域土壤养分的空间异质性

毛乌素沙地南缘沙漠化临界区域是沙地-草地景观界面的关键部位,研究该区域土壤养分的空间格局和生态学过程,对于土地沙漠化的机理研究具有重要的意义。采用经典统计与地统计学相结合的方法,通过半变异函数及其模型、克里格局部插值估计、空间分布图等研究了毛乌素沙地南缘沙漠化临界区域土壤养分的空间异质性特征。结果表明:研究区土壤速效钾含量符合球状模型,全氮和速效磷含量符合指数模型;速效钾含量具有强空间自相关性,其结构方差比为0.882,而全氮和速效磷含量表现为中等程度的空间自相关性,其结构方差比分别为0.501和0.514;3种土壤养分空间自相关距离存在差异,其中全氮和速效钾的变程均为511m,而速效磷的变程为143m;3种土壤养分的分布格局呈现明显的空间规律性,从牛枝子群落到黑沙蒿群落,速效钾和速效磷含量先降低后升高,与研究区的界面变化过程一致,而全氮含量逐渐降低,与研究区的植被覆盖度变化一致;3种土壤养分的标准差都较小,Kriging插值结果比较可靠。     

毛乌素沙地植被不同恢复阶段植物群落物种多样性、功能多样性和系统发育多样性

进入21世纪以来, 中国荒漠化恢复取得显著成效, 荒漠化、沙化土地面积持续减少, 植被覆盖度大幅提升, 但关于植被恢复过程中生物多样性如何变化的研究不足, 这制约着对荒漠化恢复成效的全面评估。本文基于群落调查和叶功能性状(叶片厚度、叶片干物质含量、比叶面积和叶片密度)的测定, 分析了毛乌素沙地不同恢复阶段(半固定沙地、固定沙地、结皮覆盖沙地和草本植物覆盖沙地)的植物群落物种多样性、功能多样性和系统发育多样性特征。结果表明: (1)多数叶功能性状的系统发育信号不显著, 表明环境因子对研究区植物功能性状的塑造作用很强。(2)对于α多样性, 结皮覆盖沙地的物种多样性(Shannon-Wiener多样性, H)、物种丰富度(S)、功能丰富度(FRic)及系统发育多样性(PD)指数均显著低于其他恢复阶段, 而其他3个阶段间无显著差异; 这些指数间均显著正相关, 表明物种多样性、功能多样性和系统发育多样性在植被恢复过程中协同变化。(3) β多样性指数随恢复阶段间隔增加而逐渐增大, 表明物种组成、功能属性及系统发育关系随植被恢复持续变化, 且半固定沙地到固定沙地的群落物种组成、功能属性及系统发育关系更替最快, 导致群落间差异最大。(4)固定沙地、结皮覆盖沙地和草本植物覆盖沙地群落系统发育结构均趋向于发散, 表明竞争排斥是群落构建的主要驱动力; 而半固定沙地群落系统发育结构无一致规律, 表明群落构建可能受到生境过滤和竞争排斥的综合作用。研究结果可为植被建设与管理提供参考, 为毛乌素沙地生态保育和生物多样性的保护提供科学依据。     

Structure and diversity of a species-rich grassland community, treated with additional illumination, fertilization and mowing

We examined the changes of species‐rich herbaceous community canopy structure and species diversity in a five‐year field experiment. Above‐ and below‐ground resource addition (fertilization and additional illumination with the help of mirrors) and cessation of annual mowing were applied as experimental treatments in 24 permanent plots of 40×40 cm. Canopy structure was studied by point quadrat sampling using laser beam to randomly position point quadrats at two different angles of observation – 60° and 120° from horizontal, north‐south direction. We hypothezised that the studied plant community is not light‐limited under the normal conditions (non‐fertilized and annually mown) but would become light‐limited after nutrient addition and/or cessation of mowing. In this case the effect of fertilization and cessation of mowing could be mitigated by introducing additional light resource (placing south‐facing mirrors).
Species richness in plots was not significantly altered by experimental treatments, most probably because of a strong input of species from surrounding areas by the means of lateral vegetative spread, compensating for the expected decrease of diversity with fertilization and cessation of mowing. Surprisingly, plant total coverage in a plot was the only variable significantly explaining plot richness, independent of experimental treatments and the year of observation. We therefore studied also species richness per unit coverage (standardized richness) which appeared to be significantly reduced by fertilization. Annual change of plant total coverage of a plot was good predictor of annual change of plot richness, except for the exceptionally dry period (1994–1995). There was no indication of light being limiting for the plants in control plots, but light obviously became limiting after nutrient addition – in fertilized plots additional illumination lead to a notably denser canopy. Generally, the average exposition of plant leaves surface was towards the north, independent of experimental treatments. However, in the exceptionally cloudy and cool year 1996 the situation was radically different – leaves were exposed predominantly towards the south, indicating that multi‐species canopy can plastically react to long‐term changes in light availability.     

塔克拉玛干沙漠南缘玉米对不同荒漠化环境的生理生态响应

为了研究玉米对不同荒漠化环境的适应性,以塔克拉玛干沙漠南缘策勒绿洲外围不同荒漠化程度下生长的玉米为试验材料,大田试验为手段,布置3个胁迫水平(轻度荒漠化、中度荒漠化、重度荒漠化),研究了玉米的土壤含水率、植株高度、生物量分配、脯氨酸(Proline)、丙二醛(MDA)、可溶性糖(Sugar)、叶绿素(Chl)、叶绿素荧光参数、比叶面积(SLA)等在不同胁迫梯度下的变化特征。结果显示:随着荒漠化程度的加剧,玉米生物量、脯氨酸、丙二醛、叶绿素、类胡萝卜素、Chl a/b、叶绿素荧光参数都有不同幅度的下降;中度荒漠化可溶性糖含量最低,重度最高,轻度介于两者之间;Car/Chl、比叶面积和地下生物量占总生物量的比重都随荒漠化程度的加剧,呈增加趋势。结果表明,荒漠化环境明显对玉米的生长产生了抑制作用;随着荒漠化程度的加剧,玉米植株的光合色素含量降低,PSⅡ受到影响,从而影响植株的光合作用,使玉米物质的积累受到影响;玉米自身通过在营养器官分配更多的能量和积累调控物质,并且在形态结构上也会发生某些改变以适应更恶劣的环境。随着胁迫程度的加剧,对其生长抑制愈严重。     

Spatiotemporal evolution of desertification based on integrated remote sensing indices in Duolun County,Inner Mongolia

Desertification causes not only a reduction of vegetation cover and surface moisture but also the expansion of sandy land. Considering that the modified soil adjusted vegetation index (MSAVI) is linearly related to canopy cover, albedo plays a significant role in the surface energy balance, and the sandy feature index (SFI) can identify sandy land. This paper proposed a desertification monitoring index (DMI) based on MSAVI, albedo and SFI to accurately monitor desertification. In addition, three classification methods (quantile grading, the susceptibility index segmentation method, and Jenks Natural Breaks) were used to divide the DMI into non-desertification, mild desertification, moderate desertification, and severe desertification. The relative exponential entropy model was adopted to select the optimal method for desertification classification. Spatiotemporal distributions of desertification in Duolun County were finally observed from 2005 to 2020. The results show that (1) although MSAVI, albedo and SFI have their own advantages in monitoring desertification, a single indicator is not suitable for various land uses. The DMI can combine the advantages of MSAVI, albedo and SFI in desertification monitoring and is more consistent with the real desertification levels. (2) Compared with quantile grading and susceptibility index segmentation methods, Jenks Natural Breaks has the smallest relative exponential entropy (2.124), with an overall classification accuracy of 88.21%, indicating that Jenks Natural Breaks is an optimal method for desertification monitoring. (3) Although approximately 1708.60 km² of desertification areas have improved from 2005 to 2020, accounting for 44.23% of the whole area, the remaining areas are still under fluctuating or degraded conditions. This shows that the local government has made some progress in desertification protection, but the areas under fluctuating or degraded conditions still require protection or management.     

Effectiveness of protein-rich pea flour for the control of stored-product beetles

Abstract The association between visiting ants and the extrafloral nectaries (EFN)‐bearing shrub Hibiscus pernambucensis Arruda (Malvaceae) was investigated in two different coastal habitats – a permanently dry sandy forest and a regularly inundated mangrove forest. In both habitats the frequency of plants with ants and the mean number of ants per plant were much higher on H. pernambucensis than on non‐nectariferous neighbouring plants. In the sandy forest the proportion of live termite baits attacked by ants on H. pernambucensis was much higher than on plants lacking EFNs. In the mangrove, however, ants attacked equal numbers of termites on either plant class. Ant attendance to tuna/honey baits revealed that overall ant activity in the sandy forest is higher than in the mangrove area. The vertical distribution (ground vs. foliage) of ant activity also differed between habitats. While in the mangrove foraging ants were more frequent at baits placed on foliage, in the sandy forest ant attendance was higher at ground baits. Plants housing ant colonies were more common in the mangrove than in the sandy forest. Frequent flooding in the mangrove may have resulted in increased numbers of ant nests on vegetation and scattered ant activity across plant foliage, irrespective of possession of EFNs. Thus plants with EFNs in the mangrove may not experience increased ant aggression towards potential herbivores relative to plants lacking EFNs. The study suggests that the vertical distribution of ant activity, as related to different nest site distribution (ground vs. foliage) through a spatial scale, can mediate ant foraging patterns on plant foliage and probably affect the ants’ potential for herbivore deterrence on an EFN‐bearing plant species.     

Changes in vegetation after 22 years' natural restoration in the Karst disturbed area in northwestern Guangxi, China

Variations of plant vegetation and spatial distribution were investigated in the areas of 4 types of typical disturbance, which had been under natural restoration for 22 years in the Karst area in northwestern Guangxi while the climax plant community was utilized as control. The slope scale and disturbance theory were used to study the plant diversity in the whole area and selected plots. It is clear that the disturbance had resulted in severe loss of plant species, and only 241 species of vascular plants that belong to 91 families and 206 genera survived in disturbed areas, accounting only for 26.6% of those in the natural reserve area. The consequent succession of 6 types of plant vegetation was sparse grass of rocky desertification, grass, shrub, liana-shrub, deciduous broad-leaved forest and mixed segment of evergreen and deciduous broad-leaved forest. The height, coverage, biomass and species diversity of plants decreased sharply with slope elevating, and the plant density appeared with normal distribution. Compared with the natural reserve area, all indices of plant vegetation in disturbed areas were much worse. Furthermore, different types of disturbance showed various affections on natural vegetative restoration, among which tilling after the whole slope was set on fire caused the worst impact and rocky desertification was the consequence, followed by depasturing after the whole slope was set on fire. Cutting was selective disturbance, and the vegetative restoration in the area with combination of cutting, grazing and setting on fire on the upper slope was relatively fast; however, it was even better in the area with combination of cutting and setting the upper slope on fire. In our studies, 4 strategies for vegetative recovery, using both natural and artificial approaches, were established, which were suitable for the Karst area in northwestern Guangxi.     

Dominant plant species shape soil bacterial community in semiarid sandy land of northern China

Plant species affect soil bacterial diversity and compositions. However, little is known about the role of dominant plant species in shaping the soil bacterial community during the restoration of sandy grasslands in Horqin Sandy Land, northern China. We established a mesocosm pots experiment to investigate short‐term responses of soil bacterial diversity and composition, and the related soil properties in degraded soils without vegetation (bare sand as the control, CK) to restoration with five plant species that dominate across restoration stages: Agriophyllum squarrosum (AS), Artemisia halodendron (AH), Setaria viridis (SV), Chenopodium acuminatum (CA), and Corispermum macrocarpum (CM). We used redundancy analysis (RDA) to analyze the association between soil bacterial composition and soil properties in different plant species. Our results indicated that soil bacterial diversity was significantly lower in vegetated soils independent of plant species than in the CK. Specifically, soil bacterial species richness and diversity were lower under the shrub AH and the herbaceous plants AS, SV, and CA, and soil bacterial abundance was lower under AH compared with the CK. A field investigation confirmed the same trends where soil bacteria diversity was lower under AS and AH than in bare sand. The high‐sequence annotation analysis showed that Proteobacteria, Actinobacteria, and Bacteroidetes were the most common phyla in sandy land irrespective of soil plant cover. The OTUs (operational taxonomic units) indicated that some bacterial species were specific to the host plants. Relative to bare sand (CK), soils with vegetative cover exhibited lower soil water content and temperature, and higher soil carbon and nitrogen contents. The RDA result indicated that, in addition to plant species, soil water and nitrogen contents were the most important factors shaping soil bacterial composition in semiarid sandy land. Our study from the pot and field investigations clearly demonstrated that planting dominant species in bare sand impacts bacterial diversity. In semiarid ecosystems, changes in the dominant plant species during vegetation restoration efforts can affect the soil bacterial diversity and composition through the direct effects of plants and the indirect effects of soil properties that are driven by plant species.     

Metabolic and physiological responses of Mediterranean high‐mountain and alpine plants to combined abiotic stresses

High‐mountain areas provide excellent opportunities to study the effects of combined abiotic stresses on plant physiology given their variety of steep ecological gradients, low anthropogenic disturbance and remarkable levels of taxonomic diversity. Efficient photoprotective and antioxidant scavenging mechanisms are vital for survival in high‐mountain plants, having its altitudinal and seasonal variations determined by environmental or ontogenetic factors such as the decrease in mean temperatures and water availability. A number of stress indicators have been described in order to rapidly assess plant fitness in high‐mountain environments. For instance, carbon isotope (δ¹³C) and proline content as drought and temperature stress indicators, because of their link to water‐use efficiency and osmotic adjustment; photosynthetic pigments, related to phenology, nutrient status, light and temperature stress; and non‐structural carbohydrate accumulation in response to mild or brief drought conditions. The present review unveils the wide research opportunities available for the study of adaptive responses in high‐mountain plants via stress indicators, and calls attention to the substantial knowledge gap existing between alpine zones and other mountainous regions, such as Mediterranean high‐mountains. The aim is to grant a more holistic understanding of the physiological mechanisms driving plant life in high altitudes and improve the predictions of the effects of changing environments in these species and across ecological scales.     

Contrasting effects of plant inter‐ and intraspecific variation on community trait responses to restoration of a sandy grassland ecosystem

Changes in plant community traits along an environmental gradient are caused by interspecific and intraspecific trait variation. However, little is known about the role of interspecific and intraspecific trait variation in plant community responses to the restoration of a sandy grassland ecosystem. We measured five functional traits of 34 species along a restoration gradient of sandy grassland (mobile dune, semi‐fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. We examined how community‐level traits varied with habitat changes and soil gradients using both abundance‐weighted and non‐weighted averages of trait values. We quantified the relative contribution of inter‐ and intraspecific trait variation in specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), and plant height to the community response to habitat changes in the restoration of sandy grassland. We found that five weighted community‐average traits varied significantly with habitat changes. Along the soil gradient in the restoration of sandy grassland, plant height, SLA, LDMC, and LCC increased, while LNC decreased. For all traits, there was a greater contribution of interspecific variation to community response in regard to habitat changes relative to that of intraspecific variation. The relative contribution of the interspecific variation effect of an abundance‐weighted trait was greater than that of a non‐weighted trait with regard to all traits except LDMC. A community‐level trait response to habitat changes was due largely to species turnover. Though the intraspecific shift plays a small role in community trait response to habitat changes, it has an effect on plant coexistence and the maintenance of herbaceous plants in sandy grassland habitats. The context dependency of positive and negative covariation between inter‐ and intraspecific variation further suggests that both effects of inter‐ and intraspecific variation on a community trait should be considered when understanding a plant community response to environmental changes in sandy grassland ecosystems.     

Effect of habitat area and isolation on plant trait distribution in European forests and grasslands

A number of studies show contrasting results in how plant species with specific life‐history strategies respond to fragmentation, but a general analysis on whether traits affect plant species occurrences in relation to habitat area and isolation has not been performed. We used published data from forests and grasslands in north‐central Europe to analyse if there are general patterns of sensitivity to isolation and dependency of area for species using three traits: life‐span, clonality, and seed weight. We show that a larger share of all forest species was affected by habitat isolation and area as compared to grassland species. Persistence‐related traits, life‐span and clonality, were associated to habitat area and the dispersal and recruitment related trait, seed weight, to isolation in both forest and grassland patches. Occurrence of clonal plant species decreased with habitat area, opposite to non‐clonal plant species, and long‐lived plant species decreased with grassland area. The directions of these responses partly challenge some earlier views, suggesting that further decrease in habitat area will lead to a change in plant species community composition, towards relatively fewer clonal and long‐lived plants with large seeds in small forest patches and fewer clonal plants with small seeds in small grassland patches. It is likely that this altered community has been reached in many fragmented European landscapes consisting of small and isolated natural and semi‐natural patches, where many non‐clonal and short‐lived species have already disappeared. Our study based on a large‐scale dataset reveals general and useful insights concerning area and isolation effects on plant species composition that can improve the outcome of conservation and restoration efforts of plant communities in rural landscapes.     

石漠化程度对苔藓植物多样性及其结皮土壤化学性质的影响

以研究区域不同石漠化等级为代表,分析苔藓多样性特征及其结皮土壤化学性质变化规律,探索其对石漠化进程的响应机制。结果显示:(1)苔藓物种多样性:含苔藓14科29属84种,其中苔类2科2属2种;(2)多样性指数表现为:重度石漠化阶段中度石漠化轻度石漠化极重度石漠化无石漠化;其均匀度为:中度石漠化阶段轻度石漠化重度石漠化极重度石漠化无石漠化;(3)随着石漠化程度加剧,苔藓群落组成中混合群落比重下降而纯群落比重上升;群落生活型则呈现交织型递减而丛集型递增的规律。(4)结皮土壤中全氮、全磷和微生物量碳随石漠化加剧均都呈递减趋势。(5)通过Partial RDA分析发现密枝青藓(Brachythecium amnicolum)、褶叶藓(Palamocladium nilgheriense)和美灰藓(Eurohypnum leptothallum)等可用于石漠化生态修复。石漠化程度对苔藓多样性影响不显著,但对其群落特征和生活型影响显著。因此可以结合苔藓群落和生活型特征监测石漠化,同时也可使用苔藓作为先锋植物引进用于石漠化早期修复。     

Commonness and rarity of alien and native plant species – the relative roles of intraspecific competition and plant–soil feedback

The success of invasive alien and common native species may be explained by the same underlying mechanisms. Differences in intraspecific competition as well as differences in plant–soil feedback have been put forward as potential determinants of plant success. We teased apart the relative roles of competition and plant–soil feedback in a greenhouse experiment with 30 common and rare alien and native species from nine plant families. We tested whether plant biomass decreased less for common than rare species, regardless of origin, when grown at higher relative frequencies (1, 3 or 6 out of 9 plants per pot) in a community and in soil previously conditioned by the same species at different frequencies (0, 1, 3 or 6 out of 9 plants per pot) in an orthogonal design for these two factors. Plant survival decreased slightly, but non‐significantly, for all species when grown in soil previously occupied by conspecifics. Among surviving plants, we found a decrease in biomass with increasing intraspecific competition across all species (regardless of origin or commonness), and alien species were more negatively affected by previous high plant frequency than native species, but only marginally significantly so. Our findings suggest that, while intraspecific competition limits individual biomass in a density‐dependent manner, these effects do not depend on species origin or commonness. Notably, alien species but not natives showed a decrease in performance when grown in soil pre‐conditioned with a higher frequency of conspecifics. In conclusion, soil‐borne pathogen accumulation might be weak in its effects on plant performance compared to intraspecific competition, with neither being clearly linked to species commonness.     

西南喀斯特高原盆地石漠化环境植物群落结构与物种多样性时空动态

为阐明西南典型喀斯特石漠化类型——喀斯特高原盆地石漠化植物群落结构和物种多样性特征及其演变规律,科学支撑喀斯特石漠化治理,选取了喀斯特高原盆地典型石漠化区贵州清镇簸箩小流域为研究区域,对其植被进行广泛的野外勘察,设置典型样方研究其植物群落结构和物种多样性特征;运用空间替代时间方法,研究石漠化演变过程中植物群落结构和物种多样性变化;基于2013—2015连续3 a的监测数据,研究其年际变化。结果表明:研究区群落结构简单,共记录到的植物分布58种,其中草本层18科24属28种、木本层17科25属30种;单种属的比例很高,为82.86%。不同等级石漠化环境植物群落高度、平均地径、平均冠幅、草本层生物量和灌木层生物量均具有显著差异;植物种群密度在不同等级石漠化环境变化依次为轻度石漠化中度石漠化潜在石漠化无石漠化。不同等级石漠化环境植物多样性指数、均匀度指数、丰富度指数和优势度指数均偏低,而且4种指数均与石漠化等级演替无明显耦合关系。不同年份植物群落高度、平均地径、种群密度和灌木层生物量随着时间的推移均呈增加趋势,但相邻年份增加不显著。研究区生态系统人为干扰逐渐减弱,植被呈现出正向演替的趋势,优势种的重要性趋于降低。该研究结果对我国西南喀斯特盆地生态功能恢复和石漠化植被重建具有一定的理论意义和实践指导价值。     

To hybridize or not to hybridize: what separates two genetic lineages of the Chalk‐hill Blue Polyommatus coridon (Lycaenidae,Lepidoptera) along their secondary contact zone throughout eastern Central Europe?

As a consequence of postglacial range expansion, hybrid zones evolved where different genetic lineages met. In this study, we analysed the Chalk‐hill Blue Polyommatus coridon all along the contact zone of two expansive lineages. This zone stretches from the sandy areas of north‐eastern Germany, along the mountain ranges of the German–Czech border and throughout the eastern Alps. We studied allozymes (19 loci) of 38 populations (1542 individuals) and compared these data sets against 15 populations of the western and 15 populations of the eastern lineages and found different degrees of hybridization. Thus, the calcareous regions of Thuringia and Sachsen‐Anhalt were mostly colonized by the western lineage. The middle mountain ranges between Bavaria and Bohemia represented a strong barrier blocking further expansion and thus completely impeding hybridization in this region. More intense hybridization was detected in the populations of the eastern Alps, especially in the north‐eastern part, where the Danube most probably acted as an expansion corridor for both lineages followed by intensive hybridization. In the south‐eastern Alps, hybrid populations were mostly detected in the easternmost parts and along the larger river valley of Drava and Mur; pure western populations dominated in the other areas of this region. These results show that the degree of hybridization along a contact zone is correlated with the ecological demands of a species and the regional physical geographic circumstances. This finding was proved for the Chalk‐hill Blue in our study but is also the most likely scenario in most animal and plant species.