采石场废弃地的生态重建研究进展

采石场的开采严重破坏了植被和土壤,形成了大量的裸露岩石斜坡,造成宏观景观支离破碎和极端的环境条件,限制了植物的生长。由于自然恢复所需时间长久,人工恢复被广泛应用于采石场废弃地的生态重建。自然演替过程是采石场生态重建的理论基础,自然演替理论可以为人工恢复措施提供指导。植物群落演替的早期阶段,非生物因素起主要作用,随着演替的推移,生物因素的重要性增强。邻近自然植被的土壤和繁殖体通过外力的扩散,对恢复起重要作用。除了非生物和其他的限制,先到达恢复地的物种竞争能力的变化能决定了演替过程。演替过程中的干扰因素往往成为演替重要的驱动力。裸露岩石斜坡的物理稳定性对植被恢复有重要影响,有机废物的使用和施肥可以影响恢复演替的方向和生物多样性。播种一定的植物能够改变恢复演替方向,加速演替过程。乡土物种适应了当地气候,能够促进演替。随着修复时间的延长,土壤有机质含量,植被覆盖度和物种丰富度不断增加,土壤微生物生物量随之增加。开展不同地区采石场植物种类的选育、研究乡土物种的功能特性、土壤微生物群落和酶的变化、植被演替过程的定位研究、植物种间的竞争关系、自然演替和人工恢复的比较研究、探索经济高效的采石场生态重建方法是未来的研究方向。     

演替理论与植被恢复

《昆明-蒙特利尔全球生物多样性框架》提出要高质量保护和恢复各30%的土地,最大化地实现保护生物多样性和缓解气候变化的目标,而演替理论和植被恢复可以为实现30%的保护和恢复目标服务。演替理论是植被生态学中的核心理论,演替是指在一个地点上由一群不同物种组成的生命体的结构或组成随时间而变化的过程; 植被恢复是以植物种植、配置为主,恢复或重建植物群落或天然更新恢复植物群落的过程,植被恢复是生态系统结构和功能从简单到复杂、从低级向高级变化的过程,最终目的是建立健康稳定的植物群落。演替是植被恢复的基础,植被恢复被视为对演替过程的操纵,以达到恢复受损植被生态系统的目标。演替理论可以指导植被恢复,而植被恢复对演替理论的发展有益。演替按裸地性质可以分为原生演替和次生演替,有研究建议将恢复过程视为第三演替,这将有助于理解通过人为干预促进植被恢复成功的管理选择,特别是通过强调退化生态系统中的环境和生物遗存的管理选择。此外,该文还提出了植被恢复理论和演替理论未来可能重点关注的科学和技术问题。     

植物养分捕获策略随成土年龄的变化及生态学意义

自然成土过程中土壤养分的变化与植被原生演替常同时发生。随成土年龄变化的植物养分捕获策略(NASs)对植物竞争能力和演替过程具有重要影响。该文将植物NASs划分为细根、微生物、特殊根系、食虫和寄生策略等5个类型; 发现植物NASs的多样性随成土年龄的增加呈哑铃型变化模式; 特殊根系策略对植物捕获养分的作用在成土中期最小、后期最大, 细根和微生物策略的作用随成土年龄的增加逐渐降低; 分析了成土过程中NASs对植物种间关系影响的变化, 发现NASs对成土早期植物的促进作用和中期的竞争关系具有重要影响, 而成土后期多样和互补的NASs对植被群落的稳定共存及多样性的形成具有影响; 提出应进一步探究成土过程中土壤养分与植物NASs变化之间的定量关系, 开展更多研究以阐明NASs对植被原生演替、物种多样性形成和成土过程的贡献与机理。     

火山喷发后植被演替的影响因子

火山喷发后的植被演替是一个复杂的动态过程,受到多种因子的共同制约。揭示这一过程及其影响因子对研究火山干扰下的植被演替规律、预测未来植被演替动态具有重要的指导意义。本文综述了该领域的主要研究工作,分析了影响火山喷发后植被演替的主要因子,并对其研究方法进行总结和展望。影响火山喷发后植被演替的因子主要包括生物因子和非生物因子。生物因子包括残遗种和种子传播,它们为火山喷发后的植被演替提供繁殖体和种源。非生物因子包括火山喷发事件、火山基质、土壤因子和气候因子,它们是重要的外部因子。火山喷发事件分别从火山干扰尺度、严重度和频度3个方面制约植被演替;火山基质类型及其异质性程度决定了植被演替的轨迹,对植被演替动态起主导作用;火山喷发导致土壤和气候环境恶劣,在火山喷发后的早期演替阶段,植被演替速率低,随着土壤和气候环境得到改善,植被演替速率逐渐加快。此外,将模型与"3S"技术相结合在大尺度上研究火山喷发后的植被演替是一个新的研究视角。     

群落生态学中的植物-土壤反馈研究

植物-土壤反馈是指植物改变了其生长环境中土壤的生物和非生物属性,改变后的土壤进而影响植物适合度的过程。植物-土壤反馈的一个根本前提是:植物在根际周围产生由专化病原菌和共生菌构成的特异性微生物群落,专化微生物对宿主植物种群有很大的影响,对非宿主植物没有或者有微弱影响。自从20世纪90年代被明确提出后,植物-土壤反馈被广泛用于揭示不同尺度的生态学过程,诸如演替、竞争、生物入侵、全球变化对生态系统的影响等。近年来,植物-土壤反馈与群落生态学主要研究领域之间的整合取得了实质性进展。该文主要关注的是土壤微生物介导的植物-土壤反馈及其对植物物种共存、群落结构和生态系统功能的影响。土壤微生物不仅可以产生稳定化力量促进物种共存,也可以改变均一化力量或者种间适合度差异,从而影响植物种间共存。在群落生态学中通常假设稀有种受土壤负反馈的影响更弱,从而预测植物局域丰富度与土壤反馈强度具有负相关关系。然而实验证据却揭示了不同的模式,加强对植物与土壤病原菌之间的进化动态的关注是调和这些不一致模式的关键。土壤微生物也是驱动植物群落演替的关键因子。土壤微生物通过稀释效应影响植物多样性-群落生产力关系。专化土壤病原菌或...     

土壤有益细菌在植物根际竞争定殖的影响因素

在土壤有益微生物应用于生物肥料、生物杀虫剂、植物生长刺激剂和生物处理剂的过程中,根际定殖具有重要作用。细菌在植物根际定殖是一个比较复杂的过程,影响定殖能力的因素也是复杂多样的。本文综述了参与根部竞争定殖的生物因素,包括受细菌遗传控制的某些特性如鞭毛/运动性、趋化性、多糖、位点特异重组酶/菌落阶段变异、NADH脱氢酶,植物根的分泌物和植物种类等;影响微生物根际定殖的非生物因素如土壤类型、土壤特性和土壤温度等,探讨了影响微生物根际定殖的主要研究方向。     

长江口九段沙植物群落研究

长江口九段沙属于发育早期的河口沙洲,植被完全保持着自然演替的早期状况。对九段沙湿地高等植物群落的结构特点及演替特征进行研究。研究结果表明：九段沙湿地植被分布几乎覆盖整个沙岛,生物量丰富。高等植物中多克隆植物,植物群落结构简单,生物多样性低,植被具原生性,群落演替的早期原生特征明显,演替过程在没有引种互花米草之前人为干扰少,互花米草的引种加速了九段沙湿地植被的陆地化演替进程。最后提出保护和开发利用九段沙植被的适应原则。     

铜陵市狮子山铜尾矿废弃地生态恢复过程中植被演替规律

通过对铜陵市狮子山铜尾矿废弃地植被的实地调查,探讨了该废弃地的植被状况及其植被恢复过程中的植物群落形成与演替的一般规律与特征.结果表明:目前废弃地入侵、定居植物共49种,隶属于15科38属,主要包括菊科(12种)、禾本科(11种)、豆科(8种)等.极端贫瘠和过高的重金属含量(特别是Cu、Cd,平均超出对照土样的20～30倍)是限制植物在废弃地定居的主要因素.全部植物中,一、二年生草本植物26种,多年生草本植物20种.风播种子和果实是废弃地植物繁殖体的主要来源.尾矿废弃地植物群落形成具有先锋植物的入侵、定居、群聚和竞争等过程,共形成了14种相对稳定的小群落,包括单优势种群落、次优势种群落和共优势种群落三种类型.伴随着尾矿废弃地植物群落的形成与演替,群落中物种丰富度增大,多样性指数呈增加趋势,而群落内植物种综合优势比间的差值趋于减小.     

铜陵市狮子山铜尾矿废弃地生态恢复过程中植被演替规律

通过对铜陵市狮子山铜尾矿废弃地植被的实地调查,探讨了该废弃地的植被状况及其植被恢复过程中的植物群落形成与演替的一般规律与特征。结果表明目前废弃地入侵、定居植物共49种,隶属于15科38属,主要包括菊科(12种)、禾本科(11种)、豆科(8种)等。极端贫瘠和过高的重金属含量(特别是Cu、Cd,平均超出对照土样的20~30倍)是限制植物在废弃地定居的主要因素。全部植物中,一、二年生草本植物26种,多年生草本植物20种。风播种子和果实是废弃地植物繁殖体的主要来源。尾矿废弃地植物群落形成具有先锋植物的入侵、定居、群聚和竞争等过程,共形成了14种相对稳定的小群落,包括单优势种群落、次优势种群落和共优势种群落三种类型。伴随着尾矿废弃地植物群落的形成与演替,群落中物种丰富度增大,多样性指数呈增加趋势,而群落内植物种综合优势比间的差值趋于减小。     

樟村坪磷矿废弃地植物群落的形成与演替

通过分析湖北省宜昌县樟村坪磷矿废弃地植被的组成、空间结构、各成分综合优势比其群集度的变化以及植物分布与环境因子的相关性等问题,探讨了该地植被恢复过程中植物群落形成与演替的一般规律。结果表明,废弃地6种演替植物群落的形成是先锋植物种类入侵、定居、群聚和竞争的结果,在植物群落形成与演替的过程中,各种类成分的种群数量及综合优势比呈动态变化,废弃地植物群落形成与演替的过程按演替序列可分为3个阶段。植物群落形成与演替还与环境因子有关,废弃地高浓度的土壤效磷是影响植物生长与分布的胁迫因子。伴随着群落的形成与演替,植物群落的物种多样性呈逐渐增加的趋势。     

Dispersal and establishment both limit colonization during primary succession on a glacier foreland

Plant colonization can be limited by lack of seeds or by factors that reduce establishment. The role of seed limitation in community assembly is being increasingly recognized, but in early primary succession, establishment failure is still considered more important. We studied the factors limiting colonization on the foreland of Coleman Glacier, Washington, USA, to determine the importance of seed and establishment limitation during primary succession. We also evaluated the effects of seed predation, drought, and existing vegetation on establishment. We planted seeds of seven species into plots of four different ages and found evidence that both seed and establishment limitation are strong in early succession. We also found that seed and establishment limitation both remained high in later stages of succession. Seed predation reduced establishment for most species and some evidence suggested that drought and existing vegetation also limit establishment. Because both dispersal and establishment failure restrict colonization in recently exposed habitat, late-seral forest species may have a difficult time migrating upward in response to global climate change. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The viability of seeds of rainforest species after experimental soil burials under tropical wet lowland forest in north-eastern Australia

Seed samples of 50 rainforest species representative of all successional stages from tropical lowland forests in north-eastern Australia were buried in nylon material bags under rainforest for periods up to 2 years. The seed samples were exhumed after 6 weeks, 6 months, 1 year and 2 years, and their viabilities assessed. Substantial portions of the samples of 31 species of pioneer and early and late secondary species retained viability for 2 years in the buried samples, and germinated immediately they were exposed to greenhouse conditions. In approximately one-third of these species, the dormancy was completely enforced by the burial conditions since fresh, mature seed germinated immediately in the greenhouse. The remainder of the long-lived seeds showed some evidence of variable initial periods of innate dormancy produced by their hard, impermeable coats. There was no indication that the burial conditions enforced or induced any dormancy in the seeds of primary forest trees. The mean viability of the primary forest seeds examined was 10% after 6 months burial. The soft-coated seeds were obligate immediate germinators; they germinated or died. The remainder showed variably delayed germination, and this was interpreted as a mechanical dormancy produced by their leathery, fibrous, or stony endocarps. The group of late secondary species sampled contained both obligate immediate germinators and seeds with well developed dormancy mechanisms. Many of the buried 'seedlings’ of primary forest species remained alive for a year or more attached to seeds, demonstrating the ability of the larger primary seeds to sustain seedlings under conditions adverse to photosynthesis and growth. Some seedlings of Castanospermum australe were alive and were transplanted successfully after 2 years burial. This enables primary forest species to stock seedlings on the forest floor in contrast to the secondary species which store seed in the soil.     

Could poor seed dispersal contribute to predation by introduced rodents in a Hawaiian dry forest?

Dry forests are among the most diverse, yet threatened, communities in Hawai’i. Dry forests throughout the archipelago suffer from a lack of natural regeneration of trees. Two factors that may limit tree recruitment include poor seed dispersal and seed predation by rodents. Poor or limited dispersal of fleshy-fruited species results in seeds and fruits falling directly under parents. Dispersed and non-dispersed seeds may differ in their vulnerability to predation. We tested effects of seed location (under/away from parent trees) and pulp (presence/absence) on predation of four native species that suffer from limited dispersal and one readily-dispersed alien species in Kanaio Natural Area Reserve, Maui. Three natives (Diospyros sandwicensis, Pleomele auwahiensis, Santalum ellipticum), had significantly more seeds removed under parent trees than in exposed sites away from trees. For the one alien (Bocconia frutescens) and two native trees (D. sandwicensis, P. auwahiensis) that were evaluated, significantly more intact fruits were removed than were cleaned seeds. Presence of teeth marks and gnawed seed husk fragments indicate introduced rodents are destroying many of the seeds they remove. These results suggest that seed predation is disproportionately concentrated among poorly-dispersed seeds and may contribute to recruitment failure.     

麦蚜和寄生蜂对农业景观格局的响应及其关键景观因子分析

大量研究表明多样性的农业景观格局能够影响蚜虫及寄生蜂的分布。本文利用并设计了两种尺度的麦田农业景观格局,依据麦蚜种群发生特点,分为迁入期、增长期与高峰期三个时期,论述了不同尺度下农业景观元素对麦蚜及寄生蜂系统的影响,通过逐步回归筛选了不同时期麦蚜及寄生蜂分布的关键景观元素,最后通过CANOCO软件模拟了麦蚜及寄生蜂的分布排序格局。结果表明不同景观因子对麦蚜及寄生蜂种群影响不同,迁入期两种尺度下裸地最有利于两种有翅蚜的迁飞入田,塑料大棚对有翅蚜种群的入田有抑制作用。增长期草地与林地生境对麦蚜种群增长率促进最大,塑料大棚同样抑制了麦蚜的种群增长率;但塑料大棚、草地与林地对蚜茧蜂的种群增长率有促进作用,非麦类作物生境对蚜茧蜂种群增长率抑制作用最大;草地与林地有利于重寄生蜂的种群增长率;高峰期裸地比例大的农业景观下麦蚜的最大种群密度较大,草地与林地对蚜茧蜂与重寄生蜂的最大种群密度均有促进作用。两种尺度下的研究结果一致。不同麦物种的对不同景观元素反应与形态学与生活史特征有关,而且景观结构中特定的植物种类、非作物植物的密度与物候期都可能影响寄生蜂群落的多样性与功能。     

Human-Mediated Dispersal of Seeds by the Airflow of Vehicles

Human-mediated dispersal is known as an important driver of long-distance dispersal for plants but underlying mechanisms have rarely been assessed. Road corridors function as routes of secondary dispersal for many plant species but the extent to which vehicles support this process remains unclear. In this paper we quantify dispersal distances and seed deposition of plant species moved over the ground by the slipstream of passing cars. We exposed marked seeds of four species on a section of road and drove a car along the road at a speed of 48 km/h. By tracking seeds we quantified movement parallel as well as lateral to the road, resulting dispersal kernels, and the effect of repeated vehicle passes. Median distances travelled by seeds along the road were about eight meters for species with wind dispersal morphologies and one meter for species without such adaptations. Airflow created by the car lifted seeds and resulted in longitudinal dispersal. Single seeds reached our maximum measuring distance of 45 m and for some species exceeded distances under primary dispersal. Mathematical models were fit to dispersal kernels. The incremental effect of passing vehicles on longitudinal dispersal decreased with increasing number of passes as seeds accumulated at road verges. We conclude that dispersal by vehicle airflow facilitates seed movement along roads and accumulation of seeds in roadside habitats. Dispersal by vehicle airflow can aid the spread of plant species and thus has wide implications for roadside ecology, invasion biology and nature conservation.     

Different responses of avian feeding guilds to spatial and environmental factors across an elevation gradient in the central Himalaya

Although elevational patterns of species richness have been well documented, how the drivers of richness gradients vary across ecological guilds has rarely been reported. Here, we examined the effects of spatial factors (area and mid‐domain effect; MDE) and environmental factors, including metrics of climate, productivity, and plant species richness on the richness of breeding birds across different ecological guilds defined by diet and foraging strategy. We surveyed 12 elevation bands at intervals of 300 m between 1,800 and 5,400 m a.s.l using line‐transect methods throughout the wet season in the central Himalaya, China. Multiple regression models and hierarchical partitioning were used to assess the relative importance of spatial and environmental factors on overall bird richness and guild richness (i.e., the richness of species within each guild). Our results showed that richness for all birds and most guilds displayed hump‐shaped elevational trends, which peaked at an elevation of 3,300–3,600 m, although richness of ground‐feeding birds peaked at a higher elevation band (4,200–4,500 m). The Normalized Difference Vegetation Index (NDVI)—an index of primary productivity—and habitat heterogeneity were important factors in explaining overall bird richness as well as that of insectivores and omnivores, with geometric constraints (i.e., the MDE) of secondary importance. Granivore richness was not related to primary production but rather to open habitats (granivores were negatively influenced by habitat heterogeneity), where seeds might be abundant. Our findings provide direct evidence that the richness–environment relationship is often guild‐specific. Taken together, our study highlights the importance of considering how the effects of environmental and spatial factors on patterns of species richness may differ across ecological guilds, potentially leading to a deeper understanding of elevational diversity gradients and their implications for biodiversity conservation.     

Principles of Natural Regeneration of Tropical Dry Forests for Restoration

Tropical dry forests are the most threatened tropical terrestrial ecosystem. However, few studies have been conducted on the natural regeneration necessary to restore these forests. We reviewed the ecology of regeneration of tropical dry forests as a tool to restore disturbed lands. Dry forests are characterized by a relatively high number of tree species with small, dry, wind‐dispersed seeds. Over small scales, wind‐dispersed seeds are better able to colonize degraded areas than vertebrate‐dispersed plants. Small seeds and those with low water content are less susceptible to desiccation, which is a major barrier for establishment in open areas. Seeds are available in the soil in the early rainy season to maximize the time to grow. However, highly variable precipitation and frequent dry spells are important sources of mortality in seeds and seedlings. Collecting seeds at the end of the dry season and planting them when soil has sufficient moisture may increase seedling establishment and reduce the time they are exposed to seed predators. Germination and early establishment in the field are favored in shaded sites, which have milder environment and moister soil than open sites during low rainfall periods. Growth of established seedlings, however, is favored in open areas. Therefore, clipping plants around established seedlings may be a good management option to improve growth and survival. Although dry forests have species either resistant to fire or that benefit from it, frequent fires simplify community species composition. Resprouting ability is a noticeable mechanism of regeneration in dry forests and must be considered for restoration. The approach to dry‐forest restoration should be tailored to this ecosystem instead of merely following approaches developed for moister forests.     

A season- and gap-detection mechanism regulates seed germination of two temperate forest pioneers

The survival of seedlings in temperate climate habitats depends on both temporal and spatial factors. The interaction between an internal seed dormancy mechanism and the ruling environmental conditions allows accurate cueing of germination. We analysed how environmental signals interact in seeds of temperate forest pioneer species, increasing the seed's chances of germinating in the right place at the right time. Digitalis purpurea and Scrophularia nodosa are two small-seeded herbaceous species that typically grow in vegetation gaps in European temperate forests. Seeds of both species are partially dormant at the time of dispersal in summer. This primary dormancy is released in autumn and early winter, resulting in a minimal level of physiological dormancy by late winter and early spring. We observed that physiological dormancy was induced again in seeds exhumed in late spring and in summer. Experiments in laboratory conditions revealed that primary dormancy in seeds of S nodosa was broken by cold stratification, whereas primary dormancy in D. purpurea seeds was broken by both a cold and a warm stratification. The two species differed in their response to the tested gap-detection signals, as light was the most important factor stimulating germination of D. purpurea, and seeds of S. nodosa germinated best when subjected to daily fluctuating temperatures. This study clearly indicates that the ability to germinate in response to gap-detection signals changes seasonally in temperate forest pioneers. Additionally, seeds of both species responded differently to these environmental signals, probably reflecting differences in the regeneration niche.     

A combined physical and physiological dormancy controls seasonal seedling emergence of Geranium robertianum

Temperate forest herbs with seeds exhibiting both a physical and a physiological dormancy mechanism are rare, and knowledge on the factors regulating germination of these species is fragmentary. The biennial Geranium robertianum L. grows mainly in temperate woodlands, but can also be found in exposed habitats. Seedlings of G. robertianum are known to emerge from spring until autumn, but little is known about the environmental factors regulating germination. In this study, phenology of seedling emergence and of physical dormancy loss was examined for seeds buried at shaded or sunny exposed locations. The role of temperature in regulating dormancy and germination was analysed by incubating seeds in temperature sequences simulating temperatures that seeds experience in nature. The results indicate that most seeds of G. robertianum buried in sunny conditions germinate immediately after physical dormancy loss in summer. Seeds buried in shaded conditions also lose physical dormancy mainly during summer, but remain physiologically dormant and do not germinate until late winter or early spring. Besides physical dormancy, seeds of G. robertianum also initially have a high level of physiological dormancy, which is reduced during dry storage. Physiological dormancy is reduced through chilling in winter, thus enabling the seeds to germinate at low temperatures. We conclude that a complex combination of physical and physiological dormancy ensures that G. robertianum seeds germinate in summer at exposed sites and in early spring at shaded sites.     

Supplementing Seed Banks to Rehabilitate Disturbed Mojave Desert Shrublands: Where Do All the Seeds Go?

Revegetation of degraded arid lands often involves supplementing impoverished seed banks and improving the seedbed, yet these approaches frequently fail. To understand these failures, we tracked the fates of seeds for six shrub species that were broadcast across two contrasting surface disturbances common to the Mojave Desert—sites compacted by concentrated vehicle use and trenched sites where topsoil and subsurface soils were mixed. We evaluated seedbed treatments that enhance soil‐seed contact (tackifier) and create surface roughness while reducing soil bulk density (harrowing). We also explored whether seed harvesting by granivores and seedling suppression by non‐native annuals influence the success of broadcast seeding in revegetating degraded shrublands. Ten weeks after treatments, seeds readily moved off of experimental plots in untreated compacted sites, but seed movements were reduced 32% by tackifier and 55% through harrowing. Harrowing promoted seedling emergence in compacted sites, particularly for the early‐colonizing species Encelia farinosa, but tackifier was largely ineffective. The inherent surface roughness of trenched sites retained three times the number of seeds than compacted sites, but soil mixing during trench development likely altered the suitability of the seedbed thus resulting in poor seedling emergence. Non‐native annuals had little influence on seed fates during our study. In contrast, the prevalence of harvester ants increased seed removal on compacted sites, whereas rodent activity influenced removal on trenched sites. Future success of broadcast seeding in arid lands depends on evaluating disturbance characteristics prior to seeding and selecting appropriate species and seasons for application.