Implications from the Buell‐Small Succession Study for vegetation restoration

Abstract. Succession is relevant to restoration because managers have to prevent, enhance or replace natural vegetation dynamics. Features of a permanent plot study of post‐agricultural succession in central New Jersey, USA, illustrate important implications of vegetation dynamics for restoration. In the past, such implications had to be drawn from chronosequences and coarse resolution studies, neither of which exposes the local contingencies relevant to site specific restoration. However, the fine scale and continuous nature of the current study reveal that succession is highly contingent on historical and local spatial heterogeneity. For example, the absence of one generally expected dominant stage, the demise of shrubs without replacement by later successional tree species, and the long and multimodal persistence of individual species suggest that neither the relay floristic or initial floristic models of succession is adequate to guide restoration. At the local scale, volleys of species appear through the succession, and reflect spatial contingencies such as neighboring vegetation and edge relationships, and patchy behavior of different functional groups. The role of introduced species and of plant consumers are additional sources of local contingency. These local and time‐specific behaviors in the vegetation are the patterns that restorationists must understand either to choose appropriate reference states, to prevent unexpected local dynamics, or to design interventions that are appropriate to the specific site of interests.     

Alternative fire‐driven vegetation states

There is increasing evidence that alternative stable vegetation types exist for a given climate that are maintained by distinct fire regimes. Paritsis et al. (2014, this issue) provide an example in a temperate ecosystem. Here I briefly review cases of bi‐stability in various climates, and present a simple model for the transition between states in their system.     

Microscale vegetation-soil feedback boosts hysteresis in a regional vegetation–climate system

It has been hypothesized that a positive feedback between vegetation cover and monsoon circulation may lead to the existence of two alternative stable states in the Sahara region: a vegetated state with moderate precipitation and a desert state with low precipitation. This could explain the sudden onset of desertification in the region about 5000 years ago. However, other models suggest that the effect of vegetation on the precipitation may be insufficient to produce this behavior. Here, we show that inclusion of the microscale feedback between soil and vegetation in the model greatly amplifies the nonlinearity, causing alternative stable states and considerable hysteresis even if the effect of vegetation on precipitation is moderate. On the other hand, our analysis suggests that self‐organized vegetation patterns known from models that only focus at the microscale plant–soil feedback will be limited to a narrower range of conditions due to the regional scale climate‐feedback. This implies that in monsoon areas such as the Western Sahara self‐organized vegetation patterns are predicted to be less common than in areas without monsoon circulation such as Central Australia.     

Plant species associations in alpine-subnival vegetation patches in the Central Caucasus

Abstract. Patches of herbaceous vegetation found at the boundary of the alpine and subnival belts in the Central Caucasus (3000 m) were analysed for species composition, interspecific associations, as well as for relations between age, size and diversity of the patches. 34 plant species were recorded. Positive and negative associations were found among the most frequent species. A model is presented that describes the cumulation of species in patches during succession. In the final and stable successional stage, the maximum number of species within a patch was nine. Species composition varies in patches of different age, typical alpine species being more frequent in older ones. The results are interpreted as evidence for niche differentiation and selection of species composition through the 'sieve’ of interspecific relations, taking place during succession in the studied patches.     

Theoretical vegetation science on the way

Some historical notes are presented on the start and early development of the Working-Group for Data-Processing, now Working-Group for Theoretical Vegetation Science, of the International Association for Vegetation Science. One of the major outcomes of the first period of activities in the Working-Group has been the creation of a phytosociological coding and retrieval system to be used in combination with multivariate methods. One branch of classical phytosociology which could have profited much from the Working-Group's achievements, i.e. syntaxonomy, never developed fully into a numerical syntaxonomy and, in fact, it did not develop much at all over the last 20 yr.The next phase in the development of the Working Group is characterized by a strong emphasis on vegetation dynamics. First, these dynamical studies concentrated on real sequences of data from permanent plots, which were treated with the numerical methods available. Later, dynamical models started to be developed in order to predict succession and other forms of long-term vegetation dynamics, for which real data are not available.The third phase, which has been entered only recently, is characterized by an overall emphasis on vegetation theory, from which both the most appropriate choice of numerical methods in any particular case, and dynamical phenomena can be approached. Moreover, vegetation theory is of fundamental importance for the development of the plant community concept and of vegetation typology.In addition, some remarks are made on the growing need for vegetation ecology to cooperate with experimental ecophysiology and population ecology.     

A Markov approach for describing post-fire succession of vegetation

Vegetation dynamics in the coastal area of the Seto Inland Sea region in Japan, where wild fires occur frequently, were described using a stationary Markov model. In this region, vegetation types ofMiscanthus-Pleioblastus grassland,Lespedeza-Mallotus scrub,Pinus-Rhododendron forest andCrassocephalum-Erechtites community have been identified, and these show cyclic succession under the influence of fires. The model uses parameters determining fire frequency and rate of successional change to analyze the effect of variation in these parameters on the areal ratio of each vegetation type at equilibrium and on the time taken for one vegetation type to succeed another (elapsed successional time). The effect of fire frequency differs between hypothetical habitats with high and low productivity. A policy for vegetation management in areas of high and low productivity is proposed. The advantages and limitations of applying Markov models to studies of vegetation succession are also discussed.     

Invasion models of vegetation dynamics

Since communities change as a result of their successful invasion by new species it seems logical to attempt to predict future vegetation change by focussing on the invasion process. Several such invasion models are reviewed, and one particular model, based on dynamic game theory is developed further. This model can be used as an alternative to linear (e.g. Markov chain) models for the prediction of vegetation dynamics, and also to compare invasive abilities of species and resistance to invasion of communities. The main advantage of the model lies in the fact that it operates at a sufficiently high level of integration to allow for model calibration (in spite of the large number of underlying processes), and yet has an obvious population biological interpretation (in terms of the success of invading populations). The model can be calibrated using either time course data or experimental data, and it may be helpful in understanding what determines the fate of an invading population. It is used here to analyze two published vegetation dynamics data sets.This work was financially supported by operating grant A8115 from the Natural Sciences and Engineering Research Council of Canada.     

The vegetation of roadside verges with respect to environmental gradients in southern New Zealand

Abstract. A survey of the vegetation of roadside verges was made across the southern part of the South Island of New Zealand. Samples were taken at 10-km intervals along selected roads providing a climatic range from the suboceanic conditions of the east coast into semi-arid Central Otago, and from Central Otago through the Southern Alps to the hyper-oceanic areas of high rainfall on the west Coast. The variation in the floristic composition is associated mainly with variation in rainfall, continentality, altitude, soil acidity, soil organic matter, and presence of forest. Sites in the arable and pastoral regions on the eastern side of the Southern Alps support a herbaceous vegetation consisting mostly of exotic species of European origin, with a few native grasses scattered through the drier and less fertile sites. A greater proportion of native species is found at higher altitudes. Roadside vegetation in the area of high rainfall to the west is characterized by indigenous ferns and woody species, although vegetation adjacent to cleared areas is more similar to that on roadsides adjacent to farmland on the east coast. The pattern of distribution of both native and exotic species is strongly related to altitudinal and climatic gradients, and the environmental responses of the exotic species are similar to those recorded in Europe. This suggests a colonization of all available sites by the exotic species, despite the relatively short time since their introduction to New Zealand, rather than an incomplete invasion.     

Long-term vegetation dynamics mediated by herbivores,weather and fire in a Juniperus-Quercus savanna

Abstract. Long-term (45-yr) basal area dynamics of dominant graminoid species were analyzed across three grazing intensity treatments (heavily grazed, moderately grazed and ungrazed) at the Texas A&M University Agricultural Research Station on the Edwards Plateau, Texas. Grazing intensity was identified as the primary influence on long-term variations in species composition. Periodic weather events, including a severe drought (1951–1956), had little direct influence on composition dynamics. However, the drought interacted with grazing intensity in the heavily grazed treatment to exacerbate directional changes caused by grazing intensity. Species response to grazing was individualistic and noisy. Three response groups were identified. Taller, more productive mid-grasses were most abundant under moderate or no grazing. Short grasses were most abundant under heavy grazing. Intermediate species were most abundant under moderate grazing and opportunistic to weather patterns. Graminoid diversity increased with the removal or reduction of grazing intensity. The moderately and ungrazed treatments appeared most resistant to short-term weather fluctuations, while the heavily grazed treatment demonstrated significant resilience when grazing intensity was reduced after over 110 yr of overgrazing. Identification of a ‘climax’ state is difficult. Significant directional change, which took nearly 20 yr, appears to continue in the ungrazed treatment after 45 yr of succession. The observed, relatively linear patterns of perennial grass composition within the herbaceous patches of this savanna were generally explained by traditional Clementsian succession. However, when dynamics of the herbaceous community are combined with the woody component of this savanna, the frequency and intensity of fire becomes more important. Across the landscape, successional changes follow several pathways. When vegetation change is influenced by several factors, a multi-scale model is necessary to demonstrate interactions and feedbacks and accurately describe successional patterns. Absence of fires, with or without grazing, leads ultimately to a Juniperus/Quercus woodland with grazing intensity primarily influencing the fuel load and hence fire intensity.     

Ecological succession in oligotrophic pastures of central Spain

The dynamics of oligotrophic pastures were analyzed in the area of El Pardo (Central Spain), and related with geomorphological features and time elapsed since the last ploughing. A sampling of the area was carried out regarding these two factors. The data were subjected to correspondence analysis, which showed the progressive replacement of species related to succession, variation along slopes, with a tight interaction between both phenomena.The correspondence between vegetation change and slope geomorphology is closer as succession progresses.Authoritics for species names are meationed in Table 1.     

流域径流泥沙对多尺度植被变化响应研究进展

植被变化与流域水文过程构成一个反馈调节系统,是目前生态水文学研究的重点对象.由于植被自身的生长发育以及受自然因素和人为干扰的作用,植被变化具有多尺度性;由于受流域水文环境的异质性和水文通量的变化性的影响,流域水文过程也同样具有多尺度性.因此,只有通过对不同尺度生态水文过程分析,才能揭示流域径流泥沙对植被变化的响应机理.从不同时空尺度回顾了植被生长、植被演替、植被分布格局变化、造林以及森林经营措施等对流域径流泥沙影响的主要研究成果;概括了目前研究采用的3种主要方法,即植被变化对坡面水流动力学影响的实验室模拟、坡面尺度和流域尺度野外对比观测实验以及水文生态模型模拟方法;分析了植被变化与径流泥沙响应研究要考虑的尺度问题,从小区尺度上推至流域尺度或区域尺度时应考虑不同的生物物理控制过程.研究认为,要确切理解植被与径流泥沙在不同时空尺度的相互作用,必须以等级生态系统的观点为基础,有效结合生态水文与景观生态的理论,从地质-生态-水文构成的反馈调节入手,系统地理解植被变化与径流泥沙等水分养分之间的联系及反馈机制,建立尺度转换的基础.同时,作为有效的研究工具,今后水文模型的发展应更加注重耦合植被生理生态过程以及景观生态过程,从流域径流泥沙对多尺度植被变化水文响应的过程与机制入手,为植被恢复与重建、改善流域水资源状况和流域生态环境奠定基础.     

Successions in the forest-steppe under climate changes: a modelling approach

The paper represents an attempt to apply the general principles of modelling vegetation dynamics under climate changes to a study of the long-term vegetation dynamics in the forest-steppe zone of the European territory of Russia, with a purpose to forecast under special climatic scenarios. An original technique is used to construct a Markov chain as a model of vegetation succession. The technique emanated from gebotanic knowledge generalized as a scheme of successional transitions with estimates of the average duration for certain stages of succession. Whenever the knowledge related the stage duration to certain (climate-sensitive) factors of the environment, the fundamental potentiality arises to model the temporal course of succession as a function of a given scenario for how the key factors change. In the formal terms, the model represents a random chain of the Markov kind with a finite number of states and discrete time of transitions by the given scheme. Relative square distributions of succession stages under concern at any time moment (within an adopted scenario) appear as the model outcome (forecasts), as well as estimates of the attainment time for certain states of the vegetation in the territory under study. A method is proposed to describe dynamics of the phytomass production and stores (and the corresponding model trajectories are obtained) for a given scenario.     

The dynamics of the dune vegetation on the Polish Baltic coast

This paper deals with the Baltic coastline in Poland. Features of the climate, geomorphology, substratum, soils and vegetation are outlined. The historical forest succession is based on the results of palynological studies of fossil soils. The present-day dynamics of the plant communities are examined from the viewpoint of primary succession, regression, regeneration and secondary succession. The primary succession on moving dunes is described with particular reference to deflation fields. Attention is drawn to the spatial changes in the communities from the 16th to the 20th century as a result of natural and human factors. This study shows that during the 19th and 20th centuries and especially in the last 25 years, the dynamics of the dunes and their vegetation have been much reduced, owing to the widespread stabilization of the substratum by forests and the ongoing abrasion of the coastal dunes.     

A dynamic global vegetation model for use with climate models: concepts and description of simulated vegetation dynamics

Changes in vegetation structure and biogeography due to climate change feedback to alter climate by changing fluxes of energy, moisture, and momentum between land and atmosphere. While the current class of land process models used with climate models parameterizes these fluxes in detail, these models prescribe surface vegetation and leaf area from data sets. In this paper, we describe an approach in which ecological concepts from a global vegetation dynamics model are added to the land component of a climate model to grow plants interactively. The vegetation dynamics model is the Lund–Potsdam–Jena (LPJ) dynamic global vegetation model. The land model is the National Center for Atmospheric Research (NCAR) Land Surface Model (LSM). Vegetation is defined in terms of plant functional types. Each plant functional type is represented by an individual plant with the average biomass, crown area, height, and stem diameter (trees only) of its population, by the number of individuals in the population, and by the fractional cover in the grid cell. Three time‐scales (minutes, days, and years) govern the processes. Energy fluxes, the hydrologic cycle, and carbon assimilation, core processes in LSM, occur at a 20 min time step. Instantaneous net assimilated carbon is accumulated annually to update vegetation once a year. This is carried out with the addition of establishment, resource competition, growth, mortality, and fire parameterizations from LPJ. The leaf area index is updated daily based on prevailing environmental conditions, but the maximum value depends on the annual vegetation dynamics. The coupling approach is successful. The model simulates global biogeography, net primary production, and dynamics of tundra, boreal forest, northern hardwood forest, tropical rainforest, and savanna ecosystems, which are consistent with observations. This suggests that the model can be used with a climate model to study biogeophysical feedbacks in the climate system related to vegetation dynamics.     

1992—2018年内蒙古自治区植被动态演替特征及驱动力

人类的建设与破坏活动是植被动态变化的重要根源之一,利用遥感探究植被演替的量化监测过程及驱动力能够很好揭示人类活动对生态本底的影响。本研究利用欧洲航天局逐年土地覆被数据及地理学信息图谱方法,从植被型组、植被型尺度分析1992—2018年内蒙古自治区植被动态演替方向、演替速度及演替序列,明晰植被演替特征并量化其演替驱动力。结果表明: 研究期间,内蒙古自治区植被数量结构为“植增荒减”,具体年增长速率依次为耕地(353.10 km²)>草原(243.92 km²)>森林(-16.22 km²)>灌丛(-120.37 km²)>荒漠(-556.31 km²),并且空间相邻分布的草原、荒漠、灌丛三者的面积变化存在权衡关系。植被演替空间呈“绿进沙退”格局,演替热点集中于西辽河平原、内蒙古中部荒漠-草原交界处及黄河沿岸;植被演替序列结构复杂,进展、逆行演替相互交错,不同群落演替流量的截流率差距突出,其中,植被型组草原、灌丛与植被型草地、雨养农田群落在演替过程中截获最多演替流量。植被动态演替的核心驱动力为农牧业生产、经济发展水平、人口规模、生态工程、气候变化。作为“植物群落学-景观生态学”的实例研究,本研究结果可为植被格局优化、演替等级提升等生态措施实施空间的划定提供科学依据。     

The vegetation of Flat Top Hill: An area of semi-arid grassland/shrubland in Central Otago, New Zealand

An account is given of the vegetation of Flat Top Hill, in the driest part of semi-arid lowland Central Otago, New Zealand. Although highly modified, the area was acquired for conservation in 1992, following almost 150 years of pastoral use. The vegetation was sampled in a composite scheme using permanent monitoring sites placed to include the majority of habitats and communities present. A number of environmental factors were measured in each sample. Native species comprise 53% of the vascular flora of the area (211 species). From multivariate analyses of the data collected over three seasons, fourteen 'communities' are recognised. Although there are few constant or faithful species, strong relationships are shown with certain environmental parameters. Moisture stress is the major environmental influence on the vegetation; soil depth and past disturbance are secondary determinants. The communities differ by a factor of 10 in vascular species richness; the richest communities, and those with the greatest native component, are those around rock tors. Many of the communities present have not been reported from other vegetation surveys in Central Otago Moisture stress at xeric sites in the dry core of the region has excluded some exotic species, and allowed the survival of the native component, including three tiny spring ephemerals. Near elimination of grazing, as a result of reservation, will probably lead to an increase in the cover of taller, palatable exotic grasses and Thymus vulgaris, which may threaten the survival of some native species. Optimum management, for recovery or persistence of native species, may comprise exclusion of grazers in some areas, but continuity of grazing in others.     

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。     

基于地学信息图谱的重庆岩溶石漠化植被恢复演替研究

重庆岩溶石漠化区的植被恢复演替动态变化研究对于该地区的石漠化治理和生态恢复具有十分重要的指导意义。而多时相的遥感数据和地学图谱分析法为植被恢复的研究提供了一种动态性和综合性的研究方法。以重庆市中梁山的典型植被恢复区为例,在基于1996、2001、2007和2013年4期遥感影像解译分类的基础上,采用"空间代替时间"的生态学植被演替研究方法,建立重庆市中梁山区退耕还林前后的植被恢复演替图谱,并结合地学图谱的相关分析方法,得到该区的植被恢复演替动态格局演变规律,体现了空间信息科学技术、生态学方法和地学信息图谱分析法在植被恢复演替研究中的有效结合。结果表明:(1)运用BP神经网络和BP算法进行分类,分类精度达到87.42%,比传统监督分类提高了5.57%。(2)自2002年全国范围内的"退耕还林(草)"工程全面启动后,该区域植被恢复演变特征明显,耕地面积明显减少而植被面积明显增加。(3)从2001—2013年,植被演替在该时期内依然存在着进展演替和逆向演替两个方向。虽然逆向演替比例仅占到18.63%,但它却使该区的演替研究变得复杂。(4)质心反映了各植被类型在恢复演替过程中的聚散与迁移,1996—2013年,马尾松群落和落叶阔叶林群落的质心变化较小,其他植被群落的质心都有很明显的变化。     

Implementation of a hierarchical global vegetation classification in ecosystem function models

Abstract. We propose an alternative approach for the currently used biogeographic global vegetation classifications. A hierarchical vegetation classification system is proposed for consistent and routine monitoring of global vegetation. Global vegetation is first defined into six classes based on plant canopy structure and dynamics observable by remote sensing from satellites. Additional biome variability is then represented through a remote sensing derived leaf area index map, and direct climate data sets driving an ecosystem model to compute and map net primary production and evapotranspiration. Simulation results from an ecosystem function model suggest that the six canopy structure-based classes are sufficient to represent global variability in these parameters, provided the spatio-temporal variations in Leaf Area Index and climate are characterized accurately. If a bioclimatically based classification is needed for other purposes, our six class approach can be expanded to a possible 21 classes using archived climatic zones. For example, tropical, subtropical, temperate and boreal labels are defined by absolute minimum temperature. Further separation in each class is possible through changes in water availability defined by precipitation and/or soils. The resulting vegetation classes correspond to many of the existing, conventional global vegetation schemes, yet retain the measure of actual vegetation possible because remote sensing first defines the six biome classes in our classification. Vegetation classifications are no longer an end product but a source of initializing data for global ecosystem function models. Remote sensing with biosphere models directly calculates the ecological functions previously inferred from vegetation classifications, but with higher spatial and temporal accuracy.     

High-resolution vegetation history of West Africa during the last 145 ka

The essential characteristics of the vegetation dynamics of tropical Africa remain only partially known. This study assesses the succession of vegetation-types over Central Africa during the last two glacial/interglacial cycles. Analysis of core KZai 02, which contains pollen from the Zaire River watershed (latitudes 9°N–13°S), allows the investigation of long-term patterns of plant ecosystem development and their climatic causes. Core KZai 02 (18.20 m long) was recovered from 6°24.20′S/9°54.10′E in the uppermost axial edifice of the Zaire deep sea fan. The chronology of this sedimentary archive was established using nannofossils and correlations of pollen and total organic carbon signals with the nearby core GeoB1008. The pollen record indicates that: (i) glacials (MIS 6, 4, 2) are marked by the development of afromontane (Podocarpus) forest at high altitudes when central basin lowlands were occupied by Cyperaceae marshes and savannah; (ii) during interglacials (MIS 1, 5) lowland forests were developed, marked by the successive expansion of pioneer, warm-temperate, rain forests, and mangrove indicating sea-level rise; (iii) glacial-interglacial transitions (MIS 6/5, 2/1) display similar vegetation dynamics. The strong evidence of afromontane forest and the opening of the vegetation during glacials suggest a reduced latitudinal distribution of rainfall by the strengthening of the trade wind system. West African monsoon systems were enhanced during interglacials, allowing the progressive development of lowland forests. The development of rain and pioneer forests during glacial Heinrich stadials suggests an enhancement of water availability in tropical Africa associated with these high-latitude events. However, no augmentation of wind activity described by previous studies is evidenced by our pollen record. Similar vegetation successions during glacial/interglacial transitions suggest the diachronous and stepped intervention of CO₂ (emphasizing the influence of temperature on plant ecosystems) and water availability.