深圳市植被受损分级评价及其与景观可达性的关系

植被受损评价及其受损成因分析是快速城市化地区生态保护和管理工作的重要基础研究课题。以深圳市2007年航空影像数据、2007年IRS卫星数据以及1 ∶ 10万电子地形图为基础数据,建立植被受损以及人为活动强度空间特征的表征方式,通过叠图分析及统计分析建立两者之间的响应关系,用以揭示人为活动对植被的影响程度及方式。进行了深圳市植被受损情况分级评价和景观可达性分级评价;然后通过两种分级评价结果的Pearson相关性分析和叠图统计分析,解析植被受损与景观可达性空间分异特征之间的关系。研究结果表明,深圳市人为干扰表现为人造纯林和生态风景林的营建、果园的种植以及极端机械干扰3种类型,受损程度可以分成6级。景观可达性能够定量化描述人为活动强度的空间分异特征,全区可达性程度可以分成5级。叠图分析结果显示,景观可达性水平与植被受损程度之间为正相关关系,相关系数为0.794。利用本研究方法还可以有效解析植被受损程度与人为活动空间分异特征之间的关联细节。     

Compositional differentiation,vegetation‐environment relationships and classification of willow‐characterised vegetation in the western Eurasian Arctic

Question: How does willow‐characterised tundra vegetation of western Eurasia vary, and what are the main vegetation types? What are the ecological gradients and climatic regimes underlying vegetation differentiation? Location: The dataset was collected across a wide spectrum of tundra habitats at 12 sites in subarctic and arctic areas spanning from NW Fennoscandia to West Siberia. Methods: The dataset, including 758 vegetation sample plots (relevés), was analysed using a TWINSPAN classification and NMDS ordination that also included analyses of vegetation‐environment correlations. Results: Based on the TWINSPAN classification, eight vegetation types characterised by willow (cover of upright willows >10%) were discerned: (1) Salix glauca‐Carex aquatilis type, (2) Aulacomnium‐Tomentypnum type, (3) Salix‐Betula‐Hylocomium type, (4) Salix lanata‐Brachythecium mildeanum type, (5) Salix‐Pachypleurum type, (6) S. lanata‐Myosotis nemorosa type, (7) Salix‐Trollius‐Geranium type and (8) Salix‐Comarum palustre‐Filipendula ulmaria type. Willow‐characterised vegetation types were compositionally differentiated from other tundra vegetation and were confined to relatively moist valley and sloping tundra sites, from mire to mineral soils. These vegetation types were encountered across a broad latitudinal zone in which July mean temperature ranged from 6 to 10°C. Conclusions: Willow‐characterised tundra vegetation forms a broad category of ecologically and geographically differentiated vegetation types that are linked to dwarf shrub tundra, shrub tundra or mire. Because of complex ecological gradients underlying compositional differentiation, predicting the responses of willow‐characterised tundra vegetation to a warming climate may be complicated.     

The importance of snow in species distribution models of arctic vegetation

Snow cover is characteristic of high‐latitude and ‐altitude ecosystems where snowpack properties regulate many ecological patterns and processes. Nevertheless, snow information is only rarely used as a predictor in species distribution models (SDMs). Methodological difficulties have been limiting both the quality and quantity of available snow information in SDMs. Here, we test whether incorporating remotely sensed snow information in baseline SDMs (using five climate‐topography‐soil variables) improves the accuracy of species occurrence and community level predictions. We use vegetation data recorded in 1200 study sites spanning a wide range of environmental conditions characteristic of mountain systems at high‐latitudes. The data consist of 273 species from three ecologically different and evolutionarily distant taxonomical groups: vascular plants, mosses, and lichens. The inclusion of the snow persistence variable significantly improved the predictive performance of the distribution and community level predictions. The improvements were constant, irrespective of the evaluation metric used or the taxonomic group in question. Snow was the most influential predictor for 36% of the species and had, on average, the second highest variable importance scores of all the environmental variables considered. Consequently, models incorporating snow data produced markedly more refined distribution maps than simpler models. Snow information should not be neglected in the construction of species distribution models where ecosystems characterized by seasonal snow cover are concerned.     

Complexity and idiosyncrasy in the responses of algae to disturbance in mono- and multi-species assemblages

There is considerable debate about whether stability (e.g. inertia) of an assemblage, or of individuals in an assemblage, is positively associated with the number of species or whether there are idiosyncratic effects of particular species. We assessed the general model that the loss of an individual alga, caused by trampling, is greater in monospecific than in multi-species stands but that the responses of algae are idiosyncratic, depending on the morphology of the species. The experiment was done on conspicuous and dominant algae with different morphology on temperate Australian rocky shores: the fucalean algae Hormosira banksii and Sargassum sp. and the coralline alga Corallina officinalis. We assessed the relative and interactive effects of the extent of trampling (number of paths) and the localised intensity of trampling (number of travels per path) on the three algae. The number of paths trampled (the extent of disturbance) had more impact on each alga than the number of times paths were travelled (the intensity of disturbance). As predicted, H. banksii was most susceptible to trampling at each level than were the coarser algae Sargassum sp. and C. officinalis. There was a consistent trend for each alga to be more inert to trampling when in the presence of the other two species than when in monospecific stands, but this was only statistically significant (P < 0.05) for the softer alga H. banksii. The responses of H. banksii and Sargassum sp. to disturbance seemed, in many cases, to be due to the presence of C. officinalis rather than to "diversity" per se. The relationship between the number of species and stability is complex in intertidal habitats, depending on the species and the combinations of species with which it grows.     

Spatial distribution pattern of the riparian vegetation in a basin in the NW Spain

The riparian vegetation of a basin in the NW Spain was studied to establish its spatial variation pattern and to relate floristic and structural differences in the community to environmental factors. Eighty-seven sampling units in 43 sampling stations were used. Samples were classified in 5 groups using Two Way Indicator Species Analysis (TWINSPAN). Three groups represented reaches with riparian wood along their banks: Mediterranean alderwoods and shrubby willow woods. The remaining two corresponded to floodplains with vegetation colonizing moderately eutrophicated deposits of gravel. Structural characteristics of richness and diversity differentiated the alder woods. In these, the shaded environment created by the woody species limited herbaceous vegetation development. This was dominated by Carex acuta subsp. broteriana. Classification and CCA ordination results were compared. The TWINSPAN groups could be recognized in the CCA graph. The ordination was related to a pollution gradient associated with altitude. This pollution gradient involved bank ruderalization, incorporation of nitrophilous species and a decrease in the vegetation quality. The influence of the lithological features on vegetation was also evident.     

The impact of trampling by tourists on a high altitudinal grassland in the Tyrolean Alps,Austria

The long term effect of tourist trampling on a high altitudinal grassland (Caricion curvulae) in the Tyrolean Alps was investigated.Even under slight trampling the frequency of sensitive species decreases. The most sensitive species were found to be fruticose lichens, followed by mosses, some forbs and broadleaved grasses. Tolerant to trampling are the dominant species Carex curvula, and Ligusticum mutellina, which do not disappear completely even at a tourist frequency of 150 tourists per metre per day. Trampling increases soil bulk density moderately but has no marked effect on the soil water content.Comparison with high alpine sedge heath vegetation in North America shows a surprising uniformity of this vegetation type in response to trampling and also indicates that the common generalisation that alpine ecosystems are fragile and sensitive to disturbance does not hold true in this context. Furthermore these results represent evidence against the theory that ecosystems with low diversity are much more sensitive to arteficial impact than ecosystems with high diversity. However, if even the most resistant plants which are the dominant sedges are destroyed completely the rate of recovery is very low and may last for a long time. In the case of Carex curvula this is supported by the fact that it has very low seed production and grows mainly vegetatively. The rate of spread of the rhizome system of this species is 8 mm in 10 years. Similar figures may apply for the sedge species dominating in the alpine vegetation of North America. Thus fragility of this vegetation in regard to trampling does not mean low tolerance but low regeneration.Nomenclature of species follows Ehrendorfer (1973) for vascular plants and Poelt (1974) for lichens.The PCA calculations were done at the Computer laboratory of the University of Wales during a post doctoral stay at the School of Plant Biology in Bangor, U.K. I would like to record my thanks to Prof. Dr. P. Greig-Smith for fruitful discussions and reading the draft.     

An update of the vegetation classification in China

The vegetation classification in China was updated by referring to recent advances for vegetation classification worldwide and on the basis of our former paper Recognition and Proposal on the Vegetation Classification System of China (hereafter, “Recognition and Proposal”). In this revision, the criteria for vegetation classification were discussed and unified, and a quantified standard for high, medium, and low level units in a new hierarchical classification scheme was supplemented. Compared with the old classification scheme in “Recognition and Proposal”, the units at the level of vegetation type were substantially changed. Finally, in order to improve mutual communication among international peers, a comparison was carried out between the new revised scheme and each of International Classification and Mapping of Vegetation of UNESCO, The National Vegetation Classification Standard of United States, and The Braun-Blanquet Classification Scheme.     

Riverain vegetation in the Nile valley in Upper Egypt

Abstract. Naturaland semi-natural plant communities occurring in the Nile Valley in Upper Egypt are described and their position in the zonation along the river bank interpreted. With the help of ordination and classification methods relationships among the 13 community types and their distribution along the predominating moisture gradient are elucidated. The vegetation of the Nile Valley can be described as a series of discrete plant community types on the basis of their floristic composition, structural components and habitat conditions. The communities can be grouped into four higher units, considered as formations: swamp, meadow, thorn-bush and riverain woodland.     

典型喀斯特区不同植被恢复方式苔藓功能性状及其对土壤因子的响应

苔藓功能性状反映了苔藓对生长环境的响应与适应,对其所在土壤表层的功能特性具有重要指示意义。但喀斯特地区植被恢复初期苔藓功能性状与土壤因子关系还缺乏深入认识。以典型喀斯特峰丛洼地人工林、牧草和人工林+牧草3种植被恢复方式下苔藓为研究对象,分析了苔藓功能性状及其与土壤因子的关系。结果表明：(1)苔藓单位面积冠层质量(CMA)、冠层密度(CD)、生物量和饱和吸水量在牧草地有最大值。苔藓冠层高度在牧草地显著低于人工林和人工林+牧草,且牧草地苔藓营养元素含量较低。(2)人工林和人工林+牧草表层土壤(0—2 cm)养分含量和土壤含水量(SWC)较高,牧草地表层土壤养分含量和SWC较低。(3)冗余分析表明,苔藓营养性状(营养元素含量及化学计量比)与土壤因子主要呈正相关关系,而CMA、CD及生物量关联指标与土壤因子主要呈负相关关系,土壤交换性镁和SWC是影响苔藓功能性状的主要土壤因子。研究结果表明,苔藓通过不同的性状组合适应不同植被类型生境,其中牧草地更适宜苔藓拓殖和生长,可考虑将苔藓应用于牧草地对喀斯特退化生态系统进行修复。     

Towards objectivity in vegetation classification: the example of the Austrian forests

We present a numerical classification of 2145 objectively sampled relevés from the entire forest area of Austria (Central Europe). The sample sites were selected by a combined method involving a systematic matrix and stratified random sampling. A TWINSPAN classification led to 32 clusters which are described in detail. Three main groups can be distinguished: (1) Alpine-dinaric coniferous forests on carbonate soils, (2) Coniferous forests on acid soils and (3) Deciduous forests. These groups correspond with accuracy to the classes Erico-Pinetea, Vaccinio-Piceetea and Querco-Fagetea in the traditional Braun-Blanquet system. Thus, the value of the Braun-Blanquet approach is supported by more or less objective sampling and numerical classification methods. The assumption of the objective existence of ecological species groups is strongly supported, too. Moreover, our results may help to solve some controverse points discussed in the European forest classification regarding the delimination between the three mentioned classes. This revised version was published online in August 2006 with corrections to the Cover Date.     

The southern limit of the Mediterranean vegetation in the Sahara during the Holocene

Holocene records from the southern Sahara in Niger allow a reconstruction of the vegetation history and inform us about the former extension of the Mediterranean. Both pollen and charcoal analyses evidenced the direct contact of Sudanian and Saharan savannas during the middle Holocene at about 19°N, whereas at 20°N the transition from the Saharan savanna to the desert was found. In southwestern Libya (26°N) a combination of a Saharan desert vegetation and a semi‐desert Artemisia shrub on the plateaus demonstrated the contact with Mediterranean influenced formations. Regular ash and charcoal layers in middle‐Holocene sediments of the northern Niger prove an early interference of man with the vegetation development. One has to imagine that, in combination with the cattle‐keeping and the later metal production, man could have changed the former northern Sudanian vegetation into the present Sahelian savanna system from the middle Holocene on.     

对中国植被分类系统的认知和建议

《中国植被志》的编写工作已经启动, 藉此征求修订《中国植被分类系统》意见之际, 提出几点看法与建议: 1)贯彻原先制定的中国植被“高级分类单位偏重于生态外貌, 而中、低级分类单位则着重种类组成和群落结构”的分类原则。这一思想与当前国际上植被分类的发展是一致的。2)中国植被分类既要符合中国植被的特点, 又要适应全球植被分类的发展, 名词概念应尽量与国际上的广泛理解相一致。3) “群丛”是《中国植被志》描述的基本对象, 其概念需要统一, 以避免歧义和可能导致的南北“群丛”的不等质。资料不足的类型应组织野外补点调查。4)植被分类等级系统是严格的, 但各等级又是开放的, 可适当地增设高级分类单位, 以适应类型扩展之需要。该文附有从植被型纲到植被型的建议草案。     

安太堡矿区植被恢复过程主要种生态位梯度变化研究

通过生态位宽度与生态位重叠指数 ,结合 TWINSPAN分类与 DCA排序 ,研究植被恢复过程中优势种生态位的梯度变化 ,以及这些种在不同群落类型中的地位、各群落之间的关系 .结果表明 :TWINSPAN结合 DCA对生态位宽度进行分析 ,可以很好地反应种的生态位梯度和以这些种为优势种的群落的结构梯度和环境梯度 ,同时还可以看出光因子和水分是决定优势种生态位梯度变化的主要因子 .各优势种的生态位在不同群落中又随种类组成的变化而变化 ,这种变化反映了森林群落的植被恢复效果最好 ,灌丛群落植被恢复效果普遍好于草地群落 ,而森林群落中刺槐和油松混交恢复效果最好     

An assessment of the aquatic and wetland vegetation of the Upper Mississippi River

Illinois, Iowa, Minnesota, Missouri, and Wisconsin have strong botanical traditions that have resulted in a macrophyte literature which documents the identity, taxonomy, floristics, and ecology of aquatic macrophytes and wetland vegetation of the Upper Mississippi River and its floodplain. These findings are reviewed with respect to floristics, vegetation dynamics (patterns, history, production and management), and environmental changes that impact vegetation. Aspects requiring future study are noted to direct subsequent investigations.     

Effects of altitude and livestock on the regeneration of two tree line forming <Emphasis Type="Italic">Polylepis</Emphasis> species in Ecuador

Regeneration is known to be limited at many temperate tree lines, but very little data is available on the impacts of altitude and anthropogenic disturbance on regeneration patterns along tropical tree lines. The study focused on the reproductive traits of two Polylepis species in the Páramo de Papallacta in Ecuador along an altitudinal gradient, and involved different intensities of cattle trampling within subsequent altitudinal ranges. We analyzed flowering, fruit set, seed viability, germination, and seedling establishment as well as stand structure of Polylepis incana and P. pauta. The numbers of P. incana inflorescences and seedlings per m2 showed a marginally significant decrease with increasing altitude. Mean tree height was significantly lower at higher altitudes, while stem number increased. The number of P. pauta inflorescences also decreased significantly upslope. In both forest types, trampling was found to have a positive impact on seedling abundance, presumably due to the removal of the litter layer. Thus, there was no evidence of negative effects of moderate cattle grazing on both tree line species. However, sapling establishment was minimal inside the forest stands at all altitudes and grazing levels, and we consequently observed a low proportion of narrow stems within all investigated forests. Our results show that, along with vegetative growth limitations of adult trees, important regeneration traits such as seedling and inflorescence numbers are also influenced by altitude, which might contribute to the formation of the upper tree line. Nevertheless, recruitment in the forest interior was low overall indicating that further factors, such as light conditions, affect regeneration of the studied species.     

不同更新方式对林地植被生长及土壤性状的影响

本文研究天然次生林采伐迹地的三种更新方式对林地植被及土壤性状的影响。结果表明,炼山人工造林对林地植被和土壤有一定的破坏作用,是影响林木生长、导致物种丧失、引起林地水土流失和地力衰退的重要原因。不同林分物种丰富度为:天然更新 >人促更新 >炼山人工造林;林下植被生物量为:人促更新 >天然更新 >炼山人工造林。不炼山的天然更新和人促更新,有利于物种多样性保护、植被生长、林地土壤理化性状改善和土壤肥力提高,并具有更高的经济效益。     

山西岚县皇姑梁小流域人工植物群落生态

应用双向指示种分析法（TWINSPAN）和除趋势对应分析（DCA）等数量分析方法,对山西岚县皇姑梁小流域人工植物群落生态关系进行研究,将该人工植被划分为12个群丛,分别位于不同的海拔高度和坡向。分类结果很好地反映了人工植物群落类型及优势种的分布与环境因子的关系,并在DCA二维排序图上得到了较好的验证。DCA排序轴反映了群落土壤含水量、坡向、海拔高度、人工植被恢复时间和物种多样性的梯度变化,表明土壤含水量、坡向、海拔高度、物种类型及其配置模式是影响人工植物群落分布和变化的主要环境因子,不同物种配置模式对群落演替和物种多样性变化有重要影响,油松＋华北落叶松．沙棘、小叶杨＋油松、油松-沙棘、油松-柠条锦鸡儿等组成的乔灌混交林的物种多样性高于柠条锦鸡儿灌木纯林,并且油松＋华北落叶松-沙棘混交林的物种多样性高于小叶杨＋油松混交林,混交林的生态恢复效果优于纯林,并且对该小流域的生态恢复作用明显。华北落叶松适合在该小流域海拔较高的梁坡顶、半阳坡、半阴坡和阴坡生长,小叶杨适合在其海拔较低的沟底、半阳坡和半阴坡生长,而油松、沙棘、柠条锦鸡儿的生态适应性强,可在其不同海拔和坡向生长。人工植物群落的演替进程,遵循地带性植物群落演替规律。随着群落演替,野生植物不断侵入,油松、华北落叶松、小叶杨等人工林郁闭度增加,沙棘、柠条锦鸡儿等逐渐退化,油松、华北落叶松、小叶杨等出现枯枝、死株现象,这是自然稀疏的结果,亟待加强管理。     

云南热带森林植被分类纲要

热带森林是云南的重要植被类型,虽对云南热带森林植被的系统分类及研究在《云南植被》中有所体现,并发表了大量论文,但在植被类型的划分、命名及其解释上却不尽相同,特别是对群系的记录很不全面。该文总结已掌握的研究资料,参考世界类似热带森林植被的研究成果,系统地对云南热带森林植被的类型、分类、物种组成和群落特征等进行了归纳。结果表明:云南的热带森林植被包括3个主要的植被型,即热带雨林、季雨林、季节性湿润林。云南的热带雨林是在亚洲热带北缘季风气候下发育的在水分、热量和分布海拔上均到了极限条件的热带雨林类型,分为热带季节性雨林和其山地变型—热带山地雨林二个植被亚型,前者包括19个群系,后者包括12个群系。文中的热带季雨林是依据其原始定义指介于热带雨林与萨王纳之间的一种热带落叶至半常绿森林植被,其分布主要受水分条件制约,非纬向地带性植被;它们分为落叶季雨林和半常绿季雨林2个植被亚型,前者包括7个群系,后者包括3个群系。把分布于云南南部石灰岩山地的在一些植物学文献中称之为"石灰岩季雨林"的热带森林植被,考虑其常绿至半常绿的外貌特征、特殊的植物区系组成以及乔木层没有一个明显的无叶(落叶)期(其落叶现象可能主要由于局部生境的干燥和历史的原因,并非是由于地区性气候干旱所导致),它们与季雨林的原始定义不符;该文使用名称热带季节性湿润林来定义这类发生在石灰岩山中、上部,在热带季节雨林带之上的热带山地垂直带上的植被类型。季节性湿润林也分为季节性常绿湿润林及季节性半常绿湿润林2个植被亚型,各包括2个群系。