Changes in the flora and vegetation of the coastal dunes of Voorne (The Netherlands) in relation to environmental changes

Ecologically the former isle of Voorne is very varied. This is reflected by an exceptionally high number of plant species and vegetation types. Many data regarding flora and vegetation have been collected during more than 25 years. A comparison of the early and the later data show that in this period many changes have taken place in flora and vegetation. The changes are partly the result of a natural development of the vegetation, but to a considerable extent they are due to human activities in the coastal area itself and in its surroundings. Examples of changes produced by natural developments and by human activities are given. The effects on flora and vegetation of the area are illustrated by comparing flora inventories, vegetation maps and permanent plot studies. In addition, the future development in the region which will strongly affect its natural value, is discussed.I would like to thank Michiel Boeken, Joke van der Linden and Elly van Oosterhoud who carried out the second flora inventory and Jeanette van Beuzekom and Inge Boelens who mapped parts of the Voorne dune area. I am particularly indebted to Wiecher Smant who offered assistance in many ways.     

The Influence of Natural and Climatic Factors on the Number of Saiga (<Emphasis Type="Italic">Saiga tatarica</Emphasis> Pall.) (Bovidae,Artiodactyla) between the Volga and Ural Rivers

The features of Uralian saiga habitats are discussed. Periods of high and low abundance of the animals, which alternate depending on the productivity of vegetation communities and territorial humidity (the number of watering places) due to climate changes, are shown. After periodic cases of the mass death of saiga, their population is quickly restored to its previous level, which is likely to be facilitated by the existing feed and water resources.     

Plant communities of the Mt Wellington Range,Tasmania

Associations among species of vascular plants in twelve predefined vegetation zones on Mt Wellington, Tasmania, are described. The vegetation zones were based mainly on the dominant species of eucalypt contained therein, following an approach used previously by Martin (1940). The twelve zones were subsequently reduced to a total of six cluster groups using hierarchical classification procedures. Character species, in the sense of the Braun-Blanquet (1928) system of phytosociology, are identified and tabulated for each group. It is suggested that the division of a survey area into zones based upon dominant euealypts may be applicable to the study of vegetation communities in other parts of Tasmania.     

A late Holocene pollen diagram from the Megaris,Greece, giving possible evidence for cultivation of<Emphasis Type="Italic"> Ceratonia siliqua</Emphasis> L. during the last 2000 years

A late Holocene pollen profile from the Megaris on the eastern Gulf of Corinth shows a vegetation which was strongly influenced by human impact throughout. A Pistacia-Phillyrea maquis, which is reflected in the older parts of the profile, changed later to a more degraded vegetation type. In the uppermost part Pinus dominates the pollen spectrum. A continuous record of Ceratonia siliqua pollen older than cal a.d. 100 is of special interest.     

Long-term changes (1953–1990) in the salt marsh vegetation at the Boschplaat on Terschelling in relation to sedimentation and flooding

Long-term vegetation changes in permanent plots along two transects from the low to the high salt marsh at the Boschplaat on Terschelling between 1953 and 1990, were analysed in relation to sedimentation and flooding. In both transects, the number of plant species decreased between 1953 and 1990. In lower parts of the two transects the dominant plant species of the vegetation changed from Puccinellia maritima in 1953/54 to Limonium vulgare in 1980 to Atriplex portulacoides in 1990. The increase in A. portulacoides between 1980 and 1990 coincided with an increase in the thickness of the silt layer, caused by a sedimentation rate of about 5 mm per year. This sedimentation led to an increase in elevation but not to large changes in flooding frequency between 1953 and 1990, probably due to a sea level rise during the same period.In the higher parts of the salt-marsh transects Elymus athericus strongly increased and this species became dominant in 1980 and 1990. In these parts of the salt marsh, a small increase in elevation, in thickness of the silt layer, and in flooding frequency occurred between 1953 and 1990.The described changes in vegetation are discussed in terms of general succession of salt-marsh vegetation in relation to flooding and sedimentation.     

Assessing onset and length of greening period in six vegetation types in Oaxaca,Mexico, using NDVI-precipitation relationships

Variations in the normalized vegetation index (NDVI) for the state of Oaxaca, in southern Mexico, were analyzed in terms of precipitation anomalies for the period 1997-2003. Using 10-day averages in NDVI data, obtained from AVHRR satellite information, the response of six types of vegetation to intra-annual and inter-annual fluctuations in precipitation were examined. The onset and temporal evolution of the greening period were studied in terms of precipitation variations through spectral analysis (coherence and phase). The results indicate that extremely dry periods, such as those observed in 1997 and 2001, resulted in low values of NDVI for much of Oaxaca, while good precipitation periods produced a rapid response (20-30 days of delay) from a stressed to a non-stressed condition in most vegetation types. One of these rapid changes occurred during the transition from dry to wet conditions during the summer of 1998. As in many parts of the tropics and subtropics, the NDVI reflects low frequency variations in precipitation on several spatial scales. Even after long dry periods (2001-2002), the various regional vegetation types are capable of recovering when a good rainy season takes place, indicating that vegetation types such as the evergreen forests in the high parts of Oaxaca respond better to rainfall characteristics (timing, amount) than to temperature changes, as is the case in most mid-latitudes. This finding may be relevant to prepare climate change scenarios for forests, where increases in surface temperature and precipitation anomalies are expected.     

Distribution of Macrophytes in Relation to Environmental Factors in the Ter River,N. E. Spain

Most of the tested water quality factors increase downstream coinciding with changes in the aquatic vegetation, from typical species of fast-flowing oligotrophic waters to those of slower-flowing eutrophic waters. Several statistic analyses were carried out to relate physical and chemical parameters with plant distribution. Five vegetation types are found in a longitudinal distribution along the river system. They are dominated by bryophytes in the initial parts before the reservoirs and by higher plants in the final parts after the reservoirs.     

鄂尔多斯高原地区昆虫物种多样性研究

鄂尔多斯高原有特殊生境类型,本文研究了该地区的昆虫物种多样性变化及影响因素,得到以下结果：（1）利用巴氏罐诱法得到昆虫标本约5159号,其他无脊椎动物标本291号,鞘翅目为优势昆虫类群,其数量占昆虫标本总数的45．8％,其中拟步甲和步甲个体数量较多,占所有甲虫总数92．8％;（2）根据甲虫的物种多样性和丰富度的特点将4个调查地点分为两组：一组为以荒漠灌丛为主的杭锦旗和植被类型多样化的石灰庙,物种多样性指数,丰富度和个体数量较高;另一组为以人工植被区为主的石龙庙和新街镇,物种均匀度指数较高;（3）主成分排序（PCA）可以将该地区的甲虫群落分为人工植被区和荒漠植被区2种类型,反映降水和植被类型是决定甲虫群落组成的关键因素;（4）降水梯度对甲虫物种多样性有很大影响,物种多样性指数,均匀度指数与降水梯度呈显著的正相关关系;个体数量与降水梯度呈显著的负相关关系;物种的丰富度与降水梯度没有相关关系。以上结果表明,在鄂尔多斯高原地区,只有减少人为干扰,加强保护脆弱的原有植被,才能保护特有的昆虫种类;只有大力开展固沙造林植草,才能改善环境,提高该地区的昆虫物种多样性。     

Modern pollen–vegetation relationships along transects on the Whangapoua Estuary, Great Barrier Island, northern New Zealand

Aims To quantify pollen–vegetation relationships from saline to freshwater in an estuarine gradient from surface samples of the modern pollen rain, to allow more accurate interpretations of the stratigraphic palynological record. Location Whangapoua Estuary, Great Barrier Island, northern New Zealand. Methods Six transects were laid out along a vegetation sequence running from estuarine mud to freshwater swamp. Along these transect lines, 108 plots were sampled for vegetation and surface sediments from wet sand, mud, plant litter or moss (sand and mud sites are inundated by most tides, other sites less frequently). All sediment samples were analysed for pollen. The relationships between plant species frequency and pollen representation were examined at a community scale using twinspan and ordination analyses, and for individual species using fidelity and dispersibility indices, regression and box‐plot analyses. Results The quantitative relationships between source taxon vegetation frequency and its pollen representation varied between species due to differential pollen production and dispersal. twinspan of the surface pollen samples suggests five vegetation types: (A) mangrove (Avicennia marina); (C) Leptocarpus similis salt meadow; (D) Baumea sedges; (E) Leptospermum shrubland; and (F) Typha/Cordyline swamp forest. The (B) Juncus kraussii community is not represented palynologically owing to the destruction of its delicate pollen grains during acetolysis of samples. Detrended correspondence analysis places these communities on an estuarine‐to‐freshwater gradient. However, pollen assemblages at the seaward end of the salinity gradient are less clearly representative of the associated vegetation than those at the landward end, probably because the open vegetation at the former allows the influx of wind‐ and water‐dispersed pollen from surrounding vegetation. Main conclusions The vegetation pattern (zonation) at Whangapoua is reflected in the pollen rain. When the long‐distance and over‐represented pollen types are excluded, five out of six of the broad vegetation communities can be identified by their pollen spectra. Species with high fidelity and low‐to‐moderate dispersibility indices can be used to identify the vegetation types in the sedimentary sequences. The more open vegetation types at the ‘marine end’ of the sequence tend to be ‘overwhelmed’ by regional pollen, but the nature of the sediments and the presence of discriminatory species (e.g. A. marina, Plagianthus divaricatus, Cordyline australis), even in small amounts, will allow correct identification of the local vegetation represented in sedimentary palynological sequences. A box‐plot analysis indicates that the pollen and spore types A. marina (mangroves), Sarcocornia quinqueflora (salt meadow), P. divaricatus (sedges), Gleichenia (shrubland) and C. australis (swamp forest) are highly discriminatory in relation to vegetation type. These discriminatory palynomorphs help with the interpretation of stratigraphic pollen studies. However, salt marsh vegetation communities in the sediments must be interpreted with caution as the marine sediments are easily affected by erosion, bioturbation and tidal inundation effects.     

Rare Mollusca from the Lower Devonian Hunsrück Slate of southern Germany

Only ten gastropods have been recovered and a single hyolith found in the radiographic study of the Hunsrück fauna. Four gastropods are interpreted as retaining soft parts: the radula may be identified in one and perhaps the liver and digestive organs in the others. These gastropods may have moved into the area on floating vegetation. The hyolith probably lived on the bottom. Soft parts are present within its shell, but they are not readily interpreted. A tentacular mass anterior to a possible mantle cavity is present, with the bulk of the shell being filled by enigmatic tissue. ▭ Gastropoda, Hyolitha, soft parts, radula, pyritization.     

Holocene space-time succession of the Middle Atrato wetlands, Chocó biogeographic region, Colombia

Successional sequences from forested wetlands in the Middle Atrato River Basin were reconstructed using characterisation of present vegetation communities and palynological analysis. A 4.8 km transect, drawn across a river meander, and two 6 and 8 m deep sediment cores (San Martín and Villanueva) were collected in the floodplain within two different vegetation assemblages. Based on the floristic and environmental characteristics of the local vegetation communities, ecological changes spanning the last 4 ka (cal years BP) were analysed in San Martín and Villanueva cores. Present vegetation is dominated by four communities determined by flood tolerance and drainage conditions. We found Euterpe oleraceae, Mauritiella macroclada-Campnosperma panamensis and Oenocarpus bataua forests, and mixed forest and open vegetation in a gradient from poor to improved drainage conditions. Vegetation changes in the palynological record suggest that sedimentation and erosion processes on flood basins are due to changes in drainage conditions and to variable flooding levels.A wet period in the 4 to 2.7 ka interval is postulated, which might be related to sea level rise or local subsidence. Lower flooding levels and improved drainage conditions dominated the 2.7 to ∼ 1.6 ka interval, whereas a flooding event (and a hiatus) occurred between 1.5 and 0.5 ka. This flooding event might be synchronous with analogous events as recorded in the Colombian Amazonia between 1.6 and 1.45 ka. Forest disturbance, probably of anthropogenic origin, is recorded in both sites since 0.5 ka.     

Structure,function and floristic relationships of plant communities in stressful habitats marginal to the Brazilian Atlantic rainforest

The Brazilian Atlantic rainforest consists of a typical tropical rainforest on mountain slopes, and stands out as a biodiversity hotspot for its high species richness and high level of species endemism. This forest is bordered by plant communities with lower species diversity, due mostly to more extreme environmental conditions than those found in the mesic rainforest. Between the mountain slopes and the sea, the coastal plains have swamp forests, dry semi-deciduous forests and open thicket vegetation on marine sand deposits. At the other extreme, on top of the mountains (>2000 m a.s.l.), the rainforest is substituted by high altitude fields and open thicket vegetation on rocky outcrops. Thus, the plant communities that are marginal to the rainforest are subjected either to flooding, drought, oceanicity or cold winter temperatures. It was found that positive interactions among plants play an important role in the structuring and functioning of a swamp forest, a coastal sandy vegetation and a cold, high altitude vegetation in the state of Rio de Janeiro. Moreover, only a few species seem to adopt this positive role and, therefore, the functioning of these entire systems may rely on them. Curiously, these nurse plants are often epiphytes in the rainforest, and at the study sites are typically terrestrial. Many exhibit crassulacean acid metabolism. Conservation initiatives must treat the Atlantic coastal vegetation as a complex rather than a rainforest alone.     

Post-Soviet fire and grazing regimes govern the abundance of a key ecosystem engineer on the Eurasian steppe,the yellow ground squirrel Spermophilus fulvus

Aim

Grazing intensity and fire patterns across the Eurasian steppes have changed dramatically over the past decades due to the collapse of the Soviet Union in 1991, and Kazakhstan is now a global fire hotspot. The implications of these changes for ecosystem functioning are largely unclear. We aimed to understand the effects of changed grazing intensity and fire frequency on a key ecosystem engineer, the yellow ground squirrel Spermophilus fulvus, on a very large scale.

Location

Kazakhstan.

Methods

Ground squirrels were surveyed in an area of ca. 100,000 ha in the dry steppe of central Kazakhstan, using hierarchical distance sampling at more than 200 random points, stratified by fire frequency and livestock grazing intensity. We modelled abundance as a function of different variables, grouped at the landscape scale (fire and grazing), meso-scale (soil and vegetation structure) and at burrow scale (plant traits such as palatability, digestibility and nutrient content).

Results

Ground squirrels prefer areas of a high wormwood cover (Artemisia spp.) and high plant species richness, which are moderately grazed, preferably by cattle, with only rare fire occurrence. High squirrel densities were also related to the availability of nitrogen-rich plants of high nutritional value for herbivores.

Main Conclusions

Yellow ground squirrels seem to reach their density optima by balancing trade-offs between optimal foraging in areas of short, nutrient-rich vegetation and a good visibility of approaching predators. Post-Soviet changes in grazing pressure, resulting in higher fire recurrence rates due to grass encroachment and litter accumulation (i.e. fuel for wildfire), have likely affected the abundance of burrowing mammals and associated biodiversity across huge parts of the Eurasian steppes and semideserts.     

Hydrodynamic-ecological model analyses of the water quality of Lake Manzala (Nile Delta, Northern Egypt)

Lake Manzala remains the largest of the Nile Delta lakes and has undergone substantial recent changes particularly over the last 30 years due to regulation of freshwater inflows, land reclamation and increasing loads of BOD and nutrients. The latter are particularly associated with polluted drains flowing into the lake. An increasing fraction of the N load may also come from the expanding fish farming industry within and around the lake. Over the past 20–25 years, the N load from the drains has increased three times whilst the P load has remained approximately constant. This is despite a 40% reduction in freshwater inflows due to diversion of water towards the Sinai for land development. As a result of these changes, the concentration of total N in the drains has increased 4.5 times while the total P concentration has increased by 50% over the same period. Increases in nutrient concentrations can be attributed to increase in the use of fertilizer combined with an expanding population served by sewers, improved living standards and increased industrial production. Nutrient enrichment has resulted in declining water quality and eutrophication, especially in the southern parts of Lake Manzala. A combined hydrodynamic-ecological model has been set up for the lake and is used to analyse the development of water quality as a function of the load of organic material and nutrients. Model results show that 86% of the N load and 59% of the P load are retained within the lake. Despite the efficient treatment of wastewater by the lake ecosystem, approximately 6,000 tonnes of N and 1,300 tonnes of P are exported to the Mediterranean through the two main lake–sea connections. This nutrient export has important implications for coastal fisheries production. The present investigation suggests that the current anthropogenic nutrient load to the coastal zone exceeds that of pre-Aswan High Dam conditions despite large reductions in the annual pulse of water and nutrients brought about by the dam. A series of model simulations with reduced nutrient load are investigated in order to identify the conditions required to enable the propagation of vegetation throughout the lake. Submerged rooted vegetation is used as an indicator for water quality as it needs light for growth and in polluted, eutrophicated waters turbidity increases hampering vegetation growth. Simulation results indicate that the nutrient load has to be reduced to approximately 25% of the present loads if submerged rooted vegetation is to become re-established in the more polluted south eastern parts of the lake. Guest editors: J. R. Thompson & R. J. Flower Hydro-ecological Monitoring and Modelling of North African Coastal Lagoons     

青藏高原高寒草甸植被和土壤对短期禁牧的响应

为探讨青藏高原高寒草甸对短期禁牧的响应,设置冬季自由放牧和短期(2年)禁牧的对比试验。采用随机样方法调查植被群落盖度,分析地上和地下生物量、根冠比、植被地上和地下部分以及表层(0-10cm)土壤全碳、全氮和全磷含量、生态化学计量以及营养元素的关联性。研究结果显示:1)短期禁牧显著改变高寒草甸植被盖度、地上生物量、根冠比、植被全磷含量和N∶P,以及土壤全磷含量。2)相关性分析表明,禁牧后土壤全碳含量与植被地上全碳含量呈显著相关性,自由放牧后土壤全碳和全氮含量分别与植被地下部分全碳和全氮含量呈显著相关性。结果表明,不同的草原管理措施(禁牧、放牧)会改变高寒草甸植被与土壤养分分配及其平衡关系,同时,植被与表层土壤主要养分含量之间的关联性仅存在于部分植物器官与部分营养元素之间。     

近17年陕西榆林植被指数的时空变化及影响因素

植被指数是研究区域植被变化的重要手段。基于MODIS/Terra NDVI遥感影像数据,对陕西榆林市2000—2016年8月份NDVI进行像元尺度的时空变化及影响因素分析。结果表明,榆林有96.44%的区域植被指数是增加的,增加值在0—0.02/a区域面积占榆林的93.63%,呈显著增加趋势的面积占榆林的80.72%。复直线回归分析显示,气象因素对植被生长、演化起到了促进作用,人类活动使得植被指数等级变得更加均匀。人类活动抑制植被生长演化的区域占榆林总面积的45.04%,主要分布在榆林市最北部的府谷县、榆林市南部及西部的大部分区域;人类活动促使植被指数增加的区域占榆林总面积的54.96%,说明有一半以上的区域,人类活动对植被生长起到了促进作用,这些地区的封山育林、退耕还林、退牧还草等措施的实施效果较好。     

Firescape ecology: how topography determines the contrasting distribution of fire and rain forest in the south‐west of the Tasmanian Wilderness World Heritage Area

Aim To test the hypothesis that ‘islands’ of fire‐sensitive rain forest are restricted to topographic fire refugia and investigate the role of topography–fire interactions in fire‐mediated alternative stable state models. Location A vegetation mosaic of moorland, sclerophyll scrub, wet sclerophyll eucalypt forest and rain forest in the rugged, fire‐prone landscapes of south‐west Tasmania, Australia. Methods We used geospatial statistics to: (1) identify the topographic determinants of rain forest distribution on nutrient‐poor substrates, and (2) identify the vegetation and topographic variables that are important in controlling the spatial pattern of a series of very large fires (> 40,000 ha) that were mapped using Landsat Thematic Mapper (TM) satellite imagery. Results Rain forest was more likely to be found in valleys and on steep south‐facing slopes. Fires typically burned within highly flammable treeless moorland and stopped on boundaries with less flammable surrounding vegetation types such as wet sclerophyll forest and rain forest. Controlling for the effect of vegetation, fires were most likely to burn on flats, ridges and steep north‐facing slopes and least likely to burn in valleys and on steep south‐facing slopes. These results suggest an antagonism between fire and rain forest, in which rain forest preferentially occupies parts of the landscape where fire is least likely to burn. Main conclusions The distribution of rain forest on nutrient‐poor substrates was clearly related to parts of the landscape that are protected from fire (i.e. topographic fire refugia). The relative flammability of vegetation types at the landscape scale offers support to the proposed hierarchy of fire frequencies (moorland > scrub > wet sclerophyll > rain forest) that underpins the ecological models proposed for the region. The interaction between fire occurrence and a range of topographic variables suggests that topography plays an important role in mediating the fire–vegetation feedbacks thought to maintain vegetation mosaics in south‐west Tasmania. We suggest that these fire–topography interactions should be included in models of fire‐mediated alternative stable vegetation states in other fire‐prone landscapes.     

Approaches,levels and elements of vegetation research

The paper deals with the history of vegetation science viewed as a succession of paradigms. Alternative methodological approaches and alternative ways of viewing the elementary parts of vegetation at the coenotic level are replacing each other in the course of time. Vegetation research always involves a simplification of the vegetation objects by means of reduction and generalization. At any level there are certain traditional ways to describe the multiplicity of vegetation structure. According to the association approach, vegetation is mostly reduced to plant communities. The proponents of the continuum approach reduce the vegetation structure to the population level, and aggregate the populations in various ways. According to the ecosystem approach, various functional, more or less self-regulating vegetation elements can be described.