Two centuries of vegetation succession in an inland sand dune area,central Netherlands

Questions: (a) What are the rates and directions of vegetation succession in an inland sand‐dune system? (b) What are the differences in successional trajectories in different relief types? and (c) Is it possible to preserve the last areas of still active dunes and under what circumstances? Location: The study sites were located in the northern part of the Veluwe Region, central Netherlands; longitude 5°44′ E, latitude 52°20′ N, altitude 9 to 24 m a.s.l. Methods: Vegetation and relief mapping was conducted in three permanent plots, 200 m × 200 m in size, in 1988 and 2003. Phytosociological relevés (2400) were recorded in each 10 m × 10 m subplots. Age of woody species was determined by wood coring. Geographic Information System, ordination analyses, and TWINSPAN were used for data exploration and elaboration. Results: A total of 70 vascular plants and 19 bryophytes were recorded over successional stages spanning approximately190 years. The following dominant species formed the sequence of successional stages, but not all participated in all relief types: Ammophila arenaria, Festuca arenaria, Corynephorus canescens, Festuca ovina and Agrostis capillaris, and pine forest dominated in its herb layer at first by Deschampsia flexuosa and later by either Empetrum nigrum, Vaccinium myrtillus or Vaccinium vitis‐idaea. Conclusions: The successional trajectory is basically unidirectional for more than 100 years; no clear multiple successional pathways were observed, as is frequent in coastal dunes. Successional divergence was observed after approximately 130 years in the composition of the herb layer in the closed pine forest. The obvious vegetation heterogeneity in the still active sand‐blown area is related to differences in timing of vegetation establishment on particular relief types, thus the succession exhibits a terrain‐dependent asynchronous character. We conclude that the last patches of still‐active sand dunes can be preserved only by repeated strong artificial disturbances.     

Termitaria vs. mistletoe: Effects on soil properties and plant structure in a semi-arid savanna

Termite mounds by creating patches of increased resource availability (e.g. water and nutrients) are a major source of spatial heterogeneity in savannas. Likewise, mistletoes via input of nutrient-rich litter alter nutrient and water availability increasing environmental heterogeneity in semi-arid savanna. Despite this recognition, the influence of termitaria and mistletoe on soil properties and plant community have not been investigated together. We established eight 100 m² plots each on termitaria, under mistletoe-infected trees and in the surrounding savanna and examined the soil properties and the structure of Securinega virosa (Euphorbiaceae) and Euclea divinorum (Ebenaceae) in semi-arid savanna, southwest Zimbabwe. Soil properties significantly differed among the sampling sites (p = 0.001) with soils of increasing clay, soil moisture, pH and phosphorus, calcium and ammonium concentrations occurring on termite mounds. Soils under mistletoe-infected trees were associated with silt, organic matter, sodium, potassium, magnesium and nitrate and the surrounding savanna was associated with soils of increasing sand content. Plant structure also differed significantly between sites with greater basal area of both S. virosa and E. divinorum on termitaria relative to mistletoe-infected trees and the surrounding savanna. However, the stem density of S. virosa was greater under mistletoe-infected trees than on termitaria and in the surrounding savanna. Plant structural variables of individuals of the same species were affected by different soil properties across treatments. The major patterns showed that plant structure was influenced positively by soil moisture and nitrate and negatively by phosphorus on termitaria; positively by clay, soil moisture and ammonium and negatively by potassium under mistletoe-infected trees; and by phosphorus and calcium in the surrounding savanna. These findings show that soil properties, plant structure and their relationships differ between termitaria, mistletoe-infected trees and surrounding savanna, and these differences are suggested to increase heterogeneity in soil resources availability and vegetation structure in semi-arid savanna.     

Gradient structure of forest vegetation in the central Washington cascades

Summary Forest vegetation located in three areas of the central Washington Cascades, arrayed along a gradient of increasing continentality and decreasing rainfall, were compared using ordination methods. Within each region, lower and upper elevation sites were analyzed separately and for each set of sites, trees and ground story vegetation were analyzed independently. Principal components analysis, reciprocal averaging, weighted averaging, and polar ordination were applied to each set. The characteristics of the data determined which method gave the most readily interpretable results, but RA and WA usually best ordered the stands along a complex, combined coenocline, while PO often decomposed the gradient into moisture and temperature components. PCA was of little use, even with relatively low beta diversity.Results are presented in the form of stand by species tables for each data set and the most appropriate two dimensional ordination. Both are correlated to the classification. A mosaic diagram for each region is synthesized from these analyses and habitat data. These diagrams indicate that community types occupy a smaller portion of the habitat as continentality increases.The ordination results were in close agreement with our earlier classification of these stands. The maritime (west) region contains stands of low richness and with relatively little coenocline differentiation. In contrast, the continental (east) region has high alpha and beta diversity. Species in the west tend to occupy a broad portion of the available habitat range, while species in the east do not. The analyses reveal that ordinations by different strata may produce similar stand sequences if both strata are responding directly to the same factors, but that the correspondence degenerates where the understory responds primarily to the nature of the canopy dominant species. Thus stand sequence correlations are highest in the lowland eastern region and lowest in the lowland western region.This study demonstrates that none of these metric ordination methods is fool-proof and that none should be used exclusively or in isolation. RA and PO are demonstrated to be useful general methods; WA gave results similar to those of RA. PCA never produced uniquely superior results. Analyses with too few species and moderate beta diversity often produce distortions as pronounced as those with many species and high beta diversity.Nomenclature follows Hitchcock & Conquist (1973).Funds provided by the Graduate School Research Fund, University of Washington and by grants GB-20963 and GB-36810X to the Coniferous Forest Biome, U.S.I.B.P. This is contribution # 318 to the Coniferous Forest Biome. M.F. Denton, R.S. Fleming, A.R. Kruckeberg, and R.H. Whittaker each made significant suggestions. We thank R.S. Fleming, S.G. Fleming, C. Brewer, B.C. Cannon, K.E. Wade, K. Loughney, and J.E. Canfield for their assistance with field work and data analysis.     

贵州省普定县不同植被演替阶段的物种组成与群落结构特征

通过对贵州省普定县喀斯特地区不同植被演替阶段群落的调查, 研究了植被演替过程中群落物种组成和群落结构的变化。结果表明, 该地区的植被主要处于5个演替阶段, 即次生乔木林、乔灌过渡林、藤刺灌丛、稀灌草丛以及火烧干扰后的蕨类植物群落。本次调查共记录到植物365种, 隶属89科218属。其中, 蕨类植物31种, 隶属14科23属; 种子植物334种, 隶属75科195属。物种分布较多的科主要有蔷薇科、菊科、禾本科、百合科、忍冬科、唇形科、莎草科、樟科、葡萄科和水龙骨科。随着正向演替的推进, 物种丰富度增加, 群落结构趋于复杂化。藤刺灌丛与乔灌过渡林群落层次不明显, 次生乔木林分层明显。从藤刺灌丛向次生乔木林演替的过程中, 小径级个体所占比例明显降低, 高于1.3 m植物的总密度、乔木密度和藤本密度都先升高后降低, 而灌木密度呈逐渐降低的趋势。对喀斯特地区植被的恢复提出了参考措施。     

Dynamics of herbaceous vegetation recovery on Mount St. Helens,Washington, USA,after a volcanic eruption

Recovery of herbaceous vegetation on Mount St. Helens was studied annually after the massive lateral eruption of May 18, 1980. Measures such as species richness, cover, and diversity were combined with detrended correspondence analysis to describe vegetation recovery rates under different combinations of initial impact intensity and degree of isolation from recolonization sources. A major key to recovery is whether any plants survived the devastation. Survival of even a few individuals markedly accelerated recovery. Where no plants survived, the degree of isolation becomes paramount. New, barren substrates, a few meters from undisturbed sites, have begun to develop some vegetation, while more isolated sites have scarcely any subalpine plants present. On any site, plant-mediated processes that improve conditions for growth and the invasion of other species predominate in the early stages, but as vegetation develops, biotic inhibition and establishment of seedlings from adults already in the habitat gain importance. The rate at which this conversion occurs is a function of the size and intensity of the initial impact.Abbreviations DCA Detrended correspondence analysis     

繁殖期荒漠鸟类群落与自然植被的相关格局

为探讨植被结构和物种组成对鸟类群落多度分布的影响,于2010年5～8月,在阜康地区所涵盖的显域植被梯度带(梭梭、琵琶柴及蒿属荒漠)内分别布设3～4条样线,调查繁殖鸟类群落多度分布及植被参数.借助平均高度和盖度反映植被结构,平均物种数目反映植物组成.从鸟类群落中抽取显著正相关鸟种组合及狭分布鸟种组合,将不同的鸟类组合与植...     

Influence of grazing and soil conditions on secondary savanna vegetation in India

Abstract. Savanna vegetation and pertinent soil features were studied on 43 sites in a dry tropical forest region of India. Grazing intensity ranged from 0.68 to 0.98. Soil moisture was positively related to the proportion of fine soil particles (< 0.1 mm), and the latter decreased while the proportion of coarse particles (2.0-0.5 mm) increased with increasing grazing intensity. Canopy biomass ranged from 28 to 104 g/m² in grazed communities and from 230 to 337 g /m² in ungrazed communities and was positively related to vegetation cover which ranged between 30–72 % in grazed and 68 - 91 % in ungrazed communities. Vegetation cover was negatively related to grazing intensity. Species richness and diversity were highest at low grazing intensity. Using community coefficients and Detrended Correspondence Analysis, the grazed stands were clustered into six and the ungrazed ones into three communities. The grazed communities were recognised as degradation stages and the ungrazed ones as recovery stages. Only five grass species, in various combinations were able to dominate in one of the different stages. Evidently the harsh climatic conditions (high temperatures, high variability in rainfall and a long dry period) in the region permit only a few species already adapted to these conditions to participate in the succession.     

Temporal changes in species diversity and composition in abandoned fields in a <Emphasis Type="Italic">trans</Emphasis>-Himalayan landscape,Nepal

Secondary succession is an increasing phenomenon due to global changes in agriculture policies and practices. The empirical findings are biased towards the temperate zone. Abandonment of agriculture fields is less frequent in the subtropical and tropical zones where agriculture areas are, in general, expanding. But there are exceptions; a rapid rate of abandonment of agricultural fields have taken place in the arid trans-Himalayan region, due to today’s globalization of economy. We analysed agriculture fields that were abandoned between 1950 and 2003 in a large u-valley in central Nepal (3400 m a.s.l.). The potential forest vegetation is dominated by Pinus wallichina and shrubs of junipers and cotoneaster species. We tested the intermediate richness hypothesis in relation to vegetation cover, soil development and whether old-field succession is convergent or divergent with species data from 242 1 m² plots in 5 age-classes. The main species compositional turnover expressed by Detrended Correspondence Analyses (DCA) correlated, as expected, with time after abandonment. Fields that were abandoned a long time ago are closer to forest at the periphery of the agricultural landscape. Moisture of the soil significantly increased with age of abandonment, but total vegetation cover and pH were negatively related to age. Beta diversity expressed in DCA SD-units showed an increasing trend with age of abandonment, supporting the divergence pattern in old-field succession. The reason why the succession is not converging may be due to browsing by domestic animals that prevent a closed canopy of pines and juniper to develop. There was a significant hump-shaped pattern in species richness along the temporal gradient, which agrees with the intermediate species-richness hypothesis. There was a rapid increase in species richness in plots close to the villages that were used for haymaking which increased the seed input significantly.     

Analysis of the disintegrating group and gradient structure in Swiss riparian forests

The differentiation of river flood plain vegetation is predominantly determined by the inundation frequency and the type and age of the substrate. A comparison of data published in 1958 with recent relevés from all parts of Switzerland indicate that the hitherto known gradient- and group structure is disintegrating into multiple floristically isolated stands as a result of waterflow management constructions. In view of further vegetation mapping, a two-phase classification is proposed where the core of the gradients and groups is isolated and analysed first. The outliers are then re-attached to serve as possible indicators of the existence of variation not sufficiently described by the data. To structure the tedious analytical calculations involved, a hierarchical procedure has been developed.Abbreviations AOC = Analysis of concentration - CA = Correspondence analysis - PCA = Principal components analysis     

Dynamics of viable nitrifier community, N-mineralization and nitrification in seasonally dry tropical forests and savanna

The study was conducted in Vindhyan region, to assess the N-mineralization, nitrification and size of viable community of ammonium- and nitrite-oxidizing bacteria as affected by different sites and seasons. Six different ecosystems (four forests and two savannas), which differ in terms of topography, vegetation and moisture status, were selected for the present study. The soils of the study sites differ significantly in its physico-chemical properties. The savanna site had significantly higher pH (7.2), bulk density (1.37 g cm(-3)) and silt content (67.80%) but lower water holding capacity (1.37%), total-C (16,356 microg g(-1) dry soil), N (1090 microg g(-1) dry soil) and P (213 microg g(-1) dry soil) than forest sites. The soil moisture content, N-mineralization, nitrification rates and numbers of ammonium- and nitrite-oxidizing bacteria were highest in the wet season and lowest in dry season, while the size of mineral-N (NH4(+)-N and NO3(-)-N) showed a reverse trend at the sites. The N-mineralization, nitrification and nitrifier population size differ significantly across the site and season. The numbers of free-living cells of ammonium- and nitrite-oxidizing bacteria were significantly related to each other and to N-mineralization, nitrification, soil moisture and mineral-N components. The N-mineralization, nitrification and the viable number of nitrifying cells were consistently higher for forest soils compared to savanna sites. It was concluded that soil microbial process (N-mineralization and nitrification) and nitrifier population size were dependent on site topography, vegetation cover and soil moisture status.     

Seed bank and vegetation composition of forest stands of varying age in central Belgium: consequences for regeneration of ancient forest vegetation

Vegetation composition differs significantly between ancientand recent forest, due to slow colonization capacity of typical forest speciesand the higher abundance of early successional species in recent forest.However, little is known about differences in persistent seed bank compositionbetween ancient and recent forest and about the interaction between seed bankand vegetation in relation with forest age. We surveyed the seed bank and theunderstorey vegetationcomposition in transects from ancient to recent forest. Seed bank and fieldlayer vegetation characteristics and similarity between seed bank andvegetationwere analysed in relation to recent forest age and distance to the ancientforest. A total of 39 species and 14,911 seedlings germinated, whichcorresponds with a seed density of 12,426 seeds/m².Total seed density is significantly higher in the youngest recent forest parcel(55 years). Also the seed bank composition in the youngest forest parceldifferssignificantly from the other parcels. After a longer period of reforestation,the seed bank approaches that of the ancient forest, suggesting seed bankdepletion, although the seed bank is permanently replenished to some extent byseed bank forming species from local disturbances. Seed bank composition doesnot change significantly with distance to the ancient forest. Similaritybetween seed bank and vegetation composition, nomatter the forest age, is very low, but decreases with increasing forest age.The most frequent species in the vegetation are absent in the seed bank andvice versa. The contribution of forest species is highin the vegetation and they almost not occur in the seed bank, while species offorest edges and clearings, and species of disturbed environments are morefrequent in the seed bank. The seed bank is mainly composed of earlysuccessional species of former forest stages or species which temporary occurinsmall-scale disturbances. The seed bank may enhance the negative effects ofearlysuccessional, mainly competitive species to the forest species richness in therecent forest. In this respect, forest management should minimise forestdisturbances, to prevent germination of competitive species form buriedseeds.     

Long-term change in the floristic composition and vegetation structure of Carnac Island, Western Australia

Aim To document changes in the floristic composition and vegetation structure of Carnac Island during a period of 40 years. This paper presents a synthesis of all available floristic and vegetational information. Location Carnac Island is 8 km offshore from Fremantle, south‐west Western Australia. Methods Comparison of lists of plant species for 1951, 1958/9, 1966/7, 1975/6 and 1995–6. Comparison of vegetation, based on structural and floristic elements, for 1951, 1965, 1972, 1984 and 1995. Results Floristic composition (both native and exotic species) changed most dramatically in the period 1975/6–1995/6, with a 37% reduction in number of plant species. The number of annual and perennial native species present in 1995/6 was most similar to that in 1951. The most remarkable change in the flora has been the increase in annual exotic species since 1951. Immigration and extinction rates were greatest in the periods 1951–58/9 and 1958/9–1966/7, respectively. Vegetation structure has also altered, involving a reduction in height of dominant species from 3–4 m to 1 m as Acacia rostellifera and Olearia axillaris have declined in distribution. The weed species Mesembryanthemum crystallinum (first recorded 1975) and Malva parviflora (1958) now dominate the vegetation of half the island. Main conclusions Five factors are considered to have contributed to botanical change: nesting seabird populations, eradication of the rabbit in 1969, drought, increased saltload from occasional cyclones in summer or autumn, and competition from increasing dominance of several weed species. Several of these factors have operated in opposing ways with respect to plant species richness and vegetation cover. Experimental studies are required to determine the strength of these interactions. Two weed species, Zantedeschia aethiopica (first recorded 1966) and Lycium ferocissimum (1992) have the potential to dominate the vegetation of the island.     

Topo-edaphic, floristic and physiognomic gradients of woody plants in a semi-arid African savanna woodland

The variation in topo-edaphic conditions, woodland composition and physiognomic structure of a semi-arid savanna woodland, namely the 59 400 ha Klaserie Nature Reserve, was studied with multivariate techniques. Spatial variation in the texture and chemistry of both the A-and B-horizons was substantial. One gradient of the A-horizon was of increasing clay, silt, organic matter, pH and conductivity, while a second gradient was of increasing rockiness, slope and gravel content, associated in part with upper landscape positions. Physiognomic structure of the woodland also displayed substantial spatial variation. Variation in tree density had the greatest effect on total canopy volume, and the density of coppice and dead individuals were closely correlated. Topo-edaphic variation, after the effect of vegetation composition had been accounted for, had a direct effect on woodland structure, as clay content of soils or rockiness influenced shrub density, and catenal position together with silt-or gravel-content of soils influenced coppice density. Ordination analyses identified that the included topo-edaphic variables accounted for a significant amount of floristic variation, but also showed that important environmental variables were omitted. Floristic variation of woody elements was of the nature of a large number of relatively equivalent, independent gradients rather than of a few simple primary gradients. Ten woodland types were identified by TWINSPAN which differed in their topo-edaphic and physiognomic character. Distinctive woodland assemblages were found on rocky outcrops or alluvial areas, on deep, sandy soils or on clay-or silt-rich soils. Colophospermum mopane formed the densest woodlands. Characteristics of the B-horizon were often dissimilar to those of the A-horizon, and seemed important for woodland composition.     

亚热带稻田弃耕湿地土壤因子对植物群落结构的影响

采用冗余分析法对弃耕一年稻田湿地生态系统的植物群落与土壤因子进行了分析.结果表明：在亚热带湿地生态系统中,土壤水分条件、有效钾、有效磷和pH是影响物种分布的最主要土壤因子.试验区的主要植物物种可以划分为3个物种组:丁香蓼-水竹叶物种组(组1)、牛鞭草-圆叶节节菜-稻槎菜物种组(组2)和小白酒草-辣蓼-双穗雀稗物种组(组3).其中,组1主要分布于土壤有效钾含量较高的区域;组2主要分布于阶段性淹水区域;组3主要分布于排水区域,且与土壤有效磷和pH呈正相关.物种多样性与土壤pH、植被地上生物量与土壤全钾含量呈显著正相关,均匀度与土壤有效氮含量呈显著负相关,与其他指标的相关性均不显著.     

Plant community structure in relation to grazing and environmental changes along a north-south transect in the western Kalahari

Sixteen vegetation types were described from a north-south transect in the western Kalahari. Pronounced differences were found between communities on the nutrient poor red Kalahari sand, covering most of the area and those on fine soils and white calcareous sand. Syntaxa resulting from severe overgrazing by livestock were in most cases clearly distinguished from the less disturbed vegetation. The communities on red sand consisted mainly of shrub savanna dominated by perennial tufted grasses, whereas in the vegetation on calcareous material and on overgrazed land, forbs, dwarf shrubs and shrubs played a more important role. The major communities on red sand showed a clear geographical zonation roughly corresponding to the gradient in mean annual rainfall and its interannual variation. In the northern and central Kalahari these syntaxa were dominated by species of Sudano-Zambezian origin and in the southern Kalahari by species showing Karoo-Namib affinities.     

Altitudinal changes in composition and structure of mountain-temperate vegetation: a case study from the Western Carpathians

Changes in composition and structure of plant communities in relation tothe soil and snow cover variation were analyzed along an altitudinal transect(1150–1750 m) from the mountain-temperate forests to a woodyshrub community and alpine meadows on Mt Velký Gápel', Slovakia.The soils below the treeline (1510 m) had a more developedorganic layer above the mineral substratum. Generally, soil depth decreased asthe altitude increased, although the maximum values were recognized at a middlealtitude in a beech stand. Snow was redistributed by westerly winds from theridgeline down to the upper forest margin. Mean snow depth decreased withaltitude up to almost snow-free sites around the summit. In the 48 plots at 16sites we recorded 118 taxa including 6 tree, 7 shrub, 18 grass, 42 herb, 5fern,25 moss and 15 lichen species. The species diversity showed no distinctrelationship to altitude but declined with canopy consolidation. The TWINSPANfloristic classification distinguished five groups of community typescharacterised by different dominants, and a further three clusters of samplesfrom transition zones. Horizontal compositional heterogeneity increased inareaswhere trees were aggregated and tree basal area was smaller. Vegetationcomposition became more patchy at open-canopy Acerpseudoplatanus–Abies alba mixed forest at 1150 m,in Picea abies forest limit 1470 m, andin Pinus mugo krummholz at 1590 m. Speciesturnover of the entire transect was 6.1 half-changes as estimated by DCA.Despite this heterogeneity, none of the 15 elevational bands had significantaggregation of species' limits. Vegetation varied continuously, with individualspecies overlapping in transition zones delimited by dominant taxa. Thecoincident aggregation of up-slope and down-slope boundaries was found at abelt1430–1510 m. This discrete ecotone corresponds to a shiftfrom the closed coniferous forest to P. mugo krummholz.Thesecond inherent up-slope boundary aggregation indicated the P.mugo krummholz – alpine meadow vegetation transition at1700 m. Spatial analysis (K-function) of eight forest plots(0.12 ha each) showed that at lower elevation, adult trees of thebroad-leaf forest were closer to a random arrangement while at higherelevation,trees of evergreen coniferous stands became aggregated toward the forest limitwith the highest intensity from 2 to 4 m. Altitudinal gradient andrelated factors explained 35% of the variance in vegetation data.Canonical correspondence analysis also showed that main vegetation changesabovethe treeline area were associated with the topographic pattern of pine shrubsand snow cover.     

Epiphytic vegetation on pollarded trunks of Fraxinus excelsior in four different habitats at Grinde,Leikanger, western Norway

The epiphytic vegetation on 24 pollarded trees of Fraxinus excelsior at the farm Grinde, Leikanger, western Norway was investigated. Each trunk was divided into a basal zone, a middle zone and a top zone. In each zone the four different aspects were analysed (12 sampling units from each trunk). Within a total of 276 sampling units, 162 taxa were recorded (99 lichens, 56 bryophytes, 7 vascular plants). The trunks were covered mainly by an old, thick and occasionally swollen bark, but decaying wood did not occur. Their habitats were different, and each trunk was classified into one of four categories: open meadow, wooded hay meadow, deciduous wood, and spruce plantation. A climate station was established in each habitat to measure important parameters. The floristic and environmental data were analysed by canonical correspondence analysis (CCA). The floristic data were classified into eight TWINSPAN groups that have been taken into account in the CCA diagrams. At Grinde all the pollarded trunks grew under fairly homogeneous conditions during a more extensive agricultural period until about 1962. The deciduous wood developed by tree colonization on old meadows and wooded hay meadows, whilst spruce has been planted in a small part of the area. Floristic differences in the epiphytic vegetation between the four different habitats were found, which suggests that changes in the vegetation have developed during the last two or three decades. The spruce plantation was the most shady habitat having a very sparse epiphytic vegetation, mainly remnants from vegetation established during more open area conditions.