Detrended Correspondence Analysis Ordination Research Articles

Alnus glutinosa Riparian Woodlands of Italy and Corsica: Phytosociological Classification and Floristic Diversity

A comparative analysis of the riparian vegetation dominated by Alnus glutinosa in Italy and Tyrrhenian islands, based on literature data and unpublished relevés, is presented. A total of 456 phytosociological relevés were processed. For the definition of plant communities and alliances, hierarchical clustering was performed by using Bray-Curtis coefficient and Detrended Correspondence Analysis ordination methods. Identification of diagnostic species of the vegetation units was performed by means of the phi fidelity index. Quantum GIS software version 3.6 was used for the interpolation of the bioclimatic variables and A. glutinosa communities. Overall, a total of 18 A. glutinosa-riparian wood communities were distinguished for Italy and Tyrrhenian islands, of which two new associations and one new subassassociation are described. The classification of the relevés showed two main vegetation groups: the first one including the plant communities of the Osmundo-Alnion alliance, and the other including the vegetation of the Ligustro vulgaris-Alnion glutinosae alliance. This latest includes the riparian meso-thermophilous communities of central and northern Italy. Within the Osmundo-Alnion alliance, two subgroups can be recognized: the first one includes the thermophilous communities of the Hyperico hircini-Alnenion glutinosae sub-alliance, mainly spread in the Tyrrhenian islands, while the second group includes the mesophilous communities attributed to the new suballiance Struthioptero-Alnenion glutinosae, widespread in central Italy and the Corsican mountains. The present paper provides the first comprehensive and exhaustive scheme of the A. glutinosa riparian woodlands diversity in Italy and Corsica.

Relationship between species distribution of sandy alpine grasslands and microtopography in the source regions of Yangtze river

Dynamic of sandy alpine grasslands affect the progress and reversal of desertification in source regions of the Yangtse Rivers. To understand geomorphic driving mechanism of species distribution pattern, we examined the species compositions and delineated the most important landform factors influencing species distribution of sandy alpine grassland using two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA). Field survey were conducted in summer of 2016 using stratified random methods in hilly sloped lands, floodplains, foothills, and valley land of study region. In total, 29 plant species grouped into 27 genera and 16 families were identified. Leymus secalinus, Elymus dahuricus and Corispermum declinatum are the dominant species of sandy alpine grassland communities in different microtopography. The present vegetation reflected xerosere character, which indicated that desertification of alpine grassland is in progress. Standard frequency distribution of species varied with different microtopography, the proportion of dominant species was generally lower than rare species, and the vegetation community was in a highly successional stage. Seven groups were distinguished through TWINSPAN, distribution of which in the DCA ordination graph showed species with similar ecotype is clustered together. The results of the CCA ordination revealed that slope and aspect are the dominant factors among microtopography determining the species distribution of sandy alpine grassland.

Living on the edge: Plant diversity in the Iberian chionophilous vegetation

AbstractAimsChionophilous vegetation (i.e. snowbed vegetation and chionophilous grasslands) hosts relict arctic–alpine species, among which snowbed specialists, that find their southernmost limit in the Iberian Peninsula, where they are especially threatened by climate change. Our aims were to identify the main Iberian chionophilous vegetation groups, and analyse their plant diversity patterns and their role as refugia for snowbed glacial relicts, as well as that of Iberian high‐mountain regions.LocationIberian high mountains.MethodsWe used thebeta‐flexibleclustering method to classify 1002 vegetation relevés of Iberian chionophilous vegetation, and computed species Indicator Values and frequencies for the resulting groups. We performed a Detrended Correspondence Analysis (DCA) ordination of the relevés, and fitted six climatic variables to reveal the main ecological gradients. We constructed rarefaction curves to compare species richness between vegetation groups and between mountain regions.ResultsWe obtained eight vegetation groups, four consisting of snowbed vegetation and four of chionophilous grasslands. All but one group were present in the Pyrenees, where snowbed specialist richness was the highest. In southern and central Iberian ranges, snowbed vegetation was extremely scarce, and the main vegetation group corresponded to cryoromediterranean grasslands, where both species and specialist richness were the lowest. Snowbed and northern Iberian grassland groups accounted for similar high specialist richness, although specialists were infrequent and scarce at relevé level in these grasslands.ConclusionsDespite the set of specialised species that thrive in snowbeds, many of them are also present but scarce in northern Iberian chionophilous grasslands. In a future scenario with a high reduction of snow cover duration, which may entail the disappearance of many snowbed vegetation patches, northern Iberian chionophilous grasslands may act as terminal refugia for snowbed specialists. Nevertheless, specialists are very threatened in central and southern Iberian ranges, where snowbed vegetation is infrequent and chionophilous grasslands provide almost no shelter to them.

Silicicolous lichen communities of the Ukrainian Crystalline Shield

AbstractQuestionsHow many different silicicolous lichen syntaxa occur on the Ukrainian Crystalline Shield and what ecological factors are influencing their distribution?LocationUkrainian Crystalline Shield, Steppe and Forest–Steppe zones, Ukraine.MethodsThe field research was performed during 2013–2020. Analysis was done with the JUICE software using agglomerative hierarchical cluster analysis in the integrated PC‐Ord with data transformation, pseudospecies cut levels 0–5–25, distance measure – Jaccard, group linkage – Ward's method. For the ordination of the plots we used detrended correspondence analysis (DCA) and non‐metric multidimensional scaling (NMDS) with the “envfit” function, implemented in the R package vegan. As environmental variables we used mean indicator values obtained for each species from the ITALIC database. A generalized synoptic table, which combined both our own and literature data, was clustered using Euclidean distances and the Ward error sum of squares hierarchical clustering method with Ward's criterion.ResultsSeven clusters were obtained after JUICE analysis based on 197 relevés of lichen communities that included 119 lichen species. The main axis in both DCA and NMDS ordination is similar to the vector of substrate pH value. Communities on overhanging surfaces are acidophilous. Communities of water tracks are moderately basophilous to basophilous. Other communities included relevés on different granite characterized as mainly neutrophilous. Lichen communities on siliceous rocks of the Ukrainian Crystalline Shield are assigned to the classes Rhizocarpetea geographici, Leprarietea chlorinae, and Collematetea cristati. Two new alliances (Aspicilion intermutantis and Staurothelion frustulentae), four new associations and three subassociation are described.ConclusionSilicicolous lichen communities of the Ukrainian Crystalline Shield differ from the known units of Central Europe by species composition, where lichens with arid ecology are present. Their local distribution depends mainly on a combination of substrate pH, degree of eutrophication, protection from rain, and substrate moisture.

The effect of siliceous sponge deposition on Permian paleocommunity structure

AbstractA dramatic shift from carbonate-rich to chert-rich marine strata occurred during the Permian and is frequently attributed to the increased activity of siliceous sponges and their biosiliceous sedimentation. The first-order ecologic consequences of this transition, if any, remain opaque. We analyze fossil occurrence data from the Phosphoria Basin (western North America) to test whether the presence of siliceous sponges, which are correlated with basin-wide chert strata, influenced the recruitment of benthic fauna. Using published lithologic descriptions, we categorized fossil collections by formation, facies, and lithology and used these data to code detrended correspondence analysis and nonmetric multidimensional scaling ordinations. We also analyzed the clustering of taxa into faunal units termed biofacies.Results from these analyses indicate that fossil collections occurring in chert and carbonate are closely associated in faunal composition and community structure. These collections preferentially occur in the inner- to mid-ramp facies, in agreement with previous studies. Although largely similar in composition, collections of chert and carbonate lithology exhibit differences in the frequency and abundance of accessory brachiopod taxa (e.g., Composita and Hustedia), possibly a result of greater biosiliceous sedimentary input.

Holocene heathland development in temperate oceanic Southern Hemisphere: Key drivers in a global context

AbstractAimUnderstanding long‐term heathland development is key in mitigating their current attrition globally. However, such knowledge is limited in Australia and the wider Southern Hemisphere. We aim to identify potential climatic and environmental drivers of Holocene heathland development in temperate‐oceanic Australia (Bass Strait), and also assess the applicability of Iversen's conceptual model of interglacial vegetation development to the area.LocationBass Strait, southeast Australia.TaxonMonotoca, Epacris, Sprengelia and Restionaceae.MethodsWe used multiple sedimentary pollen and charcoal records from truwana/Cape Barren Island (CBI) in Bass Strait to reconstruct vegetation and fire history. We also used rarefaction analysis on pollen records to estimate floristic richness for all sites, and magnetic susceptibility and organic content were derived for two of the four sites as proxies for local sedimentary changes. Reconstructed vegetation and fire histories were then compared to independent records of climate and sea‐level change in temperate Australia, using a Detrended Correspondence Analysis ordination, to identify major drivers of heathland development.ResultsMajor heathland expansion occurred on truwana/CBI between the early and mid‐Holocene in response to sea‐level rise, high effective precipitation, reduced seasonality and increased Indigenous burning. Increasing seasonality, low effective precipitation, El Niño‐Southern Oscillation intensification, stable sea level, and decreased fire activity drove the expansion of scrub and woodland at the expense of heathland in the late Holocene. The overall vegetation development on truwana/CBI fits poorly with the classic Iversen conceptual model of interglacial vegetation development in the Northern Hemisphere, due to the significant role of interglacial sea‐level rise on truwana/CBI. Therefore, a modified model, which takes into account the role of sea‐level change, is proposed for Southern Hemisphere‐temperate‐oceanic settings.Main conclusionsHeathland developments in both hemispheres reflect some level of homogeneity, considering the roles of increased Indigenous burning and reduced seasonality in both hemispheres. Frequent, controlled burning strategies are recommended to maintain heathland on truwana/CBI.

Coastal saltmarsh vegetation in Sicily (Italy): phytosociological insights and plant diversity

This paper reports a phytosociological survey on the perennial halophilous vegetation of the coastal salt marshes in Sicily. Data available from the literature have been supplemented with original relevés performed in different salt marshes in Sicily. A total of 470 relevés according to the standard procedures of the Braun-Blanquet method were processed. For the definition of plant communities and alliances, hierarchical clustering was performed by using Bray-Curtis coefficient and Detrended Correspondence Analysis ordination methods. The Salicornietea fruticosae class is represented in Sicily by two, floristically and ecologically well differentiated, orders: Salicornietalia fruticosae, including seven alliances (Arthrocnemion macrostachyi, Inulion crithmoides, Limoniastrion monopetali, Limonion ferulacei, Salicornion fruticosae, Sarcocornion alpinii, Suaedion verae), and Halocnemetalia cruciati, including only one alliance (Halocnemion cruciati). Within this class, 12 plant associations were recognized, of which a new association (Junco subulati-Limonietum narbonense), included in the Salicornion fruticosae alliance.

Surface pollen distribution in alpine zone of the higher Himalaya: a case study from the Kalla glacier valley, India

ABSTRACT In order to understand the relationship between modern pollen spectra and vegetation, we analysed 20 surface sediment samples collected from the alpine zone of Kalla Bank glacier valley, Dhauliganga Basin, India covering an elevational stretch of c. 3600 to 5000 m asl and vegetation zones like the alpine scrub, alpine meadow and alpine barren. This study also provides insights into the vertical pollen transport along the elevational gradient of the glacier valley. Numerical analyses such as cluster analysis (CA), discriminant analysis (DA) and detrended correspondence analysis (DCA) are used to explore and discuss the modern pollen deposition patterns in the alpine settings. Despite the inconsistencies observed between modern vegetation and surface palynoassemblages, a good agreement is noticed between CA and DA classifications and DCA ordination results which reveal signature of upslope wind transport. High percentages of pine, cedar, alder and birch pollen grains in the above tree-line surface pollen assemblages are indicative of their upslope wind transport from a lower elevation. The inconsistencies may be attributed to the differential pollen representation between species, differential flowering and pollination of herbaceous taxa. The present study suggests altitude and monsoonal winds might be the two most influential factors that attributed changes in the surface palynoassemblages of the alpine vegetation in the Kalla Bank glacier (Kunti-Banar) valley. Therefore, while interpreting the fossil pollen spectra from any high altitude mountainous zone, long-distance pollen transport should always be taken into account, especially for anemophilous plant taxa.

Floristic Variation of Tree Communities In Island Forests of Pulau Tuba and Gunung Raya Forest Reserve, Langkawi

Island forests are among forest habitats that are vulnerable to natural and anthropogenic disturbances, whereby the disturbances would influence the survival of biological species of the ecosystems. Langkawi Archipelago contains many small island forests and rapid development of tourism industry within this archipelago might contribute impacts to the tree flora of the forest communities on the small islands. Hence, in this study the species richness and floristic variation pattern of tree communities of two selected island forests in the Langkawi Archipelago were explored, and data gathered are anticipated to be used for management of island forests in Langkawi. Tree survey was carried out in 10 study plots of 20m x 25m each, at island forests of Pulau Tuba Forest Reserve (PTB) and Gunung Raya Forest Reserve (GRFR), making the total of 20 study plots. All trees with diameter at breast height (dbh) of 5.0 cm and above were enumerated and tree species were identified. Species data were analyzed for diversity and richness using the Shannon and Margalef indices; whilst Detrended Correspondence Analysis (DCA) was used to determine floristic pattern. A total of 1062 trees were recorded from all study plots which comprised of 49 families, 134 genera and 213 tree species. The GRFR exhibited the highest species number of 135 tree species, followed by the PTB (106 tree species). Species accumulation curves showed that the curves were far from reaching the asymptote even when the whole dataset were combined. The DCA ordination diagram clearly grouped the study plots by their geological formation that indicated a gradient of species change in GRFR and PTB sites.

Desert vegetation distribution and species-environment relationships in an oasis-desert ecotone of northwestern China

Environmental heterogeneity significantly affects the structure of ecological communities. Exploring vegetation distribution and its relationship with environmental factors is essential to understanding the abiotic mechanism(s) driving vegetation succession, especially in the ecologically fragile areas. In this study, based on the quantitative analysis of plant community and environmental factors in 68 plots at 10 different transects in the Minqin oasis-desert ecotone (ODE) of northwestern China, we investigated desert vegetation distribution and species-environment relationships using multivariate analysis. Two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA) methods were used. A total of 28 species, belonging to 27 genera in 8 families, were identified. Chenopodiaceae, Zygophyllaceae, Gramineae, and Leguminosae were the largest families. Annual and perennial herbs accounted for 28.60% of the total number of plants, while shrubs (42.90%) were the most dominant. Nitraria tangutorum was the constructive species of the desert plant community. We divided the 68 plots surveyed in this study into 7 community types, according to the results of TWINSPAN. The distribution of these 7 communities in the DCA ordination graph showed that species with a similar ecotype were clustered together. Results of CCA indicated that groundwater was the dominant factor influencing vegetation distribution, while distance between plot and oasis (Dis) and soil electrical conductivity (EC) were the local second-order factors. Our study suggests that optimizing the utilization of groundwater in oases is key to controlling the degradation of desert vegetation. The favorable topographic conditions of sand dunes should be fully utilized for vegetal dune stabilization, and the influence of soil salinity on the selection of afforestation tree species should be considered.

Land-use impacts on the composition and diversity of the Baikiaea– Guibourtia–Pterocarpus woodlands of north-western Zimbabwe

Variation in floristic composition of recovering Baikiaea–Guibourtia–Pterocarpus woodlands was studied in different development stages (from early regrowth to mature woodland) under different land-use systems (protected areas, timber harvesting, pole and firewood collection, and abandoned crop fields), in the Gwayi and Tsholotsho areas in north-western Zimbabwe. A total of 150 nested circular plots were sampled representatively in four different development stages related to the land-use systems. The DBH (stem diameter at 1.3 m above ground level) and tree height were recorded by species for all stems of tree species with DBH ≥ 15 cm in a 30-m-radius plot (0.283 ha) and for trees with DBH 5.0–14.9 cm in a 11.3-m-radius plot (0.04 ha) (both centred around the same midpoint). Stems with DBH < 5 cm were counted by species in an inner sub-plot of 5.65 m (0.01 ha) radius. Tree data (stem DBH ≥ 5 cm) and regeneration data (stem DBH < 5 cm) by stem counts per species per plot, were used separately to run TWINSPAN (TWo-way INdicator SPecies ANalysis) classifications of species assemblages. Importance values were calculated for all tree species per community. Shannon–Wiener diversity indices were calculated for each community and tested for differences using one-way ANOVA in SPSS version 21. Detrended correspondence analysis (DCA) implemented in the CANOCO ordination software was used to determine the extent of variation amongst the identified communities. The classification identified 12 tree communities and 13 regeneration communities, clustering plots from different land uses together. Baikiaea plurijuga was the most important tree species in all tree communities, except where Combretum collinum, C. apiculatum, Commiphora mossambicensis and Pterocarpus angolensis were dominant. Pterocarpus angolensis showed low importance in most communities, except for communities from undisturbed sites (mostly mature trees) and abandoned fields (mostly young trees). Baikiaea plurijuga was most important in most regeneration communities, except in communities dominated by Baphia massaiensis, C. collinum, C. apiculatum and P. angolensis. Species diversity differed significantly (p < 0.05) amongst tree communities. The DCA ordination showed little variation amongst the communities. The cumulative contribution of environmental factors explaining variation in species composition was 22.6% for tree communities and 26.1% for regeneration communities, suggesting that recovery from disturbance after different land uses may explain more of such variation.

新疆博格达山岩面生地衣群落结构特征

根据对新疆博格达山岩面生地衣群落20个样点（20m×20m）调查的数据，以各地衣种的盖度为指标结合双向指示种分析方法（TWINSPAN）和除趋势对应分析法（DCA）对博格达山岩面生地衣群落进行数量分类并分析了群落结构特征及其多样性和相似性。采用典范对应分析法（CCA）对各群落的物种分布格局与环境因子的关系进行研究。结果表明，TWINSPAN分析和DCA排序将分布在博格达山的37种岩面生地衣分为以下5个群丛。群丛1：斑纹网衣（Lecidea tessellate Florke）+粉芽盾衣（Peltula euploca（Ach.）Poelt）+杜瑞氏黄梅（Xanthoparmelia durietzii Hale）群丛，有25个种，总覆盖度为30.145%，多样性为4.025；群丛2：袋衣（Hypogymnia physodes（L.）Nyl.）+白边平茶渍（Aspicilia sublaqueata（H.Magn.）J.C.Wei）+砖孢胶衣（Collema subconveniens Nyl.）群丛，有17个种，地衣总盖度为15.885%，多样性为3.196；群丛3：聚茶渍（Lecanora accumulate H.Magn.）+丽石黄衣（Xanthoria elegans（Link）Th.Fr.）+亚洲平茶渍（Aspicilia asiatica（H.Magn.）Yoshim.）群丛，有30个种，地衣总盖度为37.87%，多样性为4.357；群丛4：中华石果衣（Endocarpon sinense H.Magn.）+伴藓大孢蜈蚣衣（Physconia muscigena（Ach.）Poelt.）+垫脐鳞衣（Rhizoplaca melanophthalma（DC.）Leuckert&Poelt）群丛，有24个种，地衣总盖度为30.458%，多样性为3.912；群丛5：石胶衣（Collema flaccidum（Ach.）Ach.）+短绒皮果衣（Dermatocarpon vellereum Zschacke）+绿黑地图衣（Rhizocarpon viridiatrum（Wulfen）Korber.）群丛，有18个种，地衣总盖度为19.331%，多样性为3.515。CCA排序结果反映，该地区岩面生地衣的分布与海拔高度、光照强度、岩石pH和人为干扰有关，其中影响最大的因素是海拔高度，其次为光照强度和干扰。坡向和岩石大小对地衣种类分布的影响不显著。;In this investigation of saxicolous lichen communities in the Bogda Mountains using 20 quadrats (20m×20m), the data were classified based on species coverage using two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis (DCA). Community structure characteristics, species diversity, and similarity index were analyzed. The relationship between species distribution of saxicolous lichens and six different environmental factors was examined by canonical correspondence analysis (CCA). The results showed that the saxicolous lichen community can be divided into five associations according to the TWINSPAN analysis and DCA ordination:Association 1 (Lecidea tessellata Florke+Peltula euploca (Ach.) Poelt+Xanthoparmelia durietzii Hale), including 25 species with the total coverage of 30.145% and diversity of 4.025; Association 2 (Hypogymnia physodes (L.) Nyl. +Aspicilia sublaqueata (H. Magn.) J. C. Wei+Collema subconveniens Nyl.), including 17 species with the total coverage of 15.885% and diversity of 3.196; Association 3 (Lecanora accumulata H. Magn. +Xanthoria elegans (Link) Th. Fr. +Aspicilia asiatica (H. Magn.) Yoshim.), including 30 species with the total coverage of 37.87% and diversity of 4.357; Association 4 (Endocarpon sinense H. Magn. +Physconia muscigena (Ach.) Poelt. +Rhizoplaca melanophthalma (DC.) Leuckert & Poelt), including 24 species with the total coverage of 30.458% and diversity of 3.912; and Association 5 (Collema flaccidum (Ach.) Ach. +Dermatocarpon vellereum Zschacke+Rhizocarpon viridiatrum (Wulfen) Korber.), including 18 species with the total coverage of 19.331% and diversity of 3.515. The CCA ordination results showed that the species composition and distribution pattern of saxicolous lichens were most strongly influenced by altitude, then light intensity, rock pH, and human disturbance; the distribution pattern of the lichen communities did not significantly correlate with aspect and rock size.

Effect of altitudinal gradients on forest structure and composition on ridge tops in Garhwal Himalaya

Ridge top ecosystems (RTEs) are considered to be more sensitive to global warming as they are characterized by uniform sunlight exposure and low human interferences and hence are perfect places for monitoring and comparing the effects of climate change in species composition. The present study was carried out on RTEs of four different mountain ranges, viz. (1) Narendranagar–Hindolakhal (2) Mussoorie–Dhanolti (3) Chaurangikhal–Harunta and (4) Dayara–Gidara, along altitudinal gradient (situated below 2000 to above 3500 m), in Garhwal Himalaya to understand the variation in tree composition and distribution range. 0.1 ha-sized sample plot was used to analyze the tree species, whereas 5 m × 5 m for saplings and 1 m × 1 m for seedlings. The tree layers on RTEs were consisted of total 69 tree species, belonging to 55 genera and 39 families. Shorea robusta, Pinus roxburghii, Rhododendron arboreum, Quercus leucotrichophora, Q. floribunda, Q. semecarpifolia, Cedrus deodara, Pinus wallichiana and Abies spectabilis were found as the dominant and well-occupied tree species on the RTEs from lower to higher elevations. The mean stand density was recorded as 597 ± 29 trees ha−1 (ranged between 546 and 616 trees ha−1) with a mean basal cover of 77.25 ± 17.90 m2 ha−1 (ranged between 54.43 and 102.83 m2 ha−1). A traditional pattern for tree diversity was recorded which decreased with increasing altitude. The detrended correspondence analysis ordination plot clumped the species together which shared the same habitat and environmental conditions which revealed that elevation and geographic location were the dominant factors for regional differences in species composition among RTEs.

A classification of the geothermal vegetation of the Taupō Volcanic Zone, New Zealand

ABSTRACTWe undertook stratified random sampling of vegetation, soil chemical fertility and subsurface soil temperature at 38 sites on 15 geothermal fields in the Taupō Volcanic Zone, central North Island, New Zealand, to develop a quantitative classification of geothermal vegetation types and to identify the main environmental drivers of vegetation composition. We implemented this with the fuzzy classification framework of noise clustering. Gradients in composition were derived using Detrended Correspondence Analysis ordination and related to soil physical and chemical parameters using correlation. Of 166 plant species recorded, only seven native species were present in > 20% of plots and only four adventive species in > 5% of plots. Subsurface soil temperatures ranged from ambient (7 °C) to near-boiling (98.5 °C). Classification identified 16 vegetation associations, almost all dominated by indigenous species and unique to geothermal fields. Subsurface soil temperature was the main factor controlling vegetation composition; soil chemistry was less important.

Effect of black walnut (Juglans nigra) on the understorey vegetation - a case study of South Moravian forests (Czech Republic)

The article analyses the influence of black walnut on forest phytocoenosis in South Moravian forests and assesses how its representation may affect the understorey vegetation of the forest ecosystems. In July 2014, 31 relevés were processed in the South Moravian forests. These were stands of pure black walnut (Juglans nigra) as well as black walnut with small-leaved lime (Tilia cordata), along with neighbouring autochthonous stands (pure ash – European and narrow-leaved), oak (summer oak), or their mixtures. Ellenberg’s indicator values reveal differences in the plant communities under black walnut comparing those under native tree species for the variables nitrogen, soil reaction and temperature. In addition, total cover is significantly higher under walnut. Other differences are visible from the detrended correspondence analysis ordination. The study also confirmed that in the stands of black walnut the preference of some species is suppressed, for example Brachypodium sylvaticum and Poa nemoralis in alluvial forests and Melica uniflora in hilly forests.

Effect of grazing removal on aboveground vegetation and soil seed bank composition in sub-alpine grasslands of northern Iran

Background: Knowledge about vegetation and soil seed bank composition and the processes that contribute to vegetation recovery after the removal of heavy grazing is lacking in sub-alpine ecosystems.Aims: In order to assess the effects of large herbivores on above-ground vegetation (AGV) and soil seed bank (SSB) characteristics, intensively sheep-grazed areas were compared to adjacent areas where grazing had been removed 10 years previously in a sub-alpine grassland of northern Iran.Methods: A total of 40 4-m2 (2 m × 2 m) plots were established in each treatment, and soil samples were collected from each plot within a depth of 10 cm. Plant species composition was determined for each plot during the flowering stage of herbaceous species in June 2011. The seedling emergence method was used to estimate SSB composition.Results: A total of 45 species (23 annuals and 22 perennials) emerged from the soil samples of the grazed area, while the number of species emerged from the soil samples of the previously grazing area was 76 (37 annuals and 39 perennials). The removal of grazing led to a significant increase in species richness and seed density in the SSB. Species turnover of AGV was higher, and that of the SSB was similar for grazed areas compared with areas that were formerly grazed. Detrended correspondence analysis ordination of AGV composition showed a clearly separate structure between grazed plots and plots where grazing has been removed, while the segregation was less clear for SSB composition.Conclusions: We concluded that restoration of locally degraded sites cannot rely on the SSB when grazing is stopped simultaneously and unvegetated gaps are colonised by vegetative growth rather than by seed.

Surface pollen deposition on glacier forelands in southern Norway II: Spatial patterns across the Jotunheimen–Jostedalsbreen region

This paper presents the results of a study of surface pollen deposition on 26 glacier forelands in the Jostedalsbreen–Jotunheimen region of southern Norway. Numerical techniques, including two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA), are used to identify distinct plant assemblages, to examine the pollen–vegetation relationship and to distinguish broad trends in the data. The source of pollen is fundamental; the majority of samples, especially those from sparsely vegetated sites, are dominated by arboreal pollen (up to 90% of the total land pollen (TLP) sum), most with a long-distance source. However, indicator taxa, notably Salix and Empetrum, although present at low frequencies, can hold the key to the true nature of the local vegetation. Indicator taxa produce strong correlations between their presence in the vegetation and representation in the pollen spectra, at times essential to distinguish plant communities. Multivariate analysis of the 197 surface pollen samples and vegetation data indicates the broad division of the sub-alpine and alpine vegetation into four major groups: pioneer communities, snowbed communities, heath communities and woodland. The primary DCA ordination axes show significant correlations with altitude and terrain age (e.g. correlation r = 0.36 between altitude and non-arboreal pollen (NAP) Axis-1). The most readily interpretable results are produced by CCA simultaneous ordination of vegetation data and NAP data. The potential for improving the interpretation of Holocene vegetation is assessed.

Macroinvertebrate Assemblages in Mountain Streams with Different Streambed Stability

AbstractBenthic macroinvertebrates are organisms primarily living in the streambed. The stability of the streambed is of vital importance to macroinvertebrate assemblages. Measurement of the streambed stability and sampling of macroinvertebrates were performed from 2005 to 2011 in four mountain streams: the Shengou, Diaoga, Jiangjia and Dabaini Rivers, which have different stability and are all located in the Yunnan plateau in southwestern China. The Shengou, Diaoga and Jiangjia Rivers are composed of gravels and cobbles, and the Dabaini River is mainly composed of gravels. The streambed stability was determined by the ratio of time over the sum of erosion and deposition areas of sediment per unit streambed width at each measured cross‐section.The Shengou River had the highest stability, followed by the Diaoga and Jiangjia Rivers. The Dabaini River had the lowest stability. A total of 70 taxa of macroinvertebrates belonging to 45 families and 68 genera were identified in these streams. Arthropods were the dominant taxonomic group. Collector gatherers had the highest density. Taxa richness, Shannon–Weaver index and K‐dominance curve were used to assess the biodiversity of macroinvertebrates. Results showed that the Shengou River had the highest biodiversity, followed by the Diaoga and Jiangjia Rivers. The Dabaini River had the lowest biodiversity. The detrended correspondence analysis ordination indicated that the streambed stability was the main factor that influenced macroinvertebrate assemblages, counting for 22.7% of the variance. The biodiversity and wet weight of the macroinvertebrates were highly dependent on the streambed stability. The biodiversity increased with the streambed stability and reached equilibrium when the stability was over 20 year m−1. The wet weight of macroinvertebrates showed an increasing trend with the streambed stability. However, no clear relation was identified between the density of macroinvertebrates and the streambed stability. It was concluded from this study that, in order to improve the ecological condition within the mountain streams, erosion and sedimentation must be controlled to enhance the streambed stability. Copyright © 2014 John Wiley &amp; Sons, Ltd.

설악산 양사면 하천에서의 고도차에 따른 저서성 대형무척추동물 군집의 공간 분포

There are marked differences in climate condition between east-facing slopes and west-facing slopes in Mt. Seorak (1,708 m). This study was conducted to find out the differences of benthic macroinvertebrate communities between both slopes of Mt. Seorak. Quantitative (Surber net; <TEX>$30cm{\times}30cm$</TEX>, mesh: 1mm) and qualitative (Hand net; mesh: 1mm) samplings ware carried out seasonally in each site which had 100-meter-high difference from November 2010 to November 2011. Most of the survey sites showed sound environmental conditions because they were located in the protection area of the national park. The benthic macroinvertebrates collected from all survey sites were composed of 158 species, 62 families, 17 orders, 7 classes and 5 phyla. DCA (Detrended Correspondence Analysis) ordination based on the abundance of benthic mactoinvertebrates showed that altitude was a major factor governing the structure of benthic macroinvertebrate community. There was no significant difference of the communities between both slopes.

山西高原草地景观的数量分类与排序

PDF HTML阅读 XML下载 导出引用 引用提醒 山西高原草地景观的数量分类与排序 DOI: 10.5846/stxb201307291977 作者: 作者单位: 山西林业职业技术学院,山西大学黄土高原研究所;山西省中阳县第一中学,山西大学黄土高原研究所,山西林业职业技术学院 作者简介: 通讯作者: 中图分类号: 基金项目: 山西省自然科学基金项目（2012011033-4）； 山西省林业厅科技创新项目（201021） Classification and ordination of grassland landscape in the Shanxi Plateau Author: Affiliation: Shanxi Forestry Technological college,,Institute of Loess Plateau, Shanxi University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:草地植被空间格局研究是草地景观研究中一项重要的基础工作。空间格局研究不仅限于描述景观的空间特征，而是要深入分析空间格局的分布规律及影响格局形成的原因及机制。以1：50万《山西省草地类型图》、《山西省行政区域图》及《山西省地形图》为主要信息源，借助GIS技术，应用TWINSPAN和DCA对山西高原草地景观的1127个样方进行研究。结果表明：（1）在TWINSPAN分类结果中，31个群丛组从左到右的排列顺序很好地揭示了山西高原草地景观的纬向地带性分布规律。即从40°43’N向34°34’N依次分布着北部草原、中部灌草丛和草丛及南部的暖温带草丛。（2）1127个样方DCA排序图纵轴揭示了明显的海拔梯度，即由上至下海拔逐渐降低，相应地草地景观变化为亚高山草甸、灌草丛、草原及河漫滩草甸；DCA排序图的横轴揭示了明显的水分梯度，即从左到右水分逐渐增加。两大优势群丛组样方及44个优势群丛组物种DCA的排序图都很好地刻画了山西高原水热组合的变化，即从西北向东南由于地形地貌引起的水热组合由冷干向暖湿逐渐变化，水热组合的梯度变化进一步影响了草地景观整体的空间分布格局。（3）GIS技术与数量生态学方法相结合有助于丰富景观生态学研究的技术体系。 Abstract:Spatial pattern is a reflection of the landscape heterogeneity over a region. Research on this pattern is a fundamental work in understanding the landscape structure, and has both theoretical and practical significance for exploring the composition and distribution laws of landscape components and their mechanisms. The key methods for realizing the spatial pattern include the comparison of pattern indices and spatial characteristics; the analysis of transition matrix of Markov Chain, and the dynamic simulation of spatial pattern based on cellular automata model. While these methods are proved to be usefull, the theoretical and technical framework has not yet been formed for the comprehensive research. The methods of quantitative ecology have been successfully used in vegetation pattern analysis on meso\ and mico\ scales. The integrated application of the methods in quantitative ecology and other modern techniques like GIS and RS might enrich the methodology of landscape study. In this study, based on the Grassland Type Map of Shanxi Province (1:500 000), Topography Map of Shanxi Province (1:500 000) and Administration Division Map of Shanxi Province (1:500 000), the Present Grassland Map of Shanxi Plateau (1:500 000) was compiled. Through the GIS techniques, 20mm×20 mm quadrat grids were set up on the Present Map, and then a set of 1127 effective quadrats was obtained. After the calculation of the importance values of individual quadrats, all the 1127 quadrats were analyzed using the quantitative methods of TWINSPAN (Two-Way Indicator Species Analysis) and DCA (Detrended Correspondence Analysis). The results showed that (1) the 31 association groups obtained from the TWINSPAN classification revealed the latitudinal zonality of grassland landscape in the plateau, i.e., the temperate grassland in the north, the shrub-grassland and grassland in the middle, and the warm temperate grassland in the south from 40°43'N to 34°34'N. (2) The vertical axis of DCA ordination plot indicated that, with the decrease in altitude from top to bottom, the grassland landscape changed gradually from the sub-alpine meadow to shrub-grassland, grassland and floodplain meadow; and the horizontal axis exhibited a clear water gradient, i.e., a gradual increase of wetness from left to right. The plots of DCA ordination for the quadrats of two dominant association groups and for the species of 44 dominant association groups reflected the gradient of rainfall and temperature changes, i.e., from the cold-arid conditions in the north-west to warm-wet conditions in the south-east across the plateau. This gradient of water-heat regime further influenced the spatial pattern of grassland landscape. (3) The integrated application of GIS technique and the methods of quantitative ecology could enrich the technical system of landscape ecology. The findings in this study suggest that either TWINSPAN or DCA was very useful for characterizing the distribution patterns of grassland landscape, and for exploring the possible causes of the patterns. The integrated application of GIS technique and quantitative techniques in ecology might have great potential for studies of landscape pattern dynamics, the drivers and the driving mechanisms. Further research on the dynamic characteristics and the driving factors of the grassland landscape in Shanxi Plateau should be conducted. 参考文献 相似文献 引证文献