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1.
Bioclimates are syntheses of climatic variables into biologically relevant categories that facilitate comparative studies of biotic responses to climate conditions. Isobioclimates, unique combinations of bioclimatic indices (continentality, ombrotype, and thermotype), were constructed for northern California coastal ranges based on the Rivas-Martinez worldwide bioclimatic classification system for the end of the 20th century climatology (1971–2000) and end of the 21st century climatology (2070–2099) using two models, Geophysical Fluid Dynamics Laboratory (GFDL) model and the Parallel Climate Model (PCM), under the medium-high A2 emission scenario. The digitally mapped results were used to 1) assess the relative redistribution of isobioclimates and their magnitude of change, 2) quantify the loss of isobioclimates into the future, 3) identify and locate novel isobioclimates projected to appear, and 4) explore compositional change in vegetation types among analog isobioclimate patches. This study used downscaled climate variables to map the isobioclimates at a fine spatial resolution −270 m grid cells. Common to both models of future climate was a large change in thermotype. Changes in ombrotype differed among the two models. The end of 20th century climatology has 83 isobioclimates covering the 63,000 km2 study area. In both future projections 51 of those isobioclimates disappear over 40,000 km2. The ordination of vegetation-bioclimate relationships shows very strong correlation of Rivas-Martinez indices with vegetation distribution and composition. Comparisons of vegetation composition among analog patches suggest that vegetation change will be a local rearrangement of species already in place rather than one requiring long distance dispersal. The digitally mapped results facilitate comparison with other Mediterranean regions. Major remaining challenges include predicting vegetation composition of novel isobioclimates and developing metrics to compare differences in climate space.  相似文献   

2.
Mediterranean ecosystems comprise the second biodiversity hotspot area after tropical rain forests and will be most affected by global climate change. Therefore, it is important to understand community dynamics for effective conservation in this region. We investigated the relationships between soil moisture, nitrogen forms and community structuring in Quercus ilexL., Erica arborea L. and Sarcopoterium spinosum (L.) Spach communities, representing different successional stages, distributed as Mediterranean enclaves on the Sinop Peninsula (Turkey). The soil moisture, ammonium, nitrate and nitrite content were measured seasonally. Differences in these abiotic parameters within and between communities over seasons were tested. Previously collected biotic data were then used to analyze the relationship between soil parameters and community structure. Significant differences in soil parameters within and between seasons were found within and between communities. Our results show that there are different relationships between soil moisture, nitrogen forms and community structure in Mediterranean plant communities representing different successional stages. Differentiation in vegetation structure during succession cause changes especially in the water and nitrate content of the soil, and these changes in turn affect the continuity of community structure in Mediterranean plant communities.  相似文献   

3.
Abstract

The analysis of landscape changes in space and time plays an important role in landscape ecology. Analyzing landscape dynamics through time may be crucial for identifying historical and current processes that shape the actual landscapes and for developing predictive landscape models for ecosystem management and conservation. In this view, the propensity of land cover patches to change is at least partially related to the nature of their contact types. The interactions of a given patch with adjacent land cover types affect both land use exploitation by humans and vegetation dynamics. The aim of this paper is to use patch boundary dynamics for describing the landscape changes that occurred in the Lepini Mountains (central Italy) during 1954 – 2000. Results show an increase in landscape complexity in the Mediterranean land units and a corresponding decrease in landscape complexity in the Temperate land units. This differential trend is due to a complex, human-driven temporal dynamics of Mediterranean ecosystems that generates heterogeneity as opposed to a diffuse landscape abandonment in the Temperate region that leads to a more homogeneous boundary structure.  相似文献   

4.
This paper reports a phytosociological study on managed hay meadow communities in the main mountains of the Spanish Central Range. Multivariate techniques (Cluster analysis and CA-ordination) were applied in the classification of the relevés and ordination of vegetation units and species. Clusters were related to the following associations: Agrostio castellanae–Arrhenatheretum bulbosi, Festuco amplae–Cynosuretum cristati, and F. amplae–Agrostietum castellanae. The scattergram suggested that the dynamic patterns between communities are associated with soil nutrient content and moisture. We propose a new subassociation: F. amplae–A. castellanae gaudinietosum fragilis that includes Salmantincensean Agrostis castellana communities growing in regions with lower supramediterranean thermotype.  相似文献   

5.
石羊河下游位于干草原向荒漠过渡区域,有天然种子植物23个科,73个属,123个种,不仅有典型的戈壁荒漠成分,也渗入一些草原化荒漠植物种类.其荒漠植被特征更明显,群落层片结构简单,群丛建群种的74.4%是灌木和半灌木,构成了灌木、半灌木旱生群落;1年生草本植物随季节性降雨可形成"灌草丛",成为荒漠植被的重要组成部分.在植物地理区系成分上,温带成分属占优势,其中地中海至中亚分布型及其变型最多,其次为北温带分布及其变型.整个区域内植物的分布集中在生境较适宜的区域,空间结构的成群性高,但在小区域内植物种的分布则较单一.植被可划分为4个植被型,5个植被亚型,13个群系组,23个群系,38个群丛.地域性植被以绿洲为中心,成环状分布,可分为3个带.  相似文献   

6.
Abstract. Floristic and climate data from 150 plots in 25 sites in Galicia, Spain, were analysed to test the hypothesis that climate is the major factor governing the distribution of woody plant species. TWINSPAN classification, Detrended Correspondence Analysis and Canonical Correspondence Analysis were applied in successive stages of the data analysis to describe vegetational variation in relation to climatic gradients. Six groups of species were defined, two clearly oceanic (Maritime and Cool Maritime), one mediterranean maritime, and three mediterranean (Cold Mediterranean, Cool Mediterranean and Temperate Mediterranean). An aridity gradient was revealed as the primary factor regulating the distribution of the species considered. This main gradient reflects the transition between the Eurosiberian and Mediterranean bio-geographic regions. The gradient can be characterized by means of the Vernet bioclimatic index. A value ≥ 4 for this index can be taken to define the mediterranean zone in our study area. The mean minimum temperature in the coldest month was the second most influential climatic variable. Partial ordination analysis revealed that the residual variation was insignificant and that the observed variation in vegetation can be fully accounted for by climatic variables.  相似文献   

7.
Aim Fire is a key disturbance in Mediterranean‐type climates. It has effects on plant community structure and composition and on the evolution of different groups of the flora. This study aimed to quantify changes in demography and vegetative regeneration caused by fire in key species in Mediterranean vegetation and to examine the hypothesis of convergence in characteristics of species in relation to fire by comparing the occurrence of bioecological groups of plants in the Mediterranean basin with groups of plants in other areas of Mediterranean‐type climate. Methods Changes in the demography and species composition after fire were studied in a plant community developed from a pinewood (Pinus halapensis Miller plantation) in north‐western Sardinia. The demography of the three main species dominating the community after fire, Cistus monspeliensis L., Pistacia lentiscus L. and Chamaerops humilis L., was quantified by quadrat measurements in areas of the plantation which had never been burnt and in different parts 1 and 8 years after fire. Vegetative regeneration of resprouting species was also quantified. From the results of the survey and examination of published material, comparison was made between bioecological groups of species in different regions with Mediterranean‐type climate to assess the similarities and differences in the biogeographic distribution of what can be broadly considered fire‐related functional groups of plants. Results Seeder and sprouter species showed contrasting population responses to fire in an area planted to pines over 50 years ago but subsequently in part subjected to fire. Mean species richness at a 25 m2 scale decreased by c. 28% over 8 years after fire. C. monspeliensis in the unburnt pinewood was sparse and sporadic but recruitment after fire was prolific and produced plant densities similar to those of similar seeder species in other Mediterranean Basin areas and in Californian chaparral. However density was very variable between burnt areas of different ages. In particular, seedling recruitment was much lower under the canopies of P. lentiscus than away from the canopy. Sprouter species (P. lentiscus and C. humilis) had recruited into the pinewood over time since planting of the pines but did not recruit after fire. Above‐ground parts of plants were killed by fire and resprout stem density per plant increased initially but later decreased slightly due to self thinning of stems on each plant. Main conclusions Plant demographic and floristic changes after fire in the Sardinian pinewood were similar to those reported for other Mediterranean plant communities. Resprouting species only recovered by vegetative means and, in contrast to seeder species, underwent thinning of stems within, rather than between, plants, so plant density did not change after fire in resprouting species. The Tertiary relic, strongly resprouting, animal‐dispersed group of species in the Mediterranean Basin has a homologous group in the North American mediterraneoid flora but not in the Southern Hemisphere. In contrast, the general group of resprouting species which recruit after and/or between fires in the Southern Hemisphere mediterraneoid areas corresponds to only a small group of taxa in the Mediterranean basin. The bioecological group of seeder species, which are killed by and establish prolifically after fire, are represented in both Northern and Southern Hemisphere Mediterranean‐type heathlands but are much more species rich in the south.  相似文献   

8.
The evergreen broad-leaved forest of Rhododendron ponticum represents a special type of Mediterranean vegetation because of their relict nature (allegedly pre-glacial, Southern-Iberian and Pontic) and connection with Macaronesian-Atlantic flora. The findings of ecomorphological (growth forms) and phenological (phenology) studies point to characteristics typical of its relict character and its relationship with subtropical lauroid vegetation (greater forest stratification, larger leaves, high percentage of photosynthetic stems, scarce tomentosity, pre-flowering in a season different to Mediterranean species and closeness of autumn–winter flowering species). There are, however, links with typical Mediterranean vegetation (Quercus L. forests) that surrounds the Rhododendron stands, due to its adaptation to Mediterranean climate (sclerophyll leaves, plant and leaf duration, post-fire regeneration, fleshy fruit and fruit setting-seed dispersal seasonality). Within the community, different groups of plants show different adaptations to the same biotope, suggesting their distinct paleo-phytogeographical origins. The results confirm the singularity of this vegetation within the typically Mediterranean environment where it grows and its connections with other extra-Mediterranean types.  相似文献   

9.
A consistent vegetation classification is an essential tool for conservation and monitoring purposes, also for semi-natural habitats such as pastures and hay meadows that are linked to traditional land use and generally considered crucial to maintain biodiversity within agricultural systems. Indeed, these habitats can be strongly affected by land abandonment or agriculture intensification. Despite their importance in the framework of the EU Habitats Directive (43/92/EEC), information on distribution, species composition, and conservation status is still lacking for many regions. To fill these gaps, we investigated from a phytosociological point of view the sheep pastures of the North-Western Sardinian trachy-basaltic sector. Three main communities were described as new: (i) perennial montane (meso-supratemperate) cattle and sheep pastures (Loto alpini-Festucetum morisianae); (ii) mixed (annual and perennial) Mediterranean (lower Thermomediterranean to lower supratemperate) sheep pastures (Ornithogalo corsici-Poetum bulbosae); and (iii) annual ploughed subnitrophilous Mediterranean and Temperate pastures (Cynosuro polybracteati-Vulpietum ligusticae). As the first two host numerous endemic taxa and show a peculiar floristic composition, we assign them a higher conservation value, testified also by their classification in two new syntaxa: Danthonio decumbentis-Caricenion insularis (Molinio-Arrhenatheretea) and Ornithogalo corsici-Trifolienion subterranei (Poetea bulbosae), respectively.  相似文献   

10.
Woody species populating the major Mediterranean ecosystems in the world are characterized by different levels of adaptation to the seasonal Mediterranean climate conditions. Many species of these ecosystems show wood features that allow high efficiency of transport when water is available, while maintaining hydraulic safety during drought periods. This study focuses on the anatomy of juvenile and mature wood of some species representative of continuous sequences of Mediterranean vegetation formations according to gradients of water availability, from xeric to relatively mesic: Cistus monspeliensis L., Rhamnus alaternus L., Myrtus communis L., Pistacia lentiscus L., Olea europaea L., Quercus ilex L., Fraxinus ornus L. and Ostrya carpinifolia L. Twigwood collected in Southern Italy was anatomically compared with the stemwood of the same species represented in the reference slide collection of the National Herbarium of the Netherlands (Lw). The “hydraulic distance” between the wood of main stems and twigs was estimated on the basis of suites of anatomical features related to water efficiency/safety. Although some attributes (i.e. porosity and type of imperforate tracheary elements) were similar in young twigs and older rings, other traits (i.e. vessel frequency and size) evidenced the different hydraulic properties of twig and stemwood. The difference between juvenile and mature structures was large in the species of the mesic end of the gradient while it was relatively small in those more xeric. This tendency is in agreement with the habit gradient from medium-sized trees to small evergreen/drought deciduous shrubs according to decreasing water availability in Mediterranean vegetation types.  相似文献   

11.
This work investigates the Polylepis-dominated forests in the high Andes of central and southern Bolivia, using both the Braun-Blanquet approach and multivariate analysis. These are among the highest altitude forest types in the world, and the region under study is a center of diversity for the genus, and is located at the confluence of four biogeographical provinces. Nine main plant communities were distinguished. Correspondence Analysis revealed a strong dependence of community composition primarily on biogeographic as well as on bioclimatic features. The greatest forest type diversity is found in the central part of the Cordillera Oriental in the Tropical pluviseasonal bioclimate, within a Supratropical thermotype and a Subhumid ombrotype.  相似文献   

12.
Question: How do patterns in colonization and patch expansion of an invasive woody plant (Larrea tridentata, Zygo‐phyllaceae) differ between two grassland ecosystems at a biome transition zone? Location: Semi‐arid/arid transition zone in central New Mexico. Methods: Frequency of occurrence, height, and surface area of saplings (n= 134) and patches of adult plants (n= 247) of the invasive shrub, L. tridentata, were measured within a mosaic of ecosystems dominated either by the Chihuahuan Desert species, Bouteloua eriopoda (Poaceae), or the shortgrass steppe species, B. gracilis, located within 1 km of the L. tridentata‐dominated ecosystem. Distances between L. tridentata patches and patch area were used to estimate connectivity as a measure of propagule pressure. Sapling age (estimated from height using previously established relationships) and distance to the L. tridentata‐dominated ecosystem was used to evaluate patterns in dispersal. Cover by species or functional group inside each L. tridentata patch was compared with surrounding vegetation to estimate changes in species composition with patch expansion. Results: L. tridentata saplings (< 1%) and adult patches (15%) occurred less frequently in B. gracilis‐dominated ecosystems than expected based on areal extent of this ecosystem type. Propagule pressure did not differ with distance from the core ecosystem dominated by L. tridentata. Evidence for both local and long‐distance dispersal events was found. Similar relationships between number of plants and patch area in both grassland types indicate similar patterns in patch expansion. Cover of perennial forbs was higher and cover of dominant grasses was lower in L. tridentata patches compared with the surrounding vegetation for both ecosystem types. Conclusions Spatial variation in L. tridentata saplings and patches at this biome transition zone is related to the different susceptibilities to invasion by two grassland ecosystems. The persistence of grasslands at this site despite region‐wide expansion by L. tridentata may be related to the spatial distribution of B. gracilis‐dominated ecosystems that resist or deter invasion by this woody plant.  相似文献   

13.
About 45% of the total surface area of the Castile and Leon region today can potentially be occupied by semi-deciduous forests, chiefly dominated by Quercus faginea Willd. and Quercus pyrenaica Lam. On the basis of extrapolated trends in annual mean temperature and precipitation in Castile and Leon observed over the 37-year period from 1961 to 1997 [del Río et al. 2005], predicted changes in the areas covered by Q. faginea and Q. pyrenaica forests in 2025, 2050 and 2075 were made. A decrease in Q. faginea forests may occur if observed trends in temperature and precipitation continue. With respect to Q. pyrenaica forests, they may increase in present Mediterranean areas and decreases in Temperate Submediterranean areas. In some cases, both types of forests could be replaced by deciduous forests. The predicted results in the natural distribution of vegetation types by the bioclimatic models can be used to establish policies for improved future nature conservation and land management.  相似文献   

14.
The geographical distribution of the grass genusHelictotrichon in the Mediterranean Region is analysed and mapped for 33 taxa. Based on only a single life form (perennial herb), a variety of edaphically, climatically and altitudinally differently adapted species complexes has evolved in the area. Most of these complexes show west-east disjunctions and contain geographically, sometimes even edaphically vicarious taxa with complementary distribution. A transition from mesomorphic to xeromorphic habit occurred independently in different species groups and led to the establishment of the modern Mediterranean taxa which are in part highly polyploid derivatives of more mesophilic diploids. The significance of polyploidy, patterns of parapatric and sympatric distribution, biogeographical borders, and centres of species diversity are discussed in context with the history of the Mediterranean vegetation. New combinations are:Helictotrichon setaceum subsp.petzense, H. pratense subsp.lusitanicum, H. praetutianum.  相似文献   

15.
ABSTRACT

A phytosociological study of the urban woods of Rome is described. Six syntaxonomical types were identified: 1) Orno-Quercetum ilicis, an edaphic-xerophytic variant of the natural potential vegetation of the city (deciduous Quercus sp. pl. woods); 2) Aquifolio-Fagetum carpinetosum betuli, in the northern slopes of alluvial valleys; 3) Q. suber and Q. pubescens wood, ranked in Quercetalia pubescenti-petraeae order 4) Quercetum ilicis galloprovinciale suberetosum; 5) coppice of Q. cerris and Q. frainetto, which belongs to the Teucrio siculi-Quercion cerridis alliance; 6) mixed mesophile wood of Q. cerris and Ostrya carpinifolia which can be considered a transition between the Doronico-Fagion and the Teucrio siculi-Quercion cerridis alliances. All of these six woody vegetation types are characterised by the large penetration of Mediterranean species belonging to the Quercetea and Quercetalia ilicis and the middle-European ones of the Querco-Fagetea. This mosaic of species exemplifies the bioclimatic characteristics of Rome, which is situated in a Mediterranean transitional region.  相似文献   

16.
Barbero  M.  Loisel  R.  Quézel  P. 《Plant Ecology》1992,(1):19-34
Quercus ilex sensu lato plays an important role in Western Mediterranean ecosystems, but is poorly developed in the Eastern Mediterranean where it is often replaced by Quercus calliprinos.The occurrence of Quercus ilex in the different bioclimates and their thermic subdivisions is presented on a small scale. Under certain geographical and ecological conditions, Quercus ilex participates in the organization of vegetation ecosystems from the meso-Mediterranean to the oro-Mediterranean altitudinal zones. Quercus ilex imposes microclimatic constraints on its associated species; it thus organizes and original understory vegetation structure (ethological groups) which will be defined in this study.One of the reasons for the success of Quercus ilex stems from its remarkable resistance to ecological constraints. A broad synthetic presentation of foliar area index variations in relation to different types of stress serve as a basis for an explanation of the sclerophyllous model in the Mediterranean region.Finally, historical factors are outlined as being critical characteristics in the determination of the present organization and spatial structure of Quercus ilex ecosystems. These considerations will be analyzed from a paleobioclimatical point of view, including data related to human pressure.  相似文献   

17.
Aim To assess at a broad scale the vulnerability of Mediterranean vegetation to alien plant invasion under different climatic and disturbance scenarios. Location We simulated the vegetation biogeography and dynamics on five of the main islands of the Mediterranean Basin: Mallorca, Corsica, Sardinia, Crete and Lesvos. Methods We used LPJ‐GUESS, a generalized ecosystem model based on dynamic processes describing establishment, competition, mortality and ecosystem biogeochemistry. We simulated the vegetation distribution and dynamics using a set of plant functional types (PFTs) based on bioclimatic and physiological parameters, which included tree and shrub PFTs defined especially for the Mediterranean. Additionally, two invasive PFTs, an invasive tree type and an invasive herb type, were defined and used to estimate the vulnerability to invasion of a range of different ecosystems. The model was used to simulate climate changes and associated changes in atmospheric [CO2] to 2050 according to two SpecialReport on Emissions Scenarios climate scenarios (A1Fi and B1) combined with mean disturbance intervals of 3 and 40 years. Results The simulations and scenarios showed that the effect of climate change alone is likely to be negligible in many of the simulated ecosystems, although not all. The simulated progression of an invasion was highly dependent on the initial ecosystem composition and local environmental conditions, with a particular contrast between drier and wetter parts of the Mediterranean, and between mountain and coastal areas. The rate of ecosystem disturbance was the main factor controlling susceptibility to invasion, strongly influencing vegetation development on the shorter time scale. Main conclusions Further invasion into Mediterranean island ecosystems is likely to be an increasing problem: our simulations predict that, in the longer term, almost all the ecosystems will be dominated by exotic plants irrespective of disturbance rates.  相似文献   

18.
Abstract. The syntaxonomy of the perennial nitrophilous vegetation assigned to the Artemisietea vulgaris of the northern part of the Iberian Peninsula (Basque Country and surrounding areas) was revised. The study area is of biogeographic importance due to its transitional character - here, the ruderal vegetation of the Mediterranean and that of temperate Europe meet. Numerical ordination of the communities was performed in order to reveal systematic relations between the syntaxa. Two subclasses, Artemisienea vulgaris and Onopordenea, encompassing five orders, Convolvuletalia, Galio-Alliarietalia, Artemisietalia, Onopordetalia, Carthametalia lanati, and seven alliances with 12 associations and two rankless communities were distinguished.  相似文献   

19.
为了阐明固沙过程中蚂蚁群落结构分布特征及其对土壤性质的影响,在腾格里沙漠固沙植被区选取流动沙地以及5 a、8 a、34 a和57 a固沙植被区为研究样地,对不同样地蚂蚁群落的个体数、类群数以及蚁丘内外土壤理化性质进行测定,进而分析了不同样地蚂蚁群落分布特征及其与土壤因子间的关系。结果表明:(1)固沙植被区蚂蚁群落中的优势类群为掘穴蚁(Formica cunicularia),个体数占比为78.87%。(2)57 a固沙植被区蚂蚁密度显著低于8 a和34 a固沙植被区(P < 0.05);5 a固沙植被区蚂蚁类群数显著低于其他植被区(P < 0.05)。(3)57 a固沙植被区蚁丘中土壤含水量、土壤黏粒和土壤全钾显著高于非蚁丘,而土壤电导率和土壤粉粒显著低于非蚁丘(P < 0.05)。8 a和57 a固沙植被区蚁丘中土壤pH显著高于非蚁丘,8 a固沙植被区蚁丘中土壤有机碳显著高于非蚁丘,8 a和34 a固沙植被区蚁丘中土壤全氮显著高于非蚁丘(P < 0.05)。(4)蚂蚁群落组成与土壤粒径、电导率、pH、有机碳、全氮、全磷和有效磷含量的相关关系显著;偏RDA 结果表明,蚂蚁类群数是影响固沙区土壤理化性质的主要限制因子。综合表明,腾格里沙漠不同固沙年限植被区蚂蚁群落组成差异较大,更丰富的蚂蚁群落有利于改善土壤质地,促进土壤理化性质向良好的方向发展,对实现荒漠生态系统恢复起到推进作用。  相似文献   

20.
Abstract. Question: Does the influence of plant canopy on seedling establishment interact with climate conditions, and particularly, do intensified drought conditions, enhance a positive effect of the vegetation canopy on seedlings in Mediterranean‐type ecosystems. Location: Mediterranean shrubland near Barcelona, Spain at 210 m a.s.l. Methods: Over the course of four years we recorded seedling emergence and survival in open areas and below vegetation under control, drier and warmer experimental climatic conditions. Results: Seedling emergence is more sensitive to climate conditions than later stages of growth. When considering the whole set of species, the total number of established seedlings at the end of the experiment was lower in the drought and warming stands than in control ones, and vegetation canopy increased the number of these seedlings in the drought stands. Drought reduced seedling emergence but not warming, while the interaction between climate treatments and vegetation canopy was not significant. Seedling survival was lower in the warming treatment than in the control. Under drought conditions, vegetation canopy increased seedling emergence of the dominant Globularia alypum. In control stands, vegetation canopy reduced their survival. Vegetation canopy increased the survival of the dominant Erica multiflora in warming stands, and it reduced the survival of G alypum in drought stands. No significant effects of drought and warming were observed in the seed rain of these two species. Conclusions: The balance of the facilitation‐competition interactions between vegetation canopy and seedling establishment in Mediterranean‐type ecosystems determined by water availability, and drought conditions enhance the positive effect of vegetation canopy. This interaction is species‐specific and shows important between‐year variability.  相似文献   

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