Natural Vegetation Patterns Research Articles

Microclimatic Zonation and Climatic Variability of Sikkim Himalaya

The Köppen classification of climate integrates precipitation and temperature information with natural vegetation patterns to create a precise representation of any particular region's climate. This integration depends on the empirical relationship of climate and vegetation, which indicates that distinct locations in the same class have similar vegetation attributes. Köppen climatic classification factors are explained and Sikkim's climate characteristics are regionalized based on it. The method for making representations of air temperatures and precipitation has been described, and an illustration of Sikkim's climatic zones with variability is generated as a result of these changes. The geographic pattern of climatic types and subtypes in Sikkim has been briefly addressed using an available high-resolution gridded dataset (ERA5-Land). This is described that the constraints of microclimatic zonation emanate from the empirical prerequisite of climate classifications, as well as the nature of data selection and the methodologies employed for climate variability analysis and classification. Based on the Köppen classification for the long term (1980–2021), the Sikkim Himalaya contains three primary climatic classes, particularly ETc (cold, tundra, and cool summer), Cfc (moderately warm, humid, and cool summer), and Cfb (moderately warm, humid, and warm summer). Climate variability on the basis of temperature and precipitation change with respect to 1980–2021 over the entire Sikkim Himalaya concludes that the climatic pattern of the Sikkim has been changed from cold-dry to warm-wet. The alteration in the corresponding climatic pattern is further supported by changes in LULC and NDVI. The results suggest that the precipitation change in the past two decades (1980–2000) is negative, while a significant positive change has been noticed in the recent two decades (2001–2021). Subsequently, the number of extremely wet days decreases in the entire ETc and Cfc climate zones. Regardless, the southern part of the Cfb climatic zone has experienced an increase in extremely wet days. This study's findings will significantly contribute to the development of future policies and initiatives by providing insights crucial for achieving sustainable development, environmental protection, and climate change adaptation.

Highways to invasion: Powerline servitudes as corridors for alien plant invasions

AbstractHuman use of powerline servitude corridors for the secure transmission and distribution of electricity disturbs natural landscapes and changes vegetation patterns. We examined vegetation communities under two powerlines in the Limpopo province, South Africa (Khakhu line 22KV and Fundudzi 132KV powerlines). Twelve invasive alien species were identified in Khakhu and Fundudzi, dominated by Khaki bush Tagetes minuta, common guava Psidium guajava, black‐jack Bidens pilosa, fierce thorn apple Datura ferox and common lantana Lantana camara. Sites closest to human settlements showed high alien species richness, whilst sites located further away were dominated by alien L. camara, but had a low overall species richness. Conversely, areas away from human settlements showed lower levels of alien invasion. Weak overlaps in the principal coordinates analysis polygons for the two powerline servitudes suggest that alien plant compositions are dissimilar, with five identified species groups being identifiable among sites, and thus a high potential for invasion success from multiple taxa. The research findings showed that powerline corridors could potentially trigger invasion success via disturbance as they act as pathways for arrival and should be a focus for management efforts to prevent further spread.

Topological differentiation of the vegetation cover of the Sandomiria Upper Dnister geobotanical district

The article provides distribution patterns of natural vegetation depending on topological conditions and outlines the main directions of its anthropogenic transformation. The boundaries as well as botanical and geographical features of the studied district are specified. The syntaxonomic classification of plant communities is presented. The combinative ecological and coenotic profile was created showing distribution patterns of the main plant communities in relation to changes in the indicator values of ecological factors. Three types of mesocombinations are distinguished: forest, grassland (meadow) and swamp-flood ones. Averaged (relevant) indicator values were calculated based on environmental conditions. It has been established that the forest range is characterized by the indicators close to the background ones, which indicate a high stabilizing role of forest ecosystems. Correlative dependence between changes in indicators of certain factors was found, that enables to predict possible cause-and-effect changes. Under current trends of anthropogenic and climatic changes, a decrease in the humidity regime along with raise in soil pH can be expected in the future, while increase in seasonal changes in moisture will accelerate processes of nitrification and soil mineralization. Some habitats within the district are under significant negative effect of invasive species, e.g. the territory between the Lomnytsia River and Kolomyia town is classified as the one under the highest degree of threats due to huge, probably largest in Ukraine, areas of Heracleum sosnowskyi, Erigeron annuus, Solidago canadensis and Rudbeckia laciniata. In the future, this region may undergo substantial transformation and a special attention is required to protect its biodiversity.

High-Mountain Landscape Classification to Analyze Patterns of Land Use and Potential Natural Vegetation

In Georgia’s Lesser Caucasus, extremely species rich wooded grasslands are still used as pastures or meadows. These silvopastoral systems are one of the oldest land-use types in Europe, hosting both light-demanding and shade-tolerant species. However, in Europe silvopastoral systems have decreased over the past centuries. The aim of this study is to map, quantify, and classify the local land use and forest types in comparison to the potential natural vegetation to analyze and evaluate the high-mountain landscape pattern. Therefore, we mapped a 223 km2 study area and classified this mountainous terrain by topographical variables in a cluster analysis. Our results revealed a small-scale pattern of agriculture and forest in the study area, both strongly interlinked. The forest pattern strongly depends on altitude and aspect. The mentioned wooded grassland consists of forests with varying canopy covers connecting the settlement-near pastures and meadows in the montane belt with the natural open grassland in the alpine belts. The forest is in a near-natural condition compared with the potential natural vegetation. However, the quantifications revealed shrub encroachment indicating land-use abandonment. The compiled GIS-maps and the spatial classification of the landscape can be used to support sustainable management strategies in forestry and agriculture.

An analysis of multidimensional poverty in Nigeria using statistical and geospatial modelling: A case study of Jigawa state

Despite recent advances in reducing poverty across the world, millions of people remain on the verge of or already living in severe multidimensional poverty especially in third world nations. The poor in Nigeria suffer from a feeling of voicelessness, helplessness, mistreatment, a complete lack of capacity to influence important choices that impact their life, and a lack of social networking inside state and societal organisations. The goal of this research is to conduct a geospatial analysis of Nigeria’s multidimensional poverty and to identify the geospatial distribution pattern of poverty in Jigawa State as a case study. As a result, comprehend the causes of Jigawa’s complicated poverty condition and to create the state’s first ever poverty map. Also, to look at the country’s poverty trends, with a particular emphasis on Jigawa. The National Bureau of Statistics provided the headcount poverty statistics for Nigerian states, which were downloaded and analysed using simple geospatial approach. The findings revealed a dynamic pattern in Nigerian state poverty from 1996 to 2019. The distribution of poverty in Jigawa state, as a case study, revealed that physical and natural environment resources play a critical role in the state’s high poverty rate. Natural drainage, fertile soil, flat topography, and vegetation pattern all aid other people’s poverty levels in different parts of the state. Future study will examine the linking between environmental, social, religious, and political factors and multidimensional poverty using a geospatial method to map the state’s poverty, which has consistently ranked at the bottom of the Nigeria States Poverty Index.

Edaphic factors influencing vegetation colonization and encroachment on arsenical gold mine tailings near Sudbury, Ontario

Mine tailings are found worldwide and can have significant impacts on ecosystem and human health. In this study, natural vegetation patterns on arsenical (As) gold (Au) mine tailings located in Sudbury, Ontario were assessed using transects located at the edge of the tailings and on the tailings. Vegetation communities were significantly different between the edge and open tailings areas of the site. Arsenic concentrations in both areas were extremely variable (from 285-17,567 mg/kg) but were not significantly correlated with vegetation diversity at the site. Nutrients (carbon (C), phosphorus (P)) and organic matter concentrations were associated with higher diversity and with the presence of climax vegetation on the tailings, but there were no significant relationships between tailings chemistry and vegetation indices on the edge. Encroachment onto the tailings from the edge occurred in conventional succession patterns, with a clear gradient from grasses (Agrostis gigantea) to trees such as Picea glauca. On the tailings, a nucleation pattern was visible, distinct from conventional succession. Trees and shrubs such as Betula papyrifera and Diervilla lonicera were associated with higher diversity and higher nutrient concentrations in the underlying tailings, whereas grasses such as A. gigantea were not. We concluded that at all areas of the site, vegetation - particularly trees - was facilitating amelioration of the underlying tailings. Despite high concentrations of As, nutrients appeared to have a greater influence than metals on vegetation diversity.

Climate Variability Induced Shifts in Nitrogen Loading from Terrestrial to Aquatic Ecosystems

Nitrogen is one of the critical nutrients regulating terrestrial and aquatic productivity, and is linked to degradation of water quality of freshwater and marine ecosystems worldwide. The landscape patterns of stream nitrogen components, concentrations and loadings and their relationships with climate variability and landuse, were analyzed and quantified in this study. We used stream nitrogen concentration data collected at 2,125 sites and climate data at 301 weather stations during 1976 to 2005 in 30 eco-regions across British Columbia, Canada. While the patterns of stream nitrogen component, concentration, and loading distributions were found to be related to landscape patterns of climate variability, human activities, landuse, natural vegetation, and relief across British Columbia, the climate variability on both temporal a d spatial scales were found to be the dominant driver of variability in loading and concentrations of nitrogen. Elevated air temperature gradient across the landscape of British Columbia resulted in a significant increase in stream nitrogen loading from terrestrial into aquatic ecosystems. Precipitation, nitrogen deposition, population density and urban area also significantly affected the stream nitrogen components, concentrations and loadings. We suggest that climate change, especially shifts in temperature and precipitation, along with increased human activities tend to have important implications for loading of nitrogen from terrestrial to aquatic ecosystems and associated water quality in aquatic ecosystems

What Do Plants Leave after Summer on the Ground?—The Effect of Afforested Plants in Arid Environments

The implementation of afforestation programs in arid environments in northern China had modified the natural vegetation patterns. This increases the evaporation flux; however, the influence of these new covers on the soil water conditions is poorly understood. This work aims to describe the effect of Willow bushes (Salix psammophila C. Wang and Chang Y. Yang) and Willow trees (Salix matsudana Koidz.) on the soil water conditions after the summer. Two experimental plots located in the Hailiutu catchment (Shaanxi province, northwest China), and covered with plants of each species, were monitored during Autumn in 2010. The monitoring included the soil moisture, fine root distribution and transpiration fluxes that provided information about water availability, access and use by the plants. Meanwhile, the monitoring of stable water isotopes collected from precipitation, soil water, groundwater and xylem water linked the water paths. The presence of Willow trees and Willow bushes reduce the effect of soil evaporation after summer, increasing the soil moisture respect to bare soil conditions. Also, the presence of soil water with stable water isotope signatures close to groundwater reflect the hydraulic lift process. This is an indication of soil water redistribution carried out by both plant species.

Agricultural systems and terrace pattern distribution and preservation along climatic gradient: From sub-humid mediterranean to arid conditions

Agricultural terraces are a well-distributed agrotechnical method around the world. The current review aims to provide a holistic analysis of agricultural terrace spatial distribution along a climatic gradient of sub-humid Mediterranean, semi-arid and arid climate zones.It focuses on the relationship between geographic conditions and spatial distribution only, and does not examine chronological establishment or use. Three case studies that were carried out in the Land of Israel are presented and explored according to their geographic occurrence. In the Judean Mountains (central Israel), under sub-humid Mediterranean conditions, agricultural terraces are characterised by terrace coverage on slopes and in valleys. Annual rainfall average in this region is between 500 and 700 mm, allowing for vast rain-fed agriculture based on direct rain. In the Southern Shephelah (the Judean foothills, central Israel), a region under semi-arid conditions, agriculture terraces are located in small spots on the slopes, and in terrace fields in the valleys. Annual average rainfall in this region is between 300 and 400 mm. Rain-fed agriculture was sustained by direct rain and additional runoff generated on rock outcrops. In the Negev Highlands (southern Israel), a region under arid climate conditions with annual rainfall average of 100 mm, runoff farm terraces are located in valleys, and agriculture sustenance was based on water harvesting from the slopes. The terrace pattern distribution is similar to the natural vegetation pattern distribution of the three given areas.For the past several dozen years, changes in land use methods have resulted in the abandonment of many agricultural terraces in these areas. Terrace abandonment leads to the collapse of retaining walls and erosion of soil and sediments from the terrace body, with the latter occurring at a high rate in the arid Negev highlands. However, in the Judean Mountains and the Judean Shephelah, areas under sub-humid Mediterranean and semi-arid conditions, the intensity of erosion is lower since the terraces are covered by dense shrubs such as Sarcopoterium spinosum, which stabilizes and moderates soil and sediment erosion. This regional difference shows that the absence of maintenance is more significant in arid areas.To conclude, there are two primary insights 1: Climate has a dominant effect on agricultural terrace distribution, and ancient farmers knew how to adapt to different climate conditions. 2: Climate conditions have a major effect on terrace preservation and maintenance.

Topographically-controlled site conditions drive vegetation pattern on inland dunes in Poland

The inland dunes of Central Europe are commonly overplanted by Scots pine (Pinus sylvestris) monocultures in which the primary occurrence of the natural vegetation pattern is obliterated. We hypothesize that on naturally revegetated inland dunes the pattern is clear and driven by topographically-controlled site conditions. To test this hypothesis, we addressed the following research questions: (1) Does topography drive vegetation patterns on inland dunes and if so, what are main differences between vegetation in varying relief positions? (2) To what extent does topography involve the variability of microclimates and of soil properties, and how does the topographically-induced differentiation of these site conditions control vegetation patterns? We conducted interdisciplinary studies (applying floristic, pedological and microclimatic research techniques) on a naturally revegetated inland dune area situated on a military artillery training ground near Toruń, northern Poland. We investigated vegetation patterns with reference to three topographical position variants (north-facing slopes, south-facing slopes, and intra-dune depressions). We found distinct differences in vegetation characteristics covering the aforementioned topographical positions. This primarily concerned species composition of ground vegetation: Calluna vulgaris was dominant species on north-facing slopes, Corynephorus canescens on south-facing slopes, while Calamagrostis epigejos in intra-dune depressions. In comparison to dune slopes, the depressions were characterized by much higher biodiversity of vascular plant species. This followed the most favorable soil conditions for the existence of plants (higher moisture and nutrient pools) occurring in low topographical positions. However, tree succession was most advanced not in depressions, where the competitive impact of tall grasses on seedlings was recognized, but on north-facing slopes. Based on our results, we formulated some suggestions, which could be useful for both practical foresters to increase biodiversity of ecosystems and for practices that work on the fixation of dunes by restoring vegetation.

Natural disturbance, vegetation patterns and ecological dynamics in tropical montane forests

Abstract:Disturbance is a central process in forest dynamics, yet the role of natural disturbance in tropical montane forests (TMFs) has not been systematically addressed. We posit that disturbance in TMFs has a wider role than commonly acknowledged and its effects are distinctive because: (1) TMFs often have very low rates of productivity due to low resources, and so recovery from disturbance may be slow, (2) montane forests have marked environmental heterogeneity which interacts with disturbance, (3) a large percentage of TMFs are regularly exposed to high energy windstorms and landslides, and (4) TMFs contain a biogeographically rich mixture of tree species with divergent evolutionary histories that interact differently with different disturbance types. We reviewed the literature on natural disturbance in TMFs and found 119 peer-reviewed papers which met our search criteria. Our review shows that disturbance is widespread in TMFs with pronounced effects on structure, function, composition and dynamics. Disturbance is also evident in the ecology of TMF biota with clear examples of plant life-history traits adapted to disturbance, including disturbance-triggered germination, treefall gap strategies and resprouting ability. Important aspects of TMF disturbances are stochastic and site-specific, but there are broad patterns in disturbance type, frequency and severity along latitudinal, altitudinal and environmental gradients. Compared with the lowland tropics, TMF disturbances are more spatially structured, TMFs experience more disturbance types in a given area due to environmental complexity, and TMFs are much more prone to small-scale yet severe landslides as well the large and potentially catastrophic disturbances of cyclones, forest die-back and fire. On the whole, natural disturbance should assume a larger role in models of ecosystem processes and vegetation patterns in TMFs. An improved understanding of what creates variation in disturbance severity and post-disturbance recovery rates, how composition and diversity feedback on disturbance type and likelihood, and how global change will alter these dynamics are important priorities in future TMF ecology research.

Application of multisensoral remote sensing data in the mapping of alkaline fens Natura 2000 habitat

The Biebrza River valley (NE Poland) is distinguished by largely intact, highly natural vegetation patterns and very good conservation status of wetland ecosystems. In 2013⿿2014, studies were conducted in the upper Biebrza River basin to develop a remote sensing method for alkaline fen classification ⿿ a protected Natura 2000 habitat (code 7230) ⿿ using remote sensing technologies. High resolution airborne true colour (RGB) and color infrared (CIR) orthophotomaps, the laser scanning point cloud and thermal day and night images were obtained in August 2013 in the Biebrza River basin. At the same time, botanical studies were conducted in this area using conventional phytosociological methods. The random forest classification method was used to distinguish patches (phytocoenoses) of alkaline fens in the study area. The developed method of wetland identification has an accuracy of 91.5%. The night land surface temperature (LST) appears to have the greatest indicator potential. The obtained inventory results were compared with the results of the traditional habitat 7230 mapping method, carried out in 2011⿿2013 by another team of authors, under the Management Plan (MP, 2014). The obtained results suggest that the developed method has a wide application in nature conservation. Remote sensing methods are alternatives to traditional methods and can be used to identify alkaline fens on a larger scale.

Characterizing soil water dynamics on steep hillslopes from long-term lysimeter data

Summary Understanding soil water dynamics on hillslopes is of crucial importance to the prediction of floods and other hydrological events in mountainous catchments, to the identification of natural vegetation patterns, and to the optimization of agricultural land use. In principle, such information can be obtained from lysimeters, but most experimental lysimeter facilities have been installed on flat terrain. This study presents a long-term and high-resolution investigation of soil moisture, surface and subsurface flow using three large-scale lysimeters on a slope with 23.5° inclination on a landfill site in Karlsruhe, Germany. Data from a 10-year observation period were evaluated for this study, including weekly soil moisture data obtained by neutron probes, continuous discharge data from the land surface and several layers within the soil zone, and hydrometeorological data from a climate station. The results reveal (i) clear temporal and spatial patterns of soil moisture variations down to a depth of 250 cm, (ii) substantially higher discharge and faster percolation rates in the lower part of the lysimeter field, indicating significant downhill flow at various depths within the soil profile, (iii) characteristic threshold values for flow processes in the soil, associated with a hysteresis effect between soil moisture and flow processes. These results can be used as a basis of improved numerical models for the simulation of floods, soil moisture distributions, and vegetation patterns.

Using solid element roughness to control sand movement: Keeler Dunes, Keeler, California

Abstract The use of large roughness elements was investigated as a means to control sand transport and dust emissions in the Keeler Dunes to meet particulate matter air quality standards in Keeler, CA. 502 elements (straw bales) were arranged to mimic a natural vegetation pattern in a 50 × 100 m area in the dunes. The sand flux reduction target was 85%, compared to sand flux exterior to the array. Sand flux was initially reduced in the interior third of the array by ≈92% (±9%), exceeding the reduction target. Sand flux decreased exponentially with increasing distance into the array, reaching equilibrium at ≈110.5 element heights (≈42 m). Loss of effectiveness due to inundation of sand was 3.5% per month, falling below the target effectiveness after five months. The measurements of interior sand flux and rate of change of sand flux with increasing distance into the array corroborated the predictive ability of the empirical relationships used to design the roughness array. The established relationships are robust predictors for estimating how roughness modulates sand flux and can be used with high confidence for designing control strategies using this approach for roughness elements ≈0.3 m high for areas with low to modest topography.

Effects of soil erosion and seabird activities on chemical properties of surface soils on an oceanic island in Ogasawara Islands, Japan

To conserve indigenous natural ecosystem and help in the recovery of natural vegetation on Nakoudojima Island, which is a subtropical oceanic island in Ogasawara Islands in Japan, we clarified the mechanisms of the changes in soil chemical properties as affected by soil erosion and seabird activities on the island. Under grassland vegetation where influence of feral goat (exotic species) had been severe, the chemical properties of surface soils with a thickness of 5cm were variable even in a small area of 0.375km2; pH(H2O) value range between 4.6 and 6.9, total C content range between 0.36 and 5.62%, total N content range between 0.03 and 0.45%, exchangeable acidity range between 0.5 and 50mmolckg−1, and plant-available phosphate (Bray II P) range between 0.4 and 170mgP2O5100g−1. By clarifying soil profile characteristics under natural and disturbed vegetation and distribution patterns of these soils on the island, the changes in the soil chemical properties were reasonably assigned to the effect of soil erosion caused by feral goats for increased soil exchangeable acidity and decreased soil pH (mainly found in inland area) and to the effect of seabird activities for increased Bray II P and soil exchangeable acidity and decreased soil pH (mainly found in outer rim area with high altitude). It was also clarified that the high soil exchangeable acidity was significantly related to the low productivity of plant biomass for these plots (P<0.01). Soil erosion would have removed surface soils having weak acidity and exposed subsoils having strong acidity to the ground surface, resulting in inhibition of plant growth and delay of vegetation recovery. Based on the findings obtained in the present study, several options were proposed to stop soil erosion and to recover the vegetation, although careful preliminary examination would be necessary for applying them.

Last interglacial vegetation and climate history from the Portuguese coast

ABSTRACTWe examine the Atlantic maritime vegetation history from Praia Rei Cortiço, Portugal, to understand natural vegetation patterns and infer climatic conditions during the transition from the last interglacial to early glacial periods. Optically stimulated luminescence dating of quartz grains from sediments surrounding the 1.3‐m‐thick organic deposit date the section to within 120–89 ka. Pollen data were used to reconstruct the vegetation history and determine a range of possible past climates using an ensemble of seven modern analogue approaches. A five‐part environmental sequence transitioned from heath‐pine‐dominated communities, deciduous hardwood forests and pine forests to heathlands surrounded by steppe‐like environments. Mixed temperate and Mediterranean forest elements existed during the last interglacial period at Praia Rei Cortiço, suggesting a proximal limit to these floras. Abundant Fagus pollen (&gt;6%) suggests local beech populations existed within maritime forests of the Iberian Atlantic margin, representing a greater distribution of this genus during interglacial periods than has previously been recognized. Climate reconstructions indicate that variations in moisture availability may have been a major driver of the observed environmental changes.

Variation in NDVI values with change in spatial resolution for semi-arid savanna vegetation: a case study in northwestern South Africa

Natural vegetation and crop-greening patterns in semi-arid savannas are commonly monitored using normalized difference vegetation index (NDVI) values from low spatial resolution sensors such as the Advanced Very High Resolution Radiometer (AVHRR) (1 km, 4 km) and Moderate Resolution Imaging Spectroradiometer (MODIS) (250 m, 500 m). However, because semi-arid savannas characteristically have scattered tree cover, the NDVI values at low spatial resolution suffer from the effect of aggregation of near-infrared and red energy from adjacent vegetated and non-vegetated cover types. This effect is seldom taken into consideration or quantified in NDVI analyses of the vegetation of semi-arid lands. This study examined the effect of pixel size on NDVI values of land-cover features for a semi-arid area, using the 1000 m, 250 m and 10 m pixel sizes. A rainy season Système Pour l'Observation de la Terre 5 (SPOT 5) High Resolution Geometric (HRG) image at 10 m spatial resolution was utilized. Following radiometric and geometric preprocessing, the 10 m pixel size of the image was aggregated to 250 m and 1000 m to simulate imagery at these pixel sizes, and then NDVI images at the spatial resolution scales of 10 m (NDVI10 m), 250 m (NDVI250 m), and 1000 m (NDVI1000 m) derived from the respective images. The simulation of the NDVI250 m image was validated against a concurrent 16 day MODIS NDVI composite (MOD13Q1) image, and the accuracy derived from the validation was generalized to the NDVI1000 m image. With change from low to high spatial resolution, extreme magnitude NDVI values shifted towards the centre (mode) of the resulting approximately Gaussian NDVI distributions. There was a statistically significant difference in NDVI values at the three pixel sizes. Low spatial magnitude vegetation sites (woodland, cropland) had reductions of up to 28% in NDVI value between the NDVI10 m and NDVI1000 m scales. The results indicate that vegetation monitoring using low spatial resolution imagery in semi-arid savannas may only be indicative and needs to be supplemented by higher spatial resolution imagery.

Interactions between mangroves and exotic Spartina in an anthropogenically disturbed estuary in southern China

Cordgrass (Spartina alterniflora) was introduced to China in 1979 from the United States for reducing coastal erosion. It grows vigorously in China and has spread over much of the Chinese coast, from Leizhou Peninsula to Liaoning, a range of more than 19 degrees of latitude. On the southern coast of China, S. alterniflora has invaded mangrove-dominated habitats during the last two decades, but little is known about interactions between native mangroves and invasive S. alterniflora. We studied the distribution and competitive interactions between native mangroves and S. alterniflora in the Zhangjiang Estuary at four tidal sites along a salinity gradient: oligohaline upstream, mesohaline, polyhaline, and euhaline downstream. S. alterniflora occurred at all four sites, and several mangrove species occurred at all but the downstream euhaline site. S. alterniflora has invaded the estuary widely and has spread to the lower tidal margins of mangroves. It has not invaded mangrove areas with a closed canopy but has established in the mangrove zone where the canopy was opened by human disturbance. Ramets of S. alterniflora transplanted into the understory of mangrove stands with closed canopies died within 10 weeks, but 37.5% survived and grew well on open mud flats. S. alterniflora had virtually no competitive effect on mangrove seedlings planted at the upstream oligohaline site. However, S. alterniflora competitively reduced biomass of mangrove seedlings to 33% over a period of 14 weeks at the mesohaline and polyhaline sites where human disturbance has opened the mangrove canopy. In contrast, S. alterniflora marginally facilitated growth and survival of experimental seedlings at the downstream euhaline site. In China, mangroves occur along the coastline south of Whenzhou, but they have been severely disturbed and removed widely, mainly by mariculture activities. Natural vegetation patterns and our experimental results suggest that, without intervention, S. alterniflora could gradually replace these mangroves in mid-salinity regions of Chinese estuaries.

Sensitivity of natural vegetation to climate change in the Euro-Mediterranean area

This study explores the sensitivity to future climate change of natural vegetation patterns in the Euro-Mediterranean area under the IPCC-A1B emission scenario, using a dynamic vegetation model forced by fully coupled high resolution regional ocean-atmosphere model simula- tions. Our results indicate that a future warmer climate could not only affect the regional terrestrial carbon cycle, but also significantly impact vegetation dynamics. Specifically, by 2021-2050, temper- ate deciduous vegetation is projected to replace boreal and grass vegetation in parts of northeastern Europe, while in North Africa, simulations show a progressive desertification. The changes in domi- nant vegetation are mainly related to the increased drought stress on vegetation and the enhanced fire frequency. As for the carbon cycle, large increases in net primary production (NPP) are found in northern Europe resulting from higher temperature and precipitation, as well as higher atmospheric CO2 levels. In contrast, smaller NPP increases are found in the Mediterranean region, where reduced precipitation and increased temperature leads to an increase in drought years and, hence, water- stress for vegetation.

Patch vegetation and water redistribution above and below ground in south‐east Spain

AbstractTwo sites, one dominated by Anthyllis cytisoides and the other by Retama sphaerocarpa in south‐east Spain were instrumented to measure soil matric potential to a soil depth of 1 m and soil water content to 2·75 m depth within shrubs and grass areas. Soil cores and underground surveys were taken to estimate root length and soil texture, ground cover volume was measured and runoff traps were installed to estimate overland flow in grass and shrub areas. The outcome of the results was summarised as a conceptual model to describe the flow of water within patch vegetation, where the main dominating factor of patch vegetation was found to be the function of shrub canopy/root systems. The results illustrated that not only the dynamics of runoff/runon between grass and shrub areas were significant in redistributing rainfall, but also the morphology of shrub species caused significant differences to the accumulation and movement of water in shrub zones. A comparison of growth and flowering times of grass and shrub species showed that soil water availability for each species differs throughout the year. Such an understanding of water movement within patch vegetation of different species shows that sustainable management practices of semi‐arid areas must take into account not only natural vegetation patterns, but also the function of each plant type. Copyright © 2011 John Wiley &amp; Sons, Ltd.