Establishment and clonal spread of the alien shrub Rosa rugosa in coastal dunes—A method for reconstructing and predicting invasion patterns

Little is known about the rates of establishment and clonal spread of invasive plants on a landscape scale. This knowledge is necessary for reconstructing and predicting invasions, for example of the alien shrub Rosa rugosa. A series of aerial photographs (1986, 1999, 2002, 2004, 2006) were used to map the species in coastal dunes of north-western Denmark (2354 ha), and all R. rugosa patches (1321) were recorded with GPS in 2004 and 2007. The 2004 records were used to digitize 82–161 distinct patches on the photographs. The increase in patch sizes from the older to the younger photographs was used to calculate a lateral clonal spread rate (0.42 m year⁻¹). Relative area increment by clonal spread was 16.4% per year, decreasing exponentially with patch size due to constant clonal lateral spread. Based on the lateral spread rate, recursive negative buffers were introduced to determine when each patch became established. Applying the clonal spread rate to current patches allowed to quantify future distribution patterns. R. rugosa invaded the study area after 1949, and most patches established after 1989. For 1986–2004, the establishment rate was estimated as 0.02 patches ha⁻¹ year⁻¹. In 2004, the species had invaded 0.33% of the study area. If only clonal spread of existing patches is considered and assuming current environmental conditions and no management, the species will cover 3.9% by 2034. When including establishment of new patches, cover will increase to 9.5% in 2034. The advantages and limitations of the suggested extrapolation model are discussed.     

Bedform mobility and benthic oxygen uptake

A non-consumptive probe was used to measure DO concentrations in mobile sand dunes of the Tarawera River, New Zealand, which receives pulp-mill effluent. Net oxygen depletion rates were low in the top 5–10 cm (occasionally 10–20 cm) of the sediments which indicates that turbulent dispersion transports oxygen to these depths. Below 10–20 cm the net depletion rate was independent of depth which implies that the oxygen resupply rate was negligible. Minimum DO concentrations were invariably found at the upstream (scouring) face of the dunes indicating that advection through the sediments was negligible. A simple analytical model showed that dune turnover explained 30% of the observed river deoxygenation rate. Benthic uptake arising from dune turnover was uniform down the river because an increase in dune height along the river was offset by a decrease in river DO. This helps explain why the river deoxygenation rate is uniform. A fragile layer of fluidized sediment covered the crests of each dune. It was inferred that oxygen uptake in this layer explained 60% of the river deoxygenation rate but an improved understanding of oxygen dynamics within the fluidized layer is required. In other mobile-bed rivers it is likely that dune turnover will be important in determining the benthic mass transfer rate.     

Blowouts in coastal foredunes

Foredune blowouts within many embayments along the south coast of South Africa are traditionally believed to be caused by human activities and the result of onshore winds reducing vegetation cover and developing landward migrating patches of bare sand. These bare areas are not blowouts sensu strictu, however, and are more likely the elongated horns of barchan dunes formed across the direction of the dominant winds. Blowouts of this type have been present on the foreshore of Algoa Bay for more than 100 years and long before present-day human pressures could be the possible causal factor. They are not likely to present major management problems provided buildings are not constructed within them or closely behind them. Where necessary, vegetation cover should be maintained either by keeping people out of the dunes or by implementing revegetation options. Some mechanical sand relocation may occasionally be a helpful short-term management solution.     

Effect of vegetal cover on runoff and soil erosion under light intensity events. Rainfall simulation over USLE plots

The erosive power of frequent light rainfalls is studied in this paper. Field experiments of simulated rainfall (Intensity, 21 mm h(-1) and kinetic energy, 13.5 J m(-2) mm(-1)) were conducted over 8 bounded USLE plots (80 m(2) each) with a slope of 10%. In 4 plots the soil was almost bare (<4% vegetation cover); the other 4 plots had almost full cover with natural vegetation in one year. Runoff and sediment yield was recorded. The results revealed the efficiency of vegetation cover reducing runoff and sediments. Runoff and sediments were negligible in covered plots. Therefore, in bare plots, although sediment yield was generally low, averaging 74+/-43 kg ha(-1), the mean of runoff achieved a coefficient of 35%, this magnitude has to be taken into consideration in this region verging on aridity. Rains around 13.5 J m(-2) mm(-1) of kinetic energy are quite frequent in the study area (34% of recorded rains en 12 years). If we would consider the usual lower limits from the literature, we would be ignoring an important percent of natural rainfall episodes.     

Post-mining rehabilitation of coastal sand dunes in Zululand South Africa

In the process of dredge mining, employed since 1977 on the Zululand coast, heavy minerals are extracted from the dunes after the complete removal of the existing vegetation. The tailings are then reshaped to approximate their original contours, covered with topsoil and revegetated with a cereal cover crop, together with indigenous seeds of long-lived (woody) species. The existence of stands of different ages over a recorded period provided an opportunity to study changes in species composition and vegetation dynamics. Five random 10 × 10m quadrats were sampled in stands of age 4, 5, 7, 8, 9, 10, 11 and 12 years respectively, and cover data were used for multivariate analysis using TWINSPAN and DECORANA. Importance values of each species, and total and mean species richness were also calculated. Pre-mined and mined soil samples were analysed for trace elements, organic matter and pH. Recently rehabilitated areas of 4 to 5 years were dominated by Acacia karroo, but species richness showed a progressive increase with age of rehabilitated stands, with more woody species in the older stands and a slight decline in dominance of A. karroo. TWINSPAN classified older and younger stands into distinct groups which were related to a chronological succession gradient, also shown by the DECORANA ordination. Some soil nutrients of rehabilitated areas compared favourably with the pre-mined topsoil and subsoil, but percentage organic matter content was still higher in natural dune forests. Increases in soil nutrients suggest that nutrient retention and the establishment of substantial soil flora and fauna are occurring, providing evidence for the sustainability of the soils. From this study it appears that successional changes follow the facilitation pathway, and rehabilitation will eventually lead to the restoration of the dune forest.     

Assessing landscape change and biodiversity values of the Middle Vistula river valley, Poland, using BIO-SAFE

This paper deals with the relation between legally protected biodiversity and riverine ecotopes and with the assessment of biodiversity values of the Middle Vistula river valley (Poland). Furthermore, it describes the effects of landscape change on spatial distribution of ecotope patches and biodiversity values in Kazimierski Landscape Park. Biodiversity values were calculated using BIO-SAFE, a model meant to quantify biodiversity and to value ecotopes based on legally protected species. Dissimilarity indices depict high uniqueness of ecotope types regarding their species assemblages (e.g., river dunes, banks and bars). The actual biodiversity values of the river valley in Kazimierski Landscape Park are high in comparison with floodplains of lowland rivers in Western Europe. GIS analyses of remotely sensed ecotope maps show remarkable differences in number, acreage and patchiness of ecotopes for the years 1953 and 2003. The total number of patches increased by almost 44%. Side channels and floodplain lakes became fragmented. The average and total surface area of bush, forest and arable land increased, but decreased for bare soil, pioneer vegetation and grassland. These landscape changes indicate natural vegetation succession, intensification of agriculture and progressive impacts of river regulation. The Vistula river valley still represents high biodiversity values for higher plants, birds, herpetofauna and fish. However, current landscape changes negatively affect potential values for protected and endangered species. Assessments with BIO-SAFE can help to balance biodiversity conservation, river management and landscape planning.     

Dynamics and succession of coastal dune vegetation in the Eastern Cape, South Africa

Mobile or partially vegetated dunefields dominate the Eastern Cape coastline, with dune slacks being conspicuously well vegetated. Earlier studies on the dynamics of these habitats suggested that greater soil moisture, reduced sand movement and salt spray favoured the establishment of more mesic species. Since an understanding of these successional processes has important management implications, more detailed studies to firstly describe and then interpret the successional relationships between various plant communities were undertaken. From a survey of 152 relevés at 62 sites, seven coastal communities were recognised by TWINSPAN. This separation appeared to be based on the location, habitat and successional stages of the communities, and ordination by DECORANA showed that in any one area these communities were linked to a succession gradient from pioneer to “climax”. A more detailed investigation of the role played by dune slacks in this succession was undertaken at Kleinemonde. Six communities were separated by TWINSPAN. Pioneer communities of the foredunes had low cover and diversity, being dominated by herbs. Young dune slacks had low cover but moderately high diversity, with sedges and grasses dominating. Old dune slacks had a greater total mean cover, and shrubs were more abundant. Bushclumps were physiognomically more complex than dune slacks, with greater total mean cover, diversity and life form composition. Thicket margin communities were structurally similar to bushclumps, but floristically more complex. Dune thicket was the most physiognomically and floristically complex community sampled. Multivariate analysis revealed a distinct gradient of plant communities with increasing distance (age) from the sea, namely from Pioneer to Young Slack, Old Slack, Bushclump, Thicket Margin and Dune Thicket communities. With age, species richness, cover, diversity, number of life forms and structural complexity of the communities all increased. Importance value curves for 12 diagnostic species highlighted the distribution of these key species along the chronosequence. Pioneer species were restricted to the beginning, and dune slack species the central portion of the chronosequence. Hardy species had a wide distribution, but dune thicket species only appeared later. These trends appear to represent directional changes along a successional sequence as proposed in an earlier model, and the mode of transition between them relies heavily on autogenic changes. Dune slacks play an important role in this facilitation by acting as centres of diversity within the sparsely vegetated dunefield, and the foredunes by protecting dune slacks from salt spray and sand movement. Therefore, the role of foredunes and dune slacks must be considered in the management of the South African dune landscape, as they contribute significantly to the dynamic equilibrium of partly vegetated dunefields. Management should therefore be aimed at protecting these habitats.     

Preliminary observations on managing and reclaiming frontal dunes within the Durban municipal area

The Bluff dunes, located within the Durban (South Africa) municipal area, have become increasingly degraded as a consequence of human pressures over the last quarter century. The resulting localised wind-blown sand pollution of roads and storm drains necessitated a dune reclamation project involving a multi-disciplinary team of Parks managers and engineers. An effective solution was provided by a combination of physical sand/wind screens, and irrigation aided revegetation of dunes employing several locally occurring indigenous plant species. Liaison with the community at all development phases has allowed for an effective solution which is practical, cost-effective, environmentally sound and socially accepted. This paper outlines the methods employed and steps taken in dune revegetation on the Bluff, and discusses the practical problems encountered, together with the solutions. The system follows a series of steps that any land manager can use to maintain a cover over the sand. It has a multi-disciplinary approach, so that engineers, ratepayers and scientist can all contribute to the process.     

Morphology of dunes of the Coromandel coast of Tamil Nadu: A satellite data based approach for coastal landuse planning

The 1000 km long coast of the Tamil Nadu state of India forms part of the Coromandel coast. The dunes which consist of Quaternary to Recent sediments are a major part of the various coastal landforms such as lagoons, estuaries, bays, beaches, spits, bars, deltas, marshes, tidal flats, mud flats, etc. The dunes occupy a large part of the Coromandel coast and have a key role in the morphology and landuse planning of this coastal zone. These dunes are an important source of ground water, heavy minerals, silica (glass) sands and are also potential avenues for social forestry, mixed forests, plantations and recreational resorts.As a first step in coastal zone management, mapping of these dunes and study of their relation to landuse is to be carried out. Their large extent and widespread habit make conventional mapping techniques difficult to use. Hence, the Indian Remote Sensing Satellite (IRS-1A) imagery has been used to map them. This paper gives an account of mapping these coastal dunes using IRS-1A imagery, a study of their morphology, the related landuse/land cover details, and also suggestions for optimal landuse management techniques.     

Human activity and potential impacts on dune breeding birds in the Alexandria coastal Dunefield

Human use of coasts has increased considerably with increasing demand for recreational experiences, increased availability of off-road vehicles (ORVs) and population increase. Besides impacts on dune morphology and flora, humans and ORVs also affect the fauna. The Alexandria Dunefield in Algoa Bay comprises a 50 km sandy beach backed by a 2.1 km wide strip of dunefield. The dunefield is largely conserved, but access to the beach is allowed under permit, and the beach is heavily utilised by fishermen and recreational ORV drivers. The area is also important for dune breeding birds. Beach and dune use by fishermen and other users was quantified by recording their position relative to the high water mark and along a 20 km stretch of beach, and through analysis of access permits and angling competition data. An increase in vehicle use in the area was observed. An indication of human perception of the area was obtained by questionnaires. Eighty percent of human activity was concentrated in 50% of the study site where the highest concentration of dune breeding birds nest. Sixty percent of the vehicles recorded, were on or above the high water mark (in the dunes). Of the beach-users interviewed, 74% suggested that only registered vehicles should be allowed on the beach. Most (80%) anglers had no problem determining the position of the high water mark. There is an overlap in area and seasonal use between beach-users and breeding birds. With specific areas along the beach being heavily impacted and vehicles utilising the area above the high water mark the potential for impact on the fauna and flora of these areas is high. There is a need to educate beach users as to the vulnerability of dune systems and to develop appropriate management guidelines to minimise the impacts of beach users on the dune fauna.     

Remaining tree species from the indigenous vegetation of Ankara, Turkey

The city of Ankara is located in the geographic centre of Anatolia, Turkey. In the state of nature, Anatolia was covered with forests. Due to the destructive effects of civilisations passing through Anatolia over the centuries, the forest vegetation was gradually transformed to a steppe formation. After it became the capital city, a rapid planned urbanisation process was initiated in Ankara. In the first development plan, efforts were concentrated on the south axis of the city, which harbored the greatest concentration of indigenous plant cover in the valleys.In 1974, the embassy gardens and parks on the north–south axis were declared a “Natural Conservation Area”. Despite the conservation act, change and denuding of indigenous vegetation continued all along the axis due to highly increasing development. However, these conservation areas still include tree species from the indigenous vegetation. In this study, the presidency gardens, the embassy gardens and parks in Ankara that were declared a “conservation area” were evaluated in terms of the remaining tree species from the indigenous plant cover. The study aims to indicate the level of conservation of natural habitat in Ankara and to determine whether the concept of “Natural Conservation Areas” includes the protection of biodiversity or not. Moreover, the research results aim to reveal still existing tree species of indigenous vegetation, which will enlighten us regarding future landscape planning in Central Anatolia. Trees were examined by age, height and exposition. The results show that remaining indigenous tree species of the study area grow along the former ncesu River and that the terrain on which the trees stand is mostly exposed to the southwest and southeast. The indigenous tree species which do not exist in the study area are scattered in valleys along the river trails or on the hills of Ankara’s rural lands.     

Analysis of Eastern Mediterranean Oak Forests Over the Period 1965–2003 Using Landscape Indices on a Patch Basis

Although Eastern Mediterranean forests have been exploited for many years, the changing trends in the past 40 years require detailed investigations. Forests in the coastal zone of Lebanon are witnessing major changes mainly because of chaotic urbanisation. The study area at the coastal zone of Lebanon has 96% of its forest cover under oak coppice. The aim of this study is to investigate the applicability of landscape indices on oak forests especially their ability to detect changes between 1965 and 2003. It uses forest canopy closure as another indicator of forest destruction. The 1965 forest map was first checked for its accuracy before being used to extract patch delineations and canopy closures. Landcover types for 2003 were obtained by classifying a SPOT 5 satellite image. FRAGSTATS software was utilised on the 1965 map on a patch basis to calculate patch shapes and sizes. These indices and canopy closures data were investigated for correlation purposes with patterns of forest loss. The edge distances between forest patches in 1965 and new forest patches in 2003 were computed to analyze regeneration processes. Results show that although older forest patches have shown a 48% loss in area, total forest area reached 83%. Abandoned agricultural lands have become new forest. Smaller forest patches (< 40 ha) showed greater losses than large ones. Small and open forest patches recorded greater loss than large and dense patches. Shape indices show no correlation with forest loss. Clearance for agriculture covered 30% of the pre-existing forests, while urban developments accounted for just 4% of forest loss. This research highlights the great need for comprehensive studies of forests using landscape analyses. Such analyses help managers develop practical and relevant conservation measures.     

Lowering the outdoor temperature in high-rise high-density residential developments of coastal Hong Kong: The vegetation influence

This paper investigates the impact of on-site variables on the influence of vegetation in lowering outdoor temperature. The study uses six critical on-site variables such as surface albedo, sky view factor, altitude, shrub cover, tree cover and average height to floor area ratio to carry out analysis in five data sets. The climatic parameters and physical characteristics were measured and surveyed, respectively in 216 stations in high-rise high-density residential developments of coastal Hong Kong. The data set is mainly categorised into peak summer clear sky days (PSCS-days), peak summer partially cloudy days (PSPC-days) and late summer days to address the issues related to cloudy sky conditions in Hong Kong. The trend analysis shows that at a lower sky view factor, ranging from 0.1 to 0.25, shrub cover as low as 10–15% in a 1000 m² open area is more effective in reducing outdoor temperature than the same level of tree cover in a location with a higher sky view factor (0.4 or above). The regression models used in this study were able to explain the influence of on-site variables on vegetation in lowering the outdoor temperature within the respective urban settings. In high-rise high-density environments, on-site variables such as sky view factor and altitude have a substantial impact on the influence of vegetation in lowering outdoor temperature. However, off-site variables such as high urban density and anthropogenic heat could negate the behaviour of sky view factor and altitude. The study suggests that increasing the tree cover from 25% to 40% in the pocket parks in coastal area residential developments of Hong Kong could reduce daytime urban heat island intensity (UHI) by further 0.5 °C.     

Radionuclide transfer to invertebrates and small mammals in a coastal sand dune ecosystem

International intercomparisons of models to assess the impact of ionising radiation on wildlife have identified radionuclide transfer assumptions as a significant source of uncertainty in the modelling process. There is a need to improve the underpinning data sets on radionuclide transfer to reduce this uncertainty, especially for poorly-studied ecosystems such as coastal sand dunes. This paper presents the results of the first published study of radionuclide transfer to invertebrates and small mammals in a coastal sand dune ecosystem. Activity concentrations of ¹³⁷Cs, ²³⁸Pu, ^239 + 240Pu and ²⁴¹Am are reported for detritivorous, herbivorous, carnivorous and omnivorous biota. Differences in activity concentrations measured in the sand dune biota are related to the trophic level of the organisms and the influence of sea-to-land transfer is apparent in the food chain transfer observed at the site. There are notable differences in the concentration ratios (CRs) calculated for the sand dune biota compared to other terrestrial ecosystems, especially for the small mammals which have CRs that are two orders of magnitude lower than the generic terrestrial ecosystem CRs published by the recent EC EURATOM ERICA project. The lower CRs at the sand dunes may be due to the influence of other cations from the marine environment (e.g. K and Na) on the net radionuclide transfer observed, but further research is required to test this hypothesis.     

Thermal performance of a vegetated cladding system on facade walls

An experimental approach is used to assess the effect of vegetation on the thermal performance of a vertical greening system, which comprised of turf-based vertical planting modules, on an elevated facade wall of a public housing apartment. Despite temperature fluctuations in the various compartments external and internal to a concrete wall, the vegetated cladding reduced interior temperatures and delayed the transfer of solar heat, which consequently reduced power consumption in air-conditioning compared with a building envelope with bare concrete. Vegetation cover led to a different pattern of temperature fluctuations on wall surfaces, which may affect the comfort of occupants even after sunset. The cooling effect which was closely associated with the area covered by living plants and moisture in the growth medium, demonstrated the value of maintaining a healthy vegetation cover beyond visual amenity. Marked variation in moisture distribution along the vertical profile of the growth medium highlighted a concern rarely addressed in planting on ground. Substrate moisture measured at randomly selected locations would underestimate the water stress in some plants and impair their survival.     

城市裸土地景观生态效应研究

研究了城市裸土地的分类、景观生态效应和景观生态修复方法,将其划分为季节性裸土地、点状裸土地和面状裸土地三个类别,探讨其对城市景观、生物多样性、环境质量和人体健康等的负面效应,提出了植物种植、有机无机物覆盖和硬质铺装等景观生态修复方法。     

The integration of bioclimatology in an environmental study

The environmental study concerned with the planning scheme for Kenitra (Morocco) includes a biological evaluation, a landscape evaluation, and a bioclimatological approach to define the constraints and planning potentialities.Ground occupation and forms of vegetation have been mapped (200 km²) and climatic data collected along traverses through the investigated area.The high littoral dunes reduce the oceanic influence. A slight heat island has been observed and comfortable zones identified during the warm season. The most comfortable areas have abundant shade, abundant vegetation, available water, and light movements of air.Integration of the biotic, scenic and bioclimatic observations allow a crucial examination of, and improvement in, the urban arrangement, and allow proposals to be made concerning unification of the landscape so that authenticity may be preserved and qualities developed.     

Landscape effects of environmental impact on bay-area wetlands under rapid urban expansion and development policy: A case study of Lianyungang,China

This paper presents a synthesis of rapid landscape change and regional environmental dynamics in the Lianyungang bay area from 2000 to 2006 based on remote sensing data. We quantified the annual rate of urban land-use change in the study area using classified Landsat TM (2006-05-20) and ETM⁺ (2000-09-16) images. The classified images were used to generate maps of urban expansion and salt wetlands degradation, and landscape metrics were calculated and analyzed spatiotemporally across class and landscape level for each year. Results indicate that the Lianyungang bay area has a widespread urban–rural interface with rapid land-use changes, urban expansion and wetland degradation. Rapid increases in urban built-up land, which were often associated with large-scale salt wetlands degradation, have been prominent since 2005 when the eastern coastal development policy was implemented.     

Three decades of urban growth in the city of Shiraz, Iran: A remote sensing and geographic information systems application

Although remotely sensed images have been used to study urban growth patterns the world over, very few studies have employed these methods to examine the growth of Iranian cities. Shiraz is perhaps the most important city in the southern part of Iran and, thus, was selected for this study. We used satellite images of the study area from the period between 1976 and 2005, and population censuses of Shiraz. By applying classification methods to the satellite images four main types of land use were extracted: water, built-up, vegetation and bare land. Then, the area coverage for all the land use types at different points in time were measured and coupled with population data. The results demonstrate that, over the entire study period, development in Shiraz cannot be characterized as sprawl. Since 2000, however, one can see evidence of sprawl. These results are also supported by calculations using Shannon’s entropy. A further finding is that vegetation growth did not keep pace with that of population or the built-up area; more recently, vegetation has greatly declined. It is advisable that future plans for the city give serious consideration to the preservation of available vegetation and, when possible, the restoration of vegetation that was destroyed in the past.     

Implications of patterns of carbon pools and fluxes across a semiarid environmental gradient

Landscape scale environmental gradients present variable spatial patterns and ecological processes caused by climate, topography and soil characteristics and, as such, offer candidate sites to study environmental change. Data are presented on the spatial pattern of dominant species, biomass, and carbon pools and the temporal pattern of fluxes across a transitional zone shifting from Great Basin Desert scrub, up through pinyon–juniper woodlands and into ponderosa pine forest and the ecotones between each vegetation type. The mean annual temperature (MAT) difference across the gradient is approximately 3°C from bottom to top (MAT 8.5–5.5) and annual precipitation averages from 320 to 530 mm/yr, respectively. The stems of the dominant woody vegetation approach a random spatial pattern across the entire gradient, while the canopy cover shows a clustered pattern. The size of the clusters increases with elevation according to available soil moisture which in turn affects available nutrient resources. The total density of woody species declines with increasing soil moisture along the gradient, but total biomass increases. Belowground carbon and nutrient pools change from a heterogenous to a homogenous distribution on either side of the woodlands. Although temperature controls the seasonal patterns of carbon efflux from the soils, soil moisture appears to be the primary driving variable, but response differs underneath the different dominant species. Similarly, decomposition of dominant litter occurs faster at the cooler and more moist sites, but differs within sites due to litter quality of the different species. The spatial pattern of these communities provides information on the direction of future changes. The ecological processes that we documented are not statistically different in the ecotones as compared to the adjoining communities, but are different at sites above the woodland than those below the woodland. We speculate that an increase in MAT will have a major impact on C pools and C sequestering and release processes in these semiarid landscapes. However, the impact will be primarily related to moisture availability rather than direct effects of an increase in temperature.