Landscape structure influences continental distribution of hantavirus in deer mice

We hypothesized that landscape structure affects movement of individuals through the landscape, which affects the rate and pattern of disease transmission. Based on this hypothesis, we predicted a relationship between landscape structure and disease incidence in spatially structured populations. We tested this prediction for hantavirus incidence in deer mice (Penomysens moniculatus), using a novel index of habitat fragmentation for transect data. A series of four stepwise logistic regression analyses were conducted on serological and ecological data from 2837 mice from 101 sites across Canada. The significant variables, ranked in decreasing order of size of their effect on virus incidence were: human buildings, landscape composition (amount of deer mouse habitat in the 1-km radius landscape surrounding each site), landscape configuration (fragmentation of deer mouse habitat in the 1-km radius landscape surrounding each site), mean annual temperature, and seasonal variation. Our results suggest that epidemiological models should consider not only the demographic structure of the host population, but its spatial structure as well, as inferred from landscape structure. Landscape structure can have a greater effect on the pattern of distribution of a virus in its host population than other ecological variables such as climate and seasonal change. The usefulness of landscape data in epidemiological models depends on the use of the appropriate spatial scale, which can be determined empirically. Epidemiological models with a spatially structured host population can benefit from the explicit consideration of landscape structure.     

OUTENIQUA — A computer model to simulate succession in the mixed evergreen forests of the southern Cape,South Africa

A succession model for mixed evergreen forests of the southern Cape, South Africa, called OUTENIQUA, was developed based on one for subtropical rain forest in New South Wales, Australia. The model simulates the regeneration, growth and mortality on a 0.04 ha plot using an individual-tree based modeling approach to forest succession. The OUTENIQUA model was tested on its ability to simulate species dynamics of the forest stand used for its development, as well as on independent data from a neighboring stand and not used for the model derivation. The model is used as a research tool to summarize published and unpublished knowledge on the southern Cape forests and to highlight aspects where knowledge is insufficient. The development of the model represents a test of an individual-tree gap model as a simulation tool for use in management and directing research in subtropical and tropical forests.     

Current and potential carbon stocks of trees in urban parking lots in towns of the Eastern Cape,South Africa

Greening of shopping centre parking lots is a potentially important strategy that can contribute to urban carbon mitigation efforts, improve aesthetics and the shopping experience of consumers, whilst adding to urban biodiversity. Twenty-eight shopping centre parking lots in six Eastern Cape urban centres, South Africa, were sampled to determine tree species composition, density and annual carbon sequestration potential. The best case parking lot found during the study was used as a benchmark to display the difference between current tree density and above-ground carbon stocks relative to the potential optimum. The highest tree density was 66 trees ha^?1, whereas the average density across all sampled parking lots was less than half that (27.2 ± 22.6 trees ha^?1). The average annual carbon sequestration potential per parking lot was 1390 ± 2503 kg ha^?1. Planting density was positively related to annual sequestration rates, whilst parking lot age and the mean annual rainfall of the town had no influence. Mean tree species richness per parking lot was 2.3 ± 1.8 species, with a positive relationship to parking lot size, but not to mean annual rainfall of the site. The majority of trees (62.5%) in parking lots were alien species, although newer parking lots had significantly greater proportions of indigenous species. There was no difference in mean annual carbon sequestration rate per tree between indigenous and alien trees species. Low tree densities and small parking lot areas constrained the potential for earning carbon credits from trees in parking lots. Nonetheless, planners and designers need to be more aware of the potential contribution of trees towards urban sustainability.     

Landscape diversity in a conservation area and commercial and communal rangeland in Xeric Succulent Thicket,South Africa

Landscape Ecology - Nature reserves in Xeric Succulent Thicket of South Africa contain a greater diversityof wildlife and correspondingly a greater diversity of disturbance agents thanadjacent,...     

Landscape history,time lags and drivers of change: urban natural grassland remnants in Potchefstroom,South Africa

Context

The history of the landscape directly affects biotic assemblages, resulting in time lags in species response to disturbances. In highly fragmented environments, this phenomenon often causes extinction debts. However, few studies have been carried out in urban settings.

Objectives

To determine if there are time lags in the response of temperate natural grasslands to urbanization. Does it differ for indigenous species and for species indicative of disturbance and between woody and open grasslands? Do these time lags change over time? What are the potential landscape factors driving these changes? What are the corresponding vegetation changes?

Methods

In 1995 and 2012 vegetation sampling was carried out in 43 urban grassland sites. We calculated six urbanization and landscape measures in a 500 m buffer area surrounding each site for 1938, 1961, 1970, 1994, 1999, 2006, and 2010. We used generalized linear models and model selection to determine which time period best predicted the contemporary species richness patterns.

Results

Woody grasslands showed time lags of 20–40 years. Contemporary open grassland communities were, generally, associated with more contemporary landscapes. Altitude and road network density of natural areas were the most frequent predictors of species richness. The importance of the predictors changed between the different models. Species richness, specifically, indigenous herbaceous species, declined from 1995 to 2012.

Conclusions

The history of urbanization affects contemporary urban vegetation assemblages. This indicates potential extinction debts, which have important consequences for biodiversity conservation planning and sustainable future scenarios.

     

The extent and perceptions of vandalism as a cause of street tree damage in small towns in the Eastern Cape,South Africa

Street trees are important foundations of urban sustainability due to the ecosystem services that they provide society and the environment. However, street trees are vulnerable to vandalism and damage, especially when small, which constraints the flow of benefits they provide and also increases the costs of planting programmes. Despite being a common phenomenon, there is limited knowledge regarding the extent of vandalism and the reasons for it. Here we seek to understand the causes and extent of street tree damage in eleven small Eastern Cape (South Africa) towns and to assess the perceptions of residents and officials. The condition of newly planted street trees was assessed in each town and residents were interviewed in the two towns with the highest number of newly planted street trees. Almost half (42%) of recently planted street trees were totally snapped, ranging between 0% and 63% per town. There was no difference in the prevalence of trees being snapped between those with protective structures and those without. Each town used different structures around newly planted street trees, but in only two towns were all the structures intact. The prevalence of damage declined with increasing trunk thickness and increasing town size. According to residents, boredom, misbehaviour, lack of appreciation of trees and collection for wood were the main factors for tree vandalism by people along with damage by livestock. Ward councillors recognised the presence of vandalism, but indicated that it was not a priority topic in their ward meetings. Suggestions by residents to prevent vandalism included: planting in sensible areas, re-designing the protective structures, re-locating livestock and engendering community participation and ownership in all aspects of street tree planting.     

Trees stocks in domestic gardens and willingness to participate in tree planting initiatives in low-cost housing areas of the Eastern Cape,South Africa

Increasing human populations and rapid urbanization in sub-Saharan Africa have prompted the development and maintenance of urban green infrastructure, including urban trees for sustainability, human wellbeing, liveability and climate resilience. However, there are still insufficient amounts and large inequities in the distribution of trees between and within towns and cities of the Global North and South. In South Africa, urban green space planning and planting are encoded in several policies at national level. However, these policies are rarely translated into specific guides, standards or actions, and consequently disparities in urban trees and green space distribution persist. This study assessed the prevalence of urban trees in domestic gardens in low-cost housing areas (LCHAs) of eight small to medium-sized towns in the Eastern Cape province of South Africa and examined residents’ perceptions in this regard. This was done via surveys with 800 households in old and recently developed LCHAs. The results revealed that most households (52 %) had at least one tree in their yard, with more households in the older neighbourhoods (60 %) reporting having trees than in the newer ones (44 %). Most of the trees (66 %) had been deliberately planted as opposed to natural regeneration. Experience of formal urban tree planting programs was low, but 75 % of residents expressed willingness to participate in the future, preferably in tree planting and maintenance. Urban green spaces and trees cannot be an afterthought in the development of sustainable human settlements, and municipal plans should reflect tangible commitments in this regard. Meeting goals for greener LCHAs requires the involvement of local residents, and for municipal authorities to be receptive to the wishes of residents and willingness to green their residential areas.     

Landscape ecology of uncultivated lowlands in Central Spain

The relationship between groundwater and landscape in representative areas of the Spanish plateaux is discussed, with special attention given to the Douro River basin. The study focusses on the transference of water and matter that is conditioned by groundwater flow systems, and also on water bodies, wet meadows, marshes, saline soils under their influence.These factors are of great importance in semiarid areas. Using photointerpretation, interviews, vegetation plots, water samples from wells and springs and soil samples, and the results of data processing (principal component analysis, shared information) we find that hydrological processes are the main controlling factor in the ecological function and variation of uncultivated lowlands. These processes include the alternation of recharge and discharge areas, the geochemical evolution of groundwater and the independent flows of the regional system.The landscapes in recharge and discharge areas are compared, as well as the influence of the evolutionary stage of the groundwater in the latter areas (glycophyte or halophyte vegetation). After observing the ecological importance of these aquifer discharges systems, the causes of their accelerated transformation are analyzed.     

Landscape ecology: Population genetics at the metapopulation level

Distribution of genetic diversity in a landscape depends on both within and among population processes. Selective pressures within populations have traditionally been studied by population genetics, which usually assumes that populations are at equilibrium. However, when selection pressures within and among populations are different, landscape processes are required to define an equilibrium (landscape being defined as the habitat of a set of populations called a metapopulation, and populations will differ depending on their situation in the landscape, i.e. their age and the state of neighboring populations). We examine reproduction systems and life history traits, for which variation depends on landscape processes. Predictions of their states in a metapopulation are drawn from theoretical models, and confronted to observations collected in natural populations.     

Using a multifaceted approach to reveal avian community responses to natural and anthropogenic effects in a fragmented Southern Mistbelt Forest system,South Africa

Landscape Ecology - Forest loss and fragmentation are major drivers of biodiversity decline globally. However, with the widely recognised notion that biodiversity is multifaceted, few studies have...     

Carbon sequestration estimates of indigenous street trees in the City of Tshwane,South Africa

Amelioration of global warming presents opportunities for urban forests to act as carbon sinks, and thereby could possibly be included in the potential future carbon trade industry. The City of Tshwane Metropolitan Municipality provided a strategy in 2002 to plant 115,200 indigenous street trees in the period 2002–2008. These trees hold a monetary carbon value in their potential future growth. In order to calculate the carbon sequestration potential, the growth rates of Combretum erythrophyllum, Searsia lancea and Searsia pendulina were determined. Combined species growth regressions of C. erythrophyllum–S. lancea and S. lancea–S. pendulina are also presented. Combretum erythrophyllum has the fastest growth rate while those of S. lancea and S. pendulina are slower. The results from growth regression relationships were used in a generic allometric biomass regression to calculate the carbon sequestration rate of each species, which was extrapolated to determine the total quantity of carbon to be sequestrated by the street trees over a 30-year period (2002–2032). It is estimated that the tree planting will result in 200,492 tonnes CO₂ equivalent reduction and that 54,630 tonnes carbon will be sequestrated. The carbon dioxide reductions could be valued at more than US$ 3,000,000. But this estimate should also be viewed in the context of the limitations presented in this study. This illustrates that when future carbon trade becomes operational for urban forests these forests could become a valuable source of revenue for the urban forestry industry, especially in developing countries.     

浅谈西方现代景观设计的主要倾向

西方现代景观经过近一个世纪的发展,形成了有别于传统园林的风格和形式。受到现代景观思想与设计手法的广泛影响,景观从传统中逐渐走了出来,并形成了现代园林一些明显与传统形式不相同的特征,该文从5个方面谈论了西方现代景观设计的主要倾向。     

Quantifying spatiotemporal drivers of environmental heterogeneity in Kruger National Park,South Africa

Context

Environmental heterogeneity is considered an important mechanism of biodiversity. How environmental heterogeneity is characterised by the compositional, structural and functional variation of biotic and abiotic components is a central research theme in conservation.

Objectives

We explore how environmental heterogeneity relates to the underlying physical landscape template and how that relationship changes over space and time. We examine how, in some areas, environmental heterogeneity may also be driven by dynamic ecological processes, and how this relates to patterns of plant species richness.

Method

We use local geographically weighted regression to spatially partition environmental heterogeneity, measured as Landsat spectral variance, into the portion explained by stable physical landscape properties (R²) and the portion unexplained (1?R²) which we term landscape complexity. We explore how this relationship varies spatially and temporally as a function of dynamic ecological processes such as rainfall and season in Kruger National Park, as well as plant species richness at landscape scales.

Results

The significance and direction of relationships varied over space and time and as a function of rainfall and season. R² values generally decreased in higher rainfall summer months and revealed patterns describing the importance of known stable factors relative to unknown dynamic factors. Landscape complexity (1?R²) explained over 70 % of variation in species richness.

Conclusions

Rainfall and seasonality are important drivers of environmental heterogeneity. The spatial arrangement and magnitude of model agreement helped disentangle the relative influence of the physical landscape template on environmental heterogeneity. Given the high correlation with species richness, landscape complexity provides complementary guidance to biodiversity research and monitoring prioritization.

     

Landscape ecology: a framework for integrating pattern and process in river corridors

Investigations of European floodplain rivers demonstrate how landscape ecology can provide an effective framework to integrate pattern and process in river corridors, to examine environmental dynamics and interactive pathways between landscape elements, and to develop viable strategies for river conservation. The highly complex and dynamic nature of intact river corridors is particularly amenable to a landscape ecology perspective. Analysis of spatial patterns has provided considerable insight into environmental heterogeneity across river corridors and is an essential prelude to examining dynamic interactions. For example, data from aerial photographs, digitized maps and year-round field measurements in a glacial flood plain, enabled us to distinguish six channel types, based on the correspondence between connectivity and physicochemical attributes. Spatial data were also used to analyze longitudinal changes in landscape elements along the course of a morphologically-intact riverine corridor, providing insight into the structural complexity that must have characterized many Alpine rivers in the pristine state. Landscape indices were employed to investigate seasonal dynamics in a glacial flood plain of the Swiss Alps which exhibits a predictable expansion/contraction cycle, with corresponding shifts in flow paths (surface and subsurface) and water sources (snowmelt, englacial, subglacial, alluvial aquifer, hillslope aquifer). Surface connectivity exhibited an unexpected biphasic relationship with total channel length, whereas riverscape diversity progressively increased along the entire range of channel length. Reconstituting the functional integrity that characterizes intact river corridors should perhaps be the major goal of river conservation initiatives. Although understanding functional processes at the landscape scale is essential in this regard, few data are available. In the Alluvial Zone National Park on the Austrian Danube, three phases of hydrological connectivity were identified (disconnection, seepage connection and surface connection) that corresponded to the predominance of three functional processes (biotic interactions, primary production and particulate transport) within the river corridor.     

Photorealistic visualisation of urban greening in a low-cost high-density housing settlement, Durban, South Africa

Apartheid housing policies of the pre-1994 South African government, and the low-cost high-density housing programmes of the post-1994 government, have given rise to numerous urban environmental problems, some of which could be addressed in a cost-effective and sustainable manner through urban greening, while simultaneously promoting biodiversity. Public participation in the planning of urban greening has been identified as being of vital importance, without which urban greening projects run a high, and expensive, risk of failure. Previous studies indicate that the greening priorities of residents in low-cost high-density housing settlements may differ considerably from those of managers and experts tasked with the protection and extension of the natural environment resource base. A system of participatory decision support is therefore required to reconcile the greening requirements of the community, and the ecological benefits of biodiversity. If language, literacy, map literacy and numeracy difficulties are to be avoided, and a sense of place or belonging is to be invoked, such a participatory decision support system should, ideally, be visually based and capable of generating realistic eye-level depictions of the urban landscape. New computer-based landscape visualisation applications, which can directly utilise geographical information systems (GIS), computer-aided design (CAD) and Digital Elevation Model (DEM) data to produce detailed photo-realistic viewsheds, were deemed better suited to the task of visualising urban greening than existing GIS-based mapping systems, CAD and traditional landscape visualisation methods. This paper examines the process of constructing a 3D computer model of the Mount Royal low-cost high-density housing settlement, situated in the eThekwini Municipality, KwaZulu-Natal, South Africa. Visualisations including terrain, natural features, indigenous vegetation, houses and roads were produced and submitted, with a questionnaire, to experts from different disciplines, Mount Royal residents and neighbours. Results from the expert survey indicate moderate support for visualisation in professional decision-making. Both experts and residents expressed strong support for the accuracy and credibility of the visualisations, as well as for their potential in a participatory decision support system.