Using remotely sensed imagery to monitor savanna rangeland deterioration through woody plant proliferation: a case study from communal and biodiversity conservation rangeland sites in Mokopane, South Africa

Healthy rangelands are of economic and biodiversity conservation importance in the savannas of northern South Africa. The proliferation of woody plant species on the rangelands, known as bush encroachment, constitutes a degradation of rangeland quality, given the non-palatability of the encroaching species. Though the causes are not fully understood, heavy grazing and fire suppression are thought to be primary causes of bush encroachment. This study utilised multitemporal (1994, 2000 and 2008) SPOT images of two rangeland sites in Mokopane, South Africa in monitoring and assessing bush encroachment. The study sites were a fenced biodiversity conservation rangeland with game species in which fire is suppressed and an open access communal rangeland grazed by livestock. Field plot-derived encroachment categories of heavy encroachment, moderate encroachment, low encroachment and non-encroached were used in hybrid classification of the images, following radiometric normalisation and geometric registration. GIS overlay analysis using the non-encroached category enabled the quantification and mapping of change in the preferable open grass rangeland typifying savannas. The biodiversity conservation area was undergoing a trend of reduction in open grass rangeland, whereas the communal rangelands were getting more opened up by livestock trampling. Rangeland management practices of fire utilisation, stocking levels and stock concentration account for the differing trends. Lightly grazed and heavily grazed wild game-utilised rangelands under a fire suppression rangeland management regime had bush encroachment rates of approximately 34% and 56%, respectively, in 6 years. Multitemporal remote sensing proved to be useful for monitoring bush encroachment as indicator of state of savanna rangelands.     

Evaluation of air pollution phytotoxicity downwind of a phosphate fertilizer factory in India

The effects of air pollution on plants downwind of a fertilizer factory at Udaipur, India, were studied using three woody perennials. Seedlings of these species including a shrub (Carissa carandas L.), a leguminous avenue tree (Cassia fistula L.) and a fruit tree (Psidium guajava L.) were grown in earthen pots at different study sites receiving varying levels of air pollution input. Changes in plant growth, morphological characteristics, photosynthetic pigment, ascorbic acid, N and S contents and in dry matter allocation were considered in relation to the status of ambient air quality. Observations with these parameters have indicated that the ambient air around the factory contained pollutants at phytotoxic levels. Plant height, basal diameter, conopy area, leaf area and chlorophyll, ascorbic acid and foliar-N concentrations decreased with increasing pollution load. However, foliar-S increased slightly at polluted sites. Air pollution load around the factory have also altered the biomass allocation. Root:shoot ratios increased in C. fistula and P. guajava at polluted sites. In contrast, for C. carandas the above ground parts, where foliage assumed predominance showed precedence over the root growth. This species responded characteristically to air pollution stress by allocating more of its photosynthate towards leaf production and shoot growth.     

Distribution pattern of plant species diversity in the mountainous Region of Ili River Valley, Xinjiang

In this paper, detrended canonical correspondence analysis was performed to analyze the relationships between diversity indices and environmental gradients, generalized additive model was employed to modal the response curves of diversity indices to the elevation, based on data from field investigation in the mountainous region of the Ili River Valley and a survey of 94 sample plots. Two hundred fifty-nine plant species were recorded in the 94 sample plots investigated, up to 235 species all appeared in the herb layer, and the species of woody plants were very limited. The communities with a complicated vertical structure presented higher values of indices. The distribution pattern of plant species diversity on the northern slope was affected by such factors as elevation, slope aspect, slope gradient, total nitrogen, total potassium, soil water content, organic matter, and that on the southern slope was mainly affected by such factors as slope gradient, elevation, available phosphorus, and soil water content. On the northern slope, Patrick index and Shannon?CWiener index of the plant communities presented a bimodality pattern along altitude; Simpson index and Pielou index showed a partially unimodal pattern. On the southern slope all the distribution pattern of species diversity indices showed two peaks, though Patrick index??s bimodality pattern was not an obvious one. These altitudinal patterns were formed by the synthetic action of a variety of environmental factors with elevation playing an important role.     

Negative effect of litter of invasive weed Lantana camara on structure and composition of vegetation in the lower Siwalik Hills,northern India

Lantana camara, an aromatic shrub, native to tropical America, was introduced into India for ornamental hedging, but later escaped and became a serious invasive weed. This study assessed the quantitative and qualitative status of plant community richness and diversity in areas invaded by L. camara in the Siwalik Hills (Himachal Pradesh, India), and explored allelopathy as a possible mechanism of interference. We measured species diversity, richness and evenness of the vegetation in areas invaded and uninvaded by L. camara. Allelopathic effects of L. camara rhizosphere soil and litter were assessed against two native plants—Achyranthes aspera (a herb) and Albizia lebbeck (a tree). Density, biomass and indices of diversity, richness and evenness were reduced by L. camara, indicating a significant alteration in composition and structure of native communities. Seedling growth of the test species was reduced in L. camara rhizosphere- and litter-amended soil. The inhibitory effect was ameliorated by the addition of activated charcoal, indicating the presence of organic inhibitors (quantified as phenolics) in the soil. Lantana invasion greatly reduces the density and diversity of the vegetation in the invaded area, and chemical interference of its litter plays an important role in invasion.     

Remote sensing of aquatic vegetation: theory and applications

Aquatic vegetation is an important component of wetland and coastal ecosystems, playing a key role in the ecological functions of these environments. Surveys of macrophyte communities are commonly hindered by logistic problems, and remote sensing represents a powerful alternative, allowing comprehensive assessment and monitoring. Also, many vegetation characteristics can be estimated from reflectance measurements, such as species composition, vegetation structure, biomass, and plant physiological parameters. However, proper use of these methods requires an understanding of the physical processes behind the interaction between electromagnetic radiation and vegetation, and remote sensing of aquatic plants have some particular difficulties that have to be properly addressed in order to obtain successful results. The present paper reviews the theoretical background and possible applications of remote sensing techniques to the study of aquatic vegetation.     

Community Based Interventions as a Strategy to Combat Desertification in the Arid and Semi-Arid Rangelands of Kajiado District, Kenya

Vegetation degradation, especially the disappearance of woody vegetation and a diminished grass cover, has aroused the concern of the Maasai community (semi-nomadic pastoralists) of Kajiado District, Kenya. The district is one of Kenya’s arid and semi-arid districts. Over recent years, they have observed their land resources deteriorate due to the desertification process caused by the land use practices of man. They have identified indicators of desertification such as increase of bare lands, which have been invaded by previously unknown grasses and weeds that are of no economic value, and also the disappearance of some useful plant species. It is due to the above concerns that a group of 30 farmers have been very keen to participate in on-farm research to strategize on ways to halt and even reverse the desertification process. The participatory research has identified useful trees that the farmers have been planting around homesteads, as woodlots on their farms to provide woodfuel, shade, and to act as windbreaks. They have also identified species for planting as live fences instead of using thorny tree branches as fencing material, which contributes further to the desertification process. Due to the termite menace on young tree seedlings, the farmers use indigenous knowledge to prepare concoctions using locally available materials, which they apply to planting holes and on seedlings. During awareness campaigns, the farmer research group highlights the need to conserve vegetation resources and also expounds on the concept of planting two trees after one is felled.     

Forest dynamics modelling under natural fire cycles: A tool to define natural mosaic diversity for forest management

In natural boreal forests, disturbances such as fire and variation in surficial deposits create a mosaic of forest stands with different species composition and age. At the landscape level, this variety of stands can be considered as the natural mosaic diversity. In this paper, we describe a model that can be used to estimate the natural diversity level of landscapes. We sampled 624 stands for tree species composition and surficial deposits in eight stand-age classes corresponding to eight fire episodes in the region of Lake Duparquet, Abitibi, Québec at the southern fringe of the Boreal Forest. For six surficial deposit types, stand composition data were used to define equations for vegetation changes with time for a chronosequence of 230 years for four forest types. Using Van Wagner's (1978) model of age class distribution of stands, the proportion of each forest type for several lengths of fire cycle were defined. Finally, for real landscapes (ecological districts) of the ecological region of the Basses-Terres d'Amos, the proportion of forest types were weighted by the proportion of each surficial deposit type using ecological map information. Examples of the possible uses of the model for management purposes, such as biodiversity conservation and comparisons of different landscapes in terms of diversity and sensitivity to fire regime changes, are discussed.     

Evaluating the ecological integrity of Atlantic forest remnants by using rapid ecological assessment

The need for quick identification of priority areas for biodiversity protection makes rapid assessment methods important management tools for defining conservation strategies. An increasingly used rapid assessment method is rapid ecological assessment (REA), a fast and flexible survey directed toward selected indicator species and vegetation forms. The purpose of this study was to propose and test REA based on plant community features of the semideciduous Atlantic forest (SAF). Correlation tests were performed between data collected by REA and plant species diversity, richness, and abundance collected by conventional woody plant inventory methods. The study was conducted in 21 SAF patches in Northern Paraná State, Brazil. The phytosociological inventory was conducted along a single transect and required 2 days to complete (excluding time spent for herbarium identification), whereas REA was conducted along three to four transects per working day. REA results correlated positively with woody plant diversity, proving REA to be an efficient method for defining the conservation status of SAF fragments, but accuracy of evaluations of threats to biological integrity are relatively low. Both the selection of appropriate variables and the skill level of field staff are critical and can strongly influence REA results.     

Can tree species diversity be assessed with Landsat data in a temperate forest?

The diversity of forest trees as an indicator of ecosystem health can be assessed using the spectral characteristics of plant communities through remote sensing data. The objectives of this study were to investigate alpha and beta tree diversity using Landsat data for six dates in the Gönen dam watershed of Turkey. We used richness and the Shannon and Simpson diversity indices to calculate tree alpha diversity. We also represented the relationship between beta diversity and remotely sensed data using species composition similarity and spectral distance similarity of sampling plots via quantile regression. A total of 99 sampling units, each 20 m × 20 m, were selected using geographically stratified random sampling method. Within each plot, the tree species were identified, and all of the trees with a diameter at breast height (dbh) larger than 7 cm were measured. Presence/absence and abundance data (tree species number and tree species basal area) of tree species were used to determine the relationship between richness and the Shannon and Simpson diversity indices, which were computed with ground field data, and spectral variables derived (2 × 2 pixels and 3 × 3 pixels) from Landsat 8 OLI data. The Shannon-Weiner index had the highest correlation. For all six dates, NDVI (normalized difference vegetation index) was the spectral variable most strongly correlated with the Shannon index and the tree diversity variables. The Ratio of green to red (VI) was the spectral variable least correlated with the tree diversity variables and the Shannon basal area. In both beta diversity curves, the slope of the OLS regression was low, while in the upper quantile, it was approximately twice the lower quantiles. The Jaccard index is closed to one with little difference in both two beta diversity approaches. This result is due to increasing the similarity between the sampling plots when they are located close to each other. The intercept differences between two investigated beta diversity were strongly related to the development stage of a number of sampling plots in the tree species basal area method. To obtain beta diversity, the tree basal area method indicates better result than the tree species number method at representing similarity of regions which are located close together. In conclusion, NDVI is helpful for estimating the alpha diversity of trees over large areas when the vegetation is at the maximum growing season. Beta diversity could be obtained with the spectral heterogeneity of Landsat data. Future tree diversity studies using remote sensing data should select data sets when vegetation is at the maximum growing season. Also, forest tree diversity investigations can be identified by using higher-resolution remote sensing data such as ESA Sentinel 2 data which is freely available since June 2015.     

Effect of Fly-Ash on Metal Composition and Physiological Responses in Leucaena Leucocephala (Lamk.) de. Wit.

Plants of L. leucocephala were grown in 100%soil (as control), 100% fly-ash and fly-ash amendedwith 50% press mud for 80 days, and analysed withrespect to plant growth, elemental composition andphysiological changes in different parts of the plant.The results revealed that amending fly-ash with pressmud enhanced plant growth as well as otherphysiological responses such as chlorophyll, protein,in vivo nitrate reductase activity compared to100% fly-ash treated plants. The elements Fe, Zn, Cuand Mn accumulated in larger quantities in plantsgrown in 100% fly-ash, and followed the order ofaccumulation Fe > Zn > Cu > Mn. The results of thisstudy indicate that ash amending with press mud mayprovide more favourable conditions for the growth ofthis tree species.     

Satellite monitoring of desert plant community response to moisture availability

Our study demonstrates the utility of coarse spatial-resolution satellite spectra for analysis of vegetation phenophases and response to moisture availability in an arid ecosystem. We show the feasibility of deriving information on vegetation parameters such as stress and growth patterns in arid regions through the use of satellite-derived vegetation indices, despite the usual problems associated with a high ratio of soil to vegetation cover. Vegetation in our study area consists of Chihuahuan Desert grassland and scrub, including extensive zones of mixed desert scrub and grassland. Historic vegetation change has been well documented and is exemplified by decreasing grass cover and increasing shrub cover, a general trend of desertification. Our analysis suggests that satellite-based inputs can be used to improve our understanding of the spatial dynamics of climatic impacts on natural vegetation and to help us distinguish these processes from human-caused desertification.     

Plutonium uptake and behavior in vegetation of the desert southwest: a preliminary assessment

Eight species of desert vegetation and associated soils were collected from the Nevada National Security Site (N2S2) and analyzed for 238Pu and 239 + 240Pu concentrations. Amongst the plant species sampled were: atmospheric elemental accumulators (moss and lichen), the very slow growing, long-lived creosote bush and the rapidly growing, short-lived cheatgrass brome. The diversity of growth strategies provided insight into the geochemical behavior and bio-availability of Pu at the N2S2. The highest concentrations of Pu were measured in the onion moss (24.27 Bq kg-1 238Pu and 52.78 Bq kg-1 239 + 240Pu) followed by the rimmed navel lichen (8.18 Bq kg-1 and 18.4 Bq kg-1 respectively), pointing to the importance of eolian transport of Pu. Brome and desert globemallow accumulated between 3 and 9 times higher concentrations of Pu than creosote and sage brush species. These results support the importance of species specific elemental accumulation strategies rather than exposure duration as the dominant variable influencing Pu concentrations in these plants. Total vegetation elemental concentrations of Ce, Fe, Al, Sm and others were also analyzed. Strong correlations were observed between Fe and Pu. This supports the conclusion that Pu was accumulated as a consequence of the active accumulation of Fe and other plant required nutrients. Cerium and Pu are considered to be chemical analogs. Strong correlations observed in plants support the conclusion that these elements displayed similar geochemical behavior in the environment as it related to the biochemical uptake process of vegetation. Soils were also sampled in association with vegetation samples. This allowed for the calculation of a concentration ratio (CR). The CR values for Pu in plants were highly influenced by the heterogeneity of Pu distribution among sites. Results from the naturally occurring elements of concern were more evenly distributed between sample sites. This allowed for the development of a pattern of plant species that accumulated Ce, Sm, Fe and Al. The highest accumulators of these elements were onion moss, lichen flowed by brome. The lowest accumulators were creosote bush and fourwing saltbush. This ranked order corresponds to plant accumulations of Pu.     

The effects of grassland degradation on plant diversity,primary productivity,and soil fertility in the alpine region of Asia’s headwaters

A 3-year survey was conducted to explore the relationships among plant composition, productivity, and soil fertility characterizing four different degradation stages of an alpine meadow in the source region of the Yangtze and Yellow Rivers, China. Results showed that plant species diversity, productivity, and soil fertility of the top 30-cm soil layer significantly declined with degradation stages of alpine meadow over the study period. The productivity of forbs significantly increased with degradation stages, and the soil potassium stock was not affected by grassland degradation. The vegetation composition gradually shifted from perennial graminoids (grasses and sedges) to annual forbs along the degradation gradient. The abrupt change of response in plant diversity, plant productivity, and soil nutrients was demonstrated after heavy grassland degradation. Moreover, degradation can indicate plant species diversity and productivity through changing soil fertility. However, the clear relationships are difficult to establish. In conclusion, degradation influenced ecosystem function and services, such as plant species diversity, productivity, and soil carbon and nitrogen stocks. Additionally, both plant species diversity and soil nutrients were important predictors in different degradation stages of alpine meadows. To this end, heavy degradation grade was shown to cause shift of plant community in alpine meadow, which provided an important basis for sustaining ecosystem function, manipulating the vegetation composition of the area and restoring the degraded alpine grassland.     

Mapping the Spatial Variability of Plant Diversity in a Tropical Forest: Comparison of Spatial Interpolation Methods

Knowledge of the spatial distribution of plant species is essential to conservation and forest managers in order to identify high priority areas such as vulnerable species and habitats, and designate areas for reserves, refuges and other protected areas. A reliable map of the diversity of plant species over the landscape is an invaluable tool for such purposes. In this study, the number of species, the exponent Shannon and the reciprocal Simpson indices, calculated from 141 quadrat sites sampled in a tropical forest were used to compare the performance of several spatial interpolation techniques used to prepare a map of plant diversity, starting from sample (point) data over the landscape. Means of mapped classes, inverse distance functions, kriging and co-kriging, both, applied over the entire studied landscape and also applied within vegetation classes, were the procedures compared. Significant differences in plant diversity indices between classes demonstrated the usefulness of boundaries between vegetation types, mapped through satellite image classification, in stratifying the variability of plant diversity over the landscape. These mapped classes, improved the accuracy of the interpolation methods when they were used as prior information for stratification of the area. Spatial interpolation by co-kriging performed among the poorest interpolators due to the poor correlation between the plant diversity variables and vegetation indices computed by remote sensing and used as covariables. This indicated that the latter are not suitable covariates of plant diversity indices. Finally, a within-class kriging interpolator yielded the most accurate estimates of plant diversity values. This interpolator not only provided the most accurate estimates by accounting for the indices' intra-class variability, but also provided additional useful interpretations of the structure of spatial variability of diversity values through the interpretation of their semi-variograms. This additional role was found very useful in aiding decisions in conservation planning.     

Modelling and assessment of South African elephant Loxodonta africana population persistence

The use of a quantitative population growth model to investigate the persistence of South African elephant populations is explored. The model provides quantitative assessments of population persistence and confidence intervals for estimated parameters based purely on population size estimates. The analysis supports the view that most of the larger populations in the region are secure. This view is further supported by a lack of density dependent effects in most of the recovering populations and the high population rates of increase observed. This predominantly positive prognosis is in contrast with that emerging from most of the rest of the African continent where the populations are under greater threat because of habitat restriction and direct human conflict. This preliminary assessment of elephant population persistence suggests that “viable” populations may lie between 400 and 6000 individuals. Although not inconsistent with information-greedy genetic and demographic models, the relationship between population growth versus genetic and demographic models should be further investigated. The implementation of a metapopulation management strategy towards these smaller populations is advocated. In addition, as all of the populations included in this analysis have been afforded some degree of protection since the 1920s, continued protection would be a prerequisite for their continued survival.     

South Africa's arid and semiarid rangelands: Why are they changing and can they be restored?

Since the mid-19th century settled livestock ranching has been the major form of land use in South Africa, occupying 68% of the land surface. Decreases in livestock densities and ranch numbers during the past century imply that carrying capacities for domestic herbivores are falling. Differences in carbon isotope signals with soil depth and abrupt shifts in dominant plant species across ranch boundaries reveal that southern African rangelands are changing. Case studies suggest ways to control altered grassland composition, bush encroachment in arid savanna, and dominance by toxic and halophytic shrubs in arid shrublands. But climatic and biological factors constrain rates of passive recovery, and guidelines for active restoration are poor and techniques costly. Moreover, conservation of remaining good rangeland is seldom enforced, and economic considerations usually outweight the land user's desire to sustain diversity and productivity.     

Integrating in-situ, Landsat, and MODIS data for mapping in Southern African savannas: experiences of LCCS-based land-cover mapping in the Kalahari in Namibia

Integrated ecosystem assessment initiatives are important steps towards a global biodiversity observing system. Reliable earth observation data are key information for tracking biodiversity change on various scales. Regarding the establishment of standardized environmental observation systems, a key question is: What can be observed on each scale and how can land cover information be transferred? In this study, a land cover map from a dry semi-arid savanna ecosystem in Namibia was obtained based on the UN LCCS, in-situ data, and MODIS and Landsat satellite imagery. In situ botanical relevé samples were used as baseline data for the definition of a standardized LCCS legend. A standard LCCS code for savanna vegetation types is introduced. An object-oriented segmentation of Landsat imagery was used as intermediate stage for downscaling in-situ training data on a coarse MODIS resolution. MODIS time series metrics of the growing season 2004/2005 were used to classify Kalahari vegetation types using a tree-based ensemble classifier (Random Forest). The prevailing Kalahari vegetation types based on LCCS was open broadleaved deciduous shrubland with an herbaceous layer which differs from the class assignments of the global and regional land-cover maps. The separability analysis based on Bhattacharya distance measurements applied on two LCCS levels indicated a relationship of spectral mapping dependencies of annual MODIS time series features due to the thematic detail of the classification scheme. The analysis of LCCS classifiers showed an increased significance of life-form composition and soil conditions to the mapping accuracy. An overall accuracy of 92.48% was achieved. Woody plant associations proved to be most stable due to small omission and commission errors. The case study comprised a first suitability assessment of the LCCS classifier approach for a southern African savanna ecosystem.     

Monitoring of environmental parameters for CO2 sequestration: a case study of Nagpur City, India

The use of native plants was examined in three rural communities in the semi-arid of the state of Pernambuco, in northeastern Brazil. The techniques employed in the present study combined a number of different techniques of data-gathering, including semi-structured interviews, guided tour, key-informants, and participating observation, and sampling of the vegetation to evaluate the biodiversity of useful plants. A total of 61 woody species were cataloged, mostly used for construction purposes or fuel. Among the species that stood out for their local importance and multiplicity of uses were: Myracrodruon urundeuva (Engl.) Fr. All., Schinopsis brasiliensis Engl., and Anadenanthera colubrina (Vell.) Brenan. The first two species are included in Brazilian lists of threatened species. Arguments are presented for strategies of management and conservation of plant resources in the semi-arid region that seek alternatives to the use of timber species and the development of alternative non-timber resources.     

The effect of management systems and ecosystem types on bark regeneration in Himatanthus drasticus (Apocynaceae): recommendations for sustainable harvesting

Bark and exudates are widely commercialized non-timber forest products. However, the ecological impacts of the harvesting of these products have seldom been studied. The aim of this study is to investigate the relationship of tree resilience to harvesting intensity in Himatanthus drasticus, a tree that is highly exploited in the Brazilian savanna (Cerrado) for its medicinal latex. Although the traded product is the latex, the traditional harvesting systems involve the removal of the bark of the trees to allow exploitation. A 3-year experiment was conducted in two different Cerrado ecosystems (open savanna and savanna woodland). Trees were debarked at four debarking intensities to simulate the effects of traditional management systems. Measurements of bark growth were taken every 6 months, and quantitative and qualitative indexes of bark regeneration were obtained. The mortality of the debarked trees was low and could not be related to the intensity of harvesting. No signs of attack by fungi or insects were recorded. Compared with other species exploited for bark, H. drasticus is very resilient to harvesting; however, bark regeneration is relatively slow. In both analyzed ecosystems, the regeneration indexes showed higher values in the controls than in the treatments, indicating that 3 years is not sufficient for total recovery of the rhytidome. Bark regeneration occurred primarily by sheet growth and was more rapid in open savanna than in savanna woodland. No differences in the rate of bark recovery were found among management treatments. Based on the results, sustainable harvesting guidelines are suggested for the species.     

A model for species diversity monitoring at community level and its applications

A simple, handly and powerful tool, called the DIMO model based on the Shannon-Wiener index, has been developed for analysis and evaluation of species diversity at plant community (alpha) level. Three axes, i.e. species richness, species evenness and the Shannon-Wiener index, were plotted in a two-dimensional space. Any change in these parameters and their relationship can be easily analysed and demonstrated by the model. A modified Shannon-Wiener index,Q, based on the DIMO model, was constructed to integrate species richness and evenness. The model and theQ index were tested with the real-life data collected from vegetation monitoring by the Swedish National Environmental Monitoring Program (PMK) during a 12-year period. Because of its dynamic features, the DIMO model is especially suitable for biodiversity monitoring at community level and can be applied to other levels as well if one replaces species taxa by other categories.