Elephant (Loxodonta africana) Disturbance to Riparian Woodland: Effects on Tree-Species Richness,Diversity and Functional Redundancy

The substantial increase in elephant populations across many areas in southern Africa over past decades is prompting concerns about the effects on biodiversity. We investigated the outcomes of elephant disturbance on tree-species presence, density, and richness, and on alpha and beta diversity within riparian woodland in Chobe National Park, Botswana. We enumerated all tree species occurring in 32 plots (0.06 ha) along the Chobe riverfront. Plots were stratified by soil type (nutrient-rich alluvium vs. nutrient-poor Kalahari sand covering alluvium) and elephant impact (high vs. low impact on both soil types). We tested four predictions: elephants reduce tree density, richness, and alpha diversity; beta diversity is greater in vegetation subjected to high elephant impact; elephant impact on tree-species composition is greater on nutrient-poor than on nutrient-rich soil; and the loss or decline of abundant tree species on heavily disturbed sites is offset by an increase in abundance of functionally similar species, ones that are minor on lightly disturbed sites. Elephant browsing substantially affected tree-species composition, reducing density, species richness, evenness, and alpha diversity but had no effect on beta diversity. The dominant species on relatively undisturbed areas were partly replaced by functionally similar species on heavily disturbed sites. Soil type influenced species composition on lightly disturbed sites but was less important at higher elephant densities. Our findings are important for areas with extreme dry-season densities of elephants but should not be extrapolated to infer purported effects of elephants on tree diversity at lower densities.     

Changes in tree populations of Tsavo East National Park, Kenya*

To assess distribution, density and population trends under the impact of elephants and other browsing herbivores, trees of four common species were counted in belt transects along existing roads in Tsavo East National Park in 1970 and 1974. In three of the four species, mature and recruitment-age trees declined substantially during this period. The reduction can be attributed almost entirely to utilization by elephants. The fourth species showed a slight increase in mature and recruitment-age trees; significantly, it is not eaten by elephants. A high regeneration potential (trees <1 m high) still exists, even in the worst-affected species. However, most of the young in dividuals do not reach recruitment age due to the heavy browsing to which they are subjected. Whether the recent reduction of the elephant population has been sufficient to reverse this trend, remains to be seen; much depends on rainfall, too, which was below average during the period considered.     

Threats to the tropical island dragonfly fauna (Odonata) of Mayotte, Comoro archipelago

The dragonfly fauna of the 374 km² island of Mayotte in the western Indian Ocean comprises some widespread African species and some Comoro endemics, and is a biodiversity hotspot. This dragonfly assemblage is under threat from increasing human impact as it creeps up the water courses from the periphery of the island towards the centre. Among these impacts are indigenous tree removal and replacement growth by alien vegetation. An even greater impact and threat is detergent input into streams. The intensity of this impact is so great that the streams and rocks become white. To date, although often the wings and bodies of odonates become stained white with detergent, the dragonfly assemblage appears remarkably tolerant of this impact. However, there is differential impact, with loss of island endemic species in the most impacted areas. In contrast, the geographically widespread and eurytopic species continue to thrive in these impacted areas, at least in the short term. It is urgent to change people's water-usage behaviour, both for their benefit and for the endemic dragonfly assemblage.     

Comparison of regeneration following burning,clearing or mineral sand mining at Tomago,NSW: II. Succession of ant assemblages in a coastal forest

Abstract The dry sclerophyll forest community of the Tomago Sandbeds, near Newcastle in New South Wales, has been subject to regular disturbances due to fire, clearing and strip mining for over 18 years. In this study we use chronosequence analysis to examine whether the structure of the ant community varies with the type of disturbance and the time since disturbance. We treat the recovery trajectory after fire as a control trajectory because fire is an endogenous disturbance. The main analyses were based on an ant fauna comprising 72 species sampled from 44 sites surveyed in December 1992. Comparison with samples taken in April and December 1991, and for cumulative records for all sites over this 20 month period, all show quantitatively similar responses. Results suggest that while fire has a minor effect on the composition of the ant community over time, the impact of clearing and mining is much more severe. Ant species richness at cleared and mined sites recovers rapidly, overshoots controls in mid-succession and returns to control levels by 18 years after disturbance. The cumulative number of species recorded over all sites (from the total recorded fauna of 82 species) for each different disturbance type were: burned, 61; cleared, 55; and mined 56. Species composition at cleared or mined sites, after 18 years, approaches but does not match controls. The recovery trend for mined sites lags slightly behind that for cleared sites, which have reached 49% similarity with the oldest burned sites, while mined sites have not exceeded 39% similarity of species composition. The main patterns in the ant community appear to be related to habitat variables. These results provide further evidence that the ant community may be used as a reliable bio-indicator for evaluating the extent of habitat damage and recovery after disturbance in these Australian forests.     

The impacts of habitat disturbance on adult and larval dragonflies (Odonata) in rainforest streams in Sabah,Malaysian Borneo

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Local environment rather than past climate determines community composition of mountain stream macroinvertebrates across Europe

Community assembly is determined by a combination of historical events and contemporary processes that are difficult to disentangle, but eco‐evolutionary mechanisms may be uncovered by the joint analysis of species and genetic diversity across multiple sites. Mountain streams across Europe harbour highly diverse macroinvertebrate communities whose composition and turnover (replacement of taxa) among sites and regions remain poorly known. We studied whole‐community biodiversity within and among six mountain regions along a latitudinal transect from Morocco to Scandinavia at three levels of taxonomic hierarchy: genus, species and haplotypes. Using DNA barcoding of four insect families (>3100 individuals, 118 species) across 62 streams, we found that measures of local and regional diversity and intraregional turnover generally declined slightly towards northern latitudes. However, at all hierarchical levels we found complete (haplotype) or high (species, genus) turnover among regions (and even among sites within regions), which counters the expectations of Pleistocene postglacial northward expansion from southern refugia. Species distributions were mostly correlated with environmental conditions, suggesting a strong role of lineage‐ or species‐specific traits in determining local and latitudinal community composition, lineage diversification and phylogenetic community structure (e.g., loss of Coleoptera, but not Ephemeroptera, at northern sites). High intraspecific genetic structure within regions, even in northernmost sites, reflects species‐specific dispersal and demographic histories and indicates postglacial migration from geographically scattered refugia, rather than from only southern areas. Overall, patterns were not strongly concordant across hierarchical levels, but consistent with the overriding influence of environmental factors determining community composition at the species and genus levels.     

Resilience of a high‐conservation‐value,semi‐arid grassland on fertile clay soils to burning,mowing and ploughing

In grassland reserves, managed disturbance is often necessary to maintain plant species diversity. We carried out experiments to determine the impact of fire, kangaroo grazing, mowing and disc ploughing on grassland species richness and composition in a nature reserve in semi‐arid eastern Australia. Vegetation response was influenced by winter–spring drought after establishment of the experiments, but moderate rainfall followed in late summer–autumn. Species composition varied greatly between sampling times, and the variability due to rainfall differences between seasons and years was greater than the effects of fire, kangaroo grazing, mowing or disc ploughing. In the fire experiment, species richness and composition recovered more rapidly after spring than autumn burning. Species richness and composition were similar to control sites within 12 months of burning and mowing, suggesting that removal of the dominant grass canopy is unnecessary to enhance plant diversity. Two fires (separated by 3 years) and post‐fire kangaroo grazing had only minor influence on species richness and composition. Even disc ploughing caused only a small reduction in native richness. The minor impact of ploughing was explained by the small areas that were ploughed, the once‐off nature of the treatment, and the high degree of natural movement and cracking in these shrink‐swell soils. Recovery of the composition and richness of these grasslands was rapid because of the high proportion of perennial species that resprout vegetatively after fire and mowing. There appears to be little conservation benefit from fire, mowing or ploughing ungrazed areas, as we could identify no native plant species dependent on frequent disturbance for persistence in this grassland community. However, the ability of the Astrebla‐ and Dichanthium‐dominated grasslands to recover quickly after disturbance, given favourable seasonal conditions, suggests that they are well adapted to natural disturbances (e.g. droughts, fire, flooding and native grazing).     

Development of the Concept of ‘Core Resident Species’ for Quality Assurance of an Insect Reserve

Awareness in the eyes of the public is important for involving the wider community in conservation. A dragonfly awareness trail was developed and implemented in the year 2000 at a national botanical garden in South Africa. Such a trail is not likely to always have the same number of dragonfly species either throughout the year or from one year to the next. The aim was to assess dragonfly assemblage changes that occurred along the trail over 3 years, so as to fine-tune expectations that the public may have as regards species to be seen at any particular time. A cumulative species variance for species and speciesenvironmental relations, strongly indicated that certain measured site variables were responsible for the main variation in dragonfly species patterns over time. Habitat requirements of an odonate species may be defined primarily in terms of marginal grasses, floating and submerged vegetation, marginal herbs, sedges and reeds, and pH. Additional variables were percentage shade, exposed rock, marginal forest and water flow characteristics. Both dragonfly species richness and abundance changed over the 3 years. One of the reasons for this was a single, major disturbance, in the form of dredging the reservoir site to reverse ecological succession in 2002. Despite an impact such as this, and after accounting for vagrancy, there were in all 24 ‘core resident species’ still to be seen along the trail from January to May. Another 11 species, including two migrants and one species lost temporarily to dredging disturbance, can be considered only as ‘possibilities’ on any one visit. Assurance that the 24 core species can be seen in the summer months (although only three in winter) is essential for maintaining the bona fide of such a trail, and hence conservation awareness, in the eyes of the public.     

Causes of species diversity differences: a comparative analysis of Markov models

While many dynamic processes have been proposed to produce diversity differences among communities, most empirical investigations focus on static system attributes. An ideal analysis would consider multiple dynamic processes and their impact on many community members, but such analyses can be logistically daunting. I compared Markov chain models of ecological communities to explore general processes leading to diversity differences of sessile species between coral reefs and rocky intertidal mussel beds. As predicted by diversity theory, high diversity coral reefs had lower species replacement probabilities and higher disturbance rates than did lower diversity mussel beds. Intransitivities in species replacements, recruitment limitation and responses to perturbing species from equilibrium (Jacobian elements) did not differ significantly between systems. Tradeoffs between the displacement risk or displacement ability of a species and either disturbance risk or colonising ability were not apparent. Manipulating the coral reef model to eliminate disturbance or intransitivities caused declines in species diversity, whereas removing recruitment limitation or increasing the probability of interspecific replacement did not. Higher overall disturbance levels can explain part of the diversity difference between systems, but much remained unexplained, indicating that details of the pattern and strengths of species interactions were probably extremely important.     

Differences in woody vegetation are unrelated to use by African elephants (Loxodonta africana) in Mkhuze Game Reserve, South Africa

The reintroduction of African elephants into fenced game reserves throughout South Africa has presented managers with several challenges. Although elephants are a natural part of southern African ecosystems, their confinement to fenced protected areas in South Africa has exacerbated their potential to impact their habitats negatively. However, many studies investigating the impact of elephants have failed to control for the effects of other browsers on the vegetative community. In this study, we used location data on an elephant herd to delineate high-use and low-use areas. This paired design allowed us to minimize confounding factors that could explain differences in the structure, diversity and utilization of woody species. We found little evidence to suggest elephant-mediated change in, or selection for, the structure or diversity of woody species; however, our results suggest that elephants may be altering the composition of species by preferentially using areas with higher canopy diversity and by enhancing sapling recruitment. Although stripping of bark was higher in high-use areas, there was no evidence of differential mortality of tree species. Therefore, in our study area, and over the current time scale, elephants are having a negligible impact on the vegetative community.     

Coral species richness: ecological versus biogeographical influences

Species richness in communities varies with habitat area, productivity, disturbance level, intensity of species interactions, and regional/historical effects. All of these factors influence coral richness but their effects vary with spatial scale, position on the reef, and regional location. Species richness of corals along depth gradients shows a unimodal, hump-shaped curve that peaks at intermediate depths. Moreover, the peak of the curve is higher in regions with larger species pools. This “regional enrichment” of the local community appears in line transect samples as small as 10 m in length. The pattern suggests that ecological factors operating over scales of tens of meters and regional/historical factors operating over thousands of kilometers can both affect local richness. Regional factors probably include differences in speciation relative to extinction rates among regions and proximity of local sites to richness hotspots. Plausible factors operating at the local scale are species interactions, disturbance, and productivity which combine in different ways to produce the unimodal pattern. Shallow areas support few species because extinction rates are high due to frequent disturbance or because of environmental extremes. In addition, high productivity encourages rapid growth and thus the potential for intense interspecific competition. In areas where branching acroporids are abundant, exclusion by these dominant competitors is possible. Deep areas may be depauperate because few species can tolerate the low light levels found there. Areas of intermediate depth have the richest communities because they are open for colonization by many species and because extinction rates are low. Several theories may explain this “openness” and species persistence: 1. Occasional disturbance coupled with low growth rates results in glacially slow exclusion by the dominant competitor. 2. Aggregation of corals creates spatial variation in the intensity of competition and thus refuges from competition within a spatial landscape. Inferior competitors persist because they are superior at dispersal and refuge colonization. 3. Specialist predators focus on high-density juvenile populations near the parent, creating ecological space for colonization by non-prey. 4. Coral competitive abilities are roughly equal and recruitment into the community is a probabilistic event. The community thus exhibits random drift and exclusion is an extremely lengthy process. Based upon empirical evidence, these theories are listed in order of plausibility, but still need to be rigorously tested. Accepted: 9 September 1999     

Woody riparian plant distributions in western Oregon,USA: comparing landscape and local scale factors

We studied riparian forests along mountain streams in four large watersheds of western Oregon and far northern California, USA, to better understand the multiscale controls on woody riparian vegetation in a geographically complex region. In each of the four-study watersheds, we sampled woody riparian vegetation in161-ha sampling reaches that straddled the stream channel. Within each hectare, we sampled riparian vegetation and local environmental factors in 40 m² sampling plots arrayed along topographic transects. We also surveyed natural disturbance gaps in 6 ha in each watershed to explore the effects of fine scale disturbance on species distributions. We compared species composition across our study watersheds and used Nonmetric Multidimensional Scaling (NMS) and chi-squared analyses to compare the relative importance of landscape scale climate variables and local topographic and disturbance variables in explaining species distributions at sampling plot and hectare scales. We noted substantial turnover in the riparian flora across the region, with greatest numbers of unique species in watersheds at the ends of the regional gradient. In NMS ordinations at both scales, variation in woody riparian species composition showed strongest correlations with climatic variables and Rubus spectabilis cover, but the latter was only an important factor in the two northern watersheds. At the smaller scale, topographic variables were also important. Chi-squared analyses confirmed that more species showed landscape scale habitat preferences (watershed associations) than associations with topographic position (94.7% vs. 42.7% of species tested) or gap versus forest setting (94.7% vs. 24.6% of species tested). The woody riparian flora of western Oregon shows important biogeographic variation; species distributions showed strong associations with climatic variables, which were the primary correlates of compositional change between riparian sites at both scales analyzed. Additional local variation in composition was explained by measures of topography and disturbance.     

Genetic Similarity of Island Populations of Tent Caterpillars during Successive Outbreaks

Cyclic or fluctuating populations experience regular periods of low population density. Genetic bottlenecks during these periods could give rise to temporal or spatial genetic differentiation of populations. High levels of movement among increasing populations, however, could ameliorate any differences and could also synchronize the dynamics of geographically separated populations. We use microsatellite markers to investigate the genetic differentiation of four island and one mainland population of western tent caterpillars, Malacosoma californicum pluviale, in two periods of peak or pre-peak density separated by 8 years. Populations showed high levels of genetic variation and little genetic differentiation either temporally between peaks or spatially among sites. Mitochondrial haplotypes were also shared between one island population and one mainland population in the two years studied. An isolation-by-distance analysis showed the F_ST values of the two geographically closest populations to have the highest level of differentiation in both years. We conclude that high levels of dispersal among populations maintain both synchrony of population dynamics and override potential genetic differentiation that might occur during population troughs. As far we are aware, this is the first time that genetic similarity between temporally separated population outbreaks in insects has been investigated. A review of genetic data for both vertebrate and invertebrate species of cyclic animals shows that a lack of spatial genetic differentiation is typical, and may result from high levels of dispersal associated with fluctuating dynamics.     

Environmental and spatial variables influence the composition of frog assemblages in sub-tropical eastern Australia

In community ecology, contrasting theories suggest that the distribution and abundance of species, and thus the composition of assemblages, are influenced by i) environmental gradients, or ii) contagious biotic processes such as predation, competition, dispersal and disease. In the former case, sites with similar environments would tend to support similar assemblages, while in the latter, geographically proximate sites would tend to support more similar assemblages than widely separated sites. I investigated the relative influence of environmental variables and spatial position on the composition of frog assemblages at forest streams in sub-tropical eastern Australia using redundancy analysis (RDA) and partial RDA. Data on the maximum abundance of the frog species at 65 survey sites were transformed such that RDA would yield the Hellinger distance between sites. The following analysis identified 11 environmental variables that explained 45% of the variation in the abundance of species at the survey sites (the species matrix), as a proportion of total variance. The geographic co-ordinates of the survey sites accounted for 12%, while the environmental and spatial variables combined accounted for 47% of the variation in the species matrix. Partial redundancy analysis indicated that of the explained variation, 74% was purely environmental, 5% was purely spatial and 21% was spatial environmental variation. This study is the first to quantify the relative influence of environmental and spatial variables on the composition of amphibian assemblages. It provides support for both the environmental control model and the biotic control model of species' distributions and assemblage composition, although environmental variables appear to have the greater effect at this scale of analysis.     

How does a re-colonizing population of Asian elephants affect the forest habitat?

The Asian elephant Elephas maximus is currently re-colonizing the Bardia National Park in lowland Nepal. We studied their impact on woody vegetation in the nutrient-rich floodplain and in the relatively nutrient-poor sal forest. The types and extent of tree impact were recorded along fixed-width transects (335 km). Species composition, density and size classes ≥8 cm diameter breast height (dbh) were recorded in 15-m radius random plots ( n =95). Impact was higher in the floodplain complex than in the sal-dominated forest. Our hypothesis that elephants were more selective on species in the nutrient-poor sal forest was only partly supported; the niche breadth of impacted trees was slightly higher in the floodplain complex. Pushed-over trees accounted for the highest proportion of impact (55%), followed by killed trees (39%). Of the pushed trees, 10% were not used for food. Among food trees, elephants selectively impacted size class 12–16 cm dbh, whereas non-food trees were impacted independently of size. A large proportion of the freshly browsed trees had been felled previously, indicating that most felled trees survived, enabling elephants to feed on them again. This may reflect an evolutionary adaptation among long-lived species with high site fidelity. Owing to preferential use but low abundance, two species in sal forest, Grewia spp. and Desmodium oojeinense , were found to be particularly vulnerable to local extinction due to elephants. Although the elephants had impacted a large number of species (62, 73% of all), 56.4% of the impacted trees consisted of Mallotus phillippinensis . A recently observed increase in the density of M. phillippinensis and the concurrent reduction of the hardly utilized Shorea robusta indicates that the rapidly growing elephant population may modify the composition of the forest by increasing its preferred food species.     

Variation in structure and diversity in Mediterranean grasslands related to trophic status and grazing intensity

Abstract. The spatial organization of Mediterranean grassland in Spain is described, based on samples from 71 sites covering the existing variation in slope exposition and inclination.The whole set can be regarded as representing a trophic gradient, along which gradual variation in soil, species composition, biomass, and coverage were quantified. Corresponding to other studies from varying habitats, maximal species richness, diversity, and heterogeneity were observed on moderately infertile sites. Maximum species richness, over 60 species, occurred on sites with biomass values from 150–350 g / m². Species richness values are much higher and biomass values are much lower than those found in temperate grasslands. The decrease in diversity towards the mosteutrophic communities is stronger than expected, but can be easily explained by the high grazing pressure here. The variation in diversity observed runs parallel with that in heterogeneity. Zones with a high species richness also have a high heterogeneity, meaning a low amount of dominance. Grazing is understood as abiotic form of disturbance. Differences in grazing pressure may modify the relation between richness and fertility. While the greatest grazing pressure coincides with the most eutrophic communities, decreasing progressively towards the oligotrophic ones, the trend predicted by the resource availability theory is maintained; species diversity will be maximal at intermediate levels of disturbance. Absence of grazing in the eutrophic communities would lead to an investment in the soil of the unconsumed organic matter.     

Impact of Human Activity on Regional Forest Composition and Dynamics in Central New England

Historical and ecological data from north-central Massachusetts suggest that widespread and intensive human disturbance after European settlement led to a shift in forest composition and obscured regional patterns of species abundance. A paleoecological approach was required to place recent forest dynamics in a long-term context. Pollen and charcoal data from 11 small lakes in north-central Massachusetts were used to reconstruct local vegetation dynamics and fire histories across the region over the past 1000 years. The sites are located across an environmental gradient. Paleoecological data indicate that prior to European settlement, there was regional variation in forest composition corresponding to differences in climate, substrate, and fire regime. Oak, chestnut, and hickory were abundant at low elevations, whereas hemlock, beech, sugar maple, and yellow birch were common at high elevations. Fire appears to have been more frequent and/or intense at lower elevations, maintaining high abundances of oak, and archaeological data suggest Native American populations were greater in these areas. A change in forest composition at higher elevations, around 550 years before present, may be related to the Little Ice Age (a period of variable climate), fire, and/or activity by Native Americans, and led to regional convergence in forest composition. After European settlement, forest composition changed markedly in response to human disturbance and there was a sharp increase in rates of vegetation change. Regional patterns were obscured further, leading to homogenization of broad-scale forest composition. There is no indication from the pollen data that forests are returning to pre-European settlement forest composition, and rates of vegetation change remain high, reflecting continuing disturbance on the landscape, despite regional reforestation. Received 14 May 1997; accepted 5 August 1997.     

Shifts in dominance of native and invasive plants in experimental patches of vegetation

While it is widely accepted that disturbance often promotes the process of plant invasion, few data are available on specific relationships between different types of disturbance and success of plant invaders. Nor is much known about variation in invader behaviour in response to changing composition of the dominant native species in the recipient habitats. In the middle Main valley near Würzburg (Germany), two invasive Brassicaceae forbs, Bunias orientalis and Rorippa austriaca, are frequently associated with a small number of dominant native species in the herbaceous vegetation of productive, disturbed sites. Variation in the relative dominance of these species suggests high variability between sites in the factors influencing the local invasion process. In our study, we examined variation in regeneration mode, type and frequency of disturbance, and native species composition, and considered life history differences between the two invasive species as factors contributing to the distinct dominance patterns. These factors were tested in a controlled field experiment in which individuals of the two invasive species and four native species were grown in mixed stands for almost 3 years. The development of the plants was monitored by cover values and all plants were harvested at the end of the study. All factors investigated contributed considerably to the development of distinct dominance patterns in the species mixtures. Relative to the natives, both invasive species were promoted by regeneration from vegetative fragments as compared to development from sexual offspring. While both invasive species were generally promoted by disturbance relative to the natives, they differed in their response to distinct types of disturbance, and these differences were strongly affected by species composition. Our results indicate that invasion success of R. austriaca may depend more on soil disturbance, soil transport and deposition, while B. orientalis is expected to particularly expand at mown sites that do not have dense cover by meadow grasses. Whether the native resident vegetation is mainly composed of successional competitors that suffer from disturbance or of ruderal competitors that compete early and strongly with the invasive species may be of critical importance for invasion by the two species.     

Soil Disturbance as a Grassland Restoration Measure—Effects on Plant Species Composition and Plant Functional Traits

Soil disturbance is recognized as an important driver of biodiversity in dry grasslands, and can therefore be implemented as a restoration measure. However, because community re-assembly following disturbance includes stochastic processes, a focus only on species richness or establishment success of particular species will not inform on how plant communities respond ecologically to disturbance. We therefore evaluated vegetation development following disturbance by quantifying species richness, species composition and functional trait composition. Degraded calcareous sandy grassland was subjected to experimental disturbance treatments (ploughing or rotavation), and the vegetation was surveyed during four subsequent years of succession. Treated plots were compared with control plots representing untreated grassland, as well as nearby plots characterized by plant communities representing the restoration target.Species richness and functional diversity both increased in response to soil disturbance, and rotavation, but not ploughing, had a persistent positive effect on the occurrence of specialist species of calcareous sandy grassland. However, no type of soil disturbance caused the plant species composition to develop towards the target vegetation. The disturbance had an immediate and large impact on the vegetation, but the vegetation developed rapidly back towards the control sites. Plant functional composition analysis indicated that the treatments created habitats different both from control sites and target sites. Community-weighted mean Ellenberg indicator values suggested that the observed plant community response was at least partially due to an increase in nitrogen and water availability following disturbance. This study shows that a mild type of disturbance, such as rotavation, may be most successful in promoting specialist species in calcareous sandy grassland, but that further treatments are needed to reduce nutrient availability. We conclude that a functional trait based analysis provides additional information of the vegetation response and the abiotic conditions created, complementing the information from the species composition.     

Patterns of elephant impact on woody plants in the Hluhluwe-Imfolozi park, Kwazulu-Natal, South Africa

This study identifies patterns of elephant Loxodonta africana africana impacts upon tree species and woody plant communities in Hluhluwe-Imfolozi Park, a South African savannahs/woodlands area. Elephants were reintroduced there from 1981, following more than 80 years of absence. Data were collected in 2003 on elephant impact on woodland in the Park. Different vegetation types were susceptible to different types and levels of damage by elephants, suggesting that elephants will not homogenize the vegetation. Elephants targeted larger stems for all types of damage, with a strong preference for some of the less abundant species such as Albizia versicolor (breaking and toppling) and Cordia caffra and Schotia brachypetala (debarking). Elephant impacts tended to be distributed evenly across the park landscape, irrespective of stem density or proximity to permanent water. Overall, elephants have little impact on slowing or reversing the spread of undesirable woody species, but are having a marked impact on certain less common tree species and larger tree size-classes in the Hluhluwe-Imfolozi Park.