Refine
Year of publication
Document Type
- Article (22)
- Conference Proceeding (3)
- Other (1)
- Postprint (1)
- Review (1)
Keywords
- Dry land degradation (2)
- Functional types (2)
- Rangeland management (2)
- Simulation model (2)
- Acacia mellifera (1)
- Biodiversity experiments (1)
- Biodiversity theory (1)
- Birds (1)
- Bush encroachment (1)
- CO2 increase (1)
Structural and animal species diversity in arid and semi-arid savannas of the southern Kalahari
(2004)
Although the effects of grazing-induced savannah degradation on animal diversity are well documented, knowledge of how they affect space use or responding behaviour remains poor. In this study, we analysed space use of the spotted sand lizard (Pedioplanis l. lineoocellata) in degraded versus nondegraded habitats of southern Kalahari savannah habitats. Lizards were radio tracked, daily movement distances recorded and home range sizes calculated. In degraded Kalahari savannah habitats where plant diversity and perennial grass cover are low but shrub cover high, P. lineoocellata moves larger distances (40.88 +/- 6.42 m versus 27.43 +/- 5.08 m) and occupies larger home ranges (646.64 +/- 244.84 m(2) versus 209.15 +/- 109.84 m(2)) than in nondegraded habitats (high plant diversity, high perennial grass cover and low shrub cover). We assume that this increase in daily movement distances and home range sizes is a behavioural plasticity to limited food resources in degraded savannah habitats. Although P. lineoocellata is able to adjust to resource-poor savannah habitats, the increase in the lizard's movement activities is likely to result in a higher predation risk. This is supported by the lower availability of protective vegetation i.e. perennial grass cover. Hence, we conclude that despite behavioural plasticity of P. lineoocellata, overgrazing has a severe negative impact on the space use of P. lineoocellata.
We investigated sex-specific parental care behaviour of lesser spotted woodpeckers Picoides minor in the low mountain range Taunus, Germany. Observed parental care included incubation, nest sanitation as well as brooding and feeding of nestlings. Contributions of the two sexes to parental care changed in progress of the breeding period. During incubation and the first half of the nestling period, parental care was divided equally between partners. However, in the late nestling stage, we found males to feed their nestlings irrespective of brood size while females considerably decreased feeding rate with the number of nestlings. This behaviour culminated in desertion of small broods by females shortly before fledging. The fact that even deserted nests were successful indicates that males were able to compensate for the females' absence. Interestingly, the mating of one female with two males with separate nests could be found in the population, which confirms earlier findings of polyandry in the lesser spotted woodpecker. We conclude that biparental care is not essential in the later stage and one partner can reduce effort and thus costs of parental care, at least in small broods where the mate is able to compensate for that behaviour. Reduced care and desertion appears only in females, which might be caused by a combination of two traits: First, females might suffer higher costs of investment in terms of mortality and secondly, male-biased sex ratio in the population generally leads to higher mating probabilities for females in the following breeding season. The occurrence of polyandry seems to be a result of these conditions.
We studied the effects of overgrazing on the foraging behaviour of the lizard Pedioplanis l. lineoocellata (Spotted Sand Lizard), a sit-and-wait forager, in habitats of differing vegetation states to determine the effects of habitat degradation on this species. At high grazing intensity where vegetation cover and diversity is low, the lizard P. lineoocellata moves more frequently, spends more time moving and covers larger distances than in habitats where vegetation cover and diversity is high. These behavioural changes in movement patterns can be explained by less abundant prey in habitats with low vegetation cover and diversity. Although morphology, phylogeny and physiology of P. lineoocellata should constrain the change in foraging behaviour, the species has modified its foraging strategy from sit- and-wait to actively foraging. We assume that this behavioural flexibility of P. lineoocellata is a buffer mechanism enabling the species to use and survive in degraded (unfavourable) habitats.
Shrub encroachment linked to heavy grazing has dramatically changed savanna landscapes, and is a major form of rangeland degradation. Our understanding of how shrub encroachment affects arthropod communities is poor, however. Here, we investigate the effects of shrub encroachment on abundance and diversity of ground-dwelling (wingless) arthropods at varying levels of shrub cover in the southern Kalahari. We also ascertain if invertebrate assemblage composition changes with habitat structure and identify which aspects of habitat structure (e.g., grass cover, herbaceous plant cover, shrub density) correlate most strongly with these changes. Ant, scorpion and dung beetle abundance increased with shrub cover, whereas grasshoppers and solifuges declined. Spider and beetle abundance exhibited hump-shaped relationships with shrub cover. RTU richness within orders either mirrored abundances, or exhibited no trend. Shrub density was the habitat component most correlated with similarities between invertebrate assemblages. Ground-dwelling arthropods showed clear shifts in species assemblage composition at a similarity level of 65% according to shrub density. Changes in indicator species showed that within the Tenebrionidae (darkling beetles), certain species respond positively to shrub thickening, replacing other species within the Family. Small-bodied, wingless Scarabaeidae (dung beetles) tended to increase with increased shrub density and three species emerged as significant indicators of more thickened habitats, although this might be a response to greater dung availability, rather than habitat structure itself. We conclude that because ground- dwelling invertebrates showed such clear responses in species assemblage composition, they present excellent candidates for use as indicator species in further studies into bush encroachment.
Military areas are valuable habitats and refuges for rare and endangered plants and animals. We developed a new approach applying innovative methods of hyperspectral remote sensing to bridge the existing gap between remote sensing technology and the demands of the nature conservation community. Remote sensing has already proven to be a valuable monitoring instrument. However, the approaches lack the consideration of the demands of applied nature conservation which includes the legal demands of the EU Habitat Directive. Following the idea of the Vital Signs Monitoring in the USA, we identified a subset of the highest priority monitoring indicators for our study area. We analyzed continuous spectral response curves and tested the measurability of N=19 indicators on the basis of complexity levels aggregated from extensive vegetation assemblages. The spectral differentiability for the floristic as well as faunistic indicators revealed values up to 100% accuracy. We point out difficulties when it comes to distinguishing faunistic habitat requirements of several species adapted to dry open landscapes, which in this case results in OVERALL ACCURACY of 67, 87-95, and 35% in the error matrix. In summary, we provide an applicable and feasible method to facilitating monitoring military areas by hyperspectral remote sensing in the following. (C) 2014 Elsevier Ltd. All rights reserved.
While several empirical and theoretical studies have clearly shown the negative effects of climate or landscape changes on population and species survival only few of them addressed combined and correlated consequences of these key environmental drivers. This also includes positive landscape changes such as active habitat management and restoration to buffer the negative effects of deteriorating climatic conditions. In this study, we apply a conceptual spatial modelling approach based on functional types to explore the effects of both positive and negative correlations between changes in habitat and climate conditions on the survival of spatially structured populations. We test the effect of different climate and landscape change scenarios on four different functional types that represent a broad spectrum of species characterised by their landscape level carrying capacity, the local population turnover rates at the patch level (K-strategies vs. r-strategies) and dispersal characterstics. As expected, simulation results show that correlated landscape and climatic changes can accelerate (in case of habitat loss or degradation) or slow down (in case of habitat gain or improvement) regional species extinction. However, the strength of the combined changes depends on local turnover at the patch level, the overall landscape capacity of the species, and its specific dispersal characteristics. Under all scenarios of correlated changes in habitat and climate conditions we found the highest sensitivity for functional types representing species with a low landscape capacity but a high population growth rate and a strong density regulation causing a high turnover at the local patch level.
The relative importance of habitat loss or habitat degradation, in combination with climate deterioration, differed among the functional types. However, an increase in regional capacity revealed a similar response pattern: For all types, habitat improvement led to higher survival times than habitat gain, i.e. the establishment of new habitat patches. This suggests that improving local habitat quality at a regional scale is a more promising conservation strategy under climate change than implementing new habitat patches. This conceptual modelling study provides a general framework to better understand and support the management of populations prone to complex environmental changes.