Search

Plant transpiration is a key component of the hydrological cycle that moves water from the soil through plants to the atmosphere and is largely determined by environmental conditions. The challenges of highly variable climatic conditions and water scarcity in the semi‐arid savannas of southern Africa drive trees to exhibit different water use strategies.An additional challenge for savanna trees arises from the browsing of large mammals, and its potential impact on transpiration has largely been overlooked.To assess water use strategies and the impact of browsing on transpiration in three common savanna woody species (Colophospermum mopane, Catophractes alexandri, Senegalia mellifera), we conducted an extensive field experiment in a wildlife reserve in Namibia. We established a browsing gradient ranging from 0% to 100% leaf removal to disentangle complex relationships, and we measured sap flow representing whole‐tree transpiration, stomatal conductance as a proxy for leaf level transpiration, and environmental factors including soil moisture, solar radiation, air temperature and air humidity.We discovered a unimodal relationship between browsing intensity and sap flow, consistent across all species, and peaking at low to moderate browsing levels equivalent to approximately 30% leaf removal. This universal pattern is remarkable since we found water use strategies to differ among species: Colophospermum mopane and C. alexandri exhibit a water‐saving behaviour to reduce water loss under unfavourable conditions while S. mellifera demonstrates water‐spending characteristics.The deviation from a negative linear effect of browsing does not meet the functional expectation when browsing is translated into a simple leaf area reduction. Instead, it can be attributed to stomatal adjustments that partially compensate for transpiratory surface loss. We propose that this conceptual mechanism can be generalised to other woody species and various ecosystems. In addition, common transpiration models relying solely on leaf area indices and abiotic factors can be improved by including a non‐linear relationship to reproduce the effect of browsing accurately.Our findings highlight the role of herbivores in shaping the connection between the Earth's spheres and improve our understanding of ecohydrological and vegetation dynamics in Southern African savannas. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: In this field experiment we investigate the impact of land use induced savanna degradation on movement behaviour of the spotted sand lizard (Pedioplanis l. lineoocellata) in the southern Kalahari. Foraging behaviour of lizards was tested in a factorial design (low vs. high prey availability) in degraded and non-degraded habitats. An interaction between habitat structure and prey availability affected movement behaviour. In degraded habitats with low prey availability and in non-degraded habitats with high prey availability the spotted sand lizard moved more like an active forager. In contrast, in degraded habitats with high prey availability and in non-degraded habitats with low prey availability lizards moved like sit-and-wait foragers. Interestingly, the behavioural flexibility of the spotted sand lizard seems to buffer extreme conditions and negative effects of land use impacts. [Copyright &y& Elsevier]

Abstract: Intensified land use practices have changed savannas worldwide. Both, heavy grazing-induced shrub encroachment and the decrease in tree density due to woodcutting are assumed to reduce animal diversity. However, most studies in animal ecology have focused on the effects of one of these two land use practices. In our study we analyzed the importance of both shrubs and trees, for foraging site selection of the Southern Pied Babbler (Turdoides bicolor) in the Southern Kalahari, South Africa for two different grazing regimes: endemic wildlife at Molopo Nature Reserve versus domestic livestock at neighboring farms. We compared vegetation structure at babbler foraging sites with random sites at the microhabitat scale (5×5m) and the mesohabitat scale (50×50m), and recorded babbler group size and the amount of leaf litter. Our results show for both scales that mean density of shrubs and trees was higher at foraging sites compared to random sites. We found no differences in foraging site characteristics (i.e. vegetation cover at microhabitat scale and composition and density of woody plant species at both scales) and group size between the two grazing regimes. We conclude that shrub encroachment affects the Southern Pied Babbler positively whereas woodcutting has negative effects. [Copyright &y& Elsevier]

• Hare movement behaviour was studied before and after agricultural management events. • Hares spend more time on recently harvested crop fields, but not on mown grasslands. • Management events affect hare range sizes only in areas with large crop fields. • Hares shift their ranges away or towards fields depending on the management type. • Energy expenditure of hares is unaffected by agricultural management. Agricultural landscapes are spatially and temporally dynamic habitats that force wildlife to interact with different management practices, such as harvests and mowing events which cause sudden changes in resource availability. Animals may avoid agricultural management events and the changed habitat, to search for undisturbed areas or they might use and explore such areas due to beneficial changes in vegetation structure. Further, landscape structure might influence the movement processes that are underlying reactions to agricultural management. Here we study how agricultural management events affect animal movement behaviour in two contrastingly structured agricultural landscapes. In 2014 and 2015 we collared 36 European brown hares (Lepus europaeus) with GPS-tags and accelerometers in Northeast Germany (large agricultural fields) and South Germany (small fields and comparatively more non-arable vegetation). We recorded hares' movement behaviour for 4 days before and after agricultural management events without (e.g. fertilizer application) and with (harvest and mowing) immediate changes in resource availability, on the most common production cover types (wheat, grasslands, maize and rapeseed). We measured the number of GPS points in the focal fields, the range size (area covered within 4 days), the shift in range centre, and the hares' energy expenditure (overall dynamic body acceleration). More GPS locations were found on fields following management events that affected resource availability, and less GPS fixes were recorded on the wheat fields after management events without resource changes. Compared to an equivalent period without management events, hares showed increased range shifts after harvesting maize and rapeseed fields, mowing grasslands and after management events without resource changes for most of the production cover types. Range sizes were only affected in wheat fields in Northeast Germany, where they increased after harvest and decreased after management events without resource changes. Energy expenditure was unaffected by agricultural management. Hares may profit from harvested fields, likely because they find food in form of fallen grains, improve their predator detection probability and generally prefer areas with low vegetation. The reaction to management events without the change of resources might depend on the specific type of management practices (e.g. organic vs. inorganic fertilizer). Landscape structure may play an important role as range sizes increase due to the necessity to reach distant alternative habitats. Hence, the provision of smaller fields with high crop diversity and sufficient alternative habitat patches throughout the year has the potential to maximise accessible resources and predator detection ability for hares and other farmland wildlife. [ABSTRACT FROM AUTHOR]