The multidimensional nature of biodiversity and social dynamics and implications for contemporary rural livelihoods in remote Kalahari settlements, Botswana

Despite rapid socio-economic development in Kalahari drylands, contemporary research suggests that biodiversity remains important as a component of the complex portfolio of livelihood strategies, as a real and perceived safety net in times of stress, and a key factor of cultural identity. The degree to which the spatially and temporally dynamic nature of biodiversity in drylands influences livelihoods is, however, little studied, particularly in socially complex contemporary rural settlements. Greater understanding in this area is required to allow better-informed design and implementation of rural development, poverty alleviation and conservation initiatives. This is particularly true in the light of predicted increases in environmental dynamism with climate change. An interdisciplinary approach was used in two environmentally and socially distinct dryland settlements in Botswana, to investigate the extent to which the dynamic biodiverse setting influences contemporary rural livelihoods. Results illustrate that biodiversity, particularly its dynamics, is of critical contemporary importance to rural settlement livelihoods, particularly in times of inner settlement scarcity. Entitlements to biodiversity dynamics were, however, bound up by complex settlement-specific social, economic and political factors. Unless such contextual within-settlement dynamics are understood, the relative importance of biodiversity in rural development and poverty alleviation strategies in contemporary Kalahari drylands may be undermined.     

The survival strategy of the alpine endemic <Emphasis Type="Italic">Primula glaucescens</Emphasis> is fundamentally unchanged throughout its climate envelope despite superficial phenotypic variability

The survival of alpine species in changing climates depends on dispersal or adaptation. However, it is unclear whether trait variability along elevation/climatic gradients is adaptive or represents stress towards lower/warmer elevations, particularly for the endangered endemics for which protected status and plant longevity preclude experimental study. We chose one such species, known for its phenotypic variability (Primula glaucescens, endemic to the southern Alps), and quantified key functional traits in situ throughout its range, correlating these with elevation as a proxy for climate. Larger leaves were evident towards lower elevations, but tissue nitrogen dilution and limited regenerative fitness were symptomatic of stress. Specific leaf area, a correlate of relative growth rate, was consistently low: the entire species exhibits conservative leaf economy and inherently slow growth. This seemingly variable species exhibits superficial variability around a fundamentally conservative, cold-adapted survival strategy, and thus phenotypic variability is unlikely to facilitate the persistence of alpine endemics during rapid climate warming. Nomenclature: Pignatti (1982).     

The abundance of large wild herbivores in a semi-arid savanna in relation to seasons, pans and livestock

Large herbivores, including livestock and ostrich, were counted along a 200-km long track in south-western Kalahari, Botswana. Altogether, 37 counts were made during different seasons. The number of animals seen and group size were recorded. These variables were compared with monthly and accumulated rainfall (number of animals and group size) and distance to pans (number of animals). Observations of game and livestock were also related to distance to villages. In four of the seven studied species, most animals were seen during the wet season. Group size also varied between seasons apart from the non-gregarious steenbok and duiker. Number of animals and group size were in some cases correlated with rainfall during the month of observation or with accumulated rainfall during the preceding months. The various species were more often observed close to pans than further away from the pans. Compared to livestock, game was on average observed >10 km further away from the villages. Few observations of game were made between village centres and the livestock observations most distant from the village.     

Monitoring the world population of the Lesser Grey Shrike (Lanius minor) on the non-breeding grounds in southern Africa

Summary The world population of the Lesser Grey Shrike funnels in from breeding grounds in Eurasia to an area that is ten times smaller on the non-breeding grounds in the thornbelt of southern Africa, chiefly in the Kalahari basin. The species is abundant in open savanna habitat on the non-breeding grounds, where it is regularly spaced in individual territories and behaves conspicuously as a perch hunter. It has declined considerably during the last 200 years, and the non-breeding grounds offer highly favourable conditions for assessing and monitoring the world population. Extrapolation according to vegetation types of stratified survey data across southern Africa indicates a world population of 6.1 million birds (95% confidence 5.0–7.3 million) during the mid 1990s. However, for sensitive monitoring, the establishment of a standard-effort index is more appropriate than the assessment of the total population.

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Monitoring der Weltpopulation des Schwarzstirnwürgers(Lanius minor) im südafrikanischen Überwinterungsgebiet

Zusammenfassung Die Weltpopulation des Schwarzstirnwürgers konzentriert sich im nördlichen Winter in dem zum eurasiatischen Brutgebiet zehnmal kleineren Gebiet der Dornbuschsteppen des südlichen Afrikas, hauptsächlich das Kalahari Becken. Dort kommt die Art vornehmlich in der offenen Savanne vor, wo sie territorial ist und typischerweise Stoßjagd von Ansitzen aus macht. Die Art hat in den letzten 200 Jahren stark abgenommen. Die hohe Konzentrierung im Überwinterungsareal erlaubt ein Monitoring der Weltpopulation. Die Weltpopulation wird nach dortigen Zählungen auf etwa 6,1 Millionen Vögel (5.0–7.3 Million; 95% Vertrauensbereich) geschätzt. Für ein regelmäßiges Monitoring des Bestandes wird die Einrichtung von Beobachtungstransekten empfohlen.

     

植物物候研究进展

植物物候直接反映了气候变化的影响,是植被动态模拟的关键.在遥感和模型技术的推动下,植物物候与全球变化关系的研究日益受到人们的关注.文中从植物物候与环境因子的相互关系、植物物候对全球变化的响应以及植物物候的遥感监测方面,综合论述了植物物候的研究进展,找出植被物候研究的不足,进而提出未来植被物候的研究方向.     

Spatial patterns and dynamics of woody vegetation in an arid savanna

The spatial distribution of woody plants was studied in an arid savanna in Botswana. The study included stands of mixed species and sizes as well as monospecific even-sized stands of different size classes of the tree Acacia erioloba and the shrub Acacia mellifera. In the case of A. mellifera both dense stands on overgrazed land and more open stands were included. The analysis used all plant-to-plant distances, and individuals were represented with a realistic canopy extension. The mixed stands showed aggregated distribution of individuals, mainly caused by strong clumping of small shrubs. In A. erioloba saplings were aggregated, small trees were randomly or regularly distributed and large trees were randomly spaced. In open stands of A. mellifera aggregation increased with size of the shrubs, while in dense stands with overgrazing aggregation decreased with increasing size. The different patterns are discussed in relation to the relative importance of inter- and intraspecific competition for water and of disturbance by fire as regulatory mechanisms for total amount and spatial distribution of woody plants in this savanna.     

Does an aridity and trophic resource gradient drive patterns of dung beetle food selection across the Botswana Kalahari?

1. Aridity gradients are paralleled by both reductions in resources and decreased species richness of animals. Across the aridity gradient of the Botswana Kalahari, a reduction in mammal species richness leads to reduced density and diversity of dung types, accompanied by reduced dung beetle species richness. We investigated whether this gradient also drives changes in dung beetle food type association and specialisation owing to a loss of some dung types to the arid southwest. 2. Dung beetles were sampled from three study sites in each of the six study areas using 2 × 10 grids of pitfall traps baited with dung (pig, elephant, cattle, and sheep) or carrion (chicken livers). 3. Canonical correspondence analysis (CCA) showed that distributions of dung beetle species between bait types deviated significantly from random associations. 4. Central Kalahari assemblages were more specialist than those at the mesic and arid extremes of the gradient. 5. Patterns of selection and specialisation to bait types differed between mesic northeast and arid southwest study areas. There were specialist faunas on carrion and more generalist faunas on ruminant herbivore dung (cattle and sheep) in each region. However, specialist species associated with elephant dung in the northeast were replaced by a more generalist fauna in the southwest with an opposite trend on pig dung. 6. Reduced species richness and high species turnover from the mesic northeast to the arid southwest is paralleled by a shift in patterns of food association that may reflect changes in the diversity of food types, particularly the absence of elephant dung from the southwest.     

气候变暖对领春木沿海拔分布潜在影响的实验模拟

在神农架山地不同海拔高度进行领春木(Euptelea pleiospermum)种子萌发实验和萌发后实生幼苗的存活状况研究,模拟气候变化对领春木分布的潜在影响.结果显示:(1)林窗内种子萌发率显著高于林下,林下的幼苗全部死亡;(2)在领春木的分布上限(2090 m)和以上区域种子萌发率高,且幼苗死亡率低,在领春木的分布下限(900 m)和以下区域种子萌发率低,且除620 m阳坡林下以外,幼苗均全部死亡;(3)种源对领春木种子萌发率和幼苗死亡率均无显著影响;(4)冬季播种的种子比春季播种种子萌发率低,萌发后幼苗死亡率高.研究结果表明,珍稀植物领春木具备向高海拔地区迁移的潜能,但向高海拔的迁移扩散可能会受到一定的限制;在低海拔区域,领春木幼苗更新受到威胁,但一些小生境可以缓冲气候变暖带来的威胁.     

Can soil temperature direct the composition of high arctic plant communities?

Abstract. Low temperatures exert a primary constraint on the growth of high arctic vascular plants. However, investigations into the impact of temperature on high arctic plants rarely separate out the role of air and soil temperatures, and few data exist to indicate whether soil temperatures alone can significantly influence the growth of high arctic vascular plants in a manner that might direct community composition. We examined the response of high arctic plants of three functional types (grasses, sedges/rushes and non‐graminoids) to manipulated soil temperature under common air temperature conditions. Target plants, within intact soil cores, were placed in water baths at a range of temperatures between 4.9 and 15.3 °C for one growing season. Grasses responded most rapidly to increased soil temperature, with increased total live plant mass, above‐ground live mass and total below‐ground live mass, with non‐graminoids having the lowest, and sedges/rushes an intermediate degree of response. The ratio of above‐ground live mass to total live mass increased in all growth forms. Grasses, in particular, responded to enhanced soil temperatures by increasing shoot size rather than shoot number. In all growth forms the mass of root tissue beneath the moss layer increased significantly and to a similar extent with increasing soil temperature. These results clearly indicate that different growth forms, although collected from the same plant community, respond differently to changes in soil temperature. As a consequence, factors influencing soil temperature in high arctic ecosystems, such as global climate change or herbivory (which leads to reduced moss depth and increased soil temperatures), may also direct changes in vascular plant community composition.