Comparing biodiversity between protected savanna and adjacent non-protected farmland in the southern Kalahari     

Bernd Wasiolka  Niels Blaum 《Journal of Arid Environments》2011,75(9):836-841

In this study we investigated the effect of different land use options (wildlife versus livestock) on species richness of plants and reptiles in the protected Kgalagadi Transfrontier Park (KTP) versus adjacent non-protected farmland within the same savanna habitat type (Aoub dune veld) in the southern Kalahari, South Africa. Our results show that both plant and reptile species richness as well as plant cover and reptile abundance was significantly higher in the protected KTP than in the non-protected farmland. The higher proportion of shrub but lower proportions of perennial grass cover, herb cover, and herb species richness in the farmland can be explained by higher stocking rates and the differences in feeding behaviour between native wild ungulates (e.g. Antidorcas marsupialis, Oryx gazella) and livestock (mainly sheep). The reptile’s prey availability and microhabitats (perennial grass tussocks and rodent burrows) for thermoregulation and protection against predators were significantly lower in the farmland. To conclude, our results clearly show that long term effects of different land use options (wildlife in protected KTP versus extensive livestock production in the non-protected farmland) even within the same habitat type have led to significant changes in vegetation composition, availability of microhabitat structures and in the reptile community.  相似文献   

Spatial patterns of the soil seed bank and extant vegetation across the dry Minjiang River valley in southwest China     

Y.J. Li  W.K. Bao  N. Wu 《Journal of Arid Environments》2011,75(11):1083-1089

The medium-scale spatial patterns of soil seed banks (SSBs) and extant vegetation and the roles of abiotic factors are poorly understood. We selected the dry Minjiang River valley of southwest China to investigate SSB structure and corresponding extant vegetation in a medium-scale size (200-230 km long, 3-4 km wide) at eight sites across the valley using a germination method and field surveys. We found that, there was low seed density and species number in SSB and less coverage and litter thickness for community in extant vegetation at central sites compared with transitional sites across the dry valley; Quercus spp. occurred frequently in extant vegetation at transitional sites, while Caryopteris spp., Jasminum spp., Rabdosia parvifolia, Sophora davidii, Campylotropis spp., and Bauhinia faberi var. Microphylla was present frequently at central sites; Carex spp. and Artemisia spp. occurred frequently in SSB at transitional sites, while Ajania spp., Poa spp., and Fagopyrum caudatum was present more frequently at central sites. Hierarchical cluster analysis and Kendall’s correlation showed that the spatial variation of both SSB and extant vegetation had significant correlation with rainfall and air evaporation.  相似文献   

万木林青年和老龄常绿阔叶林乔木层碳贮量分配特征     

黄蓉  王超  杨智杰  陈光水 《福建地理》2011,(2):29-35

了解森林生物量碳分配特征,对于森林碳贮量和碳汇估算、森林碳汇经营和生物多样性保护有重要意义.本课题选择福建省万木林自然保护区青年(约47 a生)和老龄(约120 a生)常绿阔叶林为研究对象,根据生物多样性调查结果和生物量异速方程,计算乔木层生物量碳贮量,并分析其高度级、径级和树种间的分配特征.结果表明:1)青年林碳贮量为115.03 t.hm-2,老龄林碳贮量为224.43 t.hm-2;2)青年林最大碳贮量出现在高度级Ⅶ级(15～17 m),为23.17 t.hm-2,而老年林最大碳贮量出现在高度级Ⅷ级(17～19 m),为62.96 t.hm-2;3)青年林中Ⅵ级(15 cm≤DBH<17 cm)的碳贮量最高,为34.25 t.hm-2,占总碳贮量的29.77%;在老龄林中最高碳贮量集中在XIX级(DBH≥41 cm),为60.03t.hm-2,占总碳贮量的26.78%;4)2个林分绝大部分碳贮量都集中在少数树种,大多数物种对碳贮量的贡献很微小.  相似文献   

Living on the edge? - On the thermobiology and activity pattern of the large herbivorous desert lizard Uromastyx aegyptia microlepis Blanford, 1875 at Mahazat as-Sayd Protected Area, Saudi Arabia     

T.M. Wilms  P. WagnerM. Shobrak  D. RödderW. Böhme 《Journal of Arid Environments》2011,75(7):636-647

Field active body temperatures (T_b) and operative temperatures (T_e) were assessed in a population of Uromastyx aegyptia microlepis at Mahazat as-Sayd Protected Area, Saudi Arabia. In summer T_b ranged between 23.2 and 47.2 °C, in winter between 23.0 and 45.1 °C and in spring between 25.5 and 45.9 °C. There is a significant difference between respective T_b and T_e distributions which suggests that U. a. microlepis is an active thermoregulator. Above ground activity is very variable between seasons, with the highest activity level in spring. In winter the animals showed an unimodal activity profile. In spring and summer the lizards exhibit bimodal activity profiles with afternoon activity being generally lower than morning activity levels. Species distribution models were calculated to estimate the future impact of global warming on this taxon. Estimates on the basis of temperature data suggest that the range size on the Arabian Peninsula might be stable but with a remarkable decrease of environmental suitability of up to 70-80%. Based on a synthesis of thermo-ecological data and species distribution models we consider climate warming as a potential threat to the survival of the species.  相似文献   

Macroinvertebrate communities in two salt affected tributaries of the Hopkins Rives,Victoria     

B. D. Mitchell  K. Richards 《International Journal of Salt Lake Research》1992,1(1):81-102

Macroinvertebrate communities were studied in two saline tributaries of the Hopkins River, western Victoria. Monthly sampling from May to August, 1990, showed the mean salinity of Bushy Creek was 5 g L⁻¹ while in Back Creek mean salinity varied from 9 to 20 g L⁻¹ between sites. Macroinvertebrate species richness and relative abundance were measured on each sampling occasion. Cluster analysis showed that community composition varied between creeks and between sites within a creek. Bushy Creek sites were more similar to each other than to Back Creek sites. A negative relationship was found between site salinity and species richness over the range 4 to 26 g L⁻¹, although there was a wide range of salinity (up to 12 g L⁻¹) over which the relationship of species richness to salinity was not clear cut. The effects of salinity on species richness in stream communities appear to be similar to that described elsewhere in salt lakes.  相似文献   

Fire and ecosystem heterogeneity: A mediterranean case study     

Pua Kutiel 《地球表面变化过程与地形》1994,19(2):187-194

The response of a Mediterranean ecosystem to fire is summarized in this paper. The results were obtained over a 3-year period at sites with a known fire history on Mt Carmel, Israel. The results give some idea of the complexity and variability of the ecosystem response to fire, and about factors that could determine these responses. It also shows how fire increases species and landscape diversity.  相似文献   

Assessing regional differences in predation of endangered species: Implications from Texas populations of the endangered star cactus (Astrophytum asterias)     

《Journal of Arid Environments》2013

Understanding threats to endangered species is one of the most critical components of implementing a successful recovery plan. For the endangered star cactus Astrophytum asterias, both mammalian and insect herbivory have been documented as a major threat to populations in Mexico. Herein, we focus on populations of A. asterias in Texas, examining how mortality threats differ from populations found in Mexico as well as among sites within Texas. Our study supports insect and mammalian herbivory as a major threat to A. asterias in Texas, with reductions in population sizes ranging between 16 and 54%. However, our study highlights that both regional and local differences can influence rates of mortality even in a range-restricted species such as A. asterias and highlights the need to assess threats at both of these levels for effective development and implementation of endangered species recovery plans.  相似文献   

The effects of enclosures and land-use contracts on rangeland degradation on the Qinghai–Tibetan plateau     

《Journal of Arid Environments》2013

Rangeland degradation on the Qinghai–Tibetan Plateau is a growing concern, often attributed to climate change and overgrazing. A minority of researchers have suggested instead that degradation may be caused by changes in land management, particularly enclosures and the contracting of long-term rangeland use rights to households. However, these claims have been hampered by a lack of empirical evidence. This field experiment is the first to compare rangeland conditions over time in the case of different management regimes on the Qinghai–Tibetan Plateau, specifically single-household versus multi-household management. A survey of vegetation properties in Maqu County, Gansu province in 2009, and repeated in 2011, examined the differences between single- and multi-household management in terms of vegetation biomass, cover, and species richness. In 2009, the biomass of the sedge group under multi-household management was significantly higher than that under single-household management. In 2011, biomass, vegetation cover, and species richness were all significantly higher under multi-household management than single-household management. These data suggest the flaws of the tragedy of the commons assumptions underlying single-household management.  相似文献   

北黄海盆地LV井侏罗系烃源岩特征及油源对比     

赵青芳  李双林  温珍河  龚建明  肖国林  吴亮亮 《沉积学报》2016,34(4):794-802

对北黄海盆地LV井中、上侏罗统烃源岩及上侏罗统原油（油砂抽提物）进行常规有机地球化学分析和碳同位素测试,分析研究烃源岩和原油的地球化学特征并探讨原油的来源问题。测试结果显示,侏罗系烃源岩达成熟-高熟阶段,有机质类型以Ⅲ型为主。中侏罗统烃源岩有机碳含量较高,但生烃潜能、氯仿沥青“A”及总烃含量低值,属于差的烃源岩。干酪根碳同位素总体偏重（-24.4‰～-23.5‰）,与原油碳同位素特征（-29‰左右）差异显著,排除与原油的母岩关系。上侏罗统烃源岩有机碳含量较中侏罗统低,但生烃潜能、氯仿沥青“A”及总烃含量高值。上侏罗统烃源岩抽提氯仿沥青“A”碳同位素（-26‰～-21.5‰）特征、单体烃碳同位素分布模式及甾萜烷生物标志物特征都与原油相似,综合分析认为原油应该来源于上侏罗统中干酪根类型较好、母质为混源的成熟烃源岩。  相似文献   

Adaptive management,international co-operation and planning for marine conservation hotspots in a changing climate     

《Marine Policy》2015

The aim of this study is to predict changes in the distribution and extent of habitat forming species defined as “Priority Marine Habitats” (PMHs) in the North-East (NE) Atlantic under future scenarios of climate-induced environmental change. A Species Distribution Modelling method was used for each PMH to map the potential distribution of “most suitable” habitat. The area and percentage cover was calculated within each country׳s Exclusive Economic Zone for the baseline (2009) and the projected (2100) years. In addition, a conservation management score was calculated based on the number of PMHs that co-occur in assessment units. Overall, this study reveals the potential for movement and/or change in the extent of some PMHs across the NE Atlantic under an increased ocean temperature scenario (4 °C) by 2100. There are regional differences in the predicted changes and some countries will experience greater/different changes than others. The movement of biodiversity hotspots (where one or more PMHs occur in the same broad area) provides both opportunities and risks for conservation management that are discussed. Co-operation between neighbouring countries and marine regions will require substantial enhancement in order to provide a robust adaptive management strategy going forward.  相似文献