共查询到20条相似文献,搜索用时 13 毫秒
1.
Regional weathered-zone goundwaters in the southern part of Western Australia are primarily stored in a granular saprolite aquifer derived from the isovolumetric weathering of granitic and gneissic rocks. Recent drilling has confirmed the existence of permeable materials capable of yielding groundwater of a suitable quality for livestock. Development of supplies of 10 to 250 kl d −1 is realisic and would complement local livestock, domestic and Government water supply systems. Wheatbelt aquifers currently supply 18 to 25 per cent of all water used for livestock in the agricultural areas of the southern part of Western Australia, although less than 1 per cent of the available resource is being utilized. Unused groundwater, artificially recharged by water-use inefficiencies of agricultural development, provides both a potential resource and a cause of soil and water quality deterioration. Groundwater pumping may provide one method of aquifer control to mitigate the influence of secondary salinization. Pumping the low transmissivity Wheatbelt aquifers provides a means to lower water-tables and limit the volume of groundwater reaching saline discharge areas at low points in the landscape. Unlike aquifer pumping systems developed in saline discharge areas, extraction systems in groundwater recharge areas, or in saline areas where groundwaters are of a suitable quality for agricultural use, can be used to mitigate salinity. The volume of groundwater available in southwestern Western Australia usually exceeds livestock requirements, to maintain low water-tables, the water has either to be pumped to suitable drainage systems or alternative uses must be sought. 相似文献
2.
We present a procedure for the selection of a network of reserves representing the biological diversity of a large and biologically poorly known region. The quantitative analysis gives equal weighting to a wide array of different species: mobile and sessile, long-lived and ephemeral, heterothermic and homeothermic, etc. Sampling was based on quadrats that were positioned through the region using a stratified random strategy. This provided a presence-absence matrix of the species composition at each quadrat. Numerical pattern analysis was used to identify 14 species assemblages and to re-order the sites and species in the data matrix. The geographic pattern of each assemblage throughout the region was described by contouring assemblage richness, the isolines being the proportion of the number of species in each assemblage. The data matrix was re-examined. Some assemblages exhibit several gradients in species composition. For example, a 0·1 isoline in the east may represent a different 10% of species than a 0·1 isoline in the west. Other assemblages exhibit only a single gradient in species composition. The results were used to select the optimum positions of reserves needed to represent the compositional diversity of each of the 14 species assemblages. Limited field checking confirmed the predicted isolines in assemblage compositional richness to a satisfactory extent. 相似文献
3.
对伊洛河流域典型地段植被景观格局变化定量分析研究结果表明 ,该区域森林覆盖面积有所增加 ,但景观破碎化程度严重 ,斑块数目猛增 ,斑块平均面积减小且各类型斑块形状日趋简单 ;但斑块空间分布趋于均匀 ,斑块分布状况也逐步集中化。 相似文献
4.
Understanding the causes, processes and ecological consequences of land use change is a conservation priority in fragmented, human dominated landscapes but is often difficult due to insufficient environmental and social data or data at different spatial scales. We assessed changes in the extent of relictual native grasslands in western Victoria, Australia, by comparing native grasslands recorded by targeted vegetation surveys in the 1980s and early 1990s, with those present in 2004. Of the 880 ha of native grassland recorded by the earlier surveys, approximately 225 ha were destroyed by 2004. The area of grassland on road reserves was reduced by 169 ha (36%), with 67 ha (32%) and 18 ha (14%) lost from private property and Crown land, respectively. However, due to incomplete surveys in 1984, the area of private native grassland destroyed is likely to have been severely underestimated. Bayesian logistic regression models determined that social factors had a greater influence on the probability of native grassland destruction than environmental variables (i.e. soil type, distance to stream). The conservation ranking of native grassland patches and the fire brigade area the patch was located in were found to be particularly important. These results highlight the destructive effect of altering roadside fire prevention techniques from controlled burning to herbicide spraying, but suggest that this change is due to a complex interaction of social, economic and cultural factors. 相似文献
5.
为了解决我国西南地区石漠化治理过程中,社会经济效益难以量化的现状,以六枝特区为例,从土地利用、产业结构、总产值增长率、产值结构、消费结构、人均纯收入增长率6方面,选取16个因素作为评价指标,构建石漠化治理区社会经济效益定量评价体系。借助层次分析法确定权重,运用递阶多层次综合评价法建立评价模型,对研究区社会经济效益进行定量评价。结果表明:土地利用、产业结构、总产值增长率、产值结构、消费结构、人均纯收入增长率等指标的评价指数均随时间呈上升趋势,土地利用指标指数从0.807 4上升到0.862 3;产业结构指标指数从0.470 8上升到0.598 6;总产值增长率指数从0.568 4上升到0.804 8;产值结构指数从0.625 6上升到0.599 9;消费结构指数从0.666 1上升到0.770 7;人均纯收入增长率指数从0.380 9上升到0.733 2。六枝特区治理工程带来的社会经济效益评价指数呈逐年上升趋势,从2008年的0.533 3上升到2013年的0.672 0,石漠化治理工程已见成效。 相似文献
6.
As in all parts of the globe, rapid climate change in Australia will have significant negative impacts on biodiversity. It also will interact with pre-existing stressors such as native vegetation clearing, altered natural disturbance regimes and invasive species - all of which already have major negative effects on biota in Australia. Strategies to reduce climate change impacts on Australian biodiversity include a mixture of mitigation and adaptation actions ( sensuMillar et al., 2007) such as: (1) significantly reducing greenhouse gas emissions, (2) ensuring bio-diverse carbon capture, (3) better tackling pre-existing stressors on biodiversity, (4) better preparing for the effects of major natural disturbances, (5) significantly improving off-reserve conservation efforts including fostering appropriate connectivity, and (6) enhancing the existing reserve system by making it more comprehensive, adequate and representative. The first strategy above demands a global response otherwise major mitigation attempts in Australia that are not paralleled elsewhere around the world will have little effect on climate change and, in turn, contribute little to enhanced biodiversity conservation. Strategies 2-6 demand multi-scaled responses, particularly at a regional level, given the major regional differences in direct climate change impacts and their interactions with pre-existing regional stressors. Well developed multi-scaled conservation plans to implement these strategies currently do not exist, nor do appropriate institutional arrangements and capacities. Institutional reforms are urgently needed in Australia to develop the land management, monitoring and regional response capabilities required to conserve biodiversity on a continent already significantly modified. 相似文献
7.
Across the deforestation frontier in eastern Amazonia, we examined the relationship between edge-related forest desiccation and deforestation patterns using remote-sensing techniques. Canopy-moisture levels were estimated over an eight-year period in three study sites that encompassed ∼100,000 km 2 in area. We found four main effects of deforestation on dry-season canopy desiccation. First, intact forests showed no detectable change in canopy water content whereas forests adjacent to clearings showed significant water loss. Second, the distance to which edge-related desiccation penetrated into forest interiors varied among landscapes with differing forest loss and fragmentation. In moderately fragmented landscapes (with 65% and 51% remaining forest cover), canopy desiccation extended 1-1.5 km into forest interiors, whereas in heavily fragmented landscapes (20% forest cover) desiccation penetrated up to 2.7 km into forests. Third, the magnitude of edge-related desiccation varied among landscapes with differing fragmentation. Moderately fragmented landscapes exhibited a greater magnitude of change in canopy-water loss over the first 1 km from an edge than did heavily fragmented landscapes. Finally, forest desiccation penetrated further into forests over time in the moderately fragmented landscapes, but not in the heavily fragmented landscape, where edge-related desiccation had evidently ‘saturated’ remaining forests. We conclude that protracted dry seasons will have far more serious effects on fragmented than intact rainforests, with the former becoming highly vulnerable to destructive fires. With ∼30,000 km of new forest edge being created annually in Brazilian Amazonia, these finding have serious implications for forest conservation. 相似文献
8.
为研究黄土高原丘陵沟壑区不同植被恢复方式下的土壤水分特征,以天水典型对比小流域——桥子西沟(自然恢复的荒草地)和桥子东沟(人工恢复的刺槐林地)为例,基于2流域5-8月0~ 100 cm深度土壤质量含水量和氢氧同位素浓度,定量分析不同植被恢复方式下降水和坡向对土壤水分影响.结果表明:以刺槐林地为主的流域土壤含水量低于以荒草地为主的流域(16.72%)约3.70%,对降水量的响应较弱,各土层含水量变异系数较高.土壤水分存在临界变化深度,刺槐林地为主的流域在10 cm以下含水量趋于稳定,最大蒸发深度为55 cm,荒草地为主的流域在30 cm以下含水量开始增加,最大蒸发深度为30 cm.两流域含水量均遵循阴坡>半阴坡>半阳坡,δo18的分布不符合这一规律.以刺槐林地为主的流域含水量随坡向变化较小,而以荒草地为主的流域受坡向影响较大,坡向对土壤水分的影响受植被因子的制约.以自然恢复荒草地为主的恢复方式可以较好的增加土壤水库蓄水量,有利于流域生态的可持续发展. 相似文献
9.
为了确定水资源不足地区植被恢复潜力和水土保持林建设目标,在黄土丘陵半干旱区宁夏固原上黄试区,对相同立地条件的16年生人工柠条林进行疏伐,建立不同密度林地,进行林分密度、森林植被水土保持效益和土壤水分关系的定位实验。结果表明:平均基径随密度的增加而减少,二者为线性关系;盖度随密度的增加而增大,盖度与密度为对数关系;林冠截留随密度的增加而增大,二者为指数关系;地表径流随密度的增加而减少,二者为对数关系;泥沙含量随密度的减少而增加,二者关系可用倒S形曲线描述。虽然密度增加,盖度增加,森林植被水土保持效益增强,但是受土壤水资源的限制,柠条林有一个最大恢复限度。当超过限度时,势必会引发或加剧土壤旱化。 相似文献
10.
Fire affects large parts of the dry Mediterranean shrubland, resulting in erosion and losses of plant nutrients. We have attempted to measure these effects experimentally on a calcareous hillside representative of such shrubland. Experimental fires were made on plots (4 m × 20 m) in which the fuel was controlled to obtain two different fire intensities giving means of soil surface temperature of 439°C and 232°C with temperatures exceeding 100°C lasting for 36 min and 17 min. The immediate and subsequent changes induced by fire on the soil's organic matter content and other soil chemical properties were evaluated, together with the impact of water erosion. Seven erosive rain events, which occurred after the experimental fires (from August 1995 to December 1996), were selected, and on them runoff and sediment produced from each plot were measured. The sediments collected were weighed and analysed. Taking into account the variations induced by fire on the soil properties and their losses by water erosion, estimates of the net inputs and outputs of the soil system were made. Results show that the greatest losses of both soil and nutrients took place in the 4 months immediately after the fire. Plots affected by the most intense fire showed greater losses of soil (4077 kg ha ?1) than those with moderate fire intensity (3280 kg ha ?1). The unburned plots produced the least sediment (72.8 kg ha ?1). Organic matter and nutrient losses by water erosion were related to the degree of fire intensity. However, the largest losses of N‐NH 4+ and N‐NO 3– by water erosion corresponded to the moderate fire (8.1 and 7.5 mg N m ?2, respectively). 相似文献
11.
The condition of salmon gums Eucalyptus salmonophloia with large hollows in them in a 15-ha patch of remnant salmon gum-York gum E. loxophleba woodland in the northern wheatbelt of Western Australia was examined in 1978. The patch was an important breeding area for six species of cockatoo, including two endangered species. The patch was revisited in 1981 when the condition of all 682 salmon gums and York gums in the patch was examined and each was measured and photographed. A further visit was made in 1997 when the condition of the surviving trees was examined and each was again measured and photographed. The condition of the trees at each visit was classified as “good”, “staghorn”, “broken top”, “dead” or “fallen.” Over the period of the study there was a serious decline in the condition of the trees, with few large trees in the “good” category by 1997. The decline was particularly marked between 1978 and 1981 after a period of well-below average annual rainfall. Using data based on the rate of decline over the period 1978-1997, predictions were made of the fate of the trees in the patch. By 2125 only 46 (11% of the 1981 total) salmon gums were predicted to be alive with only one in the “good” category. Only 16 (17%) York gums were predicted to be alive by 2125, with only one in the “good” category. There was no evidence of any regeneration of woodland trees since 1929 when the patch was isolated by clearing for agriculture, and domestic livestock allowed to graze the patch. This deterioration of the dominant trees in the patch is symptomatic of remnant native vegetation over vast areas of Australia's extensively cleared wheat-sheep regions. The future of woodland patches like the one studied is bleak, as is the future of animals dependent on them for food, breeding sites and shelter. Active management, including fencing to exclude domestic livestock and measures to encourage regeneration of native plant communities, is necessary to counter the present regime of benign neglect that characterises most of Australia's management of native vegetation in agricultural landscapes. 相似文献
12.
Ecosystems of northern North America existed without earthworm fauna until European settlers arrived and introduced European species. The current extent of invasion by some of these species, Lumbricus terrestris L., Octolasion tyrtaeum Savigny and Dendrobaena octaedra Savigny, into an aspen forest in the Canadian Rocky Mountains and the effects of the invasion on soil chemistry, microflora, soil microarthropods and vegetation were investigated. Densities of earthworm species, soil structure, plant coverage and abundance were determined along three transects starting at the edge of the forest. At locations with L. terrestris, litter was incorporated into the soil, and where O. tyrtaeum was present, organic layers were mixed with mineral soil layers. Organic layers disappeared almost entirely when both species occurred together. Carbon and nitrogen concentrations were reduced in organic layers in the presence of L. terrestris and O. tyrtaeum. Microbial biomass and basal respiration were reduced when L. terrestris and O. tyrtaeum were present, presumably due to resource competition and habitat destruction. Microarthropod densities and the number of microarthropod species were strongly reduced in the presence of O. tyrtaeum (−75% and −22%, respectively), probably through mechanical disturbances, increasing compactness of the soil and resource competition. The coverage of some plant species was correlated with earthworm abundance, but the coverage of others was not. Despite harsh climatic conditions, the invasion of boreal forest ecosystems by mineral soil dwelling earthworm species is proceeding and strongly impacts soil structure, soil chemistry, microorganisms, soil microarthropods and vegetation. 相似文献
13.
This study employs the Coordination of Information on the Environment (CORINE) model with geographic information system to assess soil erosion risk for restoring and protecting areas within the Bonrod Zangane watershed, western Shiraz, Iran. Actual soil erosion risk was determined by combining two main parameters including potential soil erosion risk and vegetation cover. The potential soil erosion risk was generated by integrating soil erodibility, erosivity and slope parameters. Soil texture, depth and stoniness layers were overlaid to form a soil erodibility map. Modified Fournier index and Bagnouls–Gaussen aridity index were integrated to generate the erosivity layer. The slope classes also were generated from digital elevation model. In order to estimate vegetative land cover, the normalized difference vegetation index (NDVI) was used. The raster-based layers were then integrated to produce erosion risk map. The results showed that 34.7% of the study area has high and only 31.4% of the study area has low soil erosion risk. It is concluded that CORINE model can be used to delineate the soil erosion risk and also to discriminate the potential soil erosion risk areas. 相似文献
14.
The aim of this investigation was to compare the influence of naringin versus red grapefruit juice on plasma lipid levels and plasma antioxidant activity in rats fed cholesterol-containing and cholesterol-free diets. The antioxidant activity of a correlated quantity of red grapefruit juice was higher than that of naringin. Forty-two male Wistar rats were randomly divided into six groups of 7 named control, naringin, grapefruit, Chol, Chol/naringin, and Chol/grapefruit. The rats of the control group were fed basal diet (BD) and 1-2 mL of distilled water. To the BD of the other five groups were added 0.46-0.92 mg of naringin dissolved in 1-2 mL of distilled water (naringin), 1-2 mL of red grapefruit juice (grapefruit), 1% of nonoxidized cholesterol (NOC) and 1-2 mL of distilled water (Chol), 1% of NOC and 0.46-0.92 mg of naringin in 1-2 mL of water (Chol/naringin), and 1% of NOC and 1-2 mL of red grapefruit juice (Chol/grapefruit). After 30 days of different feeding, it was found that diets supplemented with red grapefruit juice and to a lesser degree with naringin improved the plasma lipid levels mainly in rats fed cholesterol and increased the plasma antioxidant activity. In conclusion, naringin is a powerful plasma lipid lowering and plasma antioxidant activity increasing flavonone. However, fresh red grapefruit is preferable than naringin: it more effectively influences plasma lipid levels and plasma antioxidant activity and, therefore, could be used as a valuable supplement for disease-preventing diets. 相似文献
15.
Savanna landscapes across north Australia are characterised by limited topographic variation, and in the Northern Territory, by a relatively constant decline in rainfall with distance inland. The North Australian Tropical Transect (NATT) traverses this 1000 km gradient of largely intact vegetation which provides an ideal ‘living laboratory’ and framework to investigate the influence of vegetation structural and floristic change and climate drivers on land-atmosphere exchange at a regional scale. We conducted a multidisciplinary program examining carbon, water and energy fluxes as a function of climate and vegetation change along a sub-continental environmental gradient. Initial findings are reported in this Special Issue. During the program, an intensive field campaign was undertaken during the dry season to characterise vegetation and soil properties of eight flux tower sites used to describe spatial and temporal dynamics of fluxes across this gradient. This paper provides an overview of the savanna landscapes of north Australia detailing vegetation structural and physiological change along this gradient. Above-ground woody biomass, stem density, overstorey LAI and canopy height declined along sites that spanned an 1100 mm annual rainfall gradient. Biomass ranged from 35 to 5 t C ha −1 with dry season LAI ranging from ∼1 to 0.05 across savanna sites both intact and cleared for grazing. Across open-forest and woodland savanna, basal area ranged from 9.7 to 5.3 m 2 ha −1. While structural change was significant and correlated with rainfall, leaf scale physiological properties (maximal photosynthesis, Vcmax, ci/ ca, light use efficiency) of the dominant woody species showed little variation, despite the significant environmental gradient. It is likely that changes in structural properties dominate spatial patterns of flux as opposed to physiological plasticity or species differences along this gradient. 相似文献
16.
在综述已有研究的基础上,结合实地调查,初步分析了水土保持对植被演替影响的主要方式,不同水土保持措施(工程措施、人工恢复植被、水土保持生态自我修复)对植被演替所产生的影响。结果表明,水土保持生态自我修复下的植被演替趋向自然演替过程,而人工恢复植被的影响取决于物种选择与营造方式,不当的物种及纯林营造,往往使植物群落结构单一化,植被正常演替中断或逆向发展。反之,则可促进植被正常演替,缩短植被恢复过程。工程措施对植被演替的影响,可能更多地表现其对植物群落空间分布格局方面。但要全面科学地认识和评价水土保持对区域植被演替的影响,仍需系统的调查研究。 相似文献
17.
For many populations and species, population viability analysis (PVA) plays a critical role in developing defensible conservation strategies and recovery plans. Although technical aspects of PVA have been well scrutinized, misapplication of PVA and misinterpretation of its results have received less attention. To illustrate potential hazards of improper use of PVA we reanalyzed data from a recent study on viability of wolves in Algonquin Provincial Park (APP), Ontario, Canada. The original PVA predicted extirpation of wolves from APP and prompted both a ban on wolf harvesting in a 10-16 km buffer zone surrounding the 7571 km 2 park and an intensive research program to evaluate efficacy of the ban. Our reanalysis showed that limited and imprecise wolf population density and demographic rate estimates, as well as flawed population assessment and reconstruction methods, led to overly pessimistic evaluation of wolf population status in APP. In fact, our analyses suggest that wolves in APP are unlikely to decline significantly over the next 20 years. Further, contrary to earlier conclusions we suggest that rapid wolf population recovery following protection from human exploitation would be likely and readily detectable. These findings highlight the need for adequate data, appropriate methodology, and proper analytical context when conducting PVA. Because the original PVA prompted substantial redirection of staff and financial resources from other significant conservation initiatives, we conclude that improper PVA may undermine execution of effective wildlife management and ultimately provide a disservice to conservation biology. 相似文献
18.
Geopedology, using geomorphologic and supervised classification bases, has been proposed as a soil surveying method. It undertakes a systematic approach to map soilscapes. This approach tries to reduce the budget of accomplishing soil surveys as well as increasing the purity of mapping units. But to what extent it has been succeeded is the question. The main objective of this research was to validate the geopedological mapping methodology by statistical and geostatistical methods in the Borujen region, Central Iran. After a primary interpretation of the study area on air photos (1:20 000 scale), 94 pedons were excavated on a 125 m square sampling grid in the sample area for geostatistical studies. To achieve the statistical aims, a geomorphic unit which encompassed the maximum surface of the sample area (and also the study area) was selected and the biggest delineation of this unit with 19 pedons was considered. The credibility of generalizing the results of the geopedological approach for the studied unit was tested by comparison with 15 pedons in a similar unit outside the sample area, named the validation area. Properties of the soils, including percentage of clay, rock fragments (2–75 mm) and total carbonates in the soil family control section, percentage of organic matter in the A horizon and its thickness, were selected for statistical and geostatistical analyses. Univariate and multivariate statistical analyses obtained from the units in the sample and the validation areas, showed that the means of soil variables were similar. A high difference between A horizon thickness variances in the sample area and the validation area affected the significance of the variation test in the univariate and multivariate results. Our study demonstrated that, when comparing the same factors from sample and validation areas, the spatial distribution and spatial dependency level of soil attributes were different. Therefore, although the geopedological approach tries to distinguish more homogeneous soil mapping units, it is still not able to fully define and represent the real variability of soil properties and show the chaotic behavior or nature of the soils. We recommend further investigations on different techniques of stratifying the landscape in order to better analyze and understand the soil-forming processes and the nature of soil variability and to improve sampling and mapping approaches. We suggest that the additional determination of the phases of landforms and phases of soil series will improve mapping in the future. 相似文献
19.
荷兰Cabauw地区一个 10km10km区域内的四种主要土壤的水动力学参数用一种实验室直接测定法 (Wind氏蒸发法 )和两种间接方法 (分段土壤推导函数、连续土壤推导函数)确定 ,而该区域水动力学特性参数的整合则采用两组方案 (聚合土壤参数法和有效土壤参数法 )进行。一个SVAT模型的模拟输出结果感热通量、潜热通量与实测数据的比较分析表明 :(1)对于用分段土壤推导函数确定的土壤水动力学参数的区域整合 ,以逆模拟法(有效土壤参数法 )较为可行 ,其模拟感热、潜热的精确性接近参比方案 (模拟 平均法) ;(2 )对于实验室直接测定的参数 ,则以几何平均vanGenuchten Mualem经验公式参数的方案 (聚合土壤参数法 )为佳 ;(3)对于连续土壤推导函数推导的水动力学参数 ,几何平均土壤组分方案 (聚合土壤参数法 )和逆模拟法方案 (有效土壤参数法 )二者均可得到优于参比方案 (模拟 平均法)的模拟结果 ,其中以前者最佳 ;(4 )所有区域化参数整合方案中 ,以水平几何平均区域内实验室直接测定的参数的方案最优 ;同时 ,连续土壤推导函数法的土壤组分几何平均方案的模型输出精确性接近该最优方案 相似文献
20.
International experience of Policy Councils on food and nutrition has developed over recent decades but they have not received the attention that is due to them. The 1992 International Conference on Nutrition recommended that governments create Food Policy Councils but few have been created. There has been more experience in local and sub-national policy councils, particularly in North America. Developing country experience of attempting to improve food policy integration stems from the 1970s. The UK's House of Commons' (Parliamentary) Health Committee, in its 2004 report on obesity, reviewed current policy determinants of the rise in obesity, concluding that national food and health policy lacked coherence, integration and effectiveness. To address this vacuum, it proposed the creation of a new 'Council of Nutrition and Physical Activity to improve co-ordination and inject independent thinking into strategy'. The case for creating such a Council in the UK is reviewed, as are possible organisational options, functions and remit. A Council could be created under the forthcoming Public Health Act. The purpose of the new Council would be to provide independent advice and strategic advice as well as monitor the linkages between policies on food, nutrition and physical activity, noting their environmental implications. 相似文献
|