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D. Craw C. G. Rufaut S. Hammit S. G. Clearwater C. M. Smith 《Environmental Geology》2007,51(8):1389-1400
Slopes of an abandoned waste rock at Wangaloa coal mine, south-east New Zealand, have naturally developed variable vegetation
cover over the last 40–60 years. Three distinct areas of revegetation can clearly be identified: dense cover, patchy cover,
and largely unvegetated, and the differences in revegetation success are directly related to the physical properties of different
rock types making up the waste rock substrate. The colonizing plants have become established in largely unweathered rock with
essentially no soil development. Quartz gravel and siltstone waste rock are the two principal rock types forming substrates
for revegetation. The quartz gravel has clasts up to 3 cm, and was derived from the coal-bearing sequence. Siltstone was largely
derived from a Quaternary loess cap on the coal mine area. These two substrates have similar mineral contents, and this mineral
material provides the low level of available nutrients. However, there is little difference in nutrient status or trace element
load of the different substrates, and differences in cohesion, moisture content, and proportion of quartz pebbles control
revegetation success. Finer grained matrix has been flushed from quartz gravel waste rock by rain water, leaving a dry surface
armour layer of quartz pebbles. This surface layer inhibits plant establishment, so quartz gravel waste rock remains largely
unvegetated. Erosion creates deep rills, and steep surfaces creep downslope. In contrast, full vegetation cover was established
on the siltstone waste rock that was cohesive and did not erode. Patchy revegetation was localized by siltstone in mixed quartz
gravel and siltstone substrate. Invertebrate diversity and distribution were closely linked to the spatial patterns of revegetation.
The rate of revegetation and ecosystem recovery was primarily dependent on the proportion of siltstone waste rock in the last
dumped truck load. A quartz pebble content <15% is optimal for plant establishment. 相似文献
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Water resources availability is one of the main concerns for policy makers around the world in present and future management plans. In the Mediterranean basin, this concern is increased given the extreme variability in climate and the intrinsic aridity conditions. Water resources in the Mediterranean region depend mainly on surface and subsurface supply from mountain areas. Because evapotranspiration comprises a substantial portion of the water budget, recent land cover changes due to cropland abandonment may change transpiration (TRANS) and water supply. Therefore, land management plans must account for these potential hydrologic changes to guarantee water availability in the upcoming decades. Short-term changes to water yield have been shown to follow afforestation or natural revegetation, the main management strategies in abandoned cropland areas. Studies comparing long-term trends of these management practices, however, are scarce due to the lack of long-term hydrological data. In this study, we use the regional hydro-ecological simulation system (RHESSys), to analyse long-term changes and annual and seasonal trends in streamflow (STR) and transpiration following management of abandoned cropland areas. Annual mean values show significant differences between the three management scenarios for both streamflow and transpiration, while differences between climate scenarios are not significant. The Mann Kendall trend analysis shows significant changes to water yield compared to the situation before management. Depending on the total afforested area, afforestation could significantly decrease annual streamflow between 2.3%·decade−1 and 5.9%·decade−1 and increase annual transpiration between 1.1%·decade−1 and 3.5%·decade−1. These trends are attributed to changes during the first 30 years after management, while during the fourth and fifth decade, changes to water yield tend to stabilize or decrease. These results are substantial to optimize land management plans, ensuring sustainable hydrological and ecological ecosystem services. 相似文献
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Several studies in arid ecosystems have demonstrated that seedling establishment and survival were greater underneath the canopies of shrubs than in the open spaces between shrubs. These results led to the formulation of the hypothesis that seedling recruitment and survival were dependent on the shelter provided by shrub species (nurse-plant hypothesis). Seedling emergence and survival beneath and between the canopies of selected perennial shrub species were investigated at five localities in the Strandveld Succulent Karoo, each dominated by a different shrub species. Seedling emergence and survival were also examined at three localities dominated by annual species. In general, species richness and seedling densities were significantly higher in open areas than underneath shrubs, while seedling survival percentages did not differ significantly between microsites. Therefore, no evidence could be found to support the hypothesis that seedling recruitment and survival were facilitated by the presence of shrub species. Although most species will be able to establish in the absence of shrubs, the presence of woody species may have other advantages when restoring vegetation in mined areas. 相似文献
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In the territory of Altomonte, a village located in Calabria, in the Southern part of Italy, a new thermoelectrical station
is under construction. This work involved major earthworks which regarded new excavated slopes. In order to protect soil from
erosion due to rainfall and runoff and also in order to prevent superficial soil instability, it was decided to plant four
different species of perennial “gramineae” plants (Eragrass, Elygrass, Pangrass and Vetiver) characterised by deep roots.
Works began in November 2002 and ended in May 2003, a period marked by very different climate and meteorological conditions,
varying from exceptionally rainy and cold winter to warm and dry spring months. The paper describes the different stages of
the project and the monitoring programme for the following months. The extension of the work and the use of four different
kinds of vegetation made periodic inspections of the entire site appropriate. Two in situ investigations, respectively performed
in August 2003 and in November 2003, are outlined. The aim of these surveys was to confirm the success of the work by verifying
the growth of the plants and roots. The principal monitored parameters were the percentage of sprouted plants, the height
of the foliage and the depth of roots. The investigations showed good results, keeping in mind the very difficult climatic
conditions and the extreme poor fertility of the topsoil laid down upon the clay layer: in particular, high survival rate
were measured over the entire area of the works and the root systems have developed sufficiently to grow through the upper
topsoil layer (0.2–0.3 m) into the underlying clay layer. In March 2004, a sampling programme was undertaken on the same site.
Direct shear tests were carried out in the laboratory in order to evaluate the increase in shear strength of the rooted soil
mass. The research involved the recovery of three undisturbed samples of soil with roots for each of the four types of “gramineae”
plants and three undisturbed samples constituted only of soil, from the surface to a depth of 1.0 m. The tests were performed
in a large direct shear apparatus on 200 mm diameter samples. The test results allowed to evaluate the roots’ contribution
of the different gramineous species and to underline the direct correlation between the increase in soil shear strength and
the root tensile strengths. In particular, an increase in cohesion ranging between 2 kPa and 15 kPa was recorded, according
to the different species: the maximum values of increase in shear strength were reached by Vetiver roots, which are also characterised
by the highest tensile strength. 相似文献
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露天开采在一定程度上会造成生态环境破坏。对于在生产、规模较大的露天采场,不能采用削坡回填、覆土种植等简单的传统方法恢复矿山生态环境。文章根据北京首云铁矿沙厂矿区露天采场边坡特点,结合已有科研成果技术,采用多项工程和生物措施相结合,实现生态修复。 相似文献
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Agricultural land abandonment is currently widely spread in Mediterranean countries and a further increase is expected. Previous research has shown that abandoned fields in semi‐arid areas are more vulnerable to gully erosion. The absence of ploughing and slow vegetation recovery cause the formation of soil crusts with low infiltration rates, resulting in increased runoff and gully erosion risk. The objective of our study was to assess the extent and causes of erosion and terrace failure on abandoned fields and to discuss options for mitigation. The study was carried out in the Carcavo basin, a semi‐arid catchment in southeast Spain. At catchment scale all abandoned fields were surveyed and characteristics of each field were described. Additionally we surveyed abandoned and cultivated terraces and used statistical analyses to determine the factors that induce terrace failure. At field scale we constructed a detailed digital elevation model (DEM) for an abandoned terrace field in order to calculate sediment losses since time of abandonment. The results revealed that more than half the abandoned fields had moderate to severe erosion and the statistical analysis showed that these fields had significantly steeper slopes, were terraced and had cereals as previous land use. Factors that increase the risk of terrace failure were land abandonment, steeper terrace slope, loam texture, valley‐bottom position and shrubs on the terrace wall. The reconstructed erosion rate (87 ton ha?1 year?1) confirmed the importance of gully erosion on these abandoned terrace fields. Potential soil and water conservation practices to mitigate soil erosion after abandonment are: (1) maintenance of terrace walls, as a result more water is retained, which increases vegetation cover and consequently decreases erosion. (2) Revegetation with indigenous grass species on spots with concentrated flow, especially near terrace walls. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献