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461.
N. A. Kuz'mina 《Russian Journal of Ecology》2004,35(5):303-307
Taxonometric parameters and morphological characters of cones and seeds were studied in larch trees growing in uneven-aged larch forests of the green-moss and herbaceous types. Significant differences in trunk volume and the number of cones in the crown was revealed. Differences in the parameters of cones and the quality of seeds proved to be insignificant. Correlations between the taxonometric parameters of trees and the morphological characters of cones and seeds were analyzed. 相似文献
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通过添加磁种和混凝剂,用高梯度磁分离方法去除污水中正磷酸盐污染物,并对工艺参数进行了探讨. 相似文献
465.
Ross C 《Environmental monitoring and assessment》2004,99(1-3):267-274
Loss of vegetation production in arid lands has been difficult to remediate and has signifi- cant economic impacts on human
populations. Restoration efforts based on non-local materials and large-scale mechanization have not been capable of efficiently
reversing the trend of environmental degradation. The use of traditional knowledge and simplified methods of seed harvesting,
storing, marketing and soil preparation have proven that regeneration of native species and efficient land reclamation is
possible in areas that have traditionally been considered degraded beyond redemption. This paper describes a method of land
reclamation that combines tradition and simple mechanics that can be applied in all arid areas that face desertification.
Because the work builds on cultural practices long used in non-industrialized societies, it is particularly adapted to rural
areas. The methods described have the potential to open new low-tech economic opportunities to all segments of local non-urban
populations while combating desertification and creating a more ecologically sound environment. 相似文献
466.
Grazing effects on sustainable semiarid rangeiands in Patagonia: The state and dynamics of the soil seed bank 总被引:4,自引:0,他引:4
Mónica B. Bertiller 《Environmental management》1996,20(1):123-132
The composition of the germinable seed bank was studied in four vegetation states of the Festuca pallescens grasslands in semiarid Patagonia during four years. The aim of this study was to test whether above-ground vegetation states
resulting from grazing exclusion or different combinations of grazing and topography are reflected in different states of
the germinable seed bank. The size of the total and dicot germinable seed bank was positively related to the total cover in
each state. Dicots dominated all germinable seed bank states. Carex patagonica increased its cover as well as its germinable seed bank under grazing disturbance. Grazing did not reduce the germinable seed
bank of perennial grasses in uplands where the grazing pressure is lower as compared with slopes. In slopes the germinable
seed bank of perennial grasses was significantly reduced by grazing. A reduction of the length of the grazing period in late
spring increases the germinable seed bank of perennial grasses both in upland and slope. These results are interpreted in
the frame of a model of management techniques where grazing exclusion during late spring and late summer increases the seed
bank of the perennial grasses and promotes their establishment in uplands. The artificial addition of seeds of perennial grasses
and the manipulation of the soil surface in order to increase "safe sites" appear as management alternatives that deserve
further evaluation to improve plant reestablishment in slopes. 相似文献
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Craig J. Allan Christopher J. Estes 《Journal of the American Water Resources Association》2005,41(1):123-133
ABSTRACT: Naturally formed plunge pools (scour holes) are a common morphologic feature in many urban stream systems where the transition between a pipe and a natural channel occurs. Plunge pools serve as significant stream energy dissipaters, increasing flow resistance and enhancing stream channel stability. Such features may also improve habitat diversity and serve as refugia for stream biota during low flow periods. The morphologic characteristics of several naturally formed plunge pools associated with road crossing culvert outlets in the metropolitan Charlotte, North Carolina, area are presented. Plunge pool dimensions surveyed include maximum depth, length, and width, and longitudinal and side slopes as well as bed material. Culvert outlet dimensions and hydraulic characteristics of the scouring jet for each study site are also reported. Design equations developed from flume studies generally failed to predict the naturally formed plunge pool dimensions. Pool volume was significantly correlated with drainage area, with pool depth being the least sensitive dimension to changes in the magnitude of the scouring flow. The excavation costs for designed plunge pools compare favorably to initial construction costs of traditional culvert outlet riprap aprons. 相似文献
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东营污水处理厂采用污水处理与利用相结合的生态塘处理工艺,主要由高效厌氧塘、曝气塘、曝气养鱼塘、养鱼塘、藕塘、芦苇塘等组成。经过应用分析以及10个月的数据统计可以看出:在东营市这样土地资源丰富的地区采用生态塘工艺处理城市污水,具有基建费用低、运行费用省、维护管理方便、处理效果比较稳定的优点。 相似文献