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61.
着重介绍了老路加铺的方案及新老搭接的处理 ,重点对老路的弯沉控制指标、修补措施、加铺方案和新老路基路面的搭接处理做了详细的分析。 相似文献
62.
采用优质粉煤灰与高效减水剂 ,调整骨料级配等技术途径配制高性能混凝土 ,使水泥用量大幅度降低 ,从而减少水化热和收缩、徐变 ,使绿色高性能混凝土成功地应用于桥梁工程中。 相似文献
63.
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65.
通过对嘉兴市区道路绿化的调查,发现存在树种单一、层次单调等问题,对此提出相应的改进措施,以创造完整、连续的道路绿化空间. 相似文献
66.
We evaluated the protective effects of floor cover against soil erosion in three types of forest located on steep slopes
under a humid climate: 22- and 34-year-old Chamaecyparis obtusa (hinoki), 34-year-old Cryptomeria japonica (sugi), and 62-year-old Pinus densiflora (red pine) stands. We measured sediment transport rates (sediment mass passing through one meter of contour width per millimeter
of rainfall), using sediment traps, before and after removing floor cover. Raindrop splash erosion was dominant in the experimental
stands. Floor cover percentage (FCP) during the preremoval stage varied from 50% to 100% among the four stands, and sediment
transport rates ranged from 0.0079 to 1.7 g m−1 mm−1. The rates increased to 1.5–5.6 g m−1 mm−1 immediately after removing floor cover, and remained high throughout the experiment. The presence of physical cover near
the ground has a crucial effect on sediment transport on forested slopes. The protective effect ratio (the ratio of the sediment
transport rate in a control plot to that in the removal plot) in a young hinoki stand, in which the FCP decreased markedly,
was 0.3 at most, which is close to the rate for bare ground. The protective effect ratio in the red pine stand was ≤0.003.
We concluded that the protective effect of floor cover in undisturbed forests in Japan differs by over two orders of magnitude,
based on comparisons with previous studies.
Received: March 11, 2002 / Accepted: August 16, 2002
Present address: Department of Forest Site Environment, Forestry and Forest Products Research Institute, Ibaraki 305-8687 Japan Tel. +81-298-73-3211;
Fax +81-298-74-3720 e-mail: miura@affrc.go.jp
Present address: Department of Forest Site Environment, Forestry and Forest Products Research Institute, Ibaraki 305-8687 Japan Tel. +81-298-73-3211;
Fax +81-298-74-3720 e-mail: miura@affrc.go.jp
Acknowledgments This study was supported by the Research Council of the Ministry of Agriculture, Forestry, and Fisheries, of Japan. We thank
H. Ujihara, S. Ujihara, and M. Ogasawara in Otoyo, Kochi, who provided the experimental stands used in this study. We also
thank K. Hirai, S. Kuramoto, E. Kodani, and the rest of the staff at the Shikoku Research Center, Forestry and Forest Products
Research Institute, for their help in conducting the experiments.
Correspondence to:S. Miura 相似文献
67.
68.
Vegetation recovery is a key measure to improve ecosystems in the Loess Plateau in China. To understand the evolution of soil
microorganisms in forest plantations in the hilly areas of the Loess Plateau, the soil microbial biomass, microbial respiration
and physical and chemical properties of the soil of Robinia pseudoacacia plantations were studied. In this study, eight forest soils of different age classes were used to study the evolution of
soil microbial biomass, while a farmland and a native forest community of Platycladus orientalis L. were chosen as controls. By measuring soil microbial biomass, metabolic quotient, and physical and chemical properties,
it can be concluded that soil quality was improved steadily after planting. Soil microbial biomass of C, N and P (SMBC, SMBN
and SMBP) increased significantly after 10 to 15 years of afforestation and vegetation recovery. A relatively stable state
of soil microbial biomass was maintained in near-mature or mature plantations. There was an increase of soil microbial biomass
appearing at the end of the mature stage. After 50 years of afforestation and vegetation recovery, compared with those in
farmland, the soil microbial biomass of C, N and P increased by 213%, 201% and 83% respectively, but only accounting for 51%,
55% and 61% of the increase in P. orientalis forest. Microbial soil respiration was enhanced in the early stages, and then weakened in the later stage after restoration,
which was different from the change of soil organic carbon. The metabolic quotient (qCO2) was significantly higher in the soils of the P. orientalis forest than that in farmland at the early restoration stage and then decreased rapidly. After 25 years of afforestation and
vegetation recovery, qCO2 in soils of the R. pseudoacacia forest was lower than that in the farmland soil, and reached a minimum after 50 years, which was close to that of the P. orientalis forest. A significant relationship was found among soil microbial biomass, qCO2 and physical and chemical properties and restoration duration. Therefore, we conclude that it is possible to artificially
improve the ecological environment and soil quality in the hilly area of the Loess Plateau; a long time, even more than 100
years, is needed to reach the climax of the present natural forest.
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Translated from Acta Ecologica Sinica, 2007, 27(3): 909–917 [译自: 生态学报] 相似文献
69.
Reforestation is one of the most important and efficient measures of water and soil conservation. Based on field investigations
in the Shangyang Soil Conservation and Reforestation Station in Huizhou, Guangdong Province, China, we studied the variation
in vegetation development, vegetation succession processes and soil erosion. The regional vegetation consists mainly of monsoon
evergreen broad-leaved forests (MEBF). The area was deforested and became a denuded hill area with extremely high soil erosion
in the 1960s and 1970s. Then, the area was closed in order to allow recovery of the vegetation. Under natural conditions the
vegetation development and succession processes were slow during which soil erosion and strong sunshine and evaporation slowed
down the development of the vegetation. About 25 years later, the vegetation cover was still merely 35% or so. The dominant
vegetation types were heliophilous herbage and shrubs which formed a poorly developed shrub-herbage community and erosion
remained high. In contrast, reforestation with selected tree species dramatically speeded up the vegetation succession process.
About 12 years after reforestation, vegetation cover of the Acacia auriculiformis plantations in the Shangyang Station was 90% and erosion was under control. After 23 years, understory vegetation, consisting
of indigenous species, had developed in the plantations. The planted trees and naturally developing herbage, shrubs, bamboo,
local trees and liana formed a complex vegetation community in three layers. It will take 60 years for the vegetation to succeed
from bare land to a secondary growth forest under natural conditions. Reforestation may speed up the vegetation succession
process. The time may be reduced to 20 years. Reforestation is the most effective measure of vegetation restoration and erosion
control in this area.
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Translated from Acta Ecologica Sinica, 2006, 26(8): 2558–2565 [译自: 生态学报] 相似文献
70.