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1、附录Reclamation of forest soils with excavator tillage and organic amendments Abstract In early 1994, a research project was initiated to evaluate the success of several techniques aimed at restoring productivity to degraded soils on landings near Vama Vama Creek, 44 km east of Prince George in Centra
2、l British Columbia. Soils were developed from morainal parent materials, the usual surface soil texture was silt loam. Two organic amendments were used in this study, including freshly prepared wood chips and old sawdust. An excavator equipped with a site preparation rake was used to till the soils
3、to a depth of 0.50 m. Organic amendments were subsequently added to the plots, and either left as a mulch or incorporated into the surface 0.20 m of the soil. Nitrogen was applied to all plots at a rate of 225 kg N ha-1, which represents about one-third of the 500700 kg ha-1 that was estimated to be
4、 required to compensate for N immobilization during decomposition of the woody residues. Survival was good for all treatments, but after 3 years, trees were growing best in areas that were treated with tillage alone. Trees growing on areas where old sawdust was used as an amendment had more volume t
5、han trees growing in areas where wood chips had been used. Control plots with no treatment had intermediate growth. Soil temperature and chemical properties were evaluated for their effect on growth.#2000 Elsevier Science B.V. All rights reserved.Keywords: Forest soil rehabilitation; British Columbi
6、a; Soil disturbance; Soil conservation; Soil productivity; Landing and road rehabilitation 1. Introduction Soils on forest landings in central British Columbia are frequently characterized by compaction and nutrient depletion (Carr, 1988a). Degraded soils on landings and other areas where soils have
7、 been disturbed by forest operations often support only meager growth of planted conifers (Arnott et al., 1988). In many cases, soil conditions are so degraded that planting is not attempted on landings. Restoring soil productivity on degraded soils requires that growth-limiting conditions be allevi
8、ated (Bulmer, 1998). Tillage is frequently employed to decompact soils and improve soil productivity(Andrus and Froehlich, 1983). On coarse-textured soils, tillage alone may provide significant benefits for growth of conifers such as lodgepole pine, although the long-term consequences of soil nutrie
9、nt depletion may be of concern. On fine-textured soils,tillage results have been inconsistent (Carr, 1988b;McNabb, 1994), partly because there is a narrow rangeof moisture content where effective tillage can be carried out, but also because stable aggregates are required to prevent puddling and poor
10、 physical conditions from reappearing shortly after tillage. Stable soil aggregates form when soil mineral grains establish an intimate association with soil organic matter(Tisdall and Oades, 1982). Several approaches could be employed to re-establish stable soil structure after tillage of fine-text
11、ured soils. A cover crop of deep rooted grasses and legumes could be established to provide organic matter and enhance biological activity in the root zone,thereby encouraging the development of stable soil aggregates. Another approach that has been proposed involves the incorporation of organic ame
12、ndments into the surface soil layer to bring organic and mineral soil materials in contact with each other, and possibly encourage the formation of stable aggregates. This project was developed in order to gain more information about methods for restoring productivity to compact and nutrient-poor so
13、ils. We evaluated the effect of several combinations of tillage and the addition of organic amendments on soil properties and the establishment and early growth of lodgepole Pine.2. Materials and methods2.1. Study sitesThe study was carried out on three forest landings 44 km east of Prince George, i
14、n the SBSwk1 biogeoclimatic subzone. Soils were developed from morainal parent materials. The usual surface soil texture was silt loam, but in at least one location, a clay-rich B horizon was encountered. Coarse fragment content varied between 15 and 40%. The landings were located on level or gently
15、 sloping areas. Prior to treatment, there was little vegetation growth on the Landings.2.2. Experimental design Nine treatments were applied to 5 m6 m plots, as described in Table 1. Two control plots were established on each landing. The two organic amendments used were wood chips produced as part
16、of treatments to reduce re hazard on the adjacent cutblock, and well-rotted sawdust from an old sawmill site. These materials are typical of soil amendments that may be available at remote rehabilitation sites. The chips had typical particle size of 0.1 m 0.05 m 0.005 m,while the sawdust particles had all dimensions smaller than 0.003 m. 2.3. Treatments Treatments were carried out in the summer of 1994 using an excavator equipped with a f
