| Haloxylon ammodendron Bge, a woody shrub belongs to Haloxylon genus of Chenopodiaceae family is one of excellent plants for breaking wind and fixing sand dune. It is a typical psammophyte who prefers arid atmosphere and poor soil, enables strongly drought and cold, and can grow in alkaline and saline soil, and tolerate wind erosion and sand bury. It not only plays an important ecological role in west zones of China, but also is an important plant of pasture and fuel resources with high valued and called "coal in the desert". Natural Haloxylon ammodendron Bge became a vulnerable species because of large-scale damage in the past, and was listed as the third grade national protected plant in 1984. The endangered grade has been reduce after introduction, reproduction and aforestation of Haloxylon ammodendron Bge at different places since 1950' s. But since 1970's, artificial Haloxylon ammodendron Bge forest has degenerated, which results that fixed sand dune to be active, desertification degree increase, and threaten survival and development of oasis. It is a quite urgent task to restore or rebuild artificial Haloxylon ammodendron Bge forest that will promote protection of Haloxylon ammodendron Bge resources, biodiversity in desert zone, and construct ecological shelterbelt at fringe of oasis. The artificial woodland of. Haloxylon ammodendron Bge was took as a research object. On studying status, and community characteristics of degenerating Haloxylon ammodendron Bge, and main effecting ecological factors for growth and degeneration of Haloxylon ammodendron Bge, a restoration principles and aims will be put forward, and a experiment in four restoration technologies were also researched, which will carry out available exploration for theory and methods on artificial Haloxylon ammodendron Bge forest at Minqin county and around zones.1) The artificial woodland of Haloxylon ammodendron Bge with total area about 0.035 million hm2, forms a wind breaking and sand fixing shelterbelt that is 2-5 km width at fringe of Minqin oasis, and occupies 51.5% of the total area of 0.0678 million hm of artificial forest. At present, forest of Haloxylon ammodendron Bge shows a degeneration scene in large area. It may be divided into light degenerated section (around Hongyashan reservoir and Shiyang River), middle degenerated section (around Huqu and Quanshan districts) and serious degenerated section (around Baqu district). Haloxylon ammodendron Bge forest may be divided into light degenerated type (on Gobi), middle degenerated type (on move and semi-move sand dune) and serious degenerated type (on fixed sand dune and basin among sand dune).2) When Haloxylon ammodendron Bge community degenerate, photosynthetic rate and growth rate of Haloxylon ammodendron will reduced, the woodland soil moisture collectively decreased, and would upgrade after serious degenerated. It shows that coverage and biodiversity decreased. The domination of Haloxylon ammodendron increases in the community. The function of community on breaking wind, fixing sand dune take off, too. The object will not carry out, even though the community can break wind and fix sanddune.3) Distribution, reproduction and community structure of Haloxylon ammodendron Bge are effected obviously by the amount, spatial and temporal distribution, and annual variation of precipitation. The distribution of Haloxylon ammodendron Bge is without strictly disdrict, but it only presents at places where precipitation is lower than 180mm.4) When depth of groundwater table is lower than 4m, Haloxylon ammodendron Bge grows normally; from 4m to 7m, Haloxylon ammodendron Bge mildly degenerate; from 7m to 10m, Haloxylon ammodendron Bge middingly degenerate; at more than 10m, it seriously degenerate.5) There are two types of soil crust that are microbiotic crust and mechanical crust on surface of Haloxylon ammodendron Bge woodland in Minqin. The characteristic of mechanical crust with more fine grains, viscidity grains and lower organic matter is more solid and infertile, which effect strongly community of H... |
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