| Aiming at solving the overripe problem of Three North Shelterbelts and better play to the protection benefit, ecological benefits and economic benefits of farmland shelterbelt, we took several typical farmland shelterbelts in west of Hei Longjiang Province as research object. Firstly, the growth process and regularity of four different protection forests were analyzed by parsing method; Based on the growth characterization, we comparatively determined the updating age of the poplar tree belts through investigating the age of quantitative maturity, the age of initial protection maturity, the age of terminal protection maturity,, and economical maturity in the study area. At the same time, soil structure and regular soil chemical properties of Manchurian Ash (Fraxinus mandshurica), Dahurian Larch (Larix gmelini), Korean Spruce (Picea koraiensis) shelterbelts renovated from Poplar (Populus) in Western of Heilongjiang Province, were analyzed by measuring soil bulk density, soil porosity, three soil phase status and pH, organic mater, in order to provide theoretical basis for regeneration of farmland shelterbelt, and the results showed that:As a result of the fast-growth nature of Poplar, cumulative growth was higher than that of Pinus sylvestris var. mongolica, Dahurian Larch, and Korean Spruce in various growth factors. The tree high-speed stage of poplar is3a～7a, and after the13a, height growth rate of Poplar was slowing down; diameter at breast height in5a～8a was fast-growing period, after11a, growth of breast began to slow; fast growth period of poplar volume was5a～10a, and after18a it began to slow. For Dahurian Larch shelterbelts, the high-speed stage is5a～10a, after15a the tree height growth rate was slowing down; diameter at breast height in4a～10a was fast-growing period, after13a growth began to slow, fast-growing period of volume growth was5a～18a. For Pinus sylvestris var. mongolica shelterbelts, high speed period was in7a～11a, after19a the height growth rate was slowing down, DBH fast-growing period was in12a, after6a-4a growth began to slow, fast-growing period of volume growth was in10a～21a period. For Korean Spruce shelterbelts, high-speed stage was in8a-10a, after18a tree height growth rate was slowing down, DBH fast-growing period in10a～13a. after20a growth began to slow, fast growth period of volume growth was7a～22aBased on the annual and mean volume growth increment of poplar, the age of quantitative protection maturity was determined to10a; based on the annual and mean height growth increment of poplar. the age of initial protection maturity was determined to8a; through analyzing com crop photosynthetic physiological indexes in the different shelterbelt protection range of different ages of poplar.the age of terminal protection maturity was determined to20a～30a; net present value (NPV) method was used to obtain the economical maturity age of23a. Combination with the practical situation of the study area, suggest regeneration age of the poplar shelterbelts as23a～25a, updating during this period can make its protective benefit, ecological benefit and economical benefit are optimal, comprehensively.Manchurian Ash and Dahurian Larch shelterbelts had lower bulk density comparing with Spruce. Although the soil total porosity of Dahurian Larch was highest in topsoil and main root area, non-capillary porosity of Manchurian Ash and capillary porosity of Korean Spruce were significantly highest, respectively. In comprehensive evaluation, Manchurian Ash shelterbelt resulted in soil structure and nutrient environment by having reasonable three soil phase’s ratio, pH of background value and higher soil organic matter. However, soil under Dahurian Larch shelterbelt leaded to a poor chemical condition with lower pH and organic matter; Korean Spruce caused a poor physical condition with higher bulk density and lower proportion of macro pores. The results could provide practical reference for shelterbelt renovation and restoration in the local area. |
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