Density Regulation And Control Model Investigation Based On Moisture Production Function Of Western Shanxi Province Forest Plantation

Moisture has become the key limiting factor of cultivating forest plantation in arid and semi-arid regions. All of benefits of forest plantation can be fully realized if people abide water resource environment capacity principle according to forest land water control standing forest density and structure. The author thinks it is necessary to deeply research density adjust and control technology of moisture factor such as moisture production function to make up the deficiency of traditional density adjust and control technology, which will be good for remitting more and more severe ecological problems such as deterioration of soil fertility of forest plantation, drying of woodland and decline of groundwater level.This research analyzes wood and meteorological data, estimates climate productivity and shows the mechanism of meteorological factor's effect on annual-ring according to investigation plot with forest plantation of Robinia pseudoacacia Linn and Pinus tabulaeformis Carr as research subject in Fangshan County and Ji County of Shanxi Province. Forest plantation moisture production function is established based on comprehensively analyzing growth of standing forest in different structures, water consumption and density effect rule, aiming at supplying basis for forest plantation operation management, intermediate cutting, density adjust and control and carbon cycle research in arid and semi-arid regions. Its main conclusion is:1 The growth of forest plantation in research region is affected by many factors such as density, slope and slope position. The growth of standing forest with the same density and slope is related with slope position; the growth of standing forest with the same density and slope position is related with slope; the effect of density on standing forest growth is different due to different slope, slope position and density. Density will affect the growth of standing forest and shall be quantized according to slope and slope position. It has guidance meaning for intensive operation of forest plantation. Single-tree growth mode is established with forest age and density.2 Monthly precipitation and monthly moisture index have lag effect on width of annual-rings. Annual-ring width index model is established. Monthly moisture index takes better effect on annual-ring in terms of meteorological factor, compared with precipitation and temperature. The climate productivity in Fangshan County and Ji County has reached 8.688 t·hm-2·a-1,9.314 t·hm-2·a-1,respectively. The actually-measured supreme productivity in such two counties has taken 31.6% and 59.8% of climate productivity, respectively.3 Under the condition of precipitation, the water-consuming quantity can't reach the water-requiring quantity. The sorting of water-consuming quantity in growth reasons according to the descending order is:July, June, Aug, May, Sept., Oct.. The water-consuming quantity of forest plantation increases with the increase of forest age. The water-consuming quantity will exceed the precipitation when the forest age reaches certain standard. The forest age is:15a Robinia pseudoacacia Linn. in Fangshan County; 5a Robinia pseudoacacia Linn. in Ji County and 23a Pinus tabulaeformis Carr. The water-consuming model of forest plantation is established with forest age and density.4 The moisture production function of forest plantation is initially defined. The moisture production function of forest plantation is established to make up relevant research vacancy with standing forest annual water-consuming quantity as independent variable, standing forest biomass, accumulation quantity and annual increment as dependent variable, which supplies theory basis to rational moisture utilization and density adjust and control of forest plantation.5 Forest plantation density effect model is established. The density effect becomes more and more obvious with the increase of forest age, breast diameter in growth progress and negative correlation coefficient of density increases. When the forest age reaches certain standard, the correlation coefficient growth rate becomes small, the forest age is:13a Robinia pseudoacacia Linn of north-facing slope; 10a semi-north-facing slope;8a Robinia pseudoacacia Linn of semi-north-facing slope in Ji County; 13a Pinus tabulaeformis Carr of semi-north-facing slope and south-facing slope in Fangshan County. Different slopes give different responses for density. The correlation coefficient of north-facing slope Robinia pseudoacacia Linn in Fangshan County is smaller than that of semi-north-facing slope; the correlation coefficient of south-facing slope of Pinus tabulaeformis Carr in Fangshan County is smaller than that of semi-north-facing slope.6 Most of the diameter distribution peak of forest plantation in research region is in the left, the current density tends to be thinning commonly. Thinning has obvious effect on standing forest renewal and plant diversity. Diversity index of thinning forest is higher than that of non-thinning forest. Thickness of plants under the forest and thinning forest density are in obvious negative correlation with Simpson's diversity index and Shannon diversity index and are in obvious positive correlation with ecological dominance. The renewal density and evenness index of thinning forest reduces with the increase of density of thinning forest.7 The density adjust and control model is established with single-tree and standing forest growth as dependent variable as well as forest age, density and standing forest water-consuming quantity as independent variable. It can supply basis for forest plantation density management.