| People develop excessively in semi-arid loess hilly region for a long time, which leads to ecologicalenvironment deterioration and low vegetation cover rate. The phenomenon of soil drought and water andsoil erosion seriously appeared in that area. Afforestation work is paid attention day by day since thefounding of new China especially after1999. Caragana, whose growth situation relates to plant recovery insemi-arid region, is a typical shrub in loess area. Research on the Caragana growth process will contributeto the ecological environment construction in semi-arid region.Using hight observation data of Guyuan ecological experiment station, which locates in Shanghuangvillage He chuan township Yuanzhou area Guyuan city Ningxia Hui autonomous region, in2002,2003and2004, this research sets up Caragana growth process model in that area. The main conclusions are asfollows:1. The paper established a improved model about height growth in one year. The change condition ofbiological indicator conform to S type growth in one year. This research, based on Logistic equation whenresearching Caragana height growth, taking the rate of photosynthesis lower than that of respiratory at highdensity conditions into account when Caraganas are in the late growth period, add a growth resistancefactor to relative growth rate varied with time of Logistic model. The Logistic model increased a growthmechanism and become an explanatory model. The improved model is used to fitting growth observationdata of ripe woodland in2002,2003and young woodland in2003.2, Analysing the fitting data, the result suggest that the improved model make the relative growth rateof Caragana growth negative in the late growth period. This model which has higher goodness of fit of thenew equation than that of Logistic model, reflecting the characteristic of caragana growth in semi-aridregion, can describe the caragana growth very well in that area. Density and environment factors are on theimpact of high growth in the changes of Caragana growth during one year. The growth of ripe woodlandbelongs to that of higher density conditions, Density test is not on the impact of high growth in2002.Butwhen it comes to2003, the ripe Caragana growth whose densities are87brush per100square and71brushper100square belongs to that of higher density conditions, then, the growth whose design density is lowerthan51brush per100square belongs to that of lower density conditions. Density test is on the impact of high growth in2003.The density applicable value of the improved models locates between51brush per100square and71brush per100square. The improved model is suitable to growth process simulation ofjuvenile caragana in different seeding quantity handle. Affected by precipitation and initial moisture content,the growth volume of ripe caragana in2002is higher than that in2003and the variation of relative growthrate of ripe caragana in2002is also higher than that in2003.3, Caragana are perennial shrub so the annual variation of growth cannot be ignored. Compositing thegrowth model in two or three years is taken into account. Because test ground locates in southern mountainarea of Ningxia, when it comes to winter, the temperature is very low, which cause the terminal buds die inthe winter time. Taking the above phenomenon that the stem is dry in winter into account, the paper, basedon the observation data of sample cluster whose density are87brush per100square and71brush per100square, sets up a consecutive-year growth model. The extreme points of annual change connection functionwhich are considered as termination point of stem drying process, are solved.4, On the basis of improved model, the paper make the analysis of caragana growth interval. With adividing point at extreme point in growth stage of improved model, the paper divided growth period anddrop period. Connecting starting point and extreme coordinate within one year growth, average growthspeed of young woodland in a year can be solved. With a dividing point where instantaneous growth rate ingrowth period equals to average growth speed within one year, the paper divided growth period into thefaster growth stage and the slower growth stage. |
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