| Dealing with and mitigating global climate change, the forest has been paid more and more attention. Because the ecological property, the ecosystem services of China's ecological forest are closely related to the quality of people's life. And ecological forest plays a pivotal role in the following aspects such as air purification, carbon fixation and oxygen release, et al. But, for a long time, extensive management of ecological forest and "one size fits all" management mode, has limited ecological forest ecosystem services. Therefore, this paper, based on3S (GPS/RS/GIS), used mathematical statistical method such as variance analysis and multiple comparisons analysis to divide forest type according to tree species (group), age group and niche; analyzed the optimal stand density of forest type, technology and proposed the restrictive utilization (thinning/replanting) of ecological forest through landscape adjustment and stand adjustment, aimed at enhancing the ecosystem services, optimizing the species configuration, improving stand structure and harvesting a certain amount of timber while improving stand quality. The main conclusions are as follows:(1) In this paper, the ecological niche model MAXENT, combined climatic factors, topographic factors, soil nutrient factors, was used to predict the potential distribution of tree species (group) niches and the division of the niches suitability. The results showed that:the prediction accuracy of potential distribution of C. lanceolata, P. massoniana, broadleaved forest, mixed wood was85.0%,85.1%,80.5%,81.1%, respectively. The descending order of suitable niche area:P. massoniana> broadleaved forest> mixed wood> C. lanceolata, indicating that P. massoniana's adaptability is strongest and its niche width is widest, following by broadleaved forest and mixed wood. C. lanceolata has weakest adaptability and its niche is narrowest. Forest type was classified as16types, according to tree species (group), age group and niche.(2) This paper used variance analysis and multiple comparisons to analyze the impact of stand density on stand growth, understory vegetation and soil nutrients. The results showed that:①In the aspect of stand growth, stand density had significant effect on DBH (P<0.01), though had no significant effect on tree height, stand volume (P>0.05);②In the aspect of understory vegetation, stand density have significant effect on vegetation types, shrub height (P<0.01), and on vegetation coverage (P<0.05);③In the aspect of soil nutrients, stand density have a significant effect on soil organic matter, total nitrogen, total phosphorus, total potassium content (P<0.05), though had no significant effect on pH (P>0.05).(3) This paper, based on3S technology, used C-fix model to estimate vegetation net primary productivity(NPP); and used the revised Universal Soil Loss Equation(USLE) to estimate soil erosion modulus; and made spatial interpolation of the sampling points of soil nutrient by geostatistical Kriging method and radial basis function (RBF) method, which as the basic data for estimating the ecological forest ecosystem services value, according to 《The Criterions of Forest Ecosystem Services Assessment》 and ((The Assessment of China's Forest Ecosystem Services》, from the aspects of water conservation, carbon sequestration and oxygen release, soil conservation and air purification. The results showed that:The mean value of ecological forest NPP in Shunchang (g C m-2a-1) is708.43, sorted by tree species (group):broadleaved forest (764.08)> mixed wood (590.05)> C. lanceolata (518.23)> P. massoniana (474.05); sorted by age group:mature (744.73)> young (683.76); Sort by niche:suitable (711.84)> ordinary (703.22); sorted by ecological position:1st class protection (736.00)>2nd class protection (726.31)>3rd class protection (563.74).The mean value of soil erosion modulus(t-hm-2·a-1) of ecological forest in Shunchang is12.43, sorted by tree species (group):mixed wood (10.45)<broadleaved forest (10.96)<P. massoniana (12.59)<C. lanceolata (12.69); sorted by age group:mature (11.42)<young (12.44); Sort by niche: suitable (11.71)<ordinary (13.00); sorted by ecological position:1st class protection (12.11)<2nd class protection (12.64)<3rd class protection (13.86).The RMS (root mean square error) of spatial interpolation of soil nutrient is:organic matter16.42, total nitrogen0.61, total phosphorus0.16, total potassium2.68. According to soil nutrient content grading standards of2nd nationwide general soil survey, the grade of soil organic matter content mainly is rich and very rich (15～81g·kg1), the grade of total nitrogen content mainly is medium and rich (0.09～0.29g·kg-1), the grade of total phosphorus content mainly is low and middle (0.05～0.15g·kg-1), the grade of total potassium mainly is middle and low (14～24g·kg-1). The mean value of ecological forest ecosystem services in Shunchang (yuan·hm-2·a-1) is37836.4, sorted by tree species (group):mixed wood(40185.5)> broadleaved forest (39173.4)> P. massoniana (30256.2)> C. lanceolata (25428.9); sorted by age group:mature (33781.4)> young (33655.9); sorted by niche:suitable (40251.0)> ordinary (40024.1); sorted by ecological position:1st class protection (38689.5)>2nd class protection (38251.6)>3rd class protection (32509.2).Grey relational analysis showed that:net primary productivity, solar radiation and soil erosion modulus has a stronger correlation with the ecosystem services value, which are the main influence indices of ecosystem services value, while soil organic matter and total phosphorus content has relatively small impact on ecosystem services value of forest types.(4) According to (2) and (3) conclusions, the stand density and species configuration are closely related to ecosystem services value in ecological forest. Results showed that:There is a trend that ecosystem services value increases with the stand density increasing and then decreases in each forest type. Therefore, this paper used quadratic polynomial equation to fit, and its first order derivation is optimal stand density of forest type. Based on the principle of "increasing the proportion of broadleaved forest, reducing patch fragmentation and enhancing landscape heterogeneity", this paper simulated the adjustment of landscape pattern and the optimization of species configuration of ecological forest by computer. The results showed that:The optimal stand density, sorted by age groups:young> mature; sorted by niche:ordinary> suitable; sorted by tree species (group)(strain·hm-2):C. lanceolata (1395～2315)> P. massoniana (1525～2210)> mixed wood (1190～2007)> broadleaved forest (1455～2105).After optimimal adjustment of landscape pattern, the area proportion of C. lanceolata, P. massoniana reduced, while broadleaved forest, mixed wood increased (PLAND), the degree of patch fragmentation was significantly reduced (PD, FN), a slight increase of landscape heterogeneity (FDI, LSI), the connectivity and reunion between the patches were significantly enhanced (CONTAG), indicating the landscape pattern of ecological forest has significant improved after optimal adjustment and ecosystem services have been strengthened.(5) According to (4) conclusion, the stand density of patch is higher than the corresponding forest types'optimal stand density will need thinning, if less than need replanting, if similar is required to maintain. This paper, taking10plots as example, selected competition index, mingling index, aggregation index as the basis of stand structural adjustment (selection of logging tree or replanting area). This paper selected uniform angular index to compare stand structure changes before and after optimal adjustment. Based on forest road construction cost model, this paper analyzed the skidding routes; according to the principle of matching tree species with site, some recommendations about the choice of replanting trees are given. The results showed that:after thinning or replanting the uniform angular distribution shifted to left i.e. trees distribution tend to be uniform after optimal adjustment. |
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