Research On Structure And Function Evaluation And Close-to-nature Management Of Larch Principis Rupprechtii In Mountainous Area Of Northern Hebei Province

Forest is the main part of terrestrial ecosystem, and the forest ecosystem which is located in mountainous area of northern Hebei Province is an important ecological barrier for Beijing-Tianjin-Hebei region. Four kinds of typical larch stands were selected as research object in this paper, including larch forest (sample A), larch-birch mixed forest (sample B), larch-broadleaved mixed forest (sample C) and Spruce-larch mixed forest (sample D). The characteristics of species composition, diameter structure, vertical structure, uniform angle index, neighborhood comparison and mingling index were analyzed, and the growth law of species was compared, and the ecological functions of carbon fixation and oxygen release, air purification and water conservation were assessed. Based on the analysis of nature closeness, we constructed the optimal forest type, and proposed the Close-to-nature management Techniques of typical stands to provide a theoretical basis for the sustainable development of regional forestry.(1) Tree species composition is the basic structure of stand characteristics. The total basal area was at25.0396-47.2051m2/hm2in4kinds of stands. The mean diameter and the mean height of north-china larch were17.7-18.6cm and10.8-14.3m, respectively. The basal area of Spruce-larch mixed forests was the largest in all types of stands whose diameter and height distribution were for normal distribution. Using uniform angle index, it showed that the larch-birch mixed forests were even distribution, larch-broadleaf mixed forests were reunion distribution, and Spruce-larch mixed forests were random distribution. Among these stands, the diameter neighborhood comparison and the mean mingling index were large, and the species composition was more complicated.(2) The growth law of species in different stands was basically consistent. In the growing cycle of broadleaved tree species, the growth rate showed a downward trend, and the advantage of prophase was obvious, while, the coniferous trees had a stronger competition in the late stage. In different stands, the growth increment of larch ranged sample D>C>B>A; growth curve of birch trees was staggered, and the growth increment was sample D>C>B; the growth increment of tremula was D>C.(3) The values of capacity of carbon sequestration, air purifier and water conservation were most in Spruce-larch mixed forests in different ages. The value of capacity of carbon sequestration was Spruce-larch mixed forests (18061yuan/hm2.a)> larch-birch mixed forests(13268yuan/hm2.a)> larch forests(10284yuan/hm2.a)> larch-broadleaf mixed forests(9556yuan/hm2.a); the value of capacity of air purifier was Spruce-larch mixed forests (6442yuan/hm2.a)> larch forests(4143yuan/hm2.a)> larch-birch mixed forests(3177yuan/hm2.a)=larch-broadleaf mixed forests(3177yuan/hmz.a); the value of capacity of water conservation was Spruce-larch mixed forests (1025yuan/hm2.a)> larch-birch mixed forests(864yuan/hm2.a)> larch-broadleaf mixed forests(826yuan/hm2.a)> larch forests(727yuan/hm2.a).(4)The diversity index of arbor layer of Spruce-larch mixed forests was the largest,whereas larch forests was the smallest; the diversity of shrub layer of larch-birch forests was the largest, larch forest smallest; the diversity index of grass layer of Spruce-larch mixed forests was the largest, larch-birch forests smallest. The nature closeness of the highest was Spruce-larch mixed forest, and the lowest was larch forest. We formulated the Spruce-larch mixed forest be target stand, and determined the adjustment measures and logging mode to achieve the biggest profits of target stand.(5)By tending thinning, artificial pruning and planting seedlings, Spruce-larch mixed forest was optimized. The larch forests, larch-birch forests and the larch-broadleaf forests was near-natural induced.By evaluation of4kinds of Larch principis rupprechtii, we determined spruce and larch dominated forest as the target stand, proposed the way of objective tree controlling felled tree, the Close-to-nature optimization and near-natural induction, which could provide theoretical basis and technical support for the forest management in mountainous area of northern Hebei Province.