Spatial Characteristics And Structure-Based Management Of Picea Wilsonii Forest In DaTong River Basin Of QingHai Province,China

Qinghai,located in the northwest of China,is an important sensitive climate intersection area,lack of forest resources.Picea wilsonii,has strong adaptability and shade tolerance,as one of the main tree species of Huzhu Beishan forest range in Qinghai Province and has great ecological value such as water conservation.Forest in this range has been gradually restored after decades of management.However,there are few studies of Picea wilsonii forest,which was a hindrance to the forest sustainable development.In this research,we toke the Picea wilsonii forest in this area as the research object,using angle index(W),dominance(U)and mingling(M)parameters,quantitatively analyzed the univariate distribution and bivariate distribution etc.spatial structure characteristics of dominant species in Picea Wilsonii pure and mixed forest,and put forward specific structure-based forest management suggestions according to the results.The main results are as follows:(1)The community structure of the Picea wilsonii pure forest is compeled and the spatial structure is reasonable.The diameter distribution showed an inverted "J" shape,which generally consistent with the diameter distribution of natural uneven-aged forest.The gentle slope forest distributed in clusters,and the distribution of middle slope and steep slope forest are random.The trees of different differentiation degrees are uniformly distributed,close to20%,and the stands are close to the mean state.The Picea wilsonii competition potential in middle slope stand is slightly stronger than that in flat slope and the steep slope stands.Mixing degree in pure forest is extramely low.Bivariate distribution characteristics of different slope stands are similar.In the relationship between distribution pattern and differentiation degree,the distribution frequency of trees with different size ratios increased first and then decreased with the change of angular scale,and the development of DBH was restricted by the cluster distribution.The most common combination pattern in pure Picea wilsonii forests is that at most one tree of other species distributed around randomly distributed Picea wilsonii tree.Under the same mixing grade,the size ratio changes more evenly,without obvious evident regularity,and the correlation between them is not strong.(2)The diameter distribution of Picea wilsonii species in mixed forest is an inverted "J" shape,which generally consistent with the diameter distribution of natural uneven-aged forest.The diameter structure of companion species are not reasonable,all showing declining trend populations.Populations are uniformly distributed in Picea Wilsonii-Betula platyphyll amixed forest and Picea wilsonii-Aspen mixed forest,and randomly distributed in Picea Wilsonii-Betula dahurica mixed forest.The distribution pattern of Picea wilsonii population in Picea wilsonii mixed forest is in stage of uniform distribution transition to random distribution.The competition potential of Picea wilsonii population in Picea Wilsonii-Betula platyphyll amixed forest and Picea Wilsonii-Populus davidiana mixed forest are higher than other species,but lower than other species in Wilsonii-betula dahurica mixed forest,and the distribution pattern of birch and aspen populationare clumps and in a weak position in community.Red birch population showed a random distribution pattern and with a strong competition potential.The comprehensive conditions of community structure of betula picea wilsonii are superior to those of the other two mixed forests.The distribution frequency of Picea Wilsonii population in same differentiation level shows a trend of increasing first and then decreasing with the angular scale,and the development of DBH is constrained by the mass distribution pattern.The mixing level of most random distribution of Picea Wilsonii is moderate mixing or weak mixing.Many trees are in moderate mixed state of Picea Wilsonii population with the same degree of differentiation.In companion population,there are usually2-3 other trees around randomly distributed or unevenly distributed target trees.Under the same mixing grade,there has no obvious evident regularity in the change of size ratio,and the correlation between them is weak.(3)The large and middle diameter trees are distributed in a random pattern in pure Picea Wilsonii forest,and the small diameter trees are nodular form distribution pattern,which are squeezed obviously.The distribution pattern of large and medium diameter trees is random in mixed forest of Picea wilsonii,and the distribution pattern of small diameter trees is uniform.Both large diameter and medium diameter trees are in a competitive position in the stand,while small diameter trees mixed well but were obviously squeezed.(4)The common problems of Picea wilsonii community in study area is that the proportion of large-diameter wood is too large,so manual planting or artificial forest gap should be adopted to promote plant regeneration.The distribution of gentle slope stands is slightly clumpy,and it is necessary to adjust the crowding degree with the reference of angular scale.Betula betula and aspen populations were distributed in clumps,and the distribution pattern should be optimized.