Ciose-to-natural Plantation Of Thinning Intensity On Population And Community Restoration Of Quercus Wutaishanica Forest

In this paper, we present investigation on plots of Quercus wutaishanica forest afterthinning with different silvicultural treatments in Huanglongshan region on the Loess Plateau.Compared to the uncut treatment, managements were close-to-natural forest managementthinning13.4%(light thinning) and self-regenerating forests, thinning30.0%(heavy thinning)and planting of Pinus tabulaefomis. The vegetation changes and tree regeneration wereobserved following the first and sixth growing seasons after thinning. Soil seeds bank,seedling establishment, spatial pattern and dynamic characteristic were studied. Compared withthe uncut plots, population regeneration, woodland productivity, soil fertility and speciesdiversity were researched after thinning. The forest community stability was evaluated bycalculating subordinate function values based on fuzzy synthetic evaluation. The main resultswere as follows:(1) Close-to-natural plantation of thinning intensity on seed production of Q. wutaishanica:Seeds number of Q. wutaishanica was465～915N/plant. Seeds were higher in thinning plots(increased by9.87and17.04%in light and heavy thinning plots, respectively) than in controlplots, and there was significantly difference among thinning treatments. The developmentseeds number was control <light <heavy, and there was significantly difference amongthinning treatments. The aborted seeds were slightly higher in thinning plots than in controlplots, but there was no difference among thinning treatments. The development seeds werepositively correlated with tree height, DBH, crown area and crown volume. Stepwise linearregression statistics for development seeds(y) related to canopy cover(x1), litter depth r(x2),soil moisture (x3), pH (x4), organic matter content(x5), total nitrogen(x6) and totalphosphorus(x7), and showed that y=-4.122X1+754.882, whereas only environmental factorsignificantly related to the density of sprouts was the canopy cover.(2) Close-to-natural plantation of thinning intensity on seedling growth of Q.wutaishanica: The soil bank of Q. wutaishanica lasted about70days. The seed rain were theinitiation stage, the peak and the last stage. There existed differences in the disseminationprocess, occurrence time and composition of the seed rain among the three treatments．Thedensity of seeds rain was control <light <heavy. Which the thinning intensity increased, thedensity of Q. wutaishanica seeds was increased. The processes of seeds rain of different quality were similar among three thinning treatments. The start stage was unmature seeds,while the peak stage was mature seeds. The insect and predated seed were occurrence duringthe whole process of seeds rain. ANOVA result testing the effect of time (the initiation, thepeak and the last stage of seeds rain) and thinning treatment (control, light and heavy thinning)on characteristics of cumulative seeds, showed that the weights per hundred, germinated,insect and moldy seeds were difference among times, and no differences were found amongthinning treatments. This mean that seeds quality was better during the peak stage of seedsrain. Loss from the soil seed bank occurred though predation and removal by animal, or decayafter death, or germination, which the fist was the most important factor significantly relatedto the soil seed bank dynamics. Seeds of Q. wutaishanica were rich but seedlings were rarely.Thinning measures affect seedling settled. With the thinning intensity increased, the survivalrate of1-year-old seedlings were gradually increased, while the survival rate of2-year-oldseedlings were drop gradually.(3) Regeneration and development of stump sprouts of Q. wutaishanica: Sprouting success,number of sprouts per stump, and sprout height differed little from light and heavy thinningafter thinning1year. Stump height and diameter had influence on the number of stumpsprouts. The sprout number increased with the height of stumps,it would decrease when theheight was over20cm. The number of stump sprouts increased as the increase of stumpdiameter, and then it decreased as the stump diameter increased too large. Negativerelationship was found between height and number of stems. For6years after thinning, thesurvival of stump sprouting was97.01%. Thinning intensity had influence on sproutdevelopment. During the observation period, the height of leading sprout decreased as theincrease of thinning age. The number of dead sprout increased as the sprout numberincreasing of each stump, indicated that stump sprouts of Q. wutaishanica could develop intobig tree instead of the cut and fallen trunk.(4) Natural regeneration and growth of Q. wutaishanica saplings after plantationthinning: The number of true seedlings was more than seedling sprouts, approximately20-45%of Q. wutaishanica saplings originated from root or stem sprouts. Seedling densitieswere higher in microsites opened by thinning, while root and stem sprouts were equallycommon among different treatments. Root and stem sprouts at least initially grew faster thantrue seedlings. Whether in thinning stands, or in closing woodland, Q. wutaishanica saplingswere abundant, suggesting that they will successfully regenerate. Q. wutaishanica existedwith two breeding strategies between seedlings and seedlingsprouts among different tendingpractices.(5) Close-to-natural plantation of thinning intensity on structure characteristics and spatial distribution of Q. wutaishanica population: The age structure of the population indicated thatmost individuals were assembled in the juvenile stage, and young ones were the least.2)Population mortality rate was the highest inⅠ-Ⅲage class. With age increasing, mortalitydisplayed "high-low–high" mode, while the expectancy life of population displayed "low-high-low" mode.3) The survivorship curve of population generally matched a Deevey TypeⅢ.4) With sampling dimension increasing, the spatial distribution transformed from clumpedor random to clump distribution.5) As population became older, their distribution transformedfrom the clumped into a random distribution while their clumped intensities came down.6)Comparing with the control, the number of the juveniles after light and heavy thinningpromoted, and population structure was optimized. Therefore, the secondary Q. wutaishanicaforest reach thinning period. Under natural circumstances, the25m2–50m2at the highestclumped intensity was the optimal area for the population regeneration. The close-to-naturemanagement thinning30.0%was more suitable to the management.(6) Close-to-natural plantation of thinning intensity on ground vegetation and treeregeneration of Q. wutaishanica forest: Growth factors were different under different thinninglevels after6year of thinning. There were no significant difference in species number of tree,shrub and herb. The growth height of tree and herb hadn't significant different whereas theshrub had. The coverage of tree, shrub and herb showed significant difference. Comparedwith the first year, the cover values of single vegetation had changed after6year sincethinning. The individual numbers of the seedling in thinning plots was increased,such as, e.g.,Q. wutaishanica, P. tabulaefomis, Acer ginnala and Populus davidiana, their seedlingincreased with intensity thinning. Q. wutaishanica saplings will successfully regenerateduring the observation period. But the close-to-natural plantation thinning was the key tospeed up regeneration development. Few found natural seedlings of P. tabulaefomis inun-thinning and thinning plots proved that this species isn't able to establish spontaneously.Artificial planting P. tabulaefomis seedling after heavy thinning is an effective managementto make up for lack of seedling. The close-to-natural forest management was moreadvantageous to ground vegetation and tree regeneration of Q. wutaishanica forest. This canbe integrated into silviculture as positive forest conversion management in Huanglong forestregion on the Loess Plateau. An active treatment like thinning of stands, or planting of trees,can accelerate forest conversion with regard to species number of trees.(7) Close-to-natural plantation of thinning intensity on the community niche of Q.wutaishanica forest: Q. wutaishanica is the dominant overstory species Liaodong oak forest,which Chinese pine (Pinus tabulaefomis Carr.) and crimson-leaved maple (Acer ginnalaMaxim.) being sub-dominants.The crown density of uncut plots is very big, lead to the number plants and coverage of shrub layer were low, but the number species was abundant.Compared with unthinning samples, shrub and herb species number and coverage areincreased in thinning samples (light and heavy thinning). That was not only beneficial togrowth and expansion of shrubs and herb in the thinning measures, also can promote newspecies invasion. With the increase of thinning intensity, niche breadth of P. tabulaeformiswas increasing, and A. ginnala was decreasing. The niche breadths of shrubs and herb weredifferent among thinning intensity；the niche overlap within the same layers shown differentamong thinning intensity, that meant that the competition in the use of the environmentalresources among species is not evitable in the process of the community succession.(8) Close-to-natural plantation of thinning intensity on the community stability of Q.wutaishanica forest: Compared with the control, the forest regeneration potential in light andheavy thinning plots was promoted14.19%and20.19%respectively. Compared with theuncut plots, the arbor volumes in different thinning intensities reduced9.00%and23.80%, butbiomasses of shrub increased7.32%and12.20%, biomasses of herb increased10.53%and31.58%respectively. The woodland soil fertility and species diversity indexes were higher inthe thinning plots than the uncut plots. Therefore, the forest communality stability evaluationof Q. wutaishanica forest showed: the heavy thinning forest＞the light thinning forest＞the uncut forest. Close-to-natural plantation thinning30.0%was more suitable to managementof Q. wutaishanica secondary forest in the Loess Plateau.