【作者】 李荣；

【导师】 张文辉；

【作者基本信息】 西北农林科技大学 ， 森林培育， 2012， 博士

【摘要】 以黄龙地区经过近自然经营，不同间伐强度：未间伐（对照）、间伐材积强度13.4%（弱度间伐）自然更新和30.0%（强度间伐）后人工补植油松幼苗的辽东栎林为研究对象，通过对间伐后第1年和第6年样地调查，为辽东栎种群的抚育经营提供了依据。主要研究结果如下：（1）通过近自然经营强度对辽东栎个体结实的影响表明，辽东栎林木个体平均种子（坚果）总数在465粒/株～915粒/株。在抚育间伐条件下，弱度和强度间伐后的林地辽东栎植株种子总数提高了9.87%和17.04%，且间伐强度显著影响种子总数。正常发育的种子数,对照＜弱度＜强度的趋势；而败育(未成熟)种子数量在间伐样地略高于对照样地。辽东栎个体生产种子数量与其高度、胸径、冠幅面积和冠幅体积均呈显著正相关，个体大的植株产生更多的种子。以植株发育种子数（y）作为因变量，分别以林分郁闭度（x1）、枯枝落叶物厚度（x2）、土壤湿度（x3）、土壤pH值（x4）、土壤有机质含量（x5）、土壤全N（x6）和土壤全P（x7）做为自变量，进行多元逐步回归分析，发现影响辽东栎植株发育种子数最显著的环境因子是林地郁闭度（y=-4.122x1+754.882）。（2）通过近自然经营强度对辽东栎成苗过程的影响表明，辽东栎种群种子雨持续时间70天，不同间伐强度下种子雨密度动态相似，大致分为起始期、高峰期和末期；不同间伐强度下，种子雨密度呈现：对照＜弱度＜强度的趋势，即随着间伐强度增加，辽东栎种子密度在增加；不同间伐强度样地间种子质量无显著差异；种子雨在起始期以不成熟种子为主，高峰期以成熟种子占优势；种子质量以种子雨高峰期得到最佳；辽东栎种子库中的种子命运主要有动物取食或者搬运、种子死亡后腐烂、发芽存活等，其中动物取食或者搬运是影响种子命运的主要因素。辽东栎种子丰富但成苗的很少，不同间伐措施影响幼苗定居；随着间伐强度增加，1年幼苗生存活率逐步增加，而2年生幼苗存活率逐步下降。（3）通过研究辽东栎伐桩萌苗的发育规律表明，不同间伐强度中，当年伐桩萌生枝数量和萌生枝高度无显著差异；萌生枝数量受伐桩高度和直径的影响；当伐桩高度较低时，萌生枝数量随伐桩高度的增加而增加，超过20cm后随之减少；伐桩萌生枝数量随着伐桩直径增加呈现先增加后减少的趋势；伐桩萌生枝数量与最长萌生枝高度呈显著线性负相关；间伐第6年，伐桩的存活率为97.01%，强度间伐区萌生枝高度显著高于弱度间伐区。从间伐当年开始，辽东栎伐桩萌生枝数量逐年下降，伐桩萌苗能够自我稀疏，存在“萌代主”现象。（4）通过近自然经营辽东栎幼苗自然更新及生长状况的研究表明，辽东栎的实生苗比萌生苗多，只有大约20-45%的幼苗（高度＜2m）起源于茎萌苗或根蘖苗，间伐样地中辽东栎实生苗密度在显著大于对照样地，而茎萌苗与根蘖苗密度在不同样地间无显著差异；辽东栎无性生殖苗（茎萌苗、根蘖苗）前期生长速度快于实生苗。辽东栎种群均能够自然更新。在不同间伐经营措施中，实生苗与萌生苗所占的比例不同，反映出辽东栎存在实生苗与萌生苗两种繁殖策略的权衡。（5）通过不同间伐强度下辽东栎种群结构特征与空间分布格局的研究表明，辽东栎种群年龄结构呈现出幼苗幼树比例最大，种群死亡率在Ⅰ-Ⅲ龄级之间最高；辽东栎种群的存活曲线接近于Deevey Ⅲ型；种群格局随取样尺度增加，由聚集分布和随机分布转向聚集分布；随着种群年龄增加，分布格局由聚集型向随机型过渡；间伐措施促使辽东栎幼苗幼树和小树数量增加，促进种群结构优化。辽东栎种群聚集强度在25m2–50m2尺度最大，是其种群更新的最适面积。（6）通过近自然经营强度对辽东栎林植物组成及林木更新的影响表明，不同间伐强度影响辽东栎林的乔、灌、草植物组成、盖度和高度；间伐第6年，随着间伐强度的增加林下乔木幼苗幼树数量增加，尤其是建群树种辽东栎和油松，伴生树种茶条槭和山杨。辽东栎更新没有困难，但间伐措施能显著提高了其幼苗幼树的密度。油松天然更新幼苗幼树数量匮乏且间伐措施不能显著提高幼苗幼树密度，人工补植油松成为促进更新的有效手段。（7）通过近自然经营强度对辽东栎林优势种群生态位的影响表明，辽东栎林中占显著优势的乔木为辽东栎，其次为油松和茶条槭，未间伐样地郁闭度很大，导致灌木层植物数量低，盖度很小，但物种种类丰富。与未间伐样地相比，间伐样地（弱度和强度）灌木和草本物种数量与盖度均有所增加，间伐措施不仅有利于林下灌木和草本的生长于扩张，还能促进新物种的入侵。随间伐强度的增加，油松的生态位宽度呈递增趋势，而白桦呈递减趋势。间伐强度不同，各优势灌木和草本种群生态位宽度也有所差异，且同层之间的生态位重叠也有所差异，这些都表明在不同间伐强度下辽东栎种群间对环境资源的利用性竞争不可避免。（8）通过近自然经营强度对辽东栎林群落稳定性的影响表明，与对照相比，弱度和强度间伐样地的更新潜力分别提高了14.19%和20.19%；虽然弱度和强度间伐立木蓄积量因间伐而导致比对照分别减少了9.00%和23.80%，但灌木生物量分别增加7.32%和12.20%，草本生物量分别增加10.53%和31.58%。此外，土壤养分和物种多样性指数在间伐（弱度和强度间伐）样地均高于对照（未间伐）样地。应用模糊数学中隶属函数的方法对辽东栎林群落稳定性进行评价，表现为：强度间伐＞弱度间伐＞未间伐。近自然经营间伐强度30.0%更适合黄土高原地区辽东栎次生林的抚育管理。更多还原

【Abstract】 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.更多还原