【作者】 董伯骞；

【导师】 马履一；

【作者基本信息】 北京林业大学 ， 森林培育， 2014， 博士

【摘要】 林隙对于促进森林天然更新具有重要作用。间伐对林隙特征的影响,以及天然更新特征对林隙和皆伐年限响应的研究,对于揭示采伐干扰对森林更新的作用机制,从而优化经营措施,实现人工纯林的近自然经营具有重要现实意义。本文以河北省平泉县40年生、50年生油松人工纯林,皆伐后2年、5年和8年的油松人工纯林皆伐迹地为研究对象,在2011-2013年标准地和样线调查的基础上,应用点格局和地统计学等分析方法,对间伐对林隙特征的影响、林隙和皆伐年限对更新数量特征、年龄特征和分布格局的影响,以及林隙、皆伐年限与枯落物、草本生物量的关系进行了研究。研究结果表明：(1)40和50年生林分实施间伐后,林隙的线密度无变化,CG(林冠空隙)和EG(扩展林隙)开敞度的分布范围扩大,林隙更接近圆形,平均边界木数量增加10.0%和3.0%。实施间伐后40年生林分内CG和EG平均面积增加10.19%和19.84%,CG和EG面积比例增加35.24%和24.29%；50年生林分内CG和EG平均面积增加85.51%和50.23%,CG和EG面积比例增加65.59%和22.95%。(2)40年生林分内,更新树种只有油松,50年生林分内和皆伐迹地内油松数量比例均在90%以上。在40年和50年生林冠下更新密度从4.90/m2下降到2.03/m2；平均高度和基径从26.04cm和4.33mm增加到29.79cm和4.98mm,平均年龄从5.47下降到4.94。皆伐后随时间延长更新密度递减,从2.10/m2下降到0.72/m2；平均高度、基径和年龄递增,从82.03cm、21.71mm和5.85增加到159.23cm、37.52mm和7.06。各样地内高度和基径分布都为单峰型。在40和50年生林分内,林隙提高了更新密度,且更新密度分别与林隙面积正相关和负相关；小林隙内适合幼苗生长,大林隙内适合幼树生长。林隙对更新个体的高度、基径和年龄影响有限。(3)40和50年生林分内和皆伐迹地内油松的年龄结构都呈单峰型。40年生、50年生和皆伐迹地内更新群落分别主要由3-7年生、2-7年生和4-8年生个体组成。油松种群年龄结构失调,3年生以下的幼苗数量严重不足,平均寿命短,一般第8年时出现死亡高峰。存活曲线多接近Deevey Ⅱ型。(4)40和50年生林分内,林冠下更新种群都为聚集分布,皆伐后更新种群都为小尺度上聚集分布,大尺度上随机分布；油松幼苗和幼树、冠层木与更新层始终空间不相关。在40年生林分内,林隙内随林隙面积增加,更新群落由随机分布变为在小尺度上聚集分布,大尺度上随机分布；林隙降低了聚集强度。在50年生林分内,林隙内都为随机分布,随林隙面积增加聚集强度峰值对应的尺度变大。(5)40年生林分内,在10-15m2林隙内枯落物密度比林冠下提高21.28%,其余林隙内比林冠下减少33.02%-35.42%。枯落物厚度和有效拦蓄率在15m2-20m2林隙内比林冠下分别降低21.12%和16.60%,其余林隙内与林冠下差异不大。草本生物量密度在林隙内与林冠下基本一致。在50年生林分内,林隙内枯落物密度比林冠下提高16.95%-65.61%。林隙对枯落物厚度影响不显著。林隙内枯落物有效拦蓄率较林冠下下降15.73%-27.91%。林隙内草本生物量密度比林冠下提高18.18%-32.36%。40和50年生林分内,枯落物密度、厚度和草本生物量密度对更新密度影响很小。皆伐后2年到8年,枯落物的密度和厚度增加29.57%和51.64%；有效拦蓄率和草本生物量密度下降34.71%和19.61%；趋势有利于幼苗定居与生长。林隙和皆伐年限影响了枯落物特征和草本生物量密度的空间异质性。(6)实施主伐后该林地未来将形成油松复层异龄林,林分垂直结构和年龄结构的异质性增强,但仍然存在树种单一的问题。因此在缺乏其他树种种源的现状下,应考虑通过人工引进其他树种,增加树种多样性逐步营建复层异龄混交林。有必要在不同林龄的人工油松林内,制造面积更大的林隙或皆伐带,探索伐前更新的最适生境和最有效的人工干扰措施。更多还原

【Abstract】 Forest gaps play an important role in promoting the natural recruitment. Research of effects of thinning on gap characteristics and response of natural recruitment to gap characteristics and clear cutting fixed number of year have important practical significance in revealing mechanism of cutting disturbance on forest recruitment so as to optimize the management measures and realize close to nature management of artificial pure forest. Taking40and50years old pinus tabulaeformis plantation and clearing areas of pinus tabulaeformis plantation2,5and8years after clear cutting were taken as research objects in Pingquan County of Hebei province. On the basis of sample plot and line transect investigation in2011to2013, used analysis method of point pattern and geostatistics, the effects of thinning on gap characteristics as well as effect of gap and clear cutting fixed number of year on recruitment quantitative and age characteristics and distribution pattern, the relationship between gaps as well as clear cutting fixed number of year and litter as well as herbaceous biomass were studied. The results are as follows:(1) In40and50years stand, after thinning there were no change on gaps linear density, the distribution range of opening degree of CG (canopy gap) and EG (extended gap) were enlarged, gaps were more close to round and the boundary wood quantity were increased10.0%and3.0%respectively. After thinning in40years stand, CG and EG average area increased by10.19%and19.84%, EG and CG area proportion increased by35.24%and24.29%; In50years stand CG and EG average area increased by85.51%and50.23%; EG and CG area proportion increased by65.59%and22.95%.(2) In40years stand, pinus tabulaeformis was the only recruit tree species, in50years stand and clearing areas quantity proportion of pinus tabulaeformis were all above90%. From40to50years under the canopy density decreased from2.03/m2to4.90/m2; average height and base diameter increased progressively from26.04cm and4.33mm to29.79cm and4.98mm respectively; average age decreased from5.47to4.94. After clear cutting with the extension of time recruit density decreased progressively from2.10/m2down to0.72/m2; average height, base diameter and age increased progressively from82.03cm,21.71mm and5.85to159.23cm,37.52and7.06. In all sample plot distribution type of height and base diameter were unimodal. In40and50years stand, gap increased recruit density, and recruit density positively correlated and negatively correlated with gaps area respectively; the area of gap suitable for growth was gradually amplified with the increase of recruit age. Gaps had limited impact on the height, base diameter and age.(3) In40and50years stand and all clear areas age structures of pinus tabulaeformis populations were all unimodal type. Recruitment populations were mainly composed of3to7year,2to7years and4to8years in40years stand,50years stand and clear areas respectively. Pinus tabulaeformis age structures were imbalance, there was a serious shortage of seedling number below3years, the average life expectancy was short, generally mortality peak appeared in the eighth year, survival curves closed to Deevey type II.(4) In40and50years stand, the distribution of recruitment population presents a spatial aggregation at all scales under canopy. After clear cutting, the recruitment populations were all exhibited clumped distribution at smaller scales and random distribution at larger scales. Pinus tabulaeformis seedlings were always spatially independent of saplings. Canopy woods were always spatially independent of recruitment poulations. In40years stand, with the increase of gaps area the recruitment poulations were changed from random distribution to clumped at smaller scales and randomly distributed at larger scales. Aggregation intensity was decreased by gaps. In50years stand, the scale values corresponding to peak value of aggregation intensity increased with the increase of gap area.(5) In40years stand, litter density in10-15m2gaps was increased by21.28%and litter in the rest gaps was decreased by30.02-35.42%than that under canopy. Litter thickness and the effective rate in15to20m2were decreased by21.12%and16.60%than that under canopy, and there were no significant differences between that in rest gaps and under canopy. In50years stand, litter density in gaps was increased by16.95-65.61%than that under canopy. Gaps had no significant impact on litter thickness. The effective rate in gaps was decreased by15.73-27.91%than that under canopy. Herb biomass were18.1832.36%higher than that under canopy.2years to8years after clear cutting, litter density and thickness was increased by29.57%and51.64%, the effective rate and herb biomass were decreased by34.71%and19.61%, the trend was favour of settlement and growth of seedlings. In40and50years stand litter density, litter thickness and herb biomass had limited impact on recruitment density. Gaps and clear cutting fixed number of year influenced the spatial heterogeneity of litter characteristics and herb biomass density,(6) After final felling the stand would become multi-layer uneven-age Chinese pine stand in future, the heterogeneity of vertical structure and age structure would be enhanced. However, the stand will still have the difficulty of low tree species diversity. Therefore to enhance the tree species diversity and to establish stratified uneven-aged mixed forest should be considered to induce other tree species in the case of lack of other tree provenance. Therefore, it is necessary to create larger gaps and clear tapes in different age stand to to find out the most effective interference measurements.更多还原