采伐方式对米老排人工林天然更新的影响

Effects of cutting methods on natural regeneration of Mytilaria laosensis plantation

【目的】基于米老排树种生物学特性,探索采伐方式对米老排人工林天然更新的影响,为其天然更新利用和可持续经营提供科学依据。【方法】以南亚热带米老排人工林为对象,按单因素完全随机试验设计方法,设计3种采伐处理(TA:带状皆伐作业,皆伐迹地带宽约为100 m,顺坡长度大于100 m,两侧不采伐保留带宽度均不少于30 m;TB:沿顺坡方向带式渐伐,渐伐带宽约50 m,渐伐后林分保留密度120~150株/hm^2;TC:皆伐,作业面积4.0 hm^2)和1种对照CK处理(沿顺坡方向,保留宽度为50~100 m的不采伐保留带),每个处理布设3块样地。基于数据处理系统(DPS14.5),采用单因素方差分析和最小显著差异法(LSD),对米老排人工林不同采伐作业后天然更新幼树的更新密度、更新频度、生长等进行分析。【结果】(1)在采伐与抚育作业2年后,所有采伐处理迹地天然更新幼树(树高>1.3 m)的更新效果均可达到天然更新的良级标准(更新密度大于3000株/hm^2,更新频度大于60%),但仅有TC处理种子更新幼树的更新效果达到采伐迹地天然更新的良级标准。(2)在带状皆伐迹地内,米老排天然更新效果随林缘距离的增加而递减,仅能在距林缘18 m范围内(单侧林缘距离范围)达到天然更新良级标准。(3)采伐处理与对照处理相比,前者米老排天然更新的效果远高于后者。(4)在0~10 m尺度内,米老排人工林及其采伐迹地种子更新幼树的空间分布多为非单一的分布类型,并呈规律性变化(先呈聚集分布,随后再呈随机分布或均匀分布)。【结论】(1)在采伐处理与对照处理样地之间,采伐与抚育措施对米老排种子更新幼树的空间分布类型影响不明显,对促进种子更新幼树更新密度和更新频度的影响极显著(P<0.01),对改变种子更新幼树的径级分布作用明显。(2)在米老排人工林落种高峰期(其落种高峰期在10月下旬至12月中旬)外的带状皆伐作业,其作业的带宽宜控制在36 m内。(3)光照是影响米老排人工林天然更新幼树建成的关键因子,利用米老排人工林的落种期和天然更新特性(落种在空旷地易萌发),采用皆伐、渐伐与带状皆伐均可有效实现其采伐迹地的天然更新。

[Objective]To provide a scientific basis for the utilization of natural regeneration and sustainable management of Mytilaria laosensis plantation,the effects of cutting methods on natural regeneration of M.laosensis plantation were explored based on biological characteristics of M.laosensis tree species.[Method]Using one-factor completely random design,three kinds of cutting treatments and one kind of control(CK treatment)were conducted with the plantation in the southern subtropical area of China,the three cutting treatments were respectively TA treatment(strip clear-cutting,width of strip clear-cutting land was about 100 m,slope length was more than 100 m,width of each reserve belt was not less than 30 m),TB treatment(strip shelter wood cutting,width of strip shelter wood cutting was about 50 m,the reserve density of the stand was 120-150 plants per hectare),TC treatment(clear-cutting,cutting area was 4.0 hectare),and CK treatment(along the slope direction,reserve no cutting belt with a width of 50-100 m).Each kind of cutting treatment was surveyed with three sample plots.The differences in regeneration density,regeneration frequency and growth of natural regeneration saplings of tree species of M.laosensis plantation with different cutting methods were analyzed using one factor analysis of variance(one way AVOVA)and least significant difference method(LSD)with data processing system(DPS14.5).[Result](1)In the cutting land,after 2 years forest tending,the regeneration effects of natural regeneration saplings(tree height>1.3 m)in all cutting treatment land could reach good grade standard(regeneration density was greater than 3000 trees per hectare,and regeneration frequency was more than 60%),while only the regeneration effects of seed regeneration saplings of TC treatment could reach the good grade standard of natural regeneration.(2)In the strip clear-cutting land,the effects of natural regeneration of the species decreased with the increase of forest edge distance,and could reach good grade standard of natural regeneration only within 18 m distance range from forest edge(unilateral distance range from the forest edge).(3)The effects of natural regeneration in the cutting treatment were much better than the CK treatment.(4)During the scale of 0-10 m,the spatial distribution of natural regeneration saplings in the plantation and its cutting land mostly was non-single distribution type,and presented regular change(aggregation distribution at first,then random distribution or uniform distribution).[Conclusion](1)Between the cutting treatment plots and CK treatment plots,there were no significant effects with different cutting methods and forest tending on the spatial distribution types of seed regeneration saplings of M.laosensis,but cutting and tending treatment had an extremely significant effect in promoting the density and frequency of seed regeneration saplings(P<0.01),and had an obvious effect in changing the diameter distribution of seed regeneration saplings.(2)If strip-cutting operation was in peak period of seed rain of the plantation(the seed rain peak was from late October to late December),the width of strip clear-cutting should be controlled within 36 m.(3)Light was the key factor affecting the establishment of natural young trees in the plantation.Any kinds of cutting methods(clear-cutting,strip shelter wood cutting and strip clearcutting)could effectively realize good grade standard of natural regeneration on the cutting land by taking advantage of falling period of seed rain and natural regeneration characteristics of the plantation,falling seed was easy to germinate at open ground,and sprout of the stump was easy to germinate.