竹木混生林中观光木的空间结构及竞争力比较

Comparison of Spatial Structure and Competitiveness o f Tsoongiodendron odorum in Bamboo-wood Mixed Forest

于2020年3—5月,在福建省明溪县夏阳乡的竹木混生林中,采用3种择伐方式(HW、HE、JW处理),以不间伐的林分作为对照(CK),选择观光木为对象木,与观光木相邻的4株林木作为竞争木,测定混交度(M_(i))、角尺度(W_(i))、密集度(C_(i))等主要空间结构指标,并采用Hegyi竞争模型计算观光木竞争指数,对其空间结构及竞争力进行综合评价。结果表明,对照(保留竹木混生林原有状态)中,观光木的M_(i)、W_(i)、C_(i)分别为1.0、0.6667、0.7083,属极重度混交,呈团状、密集分布;同一高度级林木竞争指数基本上高于择伐处理,由于空间结构不合理,观光木受到以毛竹为主的竞争木上层遮盖和侧方挤压程度大,竞争力较低。择伐处理中,以HE处理(以对象木为中心,砍伐半径2 m范围内所有竞争木)效果最好,观光木的M_(i)、W_(i)、C_(i)分别为1.0、0.3125、0.2500,混交度仍属极重度混交,但分布格局呈均匀、开阔分布,同一高度级竞争指数较大幅度降低,观光木竞争力增强;不同高度级观光木的平均竞争指数存在差异,小于10~12 m高度级观光木的平均竞争指数基本大于0.5;大于10~12 m高度级的观光木竞争指数在0.1280~0.4870之间,竞争指数较大幅度降低,趋于平稳,观光木竞争力增强。在观光木树高达到10 m之前,采取人工干预是必要且关键的技术措施。

From March to May 2020,three selection cutting methods(HW,HE,JW)were adopted in the bamboo-wood mixed forest in Xiayang Township,Mingxi County,Fujian Province.The survey,taking forest stand without tending cutting as the control check,Tsoongiodendron odorumas the observation group,and four trees adjacent to Tsoongiodendron odorumas competing trees,got the main indexes of spatial structure,including mixing degree(M_(i)),angular scale(W_(i))and density(C_(i)),which were analized by Hegyi competition model to calculate the competition index of Tsoongiodendron odorum.The results showed that the M_(i),W_(i) and C_(i) of Tsoongiodendron odorum in the control group were 1.0,0.6667 and 0.7083 respectively,which was regarded as extremely heavy mixed forest with clumpy and dense distribution.The competition index of trees at the same height level is basically higher than that of woods with selection cutting treatment.The competitiveness of Tsoongiodendron odorum is low due to unreasonable spatial structure,because the Tsoongiodendron odorum are covered and occupied space by the competing trees,mainly Phyllostachys heterocycla.Tsoongiodendron odorum with HE treatment(with the target trees as the center and all competing trees within a radius of 2 m)had the best effect,the M_(i),W_(i) and C_(i) of which were 1.0,0.3125 and 0.2500.The mixing degree was still extremely severe,but the distribution pattern was uniform and open,and the competition index of the same height class was significantly reduced.Tsoongiodendron odorum competitiveness increased;the average competition index of Tsoongiodendron odorum with different height classes is different.When the height is less than 10~12 m,the average competition index of Tsoongiodendron odorum is basically higher than 0.5.When the height is higher than 10~12 m,the competition index of Tsoongiodendron odorum is between 0.1280 and 0.4870.The competition index decreases significantly and tends to be stable,and the competitiveness of Tsoongiodendron odorum is enhanced.Based on the survey,it is necessary and key technical measures to take manual intervention before the height of Tsoongiodendron odorum reaches 10 m.