采伐强度对杉阔混交人工林细根生物量及形态特征影响

Effects of Harvesting Intensity on Fine Root Biomass and Morphological Characteristics of Mixed Plantations of Cunninghamia lanceolata and Broadleaved Trees

[目的]比较杉阔混交人工林在不同采伐强度下细根生物量及形态特征的差异,探究林木细根生长与采伐强度的关系,以期为区域杉阔混交人工林科学经营提供基础数据和理论参考。[方法]以闽北杉阔混交人工林为研究对象,2011年8月实施4种不同采伐强度(按蓄积量计算分别为中度择伐34.6%、强度择伐48.6%、极强度择伐67.6%和皆伐100%)试验,并与未采伐对照;经自然恢复5 a后,采用根钻法分2层(0~10、10~20 cm)获取乔木树种活细根(≤2 mm),分析采伐强度对0~20 cm土层细根总生物量及形态特征的影响。[结果]中度和强度择伐细根总生物量分别为225.31、257.96 g·m^(−2),与未采伐(219.35 g·m^(−2))差异不显著(P>0.05),极强度择伐和皆伐分别比未采伐显著降低了47.0%和66.3%(P<0.05);各种强度的择伐下细根比根长和比表面积与未采伐无显著差异(P>0.05),皆伐比未采伐分别显著增大了41.5%和71.2%(P<0.05);细根根长密度和根表面积密度随采伐强度增大而变化的规律与细根总生物量的变化规律一致,极强度择伐比未采伐分别显著降低了51.9%和46.9%(P<0.05),皆伐比未采伐分别显著降低了54.9%和49.2%(P<0.05)。[结论]杉阔混交人工林不同采伐强度5 a后,中度和强度择伐仍能维持林木细根生物量和吸收水分与养分能力,而极强度择伐和皆伐都出现显著降低;从有效维持和促进林木细根生长的角度,建议类似林分适宜采伐强度不超过强度择伐。

[Objective]To compare the differences in fine root biomass and morphological characteristics of mixed plantation of Cunninghamia lanceolata and broadleaved trees under different harvesting intensities,reveal the relationship between fine root growth and harvesting intensity,and provide basic data and theoretical references for the management of regional mixed plantation of Cunninghamia lanceolata and broadleaved trees.[Method]A mixed plantation of Cunninghamia lanceolata and broadleaved trees in northern Fujian Province in China was used as the research object.Selective harvesting at medium intensity(34.6%removal of growing stock volume),high intensity(48.6%),at extra-high intensity(67.6%),and clear-cut harvesting(100%)were conducted and non-cutting as the control in August 2011.After 5 years of natural recovery,the basic data of biomass and morphological characteristics of living fine root(≤2 mm)of tree species were collected from two soil depths(0-10 cm and 10-20 cm)via root drilling methods.The influence of harvesting intensity on the total biomass and morphological characteristics of fine root in the 0-20 cm soil layer was analyzed.[Result]For the total fine root biomass,non-cutting,selective harvesting at medium and high intensities were 219.35,225.31 and 257.96 g·m^(−2),there was no significant difference among them(P>0.05).But the total fine root biomass under selective harvesting at extra-high intensity and clear-cut harvesting were significantly reduced by 47.0%and 66.3%respectively compared with non-cutting(P<0.05).For the specific root length and specific root surface area,there was no significant difference between selective harvesting at various intensities and non-cutting(P>0.05).The specific root length and specific root surface area under clear-cut harvesting were significantly increased by 41.5%and 71.2%respectively compared with non-cutting(P<0.05).The changes of root length density and root surface area density with harvesting intensity increasing were consistent with their change of total fine root biomass.The root length density and root surface area density under selective harvesting at extra-high intensity were significantly reduced by 51.9%and 46.9%respectively compared with non-cutting(P<0.05).The root length density and root surface area density under clear-cut harvesting were significantly reduced by 54.9%and 49.2%respectively compared with non-cutting(P<0.05).[Conclusion]5 years after harvesting,the fine root biomass and the ability to absorb water and nutrients of the mixed plantation of Cunninghamia lanceolata and broadleaved trees can be maintained under selective harvesting at medium and high intensities,but will be significantly reduced under selective harvesting at extra-high intensity and clear-cut harvesting.From the perspective of effectively maintaining and promoting the growth of fine roots of forest trees,it is recommended that suitable harvesting intensity of similar forests should not exceed the selective harvesting at high intensity.