抚育对黄土高原人工油松林林下植被的影响

Effects of Tending on Undergrowth Vegetation of Artificial Pinus tabuliformis Forests on the Loess Plateau

2015年3月旬邑县林业局开展了人工林抚育项目,对清水沟管护区内的人工林进行抚育,主要措施是卫生伐。为了探讨抚育对油松人工林林下植被的短期影响,本文以此抚育项目为研究基础,对黄土高原45 a人工油松林的抚育区和未抚育区进行研究,分析抚育1.5 a后人工油松林林下植被结构、物种多样性和生物量的变化情况,为黄土高原油松人工林的科学抚育提供理论依据及为抚育后长期动态的研究提供基础数据。结果表明,(1)抚育区和未抚育区林下植物种数分别为59种和49种。抚育区和未抚育区灌木层的Simpson指数、Shannon-Wiener指数和Pielou均匀度指数分别为0.786 0、2.069 6、0.734 4和0.777 9、2.028 6、0.712 3,无显著差异(P>0.05);草本层的Simpson指数、Shannon-Wiener指数和Pielou均匀度指数分别为0.713 6、1.543 4、0.755 8和0.660 6、1.328 7、0.805 3,仅Shannon-Wiener指数差异显著(P<0.05)。(2)抚育后,林下灌木层的盖度从74.16%下降到22.8%,草本层盖度由12.11%增加到33.8%;草本层密度由57 125 plant?hm^(-2)增加到155 595 plant?hm^(-2),灌木层密度由13 620 plant?hm^(-2)下降到12 780 plant?hm^(-2);灌木层生物量由1 377.62 kg?hm^(-2)减少到324.87kg?hm^(-2);草本层生物量由138.87 kg?hm^(-2)增加到371.69 kg?hm^(-2)。(3)抚育后林下植被生物量在各个器官和物种中的分配比例发生了明显变化。抚育后灌木层和草本层一些喜光或喜温暖湿润环境的物种的生物量贡献率增加;灌木层地下部分生物量与地上生物量比例显著增加,由0.86增加到1.62;而草本层与之相反,由1.43下降到0.92。从总体上看,人工抚育措施虽然降低了灌木层的生物量、盖度和密度,但是有助于灌木层的物种多样性和草本层的物种多样性、生物量、密度和盖度的增加。这些试验结果说明抚育对油松人工林林下植被的影响短期内主要表现在草本层植物上,对灌木层植物的影响较小。

In March2015,the artificial Pinus tabuliformis forest in Qingshuigou conservation area was tended by the Xunyi CountyForestry Bureau.The main measure was sanitation cutting.To study the short-term impact of tending measures on the growth statusof the understory vegetation of the artificial P.tabuliformis forest,we studied the tending and non-tending areas of a45-year-oldartificial P.tabuliformis forest on Loess Plateau.Changes on vegetation structure,species diversity and biomass of understory plantswas detected on tended areas.This study aimed to provide theoretical basis for the scientific tending of P.tabuliformis plantation onLoess Plateau and to provide empirical data for studies of long-term dynamic.The results showed that the total number of plantspecies were59and49in tending and non-tending areas respectively.The value of Simpson index,Shannon-Wiener index andPielou index of shrubs were0.7860,2.0696,0.7344and0.7779,2.0286,0.7123in the tending and non-tending areas respectively.They were not significantly different with each other(P>0.05).The value of Simpson index,Shannon-Wiener index and Pielou indexof herbs in the tending and non-tending areas were0.7136,1.5434,0.7558and0.6606,1.3287,0.8053.The Shannon-Wienerindex of the herb layer was significantly different(P<0.05).The coverage of shrub layer decreased from74.16%to22.8%,and thecoverage of herb layer increased from12.11%to33.8%after tending.The density of herb layer increased from57125plant?hm-2to155595plant?hm-2and the density of shrub layer decreased from13620plant?hm-2to12780plant?hm-2.The biomass of shrub layerwas reduced from1377.62kg?hm-2to324.87kg?hm-2and the biomass of herb layer increased from138.87kg?hm-2to371.69kg?hm-2.The allocation of biomass in different species and organs in undergrowth were significantly changed by tending measures.The proportion of biomass contribution of heliophytes and hygrophytes increased after tending.The belowground and abovegroundmass ratio of the shrub layer significantly increased from0.86to1.62while that of the herb layer decreased from1.43to0.92aftertending.In sum,artificial tending measures reduced the biomass,coverage and density of shrubs,however,it increased the speciesdiversity of shrubs and the species diversity,biomass,coverage and density of herbs.The results indicate that tending measures mayhave a significant impact on herbs and little impact on shrubs on a short time scale.