冰雪灾害后的杉木人工林冠层结构与林下光照及土壤生化特性的关系

Relationships between Canopy Structure and Understory Light and Soil Biochemical Property in A Cunninghamia lanceolata Stand Suffering from Ice-snow Damage

2008年1—2月,雨雪冰冻天气袭击广东粤北地区,造成大面积的杉木(Cunninghamia lanceolata)林被破坏。探讨粤北地区冰雪灾害后杉木人工林冠层结构与林下光照及土壤生化特性的关系,对杉木林的恢复具有重要的实际意义。采用实地调查、半球面影像技术和稀释平板法等方法,研究恢复期间杉木林内不同林隙的冠层结构与林下光照、林下土壤微生物多样性和酶活性的关系,旨在为杉木林的恢复提供科学依据。结果表明,随着林隙面积的增大,林冠开度从10.93%增加到18.36%,叶面积指数从2.70减少到1.88,直射光从3.21mol·m^(-2)·d^(-1)增加到9.29mol·m^(-2)·d^(-1),散射光从3.02mol·m^(-2)·d^(-1)增加到5.41mol·m^(-2)·d^(-1),总光照从6.23mol·m^(-2)·d^(-1)增加到14.70mol·m^(-2)·d^(-1)。林冠开度与所在林隙范围、直射光、散射光和总光照均呈极显著正相关(P<0.01),与叶面积指数存在显著负相关(P<0.05)。叶面积指数与直射光、散射光和总光照均呈显著负相关(P<0.05)。各样方的细菌、真菌和放线菌数量分别为0.67~8.07×106、2.83~16.33×105和6.07~48.33×105CFU·g^(-1),脲酶、磷酸酶和过氧化氢酶活性分别为.34~1.88mg·kg^(-1)、196.20~418.03mg·kg^(-1)和1.00~2.00 mg·L^(-1)。林冠开度与磷酸酶及过氧化氢酶活性之间呈显著二项式关系。综上可见,冠层结构与林下光照及土壤酶活性的关系密切,一定范围内,较大的林冠开度的有利于受灾杉木人工林林下光照条件的改善和土壤酶活性的提高,但当林冠开度超过一定范围时,土壤酶活性下降。因此,冠层结构在一定程度上能决定林内光分布和反映土壤环境质量,进而影响林木整体的光合性能和林木恢复的速度。

A huge ice storm stroke on the north of Guangdong Province from January to February 2008,which resulted in damaged Cunninghamia lanceolata stands in a large scale.Relationship between canopy structure and understory light and soil biochemical properties were analyzed in a C.lanceolata stand suffering from ice-snow damage so as to provide a scientific basis for restoration of the damaged stands.Field investigations,hemispherical imaging techniques and dilution plate methods were used to study the relationships between canopy structure and understory light,undergrowth soil microbial diversity and enzyme activity in different gaps in the C.lanceolata stands during restoration.The results showed that with the increasing gap size area,canopy openness increased from 10.93%to 18.36%,leaf area index decreased from 2.70 to 1.88,direct light increased from 3.21 to 9.29 mol·m-2·d-1,scattering light increased from 3.02 to 5.41 mol·m-2·d-1,total light increased from 6.23 to 14.70 mol·m-2·d-1.Canopy openness had an extremely significant negative correlation with leaf area index and extremely significant positive correlations with the range of forest gap,direct light,scattering light and total light.The leaf area index had significant negative correlations with direct light,scattering light and total light.The number of bacterial,fungi and actinomycetes of the quadrats ranged from 0.67×106 to 8.07×106 CFU·g-1,from 2.83×105 to 16.33×105 CFU·g-1 and from 6.07×105 to 48.33×105 CFU·g-1,respectively.The activities of urease,phosphatase and catalase ranged from 0.34 to 1.88 mg·kg-1,from 196.20 to 418.03 mg·kg-1 and from 1.00 to 2.00 mg·L-1,respectively.Polynomial correlations existed between canopy openness and phosphatase activity as well as between canopy openness and catalase activity.In summary,the canopy structure is closely related to understory light and soil enzyme activity.Within a certain range,a large canopy opening is conducive to the improvement of understory light conditions and soil enzyme activity in the damaged C.lanceolata stand.When the canopy opening exceeds a certain range,the soil enzyme activity decreases.Therefore the canopy structure determines the light distribution and soil quality in forest stands.