粤北山地常绿阔叶林自然干扰后冠层结构与林下光照动态

以粤北车八岭2008年受冰灾破坏的山地常绿阔叶林为研究对象,设置2 hm2固定样地开展连续3a(2008—2010年)的群落调查,并采用半球面影像技术(Hemispherical photography)获取冠层结构和林下光照指标,分析灾后森林演替过程中冠层结构和林下光照的动态。研究发现:1)灾后森林恢复过程中,样地林下光照(直射光、散射光和总光照)均随林冠开度的减少、叶面积指数的增加而减少;2)从2008到2010年,各年度冠层结构和林下光照的差异均极显著(P<0.0001),但年间差异程度有逐年减少的趋势;3)灾后森林恢复前3a,林下直射光对林下总光照的贡献大于散射光,其时空波动性也大于散射光;4)林冠开度对冠层结构的反映程度比叶面积指数高,冠层结构对林下散射光的影响比对直射光大。灾后林木先是迅速生长然后生长速度缓慢下来并逐渐稳定,随森林逐渐郁闭林下光照也随之减少,其中林冠开度用于评价冠层结构动态的效果更佳,林下直射光比散射光的时空变化更复杂。

Dynamics of canopy structure and understory light in montane evergreen broadleaved forest following a natural disturbance in North Guangdong

Montane evergreen broadleaved forest of Chebaling National Nature Reserve in north Guangdong followinging a huge ice storm in 2008 was targeted as research object, and a successive 3-year (2008-2010) community investigation of the 2 hm₂ permanenbt plot was launched. We analyze the changes of canopy structure and understory light in forest succession following the ice storm using hemispherical photography to acquire canopy structure and understory light index. Main conclusions were showed as following: 1) As the canopy openness shrunk and the leaf area index increased, the understory light (Transmitted Direct Solar Radiation, Transmitted Diffuse Solar Radiation and Transmitted Total Solar Radiation) decreased in the forest recovered process following the ice storm; 2) A highly significant difference (p<0.0001) was detected in canopy structure and understory light among the 3 years, but between-year difference showed a decreasing tendency as forest recovered from 2008 to 2010; 3) In the first three years of forest recovery, transmitted direct solar radiation possessed a greater spatial-temporal fluctuation and demonstrated a greater contribution to total solar radiation than did transmitted diffuse solar radiation;4) Canopy openness was more sensitive than leaf area index as in indicating canopy structure change, while canopy structure had a greater influence on transmitted diffuse solar radiation than transmitted direct solar radiation. Therefore, studies to research the effect of ice storm on the canopy structure of subtropical forest, to reveal dynamics of canopy structure and understory light followinging an ice storm, and to monitor the restoration of damaged forest ecosystem, will have significant implications in both theoretical improvement and application.