对川西亚高山原始岷江冷杉（Abies faxoniana）林林窗内和林冠下小气候及岷江冷杉幼苗生长和生物量进行了两个生长季的连续观测。结果表明：6月林窗内与林冠下太阳辐射的日积累量没有显著性差异，而7～8月的日积累量则有显著性差异。整个生长季节，林窗内太阳辐射的平均积累量为8.10×MJ•m－2，而林冠下太阳辐射的平均积累量为5.02×MJ•m－2，两个位点太阳辐射积累量的显著差异主要来自7～8月日积累量的不同；林窗内5和15 cm层土壤的日平均温度比林冠下相应深度分别高2.1和2.7℃，差异显著。林窗内和林冠下3～8年岷江冷杉幼苗高增长率分别为1.2±0.3 cm•a－1和1.1±0.3 cm•a－1，差异不显著；9～20年岷江冷杉幼苗高增长率分别为6.2± 2.4 cm•a－1和3.0±0.9 cm•a－1，差异显著。林窗内岷江冷杉幼苗根、主茎和总生物量与林冠下幼苗根、主茎和总生物量没有显著差异。不同年龄的岷江冷杉幼苗叶和侧枝生物量积累对林窗微环境的响应不同。
Background and Aims Canopy gap disturbance drives successional dynamics of forest communities and shapes forest structure, dynamics and biodiversity in the western subalpine region of Sichuan. Gap microenvironment and responses of Abies faxoniana seedlings of different ages have not been investigated.
Methods During the growing seasons of 2002 and 2003, we continuously observed microenvironment (solar radiation and soil temperature at 5 and 15 cm depth) in canopy gaps in Abies faxoniana forest in Wanglang National Nature Reserve, Sichuan Province. We studied the growth of 3-20 year seedlings (basal diameter, height growth and biomass) in gaps and under canopy to determine responses to gaps.
Key Results Total daily solar radiation was slightly higher in gaps than under canopy in June, but was significantly higher than under canopy in July and August. From June to August, total solar radiation was 8.10×MJ•m-2 and 5 .02×MJ•m－2 in gaps and under canopy, respectively, and average soil temperatures at 5 and 15 cm deep were significantly higher in gaps than under canopy. The basal diameter of 3－8 year Abies faxoniana seedlings in forest gaps was a little smaller than under canopy, but the basal diameter of seedlings 9－20 years was larger in gaps than under canopy. Height growth rate of 3－8 year seedlings was 1.2±0.3 cm•a-1 and 1.1±0.3 cm•a-1 in gaps and under canopy, respectively , and for 9－20 years old was 6.2±2.4 cm•a-1 and 3.0±0.9 cm•a-1, respectively. The average total biomass of seedlings was a little higher in gaps than under canopy.
Conclusions Tree seedlings need more illumination with increasing age. Therefore, canopy gaps are an important impetus for growth, forest dynamics and regeneration in subalpine coniferous forest.