雪灾后粤北山地常绿阔叶林优势树种幼苗更新动态
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广东省2009年度"森林生态科技研究和推广"项目; 广东省科技计划项目(2008A020100013)


Dynamics ofdominant tree seedlings in montane evergreen broadleaved forest following a snow disaster in North Guangdong
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    摘要:

    对遭受2008年雪灾破坏的车八岭山地常绿阔叶林进行连续3 a(2008-2010年)的监测,研究在冠层恢复过程中优势树种的林下幼苗动态,旨在了解幼苗灾后的更新规律及其对冠层结构变化(以叶面积指数LAI的变化来表示)的响应。结果表明,12个优势种的林下幼苗对冠层恢复有明显的响应。非参数的多元方差分析(perMANOVA)显示,优势种幼苗的组成和分布存在着极显著的年际差异(P<0.001);其中2008年与2009年及2010年的差异均极显著(P<0.001);2009年与2010年的差异不显著。这与冠层LAI的变化情况相应:2008年LAI最低,2009年LAI值迅速增加;2010与2009年相比LAI增长缓慢,并逐渐趋于稳定。不同的优势树种幼苗对样方中LAI变化的响应不同,阳性树种幼苗的相对多度和频度一般会随林分郁闭度的增加而锐减,阴性及耐阴树种幼苗数量则随冠层恢复而增加。随着冠层恢复,林下指示种截然变化。2008年的林下幼苗指示种为8个喜光的种类,而2010年则仅见较耐阴的香楠Randia canthioides 为指示种。指示种分析从另一个角度反映了幼苗对冠层恢复的响应。

    Abstract:

    Effects of a snowstorm on forest disturbance and the canopy changes caused by forest rehabilitation resulted in changes in tree seedling composition. The species and number of tree seedlings vary with the canopy-density dynamics and are embodied in the future species composition and structure of tree layer. With the aim of revealing the seedling regeneration pattern and its response to canopy changes (as indicated by changes in leaf area index ), a 3-year investigation from 2008 to 2010 was undertaken in Chebaling montane evergreen broadleaved forest. The dominant tree seedling dynamics under the recovering canopy was studied by establishing a 2 hm2 sampling area (comprised of fifty 20 m×20 m plots) following the snow storm in 2008. Data from sampling in 2008 identified the top 12 species ranked by their importance as the dominant tree seedling as follows: Castanopsis carlesii, Schima superba, Castanopsis fargesii, Neolitsea chuii, Styrax suberifolia, Alniphyllum fortunei, Cinnamomum porrectum, Randia canthioides, Machilus chinensis, Rhododendron moulmainense, Cinnamomum austrosinensis and Lithocarpus glaber. Dynamic analysis of these 12 species over the 3 years showed that fluctuation was detected in the ranking of the species’ importance values, among which 2009 and 2010 shared similar trends while 2008 showed a different trend. Castanopsis carlesii, Schima superba, Randia canthioides and Rhododendron moulmainense showed an increase in their ranking by importance value, whereas Neolitsea chuii, Lithocarpus glaber, Cinnamomum porrectum and Alniphyllum fortunei showed a decrease in their ranking. Styrax suberifolia, Cinnamomum austrosinensis and M. chinensis showed a decreased and then increased ranking while Castanopsis fargesii showed the opposite trend. The 12 dominant tree seedling species showed notable responses to canopy recovery. Permutation-based MANOVA (PerMANOVA) indicated that a highly significant difference was found in composition and distribution of dominant tree seedlings among the 3 years (P<0.001), which mainly existed between 2008 and 2009 (P<0.001), and 2008 and 2010 (P<0.001), with no significant difference occurring between 2009 and 2010. Variation in LAI showed a corresponding trend, with the lowest LAI obtained in 2008 and a great increase in LAI occurred in 2009, with a lower increment and tendency for a stable LAI observed in 2010 compared with LAI in 2009. The responses to LAI changes varied according to the seedling species. Heliophilous tree seedlings showed a sharp reduction in number with canopy recovery and shade increase, while shade and shade-tolerant tree seedlings increased in number with canopy recovery. Indicator species analysis (ISA) yielded distinct results. Eight species of heliophilous tree seedlings, namely Alniphyllum fortunei, Styrax suberifolia, Cinnamomum porrectum, Lithocarpus glaber, Schima superba, Neolitsea chuii, Machilus chinensis and Cinnamomum austro-sinensis were identified as indicator species in 2008, but only Randia canthioides, a shade-tolerant species, was determined as such in 2010, which further demonstrated the response of tree seedlings to canopy recovery from another aspect. Differences between tree seedling species in the 2 years after the snowstorm diminished gradually in the early stage of forest succession. Fluctuation in the importance-value ranking of the dominant tree seedling species inferred that understory acclimatization was still in equilibrium, and the canopy of the undamaged and less-damaged trees would continue to grow and expand to take advantage of the unused canopy space.

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区余端,苏志尧,解丹丹,柯娴氡,李镇魁.雪灾后粤北山地常绿阔叶林优势树种幼苗更新动态.生态学报,2011,31(10):2708~2715

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