摘要
高山森林冬季不同厚度雪被格局可能通过影响凋落物的分解过程中酸溶性和酸不溶性组分特征,改变凋落物分解过程,但缺乏必要关注。采用凋落物分解袋法,研究了高山森林林窗中央至林下形成的天然雪被厚度梯度(厚型雪被、中型雪被、薄型雪被和无雪被)覆盖下,6种典型物种岷江冷杉(Abies faxoniana)、红桦(Betula albo-sinensis)、四川红杉(Larix mastersiana)、方枝柏(Sabina saltuaria)、康定柳(Salix paraplesia)和高山杜鹃(Rhododendron lapponicum)凋落物在不同关键时期(雪被形成期、雪被覆盖期和雪被融化期)的酸溶性组分和酸不溶性组分变化特征。经历一个冬季的分解后,6种凋落物酸溶性组分绝对含量呈降低趋势,除红桦外5种凋落物酸不溶性组分绝对含量呈增加趋势。不同厚度雪被显著影响雪被覆盖期和融化期凋落物酸不溶性和酸溶性组分绝对变化量;其中方枝柏、红桦和康定柳凋落物酸不溶性组分增加量在厚型雪被下显著高于其它雪被覆盖;而相对于阔叶凋落物酸溶性组分变化量在薄型雪被和无雪被梯度达到最大值,针叶凋落物酸溶性组分在厚型雪被下具有最大的变化量。一个冬季分解结束后,表征6种凋落物酸溶性和酸不溶性组分含量相对比例的LCI指数(Lignocellulose index)总体升高,雪被对LCI指数的影响主要表现在雪被覆盖期和融化期,且方枝柏、岷江冷杉和康定柳凋落物LCI在冬季分解后均在厚型雪被达到最高值。同时统计分析结果表明,物种极显著影响冬季不同阶段凋落物酸溶性和酸不溶性组分的变化。这些结果意味着气候变暖情景下,高山森林冬季雪被和冻融格局的改变将显著影响凋落物分解过程中酸溶性、酸不溶性组分以及LCI指数代表的抵抗性组分结构的变化,且影响趋势受到凋落物质量的调控。
Acid-soluble extractive （ASE） and acid-insoluble residue （AIR） are two essential and play an important role in the litter decomposition. Changes in ASE and AIR concentrations components in foliar litter, are not only one of crucial processes in litter decomposition, but also run the process of mineralization and humification of organic materials in litter to a large extent. Theoretically, ASE and AIR concentrations in litter vary with tree species, precipitation, soil temperature and moisture, and other biotic and abiotic factors. In the alpine forest ecosystem, the interception of canopy on snow accumulation and the effects of canopy shading on snow ablation in winter often create a snowpack gradient on the forest floor between the center of a gap and under the forest canopy in snowy season, and in turn might give strong effects on the dynamics of ASE and AIR in litter inside and outside of the canopy gap. As yet, little information has been available on the effects of snow cover on ASE and AIR concentrations in litter at different critical periods. Therefore, litterbags with foliar litter of birch （ Betula albo-sinensis ） , cypress （ Sabina saltuaria ） , larch （ Larix mastersiana ） , fir （ Abies faxoniana ） , willow （Salix paraplesia）, and azalea （Rhododendron lapponicum） were placed on the forest floor along snow over gradients （deep snow, medium snow, thin snow and none snow） created by forest gap, canopy edge, expanded edge and closed canopy in three alpine forests of eastern Tibet Plateau. The litterbags were sampled at the stages of snow formation, snow cover and snow ablation from October 2012 to April 2013, and the concentrations of ASE and AIR in sampled litter were measured in time. Meanwhile, the LCI （Lignocellulose index ） was also calculated. Over the first winter of litter decomposition, the absolute ASE concentration in foliar litter continued to decline as litter decomposition proceeded regardless of plant species, while AIR concentration in foliar litter increased except for birch leaf litter. Snow cover gave significant （P〈0.05） effects on ASE and AIR concentrations in foliar litter at snow cover and ablation stages regardless of plant species. Absolute AIR concentration in cypress, birch and willow litter beneath deep snowpack increased more significantly in comparison with those beneath shallow and no snowpacks. The response of ASE concentration in foliar litter to snow cover depended on plant leaf forms. The maximum changes of absolute ASE concentrations in broadleaf litter were found beneath the thin and no snowpacks, whereas those in needle litters showed the opposite trend. After a snowy season, LCI, an index of indicating the relative changes of ASE and AIR concentrations in foliar litter increased significantly （ P〈 0.05） regardless of plant species. The effects of snowpacks on LCI in foliar litter were observed mainly at the stages of snow cover and ablation, and the foliar litter of cypress, fir and willow had the highest LCI beneath the deep snowpack. In addition, the statistical analysis revealed that the＇ wintertime dynamics of ASE and AIR concentrations and LCI in foliar litter were influenced significantly （P〈0.01） by litter quality determined by plant species. The results here imply that the changes of winter snow cover pattern as affected by winter wanning and forest gap regeneration will give a strong effect on the dynamics of ASE and AIR concentrations and the relative ratios of ASE to AIR in foliar litter, and in turn alter the process of mineralizaition and humification of organic materials in the alpine forest ecosystems. However, the effects of snow cover on the dynamics of ASE and AIR concentrations also depend on litter quality related with plant species.
出处
《生态学报》
CAS
CSCD
北大核心
2015年第14期4687-4698,共12页
Acta Ecologica Sinica
基金
国家自然科学基金项目(31170423
31270498)
国家"十二五"科技支撑计划(2011BAC09B05)
四川省杰出青年学术与技术带头人培育项目(2012JQ0008
2012JQ0059)
中国博士后科学基金特别资助(2012T50782)
关键词
雪被
高山森林
凋落物分解
酸溶性组分
酸不溶性组分
snow cover
alpine forest
litter decomposition
acid-soluble extractive
acid-insoluble residue
