【作者】 许建伟；

【导师】 沈海龙； 张鹏；

【作者基本信息】 东北林业大学 ， 森林培育， 2010， 硕士

【摘要】 花楸树(Sorbus pohuashanensis)系蔷薇科花楸属植物,落叶乔木,产于东北山区、华北；单株散生或簇状分布于高海拔的山地暗针叶林内,是寒温带针叶林特有的伴生阔叶树种。该树作为我国北方重要的天然非木质资源树种,被开发的力度逐年加大,部分地区出现了种群衰退甚至是消失的迹象。因此,本项研究通过对其野生幼苗建成方式和种群年龄结构配置的调查以及对其更新过程中种子散布、土壤种子库及幼苗萌发出土等生态过程的研究,认识该树种的更新特征和更新过程的影响因素,为其野生资源扩大及合理开发提供科学依据。研究结果表明：在东北东部林区,花楸树以种子繁殖、桩蘖繁殖和根蘖繁殖3种方式更新。在未经破坏的天然林和恶劣生境下的天然林中,3种方式建成的幼苗数量比例各占1／3,无显著差异；但在破坏后形成的次生林中,桩蘖苗比例(16.5%)明显降低。实生苗和根蘖苗在3种生境下的建成比例差异不显著；而桩蘖苗在破坏后形成的次生林中的建成比例显著低于另2种生境下的比例(P<0.05)。在破坏后形成的次生林、恶劣生境下的天然林和未经破坏的天然林中,Ⅰ、Ⅱ级幼苗占各生境下总径级比例的76.0%、68.9%和75.8%。1.0～2.9 cm的Ⅱ径级向3.0～4.9cm的Ⅲ径级的转化率很低,在破坏后形成的次生林、恶劣生境下的天然林和未经破坏的天然林中,Ⅱ径级向Ⅲ径级的转化率分别为25.6%、45.3%和15.9%。花楸树的果实在9月上旬开始成熟散落,10月中下旬已基本完成散落,大约历时40 d左右。自然散落过程与风速、温度、降水量和空气湿度相关不显著。自然散落的花楸树果实96.1%分布于母株2 m范围内,凋落物层和土壤表层2 cm的种子占土壤种子库数量的97.0%。花楸树土壤种子库在时间分布上具有不连续性,散布当年11月上旬最大,为257.7±69.2粒·m-2；翌年7月下旬种子库数量最低或已消失,只为2.9±2.9粒·m-2。温度没有直接限制花楸树种子的萌发出土过程,0-5℃时幼苗就能出土,出苗率为(67.5±6.6)%；20℃时出苗率最高,为(81.5±1.9)%。但温度强烈调节着花楸树的出苗速率和幼苗的高生长,前7d和前21 d幼苗的最高高度均在25℃下,分别为2.5±0.1 cm和3.1±0.1 cm,随温度下降幼苗高生长明显下降,前7d和前21 d幼苗最低高度均出现在0～5℃,分别为0.6±0.1 cm和1.8±0.2 cm。土壤含水量不仅影响花楸树的出苗率,而且也调节花楸树出土幼苗的死亡率。花楸树种子在土壤含水量为50%时出苗率最高,为(74.7±4.2)%；在含水量为60%时幼苗死亡率最低,为(32.7±0.6)%。此外,种子埋藏深度对花楸树出苗率也有显著影响。种子播在土壤表层0cm处,出苗率最高,为(70.3±3.3)%；当埋藏深度达到或超过1.5 cm时,幼苗就不能萌发出土通过以上结果分析得出：生境对花楸树幼苗的建成方式具有影响,人为破坏能够明显减少桩蘖苗的建成；充足的幼苗库不是限制花楸树种群天然更新的因素,而Ⅱ径级往Ⅲ径级的转化是限制花楸树天然更新的关键环节；种子扩散过程对天然更新无显著影响,但种子库的时空格局对花楸树的天然更新具有显著影响；温度可能是通过密度制约影响花楸树幼苗群体出土与存活进而影响其实生更新,而不是通过限制个体幼苗萌发出土过程而影响其实生更新；土壤含水量及种子埋藏深度是影响花楸树实生更新的重要因素。更多还原

【Abstract】 Sorbus pohuashanensis is deciduous tree in the genus Sorbus of Rosaceae native to northern China. It is an endemic accompanying broad-leaved species in boreal coniferous forest and mountain dark coniferous forest distributed in single-scattered or contagious patterns. As an important non-timber tree species in Northeast China, S. pohuashanensis has been over-developed recently and its population declined or even disappeared in some areas. In the paper, we investigated the wild seedlings establishment, population age structure, seed natural dispersal, soil seed bank and seedling emergence for the purpose of understanding the natural regeneration characteristics of this species and its influencing factors. The research results can provide scientific support for the rational protection and silviculture of the wild resources of Sorbus pohuashanensis.The results are as follows:S. pohuashanensis in eastern forest region of Northeast China regenerated by seed, stump sprouting and root sprouting. The line method of sampling indicated that roughly a third of the population was established by each regeneration method in S. pohuashanensis forests; in fact, there was no significant difference (P>0.05) among tree proportions established by these propagation methods whether in intact natural forests or in natural forests on stony sites. In secondary forests formed after damage, the frequency of stump sprouts (16.5%) was lower than in natural forests. Establishment ratio of seedling and root sprouts were no significant difference (P>0.05) among secondary formed forests after damage, intact natural forests and natural forests on stony sites; but significant difference (P<0.05) was detected for establishment ratio of stump sprouts between secondary forests formed after damage and intact natural forests or natural forests on stony sites.There was 76.0% of S. pohuashanensis whose diameter is less than 2.9 cm in secondary forests formed after damage; the result was 68.9% and 75.8% in natural forests on stony sites and intact natural forests respectively. The transfer rate from diameter classⅡ(1.0-2.9 cm) to diameter classⅢ(3.0-4.9 cm) was 25.6% in secondary forests formed after damage,45.3% in natural forests on stony sites and 15.9% in intact natural forests.The fruit ripening and natural dispersal of S. pohuashanensis last about 40 days that began in early September and ended in mid or late October. There was no significant correlation between the fruit dispersal of S. pohuashanensis and wind speed, air temperature, precipitation and air moisture content. Field tests found that there were 96.1% naturally dispersed seeds of S. pohuashanensis distributed within the range of 2 m around the stock tree.97.0% seeds in soil seed bank of S. pohuashanensis were distributed in the litter layer and 2 cm deep surface soil with a discontinuous temporal pattern, i.e., soil seed bank of S. pohuashanensis reached its maximum with 257.7±69.2 seeds per square meter in early November in current year of seed dispersal, and decreased to its minimum with less than 2.9±2.9 seeds per square meter in next July.Temperature had no obvious direct limitation effect on seedling emergence process of S. pohuashanensis, and seedling emergence can occurred at 0～5℃with (67.5±6.6)% seedling emergence percentage, the highest seedling emergence (81.5±1.9)% occurred at 20℃. But temperature strongly regulated seedling emergence rate and height growth of S. pohuashanensis. Maximum height of seedlings of S. pohuashanensis occurred under 25℃at the 7th day and the 21st day of germination tests with the seedling height of 2.5±0.1 cm and 3.1±0.1 cm respectively; and minimum height of seedlings of S. pohuashanensis occurred under 0～5℃at the 7th day and the 21st day of germination tests with the seedling height of 0.6±0.1 cm and 1.8±0.2 cm respectively. Soil moisture content not only affected seedling emergence percentage of S. pohuashanensis, but also adjusted the seedling mortality. The most proper soil moisture content for seedling emergence was 50%, seedling emergence percentage could reach (74.7±4.2)% in this situation; when soil moisture content was up to 60%, and seedling mortality was lowest to (32.7±0.6)%. Besides, the seed buried depth had a highly significant differences effect on seedling emergence (P<0.01). Seedling emergence of S. pohuashanensis decreased from (70.3±3.3)% to 0 with increasing soil depth from 0 to 1.5 cm.We conclude that habitats have certain effect on seedlings establishment types of S. pohuashanensis, and human disturbance could significantly reduce the establishment ratio of root sprouts. Adequate seedling bank was not a limiting factor of S. pohuashanensis natural regeneration, but the transfer rate from diameter class II to diameter class III was very lower and was the key limit factor for S. pohuashanensis natural regeneration. Seed dispersal process had no significant effect but the temporal and spatial pattern of soil seed bank had significant effect on S. pohuashanensis natural regeneration. Temperature may be a limiting factor for S. pohuashanensis natural regeneration through density-dependent effects on seedling emergence and survival, rather than by limiting individual seedling germination process effect natural regeneration. Soil moisture and burial depth were the crucial factor in S. pohuashanensis natural regeneration.更多还原