【作者】 戚裕锋；

【导师】 杨永川； 达良俊；

【作者基本信息】 华东师范大学 ， 生态学， 2010， 硕士

【摘要】 种子萌发、出苗和幼苗建立是森林更新的最初阶段,对植被格局的形成和发展起着重要作用。地形结构导致环境因子的差异性对于幼苗的建立和随后的树木生长起着决定作用。地形上幼苗动态的研究对于解释幼苗建立阶段在形成地形植被格局中的作用,进而深入理解小尺度空间植被格局的形成以及对植被恢复的作用都有重要的理论和实际意义。本研究在植被调查的基础上,选择了7种微地形优势种,通过室内种子萌发试验结合室外种子直播和幼苗监测的方法探究了不同微地形上种子萌发、出苗以及幼苗早期建立的过程,揭示了幼苗早期建立阶段对这些树种在现有微地形上占据优势地位中的作用,主要结论如下：(1)室内萌发实验表明,7种种子具有休眠或持续低萌的萌发策略。云山青冈、长叶石栎、栲树和南酸枣的种子含水量超过30%；雷公鹅耳枥、木荷和西川朴的含水量在10%～20%之间。雷公鹅耳枥和南酸枣的萌发率为0,具有休眠特性,而其他种子的萌发率都小于60%,云山青冈最高为56.50±7.14%,栲树最低为6.00±1.42%。(2)微地形、光照环境之间总空隙度存在极显著的差异(p<0.01)。上部坡面的总空隙度都要大于下部坡面。各微地形随着海拔高度的逐渐增加,总空隙度呈现逐渐上升的趋势。微地形和光照环境对土壤侵蚀影响不显著(p>0.05)。土壤含水量在微地形之间存在极显著的差异(p<0.001),林内和林窗无显著差异(p=0.067)。上部坡面的土壤含水量明显大于下部坡面。在各个月份中,呈现出上部坡面土壤含水量总是大于下部坡面的趋势。(3)7种种子在微地形上表现出不同的出苗策略。A组的雷公鹅耳枥和木荷出苗时间最早,B组西川朴和南酸枣出苗时间次之,A组的云山青冈、长叶石栎和栲树的出苗时间最迟。雷公鹅耳枥和木荷,以及西川朴在早期(4月)幼苗数达到最大值,但具有高的死亡率,而南酸枣在5、6月(CS3在7、8月)达到最大幼苗数,死亡率平缓。栲树、云山青冈和长叶石栎在第1个生长季末才达到最大幼苗数,但存活率较高。(4)出苗率受一个或多个环境因子的影响,在微地形上的差异性并不明显。除长叶石栎和西川朴的出苗率与土壤水分、总空隙度和土壤侵蚀无显著的相关性外,其他树种的出苗率至少与其中一个因子相关。林内和林窗的出苗率并无显著差异(除南酸枣在下部坡面,p<0.001)。上下坡面对树种的出苗率影响不大(除南酸枣在林内,p=0.048)。雷公鹅耳枥和栲树的出苗率在各微地形上不存在显著的差异。木荷、云山青冈、长叶石栎、西川朴和南酸枣的出苗率除了在少数几个微地形上表现出显著差异外,在各微地形上差异性也非常小,说明出苗率在微地形单元尺度上并不存在较为明显的分异。(5)不同树种的幼苗存活率和死亡率存在着较大的差异性,且受环境和生物因子的影响。云山青冈、长叶石栎、栲树的存活率较高,长叶石栎和栲树在一些微地形上的存活率可达到100%,雷公鹅耳枥的存活率相对较低。除雷公鹅耳枥外,所有树种的幼苗存活率都随着土壤含水量的增加而降低。总空隙度的增加显著提高雷公鹅耳枥、木荷、云山青冈、栲树的幼苗存活率。雷公鹅耳枥、木荷和云山青冈的幼苗存活率随着土壤的增加而降低。就所能观察到的死亡个体中,枯萎是雷公鹅耳枥、木荷、西川朴和南酸枣幼苗死亡最主要的原因,而云山青冈和长叶石栎的主要死亡原因是物理损伤。(6)所研究树种的幼苗在各微地形中的建立总体差异不大,仅在个别微地形之间表现出一定的差异性,且与成体在微地形上的分布格局无关。这些不能很好地解释所研究树种的成年植物个体在本研究地的微地形上分异的现象。种子萌发、出苗和幼苗建立是种子生物学特性和生境因子综合作用的结果,该阶段并不是引起天童地区微地形上现有植被分布的主要原因。现有植被在地形上的分异极有可能是体现在各树种种子散布的差异性上,或者幼树(sapling)以及小树(small tree)阶段,甚至是大树(adult tree)阶段对土壤、气候等因素不同的适应能力上。更多还原

【Abstract】 Seed germination, seedling emergence and seedling establishment as early stages of forest regeneration are critical in the formation and development of vegetation patterns. Topographical structures induce environmental factors’differences, which determine the seedling establishment and consequent tree growth. Studies on seedling dynamics in various topographical positions are important to explain the role of seedling establishment stage in the formation of vegetation patterns and be critical for understanding small-scale vegetation pattern and regeneration of degraded forests. Based on former vegetation investigations,7 micro-landform dominant tree species were selected, and through indoor seed germination experiment, outdoor direct seeding and seedling monitoring we investigated seed germination, seedling emergence and seedling establishment on various micro-landform units. The role of seedling establishment stage for the formation of present vegetation pattern was discussed, results are:(1) Indoor experiment indicated that 7 kinds of seeds were either dormant or had low continuous germination rates. Water contents of Cyclobalanopsis nubium and Lithocarpus harlandii, Castanopsis fargesii and Choerospondias axiliaris were higher than 30%; water contents of Carpinus viminea, Schima superba and Celtis vandervoetiana were between 10%～20%. Germination rates of Carpinus viminea and Choerospondias axiliaris were 0, and others were lower than 60%. Cyclobalanopsis nubium had the highest germination rate (56.50±7.14%) while Castanopsis fargesii the lowest(6.00±1.42%).(2) There was no significant difference among the micro-landform units and light conditions (p<0.01). Total gap fraction on the upper slope was larger than that of lower slope. Total gap fraction had a trend of increasing with the increase of altitude. Soil erosions were not significantly related with micro-landform units and light conditions (p>0.05).Soil moistures were significantly different among micro-landform units (p<0.001), and not significant between light conditions (p=0.067). Soil moisture was obviously higher than that of lower slope. In each month there was a trend that soil moisture on upper slope was higher than that of lower slope.(3) 7 kinds of seeds had different germination strategies. Carpinus viminea and Schima superba of group A geminated the first, Choerospondias axiliaris and Celtis vandervoetiana of group B the second, and Castanopsis fargesii, Cyclobalanopsis nubium and Lithocarpus harlandii of group A the latest. Schima superba, Carpinus viminea and Celtis vandervoetiana had the largest seedling numbers in April, and had high mortality rates. Choerospondias axiliaris had the largest number in May and June among the micro-landform units and had relatively low mortality rate. Castanopsis fargesii, Cyclobalanopsis nubium and Lithocarpus harlandii reached the largest amounts at the end of the 1st growing season and had high survival rate. (4) Seedling emergence rate was influenced by one or a number of environmental factors, and was not significantly different among the micro-landform units. Seedling emergence was at least correlated with one of the environmental factors, namely soil moisture, total gap fraction and soil erosion, except for Lithocarpus harlandii and Celtis vandervoetiana. Seedling emergence was not significantly different between the light conditions (except for Choerospondias axiliaris on lower hillslope area, P<0.001) and slopes (except for Choerospondias axiliaris under canopy,P=0.048). Seedling emergences of Carpinus viminea and Castanopsis fargesii were not significantly different among the micro-landform units. Seedling emergences of Schima superba, Cyclobalanopsis nubium, Lithocarpus harlandii, Choerospondias axiliaris, and Celtis vandervoetiana had little differences except for some micro-landform units, which indicated that seedling emergences at a micro-landform unit scale were not significantly different.(5) Seedling survival rates and seedling mortality rates varied among species, and were affected by environmental and biological factors. Seedling survival rates of Castanopsis fargesii, Cyclobalanopsis nubium and Lithocarpus harlandii were obviously higher than other species and seedling survival rates of Castanopsis fargesii and Lithocarpus harlandii at some micro-landform units could reach 100%. Carpinus viminea had relatively lower seedling survival rate. Seedling survival rates of all tree seedlings except for Carpinus viminea decreased with the increase of soil moisture. The increase of total gap fraction significantly increased the seedling survival rates of Carpinus viminea, Schima superba, Castanopsis fargesii and Cyclobalanopsis nubium. Seedling survival rates of Carpinus viminea, Schima superba, and Cyclobalanopsis nubium decreased with the increase of soil. Withering was the main cause of mortality of Carpinus viminea, Schima superba and Choerospondias axiliaris. The main cause of Cyclobalanopsis nubium and Lithocarpus harlandii was physical damage.(6) Seedling establishments varied not significantly among the micro-landform units, except for some units which were not correlated with the pattern of the adult trees. These results do not fit the former observed vegetation pattern on various micro-landforms. Seed germination, seedling emergence and seedling establishment of the studied species are the results of the synthesis of seed biological characteristics and environmental factors’influences, and these stages are not the main cause of the present vegetation pattern among the micro-landform units in Tiantong area. The present vegetation distribution differences are likely to vary among the dispersal, sapling, small tree or even big tree stage, which may be related with their different adaptabilities to soil and climate or other factors.更多还原