【作者】 王妍；

【导师】 卢琦；

【作者基本信息】 中国林业科学研究院 ， 水土保持与荒漠化防治， 2009， 博士

【摘要】 沙地樟子松(Pinus sylvestris L. var. mongolica Litv.)天然分布在呼伦贝尔高原东部、海拉尔河中游及支流伊敏河、辉河流域和哈拉哈河上游一带的固定沙地上,具有抗寒、抗旱、耐贫瘠等优良特性,天然更新能力强,防风固沙作用显著。沙地樟子松在沙地上持续进行的天然更新对退化生态系统的植被恢复与重建,沙地生态系统各种效益的持续发挥,以及我国北方绿色生态屏障的建立都具有重要意义。进入21世纪以来,在全球变化背景和人为因素共同作用下,沙地樟子松的天然更新状况受到严重干扰,樟子松林天然更新的面积和速度明显减慢,有些地区甚至出现面积减少的趋势。因此,探析影响沙地樟子松天然更新的主导因素,寻求有效措施保证和促进其天然更新,使沙地樟子松林能够长期稳定发展,从而发挥出更大的生态作用,是广大林业工作者普遍关心的问题。本研究以森林培育学、种群生态学、地统计学和多元统计学等多学科的基础理论为依据,从沙地樟子松更新格局变化和年龄组成结构变化的角度,通过多种观测手段,解析呼伦贝尔沙地樟子松的天然更新过程,提出主导樟子松林天然更新过程的因素,阐明樟子松在林缘和林隙中的更新模式,并比较现有人工促进措施在植被自然修复过程中的作用,以期为该地区植被恢复、生态系统保护以及荒漠化防治等提供科学依据和技术支撑。主要研究结果包括以下5方面:(1)沙地樟子松种子更新可分成3个阶段和4个时期。3个阶段包括:母树、种子和幼苗;4个时期包括:母树的种子结实与生产、种实扩散、种子萌发和幼树生长。其中种实扩散过程包括第一扩散过程,即种子从植株到靠近植株的地面的运动过程;第二扩散过程,即水平(地面~地面)和垂直(地表~土壤)的种子再运动过程。对沙地樟子松更新的不同时期进行研究发现,樟子松母树约在20龄左右开始结实,丰年间隔期为3 ~ 4年,150 ~ 200龄的老龄木结实仍很频繁。在郁闭度为0.5 ~ 0.6的林分中,平均每公顷结实的林木株数约为230株,可采集球果约358 kg,除去30%的虫害和空粒外,可产纯种子约3.6 kg。在种实第一扩散过程中,受风向和重力的双重影响,种子多散布在母树周边0 ~ 8m距离内,且随与母树距离的增加种子数量逐渐减少,母树东、北向种子的数量明显高于西、南向。在种实第二扩散过程中,土壤种子库中完好种子的水平和垂直分布特征明显。在垂直分布上,种子大都分布在5 cm以上的土层和枯枝落叶层中,尤其以枯枝落叶层中种子分布较多;在水平分布上,种子密度呈抛物线形,在距母树约3 ~ 5 m处区域出现种子密度峰值,随与母树距离的增加,种子密度逐渐减少。在幼树生长过程中,沙地樟子松更新苗主要分布在母树周边,且集群分布在母树下北偏东方向的扇形区域内,随扇形区域向母树靠近,更新苗龄级增加。(2)对沙地樟子松林分中的更新苗种群进行调查发现,樟子松的更新苗种群是稳定型增长种群,种群中幼龄林所占的比例较大,林分年龄结构呈平稳增长的趋势。在莫和尔图地区平均每hm2樟子松天然林中约有1 ~ 30龄的更新苗2.30×104株,且随林分郁闭度的增加,更新苗密度呈减少趋势,疏林中樟子松更新苗的密度最大。(3)林隙更新是沙地樟子松重要的天然更新方式之一,林隙大小与更新状况关系密切。当林隙面积较小时(<1 hm2),林隙内的天然更新受周边母树的影响较大,表现为母树单株的更新特征,更新状况取决于周边母树;当林隙面积在4hm 2> t > 1hm2之间时,林隙的存在有利于更新苗的生长,对更新有利;当林隙面积较大时( t > 4hm2),除林隙边缘对更新产生影响外,林隙在沙地樟子松更新中的影响随面积增大而减弱,林隙效应逐渐消失。在沙地樟子松林分林隙内部,林隙西缘和南缘的更新状况明显好于东缘和北缘,形成了林隙西南方向的扩展速度高于东北方向的现象。一般来讲,在不计林隙面积的前提下,林隙南缘更新苗自南向北的扩展距离最远在100 ~ 125 m,而自北向南扩展的距离在25 ~ 50 m;林隙西缘更新苗自西向东的扩展距离最远在150 m左右,而自东向西扩展的最远距离在75 m左右。(4)沙地樟子松林分林缘区域有利于更新苗的生长,更新状况较好。更新苗在靠近林缘处呈为集群分布的格局,表现出明显的边缘效应,而随与边缘距离的增加,边缘强度减弱,更新苗表现为随机分布的格局。东北林缘和北林缘更新苗状况好于西林缘和南林缘,且北林缘处更新苗向外扩展的距离显著高于其他方向。研究还发现,与凸型和直线型林缘相比,凹型林缘拥有更有利于沙地樟子松更新和生长的优越条件,因此,凹型林缘外沙地樟子松更新带较长,生长状况较好,入侵扩展的速度也较快。更多还原

【Abstract】 Mongol Scotch Pine distributes in the fixed sandyland at the east of Hulunbeier plateau and watershed which formed by Hailar River,Yimin River and Halakhah Rivernatively. It has good adaptability to cold, drought and barren environment, and a prominent advantage to wind control and shifting sand fixed with the notable regeneration ability. The natural regeneration process of Mongol Scotch Pine in the sandyland is important to vegetation rehabilitation and reconstruction of degraded ecosystems, sandy ecosystem benefit sustaining development, as well as the establishment of green ecological barriers in north of China. Since the 21st century, under the context of global change, the natural regeneration of Mongol Scotch Pine has been disturbed seriously. The expansion scale and speed has been slow down, and the trend in some areas has been adverse. Therefore, exploring the impact factors of natural regeneration, taking effective measures to ensure and promote the natural regeneration and making sure the long-term stable development to play a greater ecological benefit, which have been concerned by the forestry staffs.The natural regeneration process and character of Mongol Scotch Pine have been studied from the age pattern and spatial structural changes based on the multi-disciplinary theories and methodologies, including silviculture, population ecology, geo-statistics and multi-statistics in this study. By all kinds of observation means, the main impact factors in natural regeneration process, the regeneration model in forest edge and gap, the role of different artificially vegetation rehabilitation means were discussed and summarized to provide the scientific basises and technological supports to ecosystem protection and desertification combating. The main findings were as the following:Mature trees of Mongol Scotch Pine seed in twenty years old nearly, and the abundant year will be iterated in every 3 to 4 years. Mature trees of 150 ~ 200 years old still seed frequently. In the forest stands of canopy density is 0.5 ~ 0.6, the average amount of seeding-tree will be 230 per hm2, the cones collected will be 358 kg, the seeds produced will be 3.6 kg which 30% of the pest and empty seeds have been removed. Seeds of spread nearby the mature tree in the distance of 0 ~ 8m, and the density of seeds will decrease with the distance increase from the mature trees. The seeds density in east and north is significantly higher than that of in the west and south. Vertical distribution of soil seed banks is very distinct, and most of seeds lie in the surface litter layer more than soil. The seed density of level distribution in soil seed banks is highest in less than 3m from the observed tree. The seeding clusters near the observed tree in a fan-shaped region composed in the north east direction.The seedling population is stable growth type, which the proportion of young growth stocks is larger than the others, and the stand age structure shows as the steady growth trend. In research area, there are 2.30×104 seedlings in per hm2 natural forest and the density decrease with the forest canopy density increase, seedling density is largest in sparse stand.The relationship between the gap area and seeding density is quadratic curve function which means the seeding density increase with the area and then decrease. The natural regeneration status in west margin of gap is better than the eastern margin and it significantly better in the southern than the northern, which formed the south-west gap significantly better than in the northeast, eventually leading to south-west gap extension faster than the northeast. Generally speaking, the largest seeding spread distance from south to north is close to 100 ~ 125m, from north to south is 25 ~ 50 m, and the largest seeding spread distance from west to east is close to 150m, from east to west is nearly 75 m.The forest edge region is conducive to the growth of seedlings, which show as a greater seedlings density and better natural regeneration status. The seeding near the forest edge was the cluster distribution pattern, and with away from the edge, the seeding is in random distribution pattern. The seeding density in forest edge of north-east and north were significantly higher than that in the west and south, and the expansion distance in north forest edge was significantly higher than other directions. Compared with convex and linear forest edge, the concave edge has a greater natural regeneration status and more favorable conditions, which showed with a long spread distance, and a faster expand invasion to pasture.更多还原