【作者】 白登忠；

【导师】 肖文发；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2012， 博士

【摘要】 林线作为郁闭森林和高山草甸之间的生态过渡带，对自然环境因子变化和人为干扰异常敏感。目前，虽然热量（温度)控制、环境胁迫、生长受限、繁殖更新障碍、碳平衡失调等假说能解释一定地域的高山林线现象，但并不能作为普遍适应的林线理论。本论文通过对祁连山阴坡建群种青海云杉林线自然更新和人工更新研究，探索影响祁连山林线更新的主要因素，以及人工更新对林线位移的影响和气候变暖条件下林线的变化趋势。本论文主要研究了祁连山地区近50年来的气候变化、西水林区不同海拔的青海云杉幼苗更新、树年轮和枝条生长，以及在林线海拔以上青海云杉播种试验和幼苗移栽，分析了青海云杉林线树木生长、更新的影响因素，主要研究结果如下：1.祁连山西水林区周边气象台站气象资料分析显示，52年来该地区年均温升高显著；降水略有增加，全年降水主要分布在5、6、7、8、9月份，占到全年降雨量的82%。实验区不同海拔5或6月份-10月份大气温度和土壤温度都在0℃以上，大气和土壤温度都随着海拔升高而降低，每升高100m温度降低0.44℃左右。林线海拔3300m最热月平均温度13.60℃高于全球林线海拔最热月平均温度10℃，林线根际温度6.22℃与全球林线根际温度6.7±0.80℃相同。2.土壤有机质、全氮、速效磷和速效钾含量随着土层加深而减小；pH值随着土层加深而增大；全磷含量在各土层中变异性较小。有机质和全氮含量随着海拔升高而降低，全钾含量和pH值随着海拔的升高而减小；而速效磷和速效钾含量随着海拔的升高没有明显的规律。3.随着海拔升高，青海云杉的生长表现为从水分制约向热量制约转变的趋势。低海拔处的青海云杉年生长量较高海拔处大。水分是下限林线青海云杉的制约因子，而随着海拔的升高热量条件逐渐成为主要的制约因子。生长季的秋季结束时间对青海云杉的生长制约较大。4.海拔2900m和3000m的青海云杉种群林木生长呈现近倒“J”型结构，种群林木生长处于稳定状态；海拔3100m的种群发展呈现线性结构，种群开始出现衰退的现象；海拔3200m和3300m种群林木生长较年轻旺盛，无衰老的苗木出现，3200m处为波浪形变化，说明此海拔区段青海云杉种群发展波动较大。5.随着海拔梯度的增加，青海云杉林更新幼苗数量呈现逐渐降低的趋势，海拔3200m以下的更新幼苗以中低高度级（<25cm、25～55cm、>105cm）为主，且海拔越低幼苗数量越多，85～105cm高度级的幼苗缺少，而海拔3300m各高度级幼苗数量相差不大且更新情况较差，甚至某些高度的幼苗缺失。6.随着海拔的升高，更新幼苗的分布格局由随机分布向集群分布变化。海拔2900m，＜25cm的幼苗仅为弱聚集性，表现为随机分布；85cm～105cm的幼苗为均匀分布；在海拔3000m上，85cm～105cm和＞105cm两个高度级的幼苗表现为随机分布；3100m，3200m和3300m三个高海拔内，幼苗均呈现集群分布。不同海拔高度<25cm的幼苗的生长主要与海拔梯度、土壤含水量、有机质、总地表覆盖度、活地被物盖度存在显著正相关，而与全钾、大气温度显著负相关；影响25cm～55cm和55～85cm的幼苗与土壤pH值、大气温度、全钾呈正相关，与有机质、活地被物盖度、总地表覆盖度呈负相关；影响85cm～105cm和﹥105cm的幼苗与大气温度、乔木层郁闭度、全钾呈正相关，与土壤pH值、土壤含水量、海拔梯度呈负相关。7.从林线3300m到海拔3500m，播种试验发现，青海云杉种子均可发芽，并随海拔升高，发芽率降低，但无法越冬，而5年左右生青海云杉幼苗移栽，从3300到3700m均能成活，表明在祁连山高海拔地区种子发芽和幼苗成活是限制林线更新的一个重要环节。随着海拔的升高，人工更新幼苗生长越来越慢，长势变差，死亡率升高，海拔对幼苗生长影响明显。高海拔低温可能是限制种子发芽和幼苗成活的关键因素。8.随海拔升高青海云杉叶片组织中NSC含量持续增加状态，随海拔升高温度降低青海云杉的的生长并未受到碳限制。在气候变暖条件下，随着高海拔地区温度升高，祁连山青海云杉生长加快，低温对青海云杉种子发芽和幼苗成活的限制影响减小，有利于林线向高海拔扩展。更多还原

【Abstract】 Timberline, as the ecotone between alpine vegetations and subalpine vegetations ofmountains, is sensitive to the environment change and human disturbance. There is nouniversal theory of the timberline, although the hypothesis, such as energy(temperature)controling, environmental stress, growth limitation, reproductive disorder and carbonimbalance, could partially explain the dynamics of the timberlines in limited regions. Thenatural and man-made regeneration of Picea crassifolia at timeberline in the Qilian montainswas investigated in the dissertation to (a) understand the main impact factors of reproductivity,(b) reveal the influence of artificial regeneration on the moving of timberline,(c) study thechange trend of timberline under climate warming.The thesis mainly study the climate change in the past fifty years of Qilian montains, theseedling regeneration, growth of tree-ring and shoot of adult trees of Picea crassifolia in theXishui forest region, seeding and transplanting of seedling of Picea crassifolia over timberline,and analyses the influence elements of the growth and regeneration of Picea crassifolia. Themajor achievements of this study are summaried as follows:1. According to the analysis on temperature information of Xishui forest region, theannual average temperature increased significantly in the past fifty-two years, and the annualaverage precipitationis also increased slightly, where82%of rainfall in total year isconcentrated from May to Septermber. The atmospheric and soil temperature in differentelevations are above0℃from May or June to October and decreses0.44℃with the increasingof elevation in per100m. The temperature in warmest month in the timberline is13.60℃thatis higher than the globle mean temperature at timberline(10℃). The soil temperature in thetimberline is6.22℃that is similar with the globle soil temperature (6.7±0.80℃).2. The content of organic matters, total nitrogen, rapid available phosphorus and rapidavailable potassium decreased with the increase of soil depth, while the pH value increased with the increase of soil depth, and the total phosphorus contents didn’t show significantvariation with different soil depth. The content of organic matters and total nitrogen decreasedwith the increase of elevation, while the content of total potassium and pH value decreasedwith the increase of elevation, and the content of rapid available phosphorus and potassiumdidn’t show significant variation with different elevation.3. The growth limitation of Picea crassifolia varied from water to thermal with theincrease of elevation. The annual growth of Picea crassifolia at the lower elevation was biggerthan that in the higher elevation. Water was the limite factor for Picea crassifolia at the lowestelevation while thermal condition became the limite factor for it with the increase of elevation.The ending of growth time in the autum had great influence on the growth of Picea crassifolia.4. The growth of tree populations at the elevation of2900m and3000m was in stablestatus, which looks like the reverse “J”; the tree populations at the elevation of3100m began todecrease linearly; the tree at the elevation of3200m to3300m were vigorous with no died trees,and the tree populations at the elevation of3200m was waved, which indicated that thedevelopment of the Picea crassifolia population was in large change.5. The quantity of the regenerated seedlings decreased with the rising of elevation. In theregion lower than the elevation of3200m, the seedlings was of middle or low height (<25cm,25~55cm,>105cm). And the lower the elevation was, the more short seedlings there was. Theseedlings of the height between85and105cm was rare. In the region of the elevation of3300m, the quantity of seedlings of different height was similar, and the regeneration there wasnot good, where did not exsit seedlings of separate height.6. The regenerated seedlings varied from random distrbution to cluster by the rising ofelevation. At the elvation of2900m, the aggregation of the seedlings those height was below25cm distributed randomly, and the height of85~105cm distributed evenly; At the elvation of3000m, the aggregation of the seedlings of height in85~105cm and upper than105cmdistributed randomly; At the elvation of3100m,3200mm and3300mm, the aggregation of theseedlings showed cluster distrbution. The growth of seedlings those height was below25cmsignificantly correlated positively to the coefficient of the varation of rapid available potassium, coverage of dead litter, transmittance of arbor, the coverage of shrub, soil moisture content andthe total ground cover were bigger and negtively to the total potassium and the atmospherictemperature. The growth of seedlings of height in25cm～55cm and55～85cm positivelycorrelated to soil PH, atmospheric temperature and total potassium, and negatively to theorganic matters, coverage of ground vegetation and total ground coverage. The growth ofseedlings of height in85cm～105cm and upper than105cm positively correlated toatmospheric temperature, tree layer crown density and total potassium, and negatively to thesoil PH, soil moisture content and altitudinal gradients.7. The articicial seedling experiments of Picea crassifolia in forest line altitude fromelevation of3300to3500m showed that the seedlings could germinate but can’t survival inwinter, and the higher the elevation was, the lower the germination ration was. Howere,five-years old transplanted Picea crassifolia seedling could survive from3300to3700m whichindicated that seed germination and seedling survival were important aspects that limited theupdation of timberline. The higher the elevation was, the slower the growth of the artificialregenerated seedlings was, the worse the growth was, and the higher the death rate was, whichindicated that the growth of the seedlings was significantly affected by elevation. The lowertemperature at high elevation might be the key factor that limited seed germination andseedling survival.8. The NSC content of leaves of Picea crassifolia exhibited a sustained increase by theincrease of the elevation. The growth was not affected by the carbon content as the risingelevation and decreasing temperature.Under the global warming, with the increase of temperature in the rigion of high elevation,the growth of Picea crassifolia speed up, the influence of lower temperature at timberline onthe seed germination and seedling survival of Picea crassifolia could be reduced, which wasgood for the expansion of timberline to the higher elevation.更多还原