亚高山云冷杉混交林树木生长释放与干扰分析

对云南碧塔海亚高山云冷杉林内４个样地冠层树木的生长压制和释放的历史,用树木年轮分析方法进行了重建,然后根据生长释放频率推测林冠干扰强度（每１０年冠层树木的死亡百分率）。４个林分（１个中龄林,３个成过熟林）生长释放的平均百分率为４８％～９２％。中龄林内,平均生长释放频率为７１％／１０ａ,成过熟林则为７４％～９５％／１０ａ,在油麦吊云杉〔Ｐｉｃｅａｂｒａｃｈｙｔｙｌａｖａｒ．ｃｏｍｐｌａｎａｔａ（Ｍａｓｔ．）ＣｈｅｎｇｅｘＲｅｈｄ．〕占优势的林分和大果红杉（Ｌａｒｉｘｐｏｔａｎｉｎｉｖａｒ．ｍａｃｒｏｃａｒｐａＬａｗ）油麦吊云杉混交林分内,估测的林冠干扰强度分别为４８％／１０ａ和５９％／１０ａ。     

藏东南亚高山冷杉林林隙特征与干扰状况研究

从林隙的大小结构、干扰频率、形成方式及林隙内形成木的数量特征等几个方面,对藏东南色季拉山亚高冷杉林的典型群落类型－－藓类冷杉林的林隙干扰关况进行了分析。结果表明,在冷杉林中,扩展林隙（EG）和冠空隙（CG）的面积分别占林分总面积的41．73％和14．71％;平均每年有0．82％的林分面积转化为扩展林隙,0．29％的林分面积转化为冠空隙;每年1hm^2面积上约有0．31个林隙形成;林隙的干扰周期为345年,在调查的16个林隙中,共有形成木（GM）78株,平均每个林隙中有4．88株,形成林隙最主要的方式是形成木的折倒,其次为根和枯立,主要外力作用是风,当主林层林木直径达到40－60cm、高度15－20m时,形成林隙的可能性最大;同一林隙常常受到形成木多种死亡方式的影响,且形成时期各不相同,藏东南亚高山杉林林由不同年代的多次干扰而形成。     

岷江冷杉林林窗小气候及其对不同龄级岷江冷杉幼苗生长的影响

对川西亚高山原始岷江冷杉(Abies faxoniana)林林窗内和林冠下小气候及岷江冷杉幼苗生长和生物量进行了两个生长季的连续观测。结果表明:6月林窗内与林冠下太阳辐射的日积累量没有显著性差异,而7~8月的日积累量则有显著性差异。整个生长季节,林窗内太阳辐射的平均积累量为8.10×MJ·m^-2,而林冠下太阳辐射的平均积累量为5.02×MJ·m^-2,两个位点太阳辐射积累量的显著差异主要来自7~8月日积累量的不同;林窗内5和15 cm层土壤的日平均温度比林冠下相应深度分别高2.1和2.7℃,差异显著。林窗内和林冠下3~8年岷江冷杉幼苗高增长率分别为1.2±0.3 cm·a^-1和1.1±0.3 cm·a^-1,差异不显著;9~20年岷江冷杉幼苗高增长率分别为6.2±2.4 cm·a^-1和3.0±0.9 cm·a^-1,差异显著。林窗内岷江冷杉幼苗根、主茎和总生物量与林冠下幼苗根、主茎和总生物量没有显著差异。不同年龄的岷江冷杉幼苗叶和侧枝生物量积累对林窗微环境的响应不同。     

格氏栲林林窗自然干扰规律

通过对格氏栲(Gastanopsis kawakamii)林林窗自然干扰的基本规律的研究,得到了描述林窗干扰状况的一些重要特征。结果表明：格氏栲林中扩展林窗(EG)所占面积比例为34．46％,而实际林窗(CG)所占的面积比例为17．81％,干扰频率每年分别为0．69％和0．36％,林窗干扰返回间隔期为281a;EG的大小变化为63～1257m^2之间,平均为244m^2,而CG的大小变化为22～707m^2之间,平均为126m^2;形成林窗的主要方式是干中折断,比例占36．22％,其次为枯立,比例占32．28形;大多数的林窗是由1～5株形成木形成,3株形成木形成的林窗最多;大多数林窗是在前50a形成的,其中10～40a之前形成的林窗最多;林窗分布格局是均匀分布型的。林窗形成木主要由格氏栲、大叶乌饭(Vaccinium mandarinorum)、山胡椒(Lindera glauca)、狗骨柴(Tricalysia dubi)组成。林窗形成木的地径主要集中在60cm以下,地径20～60cm的主林层乔木形成林窗的比例较大。     

中国东北的云冷杉林

本文从以下几方面对东北地区云冷杉林进行研究．１）环境背景;２）云冷杉林三个主要树种的生态属性;３）以红皮云杉、鱼鳞云杉和臭松为优势种的林分的每一植被类型的树种组成及其结构;４）影响林分的干扰因子;５）中国东北的云冷杉林的主要演替方式和过程．     

银杉(Cathaya argyrophylla)林林窗更新的研究

银杉（Ｃａｔｈａｙａ ａｒｇｙｒｏｐｈｙｌｌａ）在林窗内和非林窗群落内均占有最大的重要值,说明银杉是典型的林窗更新方式．银杉个体在林窗内呈集群分布,林窗边缘往往集中了较多的银杉植株。林窗内银杉直径分布中,出现胸径〉８ｃｍ 及胸径〈３ｃｍ的高峰和３～７ｃｍ的低谷。对最近１０ａ银杉幼树每年高生长量的研究发现,林窗内和荫蔽要完下的结果差异显著,林窗内的幼树高生长快于荫蔽林冠下。     

林窗对岷江冷杉幼苗生存过程的影响

岷江冷杉林是我国西南亚高山暗针叶林的主体之一,其健康的种群动态和更新策略在维持长江上游生态安全方面具有重要意义。为了解岷江冷杉更新过程中林窗对幼苗种群动态的影响,通过调查林窗内和林下岷江冷杉更新幼苗的存活情况,采用数量分析方法研究了幼苗的年龄结构和动态特征。结果表明:林窗内和林下岷江冷杉幼苗的年龄结构金字塔均为两头小中间大的纺锤型,存活曲线均为DeeveyⅡ,生命期望以1龄级的最高、林下种群的高于林窗种群。幼苗的死亡率、消失率、累计死亡率和危险率均随龄级的增加而增大,生存率和死亡密度随龄级的增加而减小;岷江冷杉幼苗种群的数量化动态指数Vpi=0.1059,为增长型种群,在外界随机事件干扰时也可持续增长,尤以林窗种群抵御随机干扰、持续增长的特点更为突出;岷江冷杉幼苗种群的周期波动主要受基波控制,林窗种群在9龄级和11龄级处的波动还受谐波的影响。林窗扩大了岷江冷杉更新幼苗的数量规模、提高了种群抵御外界随机干扰的能力。因此,在岷江冷杉林更新管理中,应高度重视林窗的作用。     

林窗干扰研究

林窗是森林生态系统中一种普遍存在的现象,无论是健康的系统还是已经受到过度干扰的系统,林窗作为森林生态系统发展的重要驱动力,影响着森林的物种组成、结构以及森林的演替方向。因此,林窗研究能够为受干扰森林生态系统的恢复提供理论指导,并为森林生态系统的管理提供科学依据。本文从总结有关林窗的基本理论入手,重点介绍了近年来对林窗概念、基本特征、林窗产生后的生境条件变化以及生物对林窗环境变化的响应等研究概况,并对目前林窗研究的手段以及热点问题进行了总结,以期为今后的相关研究提供参考。     

林窗研究进展

本文从林窗的形成、林窗内微环境特点、林窗内树木更新、以及树轮分析与干扰重建,阐述了国内外在该领域的研究动态和取得的成果,以期推动和促进我国的林窗研究工作。根据欧美学者的研究报告,林窗的面积不仅与林冠和树径的大小成正比,而且与树木的倒伏方式有关;林窗的形成与特征主要受制造林窗树林的种类、树龄、海拔和气候带等因素的影响。林窗内微环境特点随林窗的大小、形状、纬度及所处位置的不同而变化。林窗是推动森林演替和更新的重要因素之一,林窗的形成、大小影响和控制着林内树种的组成和树木的更新。树轮分析可用于检测树木的生长释放,研究表明,在样本数量较大时,树木生长释放对重建过去的森林干扰是很有用的。     

Subcanopy gaps in temperate and tropical forests

Abstract We present a model of gaps in the vertical structure of forest vegetation. The traditional model of a forest gap assumes the existence of a ‘hole’ in the uppermost canopy layer, often extending down to near the ground. The present model extends the concept to gaps at any level, including those in lower layers below an intact canopy or subcanopy. It assumes that gaps at any level represent spaces with unused resources, especially favourable for plant growth and survival. Evidence from temperate and tropical forests indicates that gaps in the subcanopy and understorey layers below intact canopies are common, and that plants have higher growth rates in them than in non-gap sites. We also extend this model to below-ground gaps in the root zone.     

Gap characteristics and gap regeneration in subalpine old-growth coniferous forests,central Japan

Gap characteristics and gap regeneration were studied in three old-growth stands of subalpine coniferous forests in the northern Yatsugatake and the northern Akaishi mountains, central Japan. With the results of the present study and those of a previous study conducted in another locality, general features of gap characteristics and gap regeneration behavior of major tree species in subalpine coniferous forests of central Japan were summarized and discussed. Of the total 237 gaps investigated in the 14.48 ha of forested area, the percentage gap area to surveyed area, gap density and mean gap size were 7.3%, 17.2 ha⁻¹, and 43.3 m², respectively. The gap size distributions were similar among stands and showed a strong positive skewness with a few large and many small gaps; gaps <40m² were most frequent and those >200 m² were rare. Gaps due to the death of multiple canopy trees comprised 44.7% of the total ones. Canopy trees died in various states; standing dead (42.6%) or trunk broken (43.7%) were common and uprooted (12.2%) was an uncommon type of death of canopy trees. These figures indicate that general features of gap characteristics in this forest type are the low proportion of gap area and the high proportions of small gap size and multiple-tree gap formation. In general, shade-tolerantAbies frequently, andTsuga, infrequently, regenerate in gaps from advance regenerations recruited before gap formation, whilePicea and shade-intolerantBetula possibly regenerate in gaps from new individuals recruited after gap formation. Gap successors of conifers occurred in a wide range of gap size and did not show the clear preference to species specific gap size. In old-growth stands without large-scale disturbance (≥0.1 ha in area) of subalpine coniferous forests of central Japan, major tree species may coexist with their different gap-regeneration behaviors and, probably, different life history traits.     

Episodic recruitment of the seedling banks in balsam fir and white spruce

• Premise of the study: In ecosystems where seed production is low and masting years are sporadic, or with species that have short-lived seeds, regeneration is assured by seedling banks rather than seed banks. Seedling establishment and survival play a critical role in determining the composition of these plant communities by supplying new individuals for their maintenance. Seedling emergence and mortality were investigated to test the hypothesis that recruitment into the seedling bank is periodic. • Materials and methods: Seed production and seedling emergence and survival was monitored during 1994-2007 in balsam fir (Abies balsamea) and white spruce (Picea glauca) in four pristine stands of the boreal forest of Quebec, Canada. Measurements were collected twice per month by sampling one permanent plot of 20 × 20 m per stand. • Key results: Seed-rain abundance reached 9 × 10³ seeds m⁻² year⁻¹, and was characterized by synchronous sequences of low and high seed production. New seedlings appeared only during the year following a seed production of at least 1 × 10³ and 1.5 × 10² seeds m⁻² year⁻¹ for balsam fir and white spruce, respectively. Seedlings emerged in July and survived 34-52 d on average, with balsam fir showing a longer lifespan and lower mortality, although 85–99% of seedlings died before completing one year of life. • Conclusions: The emergence of young seedlings was coupled with massive seed rains, which allowed synchronous replenishment of the seedling banks among stands and species, and generated different cohorts, yielding a discontinuous age structure.     

大熊猫栖息地亚高山针叶林结构和动态特征

亚高山针叶林是大熊猫适宜的栖息环境 ,其结构和动态规律严重影响大熊猫的生存和繁衍及其进化潜力的维持 ,是恢复退化大熊猫栖息地的唯一科学依据。通过样方法和中心点四分法调查了大熊猫栖息地 4个亚高山针叶林样地和该样地所在森林的 6 2个林窗 ,研究了该类森林的结构及其更新与大熊猫主食竹生长、林窗干扰的关系 ,以期揭示亚高山针叶林的动态规律 ,为大熊猫栖息地的恢复提供科学依据。研究结果表明 :岷江冷杉 Abies faxoniana和紫果云杉 Picea purpurea是亚高山针叶林的主体 ,其所构成的森林是大熊猫重要的栖息环境。岷江冷杉种群年龄呈现连续分布格局 ,而紫果云杉种群年龄呈间歇性分布 ,其在 2 5 0～ 5 0 0 a之间没有更新。该类森林中普遍存在着林窗干扰和更新现象 ,90 %的林窗下分布有岷江冷杉和紫果云杉更新的幼苗、幼树和大树。但林窗内不同树种更新密度不同 :岷江冷杉更新幼苗、幼树和大树占所有更新树种的 82 .5 % ,而紫果云杉和糙皮桦的更新幼苗、幼树和大树占 11.3%。岷江冷杉和紫果云杉的更新同时受林下大熊猫主食竹生长状况的影响 :主食竹盖度高 ,更新树种幼苗、幼树的密度低 ,即主食竹的生长抑制了岷江冷杉和紫果云杉的更新。     

小径竹对亚高山暗针叶林优势 树种林窗更新的影响

在亚高山岷江冷杉林中选取面积≤50m2,50~150m2,>150m2的林窗,每种类型内均包含3种小径竹盖度(≤20%、20%~50%、>50%),共调查林窗9个,并调查包含这3种小径竹盖度的三块林下对照样地,研究了该类森林林窗更新与小径竹生长的关系。结果表明:(1)无论林窗大小,林窗内的更新幼苗数量都比林下的多,林窗更新是岷江冷杉群落更新的主要途径;(2)所选林窗均为发育早期,林窗对更新树种的种类组成和数量的影响主要表现在幼苗上。糙皮桦幼树及幼苗数量随林窗面积的增加而急速增加,它的更新更需要较大的林窗;(3)不同小径竹盖度下幼苗的密度呈现显著性变化,小径竹的生长明显抑制了森林幼苗的更新及填充的进程;(4)华西箭竹的分散程度随林窗面积的增大而降低,而平均高度和基径则有增加的趋势。     

Variations in bark acidity and conductivity over the trunk length of silver fir and Norway spruce

 Before using bark to determine the degree of acidity in the environment due to atmospheric pollution, a better understanding of the internal factors which are involved in the evolution of the physico-chemical characteristics of bark is necessary. In this paper, variation of acidity and bark conductivity over the trunk length of silver fir and Norway spruce are examined. First, we show that it is more accurate to measure average bark pH and conductivity in each 2 m section of a tree by starting at the top than by starting at the base of the tree. A positive pH and conductivity gradient is observed over the trunk length; bark thickness decreases towards the top of the trunk. In the upper part of both silver fir and Norway spruce there are good correlations between acidity, conductivity, bark thickness and height, but in the lower part of the trees, silver fir and Norway spruce show contradictory behaviour. In silver fir, pH is linked with bark thickness and distance from the ground, while conductivity is not correlated with these two criteria. In Norway spruce we observe opposite results. It appears that conductivity measured on the external part of bark is directly influenced by the proximity of internal tissues, which are rich in ions, while acidity depends on the length of exposure to leaching due to water flowing down the trunk. Received: 15 June 1993/Accepted: 30 January 1995     

Spatial and temporal variation in historic fire regimes in subalpine forests across the Colorado Front Range in Rocky Mountain National Park, Colorado, USA

Aim The historical variability of fire regimes must be understood in the context of drivers of the occurrence of fire operating at a range of spatial scales from local site conditions to broad‐scale climatic variation. In the present study we examine fire history and variations in the fire regime at multiple spatial and temporal scales for subalpine forests of Engelmann spruce–subalpine fir (Picea engelmannii, Abies lasiocarpa) and lodgepole pine (Pinus contorta) of the southern Rocky Mountains. Location The study area is the subalpine zone of spruce–fir and lodgepole pine forests in the southern sector of Rocky Mountain National Park (ROMO), Colorado, USA, which straddles the continental divide of the northern Colorado Front Range (40°20′ N and 105°40′ W). Methods We used a combination of dendroecological and Geographic Information System methods to reconstruct fire history, including fire year, severity and extent at the forest patch level, for c. 30,000 ha of subalpine forest. We aggregated fire history information at appropriate spatial scales to test for drivers of the fire regime at local, meso, and regional scales. Results The fire histories covered c. 30,000 ha of forest and were based on a total of 676 partial cross‐sections of fire‐scarred trees and 6152 tree‐core age samples. The subalpine forest fire regime of ROMO is dominated by infrequent, extensive, stand‐replacing fire events, whereas surface fires affected only 1–3% of the forested area. Main conclusions Local‐scale influences on fire regimes are reflected by differences in the relative proportions of stands of different ages between the lodgepole pine and spruce–fir forest types. Lodgepole pine stands all originated following fires in the last 400 years; in contrast, large areas of spruce–fir forests consisted of stands not affected by fire in the past 400 years. Meso‐scale influences on fire regimes are reflected by fewer but larger fires on the west vs. east side of the continental divide. These differences appear to be explained by less frequent and severe drought on the west side, and by the spread of fires from lower‐elevation mixed‐conifer montane forests on the east side. Regional‐scale climatic variation is the primary driver of infrequent, large fire events, but its effects are modulated by local‐ and meso‐scale abiotic and biotic factors. The low incidence of fire during the period of fire‐suppression policy in the twentieth century is not unique in comparison with the previous 300 years of fire history. There is no evidence that fire suppression has resulted in either the fire regime or current forest conditions being outside their historic ranges of variability during the past 400 years. Furthermore, in the context of fuel treatments to reduce fire hazard, regardless of restoration goals, the association of extremely large and severe fires with infrequent and exceptional drought calls into question the future effectiveness of tree thinning to mitigate fire hazard in the subalpine zone.     

Changes in carbon,nitrogen and phosphorus stoichiometry in decaying logs with gap positions in a subalpine forest

亚高山森林倒木碳氮磷化学计量特征随林窗位置的变化 森林林窗对太阳辐射和降水(主要是降雨和降雪)的再分配可造成林窗内外微环境条件的异质性。本研究旨在通过改变微环境,测试林窗对倒木碳(C)、氮(N)和磷(P)化学计量比的影响。在青藏高原东部的亚高山森林中,将I–V腐解等级的岷江冷杉(Abies faxoniana)倒木分别置于林窗中心(GC)、林窗边缘(GE)和郁闭林下(CC)进行原位培养,分别于2013–2016年8月测定了腐烂树皮、边材和心材的C、N、P含量。研究结果表明,树皮N浓度从CC到GC呈下降趋势,而边材和心材则表现出相反的趋势。此外,边材和心材IV、V腐解等级的C/N从CC到GC呈下降趋势,心材V腐解等级的 N/P从CC到GC呈增加趋势,这表明森林林窗对高度腐解等级倒木的C/N/P化学计量比有强烈影响。简而言之,高度腐烂的倒木更容易受到微环境的影响,必要时应适当调整郁闭林下或林窗中心的高度腐烂的倒木比例。