极端降雨对辽东山区次生林土壤侵蚀与树木倒伏的影响

为了解次生林生态系统在极端降雨后的受灾情况,于2010年7-8月极端降雨后,对中国科学院沈阳应用生态研究所清原森林生态实验站内、不同立地次生林生态系统及无林地进行了全面调查与分析.结果表明:极端降雨对次生生态系统土壤产生了强烈的侵蚀,并造成树木的大量倒伏,同时诱发多处坡面型泥石流;受灾严重区多分布于坡度陡、高差大的林分;侵蚀沟和泥石流的数量与灌木盖度呈显著负相关;凋落物层对土壤侵蚀具有一定的抑制作用;不同树种倒木数量表现不同,其中水曲柳、桦树和落叶松的倒木数量较多;与有林地相比,无林地受灾程度更为严重.基于上述结果,讨论了极端降雨干扰对次生林生态系统结构、立地条件及演替模式等可能造成的影响.     

干扰对辽东山区次生林植物多样性的影响

依据林分距离居民区和一、二级道路的远近以及郁闭度与受害乔木株数百分比,将人为干扰和自然干扰各划分为低度干扰、中度干扰和高度干扰3个水平.在此基础上,调查分析了干扰对辽东山区次生林植物多样性的影响,初步探讨了人为干扰和自然干扰影响的差异.结果表明,在不考虑次生林类型的前提下,受中度水平人为干扰的次生林总体多样性高于其它两个水平,从低水平干扰到高水平干扰的Simpson 指数分别为0.95、0.96和0.92,Shannon-Wiener指数分别为3.60、3.77和3.36;乔木层多样性有随干扰水平提高而增加的趋势,灌木层和草本层的变化趋势与总体多样性相似;各次生林类型总体多样性随干扰水平的变化存在差异,且乔木层、灌木层和草本层的多样性变化在各次生林类型中未呈一致的趋势,其中灌木层和草本层受干扰影响较大;自然(雪/风)干扰发生近3年后,受到不同程度影响的桦木林总体多样性差异不大, Simpson 指数分别为0.91、0.91和0.92,Shannon-Wiener指数分别为2.30、2.93和2.89;随着干扰水平提高,乔木层和灌木层多样性呈增加趋势,草本层多样性则变化不大.     

森林的风/雪灾害研究综述

风／雪灾害不仪极大影响木材生产,同时对森林生态系统的稳定性也造成很大影响。森林风／雪危害的主要类型有树干弯曲、干(冠)折、掘根以及后续危害等;其发生主要依赖于气象条件、立地因子、树木和林分特征及其之间的相互作用。其中．林木尖削度(胸径／树高)和林分结构特征(树种、组成、密度等)是控制树木和林分对风／雪荷载抵抗的主要特征量。因此．通过造林、调整林分结构．加强林分管理如间伐、施肥等措施一直是用来减少林木的风／雪灾害的主要措施。另外．林木或林分发生风／雪害的模型分析研究也取得了很大进展,但由于森林风／雪害受诸如地形、天气等多种因素影响、目前所建立的模型系统在实际应用中普适性较芹。通过综述以往研究结果认为：在气象和立地条件难以控制的情况下．通过改变可控因子林分结构来减少森林风／雪害是可行的。因此．研究如何加强森林经营管理,尤其是不同形式的间伐技术和不同处理的造林措施与风／雪灾害发生的关系、如何增加林木和林分抵抗风／雪灾害的能力等是今后该研究领域的重点和难点。与此同时．应加强风／雪灾害危险率评估研究．进而对森林进行风／雪灾害危险率管理;并注重对受灾前后林地内生态效应的研究,以便为灾后的森林经营管理和调控提供坚实的理论依据。     

基于物种多样性和空间格局的林分稀疏

为了解影响热带天然次生林稀疏的因素,本研究应用地上生物量模型、多样性指数和O-ring统计对固定样地中植物的地上生物量、物种多样性和空间分布格局进行定量研究,并结合Yoda自疏模型计算林分稀疏指数,分析物种多样性与空间格局对林分稀疏的影响。结果表明:林分地上生物量随着林分密度的减小呈现先增大,后减小,再增大的趋势,在径级Ⅲ或径级Ⅳ处,出现变化拐点,在天然林管理时应加以注意。多样性指数与林分稀疏指数总体上无显著的相关性,但中等多样性指数值却对应最大的稀疏指数。说明物种多样性中等情况下,林分稀疏最为强烈。植物个体聚集分布的最大强度与稀疏指数呈显著线性负相关,二者的回归方程为:α=-1.7873O11(r)max+2.3451(R2=0.798,P=0.003)。结果表明,在热带常绿季雨矮林中,过大的聚集强度不但不能促进稀疏过程的进行,反而会对其产生阻碍作用。     

雪灾对鲁南地区侧柏林的影响

以山东省枣庄市抱犊崮林场侧柏人工林为研究对象,采用典型抽样方法调查了特大雪灾后林木的受灾程度,探讨了坡向、海拔和林分结构特征对受灾程度的影响,以期为人工林雪灾预防提供理论依据。结果表明:侧柏林受灾程度极显著受到坡向和海拔的影响;从坡向看,阳坡受灾程度比阴坡严重;从海拔上看,阳坡高海拔地区比低海拔地区雪害情况严重,但阴坡不同海拔之间雪灾没有显著差异;从林分结构看,阳坡6~18 cm径阶的林木受损情况较严重,而阴坡不同胸径的林木受灾程度无显著差异。相关分析表明,受灾程度与树高呈显著负相关(除阴坡海拔296 m),但与其他林分结构指标的相关性随坡向和海拔的变化而变化。因此,立地条件与林分结构的共同作用是影响该地区侧柏林受灾的主要因素。     

木荷次生林林木更新与土壤特征的相关性

以湖南省青石冈林场木荷次生林为研究对象,在测定其土壤特征基础上,分析了林木天然更新指数和土壤理化性质的相关性。结果表明:1)8种林分更新状况有差异,更新状况由差到好的排序为:S-CP(0.46)S-DC(0.52)S-CD(0.64)S-CL(0.68)S-CM(0.69)S-CQ(0.69)S-PC(0.74)S-CP(0.88),其中与针叶树种混交的林分更新效果好。2)酸性环境更有利于林分的更新,且林地养分含量越高林分更新效果越好,有机碳、全N以及全P的含量高的林分更新指数明显大于其含量低的林分,土壤pH值、容重与更新指数变化规律相反,全K的含量与更新指数没有明显联系。3)林木更新指数与土壤容重呈显著性负相关关系(r=-0.86**),与土壤含水量(r=0.93**)、有机碳(r=0.90**)、全N(r=0.88**)、水解性氮(r=0.83*)和全P(r=0.78*)呈显著正相关关系,相关性依次减弱,且相关性在不同林分有一定差异,更新状况属于中等水平的林分相关性强,且15—45cm土层土壤理化性质与更新指数的相关性最强;经主成分分析发现,在众多影响林分天然更新的土壤特性当中,含水量、有机碳和全N决定该地区木荷次生林更新的关键因素。研究的结果为森林可持续利用以及木荷次生林的恢复和管理提供科学依据。     

次生林概念与生态干扰度

近一个世纪强烈的人为干扰使世界范围内的原始林面积锐减,次生林已成为中国乃至世界森林资源的主体.虽然在文献与现实中"次生林（Secondary forest）"被广泛使用,但次生林的概念在各个国家,甚至同一国家或地区以及各种不同文献中存在相互矛盾的情况,这给次生林研究与经营实践带来诸多不便;而不准确的次生林定义也为与各个层次的决策制定者及公众之间的交流带来了障碍.本文在查阅大量国内外关于次生林概念文献的基础上,结合近年来关于次生林生态与经营研究实践,综合分析了次生林概念的不确定性,同意以往次生林定义中的基本内涵,并认为：次生林是由于人为破坏性干扰或异常自然干扰使原始林固有的林分结构、物种组成或基本功能发生了显著变化,经过天然更新或人工诱导天然更新恢复形成的林分.但该定义中仍存在着很多不确定性, 如:怎样的干扰为"人为破坏性干扰"和"异常自然干扰";"林分结构、物种组成或基本功能"发生了怎样的变化为"显著变化";"人工诱导天然更新"中"人工"参与的成分比例如何等.次生林概念是在20世纪初由植物演替学家提出,当时未考虑干扰的持续性;而实际上,无论是次生林还是原始林,均是森林生态系统演替过程中的某一状态,在现代森林生态系统研究中,应重新规范"次生林"的概念.考虑到"次生林"定义的不确定性或困难性,建议使用"森林自然度"或"森林生态系统成熟度"或"森林干扰度"来表达现实森林所处的状态,但该方面的研究与实践尚需加强.     

林分结构对湖南栎类天然次生林林下植被生物量的影响

对湖南栎类天然次生林不同林分类型的林下植被生物量特征及其影响因素进行研究。结果表明: 将50块样地划分为甜槠-鹿角杜鹃混交林、亮叶水青冈-箭竹混交林、石栎-虎刺+山茶混交林、甜储+枹栎-鹿角杜鹃混交林、青冈栎-油茶+杜鹃混交林5种林分类型。5种林分的林下植被生物量均较低,不超过2.3 t·hm^-2。5种林分类型的林下灌木生物量没有显著差异,甜槠-鹿角杜鹃混交林草本层生物量显著低于其他4种林分类型。影响不同林分林下植被生物量的因素不同。在甜槠-鹿角杜鹃混交林,草本层生物量与郁闭度、角尺度呈显著负相关,林下植被总体生物量与开敞度呈显著正相关;在亮叶水青冈-箭竹混交林,灌木层生物量与林分的角尺度、郁闭度呈显著负相关,草本层生物量与林下植被总体生物量与混交度呈显著正相关;在石栎-虎刺+山茶混交林,草本层生物量与林分的聚集指数呈显著正相关;在甜储+枹栎-鹿角杜鹃混交林,灌木层生物量与林分的混交度呈显著负相关,草本层生物量与林分的株数密度呈显著正相关;而在青冈栎-油茶+杜鹃混交林,林分结构与林下生物量没有显著相关关系。对林下植被生物量进行调整,应该以调整林分水平分布格局为主,综合考虑林分遮盖程度与树种结构。     

帽儿山天然次生林内主要木本植物空间格局及更新特点

基于帽儿山次生林1 hm²样地的调查数据,将林分分为幼苗(树高H<30 cm)、幼树(H在30～130 cm或H>130 cm同时胸径DBH<5 cm)、中树(DBH 5～10 cm)、大树(DBH≥10 cm)4个大小级,运用O-ring点格局分析方法,分析帽儿山地区次生林内主要木本植物整体及树种人工补植红松、三大硬阔(水曲柳、胡桃楸、黄菠萝),以及榆树的各大小级空间格局及其关联性,探讨该地区次生林更新演替动向,为该地区森林的可持续经营提供依据.结果表明: 样地内更新幼苗2894株·hm^-2,幼树3337株·hm^-2,林分整体更新情况一般.对林分整体而言,幼苗分别与大树、中树和幼树在0～25 m、0～15 m、0～40 m的空间尺度上呈显著正相关,而在其余尺度上均呈显著负相关;幼树与大树、中树分别在0～15 m、0～25 m空间尺度上呈显著正相关,而在其余尺度上无显著关联;大树与中树则在所有尺度上均无相关性.对林分内优势树种而言,红松大树与幼树在所有尺度上主要呈负相关,而三大硬阔、榆树大树与幼树均以不相关为主.人工补植红松幼树与三大硬阔及榆树的各大小级在研究尺度上表现为以负相关为主,三大硬阔和榆树幼树与其他优势种各大小级只在20 m尺度内呈现负相关;三者两两之间在中树及大树阶段在20 m以上的尺度均不相关.帽儿山天然次生林还处于演替的进程当中,在今后的森林资源管理过程中,应当采取积极的人工干预措施促进林分更新,并适时对不合理的空间格局进行调整.     

中亚热带4种森林凋落物量、组成、动态及其周转期

为研究亚热带次生林保护对森林生态系统养分循环等功能过程的影响。采用凋落物直接收集法,比较湘中丘陵区3种次生林(马尾松+石栎针阔混交林、南酸枣落叶阔叶林、石栎+青冈常绿阔叶林)和杉木人工林的凋落物量、组成特征及其周转期。结果表明:4种林分年凋落物量在414.4—818.2 g m-2a-1之间,3种次生林显著高于杉木人工林,3种次生林两两之间差异不显著,落叶对林分凋落物量的贡献最大,占林分凋落物量的59.9%—66.6%。杉木人工林和南酸枣落叶阔叶林的凋落物量月动态变化呈"双峰型",马尾松+石栎针阔混交林、石栎+青冈常绿阔叶林呈"不规则型"。优势树种的凋落物量对其林分凋落物量的贡献随林分树种多样性的增加而下降,杉木、马尾松凋落物量的月动态与其林分凋落物量的月动态基本呈一致变化趋势,但南酸枣、青冈、石栎没有一致的变化趋势。杉木人工林凋落物分解率最低(0.31),周转期最长(3.2 a),南酸枣落叶阔叶林分解率最高(0.45),周转期最低(2.2 a),凋落物的分解速率和周转随林分树种多样性增加而加快。可见,次生林凋落物量大,且分解快,周转期短,有利于养分归还和具有良好地力维持的能力。     

冰雪灾害对粤北天然次生林的损害及产生的林冠残体量

采用样地调查和取样,研究了2008年初中国南方冰雪灾害对粤北天然次生林的损害特征及其产生的林冠残体量.结果表明,灾害对粤北天然林造成严重损害,林木受害特征主要是胸径较大的植株断枝、断梢和断干较多,胸径较小的容易压弯,坡度大的林分翻蔸受害率增加.灾后林地林冠残体总量为38.12～43.52 t hm-2,平均41.25 t hm-2;地表凋落叶11.79～12.87 t hm-2,平均12.47 t hm-2;灾害产生的枝、干木质残体量为24.27～30.65 t hm-2,平均28.41 t hm-2.天然常绿阔叶林产生的林冠残体量较常绿与落叶混交林和杉木人工林大,造成林地林冠残体量骤增,一方面使林地存在严重安全隐患(如发生火灾和病虫害的风险增加),另一方面大量的林冠残体归还林地、改变了森林生态系统的结构与功能.     

台风“布拉万”对东北近天然落叶松云冷杉试验林的影响

台风是重要的森林干扰因子之一,会对森林生态系统的结构和功能产生较大的影响。2012年的台风"布拉万"对我国东北地区局部森林造成了严重的破坏。以受灾最重的吉林省汪清林业局的近天然落叶松云冷杉林为对象,采用方差分析和相关分析方法,研究林分结构和地形条件对林木株数损伤率的影响。结果表明:(1)林木损伤类型可分为折断、连根拔起、搭挂、压弯4种,其中连根拔起为最主要的损伤类型,占总损伤株数的52%,台风灾害造成的林木株数损伤率平均为14.09%。(2)径级大小对林木株数损伤率的影响显著。损伤主要发生于径级较小林分处,径级越大,其株数损伤率越小。(3)林木株数损伤率随林分密度的增加有减小的趋势,但在统计学上它们的关系不显著。(4)不同树种间的林木株数损伤率差异显著,落叶松、冷杉等针叶树种损伤株数最多。(5)林分的树种多样性指数与林木株数损伤率无显著的相关性。(6)海拔、坡度和坡位对林木株数损伤率的影响不显著,但坡向的影响显著,东北坡向林分的林木株数损伤率最大。研究结果可以为灾后森林恢复和减少风灾影响的森林培育措施提供依据。     

Causal analysis of the invasion of broad-leaved forest by bamboo in Japan

Abstract. In southwestern Tokyo the area covered by bamboo forest has expanded by a factor of 2.7 over the last 26 years. This has mainly been due to bamboo (Phyllostachyspubescens) invading secondary broad-leaved forests, probably after these were abandoned. In the first stage, bamboo sprouts develop from rhizomes at the periphery of the broad-leaved forest and then grow very quickly into young culms. In the next phase culm density increases annually, while the existing broad-leaved trees gradually lose their vitality and die. Finally, the broad-leaved forest is completely replaced by bamboo forest. The competitive ability of bamboo, based on its morphological and growth features, is suggested as the causal factor for the invasion: (1) bamboo can invade a neighboring broad-leaved forest by its vigorous rhizomes; (2) young bamboo culms can break through the canopy of broad-leaved trees; (3) bamboo quickly forms a crown in or above the canopy of the broad-leaved forest; (4) bamboo is very tolerant of strong wind and heavy snow accumulation; (5) bamboo culms, being very pliable during strong wind mechanically damage neighbouring broad-leaved trees.     

Wind damage and response in New Zealand forests: a review

The literature on wind damage in New Zealand forests is reviewed to investigate how abiotic and biotic factors influence damage severity, damage type, and forest recovery. Winds that damage forests tend to result from extra-tropical depressions or from topographically enhanced westerly air flows. Severe wind damage can occur when wind speeds exceed c. 0 km/hr, although investigating the relationship between damage and wind speeds is difficult, as gusts, for which speed is usually unrecorded, are important. Damage is often quantified by estimates of area affected, with some authors detailing the size and species of damaged trees within a given area. Key abiotic factors that influence damage patterns are topographical position, edaphic conditions, and disturbance history. Important biotic factors are tree height, tree health, position of the tree within the stand, and species. Damage type (uprooting or breakage) is primarily controlled by canopy position and rooting depth. Forest responses to wind damage include sprouting, recruitment, release, and suppression, with the dominant mode of forest recovery being strongly influenced by the severity of damage, and the species composition of the stand. As noted in international literature on wind damage, a lack of consistent methods, combined with poor species and spatial coverage, makes identifying general trends difficult. Investigating the role of wind damage in New Zealand forests has focused to date on Nothofagus forests and plantations of exotic trees and few studies have investigated long term dynamics following wind disturbance events.     

Vulnerability to strong winds for major tree species in a northern Japanese mixed forest: analyses of historical data

This study examined historical census data to evaluate the vulnerability of major tall-tree species in northern Japan to strong winds. Intensive data, which measured more than 20,000 damaged trees (defined as trees that were killed or lost their major crown) in >500 ha of a natural mixed forest, were collected immediately after a severe typhoon in 1954. More than half of the damaged trees had been uprooted, and the negative size-dependency was found for the proportion of uprooting throughout species. Simple correlation analyses with respect to the averaged species-specific characteristics suggested that tree species with a high crown-depth/height tended to uproot (against to stem breakage) in a size-class with diameter at breast height 30–50 cm. Although the census data had yielded no information about non-damaged trees, the estimation of pre-disturbed stand (based on 63 1-ha plot data together with aerial photographs and GIS) revealed that the observed damage reached ca. 25% in terms of basal area. The proportion of damaged trees seemed to be doubled among species (15–42% in basal area). A higher proportion of uprooting, which indicates a large supply of tip-up mounds, and mixture of less vulnerable species, might contribute to recovery process after a wind disturbance in this type of mixed forests.     

On the distributional limits of the lucidophyllous forest in the Japanese Archipelago

The distribution of the lucidophyllous forest and its transition to the summergreen broadleaf forest were studied in relation to such environmental factors as temperature and precipitation. The distribution is primarily affected by low temperatures during winter and secondarily by precipitation and sea wind. The upper and northern limits of the forest most closely correlated with the coldness index within four thermal indices. Because of much snow, the forest is more suppressed at a lower altitude in the region with high snowfall than in other regions. The area at its upper limit is dominated by the evergreenQuercus forest while the area at its northern limit is occupied by thePersea forest. Moreover, CI values in these distributional limits are significantly different. This phenomenon appeared to result from the resistance ability of dominant lucidophyllous trees not only to the thermal conditions but also to sea wind. In both the region with high snowfall and the region with high rainfall there is a zone where the evergreenQuercus forest overlaps theFagus crenata forest. In contrast, in the region with little rainfall, these two forests do not overlap but form a gap dominated by forests such as theFagus japonica forest. Thus, precipitation factors largely affect the altitudinal forest zones in Japan.     

Species diversity of Chinese beech forests in relation to warmth and climatic disturbances

The trends in the occurrence of climatic disturbances in the ChineseFagus range are described, and the relationship between woody species diversity and climatic factors in eight old-growth Chinese beech forests is characterized. In the ChineseFagus range that lies in the humid mountains of southern China, wind storms and heavy rain frequency increase towards the eastern coast. Thunderstorm frequency increases southwards. Snowfall frequency increases northwards. Glaze storm frequency peaks in the center near Lake Dongtian, but much higher in the east than in the west. Hailstorm frequency also peaks in the center. The forests sampled in this study are widely separated. Their canopies consist of either deciduous broad-leaved trees or a mixture of evergreen and deciduous broad-leaved trees. Their species diversity increases towards warmer sites and towards the east. The importance of the evergreen trees in relation to warmth and minimum temperature increases southwards. Our analysis suggests that wind storms and heavy rains enhance the species diversity of Chinese beech forests. Cold disturbances such as glaze and snow diminish the diversity and canopy dominance of evergreen broad-leaved trees but favor deciduous broad-leaved trees, especially beech. The annual precipitation received by the forests in this study varies from 1400–2550 mm. This is not correlated with diversity, however, probably because all of these forests grow in humid conditions with sufficient water being supplied by precipitation throughout the year.     

长白山寒温带风灾区植被受损与灾后变化程度及其影响因素

1986年台风袭击了长白山,在西、南坡的寒温带针叶林和岳桦林带形成了大量林窗.为了探究在强风干扰下寒温带森林植被受损和变化特征,揭示植被受损与灾后变化规律及其影响因子,2017年在长白山海拔1600～1800 m设立研究区.利用遥感资料,对研究区依据植被破坏程度和灾后变化程度进行植被差异分区,并布设了40个样方进行植被调查.结果表明: 按森林结构的受损程度可将长白山寒温带风灾区分为3个等级,轻度破坏、中度破坏和重度破坏,其中,中度破坏区的面积最大,其次是轻度破坏区、重度破坏区.乔木受损差异显著,轻度破坏区、中度破坏区和重度破坏区乔木优势种的数量分别减少20%、50%和85%,岳桦的抗风性大于鱼鳞云杉,大径级岳桦的抗风性大于小径级的岳桦.植被受损程度与坡度的相关性最强,随着坡度的增加,受风灾破坏程度减小.1987—2017年间,长白山寒温带风灾区的植被发生明显变化,根据变化的程度可将研究区分为3个等级:变化快、变化中等和变化慢,其中,变化中等的区域面积最大,其次是变化慢、变化快的区域;植被变化程度与海拔的相关性最强,随着海拔的增加,植被变化变慢.乔木的恢复较慢,鱼鳞云杉略好于岳桦;植被变化主要表现在灌木层和草本层,变化快的区域灌木层发育好于草本层;变化中等的区域草本层发育好于灌木层;变化慢的区域灌木层发育差异大,但草本层总体上表现为低矮稠密.