林下植被的生物量分布特征及其作用

林下植被是森林生态系统的重要组成部分。研究林下植被的生物量特征及其生态作用对深入研究森林生态系统结构和功能有重要意义。本文归纳了森林林下植被的生物量分布特征与森林的类型、龄级和林分特征等因子之间的变化关系,分析了林下植被在维持森林生态系统营养元素循环、保持水土、指示森林环境状态变化、影响森林林分的生理生态特征和森林演替、保护动物的栖息地以及维持生态平衡等方面的主要生态作用。     

南岭山地抗冰雪灾害常绿树种选择

2008年1—2月发生在我国南方地区的冰雪灾害对南岭常绿阔叶林造成了巨大的破坏,同时也为抗冰雪灾害树种选择提供了良好的平台。为了选择适宜冰雪灾害受损南岭森林恢复树种,结合广东省杨东山十二度水省级自然保护区灾后实地调查数据,利用合理-满意度结合多维价值理论的评价方法,建立树种筛选评价模型,以树种的受损指数、重要值、萌条率和林下更新种丰度等可量化因子为指标,计算各树种的单因素满意度,通过加权法计算其合成合理-满意度,以此筛选出乔木树种甜槠(Castanopsis eyrei)、雷公青冈(Cyclobalanopsis hui)、小红栲(C.carlesii)和深山含笑(Michelia maudiae),灌木树种广东杜鹃(Rhododendron kwangtungense)、鹿角杜鹃(R.latoucheae)、溪畔杜鹃(R.rivulare)为适宜在南岭山地冰雪灾害后恢复的优良树种。研究结果可为南岭冰雪灾害灾后恢复重建提供科学参考,也可为亚热带地区应对极端气候事件提供技术储备。     

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。     

辽河源自然保护区不同年龄天然油松林林下草本层植物物种多样性及其环境解释

林下草本层植物在森林群落结构稳定性的调节和生态功能的发挥上具有非常重要的作用,是森林生态系统不可或缺的组成部分。本文从揭示天然林林下物种组成的主导因子出发,以不同年龄天然油松林林下草本层植物为研究对象,探讨了辽河源自然保护区林下草本层物种组成与环境因子间的相关关系。结果表明,林龄是影响林分土壤化学性质的空间变化的重要因子,但林龄与林下草本植物的物种丰富度和多样性指数间不存在线性关系。CCA排序及Monte Carlo检验结果表明,林龄、林分密度、平均胸径、郁闭度、坡度为显著影响天然油松林林下物种分布的因子,说明该地区林分的冠层结构特征主导了林下草本层植物群落的分布格局。     

山西灵空山天然松栎混交林群落特征与冠层结构

以2011年建设的山西灵空山4 hm²天然松栎混交林森林动态监测样地为研究平台,以400个10 m×10 m样方为测量单元,于2016年进行群落特征研究,采用半球面影像法(DHP)分析冠层结构和林下光照特征.结果表明: 样地内共有乔木5558株,共计25种,分属于10科15属.冠层开阔度(CO)集中在15.0%～25.0%,叶面积指数(LAI)集中在1.5～2.5,林下光环境参数集中在10.0%～30.0%.建群种在样地内的分布对冠层结构和林下光环境影响显著;冠层结构对林下光环境所有参数的影响方向一致,其中采用叶面积指数评价冠层结构动态的效果更佳;冠层开阔度和叶面积指数对林下光环境产生相反的影响,且均对散射光入射率影响程度最大.温性松栎混交林的林冠层整体较为均匀,林下光分布较为集中,林分树种组成与冠层结构对林下光照影响显著.     

不同密度华北落叶松林天然更新及其影响因子

以关帝山区8种林分密度(128、240、320、400、480、560、640和720株·hm^-2)华北落叶松纯林为研究对象,分析了不同密度下华北落叶松天然更新优劣及其影响因子。结果表明: 更新指数随林分密度增大先升高后降低,中密度(400～560株·hm^-2)林分更新效果明显优于过疏和过密林分;林下光环境、草本植物及凋落物对落叶松更新有双重作用,光照过强、草本植物盖度过大或凋落物过厚不利于林下更新,土壤有机质可使土壤质地松软、水分含量充足并形成低磷高氮环境促进林分更新;各因子对更新指数的影响依次为:土壤含水量(0.798)>全氮(0.621)>凋落物厚度(-0.597)>土壤孔隙度(0.504)>土壤有机质(0.493)>全磷(-0.404)>林下总光照(-0.274)>草本植物盖度(-0.021)。在后续森林经营中,可通过抚育间伐或补植将林分密度控制在480株·hm^-2左右,并适当清理林下凋落物,改善土壤条件,促进华北落叶松天然更新。     

海拔和林分密度对热带雨林林下植物多样性的影响

海拔和林分密度是影响生物多样性的重要因子,但目前对热带雨林中海拔和林分密度复合影响林下植物多样性的效应及路径研究仍不足。本研究在海南热带雨林中基于海拔和林分密度设置了32个样地,调查了各样地植物特征,分析了海拔和林分密度对林下植物多样性(物种丰富度、Shannon多样性指数、Simpson优势度指数和物种均匀度)的影响,探索了两者直接或间接通过林分上层植物多样性和环境因子(郁闭度、凋落物、土壤C/N、土壤N/P和土壤pH)的影响路径。结果表明：海拔升高对林下物种丰富度、Simpson优势度和均匀度影响不大,但显著降低林下Shannon多样性,其主要通过改变林分上层Shannon多样性和郁闭度发挥间接调节效应;与之相比,林分密度增加显著降低林下物种丰富度,其既可通过增加郁闭度和土壤N/P产生间接影响,还可产生直接负效应。本研究证实了热带雨林中海拔和林分密度变化对林下植物多样性影响的不同,明确了郁闭度是两者复合调控林下植物多样性的重要因子,加深了林下植物多样性形成机制的认识。     

影响天然林下层植物物种多样性的林分因子的研究

以我国东北过伐林区3种典型森林类型为对象,用多元逐步回归方法来研究影响天然林下层植物多样性的林分因子,尤其是与森林经营有关的林分因子,从而通过经营来维持和增加物种多样性。研究表明,与经营有关的因子中对下层植物多样性有显著影响的有林分郁闭度、公顷株数和树种多样性。因此,在林分发展的一定阶段,应采取合理经营措施如采伐来控制林分密度,保持多树种的混交,来维持和增加树种多样性。     

树冠结构对典型阔叶红松林生产力的影响

阔叶红松(Pinus koraiensis)林是东北东部山区的地带性森林植被, 阐明其生产力的影响因素, 对于理解温带森林生产力维持机制具有重要意义。该研究依托小兴安岭典型阔叶红松林9 hm²动态监测样地, 基于2005和2015年的30 m × 30 m样方内所有胸径>6.5 cm的木本植物的调查数据, 计算各样方的树冠结构复杂性、物种多样性和林分胸高断面积, 结合各样方的地形和土壤理化性质数据, 拟合结构方程模型, 定量分析影响典型阔叶红松林生产力的直接和间接因素。研究结果显示: 树冠结构复杂性和物种多样性与生产力显著正相关, 且树冠结构复杂性对生产力的影响显著高于物种多样性; 树冠结构复杂性对生产力的作用分为树冠垂直分层和树冠可塑性, 其中树冠垂直分层是树冠结构复杂性影响阔叶红松林生产力的主要因素, 而树冠可塑性无显著影响; 林分胸高断面积与生产力显著正相关, 其解释权重仅次于树冠结构复杂性, 树冠结构复杂性与物种多样性均通过影响林分胸高断面积对阔叶红松林生产力产生间接影响; 考虑不同树冠结构复杂性时, 坡度和土壤全磷含量代表的环境因素在调节生产力上发挥的作用存在差异, 移除树冠垂直分层的作用后两者与生产力呈显著的负相关关系。综上可知, 在典型阔叶红松林中, 树冠结构复杂性比物种多样性更有效地解释了生产力的变化, 同时不可忽视其他生物和非生物因素对生产力的作用。     

宁南山区华北落叶松林下草本层群落特征及其影响因素

林下草本植物是森林生态系统的基本组成要素,对森林的更新、生态系统结构、功能的维持和提升具有重要作用,理解林下草本层群落特征及其影响因素,有助于构建理想的林-草结合模式。本研究以宁南山区泾源县无人为干扰的华北落叶松林人工林、间伐处理的华北落叶松林人工林和华北落叶松与白桦自然混交林为研究对象,探究林下草本层群落特征(物种多样性和地上生物量)及其与土壤理化特性(土壤容重、含水量、全碳含量、全氮含量及全磷含量)和林分结构(密度和郁闭度)的关系。结果表明：(1)与人工林相比,自然混交林林下草本植物组成最丰富(34种),且物种多样性和地上生物量也最高;(2)自然混交林林下土壤特性均优于人工林,但间伐处理的人工林林下土壤特性较无人为干扰的人工林土壤特性有显著提高;(3)冗余分析表明,林下草本层物种多样性主要与土壤含水量、土壤全碳、全氮和全磷含量呈正相关,与土壤容重、林分密度和郁闭度呈负相关,且林分密度、0～20 cm土层含水量对林下草本物种多样性有显著影响(P<0.05);(4)回归分析结果表明,0～20 cm土层的土壤特性、物种丰富度和优势度、林分密度及郁闭度显著影响林下草本地上生物量的积累...     

闽东沿海防护林台风灾害的影响因子

以2010年台风"鲇鱼"(编号1013)为例,调查闽东主要海防林树种台风受灾情况,并对其影响因子进行分析,结果表明:1)不同树种受害程度差异明显,阔叶树种受害重于针叶树种,平均受害级和受害指数分别高出79.1%和76.7%。其中,桉树受灾最重,平均受害级和受害指数分别比湿地松、木麻黄高出90.5%、36.2%和86.7%、36.6%。受灾类型中,折干现象最严重,比例高达40.7%。2)林木不同形态特征受灾程度差异显著,折干类型集中于12～14cm径级,比例为56.8%,倒伏、掘根类型集中10～12cm,比例为57.9%,弯干、断稍现象径级分布较均匀,但同在14cm比例最高,分别为28.6%和18.3%。林木抗风性能与植株尖削度成正相关,而与树高、树冠面积、树冠相对高度成负相关。3)地形条件是影响林木受灾的重要因素,表现为受灾程度迎风坡大于背风坡,陡坡大于缓坡,同一坡向上,迎风坡下腹大于上腹,背风坡正好相反。4)割脂对湿地松抗风性能有较大影响,割脂林木受害指数比未割脂高40.6%,因割脂发生折干植株比例为92.7%。     

台风对森林的影响

台风通过树枝折断、吹落叶果、产生倒木和折干等许多途径影响林分结构和动态。森林受害程度随树种、林龄、森林类型、树高和地形而异。高密度的森林通常具有较差的根系和较大的树高/胸径比值,在台风袭击下,往往具有较高的受损和死亡的风险。台风疏开郁闭的林冠层,促进了先锋树种的大量增加、生长和成熟,形成的林隙也为个体更新提供了机会。强风造成了土壤基质的多样化,从而促进了实生苗和幼树的更新和生物多样性的增加。台风也通过改变粗木质残体,枯枝落叶层,地洞和土墩,以及繁殖可用性来影响生物多样性。台风产生的粗死木和枯枝落叶使森林的碳储量迅速归还土壤,并影响土壤的养分分布。台风减少了动物的食物供应和恶化栖息地的环境,减少鸟的数量,促进昆虫扩散。受害森林给害虫滋生提供了场所。今后的研究热点是受台风干扰森林的长期监测,不同森林土壤的有机碳贮藏,土壤和养分流失规律,台风和其他自然灾害的交叉影响,改进数学模型以准确预测台风损害。     

Ice‐storm disturbance and long‐term forest dynamics in the Adirondack Mountains

Ice storms cause periodic disturbance to temperate forests of eastern North America. They are the primary agents of disturbance in some eastern forests. In this paper, a forest gap model is employed to explore consequences of ice storms for the long‐term dynamics of Tsuga canadensis‐northem hardwoods forests. The gap model LINKAGES was modified to simulate periodic ice storm disturbance in the Adirondack Mountains of New York. To adapt the gap model for this purpose, field data on ice storm disturbance are used to develop a polytomous logistic regression model of tree damage. The logistic regression model was then incorporated into the modified forest gap model, LINK ADIR, to determine the type of damage sustained by each simulated tree. The logistic regression model predicts high probabilities of bent boles or severe bole damage (leaning, snapping, or uprooting) in small‐diameter trees, and increasing probability of canopy damage as tree size increases. Canopy damage is most likely on gentle slopes; the probability of severe bole damage increases with increasing slope angle. In the LINKADIR simulations, tree damage type determines the probability of mortality; trees with severe bole damage are assigned the highest mortality rate. LINKADIR predicts Tsuga canadensis dominance in mesophytic old‐growth forests not disturbed by ice storms. When ice storms are simulated, the model predicts Acer saccharum‐dominated forests with higher species richness. These results suggest that ice storms may function as intermediate disturbances that enhance species richness in forested Adirondack landscapes.     

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。     

林火干扰对北方针叶林林下植被的影响

林下植被在北方针叶林植被群落中的物种多样性最高, 且具有较高的生物量周转率和地上部分净初级生产力, 对北方针叶林生态系统功能起着重要作用。火干扰是决定北方针叶林林下植被结构与功能的一个重要景观过程。该文综述了火干扰是如何通过与地形、火前林冠组成的交互作用而影响环境资源和林下植被的。最近的研究表明: 林下植被能够影响火后树木更新苗的定植、重建速率及森林演替轨迹; 林下植被还会通过影响元素的生物地球化学过程(凋落物降解和养分循环)影响林下环境资源的数量与异质性。因此, 研究火后初期北方针叶林林下植被的动态变化, 对于物种多样性保护和森林管理具有重要意义。     

达维台风对海南尖峰岭热带山地雨林群落的影响

 海南岛地处我国台风的频发地带, 台风是影响海南岛热带雨林的一个重要的自然干扰因子。该文对2005年达维台风前后海南尖峰岭热带山地雨林天然次生林2 600 m²固定样地的物种组成、胸高断面积、植株数目、风倒木的影响因子、物种多样性、生物量变化及碳储量归还进行比较分析。结果显示, 台风后森林内产生大量的风倒木、断枝和落叶, 导致群落郁闭度减少、透光性增强, 并产生大量的林窗。台风后群落的组成结构发生显著变化, 受损株数达514株(占总株数26.1%); 其中风倒木比例较大, 达206株(占总株数10.5%)。方差分析结果显示, 受台风影响产生的风倒木与未明显受损树木的胸径面积、树高和木材密度均无显著差异; 但与树种组成有较紧密的关联, 对乔木层、幼树层和下木层造成的损害存在种类上的明显差异。台风产生的损害可以分为直接性损害和间接性损害两种: 1)直接性损害主要作用于乔木层, 造成大径级植株严重受损; 部分树种重要值降低, 变成伴生种, 或者次优势种和原有优势种成为共同优势种; 2)间接性损害主要通过风倒木作用于幼树层和下木层, 产生的倒木、断枝和落叶压倒其它植株, 表现为小面积范围内的个体死亡, 甚至有种类消失; 部分优势种的个体数减少较多, 但占该种群所有个体数目的比例较小。乔木层的Shannon-Wiener和Simpson多样性指数均略有下降, 而幼树层和下木层均略有上升, 但3个林层均表现为不同程度的种类消失和一些种类的个体数目减少。此次台风还造成该样地至少占台风前总生物量10.42%的生物量归还给林地, 并对森林生态系统碳循环产生重大影响。     

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.     

Comparative height crown allometry and mechanical design in 22 tree species of Kuala Belalong rainforest, Brunei, Borneo

In rainforests, trunk size, strength, crown position, and geometry of a tree affect light interception and the likelihood of mechanical failure. Allometric relationships of tree diameter, wood density, and crown architecture vs. height are described for a diverse range of rainforest trees in Brunei, northern Borneo. The understory species follow a geometric model in their diameter-height relationship (slope, β = 1.08), while the stress-elasticity models prevail (β = 1.27-1.61) for the midcanopy and canopy/emergent species. These relationships changed with ontogeny, especially for the understory species. Within species, the tree stability safety factor (SSF) and relative crown width decreased exponentially with increasing tree height. These trends failed to emerge in across-species comparisons and were reversed at a common (low) height. Across species, the relative crown depth decreased with maximum potential height and was indistinguishable at a common (low) height. Crown architectural traits influence SSF more than structural property of wood density. These findings emphasize the importance of applying a common reference size in comparative studies and suggest that forest trees (especially the understory group) may adapt to low light by having deeper rather than wider crowns due to an efficient distribution and geometry of their foliage.     

Forest plant community as a driver of soil biodiversity: experimental evidence from collembolan assemblages through large‐scale and long‐term removal of oak canopy trees Quercus petraea

Plant–soil interactions are increasingly recognized to play a major role in terrestrial ecosystems functioning. However, few studies to date have focused on slow dynamic ecosystems such as forests. As they are vertically stratified by multiple vegetation strata, canopy tree removal by thinning operations could alter forest plant community through tree canopy opening. Very little is known about cascading effects on soil biodiversity. We conducted a large‐scale, multi‐site assessment of collembolan assemblage response to long‐term canopy tree removal in sessile oak Quercus petraea temperate forests. A total of 33 experimental plots were studied covering a large gradient of canopy tree basal area, stand age and local abiotic contexts. Collembolan abundance strongly declined with canopy tree removal in early forest successional stage and this was mediated by negative effect of understory plant community composition changes, i.e. shift from moss and forb to tree seedling, fern, shrub and grass species. Negative effect of this composition shift on collembolan species richness was largely offset by positive effect of the increase in understory plant species richness. This gives support to both the plant mass‐ratio and functional diversity hypotheses. Collembolan functional groups had contrasting response patterns, which were mediated by different ecological factors. Epedaphic (r‐strategist) abundance and species richness increased with canopy tree removal in relation with the increase in understory plant species richness. In contrast, euedaphic (K‐strategist) abundance and species richness declined with canopy tree removal in early forest successional stage in relation with changes in understory plant community composition and species richness, as well as microclimatic conditions. Overall, our study provides experimental evidence that forest plant community can be a strong driver of collembolan assemblages. It also emphasizes the role of trees as foundation species of forest ecosystems that can shape soil biodiversity through their regulation of understory plant community and ecosystem abiotic conditions.     

Influence of light and soil moisture on Sierran mixed-conifer understory communities

Sierra Nevada forests have high understory species richness yet we do not know which site factors influence herb and shrub distribution or abundance. We examined the understory of an old-growth mixed-conifer Sierran forest and its distribution in relation to microsite conditions. The forest has high species richness (98 species sampled), most of which are herbs with sparse cover and relatively equal abundance. Shrub cover is highly concentrated in discrete patches. Using overstory tree cover and microsite environmental conditions, four habitats were identified; tree cluster, partial canopy, gap, and rock/shallow soil. Herb and shrub species were strongly linked with habitats. Soil moisture, litter depth and diffuse light were the most significant environmental gradients influencing understory plant distribution. Herb cover was most strongly influenced by soil moisture. Shrub cover is associated with more diffuse light, less direct light, and sites with lower soil moisture. Herb richness is most affected by conditions which influence soil moisture. Richness is positively correlated with litter depth, and negatively correlated with direct light and shrub cover. Disturbance or management practices which change forest floor conditions, shallow soil moisture and direct light are likely to have the strongest effect on Sierran understory abundance and richness.