西藏冷杉原始林林隙对草本植物和灌木树种多样性的影响

研究了西藏东南部亚高山原始冷杉林林隙对草本植物和灌木树种多样性的影响．结果表明,西藏东南部亚高山原始冷杉林林隙与非林隙林分内草本植物和灌木树种的种类组成、数量、密度和物种多样性均存在较大的差异．由于林隙内光照条件的改善,草本植物和灌木树种更加丰富;林隙内有喜光的草本植物和灌木,也有耐荫性较强的草本植物和灌木,而非林隙林分内仅有耐荫和较耐荫的草本植物和灌木;大部分林隙内的草本植物和灌木树种的物种多样性和均匀度大于非林隙林分;林隙内与非林隙林分的群落相似系数较小,表明林隙与非林隙林分草本植物和灌木群落组成存在差异．林隙大小在174．2～562．2m^2之间,群落相似系数与林隙大小无明显关联．林隙促进了草本植物和灌木树种的繁衍,在维持藏东南亚高山原始冷杉林的物种多样性方面起着重要作用．     

林隙对小兴安岭阔叶红松林树种更新及物种多样性的影响

研究了小兴安岭阔叶红松林不同林隙梯度(林隙中心、林隙近中心、林隙边缘)中主要树种的数量特征,以及林隙大小对树种更新的影响.结果表明:不同梯度林隙内灌木树种的密度均明显高于非林隙,同种灌木密度的比值在1.08～18.15之间;随林隙面积增加,乔木幼苗更新密度逐渐增大,幼树Ⅰ(高度H≥1 m,胸径DBH≤2 cm)和幼树Ⅱ(H≥1 m,2 cm＜DBH≤5 cm)的更新密度呈多峰曲线.林隙灌木总体更新密度主要随幼苗和幼树Ⅰ数量而变化.林隙内不同位置幼苗的平均树高、平均基径、种密度和个体密度有所差异.从林隙中心到非林隙,更新层乔木幼苗重要值的大小顺序为:林隙中心＞林隙近中心＞林隙边缘＞非林隙;物种均匀度呈高-低-高的变化,物种多样性的变化为早期林隙＞中期林隙＞晚期林隙.     

局域与区域生态过程对太白山牛皮桦林林隙内草本植物物种丰富度的影响

以太白山牛皮桦林林隙内草本植物总数为区域物种丰富度,分别采用0.25m2和1m2样方重复抽样的丰富度平均值为局域物种丰富度,来探讨区域物种多样性变异对局域多样性的影响。结果显示:(1)0.25m2和1m2局域物种丰富度与区域物种丰富度显著相关(r=0.791和r=0.861),且随区域物种丰富度的增加而增加;同时,林隙面积也能显著增加局域和区域物种丰富度。(2)控制林隙面积变量的多元回归分析显示,0.25m2和1m2局域物种丰富度与区域物种丰富度存在显著线性回归关系(R2=0.642和R2=0.743);方差分离分析显示,林隙面积仅能解释0.25m2和1m2局域物种丰富度变异的4.0%和4.4%,而区域物种丰富度能解释25.8%和35.3%。研究表明,区域物种丰富度变异在一定程度上决定着局域物种丰富度的组成。     

红松阔叶混交林林隙大小及光照对草本植物的影响

在小兴安岭红松阔叶混交林中选取的6个林隙内,以每个林隙中心为起点,沿东西和南北两个方向,每隔2 m平行布置1个1 m×l m的固定样方.2011年6月和9月利用估测法测定样方内不同高度等级草本植物的覆盖度和多度,记载样方内基质特征.6-9月每月选择阴天,利用冠层分析仪拍摄鱼眼照片,用Gap Light Analyzer 2.0软件计算相对光强.分析不同林隙间相对光强、草本植物覆盖度和丰富度的差异,以及各物种覆盖度与直射光、漫射光和基质的关系.结果表明:开阔区和林冠下的大林隙相对光强均大于小林隙,而且从林隙中心到林隙边缘的漫射光、直射光变化范围也大于小林隙;不同区域大、小林隙到达地面的直射光大小顺序为北部大于南部;在Z1～Z4区域内,大林隙的草本植物覆盖度和丰富度均大于小林隙,其中大、小林隙物种丰富度之间的差异达到了显著水平.另外,大多数草本植物覆盖度与漫射光和基质之间显著相关,只有少数草本植物覆盖度与直射光呈相关关系.     

广西弄岗北热带喀斯特季节性雨林林隙特征与空间分布

林隙是森林中一种普遍存在的小尺度森林干扰形式,对促进森林更新和循环演替具有重要作用。对热带喀斯特森林的林隙干扰目前还了解不多。该文采用Worldview-3高空间分辨率遥感影像结合地面调查,对弄岗喀斯特季节性雨林15 hm~2样地林隙干扰特征及其空间分布规律进行了研究。结果表明:样地内共解译到305个林隙,林隙的密度约为每公顷20个,林隙大小的变化范围为10～371 m~2,平均大小为52.3m~2,林隙面积占森林面积的10.6%;林隙在0～50 m尺度整体表现出聚集分布格局;林隙空间分布与大树(DBH≥10 cm)存在显著空间关联,与小树(DBH10 cm)和枯立木无显著空间关联;不同生态因子对林隙的数量分布和基本结构影响不同,对林隙数量分布影响最显著的包括凹凸度、干旱度指数、丰富度,而坡向、海拔、丰富度对林隙大小有显著影响,海拔、岩石裸露度、地形湿润度指数、干旱度指数、多度等5个生态因子对林隙周长有显著影响。研究结果表明林隙在喀斯特季节性雨林普遍存在,林隙的空间分布与特征存在着地形分异特征,是喀斯特独特的地质地貌和生境条件与喀斯特森林自身生物学特性综合作用的结果。     

喀斯特森林林隙梯度物种多样性变化规律

采用Margalef物种丰富度指数(R1)、Shannon-Wiener指数(H′)及Pielou均匀度指数(J)来研究物种多样性的林隙梯度变化。结果表明:从林隙中心至非林隙林地的水平梯度上,林隙不同区域的种类组成存在较大差异,一些阳性树种如圆果化香等在林隙中心分布较多,青冈等耐荫性强的树种则在郁闭林下较为丰富,而中度耐荫种类如香叶树、大叶冬青等则集中分布在林隙近中心和林隙边缘处。从非林隙到林隙中心,物种丰富度逐渐升高,即非林隙<林隙边缘<林隙近中心<林隙中心;物种多样性的变化则总体呈中间高两头低的现象,均匀度的变化与其一致;物种多样性林隙梯度变化程度受林隙发育期和面积的影响较大,变化程度为早期林隙>中期林隙>晚期林隙,大林隙>中等林隙>小林隙,早期林隙和大林隙的边缘效应显著。     

阔叶红松林林隙结构与树种多样性关系研究

对阔叶红松林林隙与林下不同层次树种多样性进行比较,探讨林隙大小及发育阶段与树种多样性间的关系.结果表明,林隙与林下树种多样性存在显著差异（P<0.01）.与林下相比,林隙更新层树种多样性、丰富度和均匀度增大,生态优势度减小（P<0.01）;演替层树种多样性、丰富度和均匀度减小,生态优势度增大（P<0.0001）.林隙中不同层次树种多样性随着林隙大小呈现出相反的变化趋势.长白山阔叶红松林林隙演替层树种多样性和丰富度总体上呈单峰形变化,中等大小林隙（100～250 m²）中树种多样性和丰富度较高,生态优势度较小.而更新层树种多样性和均匀度在≥250 m²和<100 m²的林隙中最大,在200～250 m²的林隙中最小;生态优势度在200～250 m²的林隙中达到最大.更新层和演替层树种对林隙面积大小反应不同,有利于更新层幼苗建立的林隙面积并不是演替层幼树发育和成活的最适面积;随林隙年龄的增加,更新层和演替层树种多样性在不同层次上呈互补关系.     

白龙江上游地区森林植物群落物种多样性的研究

 白龙江上游地区属长江防护林工程重点地区之一。根据36个样地的调查资料,分析了该地区森林植物群落物种多样性的特征：群落内各层物种丰富度指数的大小顺序为“灌木层>草本层>乔木层”;均匀度指数变化比较复杂,在杜鹃巴山冷杉（Rhododendron fastigiatum-Abies fargesii）林中为“草本层>灌木层>乔木层”,在苔藓巴山冷杉林中为“乔木层>灌木层>草本层”,其余群落中为“灌木层>草本层>乔木层”;多样性指数的大小顺序为“乔木层<灌木层和草本层”,而灌木层与草本层的多样性指数随林分郁闭度变化而变化,在郁闭度30%的杜鹃巴山冷杉林中,草本层大于灌木层,在郁闭度47%的箭竹巴山冷杉林中,草本层和灌木层相当,在郁闭度55%以上的各个群落内,灌木层大于草本层。同一海拔不同坡向群落的物种多样性表现为分布于阳坡的油松（Pinus tabulaeformis）林大于分布于阴坡的草类云杉（Picea asperata）林。物种多样性沿海拔梯度的变化表现为随海拔升高先降低后增加,从海拔2 400 m的栎类阔叶林,2 600 m的草类云杉林,2 800 m的箭竹(Sinarundinaria nitida)巴山冷杉林,到3 000 m的苔藓巴山冷杉林和3 200 m的杜鹃巴山冷杉林,物种多样性依次下降,到海拔3 400 m的高山杜鹃（Rhododendron fastigiatum）灌丛,物种多样性增加。物种多样性在紫果云杉(Picea purpurea)林的演替系列中表现为随群落演替发展而增加,后降低,在针阔混交林阶段达到最大。     

小兴安岭阔叶红松混交林林隙特征

对小兴安岭阔叶红松混交林林隙基本特征进行了研究。结果表明:林隙的线状密度为31.78个/km,冠空隙和扩展林隙所占的面积比例分别为15.71%和30.78%;冠空隙的年干扰频率为0.46%,干扰轮回期约为434.8a。冠空隙的大小变化在42.12—372.52m2之间,平均为153.37m2;扩展林隙的大小变化在98.65m2—633.10m2之间,平均为300.44m2。冠空隙和扩展林隙面积分布格局均符合Weibull分布。林隙形成方式主要为干基折断,占总形成木总数的35.29%,其次为掘根风倒,占28.43%。平均每个林隙的形成木为4.98株,由红松、白桦、枫桦、冷杉形成,径级在20—30 cm之间,高度在15—30 m之间。冠空隙的直径与高度比值的相对频率的分布呈单峰型曲线,当比值为0.30—0.45时,出现峰值;而扩展林隙的直径与高度比值的相对频率的分布呈双峰型曲线,当比值分别为0.75—0.90和1.05—1.15时,出现峰值。林隙边缘木胸径级的多度分布和高度级多度分布符合Weibull分布,但不符合正态分布。约13.41%的边缘木未出现偏冠现象,偏冠率在0.5—0.7之间的边缘木占70.49%。     

卧龙自然保护区亚高山暗针叶林林隙特征研究

以卧龙亚高山暗针叶林为研究对象,分析了森林群落林隙的大小结构、形成方式及林隙形成木(GM)的结构特征．结果表明,林隙密度为18．5个·hm^-2冠林隙和扩展林隙分别占森林面积的28．4％和60．0％;冠林隙的大小变化在10～1134．7m^2之间,平均面积为153．45m^2;扩展林隙的大小变化在84．11～1646．3m^2之间,平均面积为324．34m^2;平均每个林隙的形成木为5．14株,单株形成木形成的林隙只占8．1％．不同形成木类型对林隙形成的贡献大小次序为：折干>掘根>枯立>断梢;暗针叶林林隙大多由岷江冷杉、铁杉、糙皮桦形成．径级在60～70cm,高度在30～35m之间的林冠上层的岷江冷杉,发生折倒形成林隙的可能性最大．     

火对森林土壤的影响

林火是林地上自由蔓延的火,主要有计划火烧(控制火烧)和野火2种类型.火烧的严重程度决定了火灾的效果及其影响的持续时间.火能够通过燃烧有机质和改变粘土矿物来影响土壤结构,导致土壤容重增加和持水能力降低.长期来看,火烧引起土壤有机质减少.火烧之后土壤温度和pH值的升高会促进土壤呼吸,而微生物数量的减少、根系的死亡和可分解物质的减少则减弱土壤呼吸.林火消耗了森林的枯落物层,通过氧化、挥发、灰分颗粒对流、淋溶等途径减少了森林土壤的养分含量.火灾对土壤生物有重要影响,火灾引起的高温可直接杀死土壤微生物,同时通过改变土壤的各种理化性质及林地微环境,间接影响土壤微生物生存和群落的组成.火对土壤动物的影响显著小于对土壤微生物的影响,原因是前者具有更高的灵活性来逃避火灾.中低程度火烧主要通过土壤环境变化间接影响土壤酶,而严重火烧则通过高温直接使其变性.今后应开展跨学科的森林火灾长期研究,加强对火烧后土壤动物、微生物和生态系统之间相互关系的研究,注重计划用火、火灾对土壤有机碳、土壤养分库的稳定、土壤斥水性、水土流失强度和生物多样性影响方面的研究.     

林隙干扰对森林生态系统的影响

林隙干扰通过改变森林微生境异质性和群落演替进程,对森林物种组成、林分结构和系统功能产生重要影响。本研究评述了有关林隙干扰对森林生态系统影响的最新研究进展,从物种生物学特性和环境因素两个方面分析了林隙干扰对森林物种组成变化的影响规律,基于群落组件和群落架构阐述了林隙干扰对森林结构的作用关系,梳理了林隙干扰对森林生态系统功能的影响机制。基于已有研究的分析和目前森林生态系统经营亟需解决的问题,提出未来研究所需关注的重点领域和问题: 林隙面积阈值确定方法;林隙闭合机制;林隙干扰对森林生态系统过程的影响;林隙干扰与森林生产力的关系。林隙干扰在促进物种更新和提升森林结构复杂性等方面具有优势,因此本研究可为我国低产低效人工林改造提供科学依据。     

森林采伐对森林景观的长期影响模拟

应用空间直观景观模型(LANDIS),模拟了小兴安岭友好林业局在有无采伐方案下400年内森林景观的动态变化,并利用统计软件APACK计算代表性树种的分布面积、年龄级和反映物种分布格局的聚集度指数.结果表明:与无采伐相反,采伐下的火干扰模式为高频率小面积低强度火烧;采伐对各种群的分布面积影响不大,但显著改变了种群的年龄结构,主要表现为降低了过熟林的分布面积,而增加了其他年龄级森林的分布面积;采伐降低了各树种的聚集度,导致森林景观一定程度上的破碎化.     

Organic matter and nutrient dynamics of the forest and forest floor in the Hubbard Brook forest

Summary The forest floor is a major reservoir of organic matter and nutrients for the ecosystem and as such it influences or regulates most of the functional processes occurring throughout the ecosystem. This study reports on the nutrient and organic matter content of the forest floor of the Hubbard Brook Experimental Forest during different seasons and attempts to correlate results from studies of vegetation, litter, decomposition, stemflow, throughfall, and soil. An organic matter budget is presented for an undisturbed watershed.Average weight of the forest floor on an undisturbed watershed ranged from 25,500 to 85,500 kg/ha. The weighted watershed average was 46,800 kg/ha. Although the F and H horizons did not vary significantly with time, the L horizon increased significantly during the period June to August largely as a result of a severe hail storm. The order of abundance of elements in the forest floor was N;CaFe>S>P>Mn>K>Mg>Na>Zn>Cu. The concentrations of Ca, K, and Mn decreased with depth in the forest floor while N, P, S, Na, Fe, Zn, and Cu concentrations increased. N:P ratios were similar in decomposing leaf tissue, the forest floor, litterfall, and net stemflow plus throughfall suggesting a similar pattern of cycling. S was proportional to N and P in decomposing leaf tissue, the forest floor, and litterfall. Net stemflow and throughfall were affected by a relatively large input of SO₄=-S from the atmosphere. Residence times for elements in the forest floor were affected by inputs other than litterfall (precipitation, stemflow, and throughfall). Calculation of residence times using all inputs caused smaller values than if litterfall alone was used. While all residence times were reduced, the major differences occurred for K, S, and Na. N and P showed relatively long residence times as a result of retranslocation and immobilization by decomposers. The slow turnover rate because of the strong demand and retention by all biota must account for the efficiency of the intrasystem cycling process for N and P. K showed the shortest residence time. A rapid and efficient uptake of K by vegetation seems to account for the efficient cycling of this element. The patterns of nutrient cycling are several depending on the chemical properties of the forest floor, and nutritional requirements of the biota.This is contribution No. 67 of the Hubbard Brook Ecosystem Study. Financial support was provided by the National Science Foundation.     

Restoration of the understorey layer of recent forest bordering ancient forest

Abstract. Recently established forests are commonly characterized by an impoverished understorey. Restoration is mostly based on spontaneous secondary succession, but little is known about the time period needed to achieve a community species pool with species composition equal to that of ancient forests. Vegetation in transects of 197 plots in 13 recent forest stands contiguous to the Meerdaalwoud ancient forest complex was surveyed. The recent forest stands ranged in age from 36 to 132 yr. The community species pool was described with an ecological, functional and phytosociological approach and based on groups derived from a CCA. Differences in community species pool between age classes of recent forest stands were analysed. During establishment of a new forest competitive species, forest edge species and species with high Ellenberg values for light and nitrogen and a more persistent seed bank will dominate the understorey. After 90 yr of succession the cover by these species decreases and reaches equal values to ancient forest after ca. 105 yr. A large number of forest species will be able to colonize the forest in less than 90 yr. Some typical forest species, however, have very low colonization rates and still have low cover in recent forest more than 105 yr old, so that complete restoration of the understorey requires a time period of over a century. Anthropogenic introduction of forest plant species may reduce the time required for ancient forest vegetation equality.     

Differences in forest composition in two boreal forest ecoregions of Quebec

Abstract. In order to describe and compare the post‐fire succession patterns of the two ecological regions (mixed‐wood and coniferous ecoregions) of northwestern Quebec, 260 forest stands were sampled with the point‐centred plot method. The mixed‐wood ecological region belongs to the Abies balsamea‐Betula papyrifera bioclimatic domain whereas the coniferous ecological region belongs to the Picea mariana‐moss bioclimatic domain. In each plot, tree composition was described, surficial deposits and drainage were recorded, and fire history was reconstructed using standard dendro‐ecological methods. Ordination techniques (Correspondence Analysis and Canonical Correspondence Analysis) were used to describe the successional patterns of forest vegetation and to correlate them with the explanatory variables. The results showed the importance of surficial deposits, the time since fire and the ecoregion in explaining the variation of stand composition. Abies balsamea tends to increase in importance with an increase in time since fire, and this trend is more pronounced in the mixed‐wood region. Even when controlling both for surficial deposits and time since fire, differences in successional trends were observed between the two ecoregions. As all the species are present in both ecoregions and as they are all observed further north, our results suggest that both the landscape configuration and fire regime parameters such as fire size and fire intensity are important factors involved in these differences.     

长白山典型林区森林资源利用适宜性分析

天然林保护不是简单的禁伐,东北林区作为天然林保护的限伐林区,目前仍有一定数量的成过熟林采伐任务,如何科学合理地选择伐区非常重要．鉴于传统森林资源采伐利用操作中存在顾此失彼的问题,现代科学的森林资源经营理论认为,森林资源利用要坚持可持续利用原则,并且要更多考虑森林资源的生态效益,遥感(RS)数据及地理信息系统(GIS)技术,通过提供空间选择技术支撑,可以准确定位符合采伐标准的森林资源地理位置,并确定其面积、森林类型等信息,从而促进森林资源的科学合理利用．本文综合考虑各方面要素,以长白山典型林区露水河林业局为例,以最大程度发挥森林生态系统的生态功能为原则,进行了森林资源利用状况评价,对研究区森林资源未来利用的空间选择以及采伐利用方式进行了探讨,以期为将来制订科学的森林经营策略提供依据。