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。     

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.     

Fungicides for forest trees,shade trees and forest products

The Botanical Review -     

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.     

Traffic noise affects forest bird species in a protected tropical forest

The construction of roads near protected forest areas alters ecosystem function by creating habitat fragmentation and through several direct and indirect negative effects such as increased pollution, animal mortality through collisions, disturbance caused by excessive noise and wind turbulence. Noise in particular may have strong negative effects on animal groups such as frogs and birds, that rely on sound for communication as it can negatively interfere with vocalizations used for territorial defense or courtship. Thus, birds are expected to be less abundant close to the road where noise levels are high. In this study, we examined the effects of road traffic noise levels on forest bird species in a protected tropical forest in Costa Rica. Data collection was conducted in a forest segment of the Carara National Park adjacent to the Coastal Highway. We carried out 120 ten minute bird surveys and measured road noise levels 192 times from the 19th to the 23rd of April and from the 21st to the 28th of November, 2008. To maximize bird detection for the species richness estimates we operated six 12 m standard mist nets simultaneously with the surveys. The overall mist-netting effort was 240 net/h. In addition, we estimated traffic volumes by tallying the number of vehicles passing by the edge of the park using 24 one hour counts throughout the study. We found that the relative abundance of birds and bird species richness decreased significantly with the increasing traffic noise in the dry and wet season. Noise decreased significantly and in a logarithmic way with distance from the road in both seasons. However, noise levels at any given distance were significantly higher in the dry compared to the wet season. Our results suggest that noise might be an important factor influencing road bird avoidance as measured by species richness and relative abundance. Since the protected forest in question is located in a national park subjected to tourist visitation, these results have conservation as well as management implications. A decrease in bird species richness and bird abundance due to intrusive road noise could negatively affect the use of trails by visitors. Alternatives for noise attenuation in the affected forest area include the enforcement of speed limits and the planting of live barriers.     

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.     

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.     

Elevational zonation of afrotropical forest bird communities along a homogeneous forest gradient

Aim This study analyses the distribution and abundance of birds from a forested tropical gradient in order to determine whether elevationally distinct communities are detectable in this habitat. Location An avifaunal census was carried out on a single transect within the tropical forest of the Udzungwa Mountains in the Eastern Arc, Tanzania, covering a range in elevation from 300 to 1850 m. Methods Two complementary data sets on forest birds were analysed, encompassing (1) data derived from standardized 20‐ha spot‐mapping censuses performed at nine elevations over 175‐m intervals from 400 to 1800 m a.s.l., and (2) all observations of birds binned into 32 data points at 50‐m intervals, from 300 to 1850 m a.s.l. The degree of zonation in the avian community along the elevational gradient was examined using the chronological clustering method, an agglomerative hierarchical clustering method that can be carried out with a range of similarity indices. Results The chronological clustering analysis of the data set based on standardized spot‐mapping revealed a clearly defined boundary at c. 1200 m a.s.l., separating lowland from montane communities. Most bird species could be categorized as belonging to one of these two communities. The data set based on all observations revealed a number of potential secondary boundaries, although these boundaries delimited the entire elevational ranges of individual species in only relatively few cases. Main conclusions In contrast to previously published studies, we find evidence of an elevational zonation of distinct communities within a seemingly homogeneous habitat. Although similar boundaries have been assumed to arise as a result of vegetational ecotones, or because of interspecific competition, these mechanisms are poorly corroborated. We suggest that the causes of patterns of zonation are not well understood, and that the interplay among species distributions, species richness, and environmental factors needs more consideration. The chronological clustering method is proposed as an appropriate tool for studying these specific patterns.     

云南热带季雨林及其与热带雨林植被的比较

在中国植物学文献中, 对热带季雨林的解释和运用是不一致的, 特别是易于把季雨林与热带雨林相混淆。季雨林是在具有明显干、湿季变化的热带季风气候下发育的一种热带落叶森林植被, 是介于热带雨林与热带稀树草原(savanna)之间的一个植被类型。云南的热带季雨林在分布生境、生态外貌特征、植物种类组成和地理成分构成上, 均与热带雨林有明显区别, 季雨林主要分布在海拔1 000 m以下的几大河流开阔河段两岸和河谷盆地, 其群落结构相对简单, 乔木一般仅有1至2层, 上层树种在干季落叶或上层及下层树种在干季都落叶; 在生活型组成上, 季雨林的木质藤本相对较少, 大高位芽植物及地上芽植物很少, 但地面芽植物很丰富, 地下芽植物和一年生植物也相对丰富; 在叶级和叶型特征上, 季雨林植物的小叶和复叶比例相对较高, 分别占到24%和44%; 在植物区系地理成分构成上, 季雨林的热带分布属合计也占绝对优势, 但以泛热带分布属的比例相对较高, 约占到总属数的30%, 热带亚洲至热带非洲分布属的比例也较高, 约占总属数的12%。季雨林的地理成分更为多样性, 起源与发展历史也更复杂和古老。     

Beyond the tropics: forest structure in a temperate forest mapped plot

Question: How do the diversity, size structure, and spatial pattern of woody species in a temperate (Mediterranean climate) forest compare to temperate and tropical forests? Location: Mixed evergreen coastal forest in the Santa Cruz Mountains, California, USA. Methods: We mapped, tagged, identified, and measured all woody stems (≥1 cm diameter) in a 6‐ha forest plot, following Center for Tropical Forest Science protocols. We compared patterns to those found in 14 tropical and 12 temperate forest plots. Results: The forest is dominated by Douglas‐fir (Pseudotsuga menziesii) and three species of Fagaceae (Quercus agrifolia, Q. parvula var. shrevei, and Lithocarpus densiflorus), and includes 31 woody species and 8180 individuals. Much of the diversity was in small‐diameter shrubs, treelets, and vines that have not been included in most other temperate forest plots because stems <5‐cm diameter had been excluded from study. The density of woody stems (1363 stems ha^?1) was lower than that in all but one tropical plot. The density of large trees (diameter ≥30 cm) and basal area were higher than in any tropical plot. Stem density and basal area were similar to most other temperate plots, but were less than in low‐diversity conifer forests. Rare species were strongly aggregated, with the degree of aggregation decreasing with abundance so that the most common species were significantly more regular than random. Conclusions: The patterns raise questions about differences in structure and dynamics between tropical and temperate forests; these need to be confirmed with additional temperate zone mapped plots that include small‐diameter individuals.     

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。     

Changes in the forest floor of Canadian southern boreal forest after disturbance

Abstract. The concentrations and contents of organic matter and nutrients in organic deposits on the forest floor were estimated along a 231-yr chronosequence following fire at the southern limit of the boreal forest in eastern Canada. The sampling design was stratified to take into account the variability related to the presence of the principal tree species as well as to the presence of large gaps created by a recent spruce budworm (Choristoneura fumiferana) outbreak. The forest floor showed a steady accumulation of organic matter and total nutrients with time-since-fire and a 50 % decrease in the concentrations of available P and K, but not N (as determined by aerobic incubation). The increase in forest-floor weight was accompanied by an increased storage of available N, Ca and Mg. The availability of N and Ca was more strongly affected by tree species and gaps than by time-since-fire. A high N-availability was observed under Betula papyrifera and in gaps, while high a Ca-availability was found near Populus tremuloides and Thuja occidentalis. In old sites, the forest floor of gaps, created by a recent spruce budworm outbreak, had a necromass similar to that of a young forest, but the low concentrations of available P and K of an old forest.     

子午岭林区山杨-辽东栎混交林的生理生态效应

研究了黄土高原子午岭次生林区山杨林、辽东栎林和山杨-辽东栎混交林3种林分的土壤物理特性和叶片光合特性.结果表明,山杨林地在0～300 cm土层的土壤含水量最大,而在200 cm土层以下,山杨 辽东栎混交林的土壤水分明显改善,并优于辽东栎林;在0～60 cm土层内,山杨林地土壤容重最大、土壤孔隙度最小,而山杨-辽东栎混交林的土壤容重最小、土壤孔隙度最大,且均优于纯林,说明混交林地有深层土壤水分可供利用,同时土壤理化特性得到改善.山杨林和辽东栎林的叶绿素含量较高,且均明显高于山杨-辽东栎混交林.辽东栎林的光合速率和气孔导度最大,其次为山杨林, 二者均明显高于山杨-辽东栎混交林.从叶片水分利用效率来看,辽东栎林>山杨-辽东栎混交林辽东栎>山杨-辽东栎混交林山杨>山杨林.山杨-辽东栎混交林中辽东栎的PSⅡ最大光化学转换效率(F_v/F_m)和PSⅡ潜在活性(F_v/F_o)值均较大,但与辽东栎林的F_v/F_m和F_v/F_o值差异不显著,而混交林中山杨的F_v/F_m和F_v/F_o值均相对小于山杨林,且与山杨林的F_v/F_m差异显著,山杨林和辽东栎林的荧光光化学猝灭系数和非光化学猝灭系数值均大于混交林地.因此,子午岭林区辽东栎林更趋于稳定且生长优于其混交林,而山杨林群落将逐步被替代,与纯林类型相比较,其混交林类型可能较不利于山杨的生长.     

森林群落波动的探讨

植物群落的波动是森林动态的一种表现形式,是指由于群落中复合生态因子逐年逐季的不同,引起群落在固有的季节性和逐年性变化上的差异.波动不改变群落的总体物种组成结构和群落性质.植物群落的波动具有可逆性和方向性.正向波动促使群落具更优化结构,负向波动则反之.本文组建了测度植物群落波动强度的公式:,并将森林群落波动的基本类型分为树木生长速度的波动、结实率以及幼苗多度的波动、叶量的波动和植物季节性发育周期的波动4种类型.