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.     

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.     

Fungicides for forest trees,shade trees and forest products

The Botanical Review -     

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...     

基于森林生态系统服务权衡与协同的森林可持续管理

森林是水库、钱库、粮库、碳库,提供多种生态系统服务,对缓解全球气候变化、维护国土生态安全和促进经济社会可持续发展具有基础性、战略性作用。科学认识不同森林生态系统服务间的权衡与协同对实现森林多重效益和开展森林可持续管理至关重要,但森林生态系统服务间的协同或权衡关系存在较大不确定性、因不同研究而异,导致如何通过森林经营实现森林生态系统多种服务成为关键挑战。全面梳理森林生态系统多种服务之间协调与权衡研究现状后发现：(1)研究聚焦森林碳汇、木材供应、生物多样性、森林游憩等多种服务之间的关系与影响因子;天然林的协同效应高于人工林,林龄、林分密度、树种组成、气温、海拔、社会偏好、管理政策等是主要驱动因素;(2)对比不同森林经营模式或管理措施对森林生态系统多种服务的影响,可持续经营是协同实现森林多种效益的有效途径;(3)气候变化与森林生态系统多种服务之间的相互作用取决于气候因子种类与变化程度、森林类型、森林管理方式、区域环境等,当前重点围绕IPCC发布的未来气候变化情景开展研究;(4)借助InVEST、FSOS、CASA等工具,模拟优化森林管理情景,探索兼顾森林多目标的管理方案。同时,系统总结现有研...     

红松林和针阔叶混交林下黏菌物种多样性研究

为探讨不同林型下黏菌物种多样性的差异,本文在凉水国家级自然保护区内红松林和针阔叶混交林两种林分中开展调查研究,共采集黏菌样本242份,基于形态特征鉴定为4目7科17属50种黏菌,其中鲜红团网菌Arcyria insignis、网格筛菌Cribraria paucidictyon和玫瑰绒泡菌Physarum roseum...     

Pollination and reproduction of a self-incompatible forest herb in hedgerow corridors and forest patches

Habitat-corridors are assumed to counteract the negative impacts of habitat loss and fragmentation, but their efficiency in doing so depends on the maintenance of ecological processes in corridor conditions. For plants dispersing in linear habitats, one of these critical processes is the maintenance of adequate pollen transfer to insure seed production within the corridor. This study focuses on a common, self-incompatible forest herb, Trillium grandiflorum, to assess plant–pollinator interactions and the influence of spatial processes on plant reproduction in hedgerow corridors compared to forests. First, using pollen supplementation experiments over 2 years, we quantified the extent of pollen limitation in both habitats, testing the prediction of greater limitation in small hedgerow populations than in forests. While pollen limitation of fruit and seed set was common, its magnitude did not differ between habitats. Variations among sites, however, suggested an influence of landscape context on pollination services. Second, we examined the effect of isolation on plant reproduction by monitoring fruit and seed production, as well as pollinator activity and assemblage, in small flower arrays transplanted in hedgerows at increasing distances from forest and from each other. We detected no difference in the proportion of flowers setting fruit or in pollinator activity with isolation, but we observed some differences in pollinator assemblages. Seed set, on the other hand, declined significantly with increasing isolation in the second year of the study, but not in the first year, suggesting altered pollen transfer with distance. Overall, plants in hedgerow corridors and forests benefited from similar pollination services. In this system, plant–pollinator interactions and reproduction seem to be influenced more by variations in resource distribution over years and landscapes than by local habitat conditions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mycorrhizae and forest ecosystems

Summary Mycorrhizae play an important role in regulating patterns of energy and nutrient flux in terrestrial ecosystems. To conceptualize this role I develop the theory behind a simple index of the efficiency of soil resource acquisition by plant root systems (E). The morphological, physiological and demographic characteristics of mycorrhizae that define E appear to vary with environment and with plant community composition. This theory is elaborated with examples drawn from forest ecology literature. Some inconsistencies among observations of fine root dynamics are particularly revealing: (1) belowground carbon allocation vs soil fertility; (2) causes of root mortality; (3) root longevity vs decomposition rates. A comprehensive theory of mycorrhizal and ecosystem dynamics must await resolution of these inconsistencies and better quantitative information on mycorrhizal features affecting E.     

小兴安岭带岭林区红松阔叶林景观多样性与稳定性研究

选取具有典型代表性的黑龙江省小兴安岭带岭林业局东方红林场为研究对象,在应用地理信息系统软件对现行森林经营措施进行分析的基础上,探讨了该林场景观分类、景观变化动态分析的结果和成因,并应用马尔可夫转移模型进行景观模拟预测.结果表明,研究期间东方红林场一级分类和二级分类的景观多样性指数较低,有林地面积占整个研究区域的91%以上,构成了景观的基质;1985～1993年间,有林地优势地位加强,优势度从0.611增加到0.692,顶极群落优势度增加70%;在以择伐为主伐更新措施条件下,红松阔叶林在201～209年间将达到稳定状态,面积为13 120～13 22 hm²,成为当地稳定的顶极植被群落.     

Effects of forest clear-cutting and soil disturbance on the biology of small forest brooks

As a part of the larger Nurmes research project, we studied the effects of clear-cutting and soil disturbance (ditching, ploughing, mounding) on the biology of small forest brooks. After these forestry activities, incoming light, temperature, and nutrient content of the water increased significantly. Mean algal biomass peaked during the first summer after clear-cutting. During the first year following soil disturbance, algal biomass initially decreased because of turbidity, but began to rise again as suspended solids in the water decreased in the summer months. Species composition changed, too; after clear-cutting, Cryptomonas and Chlamydomonas species increased their densities (48% of the algal biomass) and following soil disturbance, the species numbers and densities of Conjugatophyceae (52% of the algal biomass) were higher than before. Canonical correspondence analysis suggested that increased nutrient levels and acidity were the main factors behind the changes in the flora following clear-cutting. The most important effect of soil disturbance was the increased water temperature. Effects of forest clear-cutting on algal productivity in the brooks remain evident at least for three years and those of soil disturbance for an even longer period. Restricted clear-cutting, with a protective zone left uncut around the brooks, appears to reduce the effects.     

Density and microhabitat use of Bengal slow loris in primary forest and non-native plantation forest

The extent of planted forests has greatly increased in the tropics, but their conservation value while assumed to be low, is largely unknown. We compared the density and microhabitat selection of a nocturnal arboreal primate, the Bengal slow loris (Nycticebus bengalensis), in mostly undisturbed, evergreen tropical forest to those in 15-18 year old Acacia/Leucaena plantations with significant secondary regrowth, and <15 year old plantations with little regrowth. Based on estimates derived from distance sampling, loris densities in older plantations were nearly identical to primary forest (4.26 vs. 4.00 lorises per square kilometer), although encounter rates were three times higher in the older plantations probably owing to the lower detection probability in the more complex vegetation of the primary forest. The mean density estimate for the younger plantation was one-third of the above habitats (1.27 lorises per square kilometer), although not statistically different. Lorises tended to use larger diameter and taller trees, with a greater crown depth than randomly sampled trees, and tended to avoid habitats with sparsely crowned trees. The older plantations had trees with lower basal area and shorter stems than the primary forest; however, the older plantations contained higher densities of Bauhinia lianas, a commonly eaten food source and did not contain the red giant flying squirrel (Petaurista petaurista), a potential competitor. Although it is unknown whether the Bengal slow loris would persist without the presence of primary forest in the landscape, we suggest that older plantations have conservation value for at least selected species and as such, could be better managed to increase this value.     

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.     

森林经营决策支持系统的设计与实现及在采伐中的应用

我国传统的森林经营方式比较落后,数字化水平不高,决策过程比较盲目.在地理信息系统平台中集成森林动态模型,建立森林经营决策支持系统,可以充分发挥地理信息系统的可视化、空间分析以及模型模拟预测功能,加强处理森林在较大时空尺度上的动态变化的能力.本文设计并实现了森林生长率模型、景观采伐模型和矩阵模型,开发了森林经营决策支持系统,回答森林采伐经营中“采多少,采哪里,怎么采”的三个主要问题,在长白山区的露水河林业局和三岔子林业局进行应用,为提高我国森林可持续经营管理的数字化水平提供了技术支持.     

亚热带常绿阔叶林和杉木人工林茎流与穿透雨的养分特征

亚热带常绿阔叶林和杉木人工林树干茎流和穿透雨养分含量均表现季节动态变化。养分含量中,K^ 、Ca^2 、NO3%-浓度高,Na^ 、Mg^2 居中,HPO4^2-含量低,相对于林外雨,养分均出现富集化,但树干茎流养分富集化高于穿透雨。树干茎流出现强烈的酸化,而穿透雨酸化现象不明显。树种之间的茎流养分特征表现不一样,樟树和枫香总的养分浓度较高,其次为刨花楠,最后为青冈和红栲。     

Temporally-explicit models of fire and forest

Pollen and charcoal data from varved sediments of Lake Ahvenainen, southern Finland, were examined through ordination analyses to determine temporal groupings of vegetation. The ordination `continually' changed throughout the pollen profile, indicating nonequilibrium system dynamics. However, temporal associations that were stationary existed during the history of vegetation change at Lake Ahvenainen, and these temporal associations were nested in a hierarchy. Weighted averaging regression and calibration were used to model the relationship between fire and vegetation within each temporal association. Fire was significantly related to the vegetation for nearly all temporal associations. Community dynamics within temporal associations were examined with cross-correlation analysis. Taxa were correlated with fire occurrence (charcoal fragments) within the temporal associations and classic successional recovery was confirmed. In addition, two temporal associations showed evidence of chaotic behavior. The long-term pollen-charcoal analysis supported three theories of system dynamics: (1) nonequilibrium long-term dynamics, (2) hierarchical structuring of temporally stationary associations, and (3) chaotic dynamics in stationary associations. These theories are not necessarily contradictory, but are scale dependent.