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.     

大兴安岭呼中林区虫害与火干扰交互作用的长期模拟

虫害和林火是森林生态系统的两种主要干扰类型,各种干扰在大时空尺度上存在一定的交互作用.本文采用空间直观景观模型LANDIS模拟虫害和林火在300年内的交互作用.结果表明:虫害干扰降低了细可燃物载量,提高了模拟前期(0～100 a)和中期(100～200 a)的粗可燃物载量,降低了模拟前期和中期的林火频率,不同干扰预案模拟后期(200～300 a)火烧频率的结果比较接近;虫害干扰降低了模拟前期和后期的火烧强度,增加了模拟中期的火烧强度,提高了模拟中期的森林火险等级,降低了模拟前期和后期的火险等级.人类灭火可增加虫害的发生面积,因此建议森林管理部门采取适当的防虫措施,不可只注重灭火,可以采取可燃物去除和计划火烧等方式管理林火,促进森林生态系统的可持续发展.     

林窗干扰研究

林窗是森林生态系统中一种普遍存在的现象,无论是健康的系统还是已经受到过度干扰的系统,林窗作为森林生态系统发展的重要驱动力,影响着森林的物种组成、结构以及森林的演替方向。因此,林窗研究能够为受干扰森林生态系统的恢复提供理论指导,并为森林生态系统的管理提供科学依据。本文从总结有关林窗的基本理论入手,重点介绍了近年来对林窗概念、基本特征、林窗产生后的生境条件变化以及生物对林窗环境变化的响应等研究概况,并对目前林窗研究的手段以及热点问题进行了总结,以期为今后的相关研究提供参考。     

青海麦秀林场紫果云杉次生林的干扰重建

对青海麦秀林场2个50m×50m紫果云杉(PiceapurpureaMast.)样方调查和604株树木年轮系统及157个树桩的分析结果表明:2个样方的干扰强度总体都较高,如PⅠ样方1950′s达到31.4% 10a,PⅡ样方1980′s达到18.1% 10a,说明存在经常性的择伐或盗伐活动,设定近30a来实际发生的干扰强度用树桩断面积与树桩和树木断面积的百分率来表示,并与用树轮分析的干扰重建百分比相比较,结果发现具有正态树龄分布的PⅠ样方的重建值与实际值较为接近,而不具有正态树龄结构分布的PⅡ样方,其重建值明显高于实际值。     

Arthropod Assemblages in Epiphyte Mats of Costa Rican Cloud Forests

Tropical cloud forests are functionally important ecosystems, but are severely threatened due to deforestation and fragmentation. Epiphyte mats, accumulations of live vegetation and dead organic matter on tree trunks and branches, are a conspicuous component of cloud forests and harbor diverse assemblages of meso- and microarthropods. We compared the morphospecies richness, composition, and abundance of arthropods in epiphyte mats between primary and secondary forests of Monteverde, Costa Rica, and at two nearby replicate sites. Epiphyte mats were thinner and less structurally diverse in secondary forest. We collected ca 36,000 micro- and mesoarthropods from epiphyte mats in the 2-yr study. Whereas arthropod morphospecies richness did not differ among forest types, arthropod abundance was significantly higher in secondary forest due to larger numbers of ants, especially Solenopsis spp. Arthropod assemblages showed a high degree of taxonomic overlap both within and between primary and secondary forests (Jaccard abundance-based similarity = 0.93–0.96). Although characteristics of the arthropod fauna proved to be similar among sites and between forest types, there was a significant temporal effect: arthropod morphospecies richness in epiphyte mats generally was lower in the dry season (February–May), when many taxa probably became dormant or sought shelter against desiccation in deeper portions of mats.     

Forest succession in Kibale National Park, Uganda: implications for forest restoration and management

Forest succession was studied in four plots in former grasslands at the Ngogo study area in Kibale National Park, Uganda. The plots were located in areas that had been protected from fire for 0.58, 25, 9 and ≈30 years for plots 1, 2, 3 and 4, respectively. Species richness reflected the length of time that the plot had been protected from fire; it was highest in plot 4 and lowest in plot 1. Species density, stem density and basal area were all highest in plot 4 and lowest in plot 1. The species densities of plots 2 and 3 were not different. Similarly, plots 2 and 4 did not differ with regard to stem density or basal area. Animal seed dispersers played a vital role in the colonization of grasslands by forest tree species.     

森林木质藤本数量过度增长的机制与生态效应

木质藤本是维持森林物种多样性的组成部分。近年来，热带、亚热带森林尤其是次生林内的木质藤本数量的过度增长给森林的恢复和健康发展造成了威胁。至今，国内尚少有研究对森林木质藤本过多的现象、增长机制与生态效应进行综合认识。该文梳理国内外相关文献，从木质藤本数量增长的机制与生态效应进行分析和总结，综合相关研究认为：(1)木质藤本数量的增长与干旱化加剧、大气CO₂浓度上升、自然干扰和森林破碎化有关，在环境变化的情况下，木质藤本在形态、行为、生理等方面比树木更具优势，表现为更快的生长速率、更强的繁殖力和可塑性以及资源利用效率。(2)木质藤本主要通过遮荫胁迫、资源竞争和机械压力与损伤等方式对树木造成影响。(3)木质藤本过度增长在个体水平上会阻碍树木生长、生殖并引起树木死亡，在群落水平上会改变物种组成、降低多样性，在生态系统水平上会降低森林碳储量，改变碳、矿质养分和水分循环过程等。因此，建议结合野外长期监测与控制实验开展木质藤本数量动态与环境变化关系、森林干扰对木质藤本生长的影响、木质藤本对环境变化的响应及适应机理、木质藤本数量过度增长的生态效应评价研究。同时，应积极探索合理的森林...     

森林退化/衰退的研究与实践

森林退化可以理解为森林面积减少、结构丧失、质量降低、功能下降;森林衰退则是森林退化的一种形式,指森林（树木）在生长发育过程中出现的生理机能下降、生长发育滞缓、生产力降低甚至死亡,以及地力衰退等状态.国内外研究表明,森林采伐/毁林是造成森林面积减少的最主要原因,有关森林采伐/毁林引起的森林退化研究主要集中在森林退化的后果、国家/国际政策的影响、加强全球性合作以及寻求解决途径等方面.森林衰退原因可归纳为：工、农业污染,自然胁迫/致衰因子,林分动态发生变化,森林衰退病或生态病,人工纯林以及纯林连栽导致的地力、生产力衰退等.中国的森林退化/衰退现状与世界各地森林退化基本一致,但由于历史原因,中国森林退化又有其自身特点：近一个世纪的强烈人为干扰,使大部分原始天然林退化为次生林;中国拥有世界上最多的人工林,且多数人工林均具有质量差、功能低等衰退特征.本文在综述森林退化/衰退研究与实践基础上,提出中国现代森林退化/衰退的的主要原因,给出中国森林退化/衰退的基本对策.     

Survival estimates of bird species across altered habitats in the tropical Andes

The probability of long‐term persistence of a population is strongly determined by adult survival rates, but estimates of survival are currently lacking for most species of birds in the tropical Andes, a global biodiversity hotspot. We calculated apparent survival rates of birds in the Ecuadorian tropical Andes using a moderately long‐term (11 yr) capture–recapture dataset from three habitats that varied in how much they had been modified by human activities (native forest, introduced forest, and shrubs). We fit mark–recapture models for 28 species with habitat as a covariable. For all species, recapture rates between sampling sessions were low and varied from 0.04 for Rainbow Starfrontlets (Coeligena iris) to 0.41 for Stripe‐headed Brushfinches (Arremon assimilis) when averaged across all occupied habitats. Annual survival rates varied from 0.07 for Black‐crested Warblers (Margarornis squamiger) to 0.75 for Violet‐throated Metaltails (Metallura baroni). We found no significant differences in survival rates either among habitats or species grouped by habitat specialization. Because we found similar survival rates in native forest and human‐modified habitats, our results support those of recent studies concerning the potential value of secondary habitats for the conservation of some species of birds in the tropics. However, our conclusions are tempered by the uncertainty around the estimates of survival rates. Despite the relatively long‐term nature of our study, obtaining survival estimates for bird species in this region was challenging, and either more years of study or modification of field protocols may be needed to obtain more precise survival estimates.     

Fire Scars on Amazonian Trees: Exploring the Cryptic Fire History of the Ilha de Maracá

The presence of charcoal in the soils and fire scars on 8.2 percent of tree stems strongly suggest that one of the best studied Amazonian research localities (the Ilha de Maracá in Roraima, Brazil) has burned. The patterns and images of fire scars that we present here could help researchers explore the burn history of other tropical forests, which has important implications for interpreting their present-day ecology.     

Ecological study of pseudoscorpion fauna in the soil organic layer in managed and abandoned secondary forests

We surveyed pseudoscorpion fauna in the soil organic layer in managed and abandoned secondary forests in Hiroshima Prefecture, Japan, and studied the effects of forest management on the pseudoscorpions. The vegetation structure was generally more developed in abandoned stands than in managed stands. The depth of the soil organic layer was not significantly different between the two stand types. We observed a total of seven pseudoscorpion species belonging to five genera. Pseudoscorpion species richness and densities were higher in abandoned stands than in managed stands. We did not find any pseudoscorpions in stands where the summed vegetation cover was less than 150%.An erratum to this article can be found at     

Growth Rates of Tree Height Six Years after Hurricane Damage at Four Localities in Eastern Nicaragua1

Growth rates for 44 species of trees in a posthurricane forest in Nicaragua were measured. The pattern is consistent with the interpretation of succession as a two stage process: an initial building phase after the hurricane followed by a thinning phase. Localities that were damaged less from the hurricane are now entering the thinning phase of postdisturbance succession, while those subjected to the most severe damage appear to remain in the building phase.     

中亚热带常绿阔叶林林隙及其自然干扰特征的研究

通过对福建万木林中亚热带常绿阔叶林中96个林隙的调查,研究了中亚热带常绿阔叶林的基本特征和自然干扰规律,结果表明,在中亚热带常绿阔叶林中,扩展林隙(EG)和冠空隙(CG)在中亚热带常绿阔叶林景观中的面积比例分别为50．86％和16．66％,每年干扰频率分别为0．85％·年^-1和0．28％·年^-1,林隙干扰的返回间隔期约为357年．林隙形成方式由树木折干形成的最为普遍,占形成木总数58．04％。其次是由于掘根风倒而形成的,占33．48％．林隙大多由两株树木形成,平均每个林隙拥有形成木2．33株．扩展林隙的大小多在100～300m^2之间,其中以200～300m^2者所占的面积比例最大,而以100～200m^2者所占的数量比例最大,冠空隙的大小多在100m^2以下,其中50m^2以下所占的数量比例和面积比例都是最大的．林隙形成木分布最多的径级在20～30cm之间。     

林火干扰对广东木荷林生态系统碳库的影响

森林碳库在调节CO₂浓度及减缓温室效应中发挥重要作用。选择广东木荷林为研究对象,通过相邻样地法,进行植被生物量、凋落物生物量和土壤样品的采样与分析,研究不同林火干扰强度对生态系统各碳库(植被、凋落物和土壤有机碳)及生态系统碳库产生的变化规律和空间分布格局及其影响因素。结果表明:(1)植被碳密度随着林火干扰强度增强而减少,但不同组分的植被碳密度表现不同,乔木碳密度在不同林火干扰强度下变化与植被碳密度变化一致,而草本碳密度则呈现相反的变化趋势。相同林火干扰强度下,植被各组分碳密度均以乔木层降低幅度最大。林火干扰均显著降低了凋落物碳密度(P<0.05),并随林火干扰强度的增加其降低幅度增大,但不同林火干扰强度对凋落物碳密度的影响有所差异。林火干扰降低了土壤有机碳密度,且降低幅度随土层深度增加而逐渐变小。(2)林火干扰有效改变了生态系统碳库的空间分布格局。对照样地木荷林土壤有机碳库占比为61.59%,重度林火干扰后,土壤有机碳库占比为70.96%呈上升趋势,占生态系统碳库的优势地位,而植被和凋落物碳库占比呈下降趋势,处于生态系统碳库的次要地位。(3)双因素方差分析表明,林火干扰强度和土层深度及其交互作用均对土壤有机碳密度有显著影响。林火干扰强度解释了土壤有机碳密度变异的8.78%,土层深度解释了土壤有机碳密度变异的70.29%,林火干扰强度和土层深度之间的交互作用解释了土壤有机碳密度变异的8.16%。研究发现:林火干扰降低了生态系统碳库,且随林火干扰强度增加,生态系统碳库减少幅度增大。轻度林火干扰对森林生态系统碳库的影响差异不显著,而中度和重度林火干扰对森林生态系统碳库的影响差异显著。研究结果对深化亚热带森林固碳效应的影响机制提供理论支撑。     

中国东部常绿阔叶林退化群落分析及恢复重建研究的一些问题

人类干扰活动导致常绿阔叶林的类型和数量减少,替而代之的是大面积处于不同退化程度的次生林、次生灌丛等,因此加大对其退化特征以及恢复重建的研究已是非常必要而迫切的任务。在对此类植被进行广泛调查基础上,结合数量分类法(在区域尺度上)对退化常绿阔叶林进行类型划分和群落特征的界定,并对一些影响群落恢复和改造的问题进行了讨论。这些问题是(1)不同的人类干扰方式对常绿阔叶林退化群落的形成发生深刻的影响,因此关注人类干扰方式,尤其是土地利用方式的变化和常绿阔叶林退化群落形成之间的关系应当进行重点研究;(2)退化群落的种类组成具有自身的特征,同样具有较高的物种多样性,对维持整个地区的物种多样性具有独特的贡献;(3)萌枝更新对退化群落的结构和动态起着重要作用,加强这方面的研究有助于探讨群落退化的机制和植被恢复途径;(4)种子传播方式、传播距离对于退化群落的种类组成具有重要影响,并影响到群落结构、动态和物种多样性,也应是进一步加强的研究领域。希望通过这些问题的研究,有助于明了群落的退化机理,并为其恢复改造提供依据。     

天然林生态系统稳定性与病虫害干扰——调控与被调控

如何评价天然林中原生的昆虫、病原的生态功能是制定病虫害防治措施首先要明确的问题之一。依据天然林生态系统稳定性与病虫害干扰之间关系的最新研究进展,系统阐述了当前有关天然林调控病虫害爆发的多样性-稳定性假说和联合抗性假说,指出联合抗性假说的不确定性以及多样性-稳定性假说的局限性。昆虫、病原在天然林演替过程对系统整体结构、健康、稳定以及可持续性上不但发挥着重要的生态调控功能作用,在有些情况下甚至加速或改变系统的演替途径。这种生物干扰目前在林业发达国家的天然林管理策略中被视为有益的干扰元素,由此提出将模拟自然干扰作为今后天然林管理策略一项指导方针。同时指出我国对此的认识不仅较国外林业发达国家晚,而且在实践中也未能有效地整合在森林生态系统健康管理的实践中,因此这种对天然林生物干扰的新认识有助于未来我国天然林病虫害生态控制治理决策的制定。     

Seed bank and vegetation composition of forest stands of varying age in central Belgium: consequences for regeneration of ancient forest vegetation

Vegetation composition differs significantly between ancientand recent forest, due to slow colonization capacity of typical forest speciesand the higher abundance of early successional species in recent forest.However, little is known about differences in persistent seed bank compositionbetween ancient and recent forest and about the interaction between seed bankand vegetation in relation with forest age. We surveyed the seed bank and theunderstorey vegetationcomposition in transects from ancient to recent forest. Seed bank and fieldlayer vegetation characteristics and similarity between seed bank andvegetationwere analysed in relation to recent forest age and distance to the ancientforest. A total of 39 species and 14,911 seedlings germinated, whichcorresponds with a seed density of 12,426 seeds/m².Total seed density is significantly higher in the youngest recent forest parcel(55 years). Also the seed bank composition in the youngest forest parceldifferssignificantly from the other parcels. After a longer period of reforestation,the seed bank approaches that of the ancient forest, suggesting seed bankdepletion, although the seed bank is permanently replenished to some extent byseed bank forming species from local disturbances. Seed bank composition doesnot change significantly with distance to the ancient forest. Similaritybetween seed bank and vegetation composition, nomatter the forest age, is very low, but decreases with increasing forest age.The most frequent species in the vegetation are absent in the seed bank andvice versa. The contribution of forest species is highin the vegetation and they almost not occur in the seed bank, while species offorest edges and clearings, and species of disturbed environments are morefrequent in the seed bank. The seed bank is mainly composed of earlysuccessional species of former forest stages or species which temporary occurinsmall-scale disturbances. The seed bank may enhance the negative effects ofearlysuccessional, mainly competitive species to the forest species richness in therecent forest. In this respect, forest management should minimise forestdisturbances, to prevent germination of competitive species form buriedseeds.     

Prevalence of Tree Regeneration by Sprouting and Seeding Along a Rainfall Gradient in Hawai'i

Drought stress in tropical dry forests is thought to result in greater asexual regeneration via vegetative sprouting ( e.g ., basal, root, and branch layering) than occurs in moister tropical forests. We tested this hypothesis by examining the prevalence of tree sprouting and seeding in tropical forests located along a rainfall gradient on the island of Hawai'i. Additionally, we examined the potential for novel disturbance, feral pig Sus scrofa rooting and trampling, to alter patterns in tree regeneration mode. We found greater sprouting (in terms of relative density and basal area) in dry forests than in mesic and wet forests, supporting the hypothesis. We also found that feral pig disturbance is negatively correlated with the relative density and basal area of seedlings in wet forests, but is positively correlated with the relative importance of sprouting, and the richness and diversity of sprouting species. Our results suggest rainfall regimes may be an important factor controlling broad-scale patterns in tree regeneration mode, and that exotic ungulates can significantly modify such patterns with potential consequences for the structure and dynamics of tree populations and communities.