常绿阔叶林演替过程中马尾松消退的原因

通过对浙江天童国家森林公园常绿阔叶林不同演替阶段的群落生态学调查,确认马尾松（ＰｉｎｕｓｍａｓｏｎｉａｎａＬａｍｂ．）属于常绿阔叶林演替过程中的消退种。为了揭示马尾松在群落演替过程中的消退原因,对各演替阶段群落中的生态因子,特别是光照强度的实地测定,得知马尾松群落内光照强度过低,常使马尾松更新苗处于光补偿点之下,难以正常生长。成树在演替过程中的衰退则是由于其它常绿阔叶树种,如木荷（ＳｃｈｉｍａｓｕｐｅｒｂａＧａｒｄｎ．ｅｔＣｈａｍｐ．）、栲树（ＣａｓｔａｎｏｐｓｉｓｆａｒｇｅｓｉＦｒａｎｃｈ．）等耐荫树种的抑制而使其物质合成能力逐渐减弱,物质分解能力逐渐加强,以致在常绿阔叶林演替的过程中逐渐消失。     

福建三明不同更新方式的米槠林物种多样性研究

本文从α多样性尺度总结三种不同更新方式的米槠林群落的物种多样性状况。结果表明,不同更新方式的米槠林群落中,物种丰富度、多样性指数和均匀度表现为天然更新> 人促更新> 人工造林。天然更新和人促更新米槠林是在皆伐迹上未经炼山发育起来的群落,而人工造林米槠林是从火烧迹地上发育的。天然更新米槠林处于演替的中级阶段,未达到顶级群落;而人促更新和人工造林米槠林则处于衰退阶段。     

天童国家森林公园废弃采石场植被自然恢复早期阶段的种群动态及生物量的研究

对天童国家森林公园废弃采石场植被自然恢复早期阶段的种群动态及生物量研究表明,采石废弃地植被自然恢复早期阶段的群落种类组成非常简单,只有木荷、马尾松两个种;两种群的密度动态趋势为先升后降,最大密度分别出现在３ 龄、４ 龄;马尾松地上部分生长速度明显高于木荷;群落中马尾松总生物量是木荷的１２ 倍多,木荷分配到叶和根中的生物量比例高于马尾松,而马尾松分配到茎中的比例高于木荷．这说明在采石迹地早期演替阶段马尾松以快速生长方式在竞争中处于优势地位．对采石迹地和砍伐迹地演替早期阶段的群落特性进行了比较,并对植被有效恢复进行了讨论     

亚热带不同演替树种米槠和马尾松细根性状对比研究

选择福建省三明市中亚热带演替前期树种马尾松和演替后期树种米槠两种人工林为研究对象,采用土芯法研究两个树种细根(直径2mm)的生物量及其垂直分布、形态以及分支结构等细根性状特征。结果表明:(1)0—80cm土层米槠的细根生物量密度(0.21±0.06)kg/m3、根表面积密度(3.15±1.25)m2/m3和根长密度(2202.84±517.03)m/m3分别为马尾松的1.6、1.2倍和2.2倍,并且3个指标均随土层深度增加而降低,但演替前期树种马尾松细根在土层间分布更均匀,而演替后期树种米槠细根更富集于表层。(2)马尾松细根的直径(0.86±0.04)mm、比表面积(191±32)cm2/g分别是米槠的1.4倍和1.3倍;米槠细根的比根长(10.73±0.46)m/g、组织密度(0.49±0.06)g/cm3分别是马尾松的1.4倍和2.0倍,马尾松细根的较大直径和低组织密度的形态结构能够迅速生长占领土壤空间和适应干旱环境,而米槠细根的较小直径、高比根长和较高的组织密度使其具有较强养分竞争能力和应对取食压力;(3)米槠的比根尖密度(4288±63)个/g、比分叉密度(1164±155)个/g均为马尾松的2.2倍,米槠细根的高分支系统能够迅速利用富养斑块。结论表明处于不同演替阶段的树种细根性状具有明显差异,可能反映了不同的资源获取策略。     

浙江天童国家森林公园常绿阔叶林主要组成种的种群结构及更新类型

 以浙江天童国家森林公园常绿阔叶林为对象,应用永久样方法和每木调查法调查了群落种类组成和结构,并对主要组成种的种群结构进行了分析。依据胸径级频率分布的形状,将各树种的种群结构归纳为5种类型,并结合生物学、生态学特征,分别讨论了其更新类型,同时对调查群落所处的演替阶段进行了诊断。结果表明：1）群落为6种共优势群落,出现木本植物69种。2）种群结构为单峰型的马尾松（Pinus massoniana）、枫香（Liquidambar formosana）和檫木（Sassafras tzumu）等为阳性高大乔木,无正常更新能力,更新类型是先锋群落优势种或是顶极性先锋种;间歇型的木荷（Schima superba）、黑山山矾（Symplocos heishanensis）和红楠（Machilus thunbergii）等为具有耐荫性的常绿阔叶树种,更新具有波动性和机会性,是演替系列或顶极群落优势种;逆-J字型的米槠（Castanopsis carlesii）、栲树（Castanopsis fargesii）和长叶石栎（Lithocarpus harlandii）等为强耐荫性的常绿阔叶树种,通过幼苗库和根萌生枝进行更新,是顶极群落的优势种;浙江新木姜子（Neolitsea aurata var. chekiangensis）、厚皮香（Ternstroemia gymnanthera）等为L字型;连蕊茶（Camellia fraternna）、老鼠矢（Symplocos stellaris）等为单柱型,此二型是群落亚乔木层和灌木层的主要组成种。3）调查群落已进入演替的顶极阶段,但仍处于其前期,将进一步向以米槠、栲树为主要优势种的方向发展。     

中亚热带不同演替阶段的马尾松和米槠人工林的细根生产量研究

对不同演替阶段的树种细根生产动态及其对环境因子响应的差异目前仍缺乏了解。为此, 在福建省三明市选择了中亚热带演替前期的马尾松(Pinus massoniana)和演替后期的米槠(Castanopsis carlesii)两种人工林为研究对象, 采用微根管法对两种人工林的细根根长生产量及其动态进行了为期2年的观测, 并分析了细根生产量的径级和土层分布, 及月生产量动态与气温、降水、土壤温度、土壤含水率等环境因子间的关系。结果表明: 1)两种林分的细根生产量有显著差异, 马尾松人工林细根年根长生产量约为米槠人工林细根年根长生产量的4倍; 两种林分的细根生产量呈现显著的月变化, 峰值均出现在夏季, 且2年内总细根生产量以夏季的细根生产量最大。2)两林分均是直径0-0.3 mm的细根所占细根生产量比例最大; 土层分布上, 马尾松人工林0-10 cm土层细根所占生产量的比例最大, 米槠人工林30-40 cm土层细根所占生产量比例最大。3)偏相关分析表明, 两林分细根月生产量均与气温、土壤温度极显著相关或显著正偏相关, 与降水、土壤含水率的偏相关均不显著; 一元线性回归分析表明, 演替早期马尾松人工林细根月生产量与气温、土壤温度的相关性明显高于米槠人工林。该研究表明, 与演替后期的米槠人工林相比, 中亚热带演替早期的马尾松人工林细根生产量大, 且与温度间的相关性更高。     

植被演替过程中种群格局动态的分形分析

该文根据“空间代替时间”的原则和对马尾松(Pinus massoniana)种群的重要值-平均胸径的变动趋势的分析,确定5个森林群落为广东省黑石顶自然保护区森林群落演替的一个时间序列;并在此基础上,运用分形理论的计盒维数和信息维数,对演替过程中马尾松种群空间格局的动态进行了分形分析。结果表明,马尾松种群的计盒维数和信息维数2个参数值均呈递减趋势,与其个体数、重要值变动趋势一致。在群落的演替过程中,马尾松种群的空间占据能力不断下降,种群呈衰退趋势。随其在群落中的优势地位逐渐被其它种群取代,群落将由以马尾松占绝对优势的单优群落演替为多优常绿阔叶林群落。分析结果同时表明,分形分析是群落演替过程中种群空间格局动态研究的有效方法,分形维数则能反映种群格局的尺度变化规律。     

米槠与杉木细根凋落物是否在自身群落中分解得更快?

本研究应用网袋法对福建省万木林自然保护区米槠（Castanopsis carlesii）、杉木（Cunninghamia lanceolata）细根在米槠林群落和杉木林群落交叉分解进行了为期2年的研究。结果表明,0-1mm、1-2mm米槠细根在米槠群落比在杉木群落分解速率快,而相同径级杉木细根在两群落分解差异较大。0—1mm杉木细根在杉木群落的分解速率高于米槠群落,而1—2mm杉木细根在杉木群落的分解速率只及米槠群落的48％。米槠、杉木细根在两群落分解的差异表明,群落立地条件对细根分解存在较大的影响。     

米槠与杉木细根凋落物是否在自身群落中分解得更快？

本研究应用网袋法对福建省万木林自然保护区米槠(Castanopsis carlesii)、杉木(Cunninghamia lanceolata) 细根在米槠林群落和杉木林群落交叉分解进行了为期2年的研究。结果表明, 0~1 mm、1~2 mm米槠细根在米槠群落比在杉木群落分解速率快, 而相同径级杉木细根在两群落分解差异较大。0~1 mm杉木细根在杉木群落的分解速率高于米槠群落, 而1~2 mm杉木细根在杉木群落的分解速率只及米槠群落的48％。米槠、杉木细根在两群落分解的差异表明, 群落立地条件对细根分解存在较大的影响。     

鼎湖山马尾松群落演替过程物种变化之研究

在永久样地定位调查的基础上,研究鼎湖山森林植被马尾松群落在十几年演替中种群结构和群落结构的变化．研究结果表明,随着演替的进展,其群落中的乔木种类增多,由４种增至７种．群落的组成结构趋向优化：群落的多样性趋于增加,物种多样性指数由０．５８增到１．６０;群落增加其均匀度,均匀度指数由０．２９增大至０．６９;生态优势度指数由０．８３变为０．３８．十四年的演变明显地改变群落中的优势种的种群结构．先锋性的群落发生种马尾松种群尽管仍是优势种,但消亡的趋势明显;地带性的顶极建群种,如荷木等大大的发展,群落加速向混交林的方向发展演变．     

Plant community establishment in a restored wetland: Effects of soil removal

Question: This study investigated the establishment of wetland plant assemblages following soil removal and restored hydrology in a former agricultural field. The following questions were posed. Does plant community composition differ as a result of soil removal? Does soil removal reduce the frequency of non-wetland plants? Does soil removal reduce the frequency of non-native invasive plants? Location: The Panzner Wetland Wildlife Reserve (PWWR) in Summit County, northeastern Ohio, USA. Methods: During 2000–2001, restoration was conducted on two adjoining fields (3.9 ha total) by excavating the upper 40–50 cm of soil layer and establishing 12 10 m × 10 m undisturbed control plots. Preliminary data included seed bank composition and soil organic matter, estimated from three different soil depths on the control plots. In spring 2004, a 10 m × 10 m soil-removed plot was established adjacent to each control plot. Plant percent cover of all species was estimated within the center 5 m × 5 m of every plot. Above-ground biomass of all species from three 0.25-m² quadrats was collected. Environmental water measurements included water depth, temperature, dissolved oxygen, pH, and conductivity. Results: The top 10 cm of soil contained the most seeds, the highest species diversity, the greatest proportion of annual to perennial plants, and the lowest organic content. Obligate and facultative wetland plants were found in soil-removed plots while facultative upland and upland plants were found in control plots. The only plots with arable weeds were the control plots. However, plant communities on soil-removed plots in the North field, which had a higher elevation (ca. 15–20 cm), had a different species composition than soil-removed plots in the South field. Conclusions: The results of a controlled, replicated large-scale study on the effects of soil removal showed that soil removal altered both the biotic and abiotic environment, but that the proximity to the water table was the primary controlling factor in the assembly of plant communities.     

Seeding tallgrass prairie in monospecific patches promotes native species establishment and cover

In tallgrass prairie reconstruction, the way desired seeds are arranged on the landscape may affect species establishment, species persistence, and the establishment and persistence of undesired (nonseeded) species from the local propagule pool. To test effects of species seeding pattern on how grasslands develop spatially, we seeded 20—4 × 4–m bare soil plots with 16 tallgrass prairie species. Treatment plots were divided into 16—1 × 1–m subplots, 64—0.5 × 0.5–m subplots, 256—0.25 × 0.25–m subplots, or 1,024—0.125 × 0.125–m subplots. Each species was hand broadcast into separate subplots (1 m² total area/species) within each plot. An additional treatment included uniformly mixing and broadcasting all seeds across a plot. We recorded species cover at the 0.125 × 0.125–m scale within each plot at the beginning of the second and third growing seasons. While species persistence was greatest within plots seeded with larger subplots, plots with smaller subplots were more spatially diverse and less occupied by nonseeded species over time than larger subplot and mixed plots. As is common in reconstruction efforts, establishment was variable among species and seeding with monospecific subplots enhanced colonization of desired rhizomatous species (e.g., Heliopsis helianthoides, Monarda fistulosa, Elymus virginicus) into unoccupied locations at the expense of species from the local propagule pool. Results suggest that seeding species in smaller, monospecific patches could result in grasslands with a more balanced native species composition than those established with a seed mixture approach.     

种群分布格局测定的样方尺度效应

以粤西黑石顶自然保护区西部船底窝的永久样地为研究对象,在一个面积为1600m2的人工次生裸地样地上,借助地理信息系统(GIS)技术,对各个种群分别用3种不同的样方面积(10m×10m,8m×8m,5m×5m)和不同的测定方法来研究演替初期优势种群的分布格局,从而研究不同的样方面积对测定南亚热带森林群落内种群分布格局的影响。结果表明,在南亚热带森林群落演替初期以8m×8m的样方面积来测定种群分布格局较为有效。同时运用GIS技术作数据处理及图形输出,大大简化了分析过程,提高了分析水平。     

Impact of habitat disturbance in the wetland forests of East Usambara,Tanzania

We evaluated habitat characteristics of East Usambara wetland forests. The abundance and species composition in the tree, shrub and herbaceous layers were enumerated in two sets of nested plots, one set in a natural wetland forest and the second in a wetland forest that had been disturbed by small‐scale gold mining activities. Each set had thirty‐six 1 m × 1 m plots for herbs, inside nine 5 m × 5 m plots for shrubs, in three 20 m × 20 m plots for trees. The habitat profile of herbaceous – shrub – tree layers was found to be sharply different from one obtained in previous studies at the surrounding nonwetland forests as were species composition and abundance. Unlike in the nonwetland forests, the herbaceous layer was thick, the shrub layer very thin and the woody species density and richness much lower. Disturbance significantly reduced woody cover and changed species composition in the herbaceous layer. Recovery of the woody vegetation was low. Wetland forests in the East Usambaras form a small fraction of the total area, but they are a unique biodiversity repository, they appear to be an important carbon dioxide sink and to reserve and purify water. They are sensitive to disturbance and need protection.     

Restoration of a Landfill Site in Berlin, Germany by Spontaneous and Directed Succession

We report on spontaneous and directed succession on a dry sandy landfill site of low fertility at Berlin‐Malchow, Germany. Changes in species composition and cover were followed on unmown and mown permanent plots of 2 × 2 m size through 5 years of vegetation development. Species richness on unmown plots was relatively constant during the time of observation, with 20 to 25 species per 4 m². Total cover of unmown plots continuously increased from approximately 10% in the first year to 80% in the fifth year. There are no clearly discernible sequential successional stages until present. The species composition includes species of all life forms, which colonized the site immediately after the initiation of the succession process representing the initial floristic composition type of vegetation development. However, perennial grasses and herbs gradually increased in cover up to approximately 40%. Woody plants were also present from the first year of succession and increased up to more than 20% cover in the fifth year, forming a shrub layer (>0.5 m) after the second year. Mowing significantly increased species richness, which was evident from the third year onward. This effect was mainly due to the reduction of the tall perennial grass Calamagrostis epigejos. Solidago canadensis and woody species were also significantly affected (lower cover and height), whereas short perennial herbs like Plantago lanceolata and Trifolium repens benefited from mowing.     

Abundance and dispersion of some chimpanzee-dispersed fruiting plants at Mahale, Tanzania

Abundance and dispersion of five fruiting plant species the seeds of which are commonly dispersed by chimpanzees were investigated at Mahale Mountains National Park, Tanzania from August 2000 to February 2001. All plant individuals encountered within twenty‐three 50 × 50 m plots were counted and allocated to demographic stages. Plots were allocated proportionally to the main vegetation types in the chimpanzee range. Density and the demographic stages of individuals within 50 m radii of 10 adult conspecifics for four of the five sample species were also investigated. Overall, densities of individuals varied greatly by species and growth stages within the chimpanzee ranging space. Dispersion of the five plant species tested, irrespective of growth stages, showed a clumped pattern. However, Saba comorensis was the most evenly dispersed, irrespective of growth stage. Densities of juveniles and adults generally declined away from adult conspecifics, except for Syzygium guineense. These results are discussed in view of chimpanzees as potential seed dispersers. The hyper‐dispersion of S. comorensis appears to mirror the profound intensive and extensive dispersal of its seeds by chimpanzees, which are the main eaters of this fruit in the study area.     

Causes of plant community divergence in the early stages of volcanic succession

Question: How do temporal changes in plant communities occur after volcanic eruptions? What characteristics determine successional divergence or convergence? Location: The summit area of Mount Usu, northern Japan, completely destroyed by 1‐3 m of thick ash and pumice during the 1977‐1978 eruptions. Habitats were classified into three types: gullies where the pre‐eruption topsoil was exposed due to the erosion of tephra (EG), gullies covered with tephra (CG), and outside of gullies covered with thick tephra (OG). Methods: Plant community structure was monitored for 15 years from 1983 to 1997 in 14 2 m × 5 m permanent plots. The data were summarized by species diversity, life form, and the detrended correspondence analysis. Results: The common species were perennial herbaceous plants, but habitat preferences differed between species. Seed bank species, including a nitrogen fixer Trifolium repens, were dominant in EG, and excluded the establishment of the later colonists. Pioneer trees slowly increased in cover. The detrended correspondence analysis indicated that species composition in the earlier stages did not differ greatly between plots. Thereafter, three patterns of temporal community changes were observed: seed bank species persisted in EG, and in OG and CG forest development proceeded or community structure did not change greatly. Conclusion: Pre‐eruption topsoil contributed to revegetation by the supply of seed bank and nutrients in the earliest stages, but resulted in the delay of forest development due to the persistence of seed bank species. Plant community divergence was driven by the persistence of earlier colonists.     

Species richness and species turnover in a successional heathland

Abstract. Changes in species richness and species turnover during secondary succession following experimental disturbance were studied in eight permanent plots in a species‐rich dry heathland in the southern part of the Czech Republic. The treatments applied were sod‐cutting, burning, cutting of above‐ground biomass, and control. The plots were sampled annually between 1992 and 2000; species richness was analysed at three scales, 25 cm × 25 cm, 1 m × 1 m, and 3 m × 3 m. Disturbances resulted in increased species richness. The highest vascular plant richness was attained during the secondary succession after sod‐cutting, where species established on exposed bare ground. Less severe disturbances by burning and cutting also caused a slight increase in the number of vascular plant species. For bryophytes and lichens, the highest increase in the number of species was also found in the sod‐cut plots, where all cryptogams were removed by the disturbance. At the scale of 3 m × 3 m, species richness of both vascular plants and cryptogams peaked in 1995–1996, i.e. 3–4 yrs after the disturbance, and slowly decreased or slightly fluctuated without any trend thereafter. At smaller scales it either peaked later or constantly increased over the entire observation period of 9 yrs. Species mobility, expressed as species accumulation over time, was lower than reported from grasslands. Rates of species turnover, calculated as Jaccard dissimilarity between pairs of consecutive years, corresponded across different scales. This implies that successional dry heathlands have a higher small‐scale mobility than heathlands which are apparently stable at larger scale.     

Sampling Techniques Influence Understory Plant Trajectories After Restoration: An Example from Ponderosa Pine Restoration

Abstract Although there is no one correct technique for sampling vegetation, the sampling design chosen may greatly influence the conclusions researchers can draw from restoration treatments. Considerations when designing vegetation sampling protocol include determining what sampling attributes to measure, the size and shape of the sampling plot, the number of replicates and their location within the study area, and the frequency of sampling. We installed 20 point‐intercept transects (50‐m long), 8 belt transects (10 × 50 m), 10 adapted Daubenmire transects (four 0.5 × 2‐m plots), and 4 modified‐Whittaker plots (20 × 50 m with smaller nested plots) in treatment and control units to measure understory herbaceous response in a forest restoration experiment that tested different treatments. Point‐intercept transects on average recorded at least twice as much plant cover as did adapted Daubenmire transects and modified‐Whittaker plots taken at the same location for all control and treatment units. Point‐intercept transects and adapted Daubenmire plots on average captured fewer rare and exotic species in the control and treatment units in comparison with the belt transects and modified‐Whittaker plots. Modified‐Whittaker plots captured the highest species richness in all units. Early successional understory response to restoration treatments was likely masked by the response of the herbaceous community to yearly climatic variation (dry vs. wet years). Species richness and abundance were higher in wet years than dry years for all control and treatment units. Our results illustrate that sampling techniques can greatly influence perceptions of understory plant trajectories and therefore the interpretation of whether restoration goals have been achieved. In addition, our results suggest that restoration monitoring needs to be conducted for a sufficient length of time so that restoration treatment responses can be detected.