辽东山区次生林乔木幼苗组成及其年际动态

为了解辽东山区次生林乔木幼苗组成及其年际动态, 本文以4 ha动态监测样地为平台, 对样地内1,600个 5 m × 5 m样方进行监测。依据2014-2016年连续3年的调查, 对样地内乔木幼苗的组成、高度分布、新增和死亡年际动态、空间分布格局等进行分析。结果表明: (1)调查期间共记录到22种乔木幼苗, 3年间幼苗组成没有发生变化, 但各个样方间出现极大差异, 并且幼苗优势树种组成与样地内优势树种成分保持着一定的相似性。(2)幼苗数量在不同树种和年际间表现出较大的差异: 花曲柳(Fraxinus rhynchophylla)、色木槭(Acer mono)、胡桃楸(Juglans mandshurica)在3年间幼苗数量最多, 占幼苗总数的75.6%; 花曲柳和胡桃楸幼苗数量表现出较明显的年际波动, 其他树种波动较小, 不同树种的幼苗密度差异很大。(3)幼苗新增和死亡存在明显的种间和年际差异: 2014-2015年间幼苗的新增数量(3,888)明显高于2015-2016年间(1,710), 同时2014-2015年间幼苗死亡率(23.7%)也明显高于2015-2016年间(12.7%)。对2015-2016年间新增幼苗和已有幼苗的死亡情况进行比较可以发现, 新增幼苗总体死亡率(18.8%)明显高于已有幼苗(8.1%)。(4)对比幼苗和大树的空间分布可以发现, 样地内优势幼苗都表现出集群分布的特征。在空间分布上, 幼苗与母树保持一定的相似性。     

雪灾后粤北山地常绿阔叶林优势树种幼苗更新动态

对遭受2008年雪灾破坏的车八岭山地常绿阔叶林进行连续3 a(2008-2010年)的监测,研究在冠层恢复过程中优势树种的林下幼苗动态,旨在了解幼苗灾后的更新规律及其对冠层结构变化(以叶面积指数LAI的变化来表示)的响应。结果表明,12个优势种的林下幼苗对冠层恢复有明显的响应。非参数的多元方差分析(perMANOVA)显示,优势种幼苗的组成和分布存在着极显著的年际差异(P<0.001);其中2008年与2009年及2010年的差异均极显著(P<0.001);2009年与2010年的差异不显著。这与冠层LAI的变化情况相应:2008年LAI最低,2009年LAI值迅速增加;2010与2009年相比LAI增长缓慢,并逐渐趋于稳定。不同的优势树种幼苗对样方中LAI变化的响应不同,阳性树种幼苗的相对多度和频度一般会随林分郁闭度的增加而锐减,阴性及耐阴树种幼苗数量则随冠层恢复而增加。随着冠层恢复,林下指示种截然变化。2008年的林下幼苗指示种为8个喜光的种类,而2010年则仅见较耐阴的香楠Randia canthioides 为指示种。指示种分析从另一个角度反映了幼苗对冠层恢复的响应。     

长白山阔叶红松林乔木树种幼苗组成及其年际动态

为了解阔叶红松(Pinus koraiensis)林乔木树种幼苗的组成及其年际动态, 以长白山阔叶红松林25 ha动态监测样地为平台, 在样地内150个种子收集器周围设置了600个5 m×5 m幼苗样方。基于2006–2008年连续3年的幼苗样方调查数据, 对乔木幼苗的树种组成、数量组成、空间分布特征、年际动态、新增和死亡幼苗组成等进行了分析。结果表明: (1)从树种组成来看, 该群落乔木树种的幼苗组成种类较为丰富, 共记录到21个树种, 这些树种也是样地内胸径1 cm以上乔木树种的主要组成成分。树种组成在年际间变化不大, 但各样方间表现出极大的空间变异。(2)从数量组成来看, 共记录到11,959株乔木幼苗, 以水曲柳(Fraxinus mandshurica)和紫椴(Tilia amurensis)幼苗数最多, 占总幼苗数的72.75%; 水曲柳、紫椴和红松的幼苗数量在年际间有明显波动, 其他树种年际间波动较小。(3)从新增和死亡幼苗的数量与组成来看, 共记录到15个乔木树种的新增幼苗, 其中紫椴、水曲柳、色木槭(Acer mono)、红松等10个树种在每次调查中都有新苗记录, 新苗数量在年际间随物种和样方位置表现出明显差异。(4)对各树种的幼苗、种子和大树的组成和空间分布的比较发现, 各树种的幼苗、种子和大树之间的数量组成和比例差异较大, 其中紫椴、水曲柳、色木槭和假色槭(A. pseudo-sieboldianum)的幼苗、种子在整个样地内都有分布, 春榆(Ulmus japonica)和怀槐(Maackia amurensis)幼苗的空间分布与种子和大树不一致, 糠椴(T. mandshurica)和山丁子(Malus baccata)等的幼苗、种子和大树的个体数相对都较少, 且它们的分布是一致的。     

山西灵空山天然松栎混交林群落特征与冠层结构

以2011年建设的山西灵空山4 hm²天然松栎混交林森林动态监测样地为研究平台,以400个10 m×10 m样方为测量单元,于2016年进行群落特征研究,采用半球面影像法(DHP)分析冠层结构和林下光照特征.结果表明: 样地内共有乔木5558株,共计25种,分属于10科15属.冠层开阔度(CO)集中在15.0%～25.0%,叶面积指数(LAI)集中在1.5～2.5,林下光环境参数集中在10.0%～30.0%.建群种在样地内的分布对冠层结构和林下光环境影响显著;冠层结构对林下光环境所有参数的影响方向一致,其中采用叶面积指数评价冠层结构动态的效果更佳;冠层开阔度和叶面积指数对林下光环境产生相反的影响,且均对散射光入射率影响程度最大.温性松栎混交林的林冠层整体较为均匀,林下光分布较为集中,林分树种组成与冠层结构对林下光照影响显著.     

关帝山寒温性云杉次生林样地树种组成、结构和空间分布

云杉次生林是关帝山的优势森林植被类型,也是华北亚高山地区寒温性常绿针叶林的代表类型.为更好地了解其物种组成、群落结构等基本特征及其潜在的生态学过程和机制,于2010年在关帝山庞泉沟国家自然保护区建立了4 hm²的云杉次生林固定监测样地(GDS样地).本文以第一次本底调查数据为基础,分析了样地树种组成、结构和空间分布.结果表明: 样地共有木本植物30种,隶属于11科22属.包括分枝的总个体数为26218(其中独立个体数为10266).植物区系组成属北温带成分;不同树种个体数、平均胸径和胸高断面积差异较大,导致群落成层分明,各层优势种明显.乔木层第一亚层树种径级结构呈双峰偏正态分布,乔木层第二亚层树种径级呈近似正态分布,灌木层树种径级呈“L”型分布.乔木优势树种青杄和华北落叶松的空间分布无论在个体数量还是聚集程度上均随径级变化而呈现不同的格局特征.相同径级的两树种,胸径(DBH)≥30 cm的华北落叶松在样地居多且聚集分布于样地中部,而DBH≥30 cm的青杄则相对较少,没有表现出空间聚集性.DBH≤10 cm的华北落叶松个体很少且散生于样地,而DBH≤10 cm的青杄大量聚集于样地中部.DBH≤10 cm的青杄在样地偏西北区域也有大量分布,而DBH≤10 cm的红桦主要分布于样地偏东南区域.灰栒子、土庄绣线菊和四川忍冬等灌木树种也表现出一定的异质性空间分布特征.树种分布格局受生境条件影响,同时与自身发育规律、更新特征及生态习性等相关.     

后河自然保护区珍稀濒危植物群落乔木层结构特征

对1hm^2固定样地内的亚热带常绿落叶阔叶混交林乔木层树种的胸径级结构和高度级结构以及按径经对乔木树种多样性和均匀度进行了研究。结果显示;群落内乔木树种数和个体数堕落有径级和高度级增加呈下降趋势。树种数和个体数之间存在显著正相关关系。胸径面积之和随胸径级增加呈波动状态,而随高度级的增加呈先升后降的变化。群落的多相关性一指数和均匀度指数都较高,群落内优势种明显,各种的多度差异较小,群落结构较为稳定,其中珍稀植物在各个胸径级和高度级内的树种数和个体数都较高,群落的更新良好。幼苗补充充足,珍稀树种幼苗丰富度和多度较高。     

广州公园植物群落物种组成及多样性研究

通过对广州城区10 个公园中92 块样地进行调查, 旨在探讨不同公园中植物群落物种构成及其多样性。调查显示: 样地植物种类较为丰富, 共出现维管植物275 种, 以被子植物为主; 样地中乔木共计143 种; 在乔木层中, 有6个树种出现频度超过50%, 8 种灌木频度超过50%, 12 种草本植物频度超过50%; 而不同公园间草本层植物多样性差异较小, 但是, 越秀公园、雕塑公园和天河公园等面积较大的公园乔木多样性较低; 与乔木层相比, 灌木层植物多样性普遍偏低在乔木层。因此需要进一步加强景观植被中灌木植物的配置, 进而提升城市公园森林美景。     

吉林蛟河不同演替阶段针阔混交林乔木幼苗数量组成及其时间动态

为了解蛟河地区木本植物幼苗的数量特征及其年际动态, 以及影响幼苗数量的生态学过程, 该文以不同演替阶段针阔混交林监测样地为基础, 在样地内共设置了451个种子雨-幼苗观测样站.通过2012-2014年连续3年的幼苗监测调查, 对木本植物幼苗物种组成,数量特征,高度级结构及其年际动态进行了分析, 并用多元回归的方法分析了幼苗数量与林分类型,同种成体胸高断面积之和及林冠开阔度的关系.结果表明: (1)林下幼苗层主要木本植物的组成在不同演替阶段林分中差异不大, 并与样地内主要树种组成保持着一定相似性, 但幼苗重要值排序在年际间和不同演替阶段稍有波动.(2) 3个样地内幼苗个体数量和物种数都主要集中在5-20 cm高度级之间, 之后随高度级增加而逐渐减少, 但幼苗个体数量减少更快.表明与种间竞争相比, 物种内部的相互作用是导致幼苗死亡的主要原因, 证实了负密度制约效应在幼苗更新过程中的作用.(3) 5个主要树种的幼苗数量都与同种成体胸高断面积之和呈显著的正相关关系, 还呈现出明显的生境偏好, 表明扩散限制和生态位过程也会影响幼苗的数量和分布.该文间接证实了负密度制约效应,扩散限制和生态位过程对温带地区不同演替阶段森林群落中幼苗数量组成的影响.     

超高产小麦冠层光辐射特征的研究

在超高产栽培条件下,对多穗型小麦品种豫麦49的冠层光辐射特征进行了研究.结果表明,豫麦49叶面积指数 LAI 全生育期变化为单峰曲线,由越冬期开始逐渐增大,于开花期达最大值,之后下降.开花后D2 基本苗为150×104株/hm2 处理绿叶面积保持时间较长.其叶片分布 LD 处理间存在显著差异,但以D2处理的LD较为合理.各时期处理间平均叶倾角 MFIA 均为高密度的大于低密度的,返青以前不同处理间的差异较小,拔节以后差异增大,灌浆后期各处理MFIA均有减小趋势.消光系数 K 随天顶角增大而增大,D2处理冠层消光系数适中,且分配较优.冠层直射辐射透过系数 TR 随天顶角增大逐渐减小,开花期各处理之间差异显著,灌浆中期各处理之间差异减小.D2处理因其产量三因素协调而产量显著高于其它处理.综合以上结果可知,豫麦49在超高产条件下以D2处理的冠层结构最优,表现为LAI大小适中,叶片分布均匀,冠层消光系数分布合理,光能利用率较高.     

宁夏六盘山半湿润区华北落叶松林冠层叶面积指数的时空变化及坡面尺度效应

受立地环境条件的坡位差异影响,叶面积指数(LAI)在坡面这个基本空间单元内往往具有很大空间(坡位、坡长)和时间(季节)变化,因而存在着坡面空间尺度效应及其季节变化,需对此加以深入研究、准确理解和精细刻画,从而为准确描述森林的结构、生长和生态水文功能提供科学基础。在六盘山香水河小流域选取了一个34年生华北落叶松(Larix gmelinii var.principis-rupprechtii)人工林典型坡面,均匀划分为空间连续的16个样地,于2015年5–10月测定了各样地林冠层LAI,分析其坡位变化及季节差异,并以LAI的顺坡滑动平均值在水平坡长增加100 m时的变化值(LAI/100 m)表示坡面尺度效应。研究表明,林冠层LAI具有明显的坡位变化和尺度效应,且月份变化明显。在5月份,LAI随离坡顶距离增加(坡位下降)而逐渐减小,坡面尺度效应是降低0.02/100 m。在6、7和8月份,LAI均从坡顶向下逐渐增大,在坡中部达最大后又逐渐减小,坡面尺度效应在离开坡顶的0–244.2 m和244.2–425.1 m范围内分别为升高0.15/100 m、0.16/100 m、0.18/100 m及降低0.09/100 m、0.08/100 m、0.07/100 m;在9和10月份,LAI均为随离坡顶距离增加而逐渐增大,坡面尺度效应分别为升高0.03/100 m和0.09/100 m。主要影响因素的季节变化导致了上述冠层LAI的坡位差异和尺度效应的季节变化。在5月份,主导因素是地形遮挡引起的辐射和温度的坡位差异;在6–8月份,主导因素是土壤含水量限制;在9–10月份,地形条件(海拔(坡位)、坡度)、气象条件、土壤含水量及土壤水文性质(孔隙度、持水量)等因子共同影响林冠层LAI坡位变化。对生长季各月,拟合了不同坡位样地林冠层LAI与坡面均值的比值随水平坡长增加的非线性关系,可藉此由任意坡位样地的LAI测定值估算坡面均值,以节省野外测定时间和工作量。     

Phylogenetic Structure of Tree Species across Different Life Stages from Seedlings to Canopy Trees in a Subtropical Evergreen Broad-Leaved Forest

Investigating patterns of phylogenetic structure across different life stages of tree species in forests is crucial to understanding forest community assembly, and investigating forest gap influence on the phylogenetic structure of forest regeneration is necessary for understanding forest community assembly. Here, we examine the phylogenetic structure of tree species across life stages from seedlings to canopy trees, as well as forest gap influence on the phylogenetic structure of forest regeneration in a forest of the subtropical region in China. We investigate changes in phylogenetic relatedness (measured as NRI) of tree species from seedlings, saplings, treelets to canopy trees; we compare the phylogenetic turnover (measured as β_NRI) between canopy trees and seedlings in forest understory with that between canopy trees and seedlings in forest gaps. We found that phylogenetic relatedness generally increases from seedlings through saplings and treelets up to canopy trees, and that phylogenetic relatedness does not differ between seedlings in forest understory and those in forest gaps, but phylogenetic turnover between canopy trees and seedlings in forest understory is lower than that between canopy trees and seedlings in forest gaps. We conclude that tree species tend to be more closely related from seedling to canopy layers, and that forest gaps alter the seedling phylogenetic turnover of the studied forest. It is likely that the increasing trend of phylogenetic clustering as tree stem size increases observed in this subtropical forest is primarily driven by abiotic filtering processes, which select a set of closely related evergreen broad-leaved tree species whose regeneration has adapted to the closed canopy environments of the subtropical forest developed under the regional monsoon climate.     

Composition and Dynamics of Functional Groups of Trees During Tropical Forest Succession in Northeastern Costa Rica

We compared the functional type composition of trees ≥10 cm dbh in eight secondary forest monitoring plots with logged and unlogged mature forest plots in lowland wet forests of Northeastern Costa Rica. Five plant functional types were delimited based on diameter growth rates and canopy height of 293 tree species. Mature forests had significantly higher relative abundance of understory trees and slow-growing canopy/emergent trees, but lower relative abundance of fast-growing canopy/emergent trees than secondary forests. Fast-growing subcanopy and canopy trees reached peak densities early in succession. Density of fast-growing canopy/emergent trees increased during the first 20 yr of succession, whereas basal area continued to increase beyond 40 yr. We also assigned canopy tree species to one of three colonization groups, based on the presence of seedlings, saplings, and trees in four secondary forest plots. Among 93 species evaluated, 68 percent were classified as regenerating pioneers (both trees and regeneration present), whereas only 6 percent were classified as nonregenerating pioneers (trees only) and 26 percent as forest colonizers (regeneration only). Slow-growing trees composed 72 percent of the seedling and sapling regeneration for forest colonizers, whereas fast-growing trees composed 63 percent of the seedlings and saplings of regenerating pioneers. Tree stature and growth rates capture much of the functional variation that appears to drive successional dynamics. Results further suggest strong linkages between functional types defined based on adult height and growth rates of large trees and abundance of seedling and sapling regeneration during secondary succession.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp     

A Neighborhood Analysis of the Consequences of Quercus suber Decline for Regeneration Dynamics in Mediterranean Forests

In forests, the vulnerable seedling stage is largely influenced by the canopy, which modifies the surrounding environment. Consequently, any alteration in the characteristics of the canopy, such as those promoted by forest dieback, might impact regeneration dynamics. Our work analyzes the interaction between canopy neighbors and seedlings in Mediterranean forests affected by the decline of their dominant species (Quercus suber). Our objective was to understand how the impacts of neighbor trees and shrubs on recruitment could affect future dynamics of these declining forests. Seeds of the three dominant tree species (Quercus suber, Olea europaea and Quercus canariensis) were sown in six sites during two consecutive years. Using a spatially-explicit, neighborhood approach we developed models that explained the observed spatial variation in seedling emergence, survival, growth and photochemical efficiency as a function of the size, identity, health, abundance and distribution of adult trees and shrubs in the neighborhood. We found strong neighborhood effects for all the performance estimators, particularly seedling emergence and survival. Tree neighbors positively affected emergence, independently of species identity or health. Alternatively, seedling survival was much lower in neighborhoods dominated by defoliated and dead Q. suber trees than in neighborhoods dominated by healthy trees. For the two oak species, these negative effects were consistent over the three years of the experimental seedlings. These results indicate that ongoing changes in species’ relative abundance and canopy trees’ health might alter the successional trajectories of Mediterranean oak-forests through neighbor-specific impacts on seedlings. The recruitment failure of dominant late-successional oaks in the gaps opened after Q. suber death would indirectly favor the establishment of other coexisting woody species, such as drought-tolerant shrubs. This could lead current forests to shift into open systems with lower tree cover. Adult canopy decline would therefore represent an additional factor threatening the recruitment of Quercus forests worldwide.     

Composition and temporal dynamics of tree seedlings at different successional stages of conifer and broad-leaved mixed forests in Jiaohe,Jilin Province,China

AimsOur objective was to explore the composition and temporal dynamics of woody plant seedlings and the ecological processes that affect the amount of seedlings in Jiaohe, Jilin Province, China. Methods We established a total of 415 seed-seedling census stations in three large permanent field plots belonging to three successional stages in the conifer and broad-leaved mixed forests. Based on three seedling censuses from 2012 to 2014, we analyzed species composition, quantitative character, height-classes structure and their inter-annual dynamics. Multiple linear regression was used to test the relationship between the abundance of seedlings for five major species and the forest types, the sum of the basal area of conspecific adult within 20 m away from a seed trap, as well as canopy openness.Important findings Our results show that: (1) The species composition of seedlings slightly varied among different successional stages, and was similar with that of trees in the plots. The rank of important values for seedling species among different years and successional stages varied slightly. (2) The number of seedlings and seedling species distributed mainly between 5-20 cm height classes, and decreased with the increasing height class. The number of seedlings decreased faster than that of seedling species, indicating that compared with interspecific competition, intraspecific competition was the main driver that led to seedling death. It confirmed the role of the negative density dependence in affecting seedling regeneration. (3) The amount of seedlings for all of the five major species was significantly positively related to the sum of the basal area of conspecific adults, which indicated that the quantity and distribution of seedlings were affected by dispersal limitation as well as niche processes. Our research confirmed the role of negative density dependence, dispersal limitation and niche processes on seedling composition.     

The Effect of Spatial Structure of Pasture Tree Cover on Avian Frugivores in Eastern Amazonia

The movement of frugivores between remnant forests and successional areas is vital for tropical forest tree species to colonize successional habitats. The response of these species to the spatial structure of pasture tree cover is largely unknown. We studied avian frugivores that were found in primary forest edges and large pastures in eastern Amazonia, Brazil. We determined how the small‐scale spatial structure of pasture trees at forest edges affects five response variables: bird presence, visitation rate, duration of visit, species richness, and an index accounting for species’ level of frugivory and abundance in forests. We used hierarchical linear models to estimate the effect of four predictor variables on response variables: (1) clustering of pasture trees; (2) percent canopy cover of pasture trees; (3) distance of pasture tree to forest edge; and (4) tree crown area. The study species, many of which are widely distributed in the Neotropics, were generally insensitive to percent cover and clustering of trees. Frugivore visitation to individual trees remained constant as cover increased. Visitation was positively correlated with focal tree distance to forest edge and crown area. The positive relationship between distance and visitation rates may be due to the increased abundance of some resource further from forests. If pastures were abandoned the distance from forest edges would not likely limit frugivore visitation and seed deposition under large pasture trees in our study (i.e., up to 200 m distant).     

Impact of invasion of Acer platanoides on canopy structure and understory seedling growth in a hardwood forest in North America

Invasion by exotic plant species is known to affect native communities and ecosystems, but the mechanisms of the impacts are much less understood. In a field study, we examined the effects of a tree invader, Acer platanoides (Norway maple, NM), on canopy structure and seedling growth in the understory of a North American deciduous forest. The experimental site contains a monospecific patch of A. platanoides and a mixed patch of A. platanoides with its native congener, A. rubrum (red maple, RM). In the study, we examined canopy characteristics of three types of trees in the forests, i.e., RM trees in the mixed forest, NM trees in the mixed forest, and NM trees in its monospecific patch. Height growth and biomass production of RM and NM seedlings under intact canopies and newly created gaps of the three types of trees were followed for two growing seasons. We found that removal of half of the canopy from focal trees increased canopy openness and light transmission to the forest floor, but to a greater extent under NM trees than under RM trees. Seedlings of these two Acer species varied greatly in biomass production under canopies of the same type of trees and in their responses to canopy opening. For example, seedlings of the exotic NM grown under the native RM trees in the mixed forests increased biomass production by 102.4% compared to NM seedlings grown under conspecific trees. The native RM seedlings grown under NM trees, however, reduced biomass production by 23.5% compared to those grown under conspecific trees. It was also observed that RM was much more responsive in biomass production to canopy opening than NM. For instance, total seedling biomass increased by 632.2% in RM, but by only 134.6% in NM in response to the newly created gaps. In addition, we found that NM seedlings allocated a greater portion of biomass below-ground as canopy openness increased, whereas the same trend was not observed in RM seedlings. Our results thus demonstrated that invasion of NM significantly altered canopy structure and community dynamics in the hardwood forest. Because the exotic NM seedlings are able to grow well under the native RM trees, but not vice versa, NM will likely expand its distribution in the forests and make it an ever increasingly serious tree invader in its non-native habitats, including North America.