小兴安岭南坡红松林动态模拟

用林窗模型研究了小兴安岭南坡红松针阔混交林长期动态变化过程。通过有效性检验证明所得模型能够合理地预测森林的组成、结构和动态。以经营数据估计模型的参数后,运行模型模拟１２个树种６００ａ的演替动态,结果表明次生裸地的森林在几个世纪后能恢复到以红松为主的针叶树占优势的群落,演替呈现为树种组成差别很大的３个阶段：第１个阶段为０到７０ａ,这时阳性先锋树种在群落中占据优势,无论树种组成,生物量,生产力,阳性树种占的比例都最大;第２个阶段为７０～３００ａ,在这个阶段中,硬阔叶树占优势,呈现了树种多样性最大的一个阶段,阳性阔叶树种还未退去,耐阴针叶树种已开始增多;第３个阶段为３００ａ之后,针叶耐阴树种开始在群落中占据优势,并且整个群落的树种组成、生物量和生产力变化很小,林分的各种特性呈现具有一定波动的相对稳定态。     

Changes in forest biomass and linkage to climate and forest disturbances over Northeastern China

The forests of northeastern China store nearly half of the country's total biomass carbon stocks. In this study, we investigated the changes in forest biomass by using satellite observations and found that a significant increase in forest biomass took place between 2001 and 2010. To determine the possible reasons for this change, several statistical methods were used to analyze the correlations between forest biomass dynamics and forest disturbances (i.e. fires, insect damage, logging, and afforestation and reforestation), climatic factors, and forest development. Results showed that forest development was the most important contributor to the increasing trend of forest biomass from 2001 to 2010, and climate controls were the secondary important factor. Among the four types of forest disturbance considered in this study, forest recovery from fires, and afforestation and reforestation during the past few decades played an important role in short‐term biomass dynamics. This study provided observational evidence and valuable information for the relationships between forest biomass and climate as well as forest disturbances.     

海南霸王岭热带山地雨林森林循环与树种多样性动态

通过对海南岛霸王岭热带山地雨林的调查 ,研究了热带山地雨林树种多样性特征随森林循环的动态变化规律。结果表明 :( 1 )热带山地雨林森林循环不同阶段斑块在森林景观中所占的面积比例分别是 :林隙阶段 ( G)占 38.5 0 % ,建立阶段 ( B)占 2 8.5 0 % ,成熟阶段 ( M)占 2 7.0 0 % ,衰退阶段 ( D)占 6 .0 0 %。 ( 2 )热带山地雨林中乔木树种的密度随森林循环的变化趋势是由 G→B→M呈现出逐渐增加的趋势 ,以成熟阶段达到最大 ,而到衰退阶段又趋于下降。灌木树种则表现出 G阶段斑块的密度最大 ,B阶段的最小 ,从 B到 M有所增加 ,到 D又稍有下降。 ( 3)热带山地雨林中不同高度级和不同径级的树木的密度在森林循环的不同阶段表现出不同的增减趋势 ,其随森林循环过程呈现出的动态变化可能与不同阶段斑块内的空间、环境及物种生物学特性有关。 ( 4 )热带山地雨林中树木的平均胸径、平均高、平均胸高断面积、平均单株材积随森林循环过程呈现出不断增加的趋势 ,其中平均胸径和平均高随森林循环的变化较为平缓 ,而平均胸高断面积和平均单株材积之变化较为陡急。 ( 5 )热带山地雨林森林循环不同阶段的物种多样性指数不同 ,其中 G和 B阶段的物种丰富度和多样性指数值较接近 ,M阶段的物种丰富度达到最大 ,D阶段则最小。     

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.     

Spatial hints of forest ecotone indicating forest succession, a case of larch forests in Baihuashan Reserve, north China

In cold or alpine areas of northern China, birch forests and larch forests are the two primary forest types. These forests are also characteristic of a south branch of boreal forests in Asia. Some ecologists argue that larch forests can replace birch forests, but this still remains a question due to fragmentary or short observations. The ecotone between a larch forest patch and a birch forest patch is the arena in which the two species interplay and compete with each other, and studies of these areas are meaningful to understanding forest succession. In the alpine area of the Baihuashan Reserve, northern China, we sampled a larch-birch forest ecotone with eight plots in four transects and then analyzed population structures of larches and birches. The results show that the edges of the larch forest patch are composed of many larch saplings or young trees, but the edges of the birch forest patch are mainly composed of old birches. Across the ecotone, the larches, on average, are taller than the birches. These facts suggest that larch saplings can permeate into birch forest patches, probably by seed dispersal, germination, success-ful competition and growth, but birch saplings cannot permeate into larch forest patches. Therefore, on the ecotone, larch forest patches can steadily expand by unceasing permeation into birch forest patches, whereas birch forest patches progressively recede due to ultimate death of the old and poor recruitment of the young. Larch forest patches replace birch forest patches in a stepwise manner, causing succession from birch forests to larch forests. This study not only confirms that larch forests can naturally replace birch forests, but also introduces a simple and reliable method, employing spatial hints, to study forest succession. Additionally, the findings are of benefit to cultivation or development of larch forests in cold or alpine areas of the North Temperate Zone, which can be a huge carbon sink.     

Forest turnover rates follow global and regional patterns of productivity

Using a global database, we found that forest turnover rates (the average of tree mortality and recruitment rates) parallel broad-scale patterns of net primary productivity. First, forest turnover was higher in tropical than in temperate forests. Second, as recently demonstrated by others, Amazonian forest turnover was higher on fertile than infertile soils. Third, within temperate latitudes, turnover was highest in angiosperm forests, intermediate in mixed forests, and lowest in gymnosperm forests. Finally, within a single forest physiognomic type, turnover declined sharply with elevation (hence with temperature). These patterns of turnover in populations of trees are broadly similar to the patterns of turnover in populations of plant organs (leaves and roots) found in other studies. Our findings suggest a link between forest mass balance and the population dynamics of trees, and have implications for understanding and predicting the effects of environmental changes on forest structure and terrestrial carbon dynamics.     

西双版纳热带季节雨林的树种组成和群落结构动态

研究了西双版纳热带季节雨林1 hm2(hectare)动态监测样地1993年与2007年之间树种组成和群落结构的变化。对样地中胸径≥5 cm的乔木进行了每木调查。目前其树种组成的热带分布科、属所占比例分别为91%和94%,具有较高比例的热带植物区系性质。在1993年与2007年两次调查之间,树种数量由145种增至179种,仅有1到2个个体的稀有树种所占比例从54%降为51.1%。从森林的垂直结构来看,A、B、C三层的个体死亡率分别为12.8%、12.9%和19.0%,各层树木的增长率分别为-8.5%、-1.4%和44.8%。与此相对应,C层小径级的树木所占比例有较大提高。虽然小径级的树木在种类和数量上比例增大,但个体数量和种类组成相对稳定的A、B层优势树种变化不大,维持了群落结构的稳定性。14 a间,群落中新增加的具有先锋性质的树种不超过5个。1993年时,A、B两层尚有先锋树种存在,2007年已经从A、B两层中退出。因此,从14 a间树种组成和群落结构的变化来看,虽然具有树木的死亡和增补,但其物种成分和群落结构的总体格局没有明显的变化,处于动态平衡过程中。     

Intra‐specific relatedness,spatial clustering and reduced demographic performance in tropical rainforest trees

Intra‐specific negative density dependence promotes species coexistence by regulating population sizes. Patterns consistent with such density dependence are frequently reported in diverse tropical tree communities. Empirical evidence demonstrating whether intra‐specific variation is related to these patterns, however, is lacking. The present study addresses this important knowledge gap by genotyping all individuals of a tropical tree in a long‐term forest dynamics plot in tropical China. We show that related individuals are often spatially clustered, but having closely related neighbours reduces the growth performance of focal trees. We infer from the evidence that dispersal limitation and negative density dependence are operating simultaneously to impact the spatial distributions of genotypes in a natural population. Furthermore, dispersal limitation decreases local intra‐specific genetic diversity and increases negative density dependence thereby promoting niche differences and species coexistence as predicted by theory.     

西双版纳热带森林动态监测样地——树种组成与空间分布格局

 西双版纳热带雨林是中国生物多样性最丰富的生态系统之一,西双版纳也被公认为国际上重要的生物多样性保护的热点地区之一。2007年,在中国科学院生物多样性委员会、加拿大Alberta大学和中国台湾东海大学等相关单位的支持下,由中国科学院西双版纳热带植物园和西双版纳州自然保护区管理局在西双版纳州勐腊县补蚌村的望天树(Shorea wantianshuea)林中建立了一块面积为 20 hm²的热带森林动态监测样地,该样地是中国森林生物多样性动态监测网络建设的重要组成部分之一,其建设技术是按照美国史密森热带研究所的热带森林研究中心(Center for Tropical Forest Science, CTFS) 1980年在巴拿马Barro Colorado Island建立50 hm²样地的技术规范进行的。我们逐一测量并记录了样地中所有树干胸径大于1 cm树木的胸围,并对其挂牌标记、鉴定种名和确定坐标位置。并应用Ripley’s L-Function分析了样地内4种上层优势种和12个稀有种的空间分布格局。研究结果表明：样地内共含有胸径 ≥ 1 cm的乔木95 834株,其中已经鉴定的有95 498株,占总个体数的99.65％;有乔木种类468种 ,隶属于213个属和70个科;另外有336个个体没有鉴定出来,仅占总个体数的0.35％。上层乔木中的望天树重要值排名第2,但具有最大的胸高断面积;中、下层的假海桐(Pittospo ropsiskerrii)个体数最多,占样地内已鉴定乔木个体总数的21.90％。样地内4个上层优势种的小径阶个体数量较多, 而大径阶个体数量较少,径阶分布呈倒“J”型,因此这4个种群可以维持自我更新。在分布格局上,样地内的4个上层优势树种的幼树和中龄树以聚集分布为主,而成年树则以随机分布为主。另外,大多数稀有物种也表现出聚集分布的格局。     

Spatial distribution of young forests and carbon fluxes within recent disturbances in Russia

Forest stand age plays a major role in regulating carbon fluxes in boreal and temperate ecosystems. Young boreal forests represent a relatively small but persistent source of carbon to the atmosphere over 30 years after disturbance, while temperate forests switch from a substantial source over the first 10 years to a notable sink until they reach maturity. Russian forests are the largest contiguous forest belt in the world that accounts for 17% of the global forest cover; however, despite its critical role in controlling global carbon cycle, little is known about spatial patterns of young forest distribution across Russia as a whole, particularly before the year 2000. Here, we present a map of young (0–27 years of age) forests, where 12‐ to 27‐year‐old forests were modeled from the single‐date 500 m satellite record and augmented with the 0‐ to 11‐year‐old forest map aggregated from the 30 m resolution contemporary record between 2001 and 2012. The map captures the distribution of forests with the overall accuracy exceeding 85% within three largest bioclimatic vegetation zones (northern, middle, and southern taiga), although mapping accuracy for disturbed classes was generally low (the highest of 31% for user's and producer's accuracy for the 12–27 age class and the maximum of 74% for user's and 32% for producer's accuracy for the 0–11 age class). The results show that 75.5 ± 17.6 Mha (roughly 9%) of Russian forests were younger than 30 years of age at the end of 2012. The majority of these 47 ± 4.7 Mha (62%) were distributed across the middle taiga bioclimatic zone. Based on the published estimates of net ecosystem production (NEP) and the produced map of young forests, this study estimates that young Russian forests represent a total sink of carbon at the rate of 1.26 Tg C yr^?1.     

Species Dynamics During Early Secondary Forest Succession: Recruitment, Mortality and Species Turnover

The "Initial Floristic Composition" hypothesis is applied to secondary tropical rain forest succession in abandoned agricultural fields with light previous land-use and close to seed sources. This hypothesis predicts that both pioneer and shade-tolerant species colonize a site directly after abandonment, and as the canopy closes, the recruitment of pioneers sharply declines, while recruitment of shade-tolerant species continues. It also predicts higher mortality among pioneers. Consequently, recruited and dead trees are expected to differ in species composition, with highest species richness for the recruits. During 18 mo, we monitored recruitment and mortality of trees with height ≥ 1.5 m in eight plots in abandoned cornfields with initial fallow age of 1–5 yr, in SE Mexico. Shade-tolerant species established in the first years of succession, albeit in low numbers. As predicted, recruited and dead trees differed in species richness and composition, and in shade-tolerant frequency. In contrast to our expectations, over 50 percent of recruits were from pioneer species, as high stand-level mortality opened new opportunities for continued pioneer colonization. Species turnover starts very early in succession but is not always a gradual and continuous process, complicating prevailing succession models. The strong spatial and temporal variability of succession emphasizes the need to monitor these dynamics in permanent plots across a range of initial stand ages, with multiple plots in a given age class.     

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.     

用动态模型研究森林群落中物种间的竞争

研究了以过程为基础的模型在物种竞争试验模型及实践中的应用。应用森林动态林窗模型模拟了群落内物种竞争规律。结果表明：同一群落中具有不同生物、生态学特征的物种竞争过程与环境条件有密切关系。由此确定,竞争是与外部条件密切相关的,不是一个单独稀量物种特征的指标;具有相似生物和生态学特性的物种,在森林植被发育过程中,存在绝对竞争,具有较弱更新与生长能力的物种,始终处于竞争劣热,不宜于在这样的群落中生长,而且有较强更新和生长的树种在群落中处于优势地位。     

Impacts of selective logging on population structure and dynamics of a canopy tree (Olea capensis) in Kakamega forest

This study assessed the impacts of logging on the population structure and dynamics of Elgon teak (Olea capensis), a canopy dominant in Kakamega forest. The objective was to ascertain and determine the regeneration status of this tree species in view of its commercial value. A comparison was made between logged and unlogged sections at three sites in the forest. Pairwise comparisons of the differences in the population structure among three sites and the differences in the mean tree size revealed significant differences in all three study sites. Results also revealed a variation in stem density that was dependent on the block of forest under study. Results of the spatial contagion revealed that O. capensis had a varied clumped distribution in all the study sites. Clumping was highest in the Kisere forest. These results point to logging as the major factor that explains the differences in population structure and stem density in different parts of Kakamega forest. And while intermittent recruitment may explain clumped distribution, logging appears to explain the variation in the degree of clumping.