Status of urban vegetation in Guangzhou City

According to a survey for the urban vegetation of Guangzhou, urban vegetation has a significantly difference from natural vegetation because of intense human impacts. The research was conducted in a synthetic survey for soil, species diversity, roadside trees and ecological function of urban vegetation in Guangzhou City. The results showed that: (1) soil densities of urban roadside and park forests were higher than mean density of natural forest soil. The pH values of soil in urban roadside were higher too, and the content of organic matter and the concentration of nitrogen were lower. (2) Species diversity of urban vegetation was lower. The most number of species was only 16 species in tree layers of urban forest. (3) Tree growth was limited by narrow space in high-density urban area, where the trees with defects and disorders were common. (4) Comparing with mature natural forests, the productivity of urban vegetation was lower. The effect of urban vegetation on balance of carbon and oxygen were influenced by the low primary production of urban vegetation. Therefore, the growth condition for urban vegetation should be improved. Biodiversity, primary production and ecological function should be increased for urban vecletation in order to improve urban eco-environment.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Conservation of forest biodiversity and ecosystem properties in a pastoral landscape of the Ecuadorian Andes

High Andean cloud forests are home to a diversity of unique wildlife and are important providers of ecosystem services to people in the Andean regions. The extent of these cloud forests has been widely reduced through conversion to pasture for livestock, which threatens the forests’ ability to support biodiversity and provide ecosystem services. This paper explores whether impacts on woody plant biodiversity and four ecosystem properties (woody plant species richness, juvenile timber tree abundance, soil organic matter content and soil moisture) from converting forest to pasture can be mitigated if some woody forest vegetation is maintained within pastures. Woody vegetation in pastures was found to conserve those woody plant species that are more tolerant to exposure and grazing, but conservation of the high montane cloud forest community required areas of forest from which livestock were restricted. The sampled sites clustered according to woody plant species cover; these clusters represented a gradient from pasture with patches of shrubs to mature forest. Clusters differed in both woody plant species richness and number of juvenile timber trees whereas soil organic matter and soil moisture were observed to be similar among all clusters. This suggests that the different habitats may have some equivalent ecosystem properties. We conclude that the presence of woody vegetation in pastures may reduce some of the impacts of converting forest to pasture, but should not be considered a substitute for protecting large areas of forest, which are essential for maintaining woody plant species diversity in high Andean cloud forest.     

Structural and compositional controls on transpiration in 40- and 450-year-old riparian forests in western Oregon, USA

Large areas of forests in the Pacific Northwest are being transformed to younger forests, yet little is known about the impact this may have on hydrological cycles. Previous work suggests that old trees use less water per unit leaf area or sapwood area than young mature trees of the same species in similar environments. Do old forests, therefore, use less water than young mature forests in similar environments, or are there other structural or compositional components in the forests that compensate for tree-level differences? We investigated the impacts of tree age, species composition and sapwood basal area on stand-level transpiration in adjacent watersheds at the H.J. Andrews Forest in the western Cascades of Oregon, one containing a young, mature (about 40 years since disturbance) conifer forest and the other an old growth (about 450 years since disturbance) forest. Sap flow measurements were used to evaluate the degree to which differences in age and species composition affect water use. Stand sapwood basal area was evaluated based on a vegetation survey for species, basal area and sapwood basal area in the riparian area of two watersheds. A simple scaling exercise derived from estimated differences in water use as a result of differences in age, species composition and stand sapwood area was used to estimate transpiration from late June through October within the entire riparian area of these watersheds. Transpiration was higher in the young stand because of greater sap flux density (sap flow per unit sapwood area) by age class and species, and greater total stand sapwood area. During the measurement period, mean daily sap flux density was 2.30 times higher in young compared with old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. Sap flux density was 1.41 times higher in young red alder (Alnus rubra Bong.) compared with young P. menziesii trees, and was 1.45 times higher in old P. menziesii compared with old western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees. Overall, sapwood basal area was 21% higher in the young stand than in the old stand. In the old forest, T. heterophylla is an important co-dominant, accounting for 58% of total sapwood basal area, whereas P. menziesii is the only dominant conifer in the young stand. Angiosperms accounted for 36% of total sapwood basal area in the young stand, but only 7% in the old stand. For all factors combined, we estimated 3.27 times more water use by vegetation in the riparian area of the young stand over the measurement period. Tree age had the greatest effect on stand differences in water use, followed by differences in sapwood basal area, and finally species composition. The large differences in transpiration provide further evidence that forest management alters site water balance via elevated transpiration in vigorous young stands.     

Landscape effects in bird assemblages differ between plantations and broadleaved forests in a rural landscape in central Japan

It is important to conserve forest-dependent organisms not only in broadleaved forests but also in plantation forests. We examined how surrounding forest areas affect forest bird assemblages inhabiting conifer plantations and broadleaved forests in a rural landscape in central Japan. Surrounding forest areas were measured separately as plantation area and broadleaved forest area within 200 m of each sampling site. We used hierarchical partitioning to analyze the effects of surrounding forest areas and stand structures (stand height and understory coverage) on the occurrence of four species groups. We especially focused on mature forest users that are most sensitive to loss of broadleaved forests. Occurrence of mature forest users inhabiting plantation sites was positively affected both by plantation area and broadleaved forest area whereas the occurrence of mature forest users inhabiting broadleaved forests was affected by stand height only. These results suggest that surrounding forest areas were more important to mature forest users in plantations than in broadleaved forests. To conserve mature forest users, increasing surrounding forest areas are important in plantations whereas increasing stand heights would be effective in broadleaved forests.     

Nitrogen dynamics during ecosystem development in tropical forest restoration

We considered whether ecological restoration using high diversity of native tree species serves to restore nitrogen dynamics in the Brazilian Atlantic Forest. We measured δ¹⁵N and N content in green foliage and soil; vegetation N:P ratio; and soil N mineralization in a preserved natural forest and restored forests of ages 21 and 52 years. Green foliage δ¹⁵N values, N content, N:P ratio, inorganic N and net mineralization and nitrification rates were all higher, the older the forest. Our findings indicate that the recuperation of N cycling has not been achieved yet in the restored forests even after 52 years, but show that they are following a trajectory of development that is characterized by their N cycling intensity becoming similar to a natural mature forest of the same original forest formation. This study demonstrated that some young restored forests are more limited by N compared to mature natural forests. We document that the recuperation of N cycling in tropical forests can be achieved through ecological restoration actions.     

Understory diversity and composition after planting of teak and mahogany in Yogyakarta,Indonesia

ABSTRACT

Forest rehabilitation is when a desired tree species is planted in degraded forests or lands. Rehabilitation by planting a single tree species is a common way to restore exploited forests to maintain ecological processes. We compared woody and herbaceous understory vegetation between forests rehabilitated by mahogany (N = 12) or teak (N = 12) planted from 1941 until 2003 in Yogyakarta, Indonesia. Understory vegetation of these areas was compared with that of three native forests. Species richness, species diversity, density of plants and proportion of native plants did not differ between the rehabilitated areas and the native forest. Recently rehabilitated areas were different from the native forests while 41–74 yr after rehabilitation, characteristics of understory vegetation approached those of native forest. We described species composition using ordination, and found it to differ between areas rehabilitated with teak and with mahogany and, particularly, between the rehabilitated areas and the native forests. Time since rehabilitation and tree species planted were important for the species composition of understory vegetation. We conclude that the selection of species for rehabilitation and letting rehabilitated areas mature are important for understory development and species diversity.     

The ecology of tree regeneration in mature and old forests: combined knowledge for sustainable forest management

We focused our attention on quantifying the factor complex of forest regeneration in 423 mature and old stands with contrasting environmental conditions. We recorded the microhabitat selection of tree recruits, the frequency of tree seedlings, and evaluated the drivers of sapling abundance and diversity. The majority of forest regeneration was established on undisturbed forest floor. Dead wood was a frequent substrate in spruce-(co)dominated forests. Seedling frequency within a stand was related to the site-type specific productivity gradient of stands—pine seedlings were common in low-productivity and spruce in high-productivity boreal forests. Seedlings of temperate broad-leaved trees dominated in productive boreonemoral forests, except for oak, which showed a uniform distribution of abundance in all forest site-types. Sapling abundance was dictated by forest site-type, and facilitated by stand diversity, variability in stand closure, lying dead wood, abundant moss, and a thick organic layer. Only in boreal forests was sapling abundance suppressed by the abundant spruce and younger trees. Upon considering the relationship between sapling abundance and species richness, sapling diversity was dependent on forest site-type, suppressed by stand density and dead wood (old gap) abundance, and facilitated by stand diversity. In addition, boreonemoral stands, competition from herbs, and facilitation by mosses occurred. The observed pattern of tree recruitment points to the importance of top-down effects of the overstory, competing or facilitating interactions with forest floor vegetation, and availability of regeneration microhabitats, which in complex make their ecology comparable with forest herbs. Natural forest regeneration can be enhanced if silvicultural methods support mixed stands and enhance field layer diversity. Oak can provide the universal tree species to improve stand structure over a wide range of habitats.     

珠江源自然保护区的森林生态功能

珠江源自然保护区地处滇东高原，总面积230459.0hm^2，森林覆盖率57．5％。其特点是树种组成单一，中幼林多；农林交错、次生林占优势、林分质量差；森林生态脆弱。对本自然保护区的森林生态功能评价：①总体生态功能“差”；②森林生态脆弱；③蓄水、保土、保肥、增产等效益显著；④具有生物多样性特点。对今后森林资源的保护、发展提出了建议。     

热带次生林经营研究文献分析

热带次生林面积巨大且在热带森林资源中的作用越来越重要,因而拥有巨大的经营潜力和生态功能。次生林演替过程中的主要研究成果如下：土壤贮存的种子对次生林的再生非常重要,光投射的强度增加和温度提高将刺激种子萌芽,而残余植被群落强烈影响次生林种子的散布,食种子动物影响次生林的成林;次生林群落植物种类数量一般随演替的进程而增加;随着演替的进程,次生林内阳生树种趋于衰亡,耐荫树种不断增加;次生林的树种数量能接近原生林水平的时间过程更随着林分种类、过去土地的利用强度和利用种类,以及环境条件的不同而异;在一定环境中,人工林树种通过人工林树种改变光、温度和土壤表层的湿度,能够促进发芽和种子生长,改善林地和林下植被的状况,从而加速次生林演替。大多数食草动物喜欢在次生林中取食,因为次生林中先锋树种很少或没有机械和化学保护,且林内许多树种产生大量可食用的果实;环境和火对次生林演替有一定影响;在早期的演替过程中,更多的生物量分配到资源需求旺盛的组织（如叶和细根）,在演替晚期阶段,更多的生物量则分配到结构组织中（如木质部和根端）。次生林在15至20年内能迅速积累生物量,然后积累逐渐减慢;次生林被砍伐或火烧后,森林土壤的结构被破坏,导致土壤有机质和氮减少。     

油松—白桦混交林种间关系研究

在调查河北隆化县油松－白烨混交林的林木生物量（地上部生物量及根系生物量）、林下草灌木、林地枯落物的总量以及不同混交距离油松地上地下部分生长发育状态的基础上，研究了混交林的种间关系。结果表明，该混交林作为华北地区广泛分布的一种林型，林下草灌木繁茂，林地枯落物分解迅速，有利于土壤理化性质和林分营养状况的改善，种间关系处于基本协调状态。由于林龄及密度原因，混交林生物量略低于油松纯林，在混交林中白桦对油松的生长有一定的抑制作用，抑制作用因混交距离而变化。本文提出了合适的混交距离和混交方式。     

苍梧县低效防护林综合改造技术研究

苍梧县是珠江防护林体系建设的重点县。由于人为干扰、树种选择不当、经营措施不合理等原因,林分退化严重,生态环境遭到破坏,形成较大面积的低效马尾松纯林、湿地松纯林和低效次生阔叶林。本研究通过对低效林分的土壤理化性质、凋落物、植物多样性、生物量等的调查,提出了对苍梧县低效林采取异龄混交、调整群落结构、调控林分密度、抚阔补珍、抚针植阔和封育补植等一系列综合改造技术,并对几种低效林分改造后形成的不同林分结构的土壤物理、化学性质及持续特性等效果进行了初步评价。     

Structural and environmental characterization of old-growth temperate rainforests of northern Chiloé Island,Chile: Regional and global relevance

Old-growth forests are ecologically relevant reservoirs of biodiversity and provide valuable and unique ecosystem functions in the landscape. However, what constitutes an old-growth stand is confusing because the definition depends largely on the forest type under study. Despite the ecological importance of old-growth temperate rainforests in southern Chile in comparison to other global forests, no attempts have been made to characterize them as a way to assess their structural variability. Here, we characterized old-growth stands of Valdivian and North Patagonian rain forest types located in Chiloé Island (Chile, 42°30′S) using inventory data from 23 permanent plots (0.1 ha each) located in rural landscapes and protected areas of northern Chiloé Island. For each stand, its age (average age of the oldest trees present in each stand) and disturbance regimes (evidence of recent human impact, e.g. cuttings or fires, and tree growth rates) were used as defining old-growth criteria. We characterized the structure (tree species richness, size-density distributions, vertical stratification and presence of snags) and floristic composition of each stand. Environmental variables (i.e. temperature, distance to coastline and elevation) were related to stand structure using multivariate constrained correspondence analysis. Old-growth forests were commonly characterized by (a) tree basal areas >80 m²/ha; (b) density of shade-tolerant tree species in the emergent and dominant canopy layer >36%; (c) higher tree species richness (>7 tree species) than successional stands; (d) presence of large canopy emergents (>80 cm dbh, >25 m tall); (e) high vertical heterogeneity; and (f) minimum stand ages older than 200 years. Old-growth forests showed a distinctive structural variability and floristic diversity influenced both by stand age and disturbance history of the stands. Structural variability was also related to environmental differences among sites (e.g. air temperature, distance to coastline, soil types). Old-growth forest features described here can offer a baseline for managers interested in maintaining and restoring old-growth forest structure in southern temperate rain forests.     

Tree effects on the chemical topsoil features of oak, beech and pine forests

We aimed to study tree effects on the chemical properties of forest soils. We compared soil features of three types of forest ecosystems, each with four stands (replicates): beech forests (Fagus sylvatica), oak forests (dominated by Quercus pyrenaica) and pine plantations (Pinus sylvestris). Five samples from the top 10 cm of soil were taken per stand, from which pH, organic matter content (O.M.), total nitrogen (N) and available calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺) and sodium (Na⁺) were determined. Litter layer depth was measured at each soil sampling point. We also measured tree density and crown diameters at each stand. Our results indicated that soil samples from the four pine plantation stands were more similar while oak and beech stands were characterised by great variability in terms of soil properties and leaf litter depth. Although the identity of the dominant tree species significantly influenced several topsoil chemical properties (increase in pH and available cations in oak forests and higher organic matter and total nitrogen in beech and pine ecosystems), there were other important factors affecting soil features that may be taken under consideration. Differences between soil properties of the three types of forest ecosystems were mainly related to the characteristics of the litter layer and less related to the tree layer structure. Finally, the establishment of pine plantations in naturally deciduous tree areas made the topsoil features more homogeneous.     

广东潮州凤凰山次生林物种多样性及群落优势种的研究

应用样方调查法,研究分析了广东潮安凤凰山省级自然保护区内2片保护状态较好的次生林群落的植物组成和物种多样性特点.在两个面积为1200 m2的调查样方内,共记录了112种维管植物,隶属于48科77属.次生林优势科为茜草科、山茶科和樟科.乔木层优势种为阿丁枫(Altingia chinensis)、尖叶假蚊母树(Disty...     

近自然森林经营理论在龙里林场国家储备林改培中的应用

指出了龙里林场现有国家储备林中以马尾松人工林为主,树种结构单纯、层次结构简单、生态效益差、生态系统脆弱,容易发生雪压、风倒、火灾,松毛虫危害严重。为了改善林场马尾松人工林的健康状况,提高物种多样性和生态稳定性,优化林分的树种、水平、垂直结构,进一步提高林分质量,模仿马尾松自然演替规律,通过择伐,在林下补植了乡土珍贵树种,以把马尾松人工林尽可能地改造为接近自然状态的异龄针阔混交林,结果表明:近自然改造具有如下优点:①确保了持续的主林层郁闭,实现了森林的永续利用。②将培育珍贵树种与马尾松大径材有机结合起来,兼顾了森林的经济、生态、社会效益。③有利于提高林分质量,保证了森林的健康可持续发展。     

NITROGEN NUTRIENT MECHANISM IN SECONDARY SUCCESSION PROCESS OF THE MIXED BROAD-LEAVED/ KOREAN PINE (PINUS KORAIENSIS) FOREST

INTRODUCTlONThemixcdbroad-leaved/Pinuskor`IiensiSforestwhichisoneofthemainforestsofNortheastChina,isintlleCllangbaiMountail1s(JilinProvince)a11dtheXiaoxing'anMotu1-tains(inHeilonroIangProvince).Thisistl1empicalmixcddeciduous/co11iferforestvegcta-tionofthcarca.But,duetocuttingandanunbalancebctWeenharvesti11gandanntlalin-crement,themixedbroad-leaved/PinuSko-raiensIjforestsha1,ebeenreplacedwithsec-ondaryforests(includingthelargearPaofsecondaryforestleftfrol11thepast)sinceltsclearcutti…     

Composition,structure, and management potential of secondary dry tropical vegetation in two abandoned henequen plantations of Yucatan,Mexico

Data on the composition and stand dynamics of abandoned henequen (Agave fourcroydes) fields of different ages are presented and their management potential discussed. The study was carried out in the Hacienda of Kancabchen, Yucatan, Mexico in 12- and 26-year-old secondary forests. Species richness and diversity were greater as the stand grew older. Even though 73% of species have the capacity to regenerate from coppiced shoots, only between 30 and 50% of the individuals actually regenerate from coppiced shoots in both communities, respectively. According to the Sørensen similarity index both stands are similar in composition (73%), while the Motyka index indicates that they differ in biomass distribution (17%). This could be due to soil conditions and the management of these areas, or a combination of both. The 26-year-old abandoned henequen stand still has pioneer species dominating and has very few late successional species present. Slow-growing tree species on the 26-year-old stand were expected, but their absence could be due to the lack of seed sources, a limited dispersal capability, or to an arrested succession due to human perturbation and management. Eight species dominated the stands, accounting for more than 60% of the total importance values. Most species present in both stands are widely used locally and are commercialized inside the rural communities. Potential management strategies could involve forest thinning to remove competition and favor those species used by the communities, those with potential to increase soil fertility, and those that could have semi-commercial purposes. Management could also include enrichment with other species such as Cedrela odorata and Apoplanesia paniculata that are widely used and were previously present as part of the native vegetation of the area.     

大老岭林场次生林更新方式对林分组成和林地肥力的影响分析

利用湖北宜昌大老岭林场次生林采伐迹地3种不同更新方式林分的调查数据,对不同 的更新方式的林分组从树种组成、林下植被和林木生长三个方面分析了林分组成;从林地水分 物理性质和林地化学性质分析了林地肥力状况,得出如下结论:1.不同更新方式的林分组成和 林地肥力有明显不同;2.次生林采伐迹地更新所形成的人工林表现出不稳定性。     

滇东南岩溶山区树种配置的初步研究

3年来在滇东南岩溶山区开展的树种配置试验的初步研究结果表明 :影响岩溶山地林木生长的主要因素是坡度、岩石裸露率、土类、土层厚度和土壤中的石砾含量 ,而坡向、坡位、土壤的吸湿水、旱季土壤含水率、pH值及土壤养分对林木生长的影响不明显。在岩溶地区的造林应采取特殊的措施 ,尽量保护原有植被 ,对于形成复层的林分结构具有非常重要的作用 ,特别是在多石的薄层石灰土类型上 ,人工种植的阔叶树生长较差 ,通过种植针叶树 ,能形成乔灌草结构的复层林分 ,对改善岩溶山区的生态环境效果十分明显。在吸湿水、全氮、水解氮、速效磷、速效钾、pH值、有机质和旱季土壤含水率等 8个土壤性状中 ,吸湿水、速效磷、速效钾 3个性状在年度间的差异非常显著 ,其中吸湿水平均增加 3 6 6 % ,每kg干土中的速效磷和速效钾平均分别增加9 99mg和 4 2 5 9mg ,显示出林木对土壤的改良作用。在多石的石灰土类型上 ,适宜营造墨西哥柏、郭芬柏和冲天柏等针叶树 ,在其中土层较厚的地方可种植银荆 ;在厚层山地红壤类型上 ,适宜营造墨西哥柏、冲天柏、郭芬柏、川滇桤木、滇合欢、银荆、杜仲、酸枣、苦刺等针阔、阔阔混交林以提高其生态和经济效益