Species and structural diversity affect growth of oak,but not pine,in uneven-aged mature forests

The effects of mixing tree species on tree growth and stand production have been abundantly studied, mostly looking at tree species diversity effects while controlling for stand density and structure. Regarding the shift towards managing forests as complex adaptive systems, we also need insight into the effects of structural diversity. Strict forest reserves, left for spontaneous development, offer unique opportunities for studying the effects of diversity in tree species and stand structure. We used data from repeated inventories in ten forest reserves in the Netherlands and northern Belgium to study the growth of pine and oak. We investigated whether the diversity of a tree's local neighbourhood (i.e., species and structural diversity) is important in explaining its basal area growth. For the subcanopy oak trees, we found a negative effect of the tree species richness of the local neighbours, which – in the studied forests – was closely related to the share of shade-casting tree species in the neighbourhood. The growth of the taller oak trees was positively affected by the height diversity of the neighbour trees. Pine tree growth showed no relation with neighbourhood diversity. Tree growth decreased with neighbourhood density for both species (although no significant relationship was found for the small pines). We found no overall diversity-growth relationship in the studied uneven-aged mature forests; the relationship depended on tree species identity and the aspect of diversity considered (species vs. structural diversity).     

Effects of fragmentation on forest structure and litter dynamics in Atlantic rainforest in Pernambuco, Brazil

This study evaluates the effects of fragmentation on the spatial and temporal dynamics of small litterfall production in Atlantic rainforest in Pernambuco State, Brazil. Litterfall was collected for 24 months at two 0.2 ha sites, located in the forest edge zone and the forest interior, within a rainforest patch of about 300 ha. Structural parameters of both forest sites were recorded. Litter was sorted into six fractions (foliage, twigs, buds/flowers, fruits/seeds, peduncles, rest), dried and weighed. The interior forest plot contained 314 live trees with a dbh 5 cm and a stand basal area of 41.8±8.7 m², whereas the forest edge contained 211 live trees and a stand basal area of 23.4±3.6 m². Total small litterfall was extraordinarily high and totalled 12.62±4.73 t ha⁻¹ yr⁻¹ in interior forest and 14.74±2.78 t ha⁻¹ yr⁻¹ in forest edge. High litterfall rates are probably due to a pronounced periodicity, edge effects alter litterfall strongly.     

Biodiversity in species,traits, and structure determines carbon stocks and uptake in tropical forests

Impacts of climate change require that society urgently develops ways to reduce amounts of carbon in the atmosphere. Tropical forests present an important opportunity, as they take up and store large amounts of carbon. It is often suggested that forests with high biodiversity have large stocks and high rates of carbon uptake. Evidence is, however, scattered across geographic areas and scales, and it remains unclear whether biodiversity is just a co‐benefit or also a requirement for the maintenance of carbon stocks and uptake. Here, we perform a quantitative review of empirical studies that analyzed the relationships between plant biodiversity attributes and carbon stocks and carbon uptake in tropical forests. Our results show that biodiversity attributes related to species, traits or structure significantly affect carbon stocks or uptake in 64% of the evaluated relationships. Average vegetation attributes (community‐mean traits and structural attributes) are more important for carbon stocks, whereas variability in vegetation attributes (i.e., taxonomic diversity) is important for both carbon stocks and uptake. Thus, different attributes of biodiversity have complementary effects on carbon stocks and uptake. These biodiversity effects tend to be more often significant in mature forests at broad spatial scales than in disturbed forests at local spatial scales. Biodiversity effects are also more often significant when confounding variables are not included in the analyses, highlighting the importance of performing a comprehensive analysis that adequately accounts for environmental drivers. In summary, biodiversity is not only a co‐benefit, but also a requirement for short‐ and long‐term maintenance of carbon stocks and enhancement of uptake. Climate change policies should therefore include the maintenance of multiple attributes of biodiversity as an essential requirement to achieve long‐term climate change mitigation goals.     

缙云山片断常绿阔叶林小气候边缘效应的初步研究

对缙云山5个片断常绿阔叶林和1个连续常绿阔叶林林缘附近的小气候要素水平梯度分布进行测定.结果表明,各片断阔叶林斑块边缘均存在明显的小气候边缘效应.林缘与林内最高和最低气温、光合有效辐射、最小相对湿度均为干季高于或大于雨季,而地表最高温度则为雨季高于干季;各阔叶林斑块的小气候边缘效应以最大斑块波及林内的深度最浅、最小斑块波及林内的深度最深.     

植物功能性状与森林生态系统服务的关系研究综述

植物功能性状途径是揭示生物多样性与生态系统服务关系的重要视角,尽管植物功能性状与生态系统服务的关系在单一地点的研究取得突出进展,但对于植物功能性状与生态系统服务的关系仍缺乏整体认识。以森林生态系统为对象,通过系统文献检索及筛选,收集了216篇文献,应用整合分析和二分网络分析等方法,探讨了植物功能性状对森林生态系统服务及其权衡与协同关系的影响。结果表明：植物叶片功能性状关注最多,占研究性状数量的48%,生态系统服务中关注最多是生物量、土壤肥力、病虫害控制和固碳服务;81.1%的植物功能性状与生态系统服务关系组表现为稳定的正向或负向关系,而关联植物功能性状多的生态系统服务（生物量、固碳服务、土壤水分、土壤肥力和病虫害控制）往往与植物功能性状表现为不稳定关系;森林生态系统中存在6组"植物功能性状-生态系统服务簇（简称"性状-服务簇"）：水循环相关的性状-服务簇、土壤保持相关的性状-服务簇、物质生产相关的性状-服务簇、灾害控制相关的性状-服务簇、养分循环相关的性状-服务簇和授粉相关的性状-服务簇,揭示了各性状-服务簇内生态系统服务的权衡或协同关系以及与各性状-服务簇关系密切的植物功能性状。该研究从总体上阐明了植物功能性状与森林生态系统服务关系的研究重点和进展、揭示了植物功能性状对森林生态系统服务影响效应的方向和强度,可为深化森林生态系统服务形成机制认识以及协调生态系统服务权衡关系提供科学依据。     

Woody debris stocks in different secondary and primary forests in the subtropical Ailao Mountains, southwest China

Woody debris (WD), including coarse woody debris (CWD) and fine woody debris (FWD), is an essential structural and functional component of many ecosystems, particularly in montane forests. CWD is considered to be the major part in forest WD and it is primarily composed of logs, snags, stumps and large branches, while FWD mainly consists of small twigs. Attributes of dead woody material may change in accordance with trends in stand dynamics. The primary forest (primary montane moist evergreen broad-leaved forest) in Ailao Mountain National Nature Reserve (NNR) preserves the largest tract of natural vegetation in China. The Alnus nepalensis (D. Don) association, Populus bonatii (Levl.) association and secondary Lithocarpus association represent the secondary and chronological types following human disturbance by fires and logging under different intensity. The mass and composition of coarse woody debris (CWD, ≥10 cm in diameter) and fine woody debris (FWD, 2.5–10 cm in diameter) were inventoried in a primary forest and its three secondary counterparts. Estimates of total mass of woody debris across secondary types to primary forest ranged from 2.4 to 74.9 Mg ha⁻¹. The lowest value was found in the A. nepalensis association and the highest values were in the primary forest of which logs are the considerable differences. The ratios of CWD to FWD were low in the secondary types (about 1–4) but high in the primary forest (above 15). Our results suggested that for the recovery of woody debris in the secondary forest, it might last longer than the age of the oldest successional stage studied. Yang Lipan and Ma Wenzhang contributed equally to this work.     

Environmental,structural, and taxonomic diversity factors drive aboveground carbon stocks in semi-deciduous tropical rainforest strata in Cameroon

Forest stratification plays a crucial role in the interception of light and plants' photosynthetic activities. However, there is still a lack of information on the contribution of tropical forest stratification to its functioning, despite the increasing number of studies. Here, we analysed from a perspective of the whole tree community (WTC) and forest strata (i.e., large trees, understory trees, and small stems), the relationship between abiotic, biotic factors and aboveground Carbon (AGC). The abiotic factors-AGC relationships were positive for all strata and WTC. However, soil factors-AGC relationship was stronger for small stems and understorey, while topography factor-AGC relationship was stronger for large trees and WTC. Tree size inequality-AGC relationship was positive and much stronger for WTC, large trees and small stems. In addition, a species diversity-AGC relationship was found positive only for large trees and WTC. These results highlight the niche complementarity effect for driving positive relationships of species diversity and individual tree size variation with aboveground biomass at large tree strata and WTC. The lack of positive effect of species diversity on AGC for understorey and small stems strata might be attributable to the selection effect or resource complementarity among species.     

Ethnobiology, socio-economics and management of mangrove forests: A review

There is growing research interest in the ethnobiology, socio-economics and management of mangrove forests. Coastal residents who use mangroves and their resources may have considerable botanical and ecological knowledgeable about these forests. A wide variety of forest products are harvested in mangroves, especially wood for fuel and construction, tannins and medicines. Although there are exceptions, mangrove forest products are typically harvested in a small-scale and selective manner, with harvesting efforts and impacts concentrated in stands that are closer to settlements and easiest to access (by land or by sea). Mangroves support diverse, local fisheries, and also provide critical nursery habitat and marine productivity which support wider commercial fisheries. These forests also provide valuable ecosystem services that benefit coastal communities, including coastal land stabilization and storm protection. The overlapping of marine and terrestrial resources in mangroves creates tenure ambiguities that complicate management and may induce conflict between competing interests. Mangroves have been cut and cleared extensively to make way for brackish water aquaculture and infrastructure development. More attention is now given to managing remaining forests sustainably and to restoring those degraded from past use. Recent advances in remotely sensed, geo-spatial monitoring provide opportunities for researchers and planners to better understand and improve the management of these unique forested wetlands.     

A preliminary assessment of rain throughfall beneath Portulacaria afra canopy in subtropical thicket and its implications for soil carbon stocks

Subtropical thicket dominated by the leaf- and stem-succulent tree Potulacaria afra (spekboom) accumulates extraordinarily high amounts of soil organic carbon for a semi-arid ecosystem. This has been attributed to high leaf litter production of canopy trees — especially spekboom — and the relatively cool beneath-canopy temperatures, which reduces mineralization of organic matter. High rainfall interception by the dense thicket canopy may also contribute to reduced mineralization of soil organic carbon stocks via a reduced Birch effect (wet-dry cycles) and overall reduced moisture of organic matter. Here we provide preliminary data on one easily measurable component of canopy interception, namely throughfall, which is the amount of rain falling on the canopy that is not intercepted by the canopy or diverted as stemflow. For 23 rainfall events > 1 mm in the period Jan-Jun 2006, we measured 275 ± 21 mm gross rainfall at three spekboom thicket sites. Mean throughfall was 56.4% across all events and ≤ 20% for small (≤ 5 mm) events. These values are the lowest recorded in the literature. Throughfall in tropical and temperate forests ranges from 70 to 90%, Mediterranean woodland trees 70-80%, and Savanna trees 75-84%. The low rates of throughfall recorded in this study support the hypothesis that the extreme accumulation of soil organic carbon in thicket soils is partly due to interception of rainfall and concomitant constraints on soil microbial activity. The extraordinary high interception of rainfall by the spekboom thicket canopy warrants further research at the ecosystem level.     

Assessing the effectiveness of community managed forests for plant diversity conservation in Meghalaya,Northeast India

In the state Meghalaya, northeast India, >80% of the forest lands are owned by local communities and managed by traditional institutions. These forests are under severe threats due to a number of human disturbances. The present study was conducted to assess the plant diversity and identify the community forests for priority conservation in Khasi Hills of Meghalaya. Floristic explorations carried out in the 87 forests reveals the presence of 1300 plant species of which 400 are either rare, endemic or threatened. Of the different forest categories, reserve forests had the highest number of species (1190), followed by sacred forests (987 species) and village forests (786 species). Majority of the forests (56) had high-species richness, irreplaceability level (42 forests) and vulnerability level (54). In terms of area, 13.8% (1666.8 ha) fall under low risk while 1855 ha under high risk zone. High risk zone was mostly represented by village forests. An area of 7661.56 ha of community forests falls under high priority category and hence calls for immediate conservation actions. The conservation priority map generated in the present study will help to concentrate the protection strategy to the demarcated and adjoining areas and help conservationists and planners to evolve effective strategies for conservation of the community forests.     

甘肃省森林碳储量现状与固碳速率

针对森林碳平衡再评估的重要性和区域尺度森林生态系统碳库量化分配的不确定性, 该研究依据全国森林资源连续清查结果中甘肃省各森林类型分布的面积与蓄积比重以及林龄和起源等要素, 在甘肃省布设212个样地, 经野外调查与采样、室内分析, 并对典型样地信息按照面积权重进行尺度扩展, 估算了甘肃省森林生态系统碳储量及其分布特征。结果表明: 甘肃省森林生态系统总碳储量为612.43 Tg C, 其中植被生物量碳为179.04 Tg C, 土壤碳为433.39 Tg C。天然林是甘肃省碳储量的主要贡献者, 其值为501.42 Tg C, 是人工林的4.52倍。天然林和人工林的植被碳密度均表现为随林龄的增加而增加的趋势, 同一龄组天然林植被碳密度高于人工林。天然林土壤碳密度从幼龄林到过熟林逐渐增加, 但人工林土壤碳密度最大值主要为近熟林。全省森林植被碳密度均值为72.43 Mg C·hm^-2, 天然林和人工林分别为90.52和33.79 Mg C·hm^-2。基于森林清查资料和标准样地实测数据, 估算出全省天然林和人工林在1996年的植被碳储量为132.47和12.81 Tg C, 2011年分别为152.41和26.63 Tg C, 平均固碳速率分别为1.33和0.92 Tg C·a^-1。甘肃省幼、中龄林面积比重较大, 占全省的62.28%, 根据碳密度随林龄的动态变化特征, 预测这些低龄林将发挥巨大的碳汇潜力。     

Dynamics of carbon stocks in soils and detritus across chronosequences of different forest types in the Pacific Northwest, USA

We investigated variation in carbon stock in soils and detritus (forest floor and woody debris) in chronosequences that represent the range of forest types in the US Pacific Northwest. Stands range in age from <13 to >600 years. Soil carbon, to a depth of 100 cm, was highest in coastal Sitka spruce/western hemlock forests (36±10 kg C m^?2) and lowest in semiarid ponderosa pine forests (7±10 kg C m^?2). Forests distributed across the Cascade Mountains had intermediate values between 10 and 25 kg C m^?2. Soil carbon stocks were best described as a linear function of net primary productivity (r²=0.52), annual precipitation (r²=0.51), and a power function of forest floor mean residence time (r²=0.67). The highest rates of soil and detritus carbon turnover were recorded on mesic sites of Douglas‐fir/western hemlock forests in the Cascade Mountains with lower rates in wetter and drier habitats, similar to the pattern of site productivity. The relative contribution of soil and detritus carbon to total ecosystem carbon decreased as a negative exponential function of stand age to a value of ～35% between 150 and 200 years across the forest types. These age‐dependent trends in the portioning of carbon between biomass and necromass were not different among forest types. Model estimates of soil carbon storage based on decomposition of legacy carbon and carbon accumulation following stand‐replacing disturbance showed that soil carbon storage reached an asymptote between 150 and 200 years, which has significant implications to modeling carbon dynamics of the temperate coniferous forests following a stand‐replacing disturbance.     

亚热带区4种林地土壤微生物生物量碳氮磷及酶活性特征

在位于亚热带丘陵区的长沙县大山冲林场选取地域毗邻、环境条件(立地、土壤、气候)基本一致的杉木人工林(CL)和3种次生林:马尾松-柯(又名石栎)针阔混交林(PM-LG)、南酸枣落叶阔叶林(CA)、柯-青冈常绿阔叶林(LG-CG),每种林地随机设置5个20 m×20 m的样地,分别采集表层(0—15 cm)和亚表层(15—30 cm)土壤样品,测定土壤微生物生物量碳(B_C)、氮(B_N)、磷(B_P)和蔗糖酶(INV)、脲酶(URE)、酸性磷酸酶(ACP)、过氧化氢酶(CAT)活性,分析4种林地土壤微生物生物量和酶活性及其与土壤化学性质的关系。结果表明:表层和亚表层土壤B_C、B_N、B_P和ACP活性依次为:CA LG-CG PM-LG CL,INV和URE活性依次为:LG-CG CA PM-LG CL,CAT活性依次为:CA PM-LG LG-CG CL,说明森林植被恢复对土壤微生物生物量和酶活性有明显的促进作用。通径分析表明,土壤B_C、B_N、B_P的直接影响因素和主要影响因素分别为SOC和TN/TP,TN和TN/TP,TP和SOC/TP,而TN/TP与B_C之间,TN与B_N之间具有较强的负相关;INV、ACP活性的直接影响因素主要是TN、TN/TP,其中TN/TP与INV、ACP活性具有较强的负相关;URE、CAT活性分别为B_P/TP和B_P,B_C/SOC和SOC,其中B_P与URE活性具有较强的负相关,B_C/SOC、SOC两者与CAT活性具有较强的正相关。此外,土壤B_C、B_N、B_P以及INV、URE、ACP、CAT活性的剩余余项通径系数较低,说明土壤化学性质对土壤微生物生物量,以及土壤化学性质和微生物生物量对土壤酶活性具有较大的影响。土壤B_C、B_N、B_P之间及其与土壤酶活性呈显著正相关。     

Effects of biodiversity,stand factors and functional identity on biomass and productivity during the restoration of subtropical forests in Central China

恢复梯度上华中亚热带森林生物多样性、林分因子及功能特性对生物量、生产力的影响 草地群落上进行的控制实验大都发现生物多样性对生态系统功能有显著促进作用。然而,在天然林中,多样性与林分因子、群落功能特性的相对作用大小仍存在争议。本文在森林恢复梯度上,研究这3类因素对生物量和生产力的相对影响。我们在湖北神农架设置了处于不同恢复阶段的24块(600 m²)亚热 带森林样地,计算了林分生物量和生产力。选择5个关键的植物功能性状,并计算了群落的功能多样性(功能丰富度、功能均匀度和功能离散度)和性状的加权平均值(CWM)。使用一般线性模型(GLMs)、变异分离等方法探究林分因子(密度、林龄、群落最大树高等)、功能特性、物种和功能多样性对生物量和生产力的相对重要性。研究结果表明,随着森林恢复,林分生物量和生产力显著增加,群落物种丰富度显著增加,而功能离散度显著降低。变异分离结果表明,多样性对生物量和生产力的单独效应不显著,但可能通过与林分因子和功能特性的协同效应来影响生物量和生产力。总体而言,我们发现林分因子对亚热带森林生物量和生产力的影响最大,功能特性显著影响生产力,但不影响生物量。这些结果说明,在森林经营中,调整林分结构和群落物种特性是提高森林碳储量和固碳潜力的有效途径。     

毛竹扩张对次生常绿阔叶林物种组成、结构与多样性的影响

毛竹(Phyllostachys edulis)向邻近次生常绿阔叶林扩张现象明显, 极大地影响了常绿阔叶林的生态功能, 但关于其扩张对常绿阔叶林的群落结构与生物多样性影响的后效研究较少。本文采用时空替代法, 在江西井冈山国家级自然保护区沿毛竹扩张方向, 依次设置毛竹林、竹阔混交林和常绿阔叶林样地, 比较分析了扩张前后群落物种相似性、群落结构和多样性指数等特征。结果表明: (1)毛竹林与常绿阔叶林乔木层、灌木层和草本层的Bray-Curtis相似性指数很小, 分别为0.003、0.046和0.030。(2)毛竹林的垂直结构呈“>”型, 高度12-14 m区间的多度百分比达33.3%, 径级结构集中分布于5-10 cm区间, 达总数的90.0%; 常绿阔叶林的垂直结构为“L”型, 高度2-4 m的物种数占54.3%, 径级分布范围较广, 4个较大径级区间的平均百分比为10.3%。(3)乔木层的Shannon-Wiener指数由常绿阔叶林的2.56降至毛竹林的0.06, 降幅高达98%; 灌木层也由2.58降至2.03, 降幅21%。以上结果说明, 毛竹扩张会导致次生常绿阔叶林群落组成和结构简化、物种多样性下降, 对森林生态系统功能产生负面影响。     

Floristic variation in ecotonal areas: Patterns,determinants and biogeographic origins of subtropical forests in South America

We present the first quantification of forest community composition and its relationship with environmental factors in South American subtropical Atlantic Forests. In this region, rain, seasonally dry and mixed forests form an ecotonal zone near the parallel of latitude 30°S. To investigate how well current knowledge on climatic effects and biogeographic distribution apply to subtropical ecotones, we tested the following expectations: (i) there is a floristic longitudinal gradient correlated to altitudinal and climatic gradients; (ii) climatic variables are more important than soil factors in shaping floristic composition; and (iii) there are three floristic regions in the southernmost limit of the Atlantic Forest biome that are expected to be distinct in composition, structure and biogeographical origin. We examined floristic composition and its relationship with environmental factors across 52 1‐ha permanent study areas in subtropical Brazil, containing in total 269 tree species ≥ 9.5 dbh (diameter at breast height). Climatic data, related to rainfall seasonality and temperature, as well as soil properties, were compiled from published sources or global data banks. Expectations one and two were confirmed, but expectation three was only partially met. Hierarchical cluster analysis divided the southernmost Atlantic Forests into four major groups (Rain, Seasonally Dry, Western Mixed and Eastern Mixed Forests). Overall, the tested environmental variables differed significantly among the four regions. Using indicator species analysis, we distinguished 46 indicator species, which had significant environmental preferences for one floristic region. These species can be used as indicators of environmental conditions or to determine to which floristic region a certain forest belongs. Biogeographic distributions differed between floristic groups, supporting the interpretation that Eastern Mixed Forests are relict forests of a temperate forest of Andean origin that occurred during colder palaeoclimates. Western Mixed Forests represent the main floristic ecotone between Seasonally dry and Eastern Mixed Forests.     

Landscape patterns and plant species diversity of forest reserves in the Kanto region, Japan

Plant species richness of twenty old-growth forest reserves in the cool-temperate zone in the Kanto region, Japan were investigated to detect the effect of forest fragmentation. The species richness of trees and forest floor plants were analyzed by multiple regression models relating to nine variables on the characteristics of landscape, local habitat and forest stand. The total species diversity did not have a significant correlation with any variables of landscape patterns. In this study, single large reserve in the SLOSS discussion did not seem very effective to preserve more species. However, forest reserves in large patches tend to have relatively infrequent species. Large patches of natural forests were regarded as one of the important factors to preserve infrequent species.