Genetic Divergence During Long‐term Isolation in Highly Diverse Populations of Tropical Trees Across the Eastern Arc Mountains of Tanzania

The Eastern Arc Mountains are believed to support some of the oldest tropical forest in the world. The current distribution of this forest is highly fragmented due to a combination of long‐term effects of past changes in global climate and more recent deforestation. We sought to explore the hypothesized antiquity and long‐term isolation of the Eastern Arc montane forests based on an assessment of the geographical distribution and interspecies similarity of chloroplast DNA sequence variation in five forest trees. Data were used to investigate regional patterns of diversity and population structure based on intraspecific phylogenies, and results were interpreted against hypotheses on ecosystem age and connectivity. Regional diversity was high, with up to 22 chloroplast DNA haplotypes being recorded within a species across the sampled populations. Geographical concordance of genetic and geographic structure was weak to absent in all species and there was little similarity of genetic structure between species. Haplotype sharing between mountain blocks was extremely limited. The generally weak phylogeographical structure, in conjunction with high regional diversity and genetic uniqueness of individual mountain forests does not support the assumption of widespread genetic connectivity of the mountain forests, indicating instead a pattern of past isolation and ongoing diversification. Our findings substantially add to understanding patterns of diversity in this region and lend weight to calls to use more sophisticated biodiversity assessments when setting regional conservation and research funding priorities.     

Wildfires in the western Canadian boreal forest: Landscape patterns and ecosystem management

Abstract. Mimicking of natural disturbance for ecosystem management requires an understanding of the disturbance processes and the resulting landscape patterns. Since fire is the major disturbance in the boreal forest, three widely held beliefs about fire behavior and resulting landscape patterns are examined in light of the empirical evidence available. These beliefs are: (1) that there is a ‘natural’ fire frequency for boreal ecosystems; (2) that the landscape mosaic created by wildfire is generally one of small, younger patches embedded within a matrix of older forest; and (3) that forest flammability is largely controlled by fuel accumulation. Despite the apparently logical basis for such beliefs, they are not well supported by empirical evidence. This discrepancy is explained by problems such as failure to appreciate the relationship between number of fires and area burned and inappropriate extrapolations or generalizations from other regions and vegetation types. The most important implications for management are that the natural disturbance processes producing landscape patterns in the boreal forest generally operate at much larger scales than management units, and that humans may have more indirect (through landuse change) rather than direct (through fire suppression) effects on the frequency of wildfires.     

Fire as a Recurrent Event in Tropical Forests of the Eastern Amazon: Effects on Forest Structure,Biomass, and Species Composition1

The effects of fire on forest structure and composition were studied in a severely fire-impacted landscape in the eastern Amazon. Extensive sampling of area forests was used to compare structure and compositional differences between burned and unburned forest stands. Burned forests were extremely heterogeneous, with substantial variation in forest structure and fire damage recorded over distances of <50 m. Unburned forest patches occurred within burned areas, but accounted for only six percent of the sample area. Canopy cover, living biomass, and living adult stem densities decreased with increasing fire inrensiry / frequency, and were as low as 10–30 percent of unburned forest values. Even light burns removed >70 percent of the sapling and vine populations. Pioneer abundance increased dramatically with burn intensity, with pioneers dominating the understory in severely damaged areas. Species richness was inversely related to burn severity, but no clear pattern of species selection was observed. Fire appears to be a cyclical event in the study region: <30 percent of the burned forest sample had been subjected to only one burn. Based on estimated solar radiation intensities, burning substantially increases fire susceptibility of forests. At least 50 percent of the total area of all burned forests is predicted to become flammable within 16 rainless days, as opposed to only 4 percent of the unburned forest. In heavily burned forest subjected to recurrent fires, 95 percent of the area is predicted to become flammable in <9 rain-free days. As a recurrent disturbance phenomenon, fire shows unparalleled potential to impoverish and alter the forests of the eastern Amazon.     

Mycorrhizal associations and soil properties of native Allanblackia stuhlmannii stands in the Eastern Usambara Mountains,Tanzania

Allanblackia stuhlmannii is a tree species currently under domestication. Potential mycorrhizal relationships of A. stuhlmannii and soil properties of native stands were investigated to determine the soil–environmental requirements of the species. Roots and soil samples were collected from five sites with A. stuhlmannii stands along an altitudinal transect in Amani Nature Reserve, Tanzania. Mycorrhizal status was investigated by combining microscopy with molecular analysis of the fungal communities. Soil adjacent to the A. stuhlmannii seedlings was analysed for physical and chemical properties and the sites were characterised. We showed that A. stuhlmannii form symbiosis with arbuscular mycorrhizal fungi, and that there was a diverse microbiome associated with the roots. The soils, classified as Ferralsol and Acrisol, were very well drained, had a pH_CaCl2 generally at or below 4, high exchangeable acidity and content of sesquioxides and low effective cation exchange capacity and concentrations of most nutrients. We conclude that A. stuhlmannii is tolerant to high Al availability and possesses mechanisms for acquisition of P and other macronutrients at low soil availability, possibly through mycorrhizal symbiosis. However, being adapted to low‐pH soils, it may be less efficient in acquiring Fe, Mn and/or Zn at higher soil pH. Thus, it may be most suited to introduction on farms situated on acid soils.     

Changing places: how the results of new field work in the Rubeho Mountains influence conservation priorities in the Eastern Arc Mountains of Tanzania

The Rubeho Mountains are a poorly studied mountain block within the Eastern Arc Mountain range of Tanzania and Kenya. We present the results of field surveys for vertebrates undertaken during the period February 2000 to December 2002. One hundred and twelve man‐days of surveys recorded 35 mammal, 107 bird, ten reptile and nine amphibian species, including eleven species endemic and seven near‐endemic to the Eastern Arc, with one species new to science. Of these, nine species are regarded as threatened with extinction. The new survey data significantly elevate the biological importance of the Rubehos within the Eastern Arc range. Further analyses highlight how the overall biological ranking of the Eastern Arc mountain blocks is correlated with survey effort. The majority of the forest habitat on the Rubehos is contained in three national (Central Government) Forest Reserves (Mang'alisa, Mafwomero and Ukwiva). Our surveys recorded high levels of disturbance to the forest habitat in all three reserves and we draw attention to the need for additional conservation investment in this area.     

Rutland Water Nature Reserve: concept,design and management

This paper illustrates how practical conservation management has helped to create a nature reserve of international importance for wildfowl. The development of existing and introduced habitats has produced a wide diversity of fauna and flora without causing an unnatural ecological balance and close liaison with other reservoir users has establoshed zoning areas free from disturbance resulting in both man and birds benefiting from such agreements.     

The discordance of diversification: evolution in the tropical‐montane frogs of the Eastern Arc Mountains of Tanzania

Species with similar geographical distribution patterns are often assumed to have a shared biogeographical history, an assumption that can be tested with a combination of molecular, spatial, and environmental data. This study investigates three lineages of Hyperolius frogs with concordant ranges within the Eastern Afromontane Biodiversity Hotspot to determine whether allopatric populations of co‐distributed lineages shared a parallel biogeographical response to their shared paleoclimatic histories. The roles of refugial distributions, isolation, and climate cycles in shaping their histories are examined through Hierarchical Approximate Bayesian Computation, comparative phylogeography, and comparisons of current and past geographical distributions using ecological niche models. Results from these analyses show these three lineages to have independent evolutionary histories, which current spatial configurations of sparsely available habitat (montane wetlands) have moulded into convergent geographical ranges. In spite of independent phylogeographical histories, diversification events are temporally concentrated, implying that past vicariant events were significant at the generic level. This mixture of apparently disparate histories is likely due to quantifiably different patterns of expansion and retreat among species in response to past climate cycles. Combining climate modelling and phylogeographical data can reveal unrecognized complexities in the evolution of co‐distributed taxa.     

Environmental change and rain forests on the Sunda shelf of Southeast Asia: drought, fire and the biological cooling of biodiversity hotspots

Environmental change during the Quaternary period has caused changes in the composition and structure of vegetation on the Sunda shelf of Southeast Asia. Climatic conditions drier than the present, particularly during the peak of the last ice age, led to a reduction in the extent of rain forests. Most recently, there has been a close association between drought and the occurrence of major, rain forest fires. Although many rain forest trees show adaptations to periodic drought, this is not the case for frequent or intense fires. Over evolutionary time-scales, major fires may thus have been largely confined to driver vegetation types, such as monsoon and deciduous forests, and only infrequently penetrated rain forest areas. Continental-scale distribution patterns for rain forest species reveal a number of biodiversity hotspots that are consistent for a broad range of taxonomically unrelated taxa. These biodiversity hotspots account for a relatively small part of the total extent of rain forest; they may also represent ecologically relatively stable areas. This paper discusses the location and extent of biodiversity hotspots on the Sunda shelf within the context of past and present environmental change. It finds that whatever the history of biodiversity hotspots, they are increasingly threatened by contemporary environmental change, notably a trend towards increasingly frequent and intense fires. The paper concludes that the trend is likely to continue, without major changes in those activities that degrade and precondition to fire remaining areas of rain forest.     

Modern ticuna swidden-fallow management in the Colombian Amazon: Ecologically integrating market strategies and subsistence-driven economies?

The past failure of large-scale, rural development in Amazonia has emphasized the value of small-scale, swidden-fallow management practices. The management strategies used by indigenous cultivators are well-documented, but few studies have examined how absorption by market-based economies may affect the economic and ecological stability of the agricultural system. In this study, we provide a detailed account of swidden-fallow management as it is practiced at Las Palmeras, Amazonas, Colombia; moreover, we assessed the effect of a shift from subsistence to market-directed production. A total of 68 species were selectively managed in the swidden/fallow system. Seventy-seven percent of species at the site were managed for subsistence only, 22% were managed with a view to selling surplus at market. Only one species, Cedrela odorata, was managed solely for market production. A shift from subsistence-based to market-directed production may lower the ecological and economic stability of the system at Las Palmeras. Nonperishable production strategies, such as for timber production, appear to provide the most secure approach toward market integration.     

Connectivity, sustainability, and yield: bridging the gap between conventional fisheries management and marine protected areas

A substantial shift toward use of marine protected areas (MPAs) for conservation and fisheries management is currently underway. This shift to explicit spatial management presents new challenges and uncertainties for ecologists and resource managers. In particular, the potential for MPAs to change population sustainability, fishery yield, and ecosystem properties depends on the poorly understood consequences of three critical forms of connectivity over space: larval dispersal, juvenile and adult swimming, and movement of fishermen. Conventional fishery management describes the dynamics and current status of fish populations, with increasing recent emphasis on sustainability, often through reference points that reflect individual replacement. These compare lifetime egg production (LEP) to a critical replacement threshold (CRT) whose value is uncertain. Sustainability of spatially distributed populations also depends on individual replacement, but through all possible paths created by larval dispersal and LEP at each location. Model calculations of spatial replacement considering larval connectivity alone indicate sustainability and yield depend on species dispersal distance and the distribution of LEP created by species habitat distribution and fishing mortality. Adding MPAs creates areas with high LEP, increasing sustainability, but not necessarily yield. Generally, short distance dispersers will persist in almost all MPAs, while sustainability of long distance dispersers requires a specific density of MPAs along the coast. The value of that density also depends on the uncertain CRT, as well as fishing rate. MPAs can increase yield in areas with previously low LEP but for short distance dispersers, high yields will require many small MPAs. The paucity of information on larval dispersal distances, especially in cases with strong advection, renders these projections uncertain. Adding juvenile and adult movement to these calculations reduces LEP near the edges in MPAs, if movement is within a home-range, but more broadly over space if movement is diffusive. Adding movement of fishermen shifts effort on the basis of anticipated revenues and fishing costs, leading to lower LEP near ports, for example. Our evolving understanding of connectivity in spatial management could form the basis for a new, spatially oriented replacement reference point for sustainability, with associated new uncertainties.     

自然保护区管理中生态与娱乐属性的权衡:一个选择实验的应用

随着自然保护区多样化的发展以及旅游需求的日益增长,保护区管理者面临着保护生态环境与满足娱乐需求的双重压力,这使得保护区管理者需要更多的信息进行决策。以中国东北部的扎龙国家级自然保护区为例,进行了一项选择实验,选取生物多样性、预期游客数量、景区的环境教育设施、门票价格等4个属性,分别采用多项logit模型、随机参数logit模型和潜在分类模型,探究游客在可能存在冲突的管理优先级之间的偏好。目的是揭示游客如何评价保护区不同的管理属性,以及各属性的边际支付意愿和偏好,并根据这些信息制定有效的保护区管理指南。研究结果表明生物多样性是保护区游客最关注的属性,并且游客对于生态属性的关注度高于娱乐属性。因此,保护区管理者应首先维持并改善生物多样性及其生态环境,在不破坏生态环境的基础上开发具有环境教育作用的娱乐服务。此外,研究发现游客可分为生态友好型和价格敏感型两种类别,不同类型的群体对游览保护区存在不同偏好,女性和年轻的受访者对生态更友好,男性和年长的受访者对价格更敏感。本文的贡献是将某一方面属性价值的描述扩展到涵盖多个管理属性的研究,并为保护区管理中生态与娱乐的权衡问题提供了更具体的见解。     

The socioeconomic conditions determining the development, persistence, and decline of forest garden systems

There is a range of forest management systems between pure extraction and plantation systems. Such “intermediate systems” range from wild forests modified for increased production of selected products to anthropogenic forests with a high-density of valuable species growing within a relatively diverse and complex structure. These systems, classed here as “Forest Garden Systems” (FGS), have important socioeconomic and ecological benefits, and yet they have been largely overlooked by researchers, development practitioners, and policy makers. Based on case examples and the authors’ experience, this paper analyzes the socioeconomic and institutional factors that explain the development, persistence, and decline of FGS. These systems combine productivity and biodiversity values and are important components in the diverse economic systems of their managers. As such, the model warrants increased attention to protect existing values, to support the adaptation of existing systems to changing circumstances, and to inform the development of new models of integrated forest management     

火干扰对云南苍山地表蜘蛛群落生活型组成及季节动态的影响

为揭示不同蜘蛛类群对火干扰的敏感程度及蜘蛛群落外貌对环境变化产生的响应, 本文选取苍山针阔混交林2007年火烧迹地作为调查样地, 以无火烧记录的样地为对照, 运用陷阱法调查地表蜘蛛群落生活型及季节动态。研究结果显示: (1)火烧迹地中朱氏狂蛛(Zelotes zhui)(相对优势度 DV' =33.03)、晨豹蛛(Pardosa chionophila) (DV'=22.53)和西菱头蛛一种(Sibianor sp.1)(DV'=8.75)占明显优势; 而对照样地中龙隙蛛一种(Draconarius sp.2) (DV'=63.50)占绝对优势; (2)火烧迹地的定居型蜘蛛相对多度为25.82%, 显著少于游猎蜘蛛(P<0.001); 而对照样地的定居型蜘蛛相对多度为92.07%, 显著高于游猎蜘蛛(P<0.001); (3)火烧迹地地表蜘蛛优势类群随季节更替明显, 在夏季和冬季多度为低谷期; 对照样地优势类群稳定, 为漏斗蛛科蜘蛛。研究表明, 火干扰改变了苍山针阔混交林地表蜘蛛群落生活型组成, 降低了定居型蜘蛛的相对多度和地表蜘蛛群落的季节稳定性。     

深圳福田红树林鸟类自然保护区管理策略初探

位于深圳经济特区的福田红树林鸟类自然保护区,是城市边缘一块不可多得的生物多样性宝地。面对经济建设的快速发展和市区的不断扩张,福田自然保护区正承受着来自各方面的巨大压力。如何在积极推动保护区立法的同时,通过开放式生物多样性保护管理,主动参与地方经济建设,实现与周边社区、地方政府和各相关社会利益集团结成合作伙伴关系,是本文探讨的重点。     

面向生态系统服务的森林生态系统经营:现状、挑战与展望

森林生态系统是地球陆地生态系统的主体,它具有很高的生物生产力和生物量以及丰富的生物多样性,对全球生态系统和人类经济社会发展起着至关重要和无可替代的作用。伴随着人口的不断增长和经济社会的迅猛发展,对森林资源和森林生态系统服务的需求不断高涨,而且人类对森林资源价值的认识也发生了很大程度的改变。推进森林资源可持续经营,增加森林总量、提高森林质量、增强生态功能,已成为中国林业可持续发展乃至推进中国生态文明建设和建设美丽中国的战略任务。本文全面综述了森林生态系统经营发展历程,分析了森林生态系统经营的现状和存在问题,在此基础上,提出整合基于生态系统管理与满足现代人类福祉对森林多重需求的新的森林生态系统经营理念,面向生态系统服务的森林生态系统经营理念是未来的发展趋势。森林经营发展战略表现为:1)从单纯的森林面积数量扩张,转变到提高单位面积的森林生产力和森林质量;2)从单一追求木材生产逐步转变为多目标经营,将森林林产品单一的经营目标转变为广泛的生态、经济和社会等多目标经营;3)森林经营重点从林分水平转变为森林景观的经营,强调森林景观的时空异质性和动态变化,权衡和协同多种生态系统的服务功能,倡导森林景观的多样性和连通性,提高森林与其它土地利用模式镶嵌构成的复合景观的可持续性和稳定性,增强森林生态系统对气候变化影响的适应能力;4)森林生态系统经营将从依赖传统经验的主观决策转变为信息化、数字化和智能化的决策,发展森林生态系统经营决策支持系统和森林景观恢复与空间经营规划系统。     

Where the fish swim above the birds: configurations and challenges of wetland restoration in the Po Delta,Italy

Wetland and estuary restoration presents a number of complex challenges that are primarily social, cultural, economic, and governance‐related rather than ecological. Here we consider the case of wetland restoration in the Po Delta, Italy. Wetland restoration of the Po Delta is a goal of a broad range of actors in the region and this project is a response to local calls for action. We investigate why local stakeholders are unsatisfied with apparently successful restoration projects, and appraise the factors that favor both the fulfillment of environmental targets and establishment of cooperative relations. We suggest that historical legacies of land use in the Po Delta have influenced current governance practices in a complex and fragmented governance context. Also, patterns of wetland restoration and wetland management practices differ between wetland types, and their outcomes may be influenced by the number of stakeholders involved, funding, and ability to generate direct revenues from management. However, there seem to be no blueprint solutions to successful wetland management and wetland restoration, and results are uneven at the landscape scale and often depending on contingencies. Maintaining traditional practices that retain cultural importance may be seen as part of restoration by local people. As a landscape that is highly anthropogenic and in continuous motion, we argue that the Delta exemplifies some of the challenges that restoration will face in a world increasingly characterized by novel ecosystems. We suggest actions that could contribute to enhancing wetland restoration outcomes in the Po Delta.     

Prescribed fire is associated with increased floral richness and promotes short-term increases in bee biodiversity in the ponderosa pine forest of the Southern Rocky Mountains

1. Managed low-severity surface fires are frequently implemented in efforts to restore disturbance processes to forests of North America; although the effects of managed fire on forest structure are well-studied, few studies investigate whether these disturbances cascade to impact pollinator communities.
2. We analysed bee-habitat relationships in fire-treated (1- and 3-years post-treatment) and non-treated ponderosa pine stands in Colorado to test wild bee population responses.
3. Observed bee richness and α-diversity were highest in stands 1-year post-fire and had more Anthophora, Bombus, Osmia and Lasioglossum spp. in comparison to 3-year post-fire and non-treated stands. Bee functional groups were responsive to treatments, with more below-ground nesting taxa present in stands 3 years post-fire.
4. Floral richness was the highest mid-growing season (June, July) and within 1-year post-fire stands.
5. A model analysing the effects of foraging and nesting habitat variation on bee assemblages indicated positive association between floral richness and bee α-diversity, but negative relationships with stand basal area. Nesting habitat was not associated with variation in bee assemblages.
6. We conclude that managed fire has positive short-term effects on bee biodiversity that are likely mediated by floral richness. However, these effects were not detectable by 3 years post-treatment in the southern Rocky Mountain region.