Forest health status in North America

The forests of North America provide a variety of benefits including water, recreation, wildlife habitat, timber, and other forest products. However, they continue to face many biotic and abiotic stressors including fires, native and invasive pests, fragmentation, and air pollution. Forest health specialists have been monitoring the health of forests for many years. This paper highlights some of the most damaging forest stressors affecting North American forests in recent years and provides some projections of future risks.     

Theory of catastrophic diseases of cultivated plants

Genetically homogeneous plant populations generate selective pressures for pathogens to overcome host resistance. Once a pathogen strain has evolved which overcomes host resistance, a catastrophic collapse of genetically h homogeneous host population can result. The dynamics of such a collapse are discussed by means of a mathematical model. Also, a gametheoretical model shows that high density of the host population may lead to selection for maximum pathogen virulence rather than host-parasite commensalism. The evolution of mutant pathogens is compared with the evolution of insecticide resistance. While time frame estimates are intrinsically difficult to obtain, it is argued that industrial pollution may speed up the evolution of mutant pathogens and may have been responsible for a number of agricultural and horticultural epidemics. The theory may have implications for the clonal propagation of forests.     

基于非点源污染控制的景观格局优化方法与原则

对目前国内外较为常用的基于非点源污染控制的景观格局优化方法及其设计原则进行了系统的评述 ,以促进其推广应用并提高其污染控制效果。还通过分析这些方法在我国的应用前景 ,强调了探索适合我国国情的景观格局优化方法对于控制非点源污染的重要意义。     

Status of forests in Uganda

Trees, forests and woodlands cover about 14% of Uganda’s land surface. Over the last 30–40 years, growth in human population and corresponding increase in demand for forest products for domestic and industrial use, expansion of agricultural land, illegal settlements and weak forest management capacity have adversely affected the status of natural forests in Uganda, particularly the biodiversity. Until recently, little attention had been paid to development of commercial forests which should have provided alternative forest products and services to relieve the pressure on natural forests and conserve biodiversity. As a result, Uganda’s forests have been degraded, and in some cases, the biodiversity has been eroded. There is a need for regular data collection and monitoring of the status of the forests in terms of areal extent, distribution, plantation species introductions and biodiversity.     

Counting primates for conservation: primate surveys in Uganda

Primate census techniques have been developed over the past 35–40 years yet there is still some confusion and great variation in the methods used. This precludes comparisons between sites where different techniques have been used. This paper discusses the variations between the methods that seem to be practiced currently and then describes a census of primates in the forests of western Uganda. Primate density and biomass varied greatly between forests as well as within forests and this is probably related to food availability. Chimpanzee (Pan troglodytes) density was strongly correlated with nest encounter rates from reconnaissance walks in the forest. This result can be used to estimate chimpanzee density in forests where it is difficult to survey this species (e.g., due to security reasons). A total of 4,980 chimpanzee was estimated for Uganda which is higher than previously guessed, but still of conservation concern. Only four forests had more than 500 individuals which gives concern for long-term population viability.     

Separating forest continuity from tree age effects on plant diversity in the ground and epiphyte vegetation of a Central European mountain spruce forest

Forest continuity has been identified as an important factor influencing the structure and diversity of forest vegetation. Primary forests with centuries of continuity are usually more diverse than young secondary forests as forest are colonized only slowly and because the former are richer in old tree individuals. In the present study, performed in unmanaged high-elevation spruce forests of the Harz Mountains, Germany, we had the unique opportunity to separate the effects of forest continuity and tree age on plant diversity. We compared an old-growth spruce forest with century-long habitat continuity with an adjacent secondary spruce forest, which had naturally established on a former bog after 1796 when peat exploitation halted. Comparative analysis of the ground and epiphyte vegetation showed that the plant diversity of the old-growth forest was not higher than that of the secondary forest with a similar tree age of >200 years. Our results suggest that a period of >200 years was sufficient for the secondary forest to be colonized by the whole regional species pool of herbaceous and cryptogam forest plants and epiphytes. Therefore, it is likely that habitat structure, including the presence of old and decaying trees, was more important for determining plant diversity than the independent effect of forest continuity. Our results are probably not transferrable to spruce forests younger than 200 years and highly fragmented woodlands with long distances between new stands and old-growth forests that serve as diaspore sources. In addition, our results might be not transferable to remote areas without notable air pollution, as the epiphyte vegetation of the study area was influenced by SO₂ pollution in the second half of the 20th century.     

Impacts of tropospheric ozone and climate change on net primary productivity and net carbon exchange of China's forest ecosystems

Aim We investigated how ozone pollution and climate change/variability have interactively affected net primary productivity (NPP) and net carbon exchange (NCE) across China's forest ecosystem in the past half century. Location Continental China. Methods Using the dynamic land ecosystem model (DLEM) in conjunction with 10‐km‐resolution gridded historical data sets (tropospheric O₃ concentrations, climate variability/change, and other environmental factors such as land‐cover/land‐use change (LCLUC), increasing CO₂ and nitrogen deposition), we conducted nine simulation experiments to: (1) investigate the temporo‐spatial patterns of NPP and NCE in China's forest ecosystems from 1961–2005; and (2) quantify the effects of tropospheric O₃ pollution alone or in combination with climate variability and other environmental stresses on forests' NPP and NCE. Results China's forests acted as a carbon sink during 1961–2005 as a result of the combined effects of O₃, climate, CO₂, nitrogen deposition and LCLUC. However, simulated results indicated that elevated O₃ caused a 7.7% decrease in national carbon storage, with O₃‐induced reductions in NCE (Pg C year^?1) ranging from 0.4–43.1% among different forest types. Sensitivity experiments showed that climate change was the dominant factor in controlling changes in temporo‐spatial patterns of annual NPP. The combined negative effects of O₃ pollution and climate change on NPP and NCE could be largely offset by the positive fertilization effects of nitrogen deposition and CO₂. Main conclusions In the future, tropospheric O₃ should be taken into account in order to fully understand the variations of carbon sequestration capacity of forests and assess the vulnerability of forest ecosystems to climate change and air pollution. Reducing air pollution in China is likely to increase the resilience of forests to climate change. This paper offers the first estimate of how prevention of air pollution can help to increase forest productivity and carbon sequestration in China's forested ecosystems.     

Ancient woodlands: modern threats

This review discusses the following adverse influences on long-established forests, wood-pastures, and savannas in Europe and other continents: destruction and fragmentation; depletion; pollution and eutrophication; fire and lack of fire; excessive shade; excessive numbers of deer; invasive species and cultivars; infilling of savanna; climate change; and globalization of plant diseases. Human influences on the world's mainland forests and savannas have been pervasive throughout the Holocene, to the extent that recovering 'virgin forest' becomes a somewhat nebulous conservation objective. Present and future threats arise both from increasing human activities and from withdrawal of the human activities that have shaped forests in the past. The severity of different threats depends on so many factors, especially the properties of different plants and animals, that generalization is impossible; however, in the long term, spread of pathogens is probably the most serious threat.     

Population structure and adult plant performance of forest herbs in three contrasting habitats

In Flanders, forests have been subjected to subsequent periods of reclamation and reforestation, leading to a mosaic of forest patches of various ages and with different abiotic conditions, depending on the duration and intensity of the past agricultural activities. While extensive research has been done on the relative importance of dispersal limitation and establishment limitation in explaining colonization patterns of so-called ancient forest plant species, little is known about the viability of populations of these species once they have colonized recent forests. Therefore, a comparative study on population structure and plant performance was carried out for three forest plant species with different colonization capacity ( Primula elatior , Geum urbanum and Arum maculatum ) in three different habitat types: ancient forests, recently established forests and small landscape elements (hedgerows). Contrary to the expectation, it was shown that adult plant performance – a combination of vegetative as well as reproductive characteristics – of the three species was generally higher in recent forests and small landscape elements. This also led to higher seedling densities and proportions in these habitat types. Adult densities, however, were extremely low in newly established forests, suggesting reduced seedling and juvenile survival under these circumstances, probably due to higher light availability and hence increased competition from species like Urtica dioica . Although there might be no immediate establishment limitation, installing a shrub layer in recent forests might enhance survival and result in a stable population structure. Hedgerows on the other hand seemed to contain viable populations of certain forest plant species and can therefore function as an important colonization source when incorporated in recently established forests.     

Rehabilitating degraded forests in Central Europe into self–sustaining forest ecosystems

There is a need for a consistent forest restoration strategy for the `Black Triangle', Central Europe. In the past 50 years, forests in this area have been heavily affected by industrial pollution. Recently, the amount of pollutants has decreased. This means that effective forest restoration programmes can be started. Forest decline must be seen as an ecological disturbance which cannot be solved by applying technical measures only. An ecosystem approach to forest restoration must be introduced into restoration policy and management. Basic principles and working methods of such an approach are briefly described and proposals are made for forest restoration policy, management and research in the area.     

Criteria of rehabilitation of biotic communities in oil-polluted small rivers (by example of the Shava River,Nizhnii Novgorod oblast)

An assessment of the ecological state of the small Shava River (Kstovskii raion, Nizhnii Novgorod oblast) subjected to oil pollution as a result of a pipeline accident in 2007 is presented. On the basis of physical and chemical characteristics of water quality and the results of a study of hydrobiont communities, the degree of the river pollution has been determined and a conclusion about the rehabilitation of communities as a result of the complex effect of recultivation measures and self-purification processes has been made. Criteria for recultivation activity completion have been defined according to hydrobiological indicators (phytoplankton, zooplankton, and zoobenthos).     

Ecological-coenotic characteristics of the bacterial dropsy infection rate in birch forests in the southern part of Middle Siberia (Krasnoyarsk group of areas)

As a result of a phytopathological investigation into birch (Betula pendula) stands in the Krasnoyarsk group of areas (south of Middle Siberia), newly appearing and existing nidi of bacterial dropsy have been discovered. The influence of growth conditions on morbid affection in birch forests and the correlation between disease prevalence and characteristics of forest inventory have been established. The specificities of tree affection within phytocenoses and the influence of disease on the sanitary state of birch forests have been discussed.     

城市森林调控空气颗粒物功能研究进展

受城市扩张、工业发展、汽车保有量增加的影响,空气颗粒物目前已成为诸多城市空气的首要污染物。而城市森林作为城市生态建设中最大的唯一具有自净功能的生态系统,不仅为城市高污染环境下的居民提供了相对洁净的休闲游憩空间,还对净化空气颗粒物起重要作用。从城市森林调控空气颗粒物的机理、分析方法、植物个体、群落及不同类型城市森林调控空气颗粒物的功能差异及其时空变化规律等方面进行阐述。结果表明:目前有关物理降尘的研究较多,涉及化学除尘的研究尚缺;应用重量法测定植物滞尘量的研究较多,质量浓度法测定城市森林净化空气颗粒物功能的研究较少。在未来一段时间,森林植被化学除尘的过程与机理,城市森林调控空气颗粒物的多方面、系统性研究及相关研究成果的转化与实际应用将会是重要的研究方向。     

甘肃省的胡杨林

胡杨(Populus euphratica)林是荒漠地区特有的珍贵森林资源,甘肃省的荒漠地区也有分布,但最近几十年来由于遭到人们乱砍滥伐和毁林开荒的严重毁坏,如今所剩下的胡杨林已经不多。在所剩下的胡杨林中,不少地段又因为地下水位的下降导致生境恶化,又使得某些胡杨林产生了明显的衰退。这便是当今甘肃省胡杨林面临的严重问题。如果听之任之,让其这样发展下去,甘肃省的胡杨林势必遭到灭绝。为了使甘肃省荒漠中这项珍贵的森林资源免遭灭绝,就必须对它们进行妥善管理,包括严禁乱砍滥伐和毁林开荒,并对那些因地下水位下降而产生了明显衰退的胡杨林进行灌溉和抚育等,与此同时,还应积极进行胡杨的造林,使胡杨林的面积逐渐扩大。     

Distribution of oak forests in Eastern Europe over the last 13000 years

The dynamics and distribution of oak forests on the territory of Eastern Europe over the last 12500 years have been studied. The basic materials used in this study are spore-pollen diagrams converted into the PALAEO database. As a result of this study, a series of maps describing the paleohabitat of oak forests with a 500-year increment has been constructed. Different structures of the paleohabitat of English oak (Quercus robur L.) and the basic forest paleocommunities including this species have been identified and described. The main migration pathways and refugia of oak forests have been determined, including the Volynskaya and Podolskaya uplands, the southern part of the Central Russian and Privolzhskaya uplands, Meshchera, Kodry, and the Mozyrsk-Ovruch-Slovechan refugium.     

Local Mangrove Planting in the Philippines: Are Fisherfolk and Fishpond Owners Effective Restorationists?

Local fisherfolk and fishpond owners have been practicing “restoration” of mangrove forests in some parts of the Philippines for decades, well before governments and non‐government organizations began to promote the activity as a conservation tool. This paper examines ecological characteristics of these mangrove plantations and compares them to natural mangroves in the same areas. Mangrove planters were interviewed and plantation and natural mangrove forests were surveyed to measure forest structure, composition and regeneration. Compared with natural forests, mangrove plantations were characterized by high densities of small stems, shorter and narrower canopies, and fewer species. For both economic and ecological reasons, the vast majority of people dispersed and planted only Rhizophora mucronata/stylosa and, furthermore, they often thinned other species out of planted areas. There was remarkably little subsequent recruitment of other, nonplanted mangrove species into plantations up to 50 and 60 years of age. This pattern held across a diversity of sites, including plantations that had not been selectively cut or weeded. Important ecological and economic benefits result from local mangrove planting, but catalyzing diverse forest regeneration—at least in the short to medium term—is not one of them. The lesson: if you want to restore diverse mangrove forests, you have to plant diverse mangrove forests.     

Does the disturbance hypothesis explain the biomass increase in basin‐wide Amazon forest plot data?

Positive aboveground biomass trends have been reported from old-growth forests across the Amazon basin and hypothesized to reflect a large-scale response to exterior forcing. The result could, however, be an artefact due to a sampling bias induced by the nature of forest growth dynamics. Here, we characterize statistically the disturbance process in Amazon old-growth forests as recorded in 135 forest plots of the RAINFOR network up to 2006, and other independent research programmes, and explore the consequences of sampling artefacts using a data-based stochastic simulator. Over the observed range of annual aboveground biomass losses, standard statistical tests show that the distribution of biomass losses through mortality follow an exponential or near-identical Weibull probability distribution and not a power law as assumed by others. The simulator was parameterized using both an exponential disturbance probability distribution as well as a mixed exponential–power law distribution to account for potential large-scale blowdown events. In both cases, sampling biases turn out to be too small to explain the gains detected by the extended RAINFOR plot network. This result lends further support to the notion that currently observed biomass gains for intact forests across the Amazon are actually occurring over large scales at the current time, presumably as a response to climate change.     

Marine protected areas can be useful but are not a silver bullet for kelp conservation

Kelp forests are among the most valuable ecosystems on Earth, but they are increasingly being degraded and lost due to a range of human-related stressors, leading to recent calls for their improved management and conservation. One of the primary tools to conserve marine species and biodiversity is the establishment of marine protected areas (MPAs). International commitments to protect 30% of the world's ecosystems are gaining momentum, offering a promising avenue to secure kelp forests into the Anthropocene. However, a clear understanding of the efficacy of MPAs for conserving kelp forests in a changing ocean is lacking. In this perspective, we question whether strengthened global protection will create meaningful conservation outcomes for kelp forests. We explore the benefits of MPAs for kelp conservation under a suite of different stressors, focusing on empirical evidence from protected kelp forests. We show that MPAs can be effective against some drivers of kelp loss (e.g., overgrazing, kelp harvesting), particularly when they are maintained in the long-term and enforced as no-take areas. There is also some evidence that MPAs can reduce impacts of climate change through building resilience in multi-stressor situations. However, MPAs also often fail to provide protection against ocean warming, marine heatwaves, coastal darkening, and pollution, which have emerged as dominant drivers of kelp forest loss globally. Although well-enforced MPAs should remain an important tool to protect kelp forests, successful kelp conservation will require implementing an additional suite of management solutions that target these accelerating threats.     

Decline in snail abundance due to soil acidification causes eggshell defects in forest passerines

On poor soils in the Netherlands an increasing number of great tits, Parus major, and of other forest passerines produce eggs with defective shells and have low reproductive success as a result of calcium deficiency. A similar increase in eggshell defects has been observed in Germany and Sweden. Snail shells are the main calcium source for tits in forests where defective eggshells do not occur, but are very little taken in forests where tits often have eggshell defects. We investigated whether a decrease in snail abundance on poor soils could be responsible for the decline in eggshell quality, and if so, what caused this decrease. Snail density in forests where tits have eggshell defects was much lower than in forests where tits do not have such defects. Snail density correlated with the calcium content and to a lesser extent with pH of the litter layer. Liming of a calciumpoor forest soil with few snails resulted in snail densities comparable to those on calcium-rich soils after 4 years. Snail density has declined on calcium-poor soils over the last two decades, but not on calcium-rich soils. Acid deposition has caused a decline of soil calcium on poor soils. We conclude, therefore, that anthropogenic acidification has caused a decline in snail populations, resulting in an increase in eggshell defects in birds in forests on poor soils.     

额济纳绿洲不同林隙胡杨根蘖的发生特征

额济纳绿洲在维持我国西北广大地区脆弱的生态平衡方面起着至关重要的作用.但目前由于水资源匮乏和水污染,以及人为干扰,该绿洲中胡杨林退化严重,更新主要依赖林隙中的根蘖形式的无性繁殖实现.从胡杨根蘖幼苗的发生和生长与林隙的特征关系着手,揭示胡杨根蘖更新的规律.在研究中,调查了胡杨林内不同林隙条件下,胡杨根蘖幼苗的密度、苗高和基径等生长状况,以及林隙内主要的环境影响因子,包括地被物、土壤条件、胡杨母株和人为干扰等.研究结果表明:在胡杨的根蘖幼苗生长过程中,苦豆子与土壤条件是主要的影响因子,苦豆子密度、人为干扰和周边大树数量对根蘖的基径和高生长具有显著的影响,但根蘖的发生的密度与苦豆子和土壤条件等环境因子的相关性却不显著.在分析原因中提出了根蘖发生机制的随机性与环境资源异质性的假说.