Ecological consequences of Douglas fir (Pseudotsuga menziesii) cultivation in Europe

Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was first introduced to Europe from North America more than 150 years ago, was then planted on a large scale and is now the economically most important exotic tree species in European forests. This literature review summarizes the current knowledge on the effects of Douglas fir on soil chemistry, plants, arthropods and fungi. Douglas fir shapes its abiotic environment similarly to native tree species such as Norway spruce, silver fir or European beech. In general, many organisms have been shown to be able to live together with Douglas fir and in some cases even benefit from its presence. Although the number of species of the ground vegetation and that of arthropod communities is similar to those of native conifer species, fungal diversity is reduced by Douglas fir. Special microclimatic conditions in the crown of Douglas fir can lead to reduced arthropod densities during winter with possible negative consequences for birds. The ecological impacts of Douglas fir are in general not as severe as those of other exotic tree species, e.g., Pinus spp. in South Africa and Ailanthus altissima, Prunus serotina and Robinia pseudoacacia in Europe. Nonetheless, Douglas fir can negatively impact single groups of organisms or species and is now regenerating itself naturally in Europe. Although Douglas fir has not been the subject of large-scale outbreaks of pests in Europe so far, the further introduction of exotic organisms associated with Douglas fir in its native range could be more problematic than the introduction of Douglas fir itself.     

Effects on site water balance of conversion from native mixed forest to Douglas-fir plantation in N.W. Patagonia

One of the main concerns of afforestation with exotic fast-growing species is their higher soil water consumption compared with the native vegetation they replace. In this regard, sites downstream of the plantations may suffer temporal or permanent droughts. Under this hypotheses, soil water use of Douglas-fir (Pseudotsuga menziesii) plantations and natural woodlands or shrublands (“ñirantales”) was evaluated in two sites during two growing seasons in El Foyel Valley (Río Negro province), Patagonia Argentina. Two methodological approaches were applied: water balances and sapflow measurements. Douglas-fir forests doubled the leaf area index (LAI) of the native forests (12.6 and 5.1 m² m^?2, respectively). Methodological problems were found while constructing water balances because a non-quantified influx of water to the soil was detected in all systems at the beginning and end of the growing season. This flux was not in correlation with precipitation input demonstrating the geological complexity of the valley. For this reason, caution has to be paid to water balance results. However, we have confidence on sapflow measurements, which indicated, as suggested by the water balances, that there are no differences in transpiration between systems (average of 4.8–3.6 mm day^?1 for the exotic and native forests, respectively) in spite of Douglas-fir plantations having twofold LAI than native ñirantales. However, a different response of transpiration to atmospheric demand was found between the exotic and native species, suggesting differences in their ecophysiological characteristics.     

Management Strategies and Research Orientations of Forest Diseases and Pests in China

Forest diseases and pests are perceived as a growing hazard to China economy. It is a common conclusion that the actualities of forest pests in china are no effective measures to the old important pests, some secondary pests are ascending to chief pests, increasing devastation from exotic pests, frequent ecological pest eruption induced by environmental detriment and host-leading diseases to threaten the "Western Development Project "in China, which is the most important economical strategy to China; that inducement of current forest pests results from ecological function loss and dangerous exoticpest intruding, On the basis of these cognitions, we suggest that strategies of management pests to natural forest would be stressed to maintain its innate capacities to adjust pests in virgin forest and resume such function in intermpted one, that to artificial forest would establish self-control in afforestated stands and develop resistant tree varieties and species, especially those in landscape trees. In re     

Limited native plant regeneration in novel, exotic-dominated forests on Hawai’i

Ecological invasions are a major driver of global environmental change. When invasions are frequent and prolonged, exotic species can become dominant and ultimately create novel ecosystem types. These ecosystems are now widespread globally. Recent evidence from Puerto Rico suggests that exotic-dominated forests can provide suitable regeneration sites for native species and promote native species abundance, but this pattern has been little explored elsewhere. We surveyed 46 sites in Hawai’i to determine whether native species occurred in the understories of exotic-dominated forests. Native trees smaller than 10 cm in diameter were absent in 28 of the 46 sites and rare in the others. Natives were never the dominant understory species; in fact, they accounted for less than 10% of understory basal area at all but six sites, and less than 4% on average. Sites with native species in the understory tended to be on young lava substrate lacking human disturbance, and were mostly located close to intact, native-dominated forest stands. Even where we found some native species, however, most were survivors of past exotic encroachment into native forest, rather than products of active recolonization by native species. In contrast with successional trajectories in Puerto Rico, Hawaii's exotic-dominated forests can emerge, via invasion, without human disturbance and native Hawaiian plants are largely unable to colonize them once they appear. We suggest that a wide diversity of growth strategies among the exotic species on Hawai’i may limit the opportunities for native plants to colonize exotic-dominated forests.     

Ecological consequences of an exotic fungal disease in eastern U.S. hardwood forests

Exotic pests and pathogens can cause extensive mortality of native species resulting in cascading effects within an ecosystem. As ecosystems lose species to exotic enemies, ecosystem function may be disrupted if the ecological roles are not filled by the remaining species. To illustrate this concept, this paper examines the impacts of an exotic fungus (Discula dectructiva) on flowering dogwood (Cornus florida), historically a common understory tree species in eastern U.S. hardwood forests. Recent studies indicate that dogwood plays an important role in the health and ecological integrity of forest ecosystems throughout the eastern U.S. by increasing the availability of calcium in the biota-rich surface horizons of forest soils. However, Discula destructiva causes a disease, dogwood anthracnose, which can rapidly kill dogwood trees. This paper also illustrates how past fire has increased dogwood density and improved tree health in areas infected with anthracnose, suggesting that prescribed fire may offer a tool for land managers to maintain dogwood as a component in eastern U.S. hardwood forests by shifting the “ideal” disturbance regime of this previously fire-intolerant species.     

Population dynamics and management of Amazon tidal floodplain forests: Links to the past, present and future

Although tidal floodplain forests represent the oldest commercial logging frontier in the Amazon, tree demography analyses are lacking. Consequently, the accurate evaluation of impacts of past use and the development of ecologically sound forest management has lagged. To address that gap, we combine matrix model methods with data from interviews with tidal floodplain smallholders regarding land use and ecological knowledge. Here we examine the population dynamics of 8 common tidal floodplain species and explore the link between species population ecology and past, present, and future timber use.Despite the generally high timber stocks due to the dominance of Mora paraensis, these tidal floodplain forests offer challenges to management similar to those seen in tropical forests elsewhere, including low recruitment and species-specific tree growth rates, population densities and size distributions. Furthermore, species population ecology and survey results indicate that the long legacy of forest use in the tidal floodplain forests will influence the future of forest use and management, negatively impacting some species (e.g., Virola surinamensis) while likely benefiting others (e.g., M. paraensis). The observed diameter distributions of species least harvested in the past (e.g., M. paraensis, Licania heteromorpha) follow those derived from stable stage distributions. For other historically harvested species (e.g., Carapa guianensis, V. surinamensis), a larger number of harvest-sized trees for most species would be expected under unlogged conditions, a result corroborated by survey results indicating that maximum log size of long-used timber species has decreased over the past decades.While timber extraction in the Amazon Estuary has endured for centuries, our results suggest long-term timber use does not necessarily entail sustainability; a long history of timber harvesting can also indicate a gradual process of resource depletion as preferred species are sequentially exhausted. If current practices are left unchanged, the prospects for long-term management are likely to decrease further as the densities of preferred high-value species (C. guianensis, V. surinamensis, P. filipes) fall to levels that make management economically unattractive.     

Colonisation of native and exotic conifers by indigenous bark beetles (Coleoptera: Scolytinae) in France

Planting exotic conifers offers indigenous forest insects an opportunity to extend their host range and eventually to become significant pests. Knowing the ecological and evolutionary modalities driving the colonisation of exotic tree species by indigenous insects is thus of primary importance. We compared the bark beetle communities (Coleoptera: Curculionidae, Scolytinae) associated with both native and introduced conifers in France. The aim of our study was to estimate the influence of both host- and insect-related factors on the beetles’ likelihood to shift onto new hosts. We considered the influence of host origin (i.e. native vs. exotic), host tree species identity, tree bark thickness and tree taxonomic proximity, as well as insects’ host specificity. A field inventory using trap trees was carried out in two regions in France (Limousin and Jura) during two consecutive years (2006 and 2007) on three European native conifer species [Norway spruce (Picea abies); Scots pine (Pinus sylvestris) and European Silver-fir (Abies alba)] and five North American [Sitka spruce (Picea sitchensis); Eastern white pine (Pinus strobus); Grand fir (Abies grandis); Douglas fir (Pseudotsuga menziesii) and Western red cedar (Thuja plicata)]. A total of 18 indigenous and 2 exotic bark beetle species were collected. All exotic conifer species were colonised by indigenous bark beetle species and no significant difference was observed of the cumulated species richness of the latter between native and exotic tree species (13 vs. 14, P < 0.05). The ability of indigenous bark beetles to shift onto exotic conifers appeared to strongly depend on host species (significantly structuring bark beetle assemblages), the presence of phylogenetically related native conifer species and that of similar resources, in combination with insect host specificity. Host tree species status (native or exotic) also seemed to be involved, but its effect did not seem as essential as that of the previous factors. These findings are discussed in terms of adaptation, plasticity and practical aspects of forest management.     

Early seedling establishment of two tropical montane cloud forest tree species: The role of native and exotic grasses

Tropical montane cloud forest has been undergoing a drastic reduction because of its widespread conversion to pastures. Once these forests have been cleared exotic grasses are deliberately introduced for forage production. Exotic grass species commonly form monodominant stands and produce more biomass than native grass species, resulting in the inhibition of secondary succession and tree regeneration. The purpose of this study was to assess the effect of native vs. exotic grass species on the early establishment of two native tree seedlings (Mexican alder, Alnus acuminata and Jalapa oak, Quercus xalapensis) on an abandoned farm in central Veracruz, Mexico. Seedling survival and growth were monitored (over 46 weeks) in relation to grass cover and height, and available photosynthetic active radiation (PAR). More seedlings survived in the presence of the native grass Panicum glutinosum than those growing with the exotic grass Cynodon plectostachyus (92% vs. 48%). The causes of seedling mortality varied between species; Q. xalapensis was affected by herbivory by voles but mainly in the exotic grass-dominated stands, whereas A. acuminata seedlings died due to competition with the exotic grass. A. acuminata seedlings increased more in height in the exotic grass-dominated stands (102 ± 7.8 cm) compared to native grass-dominated stands (51 ± 4.7 cm). Grass layer height, cover and available PAR were correlated (Pearson; p < 0.05). In the exotic grass dominated plots, grass layer height was correlated with the relative height growth rates of Q. xalapensis (Pearson; p < 0.05). These results indicate that the exotic grass may be affecting tree regeneration directly (grass competition) and indirectly (higher herbivory). Passive restoration may occur once P. glutinosum dominated pastures are abandoned. However, when C. plectostachyus dominates, introduction of early and mid successional tree seedlings protected against vole damage is needed.     

Evaluation of 15 indigenous and introduced species for reforestation and agroforestry in northeastern Mexico

The coast of the Gulf of Mexico is characterized by dry regions with high variation in climatic conditions. This area is rich in drought-tolerant or subhumid species. The species that are potentially useful for reforestation, regreening, agroforestry activities and the production of timber, fodder, fuelwood and human food have been overexploited, resulting in the gradual decrease and degradation of their populations. This study was undertaken in order to suggest ways of improving the regeneration of these species. Fifteen native and exotic multipurpose tree species of low dry shrubland planted in monoculture in four randomized blocks. Measurements of various growth parameters, volume of trees, fodder potential and agroforestry uses over 15 years were evaluated. Eucalyptus camaldulensis Dehnh., E. microtheca F. Muell., Leucaena leucocephala (Lam.) de Wit. (exotic species), Acacia farnesiana (L.) Wild and Parkinsonia aculeata L. (native species) tend to have better characteristics in terms of growing annual rate, economic value and management schemes, while Prosopis glandulosa Torr. and Helietta parvifolia (Gray) Benth. (native species) did not establish well due to biotics problems which arose under plantation conditions. Acacia rigidula Benth., A. wrightii Benth. and two Pithecellobium spp. (native species) had intermediate yields of great interest since their multipurpose potential is the best of all 15 species. The forage potential of the exotic species (483–1684 kg DM//ha/year) were notably superior to native species (76–721 kg DM/ha/year). The firewood production volume varied between averages of 0.3–1.2 (native species) and 0.4–2.5 m³/ha/year (exotic species). This revised version was published online in June 2006 with corrections to the Cover Date.     

Spores of ectomycorrhizal fungi as inoculants for Nothofagus pumilio and exotic conifer seedlings in Patagonia, Argentina: their activity and conservation

Ectomycorrhizal (EM) fungi incorporation in nursery production is necessary for afforestation with exotic tree species and native forests restoration programs. The fact that spore use as EM inocula is inexpensive and effective, makes it an option more realistic than vegetative inoculum production for many regions around the world. To determine spore activity from EM species selected as inoculants for Nothofagus pumilio and exotic conifers planted in Patagonia, two conservation methods were applied (i.e., dried fruit bodies and spore slurries), and their change over time was assessed (over 8–9 months). Spore activity decreased significantly with time for both native and exotic EM species. Conservation methods showed no significant differences for N. pumilio EM species considered together or for exotic conifer EM species. However, spore activity of different EM species behaved differently with conservation method and over time when considered separately. Taxa which better kept spore activity over time were Austropaxillus statuum and Setchelliogaster fragilis for N. pumilio, and Inocybe kauffmanii for exotic conifers. However, considering together fruit body spore density and spore activity, the species Hallingea purpurea and Cortinarius sp. also appeared as suitable for N. pumilio and Rhizopogon roseolus, R. villosulus, Suillus luteus and S. lakei for exotic conifers. Spore density found in EM fungal fructifications were also established in order to estimate fructification weights necessary to apply a reference dose of active spores in inoculation programs.     

Patterns of exotic plant invasions in Pennsylvania’s Allegheny National Forest using intensive Forest Inventory and Analysis plots

Intensive Forest Inventory and Analysis (FIA) plot data collected in the Allegheny National Forest (ANF), Pennsylvania, between 1999 and 2006 were evaluated for their ability to predict ANF’s vulnerability to invasion by exotic plants. A total of 26 variables classified by biotic, abiotic, or disturbance characteristics were examined. Likelihood of colonization by invasive exotic and non-invasive exotic plants was analyzed using a logistic regression model. Approximately, 11% of the 449 species documented in these plots were exotic, which is higher than has been found in other northeastern forested plots. Only 1% of the ANF flora was invasive exotic plants and these were at low abundance, confirming that most invasions are still at an early stage of establishment. Sites richer in native or non-invasive exotic plants and with more alkaline soils were more likely to be invaded. Younger forests, forests with non-forest patches present, and forests rich in native species were more likely to be colonized by exotic (invasive or non-invasive) plants. Frangula alnus, which is starting to spread locally, differed from the other invasive exotic species in terms of its association with high sapling density to tree density ratios, high soil nitrogen levels, and the presence of fire. Variables representing mortality due to beech bark disease and distance to the nearest exotic planting manifested counterintuitive results. In both cases, the combined occurrence of mortality due to beech bark disease or a close (less than 500 m away) known propagule source and the presence of an invasive or non-invasive exotic plant was rare. We encourage increased use of intensive sampling for FIA in the U.S.A. and similar monitoring programs in other countries, but suggest adding a step to the plot selection phase that would allow forest-wide or regional stratified sampling of typically coarse-scale variables, such as historic or predicted defoliation or fire events, and forest or land type. A more accurate picture of the importance of disturbance variables in defining forest vulnerability to plant invasion may be achieved.     

Collembola communities and soil conditions in forest plantations established in an intensively managed agricultural area

The challenges of a changing climate have directed greater attention to afforestation,but the effects of afforestation on soil fertility and soil biota have not been fully clarified.To explore changes in the soil conditions in two 20-year-old forest plantations established in formerly intensively fertilized plots of agricultural land,we focused on the current developmental state of the sites that received the most fertilizer and evaluated soil properties and Collembola(springtails) communities.Sessile oak(Quercus petraea) and black locust(Robinia pseudoacacia) that had been planted in the afforestation sites were assessed for differences between plantations of native and invasive species.Five adjacent reference associations,including forests and open habitats,were also analyzed and compared.Results showed that the soils in the two afforested sites were similar in their properties and Collembola communities to those of the control cultivated forests,but differed from each other in pH,calcium,phosphorus,and ammonium content.The available potassium and phosphorus contents in the soil of the sessile oak plantation were still high,while the soil organic matter content was adequate(SOM 2.0%) in both plantations.Species richness of Collembola ranged from 18 in the cultivated arable land to 43 in the relict forest.Only a few species typical for forests(e.g.,Neanura muscorum,Isotomiella minor,Entomobrya muscorum) were detected in the young plantations,while species characteristic of open habitats(e.g.,Protaphorura campata,Lepidocyrtus cyaneus) occurred as well.Although more individuals and species of Collembola were present in the soil of young plantations than in arable fields,their community diversities were significantly lower compared to the control forest stands.Collembola community diversity differed significantly also between the two plantation types(with native and non-native tree species).Mean abundance in the afforested sites was about 2.5 times higher than in the cultivated arable land,yet far lower than the mean abundance in the control forests.     

Eucalypt pests and diseases: growing threats to plantation productivity

Plantations of eucalypts (species of Eucalyptus and Corymbia), particularly in the tropics and Southern Hemisphere, have expanded dramatically during the course of the last 100 years. The nature of these plantations has changed substantially as selection, breeding, hybridisation, vegetative propagation and other innovative techniques have been introduced to improve planting stock. Although there are various examples of diseases and pests damaging early plantations, it is clear that separation of the trees from their natural enemies has resulted in exceptional performance. Not surprisingly, both the incidence and impact of diseases and pests in eucalypt plantations has increased over time. This has been due to the accidental introduction of pests and pathogens from areas where the trees are native to new environments. There are also growing examples of host-specific pathogens native to areas where eucalypts have been planted as non-natives, which have undergone sometimes surprising host jumps. These 'new pathogens' threaten not only plantation forestry based on non-natives, but also eucalypts and their relatives in areas where they grow naturally. There is little question that pests and pathogens are set to challenge eucalypt plantation forestry worldwide, more than ever before. In order to sustain profitable businesses based on eucalypt plantations, forestry companies will need to invest substantially in technologies enabling management of these pests and diseases.     

西山区实施"天保"工程浅析

昆明市西山区因其特殊的地理位置 ,丰富的旅游资源和对滇池水域的保护作用被最早列入“天保”工程区。当前西山区存在林龄结构、树种结构不合理 ,生态环境恶化 ,自然灾害频繁 ,三废污染严重 ,耕地后备资源不足等问题。因此在实施天保工程中须要采取以下措施 :①实行分类经营和目标培育 ;②对天然林进行更新和修复 ;③适当引进外来树种 ;④做好防火、防病虫和防污染工作 ;⑤其他管护措施 ;⑥技术保障措施 ;⑦监督管理和监测措施。并进行了效益分析 ,提出了今后建议     

Wood and non-wood forest products of Central Java,Indonesia

We investigated herb and woody species at rehabilitated forests planted by mahogany and teak, and original, not rehabilitated forests in Yogyakarta, Indonesia. Plant species were classified into five use categories: medicine, food, fodder, ornament, and construction. We registered 142 species belonging to 54 families known as useful species with at least one, often more, use categories. The number of useful species was highest for medicine use (107 species). There was a dominance of exotic herb species used for food and annual herbs used for fodder. The number of useful herbs and exotic woody species was highest in teak stands. The number of woody species used for medicine, food, and construction was higher than those for ornament and fodder. All herb species decreased with time, except annual native, that increased. Around 50% of the useful species occurred only once in one site, and some species showed a distribution restricted to one type of stands. Overall, our results seem to show that rehabilitated stands are doing well with regard to useful herb and woody species. We suggest strategies for plant and ecosystem conservation, especially for rare native plant species and species with restricted distribution.     

浙江省湿地松、火炬松引种推广的调查分析

湿地松(Pinus elliottii E.)、火炬松(Pinus taeda L.)原产美国东南部,是美国主要造林树种之一。木材可作建筑、纸浆和纤维工业的原料;湿地松也是一个良好的产脂树种。 浙江省引种湿地松、火炬松已有四十多年的历史。经过早期小面积的试验示范和生产性推广造林两阶段,造林面积已达7000ha.。为了总结这两个树种在本省引种后的适生表现和     

关于中国吉林省林业建设的思考

This paper reviews various forestry practices in Jilin Province, China. The authors emphasize the rich natural diversity of Jilin and the need to focus research efforts on understanding the potential of native species to meet the needs of land-management agencies involved in forest resource exploitation and ecological restoration. The native species of China hold great potential, and deserve more research attention, for meeting these needs. The introduction and testing of exotic species should be dbne only under rigorous scientific testing and after comparison with native species prior to operational introduction into forestry in order to avoid unwanted ecological consequences, including potential problems with alien invasives and pest introductions. The authors also emphasize the need to maintain viable （e.g., genetically diverse and reproductively fit） natural populations of native species in order to protect China＇s valuable natural diversity and maintain the potential of native species to function as future seed sources for local forest and ecological restoration activities.     

Timber investment returns for selected plantations and native forests in South America and the Southern United States

Timber investment returns were estimated for the principal exotic and selected native species in the Southern Cone of Latin America and in the Southern United States. Exotic eucalyptus plantations in South America were most profitable, with internal rates of returns (IRRs) ranging from 13% to 23%, followed by exotic loblolly pine, with IRRs from 9% to 17%. Average loblolly pine plantation returns in the US South were less profitable, with an IRR of about 9.5%, and natural forest management in the South had IRRs of 4% to 8%. Subtropical native species plantations of the best araucaria and nothofagus species had reasonable financial returns, with IRRs ranging from 5% to 13%. Subtropical or tropical native forests had fewer commercial timber species, and had much lower growth rates and returns. Their IRRs were less than 4%, or even negative for unmanaged stands. State subsidy payments for forest plantations or for timber stand improvements increased IRRs somewhat and reserving areas for environmental protection reduced their IRRs slightly. Including land costs in the cash flows decreased these internal rates of return substantially. Natural stand returns in Latin America were much less than those of plantations, but management of those stands offered better rates of return than only holding the land.     

Lack of genetic differentiation after host range extension argues for the generalist nature of <Emphasis Type="Italic">Pityogenes chalcographus</Emphasis> (Curculionidae: Scolytinae)

Context  

The bark beetle, Pityogenes chalcographus, is one of the main pests in Picea abies stands, and it has also been found on other European Pinaceae species. With massive introductions of North American conifer species into European forests, this insect has extended its host range to exotic Pinaceae species.     

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.