Comparison of stand dynamics after dieback caused by pine wilt disease among pine forests with different management regimes in western Japan

In pine forests damaged by pine wilt disease, in western Japan, the effect of protection regimes of pine trees on the stand dynamics were examined in the following four stands: (1) lightly damaged stand (age 30–40 years) with no procedure in operation for protecting pine trees; (2) severely damaged stand (age 30–40 years) with no procedure in place for protecting pine trees; (3) severely damaged stand (age 50 years) with a selective cutting of infected trees; (4) severely damaged stand (age 30–40 years) with a selective cutting of infected trees. All the stands had been abandoned before the pine wilt disease damage. The understory structure of the severely damaged stand with no protection procedure was similar to that of the lightly damaged stand. Frequent invasion by tree species and acceleration in the growth of understory trees occurred after the dieback in the selective cutting stand. These results suggest that a deficiency in the canopy layer caused by the dieback resulted in low disturbance intensity in the early stages after the dieback, but the selective cutting increased the intensity by the reduction in the understory as well as the canopy layer. The intensity of the disturbance in the selective cutting stands was larger in the younger stand because it had a higher density of selectively cut pine trees. The different stand structure of pine forests occurred after the dieback because the intensity of the disturbance varied as a result of the selective cutting operation and the stand age.     

Review of oak stand decline with special reference to the role of drought in Poland

Declines in oak-forest ecosystems have been reported frequently throughout the world since the beginning of this century. They have been associated with the death of individual trees, of small groups of trees or of entire stands. In this paper, the phenomenon of oak decline is presented in the context of the local site conditions in selected countries. Oak decline is regarded as a result of the synergistic action between damaging agents, both biotic and abiotic. Periodic changes of the climate in selected experimental plots of Quercus robur stands in Poland were analysed by comparing Walter's climatic diagrams and annual growth rings. Climatic conditions have a major influence on the vigour of oaks. An increase in the frequency of dry years (especially when drought occurs at the beginning of the growing season, e.g. in May-June) has contributed to the complex phenomenon of oak decline.     

Clear-cutting without additional regeneration treatments can trigger successional setbacks prolonging the expected time to compositional recovery in boreal forests

European Journal of Forest Research - Clear-cutting is one of the most widespread forestry practices used in boreal forests. Clear-cutting of boreal forests in late successional stages could...     

Responses of small mammals to clear-cutting in temperate and boreal forests of Europe: a meta-analysis and review

We analyzed the responses of small mammals to clear-cutting in temperate and boreal forests in Europe. We conducted a meta-analysis of published research on most often studied small mammal species (the striped field mouse, the yellow-necked mouse, the wood mouse, the field vole, the common vole, the bank vole, the Eurasian harvest mouse, the common shrew and the Eurasian pygmy shrew), comparing their abundance on clear-cuts and in unharvested stands. For four other species (the gray-sided vole, the Siberian flying squirrel, the Eurasian red squirrel and the hazel dormouse), we provide a qualitative review of their responses to forest harvest. Results of the meta-analysis suggest that common species of small mammals usually increase in abundance after clear-cutting or are unaffected by this disturbance. As an exception, the yellow-necked mouse declines after clear-cutting in boreal but not in temperate forest. The qualitative review suggests that the responses of more specialized (e.g., arboreal) species to forest harvest are more varied than the responses of generalist species included in the meta-analysis. For some species of small mammals (e.g., the Siberian flying squirrel), habitat loss resulting from forest harvest is a major threat.     

Presettlement and modern disturbance regimes in coast redwood forests: Implications for the conservation of old-growth stands

Coast redwood (Sequoia sempervirens), a western North American conifer of ancient lineage, has a paradoxical combination of late-successional characteristics and strong adaptations to disturbance. Despite its shade tolerance and heavy dominance of the canopy on many sites, redwood saplings are uncommon in upland old-growth stands. Information needed to ensure the conservation of old-growth redwood forests has been limited. In this review paper, we integrate evidence on redwood biology with data on the historic and modern disturbance regimes to help clarify the degree to which key attributes of redwood forests may have been dependent upon periodic disturbance. Available evidence suggests that episodes of fire, flooding, and slope failure prior to European settlement were frequent but predominantly of low to moderate severity and extent, resulting in broadly uneven-aged forests. The majority of fires prior to European settlement were apparently of human origin. Frequency and severity of the major disturbance agents have been radically changed in modern times. Fires have been largely excluded, and flooding has been altered in ways that have often been detrimental to old-growth redwoods on alluvial terraces. However, because of the apparent anthropogenic origin of most presettlement fires, the long-term evolutionary role of fire for coast redwood is ecologically ambiguous. With fire exclusion, redwood possibly could be displaced to some extent on upland sites by increasing abundance of fire-sensitive competitors. Alternatively, redwood may be able to maintain dominance by vegetative sprouting and new seedling establishment on root-wad mounds, fallen logs, and on soil exposed by slope failure. Future research priorities are suggested that will help resolve some of the current ambiguities.     

Influence of several tree traits on rainfall partitioning in temperate and boreal forests: a review

? In forests, rainfall is partitioned into intercepted water (IW), throughfall (TF) and stemflow (SF). We reviewed the majority of published works comparing water flows among tree species in temperate and boreal forests to test the effect of several tree traits on water flows.

? We hypothesized that water flows differed between evergreen and deciduous species, and according to successional status and bark roughness. We also investigated that water flows would be explained by stand variables such as basal area.

? Linear mixed models fitted on reviewed data showed that evergreens had a lower TF than deciduous trees (decrease of 13.9% of total precipitation year-round and 8.4% over the growing period). Similar results were found for conifers compared to broadleaves. TF also declined with the successional status from pioneer to late-successional tree species. SF decreased with bark roughness from smoother to rougher bark. Evergreens had water flows that were dependent on age of the stand, especially for TF which increased by 15.6% of total precipitation from young to adult forests.

? The large scale of TF differences between tree genera together with specific transpiration amounts and rooting features highlighted in other studies should result in significant differences in soil water content among tree species. This may have consequences on stand fitness and growth, and understory vegetation.

     

Climate and historical stand dynamics in the tropical pine forests of northern Thailand

Forest recruitment is the outcome of local- and regional-scale factors such as disturbances and climate. The relative importance of local- and regional-scale factors will determine the spatial scale at which temporal pulses of recruitment occur. In seasonal tropical forests, where the annual dry-season is a critical bottleneck to seedling survival, multi-year periods of relatively cool, wet dry seasons may be required for successful tree recruitment. Consequently, when such conditions are present, region-wide synchronisation of recruitment may occur. To examine the case for regional synchronisation of forest dynamics in the seasonal tropical pine forests of northern Thailand, we investigated forest age structures at three spatial scales: stand, site and region. We compared forest age structures with instrumental climatic records beginning in 1902. We found significant statistical evidence of synchronous recruitment at the stand- and site-scales, but not at the regional-scale. While correlations between recruitment and climate were not statistically significant, recruitment success was often linked to favourable climatic conditions. For example, recruitment at all sites was associated with multi-year periods of cool-wet dry seasons. The lack of significant correlations between recruitment and climate appears to reflect complex interactions among local disturbance history, regional climate variability and pine recruitment.     

Antifertility studies of Colebrookia oppositifolia leaf extract in male rats with special reference to testicular cell population dynamics

Oral feeding of male rats with the ethanolic leaf extract of Colebrookia oppositifolia at dose levels of 100 and 200 mg/kg for 8-10 weeks did not cause body weight loss, while the weights of testes and epididymides were significantly decreased. Seminal vesicles and ventral prostate showed a significant reduction at the higher dose only. Treated animals showed a notable depression of spermatogenesis. Following 100 and 200 mg/kg extract feeding, the preleptotene spermatocytes were decreased by 46.5 and 39.8%, the secondary spermatocytes by 13.4 and 12.7%, the step-19 spermatids by 36.6 and 35.2%, and the mature Leydig cells by 31.2 and 39.5%, respectively. At both dose levels, the seminiferous tubule diameter, Leydig cells nuclear area and cytoplasmic area, as well as the cross-sectional surface area of Sertoli cells, were significantly reduced (P<0.001) when compared to controls. Reduced sperm count and motility resulted in 100% negative fertility at 200 mg/kg dose level. A significant fall in the total protein and sialic acid content and acid phosphatase enzyme activity of the testes, epididymides, seminal vesicle and ventral prostate, as well as in the glycogen content of testes, was also observed at both dose levels in comparison with controls.     

Understory plant communities of boreal mixedwood forests in western Canada: Natural patterns and response to variable-retention harvesting

We examined patterns of variation in richness, diversity, and composition of understory vascular plant communities in mixedwood boreal forests of varying composition (broadleaf, mixedwood, conifer) in Alberta, Canada, before and for 2 years following variable-retention harvesting (clearcut, 20 and 75% dispersed green tree retention, control). Broadleaf-dominated forests differed from mixedwood or conifer-dominated forests in that they had greater canopy cover, litter depth, soil nitrogen, warmer soils, as well as greater shrub cover, herb and shrub richness and diversity (plot scale). In contrast, conifer, and to a lesser extent mixedwood, forest had greater β diversity than broadleaf forest. Overall, mixedwood and conifer forests were similar to one another, both differed from broadleaf forest. Several species were found to be significant indicators of broadleaf forest but most of these also occurred in the other forest types. Understory composition was related to canopy composition and edaphic conditions. Variable-retention harvesting had little effect on understory cover, richness, or diversity but resulted in reduced richness and β diversity at a larger scale. The clearcut and 20% treatments affected composition in all forest types. Early successional species and those common in disturbed sites were indicators of harvesting while evergreen, shade-tolerant understory herbs were indicators of the control forest and 75% retention harvest. We conclude that it is important to maintain a range of variation in canopy composition of mixedwood forests in order to conserve the associated understory communities. The presence of conifers in these forests has a particularly important influence on understory communities. The threshold for a lifeboat effect of variable-retention harvesting is between 20 and 75% retention. Examination of richness and β diversity at a variety of scales can provide interesting information on effects of harvesting on spatial reorganization and homogenization of understory plant communities.     

The dynamics of Imperata: historical overview and current farmer perspectives, with special reference to South Kalimantan, Indonesia

The paper reviews modern attitudes to and uses of imperata grasslands in parts of Southeast Asia, including government and NGO efforts at reforestation. It is argued that the perspective of small farmers has usually been inadequately considered in planning the rehabilitation of Imperata. A historical overview of the impact of changes in land use, population, vegetation dynamics and human adaptation on the creation, disappearance or persistence of Imperata provides a context for the present concerns and emphasizes the wide variability of the situation at the local level. Nine questions are proposed as needing consideration whenever changes are planned to a grassland-based system. They cover three main areas: 1) the origins, past and present uses of the grasslands (including the present land tenure position and variations in uses by ethnic group, socio-economic status and gender); 2) perceptions by farmers of the opportunities and constraints provided by local micro-environments, particularly vegetation types; 3) farmer suggestions for ways of improving their economic status and the potential benefits of agroforestry innovations. These questions are applied to one case study area, the Riam Kiwa valley of South Kalimantan, Indonesia.     

Effects of bioenergy extraction on visual preferences in boreal forests: a review of surveys from Finland,Sweden and Norway

Increased forest biomass production for bioenergy will have various consequences for landscape scenery, depending on both the landscape features present and the character and intensity of the silvicultural and harvesting methods used. We review forest preference research carried out in Finland, Sweden and Norway, and discuss these findings in relation to bioenergy production in boreal forest ecosystems. Some production methods and related operations incur negative reactions among the public, e.g. stump harvesting, dense plantation, soil preparation, road construction, the use of non-native species, and partly also harvest of current non-productive forests. Positive visual effects of bioenergy production tend to be linked to harvesting methods such as tending, thinning, selective logging and residue harvesting that enhance both stand and landscape openness, and visual and physical accessibility. Relatively large differences in findings between studies underline the importance of local contextual knowledge about landscape values and how people use the particular landscape where different forms of bioenergy production will occur. This scientific knowledge may be used to formulate guiding principles for visual management of boreal forest bioenergy landscapes.     

Forest stand dynamics and sudden oak death: Mortality in mixed-evergreen forests dominated by coast live oak

Sudden oak death (SOD), caused by the recently discovered non-native invasive pathogen, Phytophthora ramorum, has already killed tens of thousands of native coast live oak and tanoak trees in California. Little is known of potential short and long term impacts of this novel plant–pathogen interaction on forest structure and composition. Coast live oak (Quercus agrifolia) and bay laurel (Umbellularia californica) form mixed-evergreen forests along the northern California coast. This study measured tree mortality over a gradient of disease in three time periods. Direct measurements of current mortality were taken during 2004, representing a point-in-time estimate of present and ongoing mortality. Past stand conditions, c. 1994, were estimated using a stand reconstruction technique. Future stand conditions, c. 2014, were calculated by assuming that, given a lack of host resistance, live trees showing signs of the disease in 2004 would die. Results indicate that coast live oaks died at a rate of 4.4–5.5% year⁻¹ between 1994 and 2004 in highly impacted sites, compared with a background rate of 0.49% year⁻¹, a ten-fold increase in mortality. From 2004 to 2014, mortality rates in the same sites were 0.8–2.6% year⁻¹. Over the entire period, in highly impacted sites, a 59–70% loss of coast live oak basal area was predicted, and coast live oak decreased from 60% to 40% of total stand basal area, while bay laurel increased from 22% to 37%. Future stand structures will likely have greater proportions of bay laurel relative to coast live oak.     

Chemical structures of p-menthane monoterpenes with special reference to their effect on seed germination and termite mortality

A series of p-menthane monoterpenes was investigated to confirm any correlation between their bioactivity (effect on seed germination and termite mortality) and chemical structure. The germination percentages of Brassica rapa seeds at a concentration of 0.1 mg/Petri dish of (+)-pulegone, isopulegol, piperitone, (?)-dihydrocarveol, terpinen-4-ol and (?)-menthol were found to be 21.6, 27.3, 27.3, 29.1, 42.9 and 43.4, respectively. The lethal concentration 50 values of carvacrol, (+)-pulegone, thymol, (?)-menthol and (?)-terpinen-4-ol for termites (Reticulitermes speratus) were 0.34, 0.50, 0.65, 0.92 and 1.26 (mg/Petri dish), respectively. Of all the compounds tested, phenols produced the highest levels of termite mortality, with ketones and alcohols also showing bioactivity. An assessment of the bioactivity revealed that the presence of a phenol group was effective for termite mortality, with a carbonyl group also showing strong bioactivity. The presence of an alcohol or isopropyl group in a ring also contributed to the bioactivity, whereas the presence of an isopropenyl group at the same position, however, exhibited an inhibitory effect on seed germination. In conclusion, the bioactivity of the p-menthane monoterpenoids was dependent upon the presence and position of certain functional groups and the degree of saturation in the functional group of the side chain.     

Stomatal control and hydraulic conductance, with special reference to tall trees

A better understanding of the mechanistic basis of stomatal control is necessary to understand why modes of stomatal response differ among individual trees, and to improve the theoretical foundation for predictive models and manipulative experiments. Current understanding of the mechanistic basis of stomatal control is reviewed here and discussed in relation to the plant hydraulic system. Analysis focused on: (1) the relative role of hydraulic conductance in the vicinity of the stomatal apparatus versus whole-plant hydraulic conductance; (2) the influence of guard cell inflation characteristics and the mechanical interaction between guard cells and epidermal cells; and (3) the system requirements for moderate versus dramatic reductions in stomatal conductance with increasing evaporation potential. Special consideration was given to the potential effect of changes in hydraulic properties as trees grow taller. Stomatal control of leaf gas exchange is coupled to the entire plant hydraulic system and the basis of this coupling is the interdependence of guard cell water potential and transpiration rate. This hydraulic feedback loop is always present, but its dynamic properties may be altered by growth or cavitation-induced changes in hydraulic conductance, and may vary with genetically related differences in hydraulic conductances. Mechanistic models should include this feedback loop. Plants vary in their ability to control transpiration rate sufficiently to maintain constant leaf water potential. Limited control may be achieved through the hydraulic feedback loop alone, but for tighter control, an additional element linking transpiration rate to guard cell osmotic pressure may be needed.     

Ivy (Hedera helix L.) dynamics in riverine forests: Effects of river regulation and forest disturbance

Ivy (Hedera helix L.) favours moist nutrient-rich substrates of the floodplains of Western Europe. In this study we investigated ivy dynamics in two forest reserves of the upper Rhine. The aim was to determine the influence of flooding on ivy development following the cessation of cuttings at two forest sites of contrasting flooding regimes: the Rhinau Reserve is currently flooded while the Erstein site has not been flooded for 30 years. We also examined the impacts of severe storms in 1993 and 1999 and a long-lasting flood that occurred in 1999.Our results show that the population of Rhinau was smaller and younger because ivy is severely limited by long periods of anoxia, even though it is favoured by regular short-period floods. Indeed, juvenile growth was more rapid at Rhinau where nutrient and moist conditions are more favourable than in Erstein, but mortality was higher because of the long-lasting flood of 1999. At Erstein, the ivy showed a tendency to clump around several big trees, especially oaks and ashes, which may make the host tree vulnerable to windfall. Uprooted or broken ivies were found to survive better than the fallen host tree but could not climb to another trunk highlighting a strong dependence of ivy on its hosting tree.     

辐射松引种栽培综述

辐射松(PinusradiataD.Don)原产于加利弗尼亚海岸,被引种到世界各地,现在是南半球主要的人工林造林树种。1990年以来辐射松被引种到长江上游四川省阿坝州的干旱河谷地区,幼树的成活和早期生长表现良好。本文的主要内容包括:辐射松在原产地和引种地的生长情况,种源和遗传上的差异,环境限制因子和辐射松的气候生境,病虫害,引种不成功的经验教训以及辐射松在生态恢复中的应用。文中还简述了辐射松在阿坝干旱河谷地区的早期生长情况,列举了在长江上游干旱河谷地区引种辐射松可能遇到的问题以及所需开展的研究。图4表5参90。     

Response of vegetation and birds to severe wind disturbance and salvage logging in a southern boreal forest

Vegetation and birds were inventoried on the same plot before and after a severe windstorm in 1999 disturbed a mature black spruce (Picea mariana)–jack pine (Pinus banksiana) forest in northern Minnesota. Following the storm, another plot was established in an adjacent portion of the forest that was salvage-logged. Birds were inventoried on both plots through 2002. The original unsalvaged plot was prescribed-burned in 2004, but vegetation was surveyed through 2003, and through 2005 on the salvaged plot. We examined the effects of wind disturbance by comparing the pre-storm bird and vegetation communities with those developing afterwards through 2002 and 2003, respectively, and the effects of salvage logging by comparing vegetation and the bird community on the unsalvaged plot with those in the salvaged area. Wind reduced the canopy of the forest by over 90% with a temporary increase in the shrub layer, mostly resulting from tip-ups. Several plant species, including jack pine and beaked hazel (Corylus americana), appeared temporarily in the ground layer (<1 m height), but did not persist through 2003. Quaking aspen (Populus tremuloides) root sprouts were abundant in 2001, but decreased dramatically by 2003. Delayed mortality of tipped trees resulted in reduction of the shrub layer to pre-storm levels, and release of advanced regeneration black spruce and balsam fir (Abies balsamea). Bird species using the forest changed from dominance by canopy-foraging species to ground-brush foraging species, with an overall increase in bird diversity. Salvage logging resulted in significant reduction in coarse woody debris, and successful recruitment of jack pine seedlings. Quaking aspen sprouts were nearly 30 times more abundant in the salvage-logged area compared to the unsalvaged control. Ruderal species, especially red raspberry (Rubus ideaus), fringed bindweed (Polygonum cilinode), and several sedges (Carex spp.), were significantly more abundant after salvage logging. The bird community, on the other hand, was greatly diminished by salvage logging, with a reduction in diversity, density, and overall richness of species.     

Forest structure in selected South African forests: edaphoclimatic environment, phase and disturbance

Analysing data from 903 permanent sample plots situated in medium-moist and moist forests in the southern Cape, South Africa, we explored factors controlling forest structure. Pronounced subcanopy stem density persistence (well-stocked subcanopy forest matrix) and stem density packing (comparatively high stem densities of relatively large-sized trees) were found in the moist, less seasonal (quasi-tropical) Tsitsikamma forests. These attributes of structure were linked to the prevailing dystrophic, less seasonal conditions and the associated metabolic vertical growth orientation. The cool, moist and seasonal (quasi-temperate) Knysna forests had lower densities of relatively large-sized trees at the canopy level (stem density intolerance). This was attributed to the lateral growth mode and extended persistence of the trees involved. The warm, seasonal (quasi-subtropical) Outeniqua forests, on relatively nutrient-rich soils, had high stem densities at the canopy level relative to the subcanopy stratum; due to a combination of low subcanopy tree persistence, fast ingrowth of trees into the canopy stratum, which were then lost to mortality before they reached large sizes (high canopy tree turnover). Persistence of the multi-species subcanopy forest matrix supported asynchronous establishment and death of individual trees. Typical for tropical-type forests, the development of trees towards maturity (phase) was associated with a spatially fine-grained disturbance regime. A metabolic performance trade-off model was developed and provided an ecophysiological framework for the interpretation of forest structure and its underlying dynamics. This explanatory model indicated causal links between intraspecific metabolic tactics of trees in response to their edaphoclimatic environment and associated attributes of forest structure. Some implications of the findings for tropical forest management are discussed.