Exotic earthworms of great lakes forests: A search for indicator plant species in maple forests

The invasion of exotic earthworms in previously earthworm-free northern deciduous forests has been linked to the disappearance of forest floor litter, declines in plant species richness, and the development of monotypic stands of Carex pensylvanica. However, the impact of exotic earthworms on the regeneration of trees and understory plants is largely unknown. We examined the relationships between earthworm density, plant species richness, leaf litter accumulation, number of tree (Acer) seedlings, and cover of C. pensylvanica at 14 sites in mesic hardwood forests of the Chequamegon-Nicolet National Forest in northern Wisconsin. Earthworm biomass, especially of the genera Lumbricus, Aporrectodea, and Octolasion was negatively associated with leaf litter mass and number of Acer seedlings. Nine plant species, including two spring ephemerals (Dicentra cucullaria and Osmorhiza claytonii), a sedge (Carex deweyana), and an invasive mint (Galeopsis tetrahit) were negatively correlated with exotic earthworm densities. Dryopteris intermedia and Allium tricoccum, on the other hand, were associated with high earthworm densities. The activities of exotic earthworms appear to have significant impacts on Acer regeneration and the persistence of many herbaceous plants. Our findings suggest that the effects of exotic earthworms on litter mass are strongly related to the observed effects on species composition. Sensitive species can be used as indicators of high and low earthworm densities and might be useful for identifying forests of high conservation value where future invasions of exotic earthworms should be prevented.     

Microbial properties and litter and soil nutrients after two prescribed fires in developing savannas in an upland Missouri Ozark Forest

On some landscapes periodic fire may be necessary to develop and maintain oak-dominated savannas. We studied the effects of two annual prescribed burns to determine their effect on microbial activity and soil and litter nutrients 1 year after the last burn. Surface litter and soil from the upper 0–5 cm soil layer in three developing savannas (oak-hickory, Quercus-Carya), oak-hickory-pine (Quercus-Carya-Pinus), and pine (Pinus) were collected one year after the second of two annual prescribed burns. Surface litter was analyzed for nutrients and soil was analyzed for phospholipid fatty acids (PLFAs) and nutrients. Surface litter chemistry differed across the three savannas for potassium (K) and boron (B), being significantly (P < 0.05) higher for unburned forest than for burned forest. Among savannas, only sulfur (S) was higher for the pine savanna and B for the oak-hickory savanna, both were higher for unburned forest than for burned forest. For soil, calcium (Ca) and B differed across savannas, being higher for burned forest than for unburned forest. Among savannas, soil pH, Ca, and B concentrations were higher in soil from burned forest than from unburned forest. Total PLFA differed among savannas, but was not affected by burning treatments. However, the amounts of biomarkers for Gram-positive and Gram-negative bacteria were higher while the amount of biomarker for fungal PLFA was lower for burned forest than for unburned forest. Our results indicate that the two annual prescribed burns moderately affected PLFA microbial community structure and litter and soil nutrient concentrations. However, the long-term effects of fire on these study sites are not known and merit further study.     

The effects of prescribed burning and canopy openness on establishment of two non-native plant species in a deciduous forest,southeast Ohio,USA

Fire has often been shown to promote invasion by non-native plant species, but few studies have examined the process in temperate-zone deciduous forests. To examine the potential of prescribed fire to facilitate invasions in the Central Hardwoods ecosystem, we experimentally burned small plots and simulated aspects of fire at a forested site in southeastern Ohio, USA. Treatments included high and low burn intensity, lime addition, and litter removal to test hypotheses of population limitation by fire intensity, fire-caused nutrient release, and removal of leaf litter, respectively. Treatments were arranged in a randomized block design in two landscape positions (dry upland, moist lowland) and two canopy conditions (gap, no gap). The experimental sites were not significantly different from randomly chosen forest sites in any of 12 environmental variables. Seeds of two problematic non-native species (Microstegium vimineum and Rosa multiflora) were sown into plots following treatment to test the possibility of seed limitation. We recorded germination and height growth at three dates 1, 4, and 14 months following burning. Germination was promoted by litter removal and high- and low-intensity fire treatments in M. vimineum, and by high-intensity fire in R. multiflora. Seedling growth of both species was greatest following high-intensity fire under canopy gaps. Germination in the second year showed treatment effects similar to the first year indicating persistence of fire effects. Both species showed stronger recruitment in valleys and in canopy gaps, reflecting an interaction of fire and landscape position. We infer that prescribed burning and canopy-opening management practices have the potential to facilitate invasion of the study area by creating conditions promoting establishment and growth of at least two non-native species. The absence of these species in previous studies appears to be due to a lack of propagules rather than the unsuitability of forest sites for germination or growth.     

Forest fire effects in beech dominated mountain forest of Iran

Most of world's forests of different climates have a history of fire, but with different severities. Fire regimes for broadleaf deciduous forests have return intervals that vary from many decades (or less) to centuries (or more). Iran has a total of 1.2 million ha of temperate forest in the north, where fires burn about 300–400 ha annually. This study focused on the impact of fire on forest structure, tree species quality, and regeneration composition (specially beech) in the Chelir forest of northern Iran. The results showed that forest fires changed the structure and had different effects on tree species composition between burned and control areas. Thin barked species such as oriental beech (Fagus orientalis Lipsky) and coliseum maple (Acer cappadocicum Gled.) have been affected more than those with thick bark, like hornbeam (Carpinus betulus L.) and chestnut-leaved oak (Quercus castaneifolia C.A. Mey). The density of oriental beech regeneration in the unburned area was greater than in the burned area, while the quantity of regeneration of hornbeam, coliseum maple and velvet maple (Acer velutinum Boiss) was higher in burned area. Forest fire had a greater effect on oriental beech quality, and changed regeneration composition in the burned area. Fire prevention activities should be considered as a silvicultural treatment for preserving these valuable forests.     

A comparative analysis of spatial, temporal, and ecological characteristics of forest fires in seasonally dry tropical ecosystems in the Western Ghats, India

The Western Ghats in India is one of the 25 global hotspots of biodiversity, and it is the hotspot with the highest human density. This study considers variations in the regional fire regime that are related to vegetation type and past human disturbances in a landscape. Using a combination of remote sensing data and GIS techniques, burnt areas were delineated in three different vegetation types and various metrics of fire size were estimated. Belt transects were enumerated to assess the vegetation characteristics and fire effects in the landscape. Temporal trends suggest increasingly short fire-return intervals in the landscape. In the tropical dry deciduous forest, the mean fire-return interval is 6 years, in the tropical dry thorn forest mean fire-return interval is 10 years, and in the tropical moist deciduous forest mean fire-return interval is 20 years. Tropical dry deciduous forests burned more frequently and had the largest number of fires in any given year as well as the single largest fire (9900 ha). Seventy percent, 56%, and 30% of the tropical moist deciduous forests, tropical dry thorn forests, and tropical dry deciduous forests, respectively have not burned during the 7-year period of study. The model of fire-return interval as a function of distance from park boundary explained 63% of the spatial variation of fire-return interval in the landscape. Forest fires had significant impacts on species diversity and regeneration in the tropical dry deciduous forests. Species diversity declined by 50% and 60% in the moderate and high frequency classes, respectively compared to the low fire frequency class. Sapling density declined by ca. 30% in both moderate and high frequency classes compared to low frequency class. In tropical moist deciduous ecosystems, there were substantial declines in species diversity, tree density, seedling and sapling densities in burned forests compared to the unburned forests. In contrast forest fires in tropical dry thorn forests had a marginal positive effect on ecosystem diversity, structure, and regeneration.     

Forest structure and woody plant species composition after a wildfire in beech forests in the north of Iran

Beech (Fagus orientalis Lipsky) forest covers about 565,000 ha of land in Guilan province, north of Iran and forms a major carbon pool. It is an important economic, soil protection and recreation resource. We studied long-term effects of fire on the structure and composition 37 years after fire occurrence in these forests. To do this research, we selected 85 ha burned and 85 ha unburned beech forests). The results indicated that the fire had not changed the overall uneven-aged structure, but it changed forest composition from pure stands to mixed stands that now include species such as Carpinus betulus, Acer cappadocicum and Alnus subcordata. The density of trees and regeneration was significantly increased, while the density of shrubs significantly decreased. The main reasons for increased tree regeneration were attributed to (1) reduction of litter depth, and (2) increase in available light from opening of the canopy and reduction in shrub competition. It is apparent that the forest is on a path to return to its natural state before the fire after 37 years.     

Bird communities following high-severity fire: Response to single and repeat fires in a mixed-evergreen forest,Oregon, USA

Fire is a widespread natural disturbance agent in most conifer-dominated forests. In light of climate change and the effects of fire exclusion, single and repeated high-severity (stand-replacement) fires have become prominent land management issues. We studied bird communities using point counting in the Klamath-Siskiyou ecoregion of Oregon, USA at various points in time after one or two high-severity fires. Time points included 2 and 3 years after a single fire, 17 and 18 years after a single fire, 2 and 3 years after a repeat fire (15 year interval between fires), and >100 years since stand-replacement fire (mature/old-growth forest). Avian species richness did not differ significantly among habitats. Bird density was highest 17 and 18 years after fire, lowest 2 years after fire, and intermediate in repeat burns and unburned forest. Bird community composition varied significantly with habitat type (A = 0.24, P < 0.0001) with two distinct gradients in species composition relating to tree structure (live to dead) and shrub stature. Using indicator species analysis, repeat burns were characterized by shrub-nesting and ground-foraging bird species while unburned mature forests were characterized by conifer-nesting and foliage-gleaning species. Bird density was not related to snag basal area but was positively related to shrub height. Contrary to expectations, repeated high-severity fire did not reduce species richness, and bird densities were greater in repeat burns than in once-burned habitats. Broad-leaved hardwoods and shrubs appear to play a major role in structuring avian communities in the Klamath-Siskiyou region. In light of these results, extended periods of early seral broadleaf dominance and short-interval high-severity fires may be important to the conservation of avian biodiversity.     

Herbaceous species diversity in relation to fire severity in Zagros oak forests,Iran

Zagros forests are mainly covered byQuercus brantii L. coppices and oak sprout clumps occupy the forest area like patches. We investigated post-fire herbaceous diversity in the first growing season after fire. For this purpose neighboring burned and unburned areas were selected with the same plant species and ecological conditions. The data were collected from areas subjected to different fire severities. Overall 6 treatments were considered with respect to fire severity and the mi-crosites of inside and outside of oak sprout clumps including： unburned inside and outside of sprout clumps （Ni and No）, inside of sprout clumps that burned with high fire severity （H）, inside of sprout clumps that burned with moderate fire severity （M）, outside of sprout clumps that burned with low fire severity （OH and OM）. Different herbaceous com-position was observed in the unburned inside and outside of oak sprout clumps. The species diversity and richness were increased in treatments burned with low and moderate fire severity. However, in treatment burned with high fire severity （H）, herbaceous cover was reduced, even-ness was increased, and richness and diversity were not significantly changed. We concluded that besides the microsites conditions in forest, fire severity is an inseparable part of the ecological effect of fire on her-baceous composition.     

Woodland salamander response to two prescribed fires in the central Appalachians

Using coverboard arrays, we monitored woodland salamanders on the Fernow Experimental Forest in the central Appalachian Mountains, West Virginia, USA prior to and following two prescribed fires in mixed oak (Quercus spp.) forest stands. Treatments were burn plots on upper slopes or lower slopes fenced to prevent white-tailed deer (Odocoileus virginianus) herbivory or control plots that were unfenced and unburned. Most of the 7 species we observed were the mountain dusky salamander (Desmognathus ocropheaus), red-backed salamander (Plethodon cinereus) and slimy salamander (Plethodon glutinosis). Significant population responses were difficult to interpret with numerous treatment and year interactions. Results largely were equivocal. We found no change in woodland salamander assemblage prior to burning or afterwards. There were few differences in adult to juvenile ratios of salamanders among treatments. Still, a priori contrasts of mountain dusky salamanders and red-backed salamander counts corrected for detection probability were greater under coverboards in the 2 years monitored after both prescribed fires had occurred than before burning or in unburned controls. This suggests that these species responded to the reduced leaf litter on the forest floor by utilizing coverboards more. Similarly, the three predominate species of salamanders also were more numerous under coverboards in plots subjected to deer herbivory with less subsequent forest floor vegetation as compared to those burned plots that were fenced. Our observations would suggest that woodland salamanders somewhat are tolerant of two prescribed fires within close temporal proximity. However, because woodland salamanders can be significantly reduced following timber harvest, continued research is needed to fully understand impacts of fire as a pre-harvest management tool in central Appalachian forests.     

Litter production and decomposition dynamics in moist deciduous forests of the Western Ghats in Peninsular India

A field study was conducted in the moist deciduous forests of the Western Ghats (India) to test the following three hypotheses: (1) Litter production in tropical forests is a function of the floristic composition, density, basal area and disturbance intensity; (2) Decay rate constants of tropical species is an inverse function of the initial lignin/nitrogen ratio; (3) Decomposition rates in tropical forests are faster than temperate forests.

Litter fall was estimated by installing 63 litter traps in the moist deciduous forests of Thrissur Forest Division in the Western Ghats at three sites. Litter fall followed a monomodal distribution pattern with a distinct peak during the dry period from November–December to March–April.Dillenia pentagyna, Grewia tiliaefolia, Macrosolen spp.,Xylia xylocarpa, Terminalia spp.,Lagerstroemia lanceolata, Cleistanthus collinus, Bridelia retusa, andHelicteres isora were the principal litter producing species at these sites. The annual litter fall ranged from 12.18 to 14.43 t ha⁻¹. Structural attributes of vegetation such as floristic composition, basal area, density and disturbance intensity did not directly influence litter fall rates.

Leaf litter decay rates for six dominant tree species were assessed following the standard litter bag technique. One hundred and eight litter bags per species containing 20 g samples were installed in the forest floor litter layer at the same three sites selected for the litter fall quantification exercise. The residual litter mass decreased linearly with time for all species. In general, less disturbed sites and species adapted to higher nitrogen availabilities exhibited relatively higher decay rate coefficients (k). The rapid organic matter turnover observed in comparison with published temperate forest litter decay rates confirms that tropical moist deciduous forest species are characterised by faster decomposition rates.

Mean concentrations of N, P and K in the litter were profoundly variable amongst the dominant species. Initial nitrogen content of the leaf litter varied from 0.65 to 1.6%, phosphorus from 0.034 to 0.077% and potassium from 0.25 to 0.62%.C. collinus, an understorey shrub consistently recorded the lowest litter concentrations for all nutrients. The overriding pattern is one of higher nutrient levels in the overstorey leaf litter and lower concentrations in the understorey litter. Furthermore, as decomposition proceeded, the nitrogen concentration of the residual biomass increased.     

Distribution of saproxylic beetles in a recently burnt landscape of the northern boreal forest of Québec

This study evaluated the importance of burned habitat characteristics as well as the likely dispersal from specific habitats in the distribution of saproxylic beetles the same year as a fire occurred, in burned black spruce stands (Picea mariana [Mill] B.S.P.) in the northern boreal forest of Québec. The distribution of early post-fire saproxylic species was mainly driven by burned habitat attributes at the plot scale (0.04 ha), especially fire severity, suggesting that the effect of environment attributes can act at a relatively fine scale. Some xylophagous and most predaceous species were more abundant in severely burned stands whereas fire severity had the opposite effect on several common mycophagous species. The amount of newly fire-killed trees that could be used as breeding substrates in the burned stands had only a weak positive influence on these functional groups. The great majority of early saproxylic species were weakly associated with the distance from unburned forests or other recently burned patches that could act as potential “source habitats”. Indeed, these variables were of lesser importance than the attributes of the burned habitat. Woody debris that were already present in plots before the fire, potentially serving as local of source-populations for early colonizers, had virtually no influence on the local abundance of species. Many saproxylic species, including some true pyrophilous, clearly showed higher abundance as distance from unburned stands increased. This unexpected relation may reflect that dispersal of insects toward the burnt landscape very shortly after fire could be driven by the higher amount of volatiles released by severely burned forests, which are more likely as distance from unburned forest increased.     

Moving riparian management guidelines towards a natural disturbance model: An example using boreal riparian and shoreline forest bird communities

Forest harvesting strategies that approximate natural disturbances have been proposed as a means of maintaining natural species’ diversity and richness in the boreal forests of North America. Natural disturbances impact shoreline forests and upland areas at similar rates. However, shoreline forests are generally protected from harvest through the retention of treed buffer strips. We examined bird community responses to forest management guidelines intended to approximate shoreline forest fires by comparing bird community structure in early (1–4 years) post-burned and harvested boreal riparian habitats and the adjacent shoreline forest. We sampled riparian areas with adjacent: (1) burned merchantable shoreline forest (n = 21), (2) burned non-merchantable shoreline forest (n = 29), (3) 10 m treed buffer with 25% retention in the next 30 m (n = 18), and (4) 30 m treed buffer (n = 21). Only minor differences were detected in riparian species’ abundance and bird community composition between treatments with greater differences in these parameters occurring between post-fire and post-harvest upland bird communities. Indicators of all merchantable treatments were dominated by upland species with open-habitat species and habitat generalists being typical upland indicator species of burned merchantable habitats and forest specialists typical upland indicators of harvested treatments. Riparian species indicative of burned riparian habitats were Common Yellowthroat (Geothlypis trichas), Le Conte’s Sparrow (Ammodramus leconteii) and Eastern Kingbird (Tyrannus tyrannus) and indicators of 30 m buffers were Alder Flycatcher (Empidonax alnorum) and Wilson’s Warbler (Wilsonia pusilla). Multivariate Redundancy Analysis (RDA) of the overall (riparian and upland birds) community showed greater divergence than RDA with only riparian species suggesting less effect of fire and forestry on riparian birds than on upland birds. Higher natural range of variability (NRV) of overall post-fire bird communities compared to post-harvest communities emphasizes that harvesting guidelines currently do not achieve this level of variability. However, lack of a large negative effect on common riparian species in the first 4 years post-disturbance allows for the exploration of alternative shoreline forest management that better incorporates bird community composition of post-fire riparian areas and shoreline forests.     

Grapevine (Vitis spp.) dynamics in association with manual tending,physiography, and host tree associations in temperate deciduous forests

The role of lianas (woody vines) in the development and diversity of both tropical and temperate forests under differing management scenarios has not been thoroughly explored. We examined changes in grapevine (Vitis spp.) densities over time in clearcut stands as influenced by manual tending, physiography, and host tree associations. We used data from long-term studies on 66 clearcut stands dominated by temperate deciduous forest tree species on the Hoosier National Forest in south-central Indiana, USA. Fourteen of the stands had grapevines removed manually, approximately during the stem exclusion stage of development. Grapevine densities steadily increased from age 5 until age 15, which coincides with the period of stem exclusion of these stands. Subsequent grapevine mortality may have been related to light competition. Manually treated stands had similar grapevine densities as untreated stands after 20 years across sites, and it appeared that only on the most xeric area was the grapevine treatment effective in reducing grapevine densities. During early stand development, ranging from ages 5 to 17, grapevine density was strongly related to slope position, but as stands developed through the stem exclusion stage, aspect emerged as a stronger factor influencing grapevine density. Black cherry (Prunus serotina Ehrh.), walnut (Juglans spp.), and elm (Ulmus spp.) were the most common grapevine host trees under both treated and untreated scenarios, which may be associated with the crown architecture of these species. Results suggest lianas play a critical role in the early development of disturbed forest sites in temperate deciduous forests. With concerns that lianas are increasing in abundance and distribution in these forest types, understanding their role in forest dynamics, such as host tree associations at different stages of development, competition dynamics on different sites and corresponding influences on tree growth, species composition, and diversity, will be critical to decision-making processes in achieving desired management goals in the future.     

人类干扰对甘肃麻家寺保护站鸟类群落的影响

2004年11月~2005年1月,在兴隆山麻家寺保护站的6种生境(灌木、阔叶林、混交林、针叶林、农田和人工林)中共记录鸟类25种。鸟类物种总数以灌丛和人工林最高,均为15种。阔叶林最低,为10种。鸟类多样性最高的是灌丛,最低的是阔叶林。各种生境中的鸟类组成和优势物种差异较大,建议每种生境均保持一定面积,以便保护鸟类物种多样性。     

Breeding bird community composition in different successional vegetation in the montane coniferous forests zone of Taiwan

To examine the relationship between forest succession following fire and the composition of bird communities, we investigated the vegetation structure, bird population density, foraging behavior and guild structure in bamboo grasslands (11 years since the last fire), pine savanna (41 years), pine woodland (58 years), old-growth hemlock forest (never burned), and old-growth spruce forest (never burned) in the Tatachia area of central Taiwan. Canopy height, total foliage cover, tree density, total basal area of tree, total basal area of snags, foliage height diversity, and tree species richness all increased with successional age. However, shrub cover peaked in intermediate successional stages. The vertical profile of foliage cover was more diverse in later successional forests, which had more breeding bird species and ecological guilds. All the breeding bird species recorded in early and intermediate stages were also found distributed in the late successional forests. Because Taiwan has high precipitation and humidity, and most forest fires in Taiwan are caused by human activities, forest fires and large areas of early successional vegetation were probably rare in the mountain areas of Taiwan prior to the arrival of humans. Therefore, bird species have not had enough time to adapt to areas with early or intermediate successional vegetation. Moreover, late successional forests host all the major plant species found in the early and intermediate stages and have higher foliage height diversity index, which was positively correlated with the bird species richness and bird species diversity index in this study. As a result, all breeding bird species and guilds in the area can be found in late successional forests. Efforts for conserving avian diversity in Taiwan should focus on protecting the remaining native old-growth forests.     

Characteristics of a 20-year-old evergreen broad-leaved forest restocked by natural regeneration after clearcut-burning

? To elucidate the application of natural regeneration to the restocking of evergreen broad-leaved forests in the subtropics, the characteristics of a 20-year-old evergreen broad-leaved forest restocked by natural regeneration after clearcut-burning were studied in Okinawa, Japan. Within a 0.87 ha clearcut area with four 10 m × 10 m sampling plots, two burned and two unburned ones, the tree composition, tree species diversity and vegetation changes were investigated.

? The results showed that the species diversity, basal area and density of woody stems ? 1.0 m in height differed significantly among phanerophyte types, while they were not significantly different between the burned and unburned treatments. A vegetation census also revealed no obvious differences between the treatments.

? The primary dominant species, Castanopsis sieboldii, continued to dominate the secondary forest with a broad height distribution.

? The structural complexity and high tree species diversity of the regenerating forest after clearcut-burning provides no evidence of degeneration. We can predict that the regeneration forest may gradually develop into stands similar to pre-clearcut primary forest, and that natural regeneration may restore the high tree species diversity of the evergreen broad-leaved forests in Okinawa.

     

Tropical reptiles in pine forests: Assemblage responses to plantations and plantation management by burning

Worldwide, the land area devoted to timber plantations is expanding rapidly, especially in the tropics, where reptile diversity is high. The impacts of plantation forestry and its management on native species are poorly known, but are important, because plantation management goals often include protecting biodiversity. We examined the impact of pine (Pinus caribaea) plantations, and their management by fire, on the abundance and richness of reptiles, a significant proportion of the native biodiversity in tropical northern Australia, by (i) comparing abundance and diversity of reptiles among pine plantations (on land cleared specifically for plantation establishment), and two adjacent native forest types, eucalypt and Melaleuca woodlands, and (ii) comparing reptile abundance and richness in pine forest burnt one year prior to the study to remove understorey vegetation with pine forest burnt two years prior to the study. We also examined the influence of fire on reptile assemblages in native vegetation, by comparing eucalypt woodland burnt two years prior to the study and unburnt for eight years. To quantify mechanisms driving differences in reptile richness and abundance among forest types and management regimes, we measured forest structure, the temperatures used by reptiles (operative temperature) and solar radiation, at replicate sites in all forest types and management regimes. Compared to native forests, pine forests had taller trees, lower shrub cover in the understorey, more and deeper exotic litter (other than pine), and were cooler and shadier. Reptile assemblages in pine forests were as rich as those in native forests, but pine assemblages were composed mainly of species that typically use closed-canopy rainforest and prefer cooler, shadier habitats. Burning did not appear to influence the assemblage structure of reptiles in native forest, but burning under pine was associated with increased skink abundance and species richness. Burned pine was not warmer or sunnier than unburned pine, a common driver of reptile abundance, so the shift in lizard use after burning may have been driven by structural differences in understorey vegetation, especially amounts of non-native litter, which were reduced by burning. Thus, burning for management under pine increased the abundance and richness of lizard assemblages using pine. Pine plantations do not support the snake diversity common to sclerophyllous native forests, but pine may have the potential to complement rainforest lizard diversity if appropriately managed.     

The potential of hinoki (Chamaecyparis obtusa [Sieb. et Zucc.] Endlicher) plantation forests for the restoration of the original plant community in Japan

We estimated the potential of plantation forests for the restoration of the original plant community. We compared the understory vegetation in hinoki (Chamaecyparis obtusa [Sieb. et Zucc.] Endlicher) plantations at the understory re-initiation stage and in adjacent natural forests. To estimate the effect of the original natural forests on the understory species composition of plantation forests, we established study sites in five types of natural forests (mature evergreen broadleaf, mature deciduous broadleaf, mature evergreen coniferous, immature deciduous broadleaf warm-temperate, and immature deciduous broadleaf cool-temperate) and nearby plantation forests. The understory vegetation of the plantation forests had a higher species richness, a higher proportion of early-seral species, and a higher proportion of herb or fern species than the natural forests. The differences between natural and plantation forests varied according to the species composition of the natural forests. The composition of the understory vegetation of the plantations at the understory re-initiation stage was similar to that of the immature deciduous forests. The characteristics of immature, disturbed forests remained in the understory vegetation of the hinoki forests. No great loss of species was observed. Our findings suggest that most of the original forest species still survive in the understory of the plantation forests. These forests have the potential to follow the successional pathway to broadleaf or mixed forests via thinning or clear-cutting without planting.     

Tree effects on the chemical topsoil features of oak, beech and pine forests

We aimed to study tree effects on the chemical properties of forest soils. We compared soil features of three types of forest ecosystems, each with four stands (replicates): beech forests (Fagus sylvatica), oak forests (dominated by Quercus pyrenaica) and pine plantations (Pinus sylvestris). Five samples from the top 10 cm of soil were taken per stand, from which pH, organic matter content (O.M.), total nitrogen (N) and available calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺) and sodium (Na⁺) were determined. Litter layer depth was measured at each soil sampling point. We also measured tree density and crown diameters at each stand. Our results indicated that soil samples from the four pine plantation stands were more similar while oak and beech stands were characterised by great variability in terms of soil properties and leaf litter depth. Although the identity of the dominant tree species significantly influenced several topsoil chemical properties (increase in pH and available cations in oak forests and higher organic matter and total nitrogen in beech and pine ecosystems), there were other important factors affecting soil features that may be taken under consideration. Differences between soil properties of the three types of forest ecosystems were mainly related to the characteristics of the litter layer and less related to the tree layer structure. Finally, the establishment of pine plantations in naturally deciduous tree areas made the topsoil features more homogeneous.     

Oak regeneration using the shelterwood-burn technique: management options and implications for songbird conservation in the southeastern United States

Shelterwood silviculture is commonly used to regenerate oaks in upland stands. However, competition from other species such as tulip-poplar (Liriodendron tulipifera) may deter oak regeneration when these traditional shelterwood techniques are used. The shelterwood-burn technique is a relatively new tool for regenerating oak-dominated stands on some upland sites while simultaneously minimizing undesirable hardwood intrusion with prescribed fire. Once successful oak regeneration has been achieved, three options are available which will result in different vegetative structure and composition within a stand and subsequently different habitats for songbirds. These options are: complete or partial canopy retention, post-harvest prescribed burning and complete canopy removal. Canopy retention, burning and removal treatments will create, respectively, two-age stands that are likely to harbor a diverse mixture of mature forest and early successional species; park-like woodlands with open woodland species; or early-successional habitats with shrubland species. We suggest that shelterwood-burn systems and the management options associated with them offer viable alternatives for managing both songbird and timber resources where oak-dominated stands are the desired goal in upland southeastern sites.