Short-term effects of retention felling at mire sites on boreal spiders and carabid beetles

Green-tree retention is an integral part of forest management in the boreal zone. Retention of small spruce mires, proposed as ‘key habitats’ for many forest organisms, is recommended while logging, but the efficiency of such practices for the maintenance of forest species is poorly understood. Hence, we studied boreal spiders and carabid beetles at 11 retained mire patches (up to 0.55 ha) in Eastern Finland during 1998–2001. The adjacent surrounding drier forests of the focal mires were clear-cut during the winter of 1998/1999. We evaluated the importance of micro-habitat type (retention, edge or clear-cut plot), time since logging, and retention-patch size in determining the assemblages of spiders and carabids. Following logging, species associated with forests and mires generally decreased both in the retained mire patches and in their adjacent clear-cuts. In a GLMM, the number of standing trees in a retention patch – a surrogate for retention-patch size – had no significant effect on most of the tested species, but plot type (retention patch, its edge or clear-cut) was significant for many species. Semi-open-habitat species and open-habitat specialists increased following logging, especially in the clear-cut plots but even within the retention patches. In contrast, mature-forest and moist-habitat specialists became significantly less abundant in clear-cuts than in retention patches following logging. Spider assemblages showed pre-harvest differences among the mires, their edges and adjacent drier forests, but the fauna of logged plots rapidly diverged from that of mire and edge plots. However, after a 1–2 summers time lag, the spider fauna of mires and edges changed toward clear-cuts. For spiders, the post-harvest sample heterogeneity was significantly lower in clear-cuts than in retention patches, including their edges. Carabid responses were generally ambiguous. Multivariate regression trees showed that the number of trees in a forest patch better determined the spider assemblage structure than study area, study year or micro-site type (retention patch, its edge or clear-cut), indicating a strong impact of logging. For carabids, however, the study area better determined the assemblage structure; the other factors were of minor importance. Our results suggest that, as the spider and carabid faunas of the retention patches had drastically changed following logging, (i) retention patches should be considerably larger than the studied size range to efficiently maintain a ‘mire core’ spider and carabid assemblage; (ii) the effect of logging may take years to appear; (iii) spiders were more sensitive to habitat change than carabids; and (iv) harvesting not only changes the relative abundances of forest- and open-habitat associated species but it may also locally decrease the faunal variation.     

Differences in bird species diversities between a natural mixed forest and a coniferous plantation

Bird species diversity and bird species richness were surveyed in a natural mixed forest (mature forest) and in a coniferous plantation (30–40 years old) monthly from 1990 to 1994. These forests were 20 km apart and had similar weather conditions and soil types. There were larch and cedar plantations, and hardwoods along streams in the coniferous plantation. In the natural mixed forest, 55 bird species were found, whereas 40 species were recorded in the coniferous plantation. The species diversity of bird communities was significantly higher in the natural mixed forest than in the coniferous plantation mixed with hardwood trees. This result indicates that the coniferous plantation mixed with hardwood trees, presumed to be a more simplified environment, is likely to be less inhabitable for many bird species than the natural mixed forest, suggesting a relationship between the diversity of the forest environment and the diversity of the bird community. A higher number of bird species was recorded in the small coniferous forest mixed with hardwood trees compared with those in the coniferous plantation. The mixing of broad-leaved trees in a coniferous plantation was suggested to be effective in increasing number of bird species. These tendencies were recorded all through the year during our study. In snow-covering periods, both the diversity and the bird species richness fell in all study sites every year. Snow cover would have greater effect on bird species diversity in the coniferous plantation than in other forest types probably due to diet shortages caused by the snow cover over the forest floor.     

Changes in soil fauna 10 years after forest harvestings: Comparison between clear felling and green-tree retention methods

We studied the responses of soil decomposer animals to clear felling and alternative, green-tree retention harvesting methods (GRT) in Norway spruce forests in Finland. The study plots which were sampled for immediate treatment effects (up to three years) were resampled after 10 years. We hypothesized that responses of decomposers still depends on the level of GTR. The treatments, in addition to untreated controls (100% retained), were: (1) selection felling (70% dispersed tree retention), (2) and (3) gap felling with and without site preparation, respectively (three small gaps were felled in a 1-ha area and 50% of the stand volume was retained), (4) retention felling (10% of the stand volume was retained in three small tree groups) and (5) traditional clear felling (0% retention). Ten years after the treatments the strong increase of enchytraeids immediately after the harvestings was leveled out and the numbers on all treated plots were at the control level. Total numbers or community structure of soil dwelling collembolans were not affected either. The abundance of macroarthropods on the harvested plots, except selection felling, was ca. 50% lower compared to the control forest. Their community structure was also changed due to the harvestings. The most sensitive animal groups were herbivores, microbivores and some detritivores. After 10 years, predators (mainly spiders and certain coleopterans) were decreased only under retention tree groups, while microbidetritivores (dipteran and coleopteran larvae) were unaffected. Our study showed that dispersed tree retention, at least when only 30% of the stand volume was harvested, induced no significant changes in soil decomposer animal community in boreal coniferous forest. On the other hand, decomposer community in clear-felled areas (either large or small) and in small aggregated retention tree groups is still different from that in unfelled forest 10 years after the harvestings. Mesofauna living in the soil organic layer (humus) seem to be better buffered against environmental changes induced by the harvesting compared to animals dwelling close to or on the soil surface. These animals are affected long after harvestings.     

Influence of variable retention harvests on forest ecosystems: Plant and mammal responses up to 8 years post-harvest

Green-tree retention systems are an important management component of variable retention harvests in temperate zone coniferous forests. Residual live trees (“legacy trees”) provide mature forest habitat, increase structural diversity, and provide continuity in the regenerating stand. This study was designed to test the hypotheses that, at up to 8 years after harvest, abundance and species diversity of communities of (i) understory plants and (ii) forest-floor small mammals, and (iii) relative habitat use by mule deer (Odocoileus hemionus), will decline with decreasing levels of tree retention. Communities of plants and forest floor small mammals were sampled in replicated clearcut, single seed-tree, group seed-tree, patch cut, and uncut forest sites in mixed Douglas-fir (Pseudotsuga menziesii)—lodgepole pine (Pinus contorta) forest in southern British Columbia, Canada from 2000 to 2003 (5–8 years post-harvest). Habitat use by mule deer was measured during summer and winter periods each year from 1999 to 2003 in these same sites.     

Threshold effects of variable retention harvesting on understory plant communities in the boreal mixedwood forest

We studied the effects of six levels of dispersed green-tree retention (GTR) harvesting (clearcut (0%), 10%, 20%, 50%, and 75%, and unharvested reference (100%)) on understory plant communities in the 8th growing season post-harvest in the mixedwood boreal forest in northwestern Alberta. For the partial harvest treatments (10%, 20%, 50%, 75%) sample plots were located in the partially harvested (retention) strips as well as in the intervening machine corridors used by the harvesting equipment. The understory plant community was significantly influenced by the gradient of retention level. The cover of understory vegetation, especially graminoids, increased with increasing harvesting intensity for the retention strips and overall considering both plots types. Species richness was unaffected by retention level but did decrease as tree density increased. Lower levels of retention lead to increased abundance of early successional, shade-intolerant species. The results suggest a threshold in understory response to GTR harvesting between the 10% and 20% retention treatments. In terms of understory cover and composition, machine corridors within partially harvested forests resembled clearcuts. The results suggest that retaining more than 10% during GTR harvesting could have significant benefits in terms of maintaining understory plant communities more similar to unharvested reference forest.     

Community and species responses by birds to group retention in a coastal temperate forest on Vancouver Island,British Columbia

Group retention is a forest harvesting technique designed to sustain biodiversity and mitigate concerns regarding clearcut logging. It is characterized by retained forest patches that vary in number, size, spatial arrangement, and habitat attributes. We used birds to compare community composition and species abundance among clearcut, group retention, and uncut control forest treatments, and evaluated species’ responses to percentage retention. The bird community in group retention was more similar to that in control forests than it was to the community in clearcuts. The probability of occurrence for many bird species typical of uncut control forests was related positively to percentage retention. A preliminary analysis of plot-level effects (i.e., amount of forest sampled) suggests that patch size may be more important than total amount of retention.     

Effects of fire disturbance on bird communities and species of mountain Serrano forest in central Argentina

In central Argentina, Serrano forest has a long history of fire disturbance; however, the impact of fire on avifauna remains unknown. We compared the avian–habitat relationships in forest patches with low, moderate, and high fire regimes using a community-level (species richness, abundance, ordination and guilds) and species-level (indicator species analysis) approach. In patches under each fire condition, we recorded bird community composition, richness and abundance, and different vegetation structure variables. The site under high-severity fire regime was structurally poor and had been converted from original forest to dense grassland. There, diversity of bird community was low, retaining approximately 30 % of the species present in the least impacted site. Avian assemblage was dominated by generalist and open area birds. Guilds were underrepresented, showing an important reduction of foliage granivorous, nectarivorous, omnivores, and foliage and bark insectivorous, and absence of fly-catchers. Moreover, low abundance of forest understory, midstory, and canopy species and of birds belonging to open and closed nesting guilds was detected. By contrast, under low and moderate-severity fire regimes highest bird diversity as well as highest representativeness of most guilds was observed. Forest bird species were strongly associated with low fire disturbance, whereas moderate fire disturbance was characterized by the presence of forest and generalist species. Given the critical conservation status of Serrano forest in Córdoba, Argentina, habitat restoration and protection of forest relicts could be suitable measures to promote avifauna preservation.     

Effects of clear-cutting on decomposition processes in leaf litter and the nitrogen and lignin dynamics in a temperate secondary forest

The effects of clear-cutting on the decomposition rate of leaf litter and on nitrogen (N) and lignin dynamics were investigated in a temperate secondary forest. Decomposition processes were examined over an 18-month period by the litterbag method and compared between a clear-cut site and an adjacent uncut control site using leaf litter from five dominant tree species (Clethra barvinervis, Quercus serrata, Camellia japonica, Ilex pedunculosa and Pinus densiflora). The decomposition rate for litter from C. barvinervis, Q. serrata and I. pedunculosa was significantly greater in the clear-cut plot than in the control plot, and there was no significant difference between plots for C. japonica and P. densiflora. Water content of litter was consistently lower in the clear-cut plot than in the control plot. Nitrogen mass increased after 6 months in the control plot, whereas no net increase of N was observed in the clear-cut plot. Nitrogen concentration increased with respect to accumulated mass loss of litter and was consistently lower in the clear-cut plot for all five species. The mass of lignin remaining in decomposing litter was generally lower in the clear-cut plot, but lignin concentration in decomposing litter was not significantly different between the clear-cut and control plots.     

长白山红松阔叶林鸟类群落多样性与稳定性研究

根据连续3 a的样地统计资料,采用物种数、群落密度、Shannon-Wiener多样性指数、Pielou均匀度指数和Simpson优势度指数,分析了长白山红松阔叶林鸟类群落的多样性与稳定性状况。结果表明,在该类型稳定的森林群落中,鸟类群落指数年度周期变化的季节性明显,年间变化较小,均匀度维持较高;物种组成年度间相似性较大,优势种类组成完全相同,群落具有极高的稳定性特点。     

Canopy microclimate response to pattern and density of thinning in a Sierra Nevada forest

Restoring Sierra Nevada mixed-conifer forests after a century of fire suppression has become an important management priority as fuel reduction thinning has been mandated by the Healthy Forests Restoration Act. However, in mechanically thinned stands there is little information on the effects of different patterns and densities of live-tree retention on forest canopy microclimate. This study compared gradients of air temperature and vapor pressure deficit (VPD) through the vertical forest profile among an overstory-thin, an understory-thin, an un-thinned control, and a riparian environment in a Sierra Nevada mixed-conifer forest. Temperature and humidity were recorded for a year by 60 data loggers arrayed in 12 trees at 5, 15, 25, 35, and 45 m above the forest floor. Both thinning treatments had significantly more extreme summer daily ranges of temperature and VPD than the control across heights. The overstory-thin resulted in the greatest maximum temperatures, VPDs, and VPD range among all sensors at 5 m, and significantly higher summer maximum temperatures and VPDs than the control in lower strata (≤15 m). The understory-thin also had significantly higher summer maximum temperatures than the control (≤15 m), but these too were significantly less than in the overstory-thin nearest the surface at 5 m. Understory thinning did not alter the mean or range of microclimate as much as overstory thinning. Riparian microclimate had significantly lower minimums and means, and greater daily ranges of temperatures and VPDs than the control. Results suggest that thinning canopy cover significantly increases the extremes and variability of understory microclimate compared to thinning from below and no-thin treatments.     

深圳市常见园林植物滞尘效应初步研究

采用蒸干称重法和显微观察法对深圳市28种常见园林绿化植物的滞尘能力及部分植物的滞尘方式进行了初步研究。单位叶面积滞尘量的测定结果表明,针状叶类乔木中:龙柏﹥木麻黄;阔叶类乔木中:麻楝>霸王棕>黄花夹竹桃>海枣>大花紫薇>长芒杜英>椰子>紫檀;灌木类中:紫薇>金叶榕=小蜡树>黄花马缨丹>锈鳞木犀榄>红花檵木>龙船花>散尾葵>紫雪茄花>大佛肚竹>四季桂>朱槿>棕竹>软叶刺葵>朱蕉;草本类中:中国文殊兰>花叶艳山姜>蔓花生。以显微观察比较叶片滞尘能力有显著差异的种类,紫薇、金叶榕、红花檵木和朱蕉的滞尘方式分别以颗粒物堆叠式、块状层结式、颗粒镶嵌式及零星嵌入式为主。研究筛选出的常见园林绿化植物中滞尘能力强的种类,可为相似大气环境的亚热带城市绿化提供优先选择,使其成为有效改善空气质量的生物基本元素。     

Effects of different forest practices on Pinus tabulaeformis population dynamics and species diversity in the Huanglongshan forest region

Three Pinus tabulaeformis populations which experienced tending, shelterwood cutting, and closed tending were separately investigated to study the effects of these three forest practices on the age structures, static life tables, survivorship curves, and species diversities of P. tabulaeformis populations in Huanglongshan Mountain. Time sequence model was adopted to predict the dynamic population numbers of different P. tabulaeformis populations with different forest practices. The results revealed that the three populations are essentially identical in population structure, their young and old individuals make up a small proportion and their mid-aged individuals make up a large proportion and consequentially P. tabulaeformis populations generally stand stable. In the P. tabulaeformis communities with three tending practices, the highest species abundance index appears with tending and shelterwood cutting and the highest evenness index and species diversity appears with closed tending. The P. tabulaeformis populations with tending and shelterwood cutting practices belong to one developmental type and the P. tabulaeformis populations with closed tending practices belong to a stable type. It indicated that in the future, closed tending as the major practice and tending and shelterwood cutting as the supporting practices should be applied for P. tabulaeformis populations in Huanglongshan Mountain so that the communities will develop continuously. __________ Translated from Acta Botanica Boreali-Occidentalia Sinica, 2006, 26(5): 1,007–1,013 [译自: 西北植物学报]     

Effects of slash retention and wood ash addition on fine root biomass and production and fungal mycelium in a Norway spruce stand in SW Sweden

In the study reported here we examined the short-term effects (1–3 years) of slash retention (SR) and the long-term effects (13–15 years) of wood-ash application (A) on fine roots and mycorrhizae in a 40-year-old Norway spruce forest in southwest Sweden. Soil cores were used to obtain estimates of the biomass (g m⁻²) of roots in three diameter classes (<0.5, 0.5–1 and 1–2 mm), root length density (RLD), specific root length (SRL) and mycorrhizal root tip density (RTD). Fine root (<1 mm) length production and mortality, and mycelium production, were estimated using minirhizotron and mesh bag techniques, respectively. Compared with the control plots (C), the biomass of fine roots in diameter classes <0.5 mm and 0.5–1 mm was significantly higher in A plots, but lower in SR plots. In addition, RLD was significantly lower in the humus layer of SR plots than in the humus layers of C and A plots, but not in the other layers. None of the treatments affected the SRL. In all soil layers, the SR treatment resulted in significant reductions in the number of ectomycorrhizal root tips, and the mycelia production of fungi in mesh bags, relative to the C treatment, but the C and A treatments induced no significant changes in these variables. Fine root length production in the C, A and SR plots amounted to 94, 87 and 70 mm tube⁻¹ during the 2003 growing season, respectively. Fine root mortality in treated plots did not change over the course of the study. We suggest that leaving logging residues on fertile sites may result in nitrogen mineralisation, which may in turn induce reductions in root biomass, and both root and mycelium production, and consequently affect nutrient uptake and the accumulation of organic carbon in soil derived from roots and mycorrhizae.     

Characteristics of bird communities between slope and valley in natural deciduous forest, South Korea

本研究在弄清韩国桂坊山(374030N,128301E)天然落叶阔叶林斜坡和山谷中鸟类群落间的特征差异。调查结果表明:两地鸟类群落的种类组成、丰富度、鸟种多样性及群落结构都有不同。森林的垂直结构特别是林下覆被度及胸高直径分布多显不同。两地生境结构的不同必然影响着鸟类对可利用生境的选择。表6图2参19。     

Effects of forest landscape change and management on the range expansion of forest bird species in the Mediterranean region

In the western Mediterranean region of Catalonia (NE Spain), during the last 20 years of the 20th century, the range of many forest bird species has expanded. Our objective was to characterize the roles of (a) spatial population processes (related to dispersal), (b) changes in forest structure (due to forest maturation and management), and (c) landscape composition (resulting from afforestation and fires) in the range expansion of these bird species at the landscape scale (10 × 10 km). After correcting for the differences in sampling effort, colonizations appeared to be more likely near areas in which the species had been present in the 1980s. Patterns of the range expansion were also strongly associated with forest maturation, which seems to affect the spatial arrangement of birds at multiple scales. Changes in forest landscape composition due to afforestation and fires were minor determinants of range changes, and forest management did not seem to prevent range expansion at the spatial scale studied. Colonization events appeared to be driven primarily by landscape changes occurring in nearby localities rather than within the colonized locations themselves, presumably because of source–sink dynamics and connectivity patterns. Our results showed that in Catalonia, at a landscape scale, the impact of forest management on forest bird communities is much smaller than the impact of the widespread maturation of forests following a large-scale decline in traditional uses.     

Planning timber harvest of residual forest stands without compromising bird and small mammal communities in boreal landscapes

Numerous efforts have been invested in designing and configuring residual forest stands in Canadian boreal forest to preserve their overall biodiversity. Now that several landscapes have been partially logged, the next issue in forest management involves the planning of residual forest stand harvesting without compromising wildlife populations. Residual stands can be cut when adjacent regeneration reaches 3 m in height according to current regulations in several Canadian provinces (e.g., Québec, Ontario, Alberta, and British-Columbia). However, little is known on whether such regenerating habitat (RE-3m) can maintain wildlife communities similar to those found in unharvested mature forest (CO). We estimated the relative abundance of small mammals and forest birds in RE-3m and CO habitats and characterized landscape and stand structures. These variables were then compared between the two contrasting successional stages and were used to build habitat use models (HUMs) for 21 species. CO and RE-3m differed with regard to several landscape characteristics and stand structure variables as a result of logging. Snowshoe Hare, Northern Flicker, Alder Flycatcher, Ruby-crowned Kinglet, White-throated Sparrow and Magnolia Warbler were more abundant in RE-3m than CO, while Red-backed Vole, Brown Creeper and Golden-crowned Kinglet exhibited lower abundances in RE-3m. No significant differences in abundance were observed for the 12 other species. Species HUMs were highly significant and explained between 64.3 and 99.1% of the total variability in abundance. Following variance partitioning, stand structure variables accounted for most of the explained variability (54.2%) while landscape characteristics accounted for only 28.7%. No difference in species richness was observed but community evenness was greater in CO than RE-3m. Our results suggest that current regulations may threaten the maintenance of 3 out of 21 censused species for which abundances were significantly lower in regenerating 3 m tall stands. As stand structure explained a large amount of variability in abundance, it should be considered during timber harvest planning in both mature and regenerating stands. Until we know more on whether the current regulations are suitable for maintaining overall biodiversity, our results suggest that some mature forest stands should be maintained within managed landscapes for a complete logging rotation period.     

孟家岗红松母树林疏伐密度效应分析

对黑龙江省孟家岗林场40年生红松母树林300、450、600、700和1 300株/hm2(对照)疏伐处理后14个性状的进行统计分析,结果表明,疏伐处理对14个性状均产生极显著影响.除枝下高外,其余性状均值均有较大程度的提高,其中单株结实质量、树冠体积和公顷结实质量分别提高了47.79％、33.6％和28.65％.此外,不同性状之间存在极为复杂的相关性.聚类分析和主分量分析将上述性状分成3大类,分别代表了树冠、种子品质和结实性状.这3类性状在各主成分上得分值的加权和比较分析表明,孟家岗林场42年生红松母树林疏伐抚育最佳密度是450株/hm2.     

不同施钾水平对油茶树体生长和林地养分含量的影响

为了确定油茶幼林钾肥最适施用量,从而为油茶的科学施肥提供理论依据,以‘赣无’系列的5年生油茶林分为试验对象,设置了5个钾素水平处理(K0、K1、K2、K3、K4),1个施用复合肥的对照处理(CKFHF)和1个不施肥的处理对照(CK0),就不同施肥处理对油茶树体生长、叶片养分积累和土壤养分含量的影响情况进行了试验、测定与分析。结果表明:施肥均能显著提高油茶树体各生长指标的增幅和叶片及土壤中各种养分的含量;随着施钾水平的提高,油茶树体各生长指标的增幅和叶片中各种养分的含量均随之增加,K3处理的达到最大值,复合肥处理的肥效小于K2处理;随着施钾水平的提高,油茶林地土壤中速效钾和有机质的含量均显著性增加,而土壤中碱解氮和有效磷的含量则随着施钾水平的提高均先减小后增加,K4处理的降到最小值;对油茶叶片中的钾含量、土壤中的速效钾含量与施钾量进行拟合,得出其响应曲线,并确定了对油茶幼树施用钾肥的最适用量范围为317.72~322.25 g/株。     

Patterns of forest use and endemism in resident bird communities of north-central Michoacán, Mexico

We compared breeding avian communities among 11 habitat types in north-central Michoacán, Mexico, to determine patterns of forest use by endemic and nonendemic resident species. Point counts of birds and vegetation measurements were conducted at 124 sampling localities from May through July, in 1994 and 1995. Six native forest types sampled were pine, pine–oak, oak–pine, oak, fir, and cloud forests; three habitat types were plantations of Eucalyptus, pine, and mixed species; and the remaining two habitats were shrublands and pastures. Pastures had lower bird-species richness and abundance than pine, oak–pine, and mixed-species plantations. Pine forests had greater bird abundance and species richness than oak forests and shrublands. Species richness and abundance of endemics were greatest in fir forests, followed by cloud forests. Bird abundance and richness significantly increased with greater tree-layer complexity, although sites with intermediate tree complexity also supported high abundances. When detrended correspondence-analysis scores were plotted for each site, bird species composition did not differ substantially among the four native oak-and-pine forest types, but cloud and fir forests, Eucalyptus plantations, and mixed-species plantations formed relatively distinct groups. Plantations supported a mixture of species found in native forests, shrublands, and pastures. Pastures and shrublands shared many species in common, varied greatly among sites in bird-species composition, and contained more species specific to these habitats than did forest types.