Variation in post-wildfire regeneration of boreal mixedwood forests: underlying factors and implications for natural disturbance-based management

To test the direct regeneration hypothesis and support natural disturbance-based forest management we characterized the structure and composition of boreal mixedwood forests regenerating after large wildfires and examined the influence of pre-fire stand composition and post-fire competing vegetation. In stands which had been deciduous (Populus sp.)-dominated, conifer (white spruce)-dominated, or mixed pre-fire we measured regeneration stocking (presence in 10 m² plots), density and height 10–20 years post-burn in five wildfires in Alberta, Canada. Most plots regenerated to the deciduous or mixed stocking types; plots in the older fire and in stands that were pure conifer pre-fire had higher amounts of conifer regeneration. Surprisingly, regeneration in pre-fire ‘pure’ white spruce stands was most often to pine, although these had not been recorded in the pre-fire inventory. Pre-fire deciduous stands were the most resilient in that poplar species dominated their post-fire regeneration in terms of stocking, density and height. These stands also had the highest diversity of regenerating tree species and the most unstocked plots. High grass cover negatively affected regeneration density of both deciduous and conifer trees. Our results demonstrate the natural occurrence of regeneration gaps, pre- to post-fire changes in forest composition, and high variation in post-fire regeneration composition. These should be taken into consideration when developing goals for post-harvest regeneration mimicking natural disturbance.     

Potential use of pine plantations to restore native forests in a highly fragmented river basin

? In forests, the substitution of broadleaf species by conifers can reduce biodiversity because coniferous forests generally provide less diverse vascular understories than broadleaf forests. However, in some cases, former pine plantations might be useful for restoring native forests. We compared plant species composition on the plot scale in natural beech and mixed oak forests with that in plantations of Pinus radiata. Links between plant diversity and landscape parameters (patch size, fractal dimension and distance to the nearest patch of the same type) were investigated.

? The objective of this study was to evaluate the use of pine plantations for restoring native diversity in a zone where native forests are very fragmented.

? Similar to oak forests, plant diversity in pine plantations was high, mainly due to the presence of generalist species. Some species characteristic of oak forests also appeared in pine plantations, suggesting the onset of natural forest regeneration.

? These results suggest that pine plantations could be used to promote natural regeneration of original oak forests. Moreover, residual native stands should be conserved as important sources of native species and their seeds.

     

Post-harvest Regeneration of Lowland Black Spruce Forests in Northeastern Ontario

Success of natural regeneration has been a concern since the introduction of heavy machinery in harvesting. The objective was to compare the effect of three operational harvest methods careful logging around advanced growth (CLAAG), group seed tree (GST), and group seed tree followed by shearblading site preparation (SHE) on natural regeneration in the Clay Belt region of Ontario. A total of 30 stands, 562 cluster sample plots, were surveyed. Total density of black spruce regeneration did not differ, but height structure of black spruce regeneration did among harvest methods. The CLAAG method resulted in highest total regeneration density of other conifers. Decreasing density of other conifers from the CLAAG to GST to SHE sites indicated that the CLAAG method protected advance regeneration as expected and the SHE method removed advance regeneration in the path of the shearing blade. Both black spruce and other conifer regeneration densities increased with increasing time since harvest. Stocking of black spruce, all conifers, or all tree species did not differ significantly among harvest methods, nor did it change with time since harvest. Stocking was nonlinearly related to regeneration density. Models developed in this study predict that full stocking (i.e., 60%) can be reached based on regeneration density of 5000 stems per ha regardless of crop species choice preference. However, the existing stocking criterion for assessing black spruce regeneration may be problematic.     

Evaluation of mature conifer plantations as secondary habitat for epigeic forest arthropods (Coleoptera: Carabidae; Araneae)

Spiders (Araneae) and ground beetles (Coleoptera, Carabidae) were studied in a woodland of the Northwest German lowland. An ancient oak–beech stand (170 years old) growing on mineral soil as well as a 110-year-old Scots pine (Pinus sylvestris) and a 55-year-old spruce (Picea spp.) forest growing on peat were investigated by pitfall trapping. A total of 155 species (39 carabids, 116 spiders) and 16,887 individuals (5269 carabids, 11,618 spiders) was recorded. Beetle diversity was high in the oak–beech stand and the spruce forest, but significantly lower in the pine forest. In both conifer plantations the activity density of carabids was considerably lower. Spider diversity was significantly higher in the spruce forest when compared to the beech and pine stand, respectively. Analyses of assemblage similarity distinguished clearly the fauna of all three stands. For each forest type, indicator species were detected. Although both conifer plantations were planted on former bogs, spider species typical of bogs were present only in the pine stand, not in the spruce stand. In both animal taxa, species typical of deciduous forests were more numerous and abundant in the oak–beech stand when compared to the conifer plantations. Although they were in direct contact, the conifer stands on peat only to a very low extent serve as secondary habitats for the epigeic fauna of the autochthonous deciduous woodland. During the 1990s, various agricultural programmes in Central Europe promoted such conifer plantations – in contrast, such afforestation measures on extensively used or fallow land of former bogs are not supported by the results of this study.     

Young conifer stands form a deer browsing refuge for an oak admixture: silvicultural implications for forest regeneration under herbivore pressure

There is little knowledge how ungulate pressure on forest regeneration may be mitigated by silvicultural methods. The knowledge is especially needed for artificially regenerated, deciduous tree species. We studied factors affecting browsing incidence by deer in the Pisz Forest District in Poland, an area where 10,000 ha of forest was damaged by a 2002 hurricane. In 2006, we established three experimental plots (in total, 22.6 ha), in which the main species was Scots pine (Pinus sylvestris) admixed with pedunculate oak (Quercus robur). The data on browsing were collected in 2008–2015. In general, oak browsing incidence was unrelated to oak planting density. On a plantation scale, it was significantly affected by the pine age. Although in each variant all the oaks were browsed for four consecutive years (2009–2012), in 2013 browsing incidence began to decrease. When the pines grew higher and formed a physical barrier, it was harder for deer—roe deer (Capreolus capreolus), red deer (Cervus elaphus) and moose (Alces alces)—to move through and locate the oaks. Moreover, within plantations, oak browsing incidence was higher in the patches with shorter pines. Browsing of individual saplings or small groups of saplings was also negatively affected by the height of neighbouring pine saplings. Oak density influenced deer selectivity depending on the tree height. In a low oak tree density, browsing incidence was unrelated to oak height, while in higher tree density, deer selected oaks of the height between 40 and 100 cm. We postulate that deciduous admixture in a coniferous (unattractive) stand can be planted with a few year delay. Older coniferous trees should impede locating of attractive tree species by deer and the browsing incidence.     

Stand Density Control Diagrams for Scots pine and Austrian black pine plantations in Bulgaria

Stand Density Control Diagram (SDCD) is a stand-level mathematical model, which describes the relationships between yield, density and mortality throughout all stages of stand development. The SDCD is primarily used to derive density control schedules by management objectives. The main objectives of the present study are to define a modified model of SDCD for application to Scots pine (Pinus sylvestris L.) and Austrian black pine (Pinus nigra Arn.) plantations in Bulgaria, to examine the fitness of the model with representative experimental data sets from plantations of both species and to present a way of direct application of the SDCDs for practical purposes. The constructed SDCDs characterize the spatial-temporal dynamics of the pine plantations in a broad range of densities, forest sites and growth stages from 4 to 26 (28) m of dominant height class. The full density lines were fixed with self-thinning exponents α = 1.69 and α = 1.75 for Scots pine and Austrian black pine, respectively, and the trajectories of natural thinning for 23 initial densities (444-40000/ha) were determined. A direct way for application of the SDCDs to the plantation management was designed to estimate the optimal initial densities for the maximum attainable final yield and large-size wood production by self-thinning stands.     

应用抚育间伐资料确定经济成熟龄的初步研究

为了克服森林经济成熟龄研究中固定标准地数量少,设置年限短、资料相对贫乏和基础数据可靠性较低等缺点,本文采用来源丰富、数据可靠的间伐(或主伐)作业标准地调查表为原材料,以动态分析评价经济活动的净现值(NPV)为指标,从径级分布这个最基本的数据算起,对隆化县茅荆坝林场阴坡厚土人工油松林进行了分析,力图精确,动态地反映林地的径级分布、材种(类)出材量、价格等随年龄的变化,以确定适宜的经济成熟龄。结果表明,茅荆坝阴坡厚土人工油松林的净现值最大的年龄是27a,即为其经济成熟龄。     

Habitat use of large ungulates in northeastern Germany in relation to forest management

Estimating large herbivore density has been a major area of research in recent decades. Previous studies monitoring ungulate density, however, focused mostly on determining animal abundance, and did not interpret animal distribution in relation to habitat parameters. We surveyed large ungulates in the Biodiversity Exploratory Schorfheide-Chorin using faecal pellet group counts. This allowed us to explore the link between relative ungulate abundance, habitat use, and browsing damage on trees in a region with several types of forest, including unharvested and age-class beech forests, as well as age-class pine forests. Our results demonstrate that roe deer and fallow deer relative abundance is negatively correlated with large tree cover, and positively correlated with the cover of small shrubs (Rubus spec., Vaccinium spec.), and winter food supply. Habitat use of roe deer and fallow deer, as estimated by counting faecal pellet groups, revealed a preference for mature pine forests, and avoidance of deciduous forests. This differential habitat use is explained by different distributions of high quality food resources during winter. The response of deer to understory cover differed between roe deer and fallow deer at high cover percentages. The amount of browsing damage we observed on coniferous trees was not consistent with the relative deer abundance. Browsing damage was consistently higher on most deciduous trees, except for beech saplings which sustained less damage when roe deer density was low. Because roe deer is a highly selective feeder, it was reported to affect tree diversity by feeding only on trees with high nutritional value. Consequently, we propose that managing the number of all deer species by hunting is necessary to allow successful forest regeneration. Such an adjustment to deer numbers would need to account for both current tree diversity and alternative food resources. Our findings may be applicable to other forest landscapes in northeastern Germany including mature pine stands and differently harvested deciduous forests.     

河北燕山东段低山丘陵绿化研究

本文是根据三年的调查研究(共调查了约1000块标准地)和造试验林所取得的材料写成的。研究了油松林、栎林、刺槐林、灌丛和杨树林等的更新、造林以及经营方面的技术和营林体系问题。提出了在不能修筑窄带梯田发展干鲜果树的地段,提高森林覆盖率和林地生产力的育林措施。在林种搭配和营林体系选择方面,应因地制宜地采用封山育松栎林,营造刺槐薪炭林和小径材用材林,进行栎类播种造林和封养灌木林等。这是适应低山丘陵生态条件、经济有效的恢复森林植被的综合措施。     

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.     

Structure and regeneration dynamics of dominant tree species along altitudinal gradient in a dry valley slopes of the Bhutan Himalaya

The aim of our study was to characterize the structure and regeneration dynamics of dominant tree species along altitudinal gradient in dry valley slopes of the Bhutan Himalaya. In the typical dry valley slopes of west-central Bhutan, we analyzed forest stratification, tree crown projection, and population structure from lower dry valley bottom (1520 m a.s.l.) to upper humid ridge top (3370 m a.s.l.) across five major forest types: i.e. (1) dry pine forest with Pinus roxburghii as a dominant species; (2) mixed broad-leaved forest with Quercus lanata (evergreen), Quercus griffithii, (deciduous), and Rhododendron arboreum (evergreen) as major canopy species; (3) evergreen broad-leaved forest dominated by Quercus semecarpifolia, Quercus glauca and Quercus oxyodon; (4) cool conifer forest dominated by Abies densa and Tsuga dumosa; (5) cold conifer forest with A. densa and Juniperus recurva as dominants. In general, regeneration pattern of major dominant species shifted from inverse-J (lower altitudes), to sporadic (mid-altitudes), and to uni-modal type (upper altitudes) corresponding to three regeneration trends: (1) invasive at the lower, warm, dry forest under relatively strong human disturbances; (2) stable/balanced at the mid-altitude, in a relatively stable, mature moist evergreen broad-leaved forest with gap regeneration; and (3) poor/low regeneration at the upper, cool, humid conifer forest with a continuously cattle-grazed understory. Overall, regeneration patterns were balanced in all forest types, however care should be taken to prevent excessive exploitation of dry pine forest of lower valley bottom, and to control cattle grazing at higher altitudes. Our findings can be incorporated into management plans for sustainable management and conservation of mountain forests.     

Stem deformation in young plantations of black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) in the boreal forest of Quebec,Canada

Stem deformation has often been observed in young black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) plantations. Whenever important stem deformations are observed at the time of harvesting, timber value is negatively affected especially during the wood transformation process. The present work was undertaken to quantify and qualify the importance of stem deformation of black spruce and jack pine in the boreal forest of central Quebec at the stand and tree levels. In 30 black spruce and jack pine plantations, approximately 22% of spruce trees and 27% of pine trees exhibited stem deformation. The proportion of deformed trees was higher in the youngest plantations and decreased with the age of the plantations. Stem deformation caused the formation of compression wood which is another factor that can reduce the value of wood products. Thirty-nine black spruces and 34 jack pines were analysed at the tree level. On average, compression wood represented 14% and 20% of stem volume in 7- and 10-year old black spruce plantations, respectively. These proportions ranged from 18% in the youngest jack pine plantation to 26% in the oldest one. Stems of both species classified as normal contained a lower volume of compression wood than stems classified as deformed or very deformed. Annual percentages of compression wood and annual shoot length increased significantly with tree age (p < 0.0001 for both variables). Statistically significant correlations were also found between the range of displacement of the stem and the percentage of compression wood. The fewer number of trees with deformed stems in older plantations combined with high compression wood formation suggests that, over time, a deformed tree can become normal and straight in appearance.     

落叶松人工林天然更新及近自然经营

红松在落叶松下更新能够将其诱导形成红松针阔混交林,笔者就落叶松林内阔叶树组成、红松更新情况、林下灌木和近自然经营进行了调查分析,发现落叶松的长势、其伴生阔叶乔木的状况在下坡位均占优势,下坡位更新的红松密度最大。林下植被均较丰富,为红松幼年生长提供了良好的森林环境。     

西安市近自然林经营模式探讨

介绍了近自然林业经营理论及其在我国的研究与实践,分析了西安市林业建设中应用近自然森林经营理论的必要性。对西安市周边风景片林近自然林营造模式,秦岭北麓浅山区灌木林地近自然化改造模式和秦岭北麓油松、落叶松高密度人工纯林的近自然化改造模式进行了探讨。       

The effect of scalping on seedling establishment after seed tree cutting of Scots pine stands in drained peatlands in northern Finland

We studied the establishment of natural seedlings after seed tree cutting and scalping in two drained Scots pine peatland stands in northern Finland (Simo and Sievi). Approximately, 50?ha^?1 of Scots pine stems were retained on both sites. During the six subsequent years, five seedling surveys were conducted. The effect of site preparation was analysed using generalized linear mixed models (GLMM). The mean density of pine seedlings increased more quickly in the scalped plots and was ca. 1.1?m^?2 after six years compared to 0.87?m^?2 in the non-scalped plots, on average. Scalping increased the number of pine seedlings 2-fold compared to that in non-treated plots in Simo, however, in Sievi non-treated plots had 30% higher pine seedling density after six years. Downy birch seedling density was 9–10-fold compared to that of non-treated plots in both sites. In terms of seedling density, seed tree cutting led to satisfactory pine regeneration after just two growing seasons in drained pine peatlands, even without scalping. Scalping significantly increased the number of pine seedlings, but it also enhanced the germination of birch seedlings strongly.     

珍贵树种火力楠实生天然更新研究

通过林分样地调查和模拟天然更新发芽试验,研究珍贵树种火力楠(Michelia macclurei)实生天然更新情况,为火力楠可持续经营和种质资源保护等提供理论依据。结果显示:广西壮族自治区火力楠8个成熟人工林分林下天然更新实生苗木密度250~4000株·hm^-2,平均更新密度1395株·hm^-2;更新频度6.7%~66.7%,平均更新频度35.9%,实生天然更新等级为坏等级。天然更新苗木高度大部分为10 cm,地径0.1 cm,苗木规格小。2年度2批次播撒2000粒火力楠种子林下模拟天然更新成苗率为0。扩大火力楠森林面积规模需要采取人工造林措施。     

间伐对栓皮栎人工林林下更新的影响

栓皮栎是我国温带落叶阔叶林代表树种之一,是河南省山区典型地带性树种和主要造林树种。间伐作为一个重要的森林经营措施,研究其对林下更新的影响,可为改善栓皮栎人工林林分结构,维持林下物种多样性,制定科学合理的森林经营措施提供支撑。对间伐3 a后栓皮栎人工林林下幼苗更新物种及更新多样性进行调查,结果表明:间伐后林地内幼苗种类和数量显著增加,间伐样地内单物种更新密度和总更新密度均高于未间伐样地,间伐样地内更新苗Shannon-Wiener、Simpson多样性指数、Patrick丰富度指数值、Pielou均匀度指数均高于未间伐样地相应数值,间伐有利于栓皮栎人工林林分结构优化和林分健康。     

Stand and landscape-level factors related to bird assemblages in exotic pine plantations: Implications for forest management

Plantations cover a substantial amount of Earth's terrestrial surface and this area is expected to increase dramatically in the coming decades. Pinus plantations make up approximately 32% of the global plantation estate. They are primarily managed for wood production, but have some capacity to support native fauna. This capacity likely varies with plantation management. We examined changes in the richness and frequency of occurrence of bird species at 32 plots within a Pinus radiata plantation (a management unit comprising multiple Pinus stands) in south-eastern Australia. Plots were stratified by distance to native forest, stand age class and thinning regime. We also assessed the landscape context of each plot to determine relationships between bird assemblages and stand and landscape-level factors. Bird species richness was significantly higher at plots ≥300 m from native forest and in mature (∼20 years since planting) and old (∼27 years since planting) thinned pine stands. We were able to separate the often confounding effects of stand age and thinning regime by including old stands that had never been thinned. These stands had significantly fewer species than thinned stands suggesting thinning regime, not age is a key factor to improving the capacity of pine plantations to support native species (although an age × thinning interaction may influence this result). At the landscape level, species richness increased in pine stands when they were closer to native riparian vegetation. There were no significant differences in species composition across plots. Our study indicates the importance of stand thinning and retention of native riparian vegetation in improving the value of pine plantations for the conservation of native fauna.     

Regeneration of Pinus sylvestris in a natural pinewood in NE Scotland following reduction in grazing by Cervus elaphus

The occurrence of Scots pine (Pinus sylvestris L.) seedlings and saplings (<2.0 m in height and suppressed by grazing) and ground characteristics were recorded in a 300 ha block of natural pine forest in 1993. The density of red deer (Cervus elaphus L.) was then reduced by exclosure to approximately 3–4 deer km⁻², which is below the threshold at which pine regeneration should occur. Numbers and performance of pine seedlings and saplings were further monitored 2 and 4 years after exclosure. Numbers of young pine increased over time. In the three years with observations 97–99% of pine seedlings and saplings were recorded within 20 m of a seed source. Stepwise multiple regression was used to explore the relationships of pine establishment with plot characteristics for (a) all observation plots (n = 178) and (b) plots within 20 m of a seed source (n = 154). The factors most closely related to the number of pine seedlings and saplings in 1997 were, for (a), seed–source distance, vegetation height, blaeberry cover, slope and deer pellet-group density in 1993, all but the last having negative effects. For (b), vegetation height, blaeberry cover and slope were again selected predictors, and again had negative effects. Possible mechanisms by which the selected main effects may influence pine regeneration are discussed, the positive relationship to deer density being considered to reflect the creation of gaps in the sward suitable for germination. However, the amounts of variation explained in the models were low, being 16% for (a) and 13% for (b), reflecting the patchy nature and diverse age of the regeneration.     

Natural regeneration characteristics of Pinus sylvestris var. mongolica forests on sandy land in Honghuaerji, China

Natural regeneration in Mongolian pine, Pinus sylvesttis var. mongolica, forest at Honghuaerji of China （the original of the natural Mongolian pine, forest on sandy land） was studied in 2004. The total mean values of regeneration indexes were higher in mature stands （more than 80% individual stems were older than 50 years）, the maximum of regeneration index reached 29 seedlings, m^ 2, with lowest values in the younger stand, e.g., in 32-year old and 43-year old stands. The stand age was an important factor determining the natural regeneration, which was the best in the older stands in this investigation （e.g. about 80-year old）. The regeneration index seemed not to be closely in relation to canopy openness although Mongolian pine is a photophilic tree species. In each type of gaps, natural regeneration was very well. Regeneration indexes were satisfactory at the south and east edges in the circle gaps; and at the east edge of the narrow-square gaps. Results indicated that Mongolian pine, seedlings could endure shading understory, but it would not enter the canopy layer without gap or large disturbance, e.g., fire, wind/snow damage or clear cutting etc. These results may provide potentially references to the management and afforestation of Mongolian pine, plantations on sandy land in arid and semi-arid areas. Researches such as the comprehensive comparisons on regeneration, structure and ecological conditions and so on between natural Mongolian pine, forests and plantations should be conducted in the future.