Stand development patterns of forest cover types in the natural forests of northern Baekdudaegan in South Korea

The purpose of this study was to classify current forest cover types,and to investigate stand development patterns for natural forests in six areas in northern Baekdudaegan,South Korea.Twenty-eight independent forest communities were aggregated into eight forest cover types by species composition in the overstory of each forest community.The forest cover types were of mixed mesophytic,‘‘others’ ’ deciduous,Quercus mongolica dominant,Q.mongolica pure,Pinus densiflora–Q.mongolica,P.densiflora,Betula ermanii,and Q.mongolica–P.koraiensis.The ecological information was organized by importance value and species diversity for each forest type.Based on the correlation between species diversity index and the abundance of Q.mongolica plus P.densiflora for corresponding forest cover types,we compared the developmental process and approximate successional pathway between each cover type.The P.densiflora forest cover type changes into the P.densiflora–Q.mongolica cover type,followed by the Q.mongolica dominant cover type through continuous invasion of the oak trees.Furthermore,the Q.mongolica pure cover type would spread toward the Q.mongolica dominant cover type with a mixture of various deciduous tree species.The Q.mongolica dominant cover type progresses through the other deciduous cover types to the mixed mesophytic cover type with diversified composition and structure.On the mid to lower slopes,with loamy soils and good moisture conditions,various deciduous forest types should progress,by ecological succession,toward the mixed mesophytic cover type without any further disturbance.

Quantitative division of succession and spatial patterns among different stand developmental stages in Changbai Mountains

Broadleaf-Korean pine forests exhibit high species richness and distinctive species composition, which are currently becoming more dominant among natural forests in Changbai Mountains of northeastern China. Understanding the ecological process of restored vegetation is quite important for ecosystem reconstruction. Distinguishing stand development stages and analyzing the dynamic spatial patterns could provide insights into significant community coexistence mechanisms. In the present study, eight permanent study areas were established according to the substituting space for time method in Changbai Mountains of north-eastern China. The optimal division method was used to quantify the successional series into different stand development stages, and the point pattern analysis method(L(r) function) was used to analyse the dynamic changes in spatial patterns and interspecific associations. Our results suggested that:(1) The stand development process was divided into five stages: the first three stages were poplar-birch secondary forests in different stages of recovery, the fourth stage was thespruce-fir mixed forest, and the last stage was the primary broadleaf-Korean pine forest;(2) The spatial pattern showed an aggregated distribution at a small scale and changed to a random distribution as the scale increased in poplar-birch secondary forests, but the spatial pattern appeared to be randomly distributed in spruce-fir mixed forest and broadleafKorean pine forest;(3) The interspecific associations between pioneer species and climax species changed from negative to positive among the different stand stages, and environmental resources were shared among these species. Interspecific differences in shade tolerance among the tree species were key determinants of forest dynamics and structure. Our study is vital to the understanding of the forest development;thus, the spatial change features should receive greater attention when forest management is being planned and restoration strategies are being developed for the Changbai Mountains.

Effects of precommercial thinning intensity on growth of Fagus orientalis Lipsky stands over 6 years

Determining the most suitable intensities for precommercial thinning (PCT) in oriental beech (Fagus orientalis) stands, which cover substantial areas in Turkey and have a high economic and ecological value, is essential to provide higher economic return and obtain well-formed stems. The effects of various rates of PCT interventions on the growth characteristics of natural stands, located in the northern part of Turkey, were explored to determine appropriate thinning rates;24 experimental PCT plots (4 PCT rates × 3 replications × 2 sites) were established in young thicket-stage stands and four precommercial thinning rates such as light (1 – 1.5 m spacing), moderate (1.5−2.0 m spacing) and heavy (2.5–3.0 m spacing) thinning, including a control plot (i.e., untreated), were applied. At the end of the 2007 and 2010 growing seasons, the diameter and height of the trees were measured and growth analyzed based on the 3-year and 6-year incremental growth. PCT levels were found to have significant (P < 0.05) effects on diameter, height, total basal area and total volume increment at the end of each period. The mean diameter and height increment proportionally increased with increasing PCT intensity in the third and the sixth year. In both sites, the moderate PCT provided the greatest total basal area and total volume increment. The early results indicate that the moderate PCT (1.5–2 m spacing) boosted stand development over time.

Response of plant,litter,and soil C:N:P stoichiometry to growth stages in Quercus secondary forests on the Loess Plateau,China

Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems.However,little is known about the response of ecological stoichiometry to plant growth.In this study,carbon(C),nitrogen(N),and phosphorus(P)concentrations were evaluated in plant tissues(trees,shrubs,and herbs),litter,and soil of young(≤40-year-old),middle-aged(41–60-year-old),near-mature(61–80-year-old),and mature(81–120-year-old)Quercus secondary forests on the Loess Plateau,China.Vegetation composition,plant biomass,and C stock were determined to illustrate their interaction with stoichiometry.Only tree biomass C signifi cantly increased with stand development.Leaf N and trunk P concentrationsgenerally increased,but branch P decreased with growth stage.Fine roots had the highest C and P concentrations at the middle-aged stage.In contrast,shrubs,herbs,litter,and soil C:N:P stoichiometry did not change signifi cantly during stand development.Leaf N and P were positively correlated with soil C,N,P,and their ratios.However,there was no signifi cant correlation between litter and leaves in terms of C:N:P stoichiometry.A redundancy analysis showed that soil N best explained leaf N and P variance,and tree biomass and C stock were related to biotic factors such as tree age and shrub biomass.Hierarchical partitioning analysis indicated that,compared with soil or litter variables,stand age only accounted for a relatively small proportion of leaf C,N,and P variation.Thus,secondary Quercus ecosystems might have inherent ability to maintain sensitive responses of metabolically active organs to environmental factors during stand aging.The results of this work help to elucidate the biogeochemical cycling of secondary forest ecosystems in tree development,provide novel insights into the adaptation strategies of plants in diff erent organs and growth stages,and could be used to guide fertilization programs and optimize forest structure.

Aboveground biomass and nutrient allocation in an age-sequence of Larix olgensis plantations

Biomass and nutrient （N, P, K, Ca, Mg） stock in various aboveground tree components （stemwood, stembark, branches and leaves） were quantified in an age sequence of pure Larix olgensis plantations （20, 35, 53 and 69 years old） in Northeast China. The results show that the aboveground biomass allocation in various tree components was in the order of stemwood （62%-83%）, branches （9%-21%）, stembark （7%-11%） and leaves （1%-6%） for all stands. The proportion of stemwood biomass to total aboveground biomass increased whereas that of other tree components decreased consistently with stand age from 20 to 53 years old, but kept relatively constant with stand age from 53 and 69 years old. The nutrient allocation in various tree components generally followed the same pattern as the biomass allocation （i.e. stemwood 〉 branches 〉 stembark 〉 leaves）. The proportion of nutrient stock in leaves to total aboveground nutrient stock decreased consistently with increasing stand age, while that in stemwood increased with stand age from 20 to 53 years old but then decreased from 53 to 69 years old. The rate of nutrient removal for stands was estimated at different stand ages under different logging schemes, showing that the rate of nutrient removal would be unchanged when the rotation length was shortened to 20 years by the harvest of stem only, but greatly increased by the harvest of total aboveground biomass. The rate of nutrient removal would be a considerable reduction for all elements by debarking, especially for Ca.

An imputation/copula-based stochastic individual tree growth model for mixed species Acadian forests： a case study using the Nova Scotia permanent sample plot network

Background： A novel approach to modelling individual tree growth dynamics is proposed. The approach combines multiple imputation and copula sampling to produce a stochastic individual tree growth and yield projection system. Methods： The Nova Scotia, Canada permanent sample plot network is used as a case study to develop and test the modelling approach. Predictions from this model are compared to predictions from the Acadian variant of the Forest Vegetation Simulator, a widely used statistical individual tree growth and yield model. Results： Diameter and height growth rates were predicted with error rates consistent with those produced using statistical models. Mortality and ingrowth error rates were higher than those observed for diameter and height, but also were within the bounds produced by traditional approaches for predicting these rates. Ingrowth species composition was very poorly predicted. The model was capable of reproducing a wide range of stand dynamic trajectories and in some cases reproduced trajectories that the statistical model was incapable of reproducing. Conclusions： The model has potential to be used as a benchmarking tool for evaluating statistical and process models and may provide a mechanism to separate signal from noise and improve our ability to analyze and learn from large regional datasets that often have underlying flaws in sample design.

Disturbance history,species diversity,and structural complexity of a temperate deciduous forest

Stand structural complexity enhancement is an increasingly popular management objective,especially on public lands.Complex stand structures are hypothesized to support a relatively high degree of native forest diversity and be more resistant and resilient to disturbances.Complex structures are characterized by the presence of deadwood and heterogeneity of tree-size classes and tree architecture.Relatively little is known about how discrete disturbance events affect structural complexity and compositional diversity in Quercus-dominated stands at fine spatial scales(i.e.neighborhoods).We established 200.05 ha fixed-radius plots on the Sipsey Wilderness of William B.Bankhead National Forest in northern Alabama to quantify woody plant species composition and structure.Trees were mapped on each plot to quantify overstory structural complexity and compositional diversity.We extracted two cores from all canopy Quercus spp.C 5 cm diameter at breast height to quantify age,recruitment pulses,and reconstruct canopy disturbance history.Shannon species diversity in the sampled area was 1.75 for trees,2.08 for saplings,and 1.69 for seedlings.Quercus alba had the greatest basal area,and Ostrya virginiana had the highest density.The stand exhibited a reverse J-shaped distribution with a q-factor of 1.72.The oldest Quercus dated to 1795,and the largest recruitment pulse occurred in the 1870s.The mean return interval for intermediateseverity disturbance was 38 years.Although we documented no relationships between disturbance frequency and compositional diversity at the neighborhood scale(0.05 ha),less frequent disturbance was associated with higher structural complexity(r^2=0.258,p=0.026)at the neighborhood scale.We suggest that localized disturbance increases species diversity and structural complexity,but these processes are manifest at the stand level and not at the neighborhood scale.We conclude that the spatial variability(i.e.size,shape,orientation,microsite conditions)is likely more influential on diversity and complexity than the temporal variation(frequency)of these processes at the neighborhood scale.

黑龙江省工业用材林资源现状及发展对策

本文以加快黑龙江省工业用材林发展、满足市场需求为出发点,从资源现状方面对黑龙江省工业用材林发展进行了综 合分析,并在此基础上提出了未来的发展对策,以期为黑龙江省优质工业用材林发展决策提供技术支持.

不同发育阶段马尾松人工林经营效果动态分析

为揭示不同发育阶段马尾松人工林经营效果的动态变化特征规律,对青羊湖林场不同发育阶段的马尾松人工林(幼龄林、中龄林、近熟林)林分空间结构、物种多样性、土壤肥力、林木生长等指标进行动态分析,运用主成分分析法,对不同发育阶段的各经营样地的经营效果进行综合评价。结果表明:不同发育阶段的马尾松林在经营改造后,空间结构明显改善,物种多样性指数均明显提高,土壤肥力也有所改善;幼龄林、中龄林和近熟林9块样地抚育间伐补植改造效果综合评价得分依次为0.079,-0.021,-0.241,0.528,0.438,1.028,-0.145,-0.780,-0.886,得分越高说明改造经营效果越好。经营促进了不同发育阶段马尾松人工林林分空间结构的优化、树种多样性的提高、土壤肥力的改善和林木蓄积生长的提高,林分向异龄复层混交林方向发展,为马尾松人工林经营提供理论依据。

动作发展序列理论及体育教学案例分析

为突显以学生为中心的教学理念,提供给体育教学、运动训练工作者动作发展序列理论与实践资源。运用文献资料、个人教学实践等研究方法,针对动作发展中动作发展序列理论与实践、当前体育与健康的课程标准、教师用书、教科书中相关运动技能学习内容设计进行研究分析。得出动作整体与部分发展序列的相关特征价值,即整体发展序列的阶段性、可预见性、基础动作与生理年龄的相关性;部分发展序列中特定项目的动作特征形象与特征途径的组合性。剖析动作发展序列的应用局限性。同时采用教学案例方式针对跑步、立定跳远项目的发展序列特征与体育教学中内容设计进行分析和相关原理阐述。

Two decades of compositional and structural change in deciduous old-growth forests of Indiana,USA

Aims Using a network of permanent plots,we determined how multiple old-growth forests changed over an 18-19-year period at a state-wide scale.This examination of change allowed us to assess how the compositional and structural stability of each forest varied with site characteristics(topography,physiography and productivity)and stochastic disturbance.Methods In 2011,we resampled 150 plots distributed across five old-growth hardwood forests in Indiana,USA that were originally sampled in 1992-1993.Within each plot,we relocated and remeasured the diameter at breast height(dbh)of all trees(≥10.0 cm)present during the 1992-1993 sample,which allowed us to track their individual fates through time for growth and mortality calculations.Trees that grew to≥10.0 cm dbh since plot establishment were designated as ingrowth.The dbh and species of all saplings(stems≥2.0 cm but<10.0 cm dbh)were also recorded.For each forest,we calculated density(stems ha^(−1)),basal area(BABA;m^(2)ha^(−1))and importance value(relative density+relative BABA)/2 of trees by species.For saplings,density per ha was calculated by species for each forest.We also calculated annual mortality rate(AMR)for three diameter classes(10-29.9,30-59.9 and≥60 cm)and species richness(S),evenness(E)and Shannon-Weiner diversity(H')for the tree and sapling layers.Differences between years were compared for each forest using paired t-tests and Wilcoxon signed rank tests.Important FindingsAlthough we observed commonality in changes across some sites,our results suggest that these forests differ in their rates and trajectories of change.Changes in total stand BABA and density varied across sites and were influenced by past disturbance and mortality rates.We observed a general increase in the overstory dominance of Acer saccharum coupled with a general decrease in the dominance of Quercus section Lobatae(red oak group)species.Mortality of overstory trees present in 1992-1993 ranged from 27%to 49%over the study period(mean AMR 1.6-3.7%).Most sites experienced greater mortality of early and mid-successional species,but one site experienced heavy mortality of Fagus grandifolia,a shade-tolerant late-successional species.Shade tolerant species,A.saccharum in particular,dominated the sapling layer at most sites.However,recruitment of this species into larger size classes did not occur uniformly across all sites and the species was comparatively uncommon at one site.Overall,our results suggest that old-growth remnants,even within a single state,cannot be viewed as equivalent units with regard to research or management.Stochastic disturbance events and surrounding land use may have amplified effects on small scattered remnants.Therefore,continued monitoring of these rare,but biologically important forests is critical to their long-term management and protection.

DDH患者仰卧位与站立位X线片的差异分析

目的比较发育性髋关节发育不良(DDH)患者仰卧位及站立位骨盆X线片测量值间的差异特点,以指导临床合理规划术前方案。方法选取DHH患者80例(99髋)为研究组,健康体检者25例(50髋)为对照组。对两组均进行仰卧位及站立位骨盆前后位X线片检查,测量并分析两组受试者耻骨联合与骶尾关节距离(PSSC),评估骨盆矢状面倾斜情况。测量并分析DDH患者外侧中心边缘角(LCEA)、臼顶倾斜角(TA)、锐角(SA)、股骨髋臼顶(FEAR)指数、股骨骨骺水平角(FEHA)、腿长差异(LLD)和骨盆倾斜度(PO)。结果仰卧位时,对照组PSSC高于研究组(P<0.05);站立位时,研究组PSSC高于对照组(P<0.05)。两组仰卧位PSSC明显高于站立位(均P<0.05)。从仰卧位转变为站立位,DDH患者男女测量值之间差异均无统计学意义(P>0.05);PSSC的变化与患者的TA(r=-0.195;P=0.006)及FEAR(r=-0.144;P=0.043)呈负相关;与LCEA(r=0.140;P=0.049)呈正相关。结论DDH患者体位由仰卧位变换为站立位可引起骨盆矢状面向后倾斜,同时LCEA、PO变小,TA、SA、FEAR、FEHA、LLD变大。当DDH患者进行手术之前,应联合应用仰卧位及站立位骨盆正位X线片评估髋关节实际覆盖及受力情况。