林分密度对桉树幼龄能源林的影响

对0.5年生3种不同密度配置的幼龄尾巨桉优良无性系DH32-29各器官生物量、热值以及灰分进行了调查和测定,结果表明:所选3种密度间树高差异显著,基径差异达到极显著水平,随着密度的增加,树枝、叶片、树干的生物量分别呈现减少趋势,密度与树枝和树干生物量的相关性达到了0.01极显著水平;单株生物量随密度的增大而减小,林分生物量则相反;单株热值无显著差异,仅单株平均灰分含量高密度与中密度存在显著差异。综合分析,高密度0.25 m×2 m林分生物量最大,其灰分含量比低密度的林分低,适合作为能源林培育密度。     

广东郁南尾巨桉人工林密度效应

采用随机区组试验设计在广东省郁南县西江林场设置了4种株行距(1.7 m×4 m,2.0 m×4 m,2.5 m×4 m,3.0 m×4 m)试验,分析不同造林密度(1470、1250、1000、833株 ·hm-2)对0.8~7.8 a生尾巨桉(Eucalyptus urophylla×E.grandis)人工林保存率、树高、胸径、单株材积和林分蓄积量的影响.结果表明:不同造林密度对林分的保存率、树高、胸径、单株材积和蓄积量均有显著的影响;除0.8 a生的林分保存率外,其它年龄的林分保存率均随着造林密度的增加而降低,1470株 ·hm-2与其它3种密度间的林分保存率存在显著差异;造林密度对林分平均高有一定的影响,但差异较小;随着造林密度的增加,林分平均胸径和单株材积逐步递减,1470、1250株 ·hm-2与其它两种密度间的平均胸径和单株材积在2.8~7.8 a生时均存在显著差异;在7.8 a生时,以1250株 ·hm-2为造林密度的林分蓄积量最大,达195.0 m3·hm-2,分别比造林密度为1470、1000、833株 ·hm-2的林分高16.28%、5.86%和14.37%.以获得较高的林分蓄积量为目标,初步推荐1000~1250株 ·hm-2的造林密度.     

板栗不同密度林分的生长发育与生物生产力

通过对4种不同密度8年生板栗园树体生长发育、生物量、对生物生产力的系统分析，研究了板栗密植园的生长分化机理．栽植密度区显著影响板栗树体的生长发育；它不仅对单株生物量及林分生物量存在显著的影响，同时也影响生物量在枝、叶、果中的分配比例．不同密度林分的净生产量、经济利用系数、太阳能利用率均存在一定的差别，这种差别随林分年龄的变化而变化．高密度林分可获得早期产量的迅速提高．但达到一定年龄阶段（6年生）以后必须进行适时间伐，以保持林分产量的相对稳定．     

间伐对马尾松天然次生林林下植物多样性的影响

选择12和14地位指数的2种立地的林分,分别设置6种和5种保留密度,对间伐4年后的23年生马尾松天然次生林林下植物多样性进行研究。结果表明:马尾松天然次生林林下植物种数随着林分保留密度的增大,12和14地位指数的林分均表现为由逐渐增加至一个峰值后逐渐减少;适宜的保留密度有利于提高林下植物的多样性,12和14地位指数林分的植物多样性分别以保留密度130株/667 m2和100株/667 m2的样地为最优;随着林分密度与冠层郁闭度的增大,林下植物类型有由阳性植物为主向中性与荫性变化的趋势,而形成阳性、中性及荫性共存的多态性植物群落;适宜的保留密度有利于提高林下植物的生物量和植被总盖度,12和14地位指数林分的林下植物生物量和植被总盖度分别以保留密度130株/667 m2和90株/667 m2的样地为最佳;2种地位指数不同保留密度林分的林下枯落物自然风干重、枯落物层厚及腐殖质层厚差异均不显著,而林下地被物鲜重和植被总盖度则均表现为差异极显著。     

Biomass production and potential water stress increase with planting density in four highly productive clonal Eucalyptus genotypes§

The choice of planting density and tree genotype are basic decisions when establishing a forest stand. Understanding the interaction between planting density and genotype, and their relationship with biomass production and potential water stress, is crucial as forest managers are faced with a changing climate. However, few studies have investigated this relationship, especially in areas with highly productive forests. This study aimed to determine the interaction between biomass production and leaf water potential, as a surrogate of potential water stress, in different clonal Eucalyptus genotypes across a range of planting densities. Four clones (two clones of E. urophylla × E. grandis, one clone of E. urophylla, and one clone of E. grandis × E. camaldulensis) and four planting densities (ranging from 591 to 2 949 trees ha^?1) were evaluated in an experimental stand in south-eastern Brazil. Biomass production was estimated 2.5 years after planting and predawn (ψ_pd) and midday (ψ_md) leaf water potential were measured 2 and 2.5 years after planting, in February (wet season) and August (dry season) in 2014. For all clones, total stand stemwood biomass production increased and leaf water potential decreased with planting density, and their interaction was significant. Thus, wood biomass at tighter spacings was higher but exhibited lower leaf water potentials, resulting in a trade-off between productivity and potential water stress. These are preliminary findings and still need to be supported by more experimental evidence and repetitions. However, in light of the increased frequency of extreme climate events, silvicultural practices that are tailored to the potential productivity of each region and that result in low potential water stress should be considered.     

I-69杨胶合板用材林产量及生物量结构

采用 2 90块标准地调查资料 ,分析了 I- 6 9杨胶合板用材林的产量和生物量结构随立地指数和造林密度的变化规律。胶合板材产量随立地指数的增大而增大 ,且占总产量的百分比在立地指数为 14、16、18m时 ,随造林密度的增大而减小 ;当立地指数为 2 0 m和 2 2 m时 ,保持稳定在 50 %左右。磨木浆材和化学浆材产量随立地指数和密度的增大而增加。在立地指数为 14、16、18m时磨木浆材产量占总蓄积量的百分比和化学浆材产量占总蓄积的百分比均随造林密度的增大而增大 ;在立地指数为 2 0、2 2 m时则受造林密度的影响不大 ,分别保持在 30 %和 2 0 %左右。林分和单株的树干、树枝、树皮生物量组成比例均随立地指数、造林密度的变化无明显的差异。营造 I- 6 9杨胶合板用材林时选择立地指数 2 0、2 2 m的地段以及用造林密度 156 (8m× 8m)、2 0 4 (7m× 7m )株·hm-2 为最佳。     

Stand age and fine root biomass, distribution and morphology in a Norway spruce chronosequence in southeast Norway

We assessed the influence of stand age on fine root biomass and morphology of trees and understory vegetation in 10-, 30-, 60- and 120-year-old Norway spruce stands growing in sandy soil in southeast Norway. Fine root (< 1, 1-2 and 2-5 mm in diameter) biomass of trees and understory vegetation (< 2 mm in diameter) was sampled by soil coring to a depth of 60 cm. Fine root morphological characteristics, such as specific root length (SRL), root length density (RLD), root surface area (RSA), root tip number and branching frequency (per unit root length or mass), were determined based on digitized root data. Fine root biomass and morphological characteristics related to biomass (RLD and RSA) followed the same tendency with chronosequence and were significantly higher in the 30-year-old stand and lower in the 10-year-old stand than in the other stands. Among stands, mean fine root (< 2 mm) biomass ranged from 49 to 398 g m(-2), SLR from 13.4 to 19.8 m g(-1), RLD from 980 to 11,650 m m(-3) and RSA from 2.4 to 35.4 m(2) m(-3). Most fine root biomass of trees was concentrated in the upper 20 cm of the mineral soil and in the humus layer (0-5 cm) in all stands. Understory fine roots accounted for 67 and 25% of total fine root biomass in the 10- and 120-year-old stands, respectively. Stand age had no affect on root tip number or branching frequency, but both parameters changed with soil depth, with increasing number of root tips and decreasing branching frequency with increasing soil depth for root fractions < 2 mm in diameter. Specific (mass based) root tip number and branching density were highest for the finest roots (< 1 mm) in the humus layer. Season (spring or fall) had no effect on tree fine root biomass, but there was a small and significant increase in understory fine root biomass in fall relative to spring. All morphological characteristics showed strong seasonal variation, especially the finest root fraction, with consistently and significantly higher values in spring than in fall. We conclude that fine root biomass, especially in the finest fraction (< 1 mm in diameter), is strongly dependent on stand age. Among stands, carbon concentration in fine root biomass was highest in the 30-year-old stand, and appeared to be associated with the high tree and canopy density during the early stage of stand development. Values of RLD and RSA, morphological features indicative of stand nutrient-uptake efficiency, were higher in the 30-year-old stand than in the other stands.     

南方型杨树人工林生物量与生产力研究

对湖北省10个县、市31块标准地的11种主要密度类型林分的生物量与生产力进行了研究。结果表明:南方型杨树单木生物量随着林分密度的增大而减小,林分生物量随密度的增大而增加。在各组份生物量中,树干最大,树枝其次。单木和林分地上部分生物量占总生物量的比例,达91.22％～92.19％,且林分密度越高,比例越大。中等密度林分的生物量结构特征较合理,生产潜力较大,应作为全省杨树栽培的主要模式。林分密度对净生产力有显著影响,随着林分密度的降低,林分和林分各组份的净生产量也随之降低。     

Planting spacing affects canopy structure,biomass production and stem roundness in poplar plantations

To improve the productivity and wood quality of poplar plantations, effects of four planting spacing on canopy characteristics, biomass production and stem roundness in poplar plantations were evaluated over 8 years. Planting spacing influenced canopy characteristics of the plantations, and further affected the understory vegetation and plantation productivity. Understory vegetation biomass and Shannon-Wiener index were negatively correlated with leaf area index, but both diversity indexes and aboveground biomass of understory vegetation were higher in stands with a wider spacing. Tree diameter growth increased with increasing planting spacing, while the increment in plantations of square configurations (5?×?5 m and 6?×?6 m) was higher than those with rectangular configurations (3?×?8 m, 4.5?×?8 m). The highest poplar biomass production was achieved in the plantation with 5?×?5 m spacing at age 8. Moreover, poplar trees showed a tendency with better stem roundness in a square configuration. The results suggest that planting spacing not only affect canopy characteristics, understory vegetation and tree growth but also wood quality, and square configurations (5?×?5 m and 6?×?6 m) could be a better option for poplar plywood timber production at similar sites.     

不同栽杉代数29年生杉木林净生产力及营养元素生物循环的研究

对南平溪后２９年生杉木林不同连载代数林分生物量、净生产力及营养元素生物循环的研究结果表明：随连载代数增加，林分总生物量下降，林分净生长量及乔木层净生长量占林分净生长量比例均有明显降低，生态系统中营养元素贮量减少，乔木层营养元素吸收量、存留量和归还量均下降，但林下植被层营养元素吸收量、存留量和归还量则明显增加，林分的营养元素吸收量、存留量和归还量却增大。不同代数杉木林营养元素总的循环速率为２代（０．     

不同密度杉木林分生物量结构与土壤肥力差异研究

对２９年生五种造林密度生物量结构及土壤肥力进行了全面研究，结果表明：平均单株及其各器官生物量随密度增加呈递减趋势；单位面积不同密度的杉木林分生物量及其生产力基本趋于一致；各种密度单位面积现存枯枝落叶量随密度增加而增加，而林下植被生长及其生物量则相反；五种密度林分土壤自然含水量、最大持水量和毛管持水量基本上以２８０５株／ｈｍ２和３７５０株／ｈｍ２较大；土壤非毛管孔隙度，毛管孔隙度和总孔隙度均随密度增加而增大；土壤有机质、全Ｎ、全Ｐ、水解Ｎ和速效Ｐ的含量随密度增加而下降；而速效钾含量变化规律性不明显。因此，杉木初植密度尽量控制在２８０５—３７５０株／ｈｍ２之间，以利于杉木产量提高和地力维护。     

Biomass, basic density and biomass expansion factor functions for European beech (Fagus sylvatica L.) in Denmark

The objective of this study was to analyse the within-tree allocation of biomass and to develop biomass functions for above- and below-ground components of European beech in Denmark. Separate functions were developed for stem, branches, below-ground stump and root system, total above-ground biomass and total tree biomass. For each of these components or aggregate components, models were also developed for the average basic density of wood and bark. To enhance the versatility of the models, a function for estimating the biomass expansion factor (BEF) was also developed. The functions were based on 66 trees measured for total biomass. Model performance was evaluated based on 74 trees measured only for above-ground biomass. The trees were sampled in 18 different forest stands covering a wide range of tree sizes and stand treatments. Models were estimated using a linear mixed-effects procedure to account for within-stand correlations. The functions for biomass and BEFs included only diameter at breast height and total tree height for individual trees as predictor variables. Inclusion of additional variables reflecting site quality or stand density did not improve model performance. The functions for basic density included individual tree diameter, tree height and quadratic mean diameter as predictor variables, indicating an effect of stand density on the basic density of wood and bark.     

杉木人工林连作生物生产力的研究

在全国杉木中心产区，选择不同栽植代数（1、2、3代），不同生长发育阶段（5、10、15、20a)及不同立地（14、16、18地位指数）的杉木人工林，进行不同栽植代数杉木人工林生物生产力的比较研究。结果表明：连栽导致了不同生长发育阶段杉木人工林生产力的明显下降，随栽植代数增加，不同生长发育阶段杉木林林分生物量逐代递减，林下植被生物量呈递增趋势，其中2、3代20a生杉木林林分生物量分别比1代下降20.24%和38.09%，3代比2代下降22.38%。同时林分树干生物量所占比例下降，根系生物量所占比例增加，连栽刺激了杉木根系生长发育，并有利于林下植被恢复。     

龙头山林场华北落叶松低效林生物量分析

森林生物量是森林生态系统的最基本数量特征,是研究许多森林问题和生态问题的基础。本试验以木兰林管局龙头山林场道坝子营林区华北落叶松低效林为研究对象,通过野外调查和室内测定相结合的方法,对其乔木生物量进行研究。结果表明：（1）随着密度的变化,上坡位密度达到大约800株/hm^2时,林分生物量和单木生物量达到最大47 000kg/hm^2和50kg;中坡位生物量则单调下降;下坡位最低生物量出现在300株/hm^2。（2）上坡位单木生物量为39.65kg、中坡位40.18kg、下坡位72.31kg,呈上升趋势。而林分内生物量则相反。（3）不同坡位单木各器官生物量相比,单木的叶、枝生物量均在下坡位取得最大比重,干生物量在上坡位取得最大比重（0.83）。     

毛乌素沙地樟子松壮苗深栽造林效果分析

为提高毛乌素沙地樟子松的造林效果,开展了壮苗深栽试验。在总结壮苗深栽技术要点的基础上,分析了壮苗深栽的造林效果及其生物量分配格局调节规律。结果表明,壮苗深栽可以提高根系分布层的土壤含水量,从而提高造林保存率和林木生长量。且随着林分年龄的增大,壮苗深栽与常规栽植林分的生长量差异越来越大。究其原因,壮苗深栽提高了各个构件的生物量投资,同时将更多的生物量分配于地上部分的生长发育。     

Effects of planting orientation and density of willows on biomass production and nutrient leaching

Willow buffer strips are a promising vegetated filter for the reduction of non-point source pollution from agricultural land to watercourses resulting from the rapid growth of shoots and from the large amount and distribution of roots. A greenhouse experiment tested the hypothesis that a new planting method, planting cuttings horizontally, exhibited more biomass production and more effective filter than did planting cuttings vertically. Due to the different times taken for shoots break through the soil surface, the summed height of all shoots of horizontally planted cuttings was significantly smaller than that of the vertical ones at the beginning of the growth period. The difference in the height of all of the shoots between planting orientations decreased with time. After 16 weeks growth, the biomass of the stem, leaves and fine roots was not affected by the planting orientation. The coarse root biomass was larger in the horizontal treatments and decreased with increased density. The total biomass, as well as the biomass of stem or leaves, of each treatment, increased with increased planting density. The individual plant biomass, as well as that of the stem or leaves, decreased with increased planting density. Compared with the unplanted control treatment, the planted treatments significantly reduced the total-N, NO₃-N, PO₄-P and SO₄-S leaching. The planting orientation did not affect the nitrate leaching. The horizontally planted cuttings were slightly more effective for reducing the SO₄-S leaching and the vertically planted cuttings were slightly more effective for reducing the PO₄-P leaching. Lower PO₄-P leaching was observed only with higher planting density. With regard to the horizontal planting method, further studies are needed to explore the influence of different willow clones, the size of cuttings, pre-planting treatments, planting geometry (configuration) and soil conditions on survival, the number of shoots produced, the biomass production and the amount and distribution of roots.     

Crown radius of pedunculate oak (Quercus robur L.) depending on stem size,stand density and site productivity

Crown size is a good indicator of the growth potential of trees and is often used in forest management for outlining thinning guidelines or constructing forest growth models. The aim of this study was to analyse mean crown radius as a function of stem size, stand density and site productivity in even-aged stands of pedunculate oak (Quercus robur L.). Data included measurements of 620 trees from 53 plots in nine thinning experiments and one operational stand in Sweden, Denmark and Great Britain, representing a wide spectrum of thinning practices ranging from the strictly unthinned control to extremely heavy thinning with essentially solitary trees. Three sets of models were constructed based on different predictor variables, including indicators of individual stem size (diameter at breast height, DBH), stand density/thinning grade (quadratic mean diameter and stand basal area) and site productivity (stand top height). Preliminary results indicated a significant effect of DBH and (nominal) thinning grade on crown radius. The response pattern of the final models indicated an increasing crown radius with increasing DBH, with increasing thinning grade (decreasing stand density) and with decreasing site productivity. The models are valid for predicting the crown radius of pedunculate oak in even-aged forest stands.     

合理的密度管理是提高林分生产力的重要途径——从世界种群密度理论研究的现状看深入研究的必要性

本文通过对各国有关植物种群密度与生长理论研究专著、论文、试验报告中的数据和结论进行分析,结合作者的研究实践,说明在密度与收获量的模式中的一定区间内存在着C—D效果(竞争—密度效果)和Y—D效果(收量—密度效果),指出了林分合理密度有显著的增产效益。认为过去笼统地认为植物种群密度对总生物量或总产量影响不大的观点并不准确。本文指出合理密度的增产效益有其空间结构和功能的理论基础,有深入研究的必要。     

Productivity of kayu putih (Melaleuca leucadendron LINN) tree plantation managed in non-timber forest production systems in Java,Indonesia

Kayu putih oil, extracted from the kayu putih tree (Melaleuca leucadendron), is an important non-timber forest product (NTFP) in Indonesia. We compared productivity of kayu putih tree plantations among three different sites in East, Central, and West Java, Indonesia. Leaf-twig, and branch production per tree differed significantly among the three sites. Tree biomass production was highest at the site in West Java practicing tumpangsari (a form of shifting cultivation) of kayu putih with rice (Oryza sativa) on alluvial soils. Tree biomass production was lowest at the site in East Java, practicing tumpangsari of kayu putih with maize (Zea mays) and cassava (Mani- hot esculenta). At this site, tree biomass production increased with increasing stand age and low production was compensated by greater biomass yield of companion crops. Intermediate tree biomass production was observed at the site in Central Java where intercropping is only practiced for the first two years after plantation establishment. Production of tree biomass and kayu putih oil did not increase with increasing stand density, indicating that at a given site, high tree stocking did not lead to high production. Stand-level productivity of the plantations increased with increasing stand age and maximum productivity was attained at 15 to 35 years, after which productivity declined. This suggested unsustainable stand productivity as plantations increase in age.     

Spatial heterogeneity of fine root biomass of Pinus massoniana forests in the Three Gorges Reservoir Area, China

Environmental heterogeneity is a constant presence in the natural world that significantly affects plant behavior at a variety of levels of complexity. In order to estimate the spatial pattern of fine root biomass in the Three Gorges Reservoir Area, the spatial heterogeneity of fine root biomass in the upper layer of soils (0-10 cm) in three Masson pine (Pinus massoniana) stands in the Three Gorges Reservoir Area, China, was studied in 30 m × 30 m plots with geostatistical analysis. The results indicate that 1) both the live and dead fine root biomass of stand 2 were less than those of other stands, 2) the spatial variation of fine roots in the three stands was caused together by structural and random factors with moderate spatial dependence and 3) the magnitude of spatial heterogeneity of live fine roots ranked as: stand 3 > stand 1 > stand 2, while that of dead fine roots was similar in the three stands. These findings suggested that the range of spatial autocorrelation for fine root biomass varied considerably in the Three Gorges Reservoir Area, while soil properties, such as soil bulk density, organic matter and total nitrogen, may exhibit great effect on the spatial distribution of fine roots. Finally, we express our hope to be able to carry out further research on the quantitative relationship between the spatial heterogeneous patterns of plant and soil properties.