福建柏马尾松混交林疏伐效果研究

对不同立地条件下的福建柏马尾松混交林进行疏伐试验研究,结果表明,疏伐能明显改善混交林分的光合作用强度和林地土壤肥力等生态环境条件,且疏伐强度越大,改善的幅度也加大;不同疏伐强度对混交林分生长的影响较大,对主林木居第一林层的混交林,可采用强度疏伐即疏伐伴生木株数占总株数的45%。对于主林木与伴生木居同一林层的混交林,可采用中度疏伐即疏伐伴生木株数占总株数的30%。而对立地条件较差、主林木居第二林层的混交林,则以弱度疏伐为宜即疏伐株数占总株数的15%。     

疏伐和施肥对福建柏马尾松混交林效应研究

适当疏伐有助于使混交林种间关系向有利方向发展 ,不同混交林类型对疏伐措施的反应不尽相同。福建柏为上层木、中层木的混交林经疏伐 ,对主林木树高、胸径和材积生长均有显著的促进作用 ,前者保持着强度疏伐 >全伐 >中度 >弱度 >对照的关系 ;后者则遵循弱度疏伐 >中度 >强度 >极强度 >对照的规律 ;福建柏为下层木的混交林 ,则不同疏伐处理强度对主林木树高、胸径、材积生长以及林分总蓄积量没有显著影响。适当的疏伐处理改善了林内的环境条件 ,为植物的侵入提供了可能性 ,同时也改变了原有的种群结构和数量 ,可以丰富混交林下的植物种类 ,增加混交林群落中的植物的多样性。福建柏 (下层木 )马尾松混交林经合理施肥有利于促进主林木生长 ,较佳的施肥量组合为 1hm2 施尿素 15 0kg、钙镁磷肥 30 0kg、氯化钾 10 0kg。     

生态疏伐对华北落叶松林分结构和生物多样性的影响

森林抚育对调整林分结构、促进林木生长都具有极大作用。为了解抚育对华北落叶松林分结构和林下物种多样性的影响,以承德市第三乡林场华北落叶松—白桦混交林为研究对象,采用对比分析的方法,对生态疏伐前后的林分结构、径阶分布和生物多样性进行了探讨。结果表明:生态疏伐后林分平均胸径增加2.1cm,平均树高稍有变化,林分密度从疏伐前的1 365株/hm~2下降到900株/hm~2;生态疏伐前,直径分布曲线呈左偏,6~16径阶林木数量占总数的42.6%;疏伐后,6~16径阶林木株数占总株数的21.3%,直径分布稍向右偏,更趋于正态分布;疏伐后,林下物种的Simpson和Shannon-Wiener指数均有所增加,Pielou均匀度指数在1号、4号、5号样方内有所下降,2号、3号样方内呈增加趋势,且3号样方的Simpson、Shannon-Wiener和Pielou均匀度指数涨幅均最大,分别比抚育前增加了0.373、0.834和0.203。     

不同疏伐强度的云南松母树林结实效应

十余年来对腾冲县古永林场云南松母树林营建技术措施的试验研究表明：疏伐对林分母树树冠的生长发育具有明显的促进作用,随着疏伐强度的加大,林木树冠的增长也随之增加,而枝下高能保持相对稳定,由于结实层的增加,以及光、热、水、肥等环境条件的改善,提高了母树的结实量,从而降低了种子采集成本。在参试的几种疏伐强度中以保留郁闭度0.3处理的效果最好,其1993～1995年的每公顷年平均结实量、年平均单株结实量和结实株率分别达10 329个、60个和95.65%,超出对照25.81%、408.47％和15.37％。故对改建16年生左右的云南松天然优良林分为母树林,宜选用03（郁闭度）疏伐强度的技术措施,母树林经2次疏伐后即可定型,其疏伐间隔期不超过4年。     

不同疏伐强度的云南松母树林结实效应

十余年来对腾冲县古永林场云南松母树林营建技术措施的试验研究表明，疏伐对林分母树树冠的生长发充具有明显的促进作用，随着疏伐强度的加大，林木树冠的增长也随之增加，而持下高能保持相对稳定，由于结实层的增加，以及光、热、水、肥等环境条件的改善，提高了母树的结实量，从而降低了种子采集成本。在参试的几种疏伐强度中以保留部团度０．３处理的效果最好，其１９９３～１９９５年的每公地实量、年平均单株结实量和结实株率分     

杉木母树林遗传型疏伐和提高种子产量技术研究

为提高杉木种子产量和提供经过初步改良的优质种子,应在优良种源区选择１０～２０年生Ｉ类林分,通过疏伐建立采种基地示范林。疏伐强度随林分密度,林龄,郁闭度和立地条件而定,建立母树林要注意确定位置,隔离和母树选择。二次疏伐,间隔５年左右,强度为６０％～７０％,最终郁闭度为０．５,保留株数每公顷为３９０～４２０株左右为宜。研究结果表明,母树生长量,结实量有显著的增加。     

杉木母树林遗传型疏伐和提高种子产量技术研究

为提高杉木种子产量和提供经过初步改良的优质种子,应在优良种源区选择１０～２０年生Ⅰ类林分,通过疏伐建立采种基地示范林。疏伐强度随林分密度、林龄、郁闭度和立地条件而定。建立母树林要注意确定位置、隔离和母树选择。二次疏伐,间隔５年左右,强度为６０％～７０％,最终郁闭度为０５,保留株数每公顷以３９０～４２０株左右为宜。研究结果表明,母树生长量、结实量有显著的增加。     

疏伐频率及疏伐强度对不同种源史密斯桉母树生长的影响

依次按50%,40%,40%的疏伐强度对新建的史密斯桉母树林进行3次疏伐管理后,通过方差分析、多重比较(LSD法)以及相关性分析,研究疏伐频率及疏伐强度对不同种源史密斯桉母树生长影响。结果表明:疏伐频率对不同种源史密斯桉母树高、胸径、冠幅等生长指标的影响具有显著性差异;疏伐频率及疏伐强度与树高、胸径、冠幅的净生长量呈中度及中度以上相关。     

燕山低山丘陵油松林及其经营

本文通过对抚宁县、卢龙县境内的天然次生油松林的调查研究指出,由于近年来不合理的反复择伐和整枝,多数Ⅰ～Ⅱ龄级的油松林已成为径级小、干形不良和庇护土壤能力极低的稀疏林分。有纯林也有混交林,有同龄林也有异龄林。林内有油松和栎树的天然更新幼树。文中论述了用油松林疏伐保留株数标准控制油松林密度问题,并制定了合理整枝标准;特别强调对油松林应采取封山育林措施,促进油松的天然更新,变疏林为密林。     

火炬松用材林疏伐试验初报

5种疏伐处理的3年观测表明，累计2次疏伐株数62％的林分，平均胸径生长率比对照大28％；一次强度疏伐（50．4％）或一次中度疏伐（36％）并施磷肥的生长率比对照大20％～21％，各疏伐处理与对照间的协方差分析差异极显著。但不同处理与对照的树高生长差异不显著。2次疏伐林分冠幅比对照大10．3％～14．2％，枯枝高少29％～31％，差异显著。疏伐后个体粗生长明显加快，但蓄积量仍以对照为最大。     

马尾松纸浆原料林对不同间伐强度的生长反应

马尾松(ＰｉｎｕｓｍａｓｓｏｎｉａｎａＬａｍｂ)生长快、适应性强,木材纤维含量4551%～6192%,纤维长度达44～6.5ｍｍ(周政贤等,1989),是造纸工业原料林发展的主要树种之一。但由于湖北省本地种源的马尾松在干形、材性、速生丰产性、耐瘠薄和抗病虫害等方面均不如南方种源的高州马尾松(李传志,1983),因而湖北及其它省市已从广东大量引种高州马尾松。为更好地掌握高州马尾松的生长规律,确定其造纸工业原料林的合理密度和经营管理措施,笔者对高密度高州马尾松纸浆原料林对不同间伐强度的生长反应进行了试验研究。1　试验地点与材料高州马尾松…     

Effect of thinning intensity on tree growth and temporal variation of seed and cone production in a Pinus koraiensis plantation

Thinning of Korean pine (Pinus koraiensis Sieb. et Zucc.) is used to facilitate timber and cone production. The present study in Northeast China investigated the effects of thinning intensity on individual tree growth, temporal variation in cone yield, and seed quality in Korean pine plantation. In 2005, five thinning intensity levels (none, extreme, heavy, moderate and light) were set in 15 permanent plots in a 32-year-old Korean pine plantation at Mengjiagang Forest Farm, Jiamusi City, Heilongjiang Province. We recorded tree growth and seed cone production from 2013 to 2016, i.e., from 8 to 11 years after thinning. Except for height growth, thinning increased tree growth (diameter at breast height and crown size) and improved cone yield. The extreme thinning treatment (to 300 trees per hectare) resulted in the largest tree diameter, tree volume, crown size and 4-year cone production per tree. The highest cone yield per tree in the mast year (2014) was observed when stands were thinned to 500 trees per hectare (heavy thinning). Although the best cone and seed quality and the largest cone and seed mass per tree were recorded in the heavily thinned stand, no significant differences were found between heavy and moderate thinning stands (750 trees per hectare). At the stand level, the moderately thinned stand had the highest basal area, stock volume and seed cone production per stand. Our results suggest that thinning to 750 trees per hectare will improve timber and cone productivity in 40-year-old P. koraiensis stands.     

Growth and structure development of semi-natural larch-spruce-fir (Larix olgensis–Picea jezoensis–Abies nephrolepis) forests in northeast China: 12-year results after thinning

Analyzing and understanding the structure and growth dynamics of semi-natural plantations is useful for their management. Since 1987, 16 plots with 4 treatments (CT: control; LT: light thinning; MT: medium thinning; and HT: heavy thinning) by 0, 20, 30 and 40% of basal area removal, respectively, and four replications were established in semi-natural larch-spruce-fir forests in northeast China. The structure and growth dynamics of semi-natural larch-spruce-fir stands and the effects of thinning on the growth, structure and diversity were examined. A mixed model repeated measures analysis of variance (RMANOVA) was used to test the effects of treatment and time.

Results showed that differences in periodic annual increment (PAI) of stand basal area and volume and the individual diameter and volume among treatments changed over time in a complex statistical interaction. Thinning, however, had a significant effect on growth at tree and stand levels 12 years after thinning while the PAI of the diameter, basal area and volume was positively correlated with thinning intensity. No significant differences were found in the total stand yield among treatments. Composition of tree species group (larch, other conifers and deciduous trees) during monitoring years did not change significantly. Moreover, no significant differences were observed in tree species and size diversity among treatments in the years following thinning. Both thinning and control plots had similar understory plant diversity after the 12 year period. Univariate point pattern analysis revealed that clumped and random distributions were dominant for tree species groups in this study. The current species composition and regeneration dynamics within these semi-natural plantations suggested a development towards mixed coniferous and broad-leaved forests. Management implications for the transformation from larch plantations towards mixed broad-leaved Korean forests with a more diverse structure, the climax vegetation in this region, were discussed.     

Spatially explicit assessment of carbon stocks of a managed forest area in eastern Germany

The Kyoto-protocol permits the accounting of changes in forest carbon stocks due to forestry. Therefore, forest owners are interested in a reproducible quantification of carbon stocks at the level of forest management units and the impact of management to these stocks or their changes. We calculated the carbon stocks in tree biomass and the organic layer including their uncertainties for several forest management units (Tharandt forest, Eastern Germany, 5,500 ha) spatially explicit at the scale of individual stands by using standard forest data sources. Additionally, soil carbon stocks along a catena were quantified. Finally, carbon stocks of spruce and beech dominated stands were compared and effects of thinning intensity and site conditions were assessed. We combined forest inventory and data of site conditions by using the spatial unions of the shapes (i.e., polygons) in the stand map and the site map. Area weighted means of carbon (C) stocks reached 10.0 kg/m2 in tree biomass, 3.0 kg/m2 in the organic layer and 7.3 kg/m2 in mineral soil. Spatially explicit error propagation yielded a precision of the relative error of carbon stocks at the total studied area of 1% for tree biomass, 45% for the organic layer, and 20% for mineral soil. Mature beech dominated stands at the Tharandt forest had higher tree biomass carbon stocks (13.4 kg/m2) and lower organic layer carbon stocks (1.8 kg/m2) compared to stands dominated by spruce (11.6, 3.0 kg/m2). The difference of tree biomass stocks was mainly due to differences in thinning intensity. The additional effect of site conditions on tree carbon stocks was very small. We conclude that the spatially explicit combination of stand scale inventory data with data on site conditions is suited to quantify carbon stocks in tree biomass and organic layer at operational scale.     

不同强度间伐对长白山天然林林下植物多样性的影响

对吉林森工集团松江河林业局辖区内的阔叶红松林、杂木林和杨桦林采取30%～40%（T1）、20%（T2）株数强度的均匀间伐处理,以不间伐处理为对照（CK）,对间伐2 a后林下植物木本、草本植物进行调查,采用Simpson、Shannon-Wiener多样性指数和Pielou均匀度指数进行植物多样性分析,探讨不同强度间伐对3个林型林下植物多样性的影响。研究结果表明：T1间伐后3个林型的物种丰富度均有增加（杂木林木本植物例外）,T2间伐后杨桦林木本植物丰富度降低,草本植物丰富度增加。两种间伐处理均增加阔叶红松林木本植物多样性,T1处理尤为明显。T1处理增加杂木林和杨桦林木本植物多样性,而T2间伐处理有较弱的降低作用。两种间伐处理均降低阔叶红松林和杂木林草本植物多样性,与强度无明显关系。随着间伐强度的增加杨桦林草本植物多样性增大。在长白山天然林中,较大间伐强度T1（30%～40%）能够有效提高植物多样性。     

Modelling the impacts of various thinning intensities on tree growth and survival in a mixed species eucalypt forest in central Gippsland,Victoria, Australia

The response of tree survival and diameter growth to thinning treatments was examined over 29 years, in various thinning treatments established in a 21-year-old even-aged mixed species regenerating forest in Victoria, Australia. The treatments were control, crown release, strip thinning and three different intensities of thinning from below (light, moderate, and heavy). Each treatment was replicated three times in a complete randomised design. Logistic and multilevel regression analyses showed that tree survival, growth and thinning response (change of tree growth due to a thinning treatment) were functions of tree species, size, age, removed and remaining competition, as well as time since the treatment. Mean annual tree diameter growth in unthinned stands was highest for Eucalyptus sieberi L. Johnson (1.9 mm) followed by Eucalyptus baxteri (Benth.) Maiden & Blakely ex J. Black (1.6 mm), and lowest for both Eucalyptus consideniana (Maiden) and Eucalyptus radiata (Sieber ex DC) combined (0.7 mm). Diameter growth increased with tree size for both E. sieberi and E. baxteri, but not for E. consideniana and E. radiata. Smaller trees were more likely to die due to shading and suppression than their larger counterparts. A mortality model suggested, however, that both shading and suppression had very little effect on trees in both E. consideniana and E. radiata species, which were less likely to die compared to trees in the other species. This result indicates that both E. consideniana and E. radiata species may be relatively shade tolerant compared with the other species. Total thinning response was a sum of positive (increased growing space) and negative (thinning stress) effects. Following thinning, smaller trees showed signs of thinning stress for the first one or two years, after which the highest percentage thinning response was observed. While larger trees were initially less responsive to thinning, the rate of decrease in the response for subsequent years was greater in smaller trees than larger ones. The average amount of thinning response showed similar trends to diameter growth increasing from E. sieberi (1.7 mm) through E. baxteri (0.6 mm) to both E. consideniana and E. radiata (0.5 mm). This translates into low average percentage thinning response in E. baxteri (34%), twice as much in both E. consideniana and E. radiata (69%) and highest overall percentage response in E. sieberi (87%). Thinning response and the duration of this response appeared to increase with thinning intensity and was still evident 29 years after thinning. Heavy thinning did, however, reduce the number of trees to a severely under-stocked condition, which prohibited optimum site occupancy, requiring 29 years of post-thinning development for the heavily thinned stands to regain their pre-thinning stand basal area.     

Impacts of thinning on structure,growth and risk of crown fire in a Pinus sylvestris L. plantation in northern Spain

We studied the combined effects of thinning on stand structure, growth, and fire risk for a Scots pine thinning trial in northern Spain 4 years following treatment. The thinning treatments were: no thinning, heavy thinning (32–46% of basal area removed) and very heavy thinning (51–57% of basal area removed). Thinning was achieved via a combination of systematic and selective methods by removing every seventh row of trees and then by cutting suppressed and subdominant trees in the remaining rows (i.e., thinning from below). Four years after thinning, mean values and probability density distributions of stand structural indices showed that the heavier the thinning, the stronger the tendency towards random tree spatial positions. Height and diameter differentiation were initially low for these plantations and decreased after the 4-year period in both control and thinned plots. Mark variograms indicated low spatial autocorrelation in tree diameters at short distances. Diameter increment was significantly correlated with the inter-tree competition indices, and also with the mean directional stand structural index. Two mixed models were proposed for estimating diameter increment using a spatial index based on basal area of larger trees (BALMOD) in one model versus spatial competition index by Bella in the other model. As well, a model to estimate canopy bulk density (CBD) was developed, as this variable is important for fire risk assessment. Both heavy and very heavy thinning resulted in a decrease of crown fire risk over no thinning, because of the reduction in CBD. However, thinning had no effect on the height to crown base and thus on the flame length for torching. Overall, although thinning did not increase size differentiation between trees in the short term, the increase in diameter increment following thinning and the reduction of crown fire risks support the use of thinning. Also, thinning is a necessary first step towards converting Scots pine plantations to more natural mixed broadleaved woodlands. In particular, the very heavy thinning treatment could be considered a first step towards conversion of overstocked stands.     

A simulation of the development and restoration of old-growth structural features in northern hardwoods

Thinning treatments in second-growth forest may be a practical means of accelerating the development of certain old-growth structural features in regions where old stands are presently uncommon. We used CANOPY, an individual-tree model calibrated with data from thinned and unthinned stands, to simulate effects of thinning on growth rates and development of old-growth structural features in second-growth northern hardwoods. Three simulated, moderately heavy thinnings over a period of 45 years nearly doubled the predicted mean radial increment of canopy trees, percent of stand basal area in large trees, and area of canopy gaps. Compared to untreated stands, thinned stands had fewer dead trees per ha, but the dead trees were larger in size and the overall volume of snags and logs was little affected. In a 77-year old even-aged stand, moderately heavy thinning was predicted to reduce the time needed to attain the minimum structural features of an old-growth forest from 79 to 36 years. Simulated treatments in an older, uneven-aged stand gave mixed results; the moderately heavy treatment stimulated individual tree growth, but the removal of some medium-sized canopy trees in conjunction with natural mortality delayed the development of old-growth structure. Total volume of dead wood may still be deficient under the thinning regimes investigated in this study, but predicted live-tree structure 45 years after moderately heavy thinning was typical of stands in the advanced transition and steady-state stages of old-growth development. Results suggest that thinning can substantially accelerate the development of old-growth structure in pole and mature northern hardwoods, but response in older, uneven-aged stands is more modest, and treatments in these stands may need to be more conservative to achieve restoration goals.     

Efficiently mapping an appropriate thinning schedule for optimum carbon sequestration: An application of multi-segment goal programming

Thinning is an important strategy for carbon sequestration in forest management. Linear programming (LP) and goal programming (GP) can only set fixed parameters for the left hand side constraints, which are incapable of simulating different thinning intensities at thinned stands to map an appropriate thinning schedule for optimum carbon sequestration efficiently. However, multi-segment goal programming (MSGP) with the flexibility to set multi-level parameters can be applied by forest managers to quickly choose an appropriate level from different thinning intensities.The purpose of this study was to combine MSGP with LP to efficiently adopt thinned area and thinning intensity together as decision variables. In a demonstrated case, an appropriate thinning schedule for three age-classes was chosen from 768 combinations of thinning intensity in just one step. Each age-class was allocated well such as practicing medium thinning intensity on young age-class and strong thinning intensity on the old age-class. Totally 1379643.03 tons of carbon sequestration was obtained after two planning horizons, which was 34.75% higher than no thinning. Besides, a stable supply of wood form thinning is made for carbon sequestration in each period and the stocking of each age-class is also improved.