伐木联合机的现状及发展

介绍了国外伐木联合机的发展概况,并从几个方面论述了国外伐木联合机的特点及发展趋势.最后对我国伐木联合机的发展作出了展望.     

联营速生丰产林间伐作业和收益分成的调查研究

材料分析了联营速生丰产林间伐作业亏本的主要原因，阐述了按协议和按实物进行收益分成给林场林和社会产生的影响，就加快发展速生丰产林谈几点建议。     

抚育间伐初始时间的确定

本文从生物学角度论述了抚育间伐的开始时间，提出间伐初始时间按林分生量、 林分分化的程度、林分的外貌特征确定。     

日本落叶松人工林抚育间伐时间的研究

通过计算叶面积大小,并结合林分的离散度大小和连年生长量的下降年限对日本落叶松人工林的抚育间伐时间进行了研究,结果表明,日本落叶松首次间伐时间确定11年左右为宜。     

基于支撑弦和遥控伐木楔的链锯伐木技术

使用链锯进行伐木仍然是我们国家林业采伐的主要方式。链锯伐木过程中存在被树木砸伤和机械伤害2个主要安全问题,改进伐木技术、研究新型伐木工具是减少安全事故发生的主要办法。该文在传统链锯伐木方法的基础上,介绍了一种带支撑弦的伐木留弦方式和与之配套使用的遥控电动伐木楔,并提出了使用链锯进行安全生产的一些建议,希望为相关林业安全生产工作提供借鉴。     

青椆混交林间伐指数初探

提出"间伐指数"这一新概念来量化林木在抚育间伐中被确定为间伐木的概率,突破了传统方法中对间伐木确定笼统定性的局限。选取林木的自由度、混交度、大小比数、健康指数、空间密度指数和目的树种特性指数等6个指标,结合对象林分的经营类型,并运用层次分析法给各指标赋权重,可得出该林分林木间伐指数的计算模型。以湖南省沅江市龙虎山林场青椆混交林的一个试验样地为案例,采用"间伐指数"来确定间伐木,得到了较为理想的抚育间伐方案。     

速生桉树间伐技术探讨与间伐效果分析

根据速生桉树的生长特点 ,提出应进行间伐的观点 ,探讨间伐起始年龄、间伐强度、次数及间伐方法等技术要素 ,并分析间伐对树高、胸径、树冠、蓄积量、抗逆能力、经济效益的影响     

抚育间伐时间和伐根高度对阔叶树萌芽更新的影响

天然针阔叶幼龄林占林地面积较大。在此林中进行抚育间伐就能加速恢复针叶林,可是此时恰是营林工作大忙季节,劳力比较紧张,难以安排。面临这一矛盾只有采取降低阔叶树竞争能力的林学措施,才能实现针叶林分的更新。笔者认为采用抚育间伐技术是唯一有效的措施,但在抚育间伐时一定要掌握好间伐的不同时间和伐根高度。在混交幼龄林中阔叶树高度居林分的首位,而针叶     

作业环境微气候对伐木作业人员及作业效率的影响

本文从人类工效学的角度对作业环境微气候对伐木作业人员及作业效率的影响进行了理论分析和部分实例探讨。首先,作者对高温作业 环境的影响进行了热平衡分析和实例分析研究;其次,作者又对低温作业环境对作业人员及作业效率的影响进行了较深入的理论分析和实例探讨。结果表明,作业环境微气候对伐木作业效率有较为显著的影响。对北方林区而言,夏季高温环境(较正常环境)影响伐木作业效率幅度约为20％—30％,冬季低温影响幅度约为15％—25％。     

谈抚育间伐的目的和方法

文中对抚育间伐的目的进行了分析，并从有利于森林培育出发，提出了在抚育间伐作业中应执行的几点原则。     

森林间伐的效果

本论述了森林抚育间伐的效果,结果表明：森林经过抚育间伐后,促进了保留木的高生长和直径生长。     

抚育间伐对林分结构及群落演替的影响

通过对同龄单层林、同龄复层林、异龄复层林的抚育间伐试验，调整了林分结构，改善树处组成、加快群落的演替，达到集约经营的目的。     

水杉人工林抚育间伐的效果比较

在１５ａ生水杉人工林内设立标准地，定量机械间伐，定期测定生长量，对抚育间伐７ａ后的效果及经济效益进行分析，结果表明：（１）不同初植密度的林分采用较小的强度ｐｎ＝２５％，３３％进行间伐，与对照林分相比，平均每公顷生长量分别提高５．９７，９．２７ｍ３，增加９．５７％，１４．８７％；采用较大强度ｐｎ＝５０％进行间伐，与对照林分相比，平均每公顷生长量下降９．７ｍ３，减少１５．５７％。（２）抚育间伐过的林分（间伐强度ｐｎ＝２５％，３３％，５０％）与对照林分相比，单位面积保留木平均生长率分别提高１．３４％，２．００％，１．９７％。（３）抚育间伐的林分与对照林分相比，平均每公顷总产值和利润分别增加６２７８，５７８４元，增长７．７％，９．５％。     

Effects on stem growth of Scots pine 33 years after thinning and/or fertilization in northern Sweden

Thinning and fertilization are two common and important stand treatments in forest management. In terms of area treated, thinning is the single most common form of stand treatment. The extent of forest fertilization on the other hand, has varied widely in recent decades and is currently not very common. Thinning is done primarily to promote stand properties while fertilization is done to increase growth before future final felling. After thinning stands of Scots pine, overall growth decreases, while growth of residual trees increases. An experiment was established outside Vindeln in northern Sweden where the long-term growth effects after thinning and/or fertilization were evaluated after 33 years. Experimental set-up was a randomized block design including 12 replications of four treatments. Treatments were control, fertilization, thinning, and thinning and fertilization combined. Thinning decreased overall and annual volume growth ha^?1, and increased green crown size and diameter growth at breast height (1.3 m, DBH) for the individual trees. No positive growth responses to fertilization could be seen after 33 years. In summary, this study showed that thinning can have long term effects on the growth of a Scots pine stand in northern Sweden. Possible reasons for the lack of positive response following fertilization are discussed.     

间伐对侧柏人工林土壤微生物生物量碳、氮的影响

以徐州侧柏人工林为对象,研究了在弱度间伐（LIT,20％）、轻中度间伐（MIT1,40％）、中度间伐（MIT2,60％）和强度间伐（HIT,80％）下,林下土壤微生物生物量碳、氮在土壤表层（0 ～ 10 cm）和亚表层（10～20 cm）的变化.结果表明：不同间伐强度下,微生物生物量碳、氮含量均随着土层加深而减少.随着间伐强度增加,微生物生物量碳、氮总体变化趋势为先增加后降低,其中微生物生物量碳表现为MITl＞ LIT＞ HIT＞ MIT2,均与对照CK有显著差异（P＜0.05）;微生物生物量氮表现为MIT2＞ MITl＞ LIT＞ HIT,各处理间均表现出显著差异（P＜0.05）.间伐也使土壤微生物熵增加,尤以MIT2达到最大（2.63％）.研究表明,侧柏人工林经过2 a间伐,土壤微生物生物量碳、氮含量增加,在一定程度上使土壤碳库和氮库短期内出现不稳定趋势.     

Performance of small harvester head in a thinning operation

Medium to large size harvester heads mounted on large machines are popular in Japan. These machines encounter some problems during thinning operations,e.g. damage to residual stand and the compaction of soil. The performance of these large harvesters was compared with that of smaller ones operating simultaneously in the same line thinning operation of the same stand. The results of a time study showed that mean cycle times for the smaller and larger harvesters were not significantly different. This means that the work efficiency of the smaller harvester can be at the same level as the larger harvester on sites similar to those of this study. The mean values “Feed” element of the cycle time, however, were significantly different. Although this time difference appears to provide an advantage to the larger harvester, simulation results show that the advantage is not great enough to significantly shorten the total cycle times. That is to say, the work efficiency remains essentially the same even if the feeding performance of the small size harvester becomes as high as that of larger ones. The small harvester performs adequately in thinning operations, and is not inferior to the larger ones. This result indicates that there is economic potential for small base machines that can be mounted with small harvester heads, resulting in less damage to residual trees and site soils during thinning operation. A part of this paper was orally presented at the 109th Annual Meeting of the Japanese Forestry Society (1998). The time study research presented in this paper was supported by the National Federation of Logging Contractors Cooperative Associations.     

The effects of thinning and burning treatments on within-canopy variation of leaf traits in hardwood forests of southern Ohio

Leaf nitrogen content (N_mass, %) and leaf mass per area (LMA, g m⁻²) are two important features that are closely linked to the photosynthetic performance of plants and, thus, the NPP of forest ecosystems. Forest management practices, such as burning and thinning, change stand structure and soil dynamics, which may result in changes in N_mass and LMA. The objective of this study was to understand how N_mass and LMA of seven canopy tree species/genus (Quercus alba, Q. coccinea, Q. prinus, Q. velutina, Carya spp., Acer rubrum, and Liriodendron tulipifera) responded to (i) thinning and/or burning treatments and to (ii) different landscape and soil properties in southern Ohio. We collected leaves from the top, and bottom, of five individuals of each taxa in each treatment unit. Leave traits (N_mass and LMA) were compared using analysis of variance followed by orthogonal contrasts. To further understand the factors that influence the canopy leaf traits, we used regression tree analysis (RTA) to examine how variations of LMA and N_mass were linked to thinning and/or burning treatments, soil, and landscape variables. Finally, we assessed the potential ramifications of changes in these traits on canopy carbon budgets using a PnET-Day model, which is a daily time-step canopy carbon exchange model. We found significant effects of thinning, burning, and their interactions on LMA at the bottom of the crown while none of the treatments showed significant effects on LMA at the top of the crown. N_mass responded significantly to only burning treatment. RTA results exhibited minor effects of landscape features and soil properties on N_mass and LMA. Interspecific differences accounted for most variations of both leaf traits. Sensitivity analysis of PnET-Day model suggested these subcanopy changes in LMA increased the annual net primary production (NPP) by 8%. In summary, our results suggest that forest management can substantially influence canopy leaf traits such as N_mass and LMA and that alteration of these traits can influence forest NPP. Given the role of forests as global carbon sinks, the potential influence of thinning and burning on canopy traits, and thus NPP, is an important consideration for forest management.     

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.     

Compressive strength of young Taiwania (Taiwania cryptomerioides) trees grown with different thinning and pruning treatments

Taiwania (Taiwania cryptomerioides Hay) is an important timber species in Taiwan. Growth in generally improved trees under intense silvicultural practice is so rapid that rotations or the practice of thinning trees may be as short as 20–30 years. Thus, the wood properties of young plantation trees need to be characterized to effectively use this resource. The effects of different thinning and pruning methods on the compressive strength parallel to grain of young Taiwania trees were explored. Average compressive strengths with various thinning treatments revealed the trend of no thinning > medium thinning > heavy thinning and in the pruning treatments showed the trend of medium pruning > no pruning > heavy pruning. However, most results showed no statistically significant differences among thinning and pruning treatments.