Effects of thinning on wind damage in Pinus thunbergii plantation ——Based on theoretlcal derlvation of risk—ratios for assessing wind damage

Based on paper of “Theoretical derivation of risk-ratios for assessing wind damage in coastal forest“,wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investigated for four successive growing seasons.Besides wind damage,the wind profiles outside and inside the coastal forest stand and the distributions of optical stratification porosity (OSP) were also observed.Based on these data,risk-ratios of wind damage for both individual trees and stands were estimated according to the methods developed in “Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest“.The results showed that risk-ratios of wind damage,which were calculated from the meen height and diameter only and from the combination of wind and stand sructure profiles,accurately predicted wind damage in the plantation.Relationships between different thinning ratios and incidence of wind damage showed that stand stability decreased soon after the thinning.This was due to the immediate effects of thinning on increasing the canopy roughness and wind load,and on decreasing the sheltering effects from surrounding trees.However,thinning strategies could improve the stability by long-term effects on growthand development of trees against extreme wind.Only canopy damage was recorded during the experimental period,no stem damage was found,even though the maximum 10-min wind speed outside the coastal forest attained 30.2m s^-1.The results obtained in this study indicate that thinning is the most effective silvicultural strategy available for managing coastal forest despite the increased probability of wind damage soon after thinning.     

间伐对黑松海岸林风害的影响——基于风害危险率评价的理论推导

本文在“海岸林风害危险率评价的理论推导”(Journal of Forestry Research, 2002, 13(4))一文的基础上,对1997年12月经四种间伐处理的黑松海岸林进行了连续四个生长季的风害调查,同时,对黑松海岸林内与林外风速廓线和林分透光分层疏透度的分布也分别进行了观测。应用在这些观测数据,依据“海岸林风害危险率评价的理论推导”文中获得的风害危险率评价方法,对单株树木及林分的风害风险率进行了评估,结果表明,单独依据平均直径与结合风速廓线和林分结构的风害风险率,构成了评价海岸森林风害的重要指标。不同间伐强度和风害发生率之间的关系表明,在间伐初期林分的稳定性有所下降,这可能是由于林冠粗糙度和风负载的增加及周围树木的保护效应的减少而引起的。然而,经过一段时间后,间伐处理能够促进林分生长,从而提高了林分的稳定性和对强风的抵抗力。在本试验观察过程中只发现了强风对林冠的损害,而即使是在间伐海岸林外风速达到30.2 m·s-1的条件下,也没有发现风倒或风折。本次研究中获得的结果表明,尽管在间伐之初风害的概率增加了,但是,间伐作为一种最为有效的林分管理方法,可以成为保持海岸林健康、稳定的一种长期经营管理策略。图3表4参19。     

四川盆地日本落叶松林抚育间伐研究

本文选择四川盆地的川东北山地、川西南山地、川西高山峡谷区的日本落叶松幼龄林、中壮龄林、近熟林,对日本落叶松人工林的林分结构、郁闭度、密度、蓄积量、生产力等调查和树干解析分析,根据日本落叶松人工林胸径连年生长量下降时间的变化,林分郁闭度需要恢复的时间,自然稀疏规律的综合分析,提出抚育间伐技术,并对初植密度与日本落叶松人工林合理间伐的相关关系提出建议。     

杉木火力楠混交林疏伐效果试验

对不同立地条件下的杉木火力楠混交林进行疏伐试验,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境条件。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。对立地条件较好的两树种处于同一林层的混交林,可采用强度疏伐,即疏伐伴生木株数占总株数的45%;而对立地条件较差、主林木居第二林层的混交林,则以弱度至中度疏伐为宜,即疏伐株数占总株数的15%~30%。     

Influence of storm damage on the runoff generation in two sub-catchments of the Sperbelgraben, Swiss Emmental

The project “Lothar and Mountain Torrents” investigates the effect of storm-originated deforestation on the hydrology on three scales within the Sperbelgraben catchment (Swiss Prealps). This article focuses on runoff measurements during a 3-year period in two differently affected sub-catchments (≈2 ha) and on 2-year surface runoff measurements on smaller plots (50–110 m²). The link between these two scales and the results of irrigation experiments on 1 m² areas are interpreted using a detailed map of forest site types describing soil and vegetation characteristics. Plot results show that surface runoff is generated in two distinct ways. On the one hand, high amounts of saturation overland flow were observed on wet areas of gleyic soils. On the other hand, hardly any surface runoff was measured on Cambisols, with the exception of a short hydrophobic reaction at the beginning of storms occurring on areas with a thick organic litter layer (temporary Hortonian overland flow). On the long term, the lightly damaged sub-catchment (SC1) yields less runoff than the highly damaged one (SC2). This is confirmed when direct runoff volumes during flood events are considered. However, short and intensive showers surprisingly lead to higher discharge peaks in SC1. This occurrence is explained by different geomorphologic characteristics (mainly the channel density) and the spatial distribution of the moist to wet forest site types. Effects of deforestation and local soil compaction due to forest clearing remain small on both plot and sub-catchment scale.     

如何正确测定水泥标准稠度

本文提出按固定水量法测定水泥稠度时,造成错误的检测结果是因为,常把第一次加水所拌制的净浆当做标准净浆,同时提出了正确做法。     

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。     

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.     

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。     

抚育间伐对林木生长及其稳定性的影响

不论是在人工林还是天然林管理中,抚育间伐都是一种极为常见的育林手段,在林木生长过程中具有非常重要的作用.大量实践证明,抚育间伐不仅能提高林木生长质量还有利于生态环境的改善.基于此,立足抚育间伐概念解析,分析了抚育间伐对柳杉生长和稳定性的影响,阐述了现阶段我国抚育间伐存在的问题,并提出了抚育间伐建议,以期能够为林木经营提...     

用EL-5100计算器现地控制抚育强度

笔者采用EL-5100计算器进行抚育强度的计算,并对设计抚育强度和计算抚育强度进行了比较。通过建立回归方程,进行方差分析和几何解析,证实该计算方法的实用性和可行性。结果表明,该方法能够使外业调查在1 min~2 min的时间内现地控制抚育强度,为天然林保护工程快速确定抚育强度提供参考。     

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％。     

伐木联合机间伐作业性能和时间研究

本文介绍了伐木联合机间伐针叶林的时间研究过程和方法。通过欧洲赤松和落叶松的间伐试验、测量了单株作业时间和各动作时段比例。得到(?)SA250EVA型伐木联合机的生产能力为每小时57～68株或6.8～8.5m~3分析不树种、林木胸径及作业方式对伐木联合权作业性能的影响,作业评估表明,伐木联合机生产率高、工作条件舒适安全。对林木和林地捐伤小,适合在针叶林间伐中使用。     

杉木人工林不同间伐强度对林分生物量的影响

通过对 1 3年生不同地位级杉木林间伐强度试验结果表明 ,间伐强度对不同地位级杉木林的单株生物量生长影响达到显著差异 ,单株生物量则随间伐强度加大而增大 ,单位面积生物量则随间伐强度加大而减小。树干生物量随年龄加大比例上升 ,枝、叶生物量随年龄增加比例下降     

Forest management and carbon sequestration in wood products

Wood products are considered to contribute to the mitigation of carbon dioxide emissions. A critical gap in the life cycle of wood products is to transfer the raw timber from the forest to the processing wood industry and, thus, the primary wood products. Therefore, often rough estimates are used for this step to obtain total forestry carbon balances. The objectives of this study were (1) to examine the fate of timber harvested in Thuringian state forests (central Germany), representing a large, intensively managed forested region, and (2) to quantify carbon stocks and the lifetime of primary wood products made from this timber. The analyses were based on the amount and assortments of actually sold timber, and production parameters of the companies that bought and processed this timber. In addition, for coniferous stands of a selected Thuringian forest district, we calculated potential effects of management, as expressed by different thinning regimes on wood products and their lifetimes. Total annual timber sale of soft- and hardwoods from Thuringian state forests (195,000 ha) increased from about 136,893 t C (~0.7 t C ha⁻¹ year⁻¹) in 1996 to 280,194 t C (~1.4 t C ha⁻¹ year⁻¹) in 2005. About 47% of annual total timber harvest went into short-lived wood products with a mean residence time (MRT) < 25 years. Thirty-one per cent of the total harvest went into wood products with an MRT of 25–43 years, and only 22% was used as construction wood and glued wood, products with the longest MRT (50 years). The average MRT of carbon in harvested wood products was 20 years. Thinning from above throughout the rotation of spruce forests would lead to an average MRT in harvested wood products of about 23 years, thinning from below of about 18 years. A comparison of our calculations with estimates that resulted from the products module of the CO2FIX model (Nabuurs et al. 2001) demonstrates the influence of regional differences in forest management and wood processing industry on the lifetime of harvested wood products. To our knowledge, the present study provides for the first time real carbon inputs of a defined forest management unit to the wood product sector by linking data on raw timber production, timber sales and wood processing. With this new approach and using this data, it should be possible to substantially improve the net-carbon balance of the entire forestry sector.     

抚育间伐对杉木中幼龄人工林林分生长质量及效益的影响

杉木是江西主要速生用材树种之一。通过对吉水县万华山林场20 a生人工杉木林分进行不同抚育间伐措施处理后,调查分析其平均胸径、平均树高、材种出材量、经济效益等存在明显差异。科学适时抚育间伐,经2次抚育间伐的杉木林分,上述因子高于经1次抚育间伐和未经抚育间伐的杉木林分,说明了抚育间伐能有效提高林分质量及经济效益。     

Biotic injuries on conifer seedlings planted in forest understory environments

We investigated how partial overstory retention, understory vegetationmanagement, and protective Vexar^® tubing affected the frequency andseverityof biotic injuries in a two-storied stand underplanted with western redcedar(Thuja plicata Donn ex D. Don), Douglas-fir(Pseudotsuga menziesii (Mirb.) Franco, grand fir(Abies grandis (Dougl.) Lindl), and western hemlock(Tsuga heterophylla (Raf.) Sarg.). The most prevalentsource of damage was browsing by black-tailed deer (Odocoileushemionis columbiana); deer browsed over 74% of Douglas-fir and over36% of western redcedar seedlings one or more times over the four years of thisstudy. Neither the spatial pattern of thinning (even or uneven) nor the densityof residual overstory affected browsing frequency. Spraying subplots may haveslightly increased browsing frequency, but the resulting reduction of theadjacent understory vegetation increased the volume of all seedlings by 13%,whether or not they were browsed. Vexar^® tubing did not substantiallyaffectseedling survival, browsing damage frequency, or fourth-year volume. Greaterlevels of overstory retention reduced frequency of second flushing. Chafing bydeer and girdling by rodents and other small mammals began once seedlingssurpassed 1 m in height. Essentially all grand fir seedlingsexhibited a foliar fungus infection.