川滇高山栎种群统计特征的海拔梯度变化

川滇高山栎广泛分布于横断山地区,属于亚高山硬叶栎林,是中国植被非常特殊的类型.种群统计是种群生态学研究的核心,主要研究种群在时间和空间上的数量变化规律.本文采用标准地法和样方收获法,对卧龙林区五个海拔梯度的川滇高山栎种群的大小结构、高度结构和生物量结构等方面探讨川滇高山栎种群的海拔梯度变异性规律.结果表明(1)川滇高山栎种群径级分布表现为两类,一类为海拔3000 m以下地带的双峰型,径级峰值出现在2 cm～4 cm,约占70.33%;另一类为海拔3000 m以上地带的单峰型,径级峰值出现在1 cm～3 cm,约占76.35%.(2)川滇高山栎种群高度级分布表现为两类,一类为海拔3000 m以下地带,高度级峰值出现在2 m～3 m左右,约占65.38%;另一类为海拔3000 m以上地带,随高度级增大,高度级百分率呈递减趋势.(3)川滇高山栎种群总生物量随海拔升高呈递减趋势,其平均总生物量为26 408.7 kg·hm-2,各器官平均生物量大小排序为干＞枝＞叶＞皮,其生物量占种群总生物量的百分率分别为29.85%、18.54%、18.54%和6.91%.海拔2 720 m～2 920 m地带川滇高山栎种群地上部分器官生物量,干枝叶1皮的比例约为4321;海拔3 020 m～3 120 m地带川滇高山栎种群地上部分器官生物量,干枝叶皮的比例约为4221.     

文县杨个体生物量生长规律研究

采用标准木法对文县杨地上部分生物量进行了调查,分析了地上部分各器官生物量与株高、胸径的相关关系,结果表明:文县杨地上部分生物量各器官的比例为树干56.12%、干皮7.8%、叶9.5%、枝21.4%、枝皮5.2%,其大小顺序依次为树干＞枝＞叶＞干皮＞枝皮;地上部分质量、树干质量、树皮质量、叶质量、枝质量等与株高和胸径均呈...     

海南沿海木麻黄人工林林下植被生物量

采用样地调查法,对海南沿海木麻黄人工林林下植被进行调查、并测定其生物量。结果表明:木麻黄人工林林下灌木层地上部分生物量大于地下部分生物量,草本层地下部分生物量大于地上部分生物量;灌木层各器官的生物量分配规律为干(3.41 t·hm-2)根(3.19 t·hm-2)叶(2.10 t·hm-2)枝(1.41 t·hm-2),干和根的生物量比例较大;灌木层、草本层生物量与总生物量均呈正相关关系,灌木层生物量与草本层生物量则呈负相关关系,说明灌木层与草本层存在竞争。     

巴郎山川滇高山栎群落植物科组成的海拔梯度特征

川滇高山栎林是中国植被非常特殊的亚高山硬叶栎林类型,广泛分布在横断山地区。为了阐明川滇高山栎群落植物科组成对海拔梯度的响应,用群落学调查方法研究了组成群落的植物科沿海拔梯度(15个海拔梯度,海拔2 200 m~3 600 m)的变化特征。研究结果表明:巴郎山川滇高山栎群落植物科的分布区类型,有世界分布31科、热带分布21科和温带分布21科,分别为占42.47%、28.77%和28.77%。川滇高山栎群落的植物科数具有低海拔比高海拔多的特点,在海拔3 100 m以上,分布的植物科数没有变化。在各个海拔梯度以世界分布科占主要地位,其次为热带分布科和温带分布科。热带分布科随海拔的升高具有递减的趋势,温带分布科随海拔的升高出现2个峰值。在海拔2 200 m~2 800 m范围,热带分布科和温带分布科相当,海拔2 900 m以上,温带分布科明显增多。     

巴朗山川滇高山栎群落水平结构的海拔梯度特征

采用标准地法对卧龙自然保护区4个海拔梯度川滇高山栎群落水平结构进行了研究,结果表明:(1)在各个海拔梯度上物种以川滇高山栎为主,其相对密度分别为61.40、65.67、77.21和62.27;随海拔升高伴生木本植物种类逐渐减少,从11种减少到3种.(2)有随海拔升高,川滇高山栎群落物种相对频度大于2.0以上的物种数量具有先升高后降低的趋势,川滇高山栎是各个梯度出现频度最大的物种.(3)川滇高山栎群落物种重要值大于5.0以上的物种数量具有随海拔升高先升高后降低的趋势,川滇高山栎在从低到高的4个海拔梯度上重要值分别为68.47、80.37、119.93和84.01.(4)林分平均树高和林分平均地径具有随海拔升高而降低的趋势,海拔每升高100 m树高和基径分别平均降低0.18 m和0.22 cm.(5)按株频度计算,在巴朗山阳坡各个海拔梯度的川滇高山栎种群多为聚集分布;而丛频度计算,在高海拔和低海拔地带川滇高山栎种群格局呈聚集分布,在中等海拔区域川滇高山栎种群格局呈随机分布或均匀分布.     

红豆树容器苗各器官生物量和水分分配规律研究

对不同高度等级2年生红豆树Ormosia hosiei容器苗各器官的生物量和水分分配规律进行研究。结果表明,处于不同高度时期各器官生物量和水分分配规律不同:(1)红豆树容器苗单株生物量及各器官生物量都随着高度的增加而增加,各器官生物量分配顺序从大到小依次为叶生物量根生物量干生物量枝生物量;根、干、枝、叶生物量分配随着高度的增加呈现一致增加的趋势;苗高与地径,苗高、地径与根、干、枝、叶生物量以及地上、地下和单株生物量都具有极显著相关关系(P0.01);(2)苗高在40～45 cm的红豆树根、干、叶和单株含水率均达到最大值,其中枝含水率在各器官含水率中最大,达到67.04%,而苗高在65～70 cm的根、干、叶及单株含水率均为最低值,但枝含水率却是在此高度的时候达到最大值;(3)根、干和单株含水率与各器官生物量呈极显著负相关(P0.01),枝含水率与各器官生物量呈不显著相关,叶含水率与根、干生物量呈现显著负相关(P0.05),与叶、单株生物量呈现极显著负相关(P0.01)。     

乐昌含笑造林试验及效果分析

对福建省邵武市桂林乡乐昌含笑人工林进行调查,结果表明:8年生乐昌含笑与杉木1∶1混交林的乐昌含笑和杉木胸径、树高年均生长量、单株材积及总蓄积量均大于各自纯林。不同坡位9年生乐昌含笑人工纯林的胸径、树高及蓄积生长量均以下坡林分为最高,表现为:下坡>中坡>上坡。8年生乐昌含笑和杉木人工纯林的平均木生物量分别为31.55 kg和33.74kg;乔木层生物量分别为41.73 t.hm-2和45.55 t.hm-2;地上部分生物量的比例分别为94.28%和96.85%,灌木层和草本层所占比例较少;乐昌含笑和杉木平均木生物量各器官的比例分别表现为:干>根>枝>叶>皮、干>根>叶>枝>皮。     

15年生香樟人工林的生物量及生产力

通过对湖南省黄丰桥国有林场广黄分场15年生香樟(Cinnamomum camphora)人工林进行调查,采用样方收获法对其生物量和生产力进行研究。结果表明:香樟单株生物量随着胸径的增长而增加,不同径阶单株植物的生物量差异明显,其生物量在各器官上分配为干材根蔸枝条叶干皮粗根中根细根。各器官生物量与测树因子D2H间存在密切关系,拟合的回归模型精度均为0.9以上。香樟乔木层平均生物量为183.19 t/hm~2,分配规律为干材根蔸枝条叶子干皮粗根中根细根;乔木层地上部分生物量为126.90 t/hm~2,地下部分生物量为56.29 t/hm~2,分别占乔木层生物量的69.27%、30.73%,且地上部分生物量是地下部分生物量的2.3倍。林分的平均生产力为14.00 t/(hm~2·a),表现出较高的生产力;其中乔木层为12.22 t/(hm~2·a),占林分总生产力的87.29%,林下植被层为1.78 t/(hm~2·a),占总生产力的12.71%;林分中生产力在各层中的分配规律大小依次为:乔木层灌草层凋落物层,分别占林分总生产力的87.29%、8.79%、3.93%。     

铁尾矿坝沙棘、桑树人工林生物量分配及根系分布研究

以铁尾矿区沙棘-桑树人工混交林为研究对象,对混交林内各层次、器官生物量以及生长期内沙棘、桑树根系分布状况进行了研究.结果表明:单位面积生物量比较为乔木层＞枯枝落叶层＞革本层.其中地被层凋落物生物量占到整个人工林总生物量的17.巧%,尚无灌木层.桑树、沙棘各器官单位面积生物量比较均为:根＞枝＞干＞叶.桑树单株生物量大于沙棘,但林分内沙棘密度高于桑树,因而单位面积沙棘生物量高于桑树.沙棘根冠比为0.72,桑树的根冠比为0.62.从单株根系生物量看,在0-40cm土层内桑树大于沙棘;40-80cm土层内沙棘大于桑树;80-100.m土层内桑树又高于沙棘.从根系分布密度来看,沙棘＜1mm细根主要分布在根桩附近0-60cm土层,60cm以下明显减少;桑树＜1mm细根在0-20cm土层内分布密度最大,20-80cm土层内较为均匀.在80.m以下才开始明显减少.桑树和沙棘存在协作与竞争共存的关系.     

三峡库区主要植被生物量与生产力分配特征

在调查104块样地的基础上,利用95株标准木的树干解析数据,选择主要生物量生长模型,对三峡库区主要植被生物量和生产力的分配规律进行研究.结果表明:1)在各树种生物量组成中,干材生物量最大,占总生物量的44.46%～63.07%,而皮、枝和根生物量比例间的大小关系因树种不同而有所差异;2)所有树种干生物量比例与枝和叶生物量比例存在显著的线性负相关,而枝和叶生物量之间存在明显的正相关,随着单株林木生物量增加,针叶树种干和皮生物量比例会随之增加,但枝、叶和根的生物量比例则有所下降;3)各林分生物量为75.38～191.82t·hm-2,乔木层(67.57～179.00 t·hm-2)>枯落物层(3.95～11.61 t·hm-2)>灌木层(2.40～8.35 t·hm-2),乔木层和枯落物层生物量低,有利于灌木层生物量的生长;4)各林分生产力为4.78～11.07 t·hm-2a-1,常绿阔叶林最高,柏木林最低,混交林的生产力高于纯林,其中针阔混交林的生产力又高于针叶混交林.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.     

Development of Pinus sylvestris Main Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.     

Tree planting for dryland salinity control in Australia

Dryland salinity is emerging as a major form of land and water degradation in southern Australia, particularly in Western Australia, South Australia and Victoria, and to a lesser extent in New South Wales, Tasmania and Queensland.Tree planting, in combination with other vegetation treatments, is regarded as a leading solution to dryland salinity. Research has now shown that planting trees can significantly lower groundwater tables, and thereby reverse the causal process of salinisation. Substantial progress has been made towards answering the basic questions of which species to grow, how to plant, where to plant, at what density and configuration to plant, and how much area to plant. The economic potential for commercial tree planting has given impetus to partial reforestation in higher rainfall (> 600 mm yr^–1) areas. Even so, serious constraints are apparent, relating primarily to cost, uncertainty and attitude. The future should bring increasing community input and control, technical refinement and gradual adoption, provided all aspects of the issue are well researched, relevant information is well communicated and programmes are well administered. Some specific requirements for future research are identified in this review.     

Effect of Cuttings on the Scenic Beauty of a Tree Stand

The opinions of 207 respondents on the visual effects of seven different cutting types were asked using a nine-point verbal scale ranging from ''worsens very much'' to ''improves very much''. Other estimates were obtained by letting the same respondents evaluate photographs of stands which had been treated with different cuttings. The direct questions gave results quite similar to the evaluations of photographs for all but young respondents, indicating that most respondents were able to imagine the effect of the treatment correctly. The results based on the evaluation of photographs indicated that the effect of regenerative cuttings is negative while the impact of thinnings is positive. After a few years of cutting the stand is already regarded as clearly more pleasant than immediately after the cutting. Natural regeneration with seed trees seems to be a way to avoid the very negative immediate impact of clear-felling, especially in the case of Scots pine. Women, young, urban people and those who do not own forest or have work related to forests tended to experience thinnings less positively and saw regenerative cuttings as more harmful than the other test groups did.     

Pinus contorta growth in northern Sweden as affected by soil scarification

The aim of this study was to quantify the effects of different soil scarification methods on tree growth. Soil scarification influenced stem volume and stem biomass yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in a 17-year-old field trial in boreal Sweden. Soil scarification (disc trenching, mounding and ploughing) resulted in an average stem volume yield of 3.1 and 34.2 m³ ha^–1 on the poor and intermediate sites, respectively, while corresponding values for no soil scarification were 0.9 and 16.7 m³ ha^–1. In comparison to no scarification, ploughing increased volume yields by 500% on the poor site and by 200% on the intermediate sites. The ranking according to stem volume yield was ploughing > disc trenching = mounding no soil scarification. Averaged over the two sites, the mean annual increment of stem biomass was 219% and 145% higher (in d.w., 0.26 kg and 0.34 kg per sample tree) after ploughing compared with no soil scarification, for the average and dominant sample trees, respectively. Although not significant, the increased growth rate after soil scarification decreased the average stem basic wood density of the sample trees with 1.6% and 5.3%, at the poor and intermediate sites, respectively. In conclusion, soil scarification significantly increased the 17-year stem volume yield compared with no scarification. The results also indicate that the difference in stem biomass yield between ploughing and the other methods, especially no soil scarification, will increase even more in the near future.