长期排水造林对云贵高原亚热带泥炭藓沼泽土壤理化性质的影响

探究排水造林对亚热带泥炭藓沼泽土壤理化性质的影响，为科学保护与恢复该类型湿地提供理论基础。选择贵州娘娘山湿地天然泥炭藓沼泽为对照样地，选择经立地条件相似的泥炭藓沼泽排水造林20年形成的柳杉林为处理样地，比较二者表层(0～10cm)土壤理化性质的差异。主要结果：1)泥炭藓沼泽土壤总碳含量、总氮含量、pH、碳与磷质量比(C∶P)、氮与磷质量比(N∶P)、速效钾含量、硝态氮含量、铵态氮含量、土壤质量含水量显著高于柳杉林土壤相应的指标值(P<0.05);泥炭藓沼泽土壤容重显著低于柳杉林土壤容重；2)主成分分析显示，长期营造柳杉林后土壤理化性质总体已发生明显分异；3)土壤总碳含量与总氮含量呈极显著正相关(P<0.01),且二者与C∶P,N∶P,速效钾含量、硝态氮含量、质量含水量呈极显著正相关(P<0.01),与土壤容重呈极显著负相关(P<0.01),C∶P,N∶P,铵态氮含量、硝态氮含量、速效钾含量两两之间呈极显著正相关(P<0.01)或显著正相关(P<0.05);土壤质量含水量与容重呈极显著负相关(P<0.01)。总之，泥炭藓沼泽长期营造柳杉林后，表层...     

长岗山不同林分类型对土壤理化性质的影响

以广州市长岗山自然保护区中的湿地松林(Pinus elliottii)、桉树林(Eucalyptus urophylla)和木荷林(Schima superba)为研究对象,对比不同林分类型、不同土壤层次下的土壤理化性质.结果表明:(1)土壤容重和吸湿水含量表现为湿地松林>木荷林>桉树林,土壤自然含水量、全氮和速效钾含量表现为湿地松林>桉树林>木荷林,土壤pH、有机质和速效钾含量表现为桉树林>湿地松林>木荷林;(2)在不同林分类型0~60 cm土层下,土壤容重、自然含水量、有机质差异显著(P<0.05),土壤吸湿水含量、pH、全氮、速效磷、速效钾含量差异不显著;(3)不同土层深度、林分类型与土层深度交互作用下土壤理化性质无显著差异.     

广东省蕉岭长潭省级自然保护区表层土壤特性的研究

通过对广东省蕉岭长潭省级自然保护区针阔混交林、马尾松林、杉木林、毛竹林、阔叶混交林等5种不同森林类型土壤理化性质状况的比较,研究了不同森林类型对土壤肥力状况的影响。结果表明:(1)广东省蕉岭长潭省级自然保护区表层表土呈酸性,石砾含量、土壤容重、总孔隙度、毛管孔隙度和非毛管孔隙度分别为4.0%、1.11 g/cm3、58.01%、37.73%和20.28%;自然含水量、最大持水量、最小持水量分别为296.02,442.95,321.38 g/kg;土壤阳离子交换量为5.99~8.20 cmol(+)/kg,电导率为57.87~97.44,全氮、碱解氮、全磷、速效磷和速效钾分别为1.88 g/kg、105.20 mg/kg、0.19 g/kg、2.22 mg/kg和130.53 mg/kg。(2)土壤孔隙度、土壤自然含水量、最小持水量、阳离子交换量、电导率、全磷、速效磷在不同林分类型间差异不显著,但土壤容重、石砾含量、最大持水量、土壤pH值、全氮、碱解氮、速效钾在不同林分类型间差异显著。马尾松林的石砾含量与针阔混交林、毛竹林、阔叶混交林有显著差异(p=0.003,p=0.009,p=0.01),全氮与针阔混交林差异显著(p=0.025),碱解氮与针阔混交林差异显著(p=0.028),速效钾与阔叶混交林差异显著(p=0.012);毛竹林pH值和杉木林、针阔混交林和阔叶混交林差异显著(p=0.026,p=0.030,p=0.035)。(3)从土壤理化性状来看,阔叶混交林、毛竹林的土壤质量和肥力要比马尾松林和杉木林好。     

不同龄组南酸枣根际与非根际土壤养分特征研究

对不同龄组南酸枣根际与非根际土壤全氮、全磷、水解氮、有效磷、全钾、速效钾含量差异进行研究,探明南酸枣根际养分的差异及对土壤养分的利用情况,为培育南酸枣提供参考依据。结果表明:1)3年生南酸枣根际与非根际土之间仅全氮含量存在显著性差异,15年生南酸枣与30年生南酸枣根际与非根际土之间全氮、全磷、水解氮、有效磷、全钾、速效钾含量均存在显著性差异。2)3年生南酸枣根际土壤仅全氮存在富集作用,15年生南酸枣与30年生南酸枣根际土壤全氮、全磷、水解氮、有效磷、全钾、速效钾均存在富集作用。3)根际全氮与水解氮、全磷呈极显著正相关(P 0.01);全氮与全钾呈显著正相关(P 0.05),全磷与有效磷、全钾呈极显著正相关(P 0.01),全钾与速效钾呈显著正相关(P 0.05)。非根际全氮与全钾呈极显著正相关(P 0.01);全氮与水解氮呈显著正相关(P 0.05),水解氮与速效钾呈显著正相关(P 0.05),全钾与速效钾呈显著正相关(P 0.05)。随着树龄与胸径的增加,南酸枣根际效应更加明显,个体间根际土壤的差异性也越大;根际土壤的全氮、全磷、全钾含量是相互影响的,三者同时增加或降低。     

长沙市城乡交错带4种人工林土壤养分及其相关性研究

以长沙市城乡交错带4种人工林为研究对象,对各林分林下土壤理化性质进行比较分析,揭示了土壤养分间的相互关系,结果表明:土壤物理性质指标垂直分布规律明显,同一林分内土壤容重基本上随土层深度增加而增大,毛管孔隙度、总孔隙度和自然含水率相反;土壤容重与毛管孔隙度、总孔隙度呈极显著的负相关(P<0.01),与自然含水率呈显著的负相关(P<0.05);毛管孔隙度与总孔隙度呈极显著的正相关(r=0.943,P<0.01);自然含水率与总孔隙度呈显著正相关(P<0.05),与毛管孔隙度呈极显著正相关(r=0.815,P<0.01);各林分内不同土层土壤各化学性质指标垂直分布规律明显,基本上随土层深度增加而减小;土壤pH值与土壤养分因子的相关系数值均为负数,与速效氮含量显著负相关(r=-0.661,P<0.05),土壤有机质与全氮、全磷、全钾、速效钾含量相关性显著(P<0.05),与速效氮呈极显著正相关(r=0.760,P<0.01);土壤全量养分与有效养分间均呈显著的正相关。     

乌拉山自然保护区不同林分类型的土壤特征

以乌拉山自然保护区7种林分类型为研究对象,在白桦林、蒙古扁桃林、油松林和草地设置7块样地,从0~10 cm、10~20 cm、20~40 cm和40~60 cm土层取样,测定其物理和化学性状,探讨了研究区不同林分类型的土壤特征。结果表明,土壤物理性状(土壤容重、含水量与最大持水量)具有明显的分层特征,土壤容重表层最低,随土层加深逐渐增加;土壤含水量、最大持水量则表层最高,随土层加深逐渐降低,样地间物理性状具有显著差异。土壤有机质含量与土壤容重呈极显著负相关关系(r=-0.843**),而与土壤含水量(r=0.714**)、最大持水量(r=0.713**)呈极显著正相关关系,不同林分类型通过凋落物的组成和产量影响土壤有机质含量从而间接影响土壤的物理性状。土壤化学性状中有机质及全N含量具有明显分层现象,表现出随土层加深而降低的趋势,而土壤全P含量及p H值各土层无显著差异。各样地土壤有机质含量与全N含量具有极显著正相关性(r=0.817**);群落结构及其动态变化与土壤有机质及全N含量具有显著关系。该地区不同林分类型之间的土壤——植被协同反馈机制主要由土壤有机质含量调控。     

三峡水库岸坡系统不同用地类型对土壤酶活性和土壤化学性质的影响

以三峡水库岸坡系统常见的5种不同土地利用类型(林地、草地、退耕地、耕地、消落带)为对象,研究不同用地类型下土壤酶活性、土壤化学性质及其二者之间的关系。结果表明:林地土壤的过氧化氢酶、脲酶、碱性磷酸酶的活性在所有用地类型中最低,这与耕地土壤中的蔗糖酶、蛋白酶活性最低形成鲜明对照。与之相反,退耕地土壤中的脲酶、蛋白酶活性最高,而草地中的蔗糖酶、碱性磷酸酶活性居于最高。相关性分析表明:土壤过氧化氢酶、碱性磷酸酶活性与全氮、速效氮、全磷、有机质含量以及pH值分别呈现极显著的正相关,但碱性磷酸酶活性与速效磷含量呈现出极显著的负相关。蔗糖酶和脲酶活性则与全氮、速效氮、速效磷、pH值也呈显著的相关性。脲酶与有机质含量之间、蛋白酶与全氮、速效氮、pH值之间均分别呈显著相关性。林地土壤的全氮、速效氮、全磷、速效磷含量在几种用地类型中居于最低,岸坡林地能够有效减少可能进入三峡库区水体的N,P含量。消落带土壤中的速效氮、速效磷以及全磷含量在所有用地类型中最高,消落带的人为耕作可能是加剧水库水体N,P元素富营养化的重要来源之一。建议在三峡库区进一步增加林地,限制在消落带进行耕作等农事活动。     

广东省蕉岭长潭省级自然保护区表层土壤物性的研究

通过对广东省蕉岭长潭省级自然保护区针阔混交林、马尾松林、杉木林、毛竹林、阔叶混交林等5种不同森林类型土壤理化性质状况的比较,研究了不同森林类型对土壤肥力状况的影响。结果表明：（1）广东省蕉岭长潭省级自然保护区表层表土呈酸性,石砾含量、土壤容重、总孔隙度、毛管孔隙度和非毛管孔隙度分别为4.0%、1.11 g/cm3、58.01%、37.73%和20.28%;自然含水量、最大持水量、最小持水量分别为296.02,442.95,321.38 g/kg;土壤阳离子交换量为5.99-8.20 cmol（＋）/kg,电导率为57.87-97.44,全氮、碱解氮、全磷、速效磷和速效钾分别为1.88 g/kg、105.20 mg/kg、0.19 g/kg、2.22 mg/kg和130.53 mg/kg。（2）土壤孔隙度、土壤自然含水量、最小持水量、阳离子交换量、电导率、全磷、速效磷在不同林分类型间差异不显著,但土壤容重、石砾含量、最大持水量、土壤pH值、全氮、碱解氮、速效钾在不同林分类型间差异显著。马尾松林的石砾含量与针阔混交林、毛竹林、阔叶混交林有显著差异（p=0.003,p=0.009,p=0.01）,全氮与针阔混交林差异显著（p=0.025）,碱解氮与针阔混交林差异显著（p=0.028）,速效钾与阔叶混交林差异显著（p=0.012）;毛竹林pH值和杉木林、针阔混交林和阔叶混交林差异显著（p=0.026,p=0.030,p=0.035）。（3）从土壤理化性状来看,阔叶混交林、毛竹林的土壤质量和肥力要比马尾松林和杉木林好。     

西安植物园新建城市绿地土壤肥力综合评价

为了研究城市新建绿地土壤的肥力状况,以典型新建绿地西安植物园新区为研究对象,结合内梅罗公式,选用容重、饱和导水率、有机质、速效氮、速效磷、速效钾、阳离子交换量、pH八个指标作为土壤肥力影响因子对不同干扰状况下城市新建绿地的土壤进行综合肥力评价,研究各因子对肥力的影响力。结果显示:作为城市新建绿化用地,西安植物园新区的土壤综合肥力水平较差,有机质(0.94%)、速效氮(8.26mg·kg~(-1))、速效磷(8.43mg·kg~(-1))含量极低;土壤偏弱碱性(pH值为7.85);速效钾含量(115.5mg·kg~(-1))适中;土壤容重(1.51g·cm~(-3))过高,饱和导水率(20.87mm·h~(-1))过低,不同区域差异显著;不同因子对城市绿化用地土壤综合肥力指数的影响力土壤的饱和导水率容重速效氮有机质速效钾阳离子交换量速效磷pH值。     

文峪河上游河岸林与相邻高地林土壤属性比较分析

以文峪河上游河岸林为例,分析了河岸林与相邻高地林林下土壤的理化性质。研究结果显示,河岸林土壤含水量、速效磷和速效钾含量均高于相邻高地林;河岸林土壤有机质和全氮含量低于相邻高地林。不同类型河岸林和相邻高地林土壤含水量差异均达到极显著,土壤有机质含量均差异显著,土壤酸碱度差异均不显著。河岸林与相邻高地林土壤全氮和有机质含量呈极显著正相关(r=0.946 4)。土壤含水量、速效磷和速效钾含量在不同林型河岸林和高地林下的分布格局不同。     

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.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

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.