覆盖对毛竹林土壤养分、酶活性及微生物群落的影响

【目的】为退化毛竹林土壤的修复和质量提升提供参考。【方法】以覆盖1 a、覆盖2 a、覆盖3 a、覆盖后恢复2 a、覆盖后恢复5 a及未覆盖的毛竹林地土壤为研究对象，测定土壤脲酶、酸性磷酸酶及过氧化氢酶等土壤酶活性指标，测定土壤有机质、全氮、碱解氮、全磷、速效磷、全钾及速效钾等土壤养分含量及土壤pH值，采用高通量测序技术测定土壤微生物群落组成及多样性，探讨土壤细菌、真菌变化特征及其与土壤养分含量、酶活性的相关性。【结果】覆盖3 a的毛竹林土壤脲酶、酸性磷酸酶活性均低于其他林地类型，覆盖后恢复5 a的0～20 cm土层酶活性均较高。样地土壤细菌类群中酸杆菌门、绿弯菌门、变形菌门、放线菌门为优势菌群，真菌类群中子囊菌门、担子菌门、球囊菌门所占比例较高。覆盖后恢复5 a的40～60 cm土层细菌和真菌的OUT数量较少，Chao1、Simpson及PD-whole tree指数均较小，表明覆盖后林地深层土壤微生物的数量及多样性均受到影响，土壤退化程度较高且恢复缓慢。土壤环境因子对毛竹林土壤细菌门水平的贡献度由高到低排序依次为酸性磷酸酶活性、过氧化氢酶活性、脲酶活性、碱解氮含量、有机质含量、全氮含...     

农林复合杨树土壤微生物的根际效应

对农林复合中杨树+留兰香、杨树+小麦、杨树+红薯和杨树纯林4种林地土壤微生物、杨树和间作物根际土壤微生物及根际效应进行了测定和分析。结果发现:与对照相比,间作显著增加了林地非根际和根际土壤微生物数量,尤其在杨树根际土壤中变化较大且无规律性,杨树+留兰香林地杨树根际土壤放线菌、氨化细菌数量最大,杨树+小麦林地杨树根际土壤好气性自生固氮菌、亚硝酸细菌数量最大,杨树+红薯林地杨树根际土壤真菌、纤维素分解菌数量最大;无论在间作林地还是杨树纯林,杨树具有较强的土壤微生物根际效应,其根际效应R/S值均大于1;但间作对其影响较大,土壤放线菌和亚硝酸细菌根际效应R/S值增大,土壤真菌、纤维素分解菌根际效应R/S值减小;土壤好气性固氮菌和氨化细菌因间作物不同而异。对于间作物来言,留兰香根际具有较强的吸引土壤微生物的能力和根际效应,留兰香根际土壤真菌、纤维素分解菌、氨化细菌、亚硝酸细菌数量和际效应R/S值均大于小麦和红薯,且留兰香的真菌、纤维素分解菌和亚硝酸细菌的根际效应R/S值均大于杨树。     

高山栎天然林土壤有机质及酶活性的通径分析

为探究高山栎天然林土壤生物学特性对土壤养分的影响,运用通径分析法,研究了云南省玉溪市磨盘山国家森林公园内的高山栎天然林土壤养分与土壤酶活性、微生物数量之间的关系。结果表明,土壤脲酶、过氧化氢酶、转化酶活性及细菌、放线菌、真菌、微生物总数量都是随着土层深度增加逐渐减小;影响土壤p H值的重要因素是脲酶、过氧化氢酶、转化酶活性与真菌数量;影响有机质、全氮、速效磷的重要因素是脲酶、过氧化氢酶、转化酶;影响土壤碱解氮的主要因子是脲酶、过氧化氢酶、真菌数量。总的来说,高山栎天然林土壤养分受土壤酶活性影响较大,受微生物数量影响较小。     

间作草木犀对杨树林地土壤及林分生长的影响

为探明杨树人工林间作草木犀对土壤及林分的影响，在4年生杨树人工林内间作草木犀，草木犀收获后测定土壤养分含量和杨树生长指标。结果表明：间作草木犀后，林地土壤养分得到改善，全氮、碱解氮、全磷、有效磷和有机质含量分别增加了29.89%、129.24%、51.35%、154.1%和28.05%；促进了杨树生长，树高、胸径分别提高了12.61%和15.96%。杨树-草木犀复合经营是一种林农间作新模式，可充分利用杨树林下空间资源，解决杨树人工林林地产出低、地力衰退等问题。     

桉树人工林地土壤微生物类群的生态分布规律

为了探讨湘南丘陵低山区桉树林地土壤肥力综合评价方法,研究了资兴市桉树人工林地土壤微生物数量及其类群分布规律.结果表明:资兴市桉树人工林地土壤微生物数量主要集中在0～20 cm的土层中,随土层加深,其数量迅速减少;在深度为0～70 cm的土层中,同一类群的微生物数量变动范围较大,其中好气性细菌为3.09×105～6.58×105个.g-1,真菌为4.43×104～3.53×106个.g-1,放线菌为7.50×102～1.60×103个.g-1,厌气性细菌为4.73×103～6.09×104个.g-1,自生固氮菌为2.50×10～6.00×102个.g-1;资兴市林科所桉树人工林林地微生物数量最多,其总数达4.01×106个.g-1;好气性细菌和固氮菌与速效氮呈极显著相关,厌气性细菌与速效钾呈显著相关,固氮菌也与速率磷有显著相关关系,真菌与速效钾有一定程度的负相关,钙元素对土壤微生物活动有一定的抑制作用.     

杉木林下植被对5～15cm土壤性质的改良

对江西大岗山山下林场杉木人工林５～１５ｃｍ土壤性质研究结果表明：土壤中细菌、放线菌、真菌数量，细菌中芽孢杆菌、放线菌中灰色菌丝群以及真菌中的曲霉和木霉数量，随林下植被盖度的增大而提高。土壤酶活性强度、腐殖质各组分Ｃ的含量，在１６和１８地位指数级样地，随林下植被盖度增大而提高，１４地位指数级相反，在１６地位指数级土壤有机质、速效Ｎ、交换性盐基总量，以及１８地位指数级土壤有机质、全Ｎ、速效Ｎ、Ｐ、Ｋ、Ｍｇ＋＋和Ｃａ＋＋含量，均随林下植被盖度的增大而提高。     

胶东丘陵区赤松人工林土壤生物学特性研究初探

以胶东丘陵区12块典型赤松人工林样地为对象,通过野外调查和室内分析,初步研究了不同林龄赤松人工林的土壤生物学特性。结果表明:土壤微生物数量和脲酶活性在供试赤松林地间均为强变异水平,而其它指标属于中等变异。不同林龄赤松人工林的土壤生物学指标间均存在较大差异;林龄较大时土壤生物学特性整体表现较好。不同土壤生物学指标间表现出各异的相关性,土壤细菌、放线菌、真菌、脲酶中任意两者之间存在极显著正相关,而它们均与过氧化氢酶活性存在显著负相关。     

生草栽培对油茶林地土壤养分特征和微生物及酶活性的影响

油茶林地夏季高温干旱,土壤板结,生草是一种有效的解决方式。为了探讨生草对油茶林地土壤特征的影响情况,选择人工种植的百喜草和自然生长的马唐草为研究对象,对比分析了不同草种生草区生草根际和油茶根际土壤酶活性、土壤养分、有机质含量、土壤微生物数量和土壤p H值的差异性特征。结果表明:(1)生草区根际土壤酶活性显著高于非根际土壤,微生物数量也高于非根际土壤;(2)土壤养分含量,根际区土壤有机质、有效P、有效K、有效N含量均显著高于非根际区(P0.05),根际区全N、全P、全K含量均高于非根际区,但其含量差异不显著,p H值的变化也不明显;(3)有机质、全N、有效N、有效P含量与脲酶、蔗糖酶活性间均呈显著正相关,有效K含量与过氧化氢酶、酸性磷酸酶活性间呈显著正相关,有效P含量与土壤细菌、真菌、放线菌间均呈极显著正相关,有机质含量与土壤细菌、真菌间均呈极显著正相关,土壤脲酶与细菌和放线菌间均呈正相关,蔗糖酶与细菌间呈正相关;(4)生草对土壤养分、有机质均有较大的积累和转化作用,土壤酶脲酶、蔗糖酶活性和微生物数量均表现为根际区非根际区;从土壤肥力的综合水平来看,百喜草马唐草对照,百喜草可以作为油茶林地生草草种推荐使用。     

微生物改良剂对花椒经济林土壤修复和改良

对武都地区种植的花椒经济林土壤施用新一代绿色环保型"微生物改良剂",测定了施肥前后花椒林地土壤养分理化指标和土壤微生物数量,研究其对花椒经济林土壤的修复效果。结果表明,施用微生物改良剂后,土壤的pH值呈现下降趋势,比施肥前的对照组下降了6.7%;土壤碱解氮、速效磷、速效钾、全氮、全磷、全钾、有机质等土壤理化指标明显增加;土壤细菌、放线菌和真菌的数量均有显著的增加。     

不同林分改造模式对土壤酶活性及微生物数量的影响

以广东省佛山市南海区的4种宫胁法改造林地、传统法改造林地和不进行林分改造的对照样地为研究对象,对不同样地的土壤酶活性和土壤微生物数量进行研究,以探讨不同林分改造类型的土壤生物学特性。结果显示:不同林分改造类型的林地土壤酶活性差异显著,其中宫胁法2和传统法林地土壤酶活性显著高于其它改造类型,宫胁法2改造林地土壤脲酶、磷酸酶和过氧化氢酶活性均居最高水平,宫胁法3和宫胁法4最低;不同的林分改造措施土壤微生物各生理类群的数量差异显著,但均表现为细菌数量最多,放线菌次之,真菌最少;各改造类型中,宫胁法2在土壤细菌、真菌、放线菌数量和微生物总量中均表现最高,宫胁法1在细菌、真菌和微生物总量均表现最低,说明宫胁法2在增加土壤微生物数量上表现最为显著。因此,宫胁法2最有利于改善土壤生物学特性,从而能创造植被恢复过程中良好的微生态环境。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

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.     

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.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。