小兴安岭落叶松沼泽林土壤CO2,N2O和CH4的排放规律

采用静态箱-气相色谱法,研究小兴安岭兴安落叶松-油桦-修氏苔草沼泽林、兴安落叶松-油桦-笃斯越橘-藓类沼泽林和兴安落叶松-狭叶杜香-中位泥炭藓沼泽林生长季节土壤温室气体(CO2,N2O和CH4)排放通量的季节变化规律、季节排放量及其主控因素.结果表明:1)3种落叶松沼泽林土壤CO:排放通量均呈现夏季高(651.4～823.6 mg·m-2h-1)春秋季低(233.3～310.0 mg·m-2h-1)的单峰型季节变化,N2O排放通量(0.010～0.049,0.012～0.020和0.010～0.080 mg·m-2h-1)分别呈现夏季>春季>秋季,春季>夏季>秋季和秋季>春季>夏季的变化规律,CH4排放通量(-0.083～0.037,-0.122～0.078和-0.05～0.026 mg·m-2h-1)分别呈现春秋季排放、夏季吸收,春季排放、夏秋季吸收和春夏季排放、秋季吸收的交替式季节变化;2)表层土壤(0～30cm)温度是土壤CO2排放的主要影响因素,低水位与较高表层土壤温度是N2O排放的主要影响因素,水位是CH.排放的主要影响因素,高水位时土壤排放CH4,低水位时土壤吸收CH4;3)3种落叶松沼泽林土壤在生长季节均为CO2排放源(20.8～25.2 t·hm-2),且夏季为强排放源、春秋季为弱排放源,3者均为N2O排放源(0.192～1.128kg·hm-2),兴安落叶松-油桦-修氏苔草沼泽林为强排放源,另2者为弱排放源,兴安落叶松-油桦-修氏苔草沼泽林和兴安落叶松-油桦-笃斯越橘-藓类沼泽林土壤为CH4强吸收汇(1.152～1.200 kg·hm-2),兴安落叶松-狭叶杜香-中位泥炭藓沼泽林土壤为CH4弱排放源(0.168 kg·hm-2);4)兴安落叶松-油桦-修氏苔草沼泽林土壤温室气体CO2排放强度最高(25.4 t·hm-2),另2者相对较低(20.8～21.2 t·hm-2),但均以CO2排放占绝对优势地位(99.63%～99.93%),N2O和CH4排放占次要地位(0.19%～0.92%和0.02%～0.10%).     

阔叶红松林土壤CO2,N2O排放和CH4吸收的研究

为研究凋落物对CO2,N2O排放和CH4吸收的影响,从2002年9月3日到2003年10月30日,采用静态密闭箱技术对长白山阔叶红松林两种类型土壤生态系统的CO2,N2O和CH4的通量进行测定。两种土壤类型分别为表层有凋落物覆盖和没有凋落物覆盖。研究结果表明,凋落物对CO2,N2O和CH4通量有显著性影响(P<0.05)。有凋落物样地的CO2,N2O和CH4通量的日变化趋势和无凋落物样地中三种气体的日变化趋势相似,且CO2,N2O和CH4的日通量峰值都出现在18:00。有凋落物样地的CO2,N2O和CH4通量的季节变化趋势和无凋落物样地中三种气体的季节变化趋势也相似,但在一年之中,CO2和CH4的峰值出现在六月,N2O的峰值却出现在八月。研究结果还表明有凋落物样地CO2,N2O的日排放通量和年均排放通量明显大于无凋落物样地中两种气体的排放通量,但有凋落物样地的CH4日吸收通量和年均排放通量却小于无凋落物样地的CH4吸收通量。     

华南地区4种典型人工林土壤CO_2和CH_4通量研究

采用静态箱/气相色谱分析技术对中国科学院鹤山丘陵综合开放试验站尾叶桉纯林(Eucalyptus urophylla,EUp)、厚荚相思纯林(Acacia crassicarpa,ACp)、10个树种混交林(Tp)和30个树种混交林(THp)4种林型的土壤CO2和CH4排放通量进行了原位测定,研究纯林和混交林对土壤温室气体排放的影响。结果表明:4种林型土壤都是CO2的源,但对CH4而言,可能是源,也可能是汇。CO2和CH4排放通量季节波动幅度较大;4种林型土壤CO2和CH4通量在湿季均维持较高水平;峰值均出现在湿季,旱季则趋于降低,且相对稳定。由于EUp和ACp纯林土壤微生物碳(Microbial Biomass Carbon,MBC)比混交林高,导致Eup(130.67 mg.m-2.h-1)和Acp(134.65 mg.m-2.h-1)土壤CO2通量显著高于Tp(111.39 mg.m-2.h-1)和THp(108.53 mg.m-2.h-1)。在4种林型中,尾叶桉和厚荚相思对土壤NO3-N和NH4-N快速吸收,土壤CH4排放通量较低。土壤温度、湿度、MBC、NO3-N和NH4-N都是影响土壤CO2和CH4...     

泥河水库秋季水-气界面CO2通量日变化特征及影响因子分析

利用静态箱法对泥河水库秋季水-气界面二氧化碳通量值进行连续24h观测,对其变化趋势及影响因素加以分析。结果表明：泥河水库24h均为大气的源,其碳通量均值为24.53mg·m-2.h-1,呈现出双峰值特点。全天源的极大值出现在22∶00为35.57mg·m-2.h-1,源的极小值出现在10∶00为12.57mg·m-2.h-1。在秋季影响水库水-气界面碳通量变化的主要因素是温度、风速、溶解有机碳（DOC）和碱度。秋季泥河水库CO2排放量不是很大,但仍是大气二氧化碳的碳源之一。     

降水减少对红锥和马尾松温室气体排放的影响

为了揭示降水变化对森林土壤CO2、N2O、CH4通量的影响,本研究以南亚热带红锥和马尾松人工林为研究对象,设置穿透雨减少50%和不减雨(对照),2013—2015年开展野外降水控制实验,结果表明:穿透雨减少仅导致红锥雨季土壤CO2排放通量比对照显著增加了39.1%,而对红锥全年和旱季土壤CO2排放通量、以及红锥全年、旱季和雨季土壤N2O排放和CH4吸收通量均无影响。对马尾松而言,穿透雨减少对其全年、旱季和雨季土壤CO2排放、N2O排放和CH4吸收通量的影响均不显著。另外红锥土壤温室气体排放通量大于马尾松,在减雨处理下更加明显。相关分析表明,红锥和马尾松土壤CO2排放通量与5 cm土壤温度呈指数正相关,与5 cm土壤温、湿度呈二元线性正相关;红锥和马尾松土壤N2O排放通量与5 cm土壤温、湿度的线性关系不显著;红锥土壤CH4吸收通量与5 cm土壤湿度和5 cm土壤温、湿度呈显著的线性负相关,而马尾松土壤CH4吸收通量与5 cm土壤温、湿度的线性关系不显著。总之,短期降水减少可能导致红锥雨季土壤CO2排放显著增加,然而不会改变马尾松土壤CO2、N2O和CH4通量。未来降水减少可能扩大红锥和马尾松土壤温室气体排放通量的差异。     

森林细根生产和周转研究

随着近 2 0多年来对细根功能的深入认识和研究方法的发展 ,林分细根生物量、生产和周转及其与环境因子的关系成为森林生态学的研究热点之一 ,开展了大量研究。本文在收集了大量研究报道基础上 ,对森林细根研究结果进行综述。结果如下 :细根 (直径 <2～ 5mm)生物量变化在 46～ 2 80 5g·m- 2 之间 ,大部分在 10 0～ 10 0 0g·m- 2 ;细根生物量分别占地下部分总生物量和林分总生物量的 3%～ 30 %和 0 .5 %～ 10 % ;北方常绿针叶林平均细根生物量最低 (2 16g·m- 2 ) ,热带常绿阔叶林最高 (10 87g·m- 2 )。细根年净生产量 2 0～ 1317g·m- 2 ·a- 1 ,占林分总净初级生产量的3%～ 84% ,大部分在 10 %～ 6 0 % ;从北方森林到温带、亚热带至热带森林 ,细根生产量呈增加趋势 ;针叶林细根生产在总净初级生产中的比例小于阔叶林 (常绿和落叶 )。树木细根生命周期短至数天 ,长达数年。细根年周转率 4.3%～ 2 73.2 % ,阔叶林细根周转率低于针叶林。细根生产和周转是土壤碳和养分的重要来源 ,细根生产向林地输入的生物量占总输入 (细根生产和地上枯落物输入 )的 6 .2 %～ 88.7%。除气候森林类型外 ,森林生态系统细根生物量、分布、生产、周转还因季节、土壤类型、立地条件和生长发育阶段而异。同时 ,还受树木体内碳     

福建省平潭沿海秋茄人工林群落的生物量研究

对福建平潭沿海秋茄群落的现存生物量进行了研究。测定结果表明:秋茄群落的生物量为20.842 t·hm-2,其中地上部分为10.733 t·hm-2,地下部分为10.109 t·hm-2。地下部分中94.2%的根分布于地面以下0~60 cm层。由于不同滩面的环境因素差异较大,位于不同滩面秋茄群落的生物量也有所不同,位于内滩、中滩、外滩的群落生物量分别为35.429 g·m-2、16.066 g·m-2、11.031 g·m-2。     

华北落叶松人工林土壤CO2和CH4通量的时间动态变化

采用静态箱—气相色谱(GC)法,对大青山地区华北落叶松人工林夏季(6～8月)土壤CO2和CH4通量进行原位测定,研究了夏季土壤温室气体通量和昼夜变化规律及其与温度的关系.结果表明:大青山华北落叶松人工林6、7、8月土壤CO2排放通量平均值分别为296.7、727.7、461.2 mg/m2·h;不同月份的CO2通量昼夜变化均呈现昼高夜低的现象.大青山华北落叶松人工林土壤为大气CH4的汇,6～8月土壤月均CH4吸收通量均值大小顺序为8月＞7月＞6月;各月CH4吸收通量昼夜变化表现为单峰型,最大吸收通量出现在白天.9:00和19:00这2个时间区域内进行土壤呼吸观测,经矫正后可以代表6～8月大青山华北落叶松人工林土壤CO2和CH4气体通量值.温度是影响CO2和CH4通量的重要因子.     

沿海防护林生态系统不同群落生物量和能量的研究

对福建省东山县海岸基干防护林带中木麻黄 -厚荚相思群落、木麻黄 -湿地松群落和单一木麻黄群落的生物量和能量进行了研究。结果表明 ,基干防护林带中 ,复合群落的生物量和能量均要高于单一群落 ,其中木麻黄 -厚荚相思群落中的生物量和能量最高 ,为 1 670 0 64g·m- 2 和 3 41 685 70kJ·m- 2 ,其次是木麻黄-湿地松群落 1 0 1 0 4 62g·m- 2 和 2 1 0 1 2 8 3 0kJ·m- 2 ,单一木麻黄群落最低 ,为 5 1 2 9 87g·m- 2 和 1 0 5 75 1 40kJ·m- 2 。在木麻黄 -厚荚相思群落中 ,木麻黄各组分干重热值为 1 9 83～ 2 1 5 2kJ·g,厚荚相思各组分热值为2 0 0 0～ 2 3 77kJ·g- 1 ;木麻黄 -湿地松群落 ,木麻黄各组分热值为 1 9 47～ 2 0 83kJ·g- 1 ,湿地松各组分热值为2 0 5 4～ 2 1 5 4kJ·g- 1 ;单一木麻黄群落 ,木麻黄各组分热值为 1 9 98～ 2 1 2 7kJ·g- 1 。在不同群落结构中木麻黄各组分的热值存在着一定的差异 ,木麻黄 -厚荚相思群落中木麻黄各组分热值最大 ,其次是单一木麻黄群落 ,木麻黄 -湿地松群落中最小。不同的混交模式产生不同的混交效果 ,木麻黄 -厚荚相思群落的生物量是木麻黄 -湿地松群落的 1 65倍 ,是单一木麻黄群落的 3 2 6倍 ,能量是木麻黄 -湿地松群落的 1 63倍 ,是单一木麻     

北京市3种园林绿地土壤碳排放浓度比较

对北京不同植被类型的园林绿地土壤CO2排放浓度和通量进行比较,通过利用AV-SFS土壤呼吸分析仪测量,于2010年9~12月测定并分析了北京朝阳区四环附近3种典型植被类型的土壤CO2排放日变化状况。结果显示,不同植被类型的土壤CO2排放变化都表现为单峰曲线;裸地和林下园地的土壤CO2排放单日日变化幅度都比草坪地的值低;两者日排放浓度最高值高于草坪地,最低值低于草坪地。不同植被类型土壤CO2排放通量的分析结果表明,研究地在实验状态下,草坪地的土壤碳通量日变化最高,平均值为-437.1g·m-2·s-1;裸地土壤碳通量日变化最低,且与林下园地两者之间的差异较小。     

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.     

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.     

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.     

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。     

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.