鸡公山5种森林水样的水质分析

在森林区域内,大气降水、穿透雨、树干径流、地表径流和集水区径流5种类型水样的表现性状可以大致模拟大气降水对森林垂直层面的作用与影响.本文通过对2020年3月-10月期间鸡公山森林区域内的上述5种类型水样的pH值等水质指标进行定位观测和对比,得到了该区域内穿透雨、树干径流和地表径流的大部分指标浓度值高于大气降水从而呈现正向效应,集水区径流的大部分指标浓度低于大气降水则呈反向效应的结论.并通过对实验结果的分析,阐释了大气降水透过森林林冠层、林下枯落物层的元素变化规律,为深入研究森林水文的内在运行机制提供依据.     

Water and forest productivity

Water availability is a major factor influencing the distribution and productivity of the earth's vegetation, but details of the mechanisms by which its effects are felt are not well understood. This is due in large part to the interactions between water and vegetation, such as through interception and change in leaf-area, which affect rates of canopy photosynthesis and transpiration. Physiological differences among species are not always directly translated to differences among stands, emphasizing the importance of climate and microclimate as controls.

Leaf-area index (L) is a critical integrator of water availability and productivity, and changes in leaf-area, such as occur through thinning and understory control, may have dramatic effects on both. There is increasing evidence that L changes significantly within an annual cycle and from year to year, even in closed-canopy conifer stands. Consequently, the season and year in which a measurement of L is made may explain much of the variability noted before in its response to water availability and effects on productivity. Because carbon, water, and nutrient cycles are so closely coupled, simulation models that represent both direct and indirect relationships are useful tools for understanding and managing forest ecosystems.     

Long-term changes in forest floor processes in southern Appalachian forests

Soil nutrient concentrations decreased in an aggrading southern Appalachian forest over a 20-year period. Construction of nutrient budgets showed significant nutrient sequestration aboveground including increased forest floor mass. We hypothesized that the changes in forest floor mass resulted from decreased litter decomposition rates because of decreased litter quality. In 1992 and 1993, we repeated a litter decomposition experiment conducted in 1969 and 1970 to test this hypothesis. In addition, we examined microarthropod populations and functional groups as litter decomposed. For four of the five species tested, first-year decomposition rates were about the same in both experiments. Initial litter nutrient concentrations of P were lower in all tree species in the most recent sampling. N, Ca, and Mg concentrations also declined in some species. These declines often resulted in decreased nutrient release rates during decomposition. Microarthropod populations differed significantly among litter species, as well as between years (probably resulting from differences in growing-season rainfall). For some litter species we found significant relationships between microarthropod populations and nutrient concentration (primarily C and N); however, most r²-values were low. Data suggest that changes in forest floor mass probably resulted from decreased litter quality and that those changes may have an effect on microarthropod populations.     

Seasonal and topographic patterns of forest floor CO(2) efflux from an upland oak forest

Forest floor CO(2) efflux (FF(cer)) is an important component of global carbon budgets, but the spatial variability of forest floor respiration within a forest type is not well documented. Measurements of FF(cer) were initiated in mid-March of 1991 and continued at biweekly to monthly intervals until mid-November. Observations were made at 45 sites along topographic gradients of the Walker Branch Watershed, Tennessee including northeast and southwest facing slopes, valley-bottoms, and exposed ridge-top locations. The FF(cer) measurements were made with a portable gas-exchange system, and all observations were accompanied by soil temperature and soil water content measurements. As expected, FF(cer) exhibited a distinct seasonal trend following patterns of soil temperature, but soil water content and the volume percent of the soil's coarse fraction were also correlated with observed rates. Over the entire measurement period, FF(cer) ranged from a typical minimum of 0.8 micro mol m(-2) s(-1) to an average maximum near 5.7 micro mol m(-2) s(-1). No significant differences in FF(cer) were observed among the ridge-top and slope positions, but FF(cer) in the valley-bottom locations was lower on several occasions. An empirical model of FF(cer) based on these observations is suggested for application to whole-stand estimates of forest carbon sequestration.     

Nutrients in litterfall,forest floor and mineral soils in two adjacent forest ecosystems in Greece

The fluxes of masses and the nutrients Ca,Mg,K,N,P and S were determined in the litterfall of two adjacent forest ecosystems of Hungarian oak(Quercus frainetto L.)and European beech(Fagus sylvatica L.)in a mountainous area of northeastern Greece in 2010–2015.The foliar litterfall for both species reached about 70%of the total litterfall,and was significantly higher from the other two fractions(woody and rest litterfall).The fluxes of masses and nutrients were compared between ecosystems for each fraction separately.Only one significant statistical difference was found,that of K in the woody litterfall.In addition,the stocks of masses and nutrients were calculated in the forest floors and mineral soils of the two ecosystems.Likewise,the stocks of nutrients in the forest floors and mineral soils were compared between ecosystems.In the L horizon of the forest floors,statistical differences,as a result of species effect,were found for the stocks of Ca and N.In the FH horizons,the masses and all the nutrient stocks differed significantly,as the beech plot had much higher quantities of organic matter and nutrients.These higher quantities were probably due to low soil temperatures(microclimate)and high acidity in the beech plot(species effect)that slowed down decomposition.In the mineral soils,the propagation of random error derived from random errors of the individual soil layers was an important factor in the statistical comparisons.Because of the soil acidity in the beech plot,the stocks of exchangeable base cations were significantly higher in the oak plot,whereas the other nutrient stocks did not differ.     

Measurement and modelling of wheel slip in forwarding on moraine forest floor

Wheel slip is one of the key factors for determining wheel performance and resulting damage to soil and vegetation. However, the wheel slip on a typical Scandinavian moraine forest floor has not been studied. A slip model was therefore developed from the well‐known Wismer‐Luth mobility model, and tested against empirical observations. Wheel slip of both an empty and a loaded forwarder on different slopes was measured using videotaping and an image processing technique. The field observations matched theoretical values well on gradual slopes, but on steeper slopes, close to the technical climbing ability, the discrepancies were pronounced. Wheel slip on moraine soils with good bearing capacity on gradual slopes (‐40 to 30%) varied between ‐0.15 and 0.2.     

长白山阔叶红松林林地附近湍流特征分析

2001年8月使用三维超声风温仪(IA-SA 485)测定并分析了中国科学院长白山森林生态系统开放站阔叶红松林样地(12828扙,4224?N,吉林省,中国)林地附近湍流特征。发现林地附近气流具有高度间歇性和不对称性,并为活跃的向上运动主导。垂直方向的湍流受到抑制,其时间尺度和长度尺度都小于水平两个分量的相应值,林地附近的气团呈偏平结构。热力作用对当地湍流产生和维持过程起到了主导作用。图4表3参15。     

Water absorption of boron-treated and heat-modified wood

Heat treatments change the chemical and physical properties of wood and dimensional stability and hygroscopicity are affected as a result of modifications of wood cell components. This study evaluated the water absorption of wood specimens treated with boron compounds followed by heat treatment. Sugi (Cryptomeria japonica D. Don) sapwood specimens treated with either boric acid (BA) or disodium octoborate tetrahydrate (DOT) solutions were heat-modified at either 180° or 220°C for 2 or 4 h. Carbohydrate composition and water absorption of the specimens were then measured and compared with those of untreated and unheated specimens. Wood carbohydrates were significantly degraded in the specimens after heat treatment. The heat treatment evidently decreased the water absorption and the heat-modified specimens absorbed less water than unheated specimens. The higher the treatment temperature and the longer the treatment time, the lower the amount of absorbed water. The boron-treated and heat-modified specimens, however, showed increased water absorption due to the hygroscopic properties of BA and DOT.     

Contribution of forest floor fractions to carbon storage and abundance patterns of arbuscular mycorrhizal fungal colonisation in a tropical montane forest

Forest floor carbon stocks, which include different components of litter, hemic and sapric materials, have not been empirically quantified in tropical montane forest, although they influence soil carbon (C) pools. To date, the contribution of arbuscular mycorrhizae in C sequestration potentials in tropical montane forests have not been clearly investigated. This study determined the amount of C stocks in the different decomposing layers of forest floor, mainly litter, hemic and sapric materials. The abundance of arbuscular mycorrhizal root colonisation differed among forest floor fractions. Forest floor was measured for depth, area density, dry mass and carbon fraction separately in Sungai Kial Forest Reserve, Pahang, Malaysia to calculate C stocks. Percentages of root colonisation in the hemic and sapric materials were investigated. The results showed that forest floor C stocks were significantly higher in hemic (5 Mg C ha^?1) and sapric (7.7 Mg C ha^?1) compared with the litter fragments (1.5 Mg C ha^?1). Mycorrhizal root colonisation was significantly higher (75%) in the toeslope compared with the summit area in the hemic materials. Segregation of forest floor layers provided greater accuracy in forest floor C stocks reporting.     

Influence of tree species on carbon and nitrogen transformation patterns in forest floor profiles

• Background   

Among forest management practices, forest tree species substitution influences biogeochemical cycles and soil interactions rapidly (decades) and significantly.     

Water cycle investigations in Hungarian forest ecosystems

From the biological point of view the value of autotrophy plant association is determined by the carbon fixation and the carbon cycle. Among the plant associations of Hungary, forest has the largest biological carbon fixation and carbon cycle.In general, the annual water cycle is the key factor in the organic material production of the Hungarian forests. The most intensive water consumption and organic material production take place from May till July, which period is named main water consumption and respectively main growing period. In Hungary the categories of the forest climate are characterized by main tree species and based on the characteristic meteorological data (Jaro and Tatraaljai, 1985). In Hungary the forest area covered by stand is 1,650,000 hm2. Beech forest climate covers 8% of the forest area, hornbeam-oak forest climate covers 22%, sessile oak-Turkey oak forest climate covers 48% and forest steppe climate covers 22%. Partly in the frame of ICP-Forests, the Department of Ecology in the Forest Research Institute carries out long term, complex ecophysiological investigations on several sample plots (so-called basic plots) throughout the whole country. The organic material production (growth), the nutrient and water cycle, the measurements of air pollutants and meteorological parameters, as well as chemical analyses are all part of the investigations. As a comparison the figure of two basic plots (Sopron-Piispokladany) shows the water cycles of a good growing beech stand in beech climate and a weak pedunculate oak stand in forest steppe climate in the hydrological year of 2001-2002. In the Hungarian forest 60%-70% of the precipitation is used for interception, evaporation, and in the vegetation season, for the transpiration both in beech and forest steppe climate. From other point of view, only 30%-40% of the open air precipitation infiltrates into the soil and can be utilized by the forest.     

Effects of clearfelling on forest floor accumulation and litter decomposition in a radiata pine plantation

The short-term effects of clearfelling a Pinus radiata D. Don. stand in Catalonia (NE Spain) under Mediterranean conditions were assessed. Harvesting had little effect on the surface soil distribution and accumulation. However, after clearfelling the range of soil temperatures increased, the moisture content of the L layer decreased, and the decomposition of brown needles was retarded (mass loss rate for the first year of the incubation 0.47 year⁻¹ vs. 0.29 year⁻¹). Green needles incorporated as a result of harvesting operations showed the same rates of mass loss as brown needles. Brown needles released substantial amounts of all major nutrients, especially at the beginning of the incubation. In both clearfelled and undisturbed stands, this sudden nutrient flush may have important implications in the nutrient economy of the vegetation. In contrast, green needles behaved as a sink of nitrogen and calcium, therefore representing a temporary reservoir after clearfelling.     

干旱期间森林土壤的水源涵养作用

针对西南旱情比较严重的贵州省册亨县,选取了5种不同土地利用类型,对它们的土壤物理特性及其水源涵养功能进行了研究.结果表明:不同土地利用类型的土壤容重均随土层深度的增加而增加,土壤总孔隙度与毛管孔隙度都是随土层深度的增加而减小.有林地(落叶阔叶林地、灌木林地和杉木林地)的土壤物理性状要好于荒山和耕地.有林地在土壤持蓄水能力和蓄渗水能力这两方面均要远远好于荒山和耕地.森林的水源涵养功能要远高于耕地和荒山,具体排序为落叶阔叶林地(726.67 t/hm2)>杉木林地(706.80 t/hm2)>灌木林地(704.03 t/hm2)>耕地(553.17 t/hm2)>荒山(444.25 t/hm2).     

森林资源碳汇效益及价值体现的探讨

本文主要论述了森林资源的碳汇作用、碳汇效益及价值体现的方式。     

Establishment and growth of coniferous seedlings in an altered forest floor after long-term exclusion of deer

We evaluated differences between the forest floors and the establishment and growth of coniferous seedlings in fenced (13 years) and unfenced plots on Mt Ohdaigahara where the sika deer (Cervus nippon) population density is high. Large coniferous seedlings (height > 0.05 m) were less abundant in the unfenced plot, as a result of deer browsing. Small coniferous seedlings (height < 0.05 m), however, were more abundant in the unfenced plot, where most seedlings of Abies homolepis were found on bare ground and those of Picea jezoensis var. hondoensis were found on buttresses and fallen logs. The large area of bare ground in the unfenced plot was caused by deer browsing. Deer therefore have an indirect effect on the emergence and growth of small coniferous seedlings by modifying the forest floor.     

人促天然更新恢复南方地带性阔叶林植被的探讨

试验研究表明:应用伐后更新、人工改造等办法促进地带性残次阔叶林更新,5年成林,胸径、树高达到人工林的速生标准,生长量、蓄积量则是人工林的3～5倍,且树种丰富,林分层次多。     

Carbon and nitrogen in forest floor and mineral soil under six common European tree species

The knowledge of tree species effects on soil C and N pools is scarce, particularly for European deciduous tree species. We studied forest floor and mineral soil carbon and nitrogen under six common European tree species in a common garden design replicated at six sites in Denmark. Three decades after planting the six tree species had different profiles in terms of litterfall, forest floor and mineral soil C and N attributes. Three groups were identified: (1) ash, maple and lime, (2) beech and oak, and (3) spruce. There were significant differences in forest floor and soil C and N contents and C/N ratios, also among the five deciduous tree species. The influence of tree species was most pronounced in the forest floor, where C and N contents increased in the order ash = lime = maple < oak = beech ? spruce. Tree species influenced mineral soil only in some of the sampled soil layers within 30 cm depth. Species with low forest floor C and N content had more C and N in the mineral soil. This opposite trend probably offset the differences in forest floor C and N with no significant difference between tree species in C and N contents of the whole soil profile. The effect of tree species on forest floor C and N content was primarily attributed to large differences in turnover rates as indicated by fractional annual loss of forest floor C and N. The C/N ratio of foliar litterfall was a good indicator of forest floor C and N contents, fractional annual loss of forest floor C and N, and mineral soil N status. Forest floor and litterfall C/N ratios were not related, whereas the C/N ratio of mineral soil (0–30 cm) better indicated N status under deciduous species on rich soil. The results suggest that European deciduous tree species differ in C and N sequestration rates within forest floor and mineral soil, respectively, but there is little evidence of major differences in the combined forest floor and mineral soil after three decades.