Improved interpretation of soil — macrofungal relations in south Swedish beech forests using two complementary regression analyses

Two regression analyses were used to study how the absence/presence of fungi in south Swedish beech forest is related to topsoil and litter chemistry. Since many soil variables are correlated, each species was related to models of (1) the rotated principal components of the soil properties (as suggested by a previous study) and (2) the underlying primary variables. The study indicated that the two analyses are complementary and provide a mean for further interpretation of the results, since they consider different aspects of sporophore occurrence in relation to soil properties. One of the conclusions is that various litter variables, partly related to the mull/mor gradient, are of greater importance than indicated in a previous study.Abbreviations PCA principal component analysis - PC principal component     

Seasonal changes in abundance and spatial distribution of the soil arthropods in a Japanese cedar (Cryptomeria japonica D.Don) plantation,with special reference to collembola and acarina

Seasonal changes in abundance and distribution pattern of soil micro-arthropods were studied in connection with a few environmental factors in a Japanese cedar (Cryptomeria japonica D. Don) plantation. The soil arthropods were sampled from three different depths at intervals of two months for two years. Of the collected animals (total 51000–155000 m⁻²), Collembola (20000–76000 m⁻²), oribatid mites (19000–55000 m⁻²) and carnivorous mites (6200–21000 m⁻²) were the numerically dominant animal groups. Low seasonal variations in abundance indicated their seasonal stability in population levels. The trends in seasonal fluctuation were similar among these groups and between the two years, showing bimodal pattern with little peaks in early summer and winter. The pattern of seasonal fluctuation in abundance of carnivorous mites (P _d) was significantly synchronized with that in the total abundance of Collembola and oribatid mites (P _τ). Thus, the number-ratios (P _d/P _τ) were fairly constant, ranging from 0.10 to 0.25. Seasonal changes in vertical distribution of the three animal groups showed a similar pattern for both years. The downward migrations were shown to be more affected by low temperatures in winter accompanied by snow coverage rather than by the desiccation of the surface soil in summer. All the three groups demonstrated as a whole slightly aggregated patterns of horizontal distribution throughout the two years. Temporal increases in the patchiness indices were observed from summer to autumn when the moisture content of the surface soil was low.     

Niche characteristics ofCladonia lichens associated with geothermal vents in Japan

To characterize the niche preferences ofCladonia species associated with geothermal areas, we sampled ten thermal areas in Japan. It appears from the current study and related studies that some members of theCladonia genus can have a wide tolerance for both soil temperature and pH conditions.Cladonia mitis is the most abundantCladonia and occurs throughout most of the vent system.Cladonia theiophila occurs most frequently at a soil pH of less than 3.5, but occurs mostly at lower soil surface temperatures (below 29°C).Cladonia floerkeana is very restricted in its distribution and is most abundant where the root zone temperature (15 cm) is above 70°C, the surface temperature is above 40°C, and the pH is 5–5.5. Tolerances to low pH, high soil temperatures, and low to moderate humidity permitCladonia species to grow where vascular plants and even mosses cannot grow and thus they avoid the competition such plants would provide to these slow-growing organisms. Contribution from the Phytotaxonomical and Geobotanical Laboratory, Hiroshima University, N. Ser. No. 390.     

土壤微量元素测试及其应用

土壤微量元素测试在其发展历史过程中,不断改进技术,逐渐深入地揭示土壤供给微量元素的能力,对指导施肥和保护生态环境起着积极的作用。现代测试手段发展到广泛采用原子吸收光谱(AA)和电感耦合等离子体发射光谱(ICP),但比色法(光度法)和极谱法不仅设备比较简便,而且新的显色剂、催化系统等方面的研究进展,使其对某些元素的测定灵敏度和准确度超过AA和ICP,从而在微量元素测试技术中仍占据一定地位。土壤溶液抽取技术虽然有所改进,但有效态微量元素仍然主要是选用适当提取剂来提取测定。临界值和分级标准的确定是应用测定值的桥梁。作者曾采用全幅分级标准分级制图,确定缺素面积和需肥区域,再根据土壤含量水平和增产幅度之间的函数关系预测增产效果和投入的经济效益。     

抗旱性不同的小麦叶片的渗透调节与水分状况的关系

两年的试验结果表明:在土壤水分胁迫下抗旱性强的小麦品种叶片的相对含水量和水势均高于抗旱性弱的品种;渗透势与水势为线性关系,水势每变动一个单位,渗透势变动0.71—0.93个单位;渗透势与相对含水量的对数化关系为两条直线组成的一条折线,第一条直线渗透势的下降完全由渗透调节引起;第二条直线渗透势下降主要是细胞失水浓缩的结果。渗透调节能力为:秦麦3号>昌乐5号>山农587>济南13>烟农15>鲁麦5号。     

Soil seed banks and post-fire seed deposition across a forest - fynbos ecotone in the Cape Province

Abstract. The relative sizes and composition of soil seed banks, the influence of fire and the post-fire deposition of seeds were investigated in a riparian forest and adjacent fynbos and transitional vegetation in Swartboskloof. Brief complementary studies of soil seed banks were conducted in poorly-developed forest and scree forest soils. Numbers of species in each vegetation type were very similar, but there were fewer seeds in riparian forest soil than in the transitional and fynbos zones. These patterns were not repeated in poorly-developed forest and scree forest. No effects of fire on soil seed banks were detected. Forest soil had relatively large numbers of seeds stored at 10 to 15 cm deep, with many zoochorous and few myr-mecochorous seeds. Anemochorous and ornithochorous seeds of forest species formed a major component of seed deposition within the transitional and fynbos zones in the first year after fire. The numbers of anemochorous forest seeds in the fynbos declined with distance from the forest edge. The deposition of ornithochorous forest seeds was less closely related to distance from the source, and was not exclusively associated with the presence of tall or fruit-bearing shrubs. Regeneration after canopy-destroying disturbance in the forest is likely to emanate from the soil seed banks of pioneer species which now or previously occurred on forest margins. Seed availability does not appear to limit colonization of fynbos by forest species soon after fire.     

Vegetation development in abandoned gravel pits: effects of surrounding vegetation,substrate and regionality

Abstract. Vegetation development in 68 abandoned gravel pits and their surroundings in five regions in Sweden is described by means of classification and ordination. Most pits were less than 10 yr old, but some pits in central Sweden were up to 100 yr old. For 26 pits in central Sweden the results of mechanical and chemical soil analyses are presented. Vegetation in young pits is more homogeneous than the vegetation in the surroundings. The surrounding vegetation type strongly affects pit vegetation. There are regional differences in pit vegetation between pits in coniferous forests in different parts of Sweden. Old gravel pits are clearly distinguished from young ones and show more resemblance to the surrounding vegetation. Tree layer cover and nitrogen content increase, whereas C/N ratio and pH decrease with age. Species richness of the gravel pits was not related to their size.     

Seedling emergence after sod cutting in grass heath

Abstract. Experimental plots in grass heath, previously subjected to various sod cutting treatments, contained a seed store of ericoid dwarf shrubs, but seeds of grasses of the former grass heath were not found. The density of emerging dwarf-shrub seedlings in the plots was determined mainly by soil moisture, but with density of seeds stored in the soil and soil acidity as modifying factors. It is concluded that the restoration of a dwarf-shrub heathby sod cutting is relatively successful, as compared to other measures, because the grass seeds become obsolete.     

Bacterial conjugation betweenEscherichia coli andPseudomonas spp. donor and recipient cells in soil

Summary Experiments conducted in microcosms containing loam soil samples inoculated with eitherE. coli orPseudomonas spp. donor and recipient cells showed that bacterial cells survived and conjugated over a 24-h incubation period.E. coli transconjugants were detected 6 h after donor and recipient strains were introduced into sterile soil samples. In non-sterile soil samples, transconjugants were detected between 8 and 24 h incubation.Pseudomonas transconjugants were recovered from sterile soil samples between 6 and 12 h after their introduction and as early as 2 h in non-sterile soil. The results show that genetic interactions occur in non-sterile soil in relatively short periods of time at relatively high transfer frequencies (10^–3 to 10^–4). Studies on genetic interactions in soil are becoming necessary in risk assessment/environmental impact studies prior to the release of genetically engineered or modified organisms into uncontained environments.     

Cycling of soil carbon in a Japanese red pine forest I. Before a clear-felling

Cycling of soil carbon was measured synthetically and quantitatively throughout a year in two Japanese red pine forest stands on mid- and foot-slopes at Mt. Takao, Hiroshima Prefecture, west Japan. There was no distinct difference of soil temperature along the slopes, but the soil water content was higher on the foot-slope than on the midslope. The carbon flow (litterfall, soil respiration, etc.) rates were larger on the foot-slope than on the mid-slope, but there was no significant difference of the accumulation of soil carbon (A₀ layer or human in mineral soil) between the areas. The results of the analysis of soil carbon cycling based on a compartment model show that the relative decomposition rate of A₀ layer and humaus in mineral soil increased 1.4–1.5 fold from the mid- to the foot-slopes, corresponding to the soil moisture condition. The relative decomposition rate of A₀ layer was, however, about one-third of that in a evergreen oak forest. This fact suggests that the great resistance of needle litter to decomposition is one of the main limiting factors of the cycling of soil carbon and prevents the fertilization of mineral soil in the pine forest, which was also proven by the simulation of dynamics of soil carbon cycling.