Post-fire vegetative dynamics as drivers of microbial community structure and function in forest soils

Soil microorganisms have numerous functional roles in forest ecosystems, including: serving as sources and sinks of key nutrients and catalysts of nutrient transformations; acting as engineers and maintainers of soil structure; and forming mutualistic relationships with roots that improve plant fitness. Although both prescribed and wildland fires are common in temperate forests of North America, few studies have addressed the long-term influence of such disturbances on the soil microflora in these ecosystems. Fire alters the soil microbial community structure in the short-term primarily through heat-induced microbial mortality. Over the long-term, fire may modify soil communities by altering plant community composition via plant-induced changes in the soil environment. In this review, we summarize and synthesize the various studies that have assessed the effects of fire on forest soil microorganisms, emphasizing the mechanisms by which fire impacts these vital ecosystem engineers. The examples used in this paper are derived primarily from studies of ponderosa pine-dominated forests of the Inland West of the USA; these forests have some of the shortest historical fire-return intervals of any forest type, and thus the evolutionary role of fire in shaping these forests is likely the strongest. We argue that the short-term effects of fire on soil microflora and the processes they catalyze are transient, and suggest that more research be devoted to linking long-term plant community responses with those of the mutually dependent soil microflora.     

赣南富稀土景观中稀土元素的土壤地球化学特征

选择赣南富稀土矿区典型环境地球化学景观,研究了稀土元素在土壤中的含量、分布及赋存形态特征,结果表明,在各单元景观的土壤中稀土元素的含量２具有规律性。土壤中稀土元素的分布模式继承了母岩的特征真有明显的Ｅｕ负异常。但Ｃｅ在残积景观和堆积淋溶景观的奎训呈现正异常,而在水上景观土壤中出现Ｃｅ负异常。稀土元素在各单元景观土壤中的赋存形态特征也不同。总体上,稀土元素主要以可交换态和有机结合态形式存在于矿区土壤     

抗性微生物强化重金属污染土壤植物修复的研究进展

抗性微生物对重金属的溶解、络合等作用,提高了重金属在土壤中的生物可利用性,从而增强植物对重金属的吸收富集;其次,抗性微生物分泌的植物激素可以促进植物生长、扩大生物量,进一步提高重金属污染土壤植物修复的效率.为此,对抗性微生物在强化重金属污染土壤中植物修复的作用机制和实际应用方面进行了综述,并分析目前存在的不足及今后的研...     

周巷镇耕地土壤环境质量现状及评价

本文调查分析了周巷镇36个土壤样品的土壤环境质量状况,周巷镇土壤中污染物的平均含量分别为:Pb16.1mg/kg、Cr28.2mg/kg、Cd0.162mg/kg、Hg0.101mg/kg、As5.0mg/kg、Cu22.4mg/kg.结果表明:周巷镇土壤环境质量较好,适宜于绿色食品生产.     

Use of treated municipal wastewater in irrigated agriculture—Review of some practices in Spain and Greece

Approximately, seventy (70) percent of world water use including all the water diverted from rivers and pumped from underground is used for agricultural irrigation, so that the reuse of treated municipal wastewater for purposes such as agricultural and landscape irrigation reduces the amount of water that needs to be extracted from natural water sources as well as reducing discharge of wastewater to the environment. Thus, treated municipal wastewater is a valuable water source for recycling and reuse in the Mediterranean countries and other arid and semi-arid regions which are confronting increasing water shortages. Treated wastewater reuse in agriculture is a common practice in the Mediterranean countries and there is a considerable interest in the long-term effects of treated wastewater on crops intended for human consumption. This paper reviews the fundamentals of agricultural irrigation using treated municipal wastewater and the status of municipal wastewater reuse in Greece and Spain with studies related to the effects on soils and plants.     

模拟自然气候条件下未饱和土壤中热质迁移过程的实验研究

本文利用可模拟自然环境的土壤热质迁移实验装置,就自然气候条件下风速,日照,大气温度与湿度等因素对土壤中水,盐,热等要素的一维动态迁移的影响进行了多种条件下的实验研究,揭示了土壤内温度,水分和盐分的分布动态与外界气候因素之间的联系,获得了土壤热质迁移过程中各主要参数的变化规律,对于本文实验中的砂土而言,发现土表以下存在吸水,过渡和释水三个自然分区,并分析了热渗透深度和平衡时间等主要的热质迁移特征,人     

贵州东部地区茶园土壤甲螨种类调查研究(甲螨亚目)

报道了贵州东部地区茶园土壤甲螨111种,分属38科。以奥甲螨科、单翼甲螨科、盲甲螨科、菌甲螨科、上罗甲螨科等为茶园土壤甲螨优势类群,新小奥甲螨、卵角单翼甲螨、棒菌甲螨等为茶园土壤甲螨类动物常见种类。     

Phosphate-rich soils in the European Union: estimating total plant-available phosphorus

The estimation of plant-available phosphorus (P) has become important for farmers and environmental agencies, because it can help them: (i) use existing soil P reserves more efficiently, and (ii) establish criteria for reducing or stopping application of P fertilizers, which can cause water eutrophication. In this study, total plant-available P (TPAP) in 12 P-rich soils from major agricultural areas of the European Union was estimated by successive cropping in pots, and compared to the amount of P extracted by different methods. Plant desorption curves generally conformed to a Temkin equation (P uptake = A+B log(P concentration in soil solution)). P uptake was also linearly related to the change in Olsen P of soil. Of the various laboratory methods used to estimate TPAP, extraction by goethite (viz., a ‘near-infinite’ Fe oxide sink) proved the most efficient, followed by repeated extraction with an anion-exchange resin in chloride form. Isotopically exchangeable P (IEP) was found to be useless for estimating TPAP, particularly in acid soils. However, IEP at 14 days, combined with the P concentration in the soil solution, provided a good estimate for TPAP. In practice, TPAP can also be predicted from Olsen P, provided the varying efficiency of bicarbonate in extracting P from soils in different pH ranges is considered.     

Bioturbation on wildfire-affected southeast Australian hillslopes: Spatial and temporal variation

The importance of bioturbation as an agent of soil and geomorphological change is well known but few observations have been made of spatial and temporal variations in bioturbation rates. We quantified variations in surface bioturbation by ants (particularly Aphaenogaster longiceps) and vertebrates in the sandstone terrain of the Blue Mountains, southeast Australia. Following wildfire during the period late 2001–early 2002, we monitored thirty-three 5 m² plots positioned in six different slope units and in two catchments affected by different wildfire severities. Measurements were made seasonally for six years. Overall, mean rates of ant mounding and surface scraping by vertebrates were similar (246 ± 339 g m^− 2 yr^− 1 and 274 ± 179 g m^− 2 yr^− 1, respectively). However, rates varied substantially according to slope unit, showing a marked maximum for both ant mounding and total bioturbation on footslopes. Possible reasons for this spatial variation are discussed. A complex response to various soil and ecological factors such as soil texture, soil moisture and vegetation patterns is the most likely explanation. Associated estimates of topsoil (0–30 cm depth) turnover times, based on ant mounding rates alone, ranged from 300 to 100,000 years for different slope units. In contrast to previous findings, wildfire severity did not seem to affect bioturbation, possibly because of ant survival in deep nests and spatial patchiness of fire severity. There was likewise no clear link between temporal changes in bioturbation and fire severity; high rates in the first two years after wildfire were followed by lower rates for all burn severity types. There was also seasonal variability that was not directly related to rainfall. The results substantiate the importance of bioturbation in modifying soil characteristics and influencing soil erosion, especially following a major disturbance event like wildfire.     

杭州市居民区土壤重金属的化学特性及其与酸缓冲性的关系

杭州市居民区土壤中Cd、Cr、Cu、Ni、Pb、Zn、Mn和Mo均有不同程度的积累;除Cr、Mo外, 居民区重金属的积累一般低于该市商业区。居民区土壤中Cd、Co、Cr和Ni主要以稳定的残余态为主;而Cu、Pb、Zn和Mn则以可提取态为主。在正常条件下,居民区土壤具有较高的重金属吸持能力,被吸持的重金属较为稳定,绝大部分不易被中性盐所交换。但随着pH的下降,土壤对重金属的吸持能力明显降低,而重金属的释放潜力明显增加。杭州市居民区土壤的酸缓冲性有较大的变化,主要受土壤CaCO3含量的影响,缓冲性高的土壤,重金属可溶性较低。居民区土壤由于受建筑物质中CaCO3的影响,具较高的酸缓冲性,增加了土壤重金属的稳定性。