Improving soil structure by promoting fungal abundance with organic soil amendments

Building soil structure in agroecosystems is important because it governs soil functions such as air and water movement, soil C stabilization, nutrient availability, and root system development. This study examined, under laboratory conditions, effects of organic amendments comprised of differing proportions of labile and semi-labile C on microbial community structure and macroaggregate formation in three variously textured soils where native structure was destroyed. Three amendment treatments were imposed (in order of increasing C lability): vegetable compost, dairy manure, hairy vetch (Vicia villosa Roth). Formation of water stable macroaggregates and changes in microbial community structure were evaluated over 82 days. Regardless of soil type, formation of large macroaggregates (LMA, >2000 μm diameter) was highest in soils amended with vetch, followed by manure, non-amended control, and compost. Vetch and manure had greater microbially available C and caused an increase in fungal biomarkers in all soils. Regression analysis indicated that LMA formation was most strongly related to the relative abundance of the fungal fatty acid methyl ester (FAME) 18:2ω6c (r = 0.55, p < 0.001), fungal ergosterol (r = 0.58, p < 0.001), and microbial biomass (r = 0.57, p < 0.001). Non-metric multidimensional scaling (NMS) ordination of FAME profiles revealed that vetch and manure drove shifts toward fungal-dominated soil microbial communities and greater LMA formation in these soils. This study demonstrated that, due to their greater amounts of microbially available C, vetch or manure inputs can be used to promote fungal proliferation in order to maintain or improve soil structure.     

Characterization of zein modified with a mild cross-linking agent

Zein, a predominant corn protein, is an alcohol-soluble protein extracted from corn and is an excellent film former. The characteristic brittleness of zein diminishes its usefulness as a film. It is well known that zein has a propensity for forming aggregates in solution. When zein molecules were cross-linked with 1-[3-dimethylaminopropyl]-3-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), it was found that the film-forming property was improved and the aggregation phenomenon in solution was suppressed. At the air/water interface, native zein forms brittle film with rough surface, whereas cross-linked zein forms rigid film with very smooth and even surface. Tensile strengths of the films were shown to be greatly increased by cross-linking. Objectives of this study are to determine the cross-linking mechanism of zein, the optimum reaction conditions, characteristics of the reaction product, and mechanical properties of cross-linked zein film. Through viscosity and dynamic light scattering, the cross-linking reaction was monitored. Optimum amount of EDC and NHS was determined to be 30 mg each per gram of zein. The cross-linking of zein with EDC and NHS seemed to be self-terminating because the cross-linking reaction did not proceed to precipitation.     

缙云山马尾松种群的空间分布格局研究

探索马尾松种群的分布格局及动态变化规律,从而指导人工马尾松林的合理经营管理和开发利用。运用扩散系数的t检验、Morisita指数的F检验以及一些种群聚集强度指数来研究缙云山马尾松种群的空间分布格局类型,结果表明缙云山马尾松以大中型个体为主,不同地段的马尾松空间格局分布有所差异,但整体表现不明显,总体表现为随机分布。文章同时指出为避免马尾松林的消失,应分批次种植马尾松幼苗,从而使马尾松种群保持一个平衡的状态。     

土壤有机质稳定性特征与影响因子研究综述

本文阐述了土壤有机质(SOM)稳定性的影响因素及其稳定性特征,包括有机物质化学稳定性、物理稳定性和生物化学稳定性,探讨了通过分子特征,即元素组成、功能团、分子构像;有机物、无机物质或其它有机物质之间的分子间相互作用;有机质与微生物和酶之间的作用;以及水热条件对SOM稳定性的影响。     

Spatial microdistribution of mites and organic matter in soils and caves

Spatial variability is a key to understanding the structure and function of soil biodiversity. This research addressed the question of whether a mite centimetric spatial pattern corresponds to that of organic matter in two caves and in the mineral horizon of three forest soils. Therefore, different statistical tools were used and compared: classic aggregation analysis through variance-to-mean ratio and Morisitas index, nested hierarchical ANOVA and Morans I autocorrelation coefficient. The spatial pattern of organic matter was generally found to be of the gradient or patch type, influenced by slope and trees. Cave sediments far from the entrance contained smaller patches of organic matter than deep soil and cave entrances. Mite density spatial patterns sometimes corresponded to that of organic matter in soils but never in caves. Correlograms of mite species composition were significant in soils but not in caves. The difference between the space available in caves compared with that in the tortuous pores of soil is thought to be a major structuring factor for mites, by influencing their mobility. Correlograms were the most dependable spatial analysis tools, as they could be statistically tested and used to clarify the patterns detected by the nested hierarchical ANOVA method.     

Long-term management impacts on soil C, N and physical fertility: Part I: Broadbalk experiment

For many centuries manure application to the soil has been common practice. Organic amendments and fertiliser applications can increase crop yields and soil organic matter (SOM). However, the long-term impacts on soil physical fertility are often neglected. This study was carried out on the Broadbalk Wheat Experiment at Rothamsted, UK, established in 1843 on an Aquic/Typic Paleudalf soil. Application of farmyard manure (FYM), N fertiliser and wheat straw on total organic C (C_T), labile C (C_L) and non-labile C (C_NL), total N (N_T), mean weight diameter (MWD) and unsaturated hydraulic conductivity (K_unsat) were studied on wheat (Triticum aestivum) and adjacent woodland and pasture areas. Manure additions, N fertiliser and straw incorporation increased all C fractions, particularly the C_L fraction. The addition of 35 t ha⁻¹ year⁻¹ of FYM increased C_T to 2.5 times that of the control (no fertiliser) treatment and C_L to 5 times that of the control. With highest N application and straw returned, C_T increased by 1.3 times and C_L by 1.5 times that of the control treatment. There were linear relationships between rate of N fertiliser applied and all C fractions, with the rate of increase almost double with straw than straw removed. Manure application improved MWD, as did high N fertiliser additions with straw returned. Application of N fertiliser only increased MWD and K_unsat (at 10 mm tension) if straw was returned, while the addition of manure resulted in decreased K_unsat. The highest K_unsat rate was on the high N fertiliser, straw returned treatments. The uncropped areas all had high soil structural stability. Similar relationships occurred between all C fractions and N_T and MWD for the high C soils, but relationships were much stronger with C_L than the other C fractions in the low C soils. These results showed that soils with low C concentration are more reliant on C_L for structural stability.     

集约化种植下潮土养分肥力与团聚体特征相互关系研究

通过测定封丘潮土7个肥力指标有机质、全氮、碱解氮、全磷、有效磷、全钾和速效钾,并利用主成分分析方法划分为3种肥力等级(一等、二等和三等肥力),研究了集约化种植条件下潮土养分肥力与团聚体特征的相互关系。结果表明:3种肥力等级下,大团聚体的质量比例最高,微团聚体居中,而粉黏粒最低。在0~5、5~10和10~20 cm土层,一等肥力下大团聚体的质量比例分别较三等肥力提高了25.5%、20.0%和18.5%,而微团聚体的质量比例分别降低了54.3%、43.5%和33.6%;一等肥力和二等肥力土壤团聚体的质量比例之间差异不显著。水稳性大团聚体的数量及其稳定性分别与由7个土壤肥力指标组成的养分肥力系统综合主成分得分F值呈线性正相关关系。7个肥力指标中,有机质、全氮和碱解氮与潮土大团聚体的质量比例及其稳定性显著正相关,并且这种相关性随着土壤深度增加而逐渐减弱。     

苹果叶螨类群与捕食性天敌类群空间格局的研究

本文从群落的角度,研究了成都地区苹果叶螨类群与捕食性天敌类群的空间格局关系及季节变化。结果表明:二者的空间格局在不同时期,不同类群密度下的分布均为聚集分布,捕食性天敌类群的聚集度和类群数量存在对叶螨类群的跟随效应;二者的聚集度指标存在明显的季节变化;对 Waters(1959)λ值测定结果分析,4～7月二者呈聚集分布的原因为类群物种的自身生物学特性或环境条件引起,8月为苹果叶片部分脱落引起。     

The behaviour of the species mingling index<Emphasis Type="Italic"> M</Emphasis><Subscript><Emphasis Type="Italic">sp</Emphasis></Subscript> in relation to species dominance and dispersion

Ecosystem conservation plays an increasingly important role in forest management. The value for such conservation has been directly linked to high diversity of species and structure within systems. In the past, forestry inventory practices have concentrated on aspects that were primarily required for timber management. Now, however, much interest has arisen in measures that will indicate higher or lower diversity. The interspersion of trees of different species reflects diversity at a local level and may serve as an important indicator for the simplification of a forest or woodland system. This article shows that the mingling index M_sp is robust in describing the spatial dispersion of plants; some guidelines for interpreting M_sp are provided.     

红棕象甲聚集信息素引诱桶的制作及应用

介绍红棕象甲聚集信息素引诱桶的制作及其使用方法.并应用聚集信息素对红棕象甲成虫进行田间引诱试验.结果表明:平均每个引诱桶每月引诱成虫21.21头,雌雄性比为1:0.90,其中7月份引诱的成虫数量最多,平均每个引诱桶引诱34.25头,说明了6～8月份是红棕象甲成虫活动出现的一个高峰期.在不同气候条件下,聚集信息素对红棕象甲成虫引诱效果差异较大,雨天及低温天气引诱红棕象甲成虫数量明显减少.应用红棕象甲聚集信息素诱捕红棕象甲是一种比较理想的防治方法,其操作技术简易,比较容易推广.