海南甜瓜细菌性果斑病田间药效试验

进行了5种药剂防治甜瓜细菌性果斑病田间药效试验。试验结果表明,第二次施药后7 d,5种药剂处理中以20%二氯异氰尿酸钠可湿性粉剂750倍液的防效最好,为65.47%,其次为53.8%可杀得(氢氧化铜)2000干悬浮剂800倍液,防效为56.45%;25%叶枯唑可湿性粉剂750倍液、72%农用链霉素可溶性粉剂3 000倍液和12%松脂酸铜乳油800倍液3个处理的防效分别为51.60%,50.86%和50.20%。上述药剂在生产上可轮换使用,5 d 1次,连续2~3次。     

煤矸石边坡植被恢复探讨——以郴州市青年大道煤矸石边坡为例

以郴州市青年大道煤矸石土壤结构边坡绿化为案例,提出了利用园林绿化技术进行煤矸石废弃地景观改造与生态恢复的方法,并调查了所改造的效果。结果表明:煤矸石边坡植被修复后形成了以邓恩桉、杨树、栾树为主体的植物群落,生态系统能够自我维护,生态环境得到了明显改善。     

Bt转基因抗虫棉田昆虫群落结构研究

选用3个转Bt基因抗虫棉品种DP99B、20B、1560BG和2个非抗虫棉对照品种鄂杂棉1号、湘杂棉2号,比较研究了不同棉花群体中昆虫群落结构特征。结果表明,在未采取任何防治措施的情况下,3个转Bt基因抗虫棉对棉铃虫种群,尤其是在棉花生育前期有很好的抑制作用;同时对其他鳞翅目害虫种群也有一定控制效果,这使得棉蚜、棉叶蝉、烟粉虱等刺吸式害虫上升为主要害虫。但抗虫棉棉田昆虫群落、害虫亚群落以及天敌亚群落的多样性、均匀性均较对照棉田小,而优势集中性比对照棉田高,反映出抗虫棉棉田昆虫群落结构稳定性较差。相对来说,DP99B和20B抗虫性能较好,其棉田昆虫群落结构也比较稳定。因此,转Bt基因抗虫棉的大面积应用中,除了要关注抗毒性棉铃虫的产生和危害以外,还应特别注意其他可能上升为主要害虫(如棉蚜、棉叶蝉、烟粉虱等)的防治工作。     

From multi-criteria approach to simple protocol: Assessing habitat patches for conservation value using species rarity

We investigated conservation value (CV) related to the quality of spider communities in different non-wooded habitat patches - ranging from arable land to natural grasslands. The study was conducted in two ecologically distinct regions of Hungary: the Hungarian Great Plain and the Buda Hills. We used seven variables to indicate CV which together formed a multi-criteria space of spider community characteristics. These variables were either related to species characters obtained from an extensive background database: abundance and frequency based rarity, specialist status, association to natural habitats; or were calculated for the community at the given patch: species richness, functional diversity and species evenness. Using the variables in an ordination analysis we could establish a gradient of the patches in the multi-criteria space of the spider community characteristics. Position of patches along the first axis of the ordination was taken as the multi-criteria measure of CV. CVs established this way were strongly and positively correlated with an independent botanical CV assessment. We also sought a simpler measure of spider CV by: (a) calculating only one variable out of the seven and using it as a surrogate for the multi-criteria CV measurement; by (b) calculating this variable only for a short time period or (c) for only one spider family. Average abundance based rarity value of the species proved to be the best surrogate of the multi-criteria CV measure for both regions, and it also performed very well when sample size was restricted to two sampling occasions per patch or to a single family. This adds further evidence to, what has been found in other studies, that species rarity is a sensitive and reliable measure of the ecological and conservational status of communities.     

A landscape model for quantifying the trade-off between conservation needs and economic constraints in the management of a semi-natural grassland community

We present a landscape model to investigate the ecological consequences and costs of different management regimes in semi-natural grasslands. The model integrates dynamic abiotic conditions, management (i.e. disturbance) regime and response of more than 50 characteristic plant and insect species by modelling the dynamics of relevant niche parameters as predictors for species distribution models. We compare our results for exemplary scenarios differing in spatial and temporal scales and exemplary species belonging to different functional groups through several steps of aggregation.Our analysis aims at the question whether an infrequent massive disturbance by rototilling can serve as a less expensive alternative to annual mowing for preserving the characteristic species composition of open dry grasslands in Southern Germany. Rototilling results in a shifting mosaic determining the habitat quality for plant and animal species that may reduce the survival of local or regional populations.For some meadow species as well as the encroaching shrub species, rototilling has a detrimental effect on regional habitat quality. Other species, e.g. weeds and annual pioneers, strongly benefit or show only negligible reaction. Since this is a multi-objective problem, there is a no magic bullet in selecting an optimum scenario of measures. But by visualising the trade-off between ecological consequences and costs, our model is a valuable tool for conservation managers providing a sound scientific basis for management decisions relying on available ecological knowledge. It is also an interesting example for a model describing complex communities in a relatively simple way, simultaneously considering the main driving factors.     

Survival of bacterial DNA and culturable bacteria in archived soils from the Rothamsted Broadbalk experiment

Dried soil samples from many sources have been stored in archives world-wide over the years, but there has been little research on their value for studying microbial populations. Samples collected since 1843 from the Broadbalk field experiment on crop nutrition at Rothamsted have been used to document changes in the structure and composition of soils as agricultural practices evolve, also offering an invaluable record of environmental changes from the pre- to post-industrial era in the UK. To date, the microbial communities of these soils have not been studied, in part due to the well-documented drop in bacterial culturability in dried soils. However, modern molecular methods based on PCR amplification of DNA extracted directly from soil do not require bacterial cells to be viable or intact and may allow investigations into the legacy of bacteria that were present at the time of sample collection.

In a preliminary study, to establish if dried soils can provide a historical record of bacterial communities, samples from the Broadbalk soil archive dating back to 1868 were investigated and plots treated with either farmyard manure (FYM) or inorganic fertilizer (NPK) were compared. As anticipated, the processes of air-drying and milling greatly reduced bacterial viability whilst DNA yields declined less and may be preserved by desiccation. A higher proportion of culturable bacteria survived the archiving process in the FYM soil, possibly protected by the increased soil organic matter. The majority of surviving bacteria were firmicutes, whether collected in 2003 or in 1914, but a wide range of genera was detected in DNA extracted from the samples using PCR and DGGE of 16S rRNA genes. Analysis of DGGE band profiles indicated that the two plots maintained divergent populations. Sequence analysis of bands excised from DGGE gels, from a sample collected in 1914, revealed DNA from - and β-proteobacteria as well as firmicutes. PCR using primers specific for ammonia oxidizing bacteria showed similar band profiles across the two treatments in recently collected samples, however older samples from the NPK plot showed greater divergence. Primers specific for the genus Pseudomonas were designed and used in real-time quantitative PCR to indicate that archived soil collected in 1868 contained 10-fold less pseudomonad DNA than fresh soil, representing around 10⁵ genomes g⁻¹ soil. Prior to milling, dramatically less pseudomonad DNA was extracted from recently collected air-dried soil from the NPK compared to the FYM plot; otherwise, the two plots followed similar trends. Overall bacterial abundance, diversity and survival during the archiving process differed in the two soils, possibly due to differences in clay and soil organic matter content. Nevertheless, the results demonstrate that air-dried soils can protect microbial DNA for more than 150 years and offer an invaluable resource for future research.     

Mechanisms of real and apparent priming effects and their dependence on soil microbial biomass and community structure: critical review

The number of studies on priming effects (PE) in soil has strongly increased during the last years. The information regarding real versus apparent PE as well as their mechanisms remains controversial. Based on a meta-analysis of studies published since 1980, we evaluated the intensity, direction, and the reality of PE in dependence on the amount and quality of added primers, the microbial biomass and community structure, enzyme activities, soil pH, and aggregate size. The meta-analysis allowed revealing quantitative relationships between the amounts of added substrates as related to microbial biomass C and induced PE. Additions of easily available organic C up to 15% of microbial biomass C induce a linear increase of extra CO₂. When the added amount of easily available organic C is higher than 50% of the microbial biomass C, an exponential decrease of the PE or even a switch to negative values is often observed. A new approach based on the assessment of changes in the production of extracellular enzymes is suggested to distinguish real and apparent PE. To distinguish real and apparent PE, we discuss approaches based on the C budget. The importance of fungi for long-term changes of SOM decomposition is underlined. Priming effects can be linked with microbial community structure only considering changes in functional diversity. We conclude that the PE involves not only one mechanism but a succession of processes partly connected with succession of microbial community and functions. An overview of the dynamics and intensity of these processes as related to microbial biomass changes and C and N availability is presented.     

线虫群落结构对外源添加不同浓度铜污染物的响应

通过盆栽模拟试验的方法研究外源添加铜对土壤线虫群落结构的影响,试验添加Cu浓度分别为50 mg kg-1,100 mg kg-1,200 mg kg-1,400 mg kg-1干土和不施加污染物的对照处理,在小麦的生长关键期取样。试验结果表明:线虫不同营养类群对铜污染物的响应在小麦拔节期比较明显,拔节期捕食/杂食线虫的数量在外源添加400 mg kg-1Cu处理中显著低于对照,而不同浓度铜对食细菌线虫和食真菌线虫的影响则表现为低浓度促进高浓度抑制。线虫的生态指数对不同浓度铜污染物反映比较敏感,在小麦苗期和拔节期,与对照相比,不同浓度铜处理中线虫多样性降低,而优势度增加;自由生活线虫成熟度指数对不同浓度铜反映相对滞后,只在小麦成熟期表现出差异,即高浓度铜处理中线虫成熟度指数显著低于对照。     

宁夏盐池平沙地主要植物群落土壤水分季节动态

采用样方法,调查了盐池沙地主要植物群落,并测定了4-10月各主要植物群落样地的土壤含水量,研究了不同植物群落土壤含水量的季节动态.结果表明.在根层以下为不透水层的平沙地,各样地平均土壤含水量由小到大依次为:赖草(Leymus secalinus)群落(4.91%)<猫头刺(Oxytropis aciphylla)群落(7.42%)<柠条(Caragana korshinskii)群落(10.36%)<黑沙蒿(Artemisia ordosica)群落(12.55%)<裸地(16.27%);同一植物群落(包括裸地)的土壤含水量在各个季节也不相同.在进行沙地植被建设时,适宜采用柠条和黑沙蒿,并注意控制其合理密度及配置比例,以期达到长期稳定的治理效果.     

土壤结构性质和磷脂剖面的联合保存: 三种干燥技术的比较

There is a need to simultaneously preserve evidence of interactions between the biological community and soil structural properties of a soil in as near an intact （natural） state as possible. Three dehydration techniques were implemented and assessed for their ability to minimise disruption of both biological and physical properties of the same arable soil sample. Dehydration techniques applied until samples were at constant weight were i） air-drying at 20℃ （AD）; ii） -80 ℃ freeze for 24 h, followed by freeze-drying （-80FD）; and iii） liquid nitrogen snap freeze, followed by freeze-drying （LNPD） and were compared to a moist control. Physical structure was determined and quantified in three dimensions using X-ray computed tomography and microbial phenotypic community composition was assessed using phospholipid fatty acid （PLPA） profiling. This study confirms that any form of dehydration, when preparing soil for simultaneous biological and physical analysis, will alter the soil physical properties, and cause some change in apparent community structure. Freeze-drying （both the LNFD and -80FD treatments） was found to minimise disruption （when compared to the moist control soil） to both the soil physical properties and the community structure and is a preferable technique to air-drying which markedly alters the size and character of the pore network, as well as the phenotypic profile. The LNFD was the preferred treatment over the -80FD treatment as samples show low variability between replicates and a fast turn-around time between samples. Therefore snap freezing in liquid nitrogen, followed by freeze drying is the most appropriate form of dehydration when two sets of data, both physical and biological, need to be preserved simultaneously from a soil core.