Effects of stream acidification on fungal biomass in decaying beech leaves and leaf palatability

We examined the effect of surface water acidification on rates of decomposition, ergosterol concentrations (as a measure of fungal biomass), and palatability to shredders of common beech leaves (Fagus sylvatica L.) in five mountain streams (pH 4.7-7.1). Leaf decomposition was significantly faster in the circumneutral streams (pH 6.4-7.1; k > or = 0.00175 d(-1)), when compared to acidic streams (pH 4.7-4.9; k < or = 0.00100 d(-1)). Fungal biomass showed no particular trend along the acidification gradient except that it peaked earlier in the stream closest to neutrality. Leaf palatability, measured as the feeding activity of the leaf-shredding amphipod Gammarus fossarum Koch, varied with the exposure time in the streams. Except for the higher palatability of leaves exposed during 6 weeks at the highest pH, patterns among streams were mostly similar. These results suggest that reduced processing rates in the most acidic streams were not related to differences in fungal biomass associated with decomposing leaves and that microbial conditioning was only slightly delayed by acidification. Possible effects of low pH and related variables (Ca, Al) on microbial decomposition and detritivorous macroinvertebrates are discussed to clarify the inhibition of beech leaf decomposition in the studied systems.     

Involvement of Ligninlike Compounds in Toxicity of Dietary Alder Leaf Litter Against Mosquito Larvae

The toxicological characteristics of dietary decomposed alder leaf litter against mosquito larvae were further investigated through enzymatic and chemical purification of a phenoliclike cell-wall fraction isolated from crude litter. The toxicity of the subfractions obtained was controlled by standard bioassays on third instars of Aedes aegypti chosen as a reference target species. Enzymatic hydrolyses of the cell-wall fraction were performed with caylase, pectolyase, esterase, and -glycosidase, in order to release, respectively, cellulose material and phenolic compounds bound to lignins. These treatments did not affect the larvicidal activity and the phenolic activity of the cell-wall fraction. Chemical alkaline and acid hydrolyses were carried out to break ester and glycosidic bonds of the cell-wall fraction. Comparison of HPLC profiles of the hydrolysates from both toxic and nontoxic fractions did not reveal differences between the phenolic acids released. Aluminum chloride, known for its phenolic complexing activity, counteracted the larvicidal activity of the cell-wall fraction. Altogether, these results suggest the involvement of ligninlike compounds in the toxicity of dietary alder leaf litter against larval mosquitoes. The toxicity of this fraction, which was very sensitive to drastic and smooth oxidations, seemed to be associated with a strong oxidative potential. These results are discussed in relation to a possible mode of action of lignins in the plant–mosquito interactions.     

Effect of breed on performance and meat quality of first parity sows in a seasonal organic rearing system

BACKGROUND: The objective was to compare the performance and meat quality of two different pig breeds: the modern crossbred Landrace × Yorkshire (LY) and the traditional Danish Black‐Spotted (BS) breed. The LY gilts and four of the BS gilts were inseminated with semen from Duroc (D) boars; the remaining BS gilts were served by BS boars. The experiment was performed on 26 gilts over 2 years. RESULTS: The BS breed in general had smaller litter sizes and weaned on average in terms of kg piglet 35% less than the modern breed combination. Crossbred piglets of BS × D had growth rates from birth to weaning comparable with piglets of LY × D. BS first parity sows were significantly fatter and less meaty, and the meat was significantly redder and darker compared to LY. The sensory profiling revealed increased sweetness, crumbliness and tenderness in BS. Further, the fat of the BS breed seemed to be characterized by a special nutty taste. CONCLUSION: The traditional breed has lower productivity and thereby higher costs of production compared to the modern genotypes. On the other hand, the meat and fat of the traditional purebred have special characteristics that might trigger a market premium. Copyright © 2011 Society of Chemical Industry     

基于稳定状态差异的停车及抛落物检测算法

近年来,道路交通状况的自动检测逐渐成为研究的热点。因为违法停车、抛落物不仅影响交通秩序、诱发交通事故而且有损城市形象,所以停车、抛落物的检测已经构成道路交通状况自动检测的重要组成部分。提出了一种自动检测停车事件及抛落物事件的方法,利用双向跟踪实现停车及抛落物的检测,通过分析目标面积实现两者的区分。实验表明,该方法实时性好、准确性强,具有很大的实用价值。     

杉木人工林凋落物分解动态

在福建三明16 a生的杉木人工林内,利用网袋法对叶凋落物的分解和C、N元素释放进行了研究.经过2 a的分解后,凋落物残留率为24.58%,平均分解系数为0.776 4,周转期为3.99 a.凋落物C、N浓度随分解时间的进行而逐渐减少,C/N比也呈下降趋势.C、N残留率与凋落叶干物质残留率表现出显著的正相关性,表明两元素的释放是自身释放和干物质消失双重作用的结果.     

冀北山地人工油松林水文效应研究

分密度对森林水文效应有一定影响,以冀北山地不同密度油松人工林的植被层、枯落物层和土壤层为研究对象,对其水文效应进行了研究。结果表明:林冠截留能力随着林分密度的减小而减小,林下植被截留能力随着林分密度的减小而增大;林下枯落物最大持水量随着林分密度的减小而减小,其中林分密度分别为1 584株/hm~2、864株/hm~2和684株/hm~2标准地枯落物最大持水量差距相对较小,分别是林分密度388株/hm~2标准地的1.56倍、1.50倍和1.42倍;388株/hm~2油松林枯落物有效拦蓄量较小,但其枯落物初期持水速率较大。土壤持水能力随着林分密度的减小表现出逐渐增大趋势,林分密度864株/hm~2、684株/hm~2和388株/hm~2标准地土壤持水能力分别为林分密度1 584株/hm~2标准地的1.05倍、1.16倍、1.17倍,密度684株/hm~2和388株/hm~2标准地的土壤持水能力较为接近。对油松人工林进行合理抚育间伐,保留合适密度,能改善其涵养水源功能。     

包装废弃物综合治理研究

在全面调查城市生活垃圾中包装废弃物含量的基础上，阐述了包装废弃物对环境与社会的危害及综合治理的意义。研究了切实可行的包装废弃物回收利用的技术方法，并科学地提出了包装废弃物综合治理的措施。