DNA recovery from agarose gels with a simple centrifuge-driven sephadex filtration

Conventional methods of DNA recovery from agarose gel generally require expensive equipment, extended elution times, or considerable handling of the sample after elution. We developed a simple protocol for a quick and effective recovery of DNA from agarose gels with good yield and quality. Using a Sephadex resin filled spin column, DNA fragments of 500 bp to 6 kb in an agarose gel slice were easily recovered by a 2 min centrifugation. The recovery efficiencies were over 40%-50% and the eluted DNA can be used directly for downstream application, such as polymerase chain reactions (PCR) and restriction enzyme digestion. This method could also be used to recover large DNA fragment (48 kb) without degradation. The use of Sephadex helps to remove small molecular impurities from agarose and it also reduces the chance of clogging the column filter caused by direct contact with agarose.     

建平半干旱地区石质山地造林技术研究

研究了不同植物在石质山地的造林成活率、土壤化学性质随造林年限的变化和造林措施对土壤化学性质和植物胸径、树高年净生长量的影响。结果表明：不同植物在石质山地的成活率在21%～85%之间,其中白榆和沙打旺的成活率分别为81%和85%,而小叶杨、刺槐、栾树的成活率均在70%左右;植被能明显提高石质山地不同土层的有机质、全N、P2O5含量,但提高程度随土层深度、养分种类和造林年限的不同而不同;在同一土层,生物复合肥料、菌剂和保水剂均显著提高土壤有机质含量（p〈0.01）并显著降低土壤P2O5含量（p〈0.01）;只有保水剂可引起土壤全K含量的明显升高;生物复合肥料、菌剂和保水剂均显著提高白榆、小叶杨、刺槐、栾树树高和胸径的年净生长量,但保水剂的提高程度最高。     

Comparison of two harvesting systems for the production of forest biomass from the thinning of Picea abies plantations

Abstract

This study compares two principally different harvesting systems used for the thinning of Norway spruce [Picea abies (L.) Karst.] plantations in the Alps. The first system was whole-tree harvesting (WTH), producing only whole-tree chips for energy purposes. This system minimizes the production costs by simplifying the harvesting process. The other system was cut-to-length (CTL) mechanical harvesting with an excavator-based harvester. This system maximizes value recovery by producing both short sawlogs and quality fuel chips. Trials were conducted on two similar sites in the Dolomites, in northern Italy, and demonstrated that the CTL system resulted in slightly higher harvesting costs, and also higher revenue. The price differences between the different products determine which system offers the best economic results. If the delivered price of sawlogs does not exceed [euro]25 t^?1, WTH and CTL harvesting offer very similar economic performances, and become profitable only if the delivered price of raw chip wood exceeds [euro]40 t^?1. If the delivered price of sawlogs increases to [euro]50 t^?1, the mechanized CTL system always becomes preferable, and it will turn some profits when the price of raw biomass exceeds [euro]35 t^?1. The CTL system is less sensitive to long extraction and transport distances than the WTH system.     

Direct measurements of carbon exchange at forest disturbance sites: a review of results with the eddy covariance method

ABSTRACT

Boreal and temperate forests cover a large part of the Earth. Forest ecosystems are a key focus for research because of their role in the carbon (C) balance and cycle. Increasing atmospheric temperatures, different disturbances (fire, storm and insects) and forest management (clear-cutting) will change considerably the C status of forest ecosystems. Using the eddy covariance (EC) method, we can define interactions among environmental factors that influence the C-balance and whether a forest ecosystem is functioning as a C-sink or C-source or possibly is C-neutral. In our review of published studies of different disturbances, we found that most of the post-disturbance studies based on EC method focused on the effects of forest fire and clear-cutting, only a few studies studies focused on the effects of storms and insects. Generally a forest is a C-source until several years after disturbance and then a forest is able to absorb C and become a C-sink. Recovery to C-sink status required up to 20 years in clear-cut areas. Recovery following wildfire disturbance was much longer, possibly more than 50 years. Recovery to C-sink status required approximately 5 years after storm and insect outbreak, however we can not predict overall recovery period because of the missing data.     

垄茶高速公路边坡生态恢复中先锋植物的选择研究

指出了高速公路的建设对环境具有较强的破坏作用,不仅影响景观,还影响植被的生长。为了能尽快恢复植被的生长,对高速公路边坡生态恢复中先锋树种的选择进行了研究。阐述了边坡绿化的功能,提出了高速公路边坡先锋植物的选择原则和习性要求,分析了垄茶高速公路边坡的环境特点,并探讨了其边坡绿化的有效措施,特别是就先锋树种选择、植物的文化内涵和植物配置等方面进行了研究。提出了应用植物35种,其中包括豆科、蔷薇科、杜鹃花科、胡颓子科、桦木科、鼠李科等。其结果对国内高速公路边坡植被恢复具有较强的参考价值。     

喷气式网带单板干燥机节能途径探讨

为了提高单板干燥过程中的能源利用效率,对单板干燥过程进行了分析并提出有效的节能措施与途径。提出利用单板干燥尾气余热回收系统,以减少尾气直接排入大气时的热量损失,对尾气余热回收利用;提出蒸汽梯级利用回收冷凝水的热量,达到对冷凝水余热回收利用的目的。     

女儿寨小流域植被恢复与重建过程中的小气候效应研究

以女儿寨小流域为研究对象，着重研究了植被恢复重建过程中小流域系统的小气候变化特征。随着小流域内的植被恢复与重建，小流域内最高气温约降低了1～4℃，尤其以夏、秋季更为突出，约降低了3～4℃；最低气温提高了1～2℃，夏季较其它季节更为显著一些；森林不能降低小流域的日平均气温，但能略微增加秋冬季的平均气温0．1～0．5℃；平均地面温度降低了0．9～1．3℃，秋冬季的地面平均温度略微增加0．1～0．5℃；年降水量增加了77～115mm；年蒸发量降低105～175mm。小流域小气候环境发生了较大的变化，小气候质量在不断的提高。     

植被恢复与重建过程中小流域降雨及水沙变化特征研究

以女儿寨小流域为研究对象，着重研究了植被恢复与重建过程中小流域系统的降雨和水沙变化特征，并对植被恢复过程中的总体减沙水平做了分析。结果表明：①受大气环流的影响，小流域年际降雨量差异较大；小流域降雨年内时间分布极为不均，集中性很大，主要集中在汛期（4-8月），但年内降雨量的月间分布趋势基本一致。②小流域迳流年际变化很大，迳流年内分配不均。迳流集中是该小流域迳流变化的一个显著特征：小流域的植被恢复与重建对洪峰的出现和洪峰流量具有明显的延缓和削减作用。③径流（Qi）主要来源于降水（Pi），二者呈明显的一元线型关系：Pi=115．7678＋2．7386Qi。④小流域的年输沙模数与年迳流量的变化规律基本一致，小流域年内产沙也高度集中，且与降水、迳流关系密切，小流域的土壤侵蚀主要由汛期的强降水引起。⑤随着小流域大面积、高标准的生态环境建设，1990年至2004年间小流域的输沙模数呈锐减之势，植被恢复与重建起到了显著的减沙效应。     

反硝化脱氮除磷-侧流磷回收工艺效能

为了调查反硝化同步脱氮除磷-侧流磷回收新工艺的工艺效能,该试验在该工艺稳定运行条件下评价其污染物(化学需氧量、总氮、NH+4-N和PO3-4-P)去除能力和磷回收能力。结果表明:当进水中化学需氧量、总氮、NH+4-N和PO3-4-P的质量浓度为239.2~259.5、39.6~43.8、38.2~41.8和8.72~11.40 mg/L,出水中相应的质量浓度分别为15.2~21.6、8.5~9.6、3.6~4.7和0.31~0.49 mg/L,满足国家《城镇污水处理厂污染物排放标准》(GB18918-2002)一级A排放标准;COD主要在厌氧池被去除,NH+4-N主要在好氧硝化池中去除;污水中磷的去除主要由诱导结晶磷回收和生物除磷两部分组成;整个工艺中,磷去除效率为95.9%,其中诱导结晶磷去除率占总去除效率的71.5%,表明该工艺具有较大磷回收潜力。此外,后置曝气池可对出水中COD、NH+4-N和PO3-4-P浓度起着把关作用,有助于提高出水水质。     

Soil drought duration and severity affect cotton boll biomass by altering recovery times and carbon dynamics of subtending leaf

Drought appears at flowering and boll formation for cotton frequently. However, reports on the impact of carbon dynamics in the subtending leaf on boll biomass under periodic droughts are limited. To investigate this, experiments were carried out with two cultivars (drought-tolerant: Dexiamian 1; drought-sensitive: Yuzaomian 9110), three water levels [soil relative water content (SRWC): control (75 ± 5)%, moderate drought (60 ± 5)%, severe drought (45 ± 5)%] and five drought durations (10, 17, 24, 31 and 38 days). A 38-day drought declined the net photosynthetic rate of subtending leaf, which could be collectively attributed to the reduction in carboxylation with reduced ribulose-1,5-bisphosphate carboxylase activity, and stomal limitation with decreased stomatal conductance, along with the damage of photosynthetic apparatus with depressed maximum and actual photochemical quantum yield, leading to lower starch content. A 38-day drought also increased the activities of sucrose phosphate synthase (SPS), sucrose synthase (Susy) and expressions of genes (GhSPS1, GhSPS2, GhSusA and GhSusB) associated with these enzymes, causing the accumulation of sucrose content, finally resulting in lower boll biomass. Some of the above parameters fully recovered under more than 17-day moderate drought or over 10-day severe drought, but boll biomass still decreased after re-watering. Under 10-day moderate drought, all aforementioned indices and boll biomass were completely recovered within 7 days of re-watering, and the recovery capacity of Yuzaomian 9110 was lower than that of Dexiamian 1. Therefore, rapid recovery of photosynthesis and decline in the subtending leaf sucrose content to pre-stress levels are important factors in lessening the impacts of drought on boll biomass and are indicative of cultivar tolerance to short-term moderate water deficit.