使用Li-6400测定森林土壤呼吸应注意的几个问题

正确使用Li-6400进行森林土壤呼吸测定是保证测定精度的前提.本文以落叶松林为例,对Li-6400使用过程应该注意的问题进行了研究.结果表明:塑料圈至少应该测定前12小时进行设置,以减少土壤CO2涌出效应对呼吸的影响,而且塑料圈插入深度对测定结果影响很大:当塑料圈插入过浅时横向气体扩散及塑料圈不稳定而造成测定时CO2的再涌出效应使土壤呼吸测定值偏高;而当插入深度过深时,切断根系导致根系呼吸下降,最活跃的土壤表层呼吸受塑料圈阻隔导致的土壤微生物呼吸测定值下降,这些现象共同造成显著低估土壤呼吸测定值.此外,在晴天白天大部分时间内目标[CO2]值设定为外界相应时段的[CO2]平均值,可以保证测定误差小于5%,而在清晨和傍晚进行测定时,则应该及时调整目标值为外界[CO2]保证测量准确性.这一测定原则在实际测定中具有较高的实用性.     

Modeling to assess growth respiration of stems inPinus densiflora trees

Multiple regression analyses were applied to the respiration data obtained by an excision method to distinguish between maintenance and growth respiration in stems ofPinus densiflora. Among several types of regression models, a few models showed marked stability of coefficient of growth related respiration that are independent of degrees of correlation between predictors and any combinations of predictors. These models predicted growth respiration as 0.45 g CO₂ g (dry weight)⁻¹. At 15°C, sapwood maintenance respiration rate was estimated to 0.72 mg CO₂ g⁻¹ day⁻¹. These estimates were not different from the results obtained with standing trees.     

不同林分下土壤活性有机碳库研究

采样分析常绿阔叶林、马尾松林和人工杉木林不同层次土壤的活性有机碳含量。结果表明 :常绿阔叶林土壤微生物量碳和易氧化态碳含量高于马尾松与杉木林土壤 ,杉木林土壤水溶性碳含量相对较低。从不同层次看 ,土壤微生物量碳、易氧化态碳含量均随着土层深度加深而递减。水溶性碳、微生物量碳和易氧化态碳占总有机碳的比率分别波动在 0 31%～ 1 18%、0 90 %～ 2 5 1%和 7 0 3%～ 2 9 5 2 %之间 ,其中 ,土壤水溶性碳占总有机碳比率为马尾松林 >常绿阔叶林 >人工杉木林 ,易氧化态碳占总有机碳比率常绿阔叶林明显高于马尾松林和杉木林。不同土壤水溶性有机碳占总有机碳比率随剖面从上到下均表明出上升趋势 ,而易氧化态碳占总有机碳比率随剖面加深有规律地下降。土壤有机碳总量与各活性碳之间以及各类活性碳之间相关性均达到极显著水平。     

湿地松幼苗根系微生物数量变化规律的研究

采用平板稀释法研究了湿地松幼苗1 a中微生物根系数量的变化规律,为合理的生物防治时期提供科学依据。结果表明:湿地松苗圃土壤中存在着大量的微生物。湿地松幼苗根系的生长和发展可以大大促进其周围微生物的生长,受湿地松根系生长和环境变化等因素的影响,在松苗移栽后的几个月内,根际细菌和真菌的种群数量迅速增加,细菌比真菌的种群增长速度要快。利用生物防治细菌进行苗木猝倒病防治的最佳时期应该是在芽苗移栽后1个月以内。     

Estimating “autotrophic” belowground respiration in spruce and beech forests: decreases following girdling

Seasonal fluxes of CO₂ from soil and the contribution of autotrophic (root + mycorrhizal) to total soil respiration (SR) were estimated for a mixed stand of European beech (Fagus sylvatica) and Norway spruce (Picea abies) in Central Europe. Mature trees of each species were girdled in August 2002 to eliminate carbohydrate allocation to roots. SR was measured at distances of 0.5, 1.0, and 1.5/2.0 m from the bole of each tree at 1–2 weeks intervals throughout the fall of 2002 and monthly during the spring and summer of 2003. The contribution of roots and mycorrhizae to total SR was estimated by the decrease in SR compared to ungirdled control trees to account for seasonal patterns evident in controls. SR decreased with soil temperature in the fall 2002 and increased again in 2003 as soil warmed. During most of the study period, SR was strongly related to soil temperature. During the dry summer of 2003, however, SR appeared to be uncoupled from temperature and was strongly related to soil water content (SWC). Mean rates of SR in beech and spruce control plots as well as root densities did not show a clear pattern with distance from the bole. SR decreased to levels below controls in beech within a few days after girdling, whereas spruce did not show a significant decrease until October 2002, 6 weeks after girdling. In both beech and spruce, decreased SR in response to girdling was greatest closest to the bole, possibly reflecting increased mycorrhizal activity close to the bole. Autotrophic respiration was estimated in beech to be as much as 50% of the total SR in the stand. The contribution of autotrophic respiration was less certain for spruce, although close to the bole, the autotrophic fraction may contribute to total SR as much as in beech. The large fraction of autotrophic respiration in total SR requires better understanding of tree level stresses that affect carbon allocation below ground.     

质量平衡法估测树干呼吸的理论与应用

介绍质量平衡法的理论、估测方法及其应用,并对其进行评价.质量平衡理论认为:一段树干组织产生的CO2,应该是CO2通量的总和,包括通过树皮向外扩散的CO2释放通量、该段树干液流中的CO2运输通量(流入和流出液流的CO2浓度之差)及液流中的CO2储存通量(液流中CO2浓度在时间上的变化量).应用质量平衡法测定树干呼吸的关键是要估测树干内部的CO2通量,即液流中CO2的储存、运输和扩散.对于液流中CO2的估测主要有2种方法:1)用仪器直接测定木质部液流中的CO2浓度;2)通过测定树干液流停止流动或相对很低时(夜间)树干的CO2释放通量与液流流动时(白天)树干CO2释放通量的差值,间接估测木质部液流中CO2浓度.质量平衡方法提供了一个更为精确地估测木本组织呼吸的方法,其结果更为合理.     

杉木人工林不同发育阶段土壤微生物数量及其生物量的变化

土壤微生物参与土壤中多种生物化学反应,如矿化-同化、氧化-还原等,是植物营养转化、有机碳代谢及污染物降解的驱动力,在土壤肥力演变,尤其是养分循环中具有重要意义。土壤微生物生物量是指除了植物根系和体积大于5×103μm3的土壤动物以外的土壤中所有活的有机体的量(Paulet a     

不同利用强度下草原土壤微生物的生物量和数量的动态研究

以内蒙古克什克腾旗西部的典型草原为研究对象,根据对草原利用强度的不同,将其划分三个不同区域,研究了各区域土壤中微生物数量、微生物生物量和土壤呼吸强度的季节动态以及利用强度对他们的影响.结果表明:微生物数量、微生物生物量以及土壤的呼吸作用强度均有较明显的季节性变化,且峰值都出现在8月份.三者之间具有极显著的正相关关系;轻...     

磺酰脲类除草剂的降解机制及代谢产物的研究进展

磺酰脲类除草剂是一类高效,低毒和高选择性的除草剂,该类除草剂能有效防除阔叶杂草,其中有些品种对禾本科杂草也有一定的抑制作用。但同时因其用量低、对哺乳动物低毒以及独特的除草活性等特点而得到广泛应用。因此,了解磺酰脲类除草剂在土壤中的环境行为及归趋对于其科学合理使用、防止作物药害和保护农业生态环境具有非常重要的意义。根据笔者对磺酰脲类除草剂的深入研究,并总结归纳国内外的相关文献报道,对磺酰脲类除草剂的降解机制及其代谢产物的研究进行了综述,最后展望了磺酰脲类除草剂未来的发展趋势。