苹果园土壤呼吸的变化及生物和非生物因素的影响

了解果园土壤呼吸变化及其影响因素,有利于深入理解退耕还果条件下黄土高原地区土壤碳源汇功能.在长武农田生态系统国家野外站,以盛产期果园(2000年建成)为对象,利用土壤碳通量测量系统(Li-COR,Lincoln,NE,USA)于2011、2012年监测了果树冠幅下距树干不同距离处土壤呼吸、土壤水分和温度变化,分析了土壤呼吸的时空变化及其影响因素.结果表明:①土壤呼吸速率随着距树干距离延长而降低.与2 m处相比,0.5 m处土壤累积呼吸量2011年提高20%,2012年提高31%;0.5 m和2 m处土壤呼吸的温度敏感性(Q10)2011年相应依次为1.79和1.56,2012年依次为1.79和1.38.②距树干2 m处温度和水分稍高于0.5 m处,但差异不显著(P>0.05).土壤呼吸与土壤温度均呈显著的指数关系,而与土壤水分的相关性不显著.温度变化可解释土壤呼吸的季节性变化,但并不能解释距离树干不同处的差异.③距离树干不同位置处的根系密度差异是影响果园土壤呼吸空间变化及其温度敏感性的重要生物因素;④冠幅下土壤呼吸的变异系数为23%~31%.估算果园土壤呼吸需考虑其距离树干的空间差异性.     

MODELING THE EFFECT OF BRUSH CONTROL ON RANGELAND WATER YIELD1

ABSTRACT: With the increase in water demand in Texas, attention has turned to improving water yield by brush control on rangeland watersheds. Several hydrologic models have been developed for either farmland or rangeland. However, none of the models were specifically developed to assess the impact of brush control on rangeland water yield. Yet, modeling the impact of brush control on water yield needs to be considered if alternative techniques are to be compared. Two models, Ekalaka Rangeland Hydrology and Yield Model (ERHYM-II) and Simulator for Water Resources on Rural Basins (SWRRB) were selected. The Soil Conservation Service curve number (SCS-CN) method is used in both models to predict surface runoff from each rainfall event. The major differences between the ERHYM-II and SWRRB models are the evapotranspiration, soil water routing, and plant growth components. The models were evaluated on brush-dominated and chemically and mechanically brush-controlled range watersheds in Texas. Results indicated that both models were capable of simulating soil water and water yield from brush dominated and chemically brush-controlled range watersheds. The models were not able to predict water yield from the mechanically brush-controlled (root plowed) watershed with acceptable accuracy. The depressions that were caused by root plowing stored surface runoff and reduced water yield from the watershed. Information about the size of depressions was not available for further model evaluation.     

水葫芦根系对苯的吸附过程研究

对苯在水葫芦根系的吸附过程进行模拟研究结果表明：新鲜水葫芦根系对苯不仅具有吸附作用，而且还具有吸收或根际微生物降解等作用；水葫芦根系吸附苯的初始速率与浓度符合一级反应动力学；平衡吸附量与苯溶液浓度成正比；吸附过程可用Langmuir公式表示的单分子层吸附模型描述。     

Root Exudates Impact on Phenanthrene Availability

In order to improve and optimize phytoremediation of PAH we propose to focus on the rhizospheric processes controlling PAH degradation. In this paper the effect of root exudates on PAH availability is studied. Model organic compounds (malic acid, malonic acid and EDTA) representing root exudates have been tested for their effect on phenanthrene sorption on a reference non polluted agricultural soil material. Phenanthrene adsorption isotherms were first obtained with batch experiments. Results showed linear isotherms and phenanthrene sorption was enhanced as the concentration of organic compounds in the solution increased. Column leaching experiments were then used to simulate the effect of root exudation following the soil pollution. Inlet solutions containing the different organic acids used were flowed through the column containing the artificially polluted soil material. Elution curves showed that the phenanthrene was less easily eluted when the solution injected contained the organic acids. However, magnitude of the phenomena did not fit with adsorption constants obtained in batch experiments. Phenanthrene desorption appeared limited by sequestration but organic acids seemed able to partially disturb the soil material structure to limit the sequestration effect.     

Competition of the active roots of Cassia siamea Lam. and Zea mays L.(cv.Katumani Composite B) in an alley cropping trial in semi arid Kenya

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论葛属植物的开发及综合利用前景

综述了国内外葛根开发利用的现状和动向,介绍了葛属植物化学成份的研究进展及其含量测定方法,以及葛根产品在医药、食品等行业中的应用及市场前景。     

重金属对西红柿种子发芽与根伸长的抑制效应

测定了水溶液和4种土壤中铜、锌、铅、镉单一污染对西红柿种子发芽与根伸长抑制率以及草甸棕壤条件下重金属复合污染的生态效应.结果表明,重金属对西红柿根伸长抑制率均明显大于对种子发芽抑制率.土壤重金属明显低于水体重金属对西红柿根伸长的抑制.抑制率大小排列为红壤>>草甸棕壤>栗钙土>暗棕壤.铜、锌、铅、镉对西红柿根伸长抑制率与土壤有机质、土壤凯氏氮、全钾含量显著线性负相关(P=0.05);与土壤pH值和土壤全磷含量线性不相关(P=0.05).重金属复合污染对西红柿根伸长表现为协同作用和拮抗作用.     

长白山不同生态系统地下部分生物量及地下C贮量的调查

论文在收集已有资料的基础上,补充调查了长白山自然保护区中沿不同海拔高度形成的不同森林生态系统的细根生物量和一些森林类型的根系总生物量,并且对自然环境因子对根系生物量的影响进行了相关分析。研究表明,由高海拔到低海拔(岳桦林、苔藓岳桦暗针叶林、暗针叶林过渡带、苔藓红松暗针叶林、红松针阔混交林)树木细根(<2mm)生物量分别是458.92gm^-2、537.42gm^-2、390.35gm^-2、397.25gm^-2和660.21gm^-2;根系总生物量分别是2578.00gm^-2、2794.00gm^-2、2680.00gm^-2、3459.25gm^-2和5155.00gm^-2。分别对细根生物量和根系总生物量与降水量和活动积温之间进行相关性分析时,发现细根生物量与不同海拔高度的活动积温和降水量没有明显的相关性;而根系生物量与这些因子存在着指数相关关系。该研究同时对不同海拔高度根系中的C、N含量和土壤中有机质的含量进行了分析和测定。结合已有的倒木和凋落物的资料,估算了长白山自然保护区中沿不同海拔高度形成的不同森林生态系统地下C的贮量。在长白山自然保护区内,由高海拔到低海拔,林地C贮量分别是15493.88gm^-2、21005.74gm^-2、19819.24gm^-2、14232.51gm^-2和7344.02gm^-2。     

pH影响下小麦根吸附极性有机物的行为研究

文章以标准纤维素为对照吸附剂,以菲为对照吸附质,采用批量平衡振荡法进行吸附实验,研究不同pH条件下,小麦根吸附极性污染物(2,4-二氯苯酚和硝基苯)的行为差异。结果表明:污染物吸附以疏水性分配为主,吸附系数(K_d)值随化合物疏水性的增强而增强;非解离型极性污染物(硝基苯)的吸附与疏水性污染物(菲)类似,吸附等温线呈线性,相关系数(R²)均大于0.98,同时pH对吸附的影响无显著性差异(P>0.05);解离型极性污染物(2,4-二氯苯酚)的吸附随pH增加而降低,仅在pH 5.0时呈现吸附线性,在pH 7.0和8.0时均呈非线性,等温线逐渐向浓度轴弯曲,这源于疏水作用以及解离的2,4-二氯苯酚与吸附剂之间静电作用的共同影响。根的吸附能力大于纤维素,这与根中含有类脂物质有关。     

Methylopila sp.SD-1与大豆联合修复苯磺隆污染土壤

分离得到1株苯磺隆降解菌株SD-1,根据表型、生理生化特征及16S rRNA基因序列分析,将其鉴定为Methylopila sp.SD-1,为首次报道能够降解苯磺隆的Methylopila属菌株,其在4d内完全降解50mg/L苯磺隆,最适降解温度、pH值分别为30℃和7.0,降解中间产物对大豆的毒性显著降低.大豆根系分泌物能促进菌株SD-1的生长,培养5d,菌株SD-1的数量由1.0×10⁷CFU/mL增至6.7×10⁷CFU/mL.分泌物中含有16种氨基酸,菌株SD-1对其中的Asp、Glu和Phe表现出明显的趋化性.接种菌悬液至苯磺隆污染土壤（3mg/kg）并种植大豆幼苗,培养4d,菌株SD-1依赖趋化性向大豆根系运动并定殖,存活率提高,根际土壤中苯磺隆的降解率相较于未种植大豆的处理提高36.0%.