尽管近年来中国氮(N)沉降水平逐渐趋于稳定,但中国东南地区N沉降相比于其他地区仍处于较高水平。N沉降对陆地生态系统碳循环过程的影响不容忽视。微生物碳利用效率(CUE)是指微生物将吸收的碳转化为生物量碳的效率,高微生物CUE意味着高...尽管近年来中国氮(N)沉降水平逐渐趋于稳定,但中国东南地区N沉降相比于其他地区仍处于较高水平。N沉降对陆地生态系统碳循环过程的影响不容忽视。微生物碳利用效率(CUE)是指微生物将吸收的碳转化为生物量碳的效率,高微生物CUE意味着高土壤有机碳存储潜力。因此,探究N沉降背景下微生物CUE的变化将有助于进一步认识陆地生态系统土壤碳存储的变化。然而,目前关于N沉降下微生物群落结构的变化如何影响微生物CUE鲜有报道。在福建省泉州市戴云山国家级自然保护区的罗浮栲林通过N添加模拟N沉降。实验共包括三个N添加处理:对照(CT,+0 kg hm^(-2)a^(-1))、低氮(LN,+40 kg hm^(-2)a^(-1))和高氮(HN,+80 kg hm^(-2)a^(-1))。测定不同处理土壤基本理化性质、微生物生物量、酶活性和CUE,并使用高通量测序对微生物群落结构和多样性进行测定。结果表明,N添加显著影响微生物CUE,随着N添加水平的增加,CUE逐渐增加;相反,土壤pH、可提取有机碳(EOC)和微生物生物量碳(MBC)均呈现下降趋势。N添加对土壤微生物群落α多样性总体上无显著影响。非度量多维度尺度(NMDS)分析表明,N添加显著改变了微生物的群落结构。尤其对于真菌而言,不同N添加处理的真菌群落明显分开为三簇。微生物CUE分别与土壤pH、EOC和真菌NMDS1呈显著的负相关关系,与矿质氮含量呈现显著正相关关系。随机森林分析表明,N添加下影响微生物CUE的类群主要是富营养菌(如变形菌门和子囊菌门)。研究表明N添加下,微生物CUE不仅受土壤养分有效性和pH的调控,同时还受土壤微生物群落结构的影响。未来进一步探究N添加下土壤微生物关键类群的变化可能有助于揭示森林生态系统碳存储过程。展开更多
A novel method for on-site determination of trace iron was developed using membrane preconcentration and spectrophotometric detection. Fe(Ⅱ)-ferrozine complex was reacted with cetyltrimethylammonium bromide (CTAB) to...A novel method for on-site determination of trace iron was developed using membrane preconcentration and spectrophotometric detection. Fe(Ⅱ)-ferrozine complex was reacted with cetyltrimethylammonium bromide (CTAB) to form a Fe(Ⅱ)-ferrozine-CTAB paired compound, which was collected on a membrane by filtration under vacuum. The membrane was immersed in 2 mL of ethanol-nitric acid and the absorbance of the solution measured for quantitative analysis. Various factors affecting the iron collection and determination were investigated. With different sample preconcentration volumes, the range of determination was broadened to 0.5-120 g/L. The detection limit of this method reached 0.19 g/L and the recoveries were between 97.2 and 109% when the concentration enrichment was about 45. The relative standard deviation (n = 7) was 1.9% for samples containing 10 g/L Fe. Twelve seawater samples were analyzed on-site using the proposed method, and two were also analyzed in inductively coupled plasma mass spectrometry. No significant difference was shown between the two methods by the Student's t-test. The method has also been used on-site for iron enrichment experiments with phytoplankton and concluded to be simple, accurate and inexpensive.展开更多
文摘尽管近年来中国氮(N)沉降水平逐渐趋于稳定,但中国东南地区N沉降相比于其他地区仍处于较高水平。N沉降对陆地生态系统碳循环过程的影响不容忽视。微生物碳利用效率(CUE)是指微生物将吸收的碳转化为生物量碳的效率,高微生物CUE意味着高土壤有机碳存储潜力。因此,探究N沉降背景下微生物CUE的变化将有助于进一步认识陆地生态系统土壤碳存储的变化。然而,目前关于N沉降下微生物群落结构的变化如何影响微生物CUE鲜有报道。在福建省泉州市戴云山国家级自然保护区的罗浮栲林通过N添加模拟N沉降。实验共包括三个N添加处理:对照(CT,+0 kg hm^(-2)a^(-1))、低氮(LN,+40 kg hm^(-2)a^(-1))和高氮(HN,+80 kg hm^(-2)a^(-1))。测定不同处理土壤基本理化性质、微生物生物量、酶活性和CUE,并使用高通量测序对微生物群落结构和多样性进行测定。结果表明,N添加显著影响微生物CUE,随着N添加水平的增加,CUE逐渐增加;相反,土壤pH、可提取有机碳(EOC)和微生物生物量碳(MBC)均呈现下降趋势。N添加对土壤微生物群落α多样性总体上无显著影响。非度量多维度尺度(NMDS)分析表明,N添加显著改变了微生物的群落结构。尤其对于真菌而言,不同N添加处理的真菌群落明显分开为三簇。微生物CUE分别与土壤pH、EOC和真菌NMDS1呈显著的负相关关系,与矿质氮含量呈现显著正相关关系。随机森林分析表明,N添加下影响微生物CUE的类群主要是富营养菌(如变形菌门和子囊菌门)。研究表明N添加下,微生物CUE不仅受土壤养分有效性和pH的调控,同时还受土壤微生物群落结构的影响。未来进一步探究N添加下土壤微生物关键类群的变化可能有助于揭示森林生态系统碳存储过程。
基金Supported by State Key Laboratory of Marine Environmental Science(MEL)Funds(No.MELRI1001)
文摘A novel method for on-site determination of trace iron was developed using membrane preconcentration and spectrophotometric detection. Fe(Ⅱ)-ferrozine complex was reacted with cetyltrimethylammonium bromide (CTAB) to form a Fe(Ⅱ)-ferrozine-CTAB paired compound, which was collected on a membrane by filtration under vacuum. The membrane was immersed in 2 mL of ethanol-nitric acid and the absorbance of the solution measured for quantitative analysis. Various factors affecting the iron collection and determination were investigated. With different sample preconcentration volumes, the range of determination was broadened to 0.5-120 g/L. The detection limit of this method reached 0.19 g/L and the recoveries were between 97.2 and 109% when the concentration enrichment was about 45. The relative standard deviation (n = 7) was 1.9% for samples containing 10 g/L Fe. Twelve seawater samples were analyzed on-site using the proposed method, and two were also analyzed in inductively coupled plasma mass spectrometry. No significant difference was shown between the two methods by the Student's t-test. The method has also been used on-site for iron enrichment experiments with phytoplankton and concluded to be simple, accurate and inexpensive.
