Volume 37 Issue 4
Jul.  2020
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HE Dongmei, JIANG Hao, ZHU Yayun, LU Xiaozhen, WANG Lei. Characteristics and influencing factors of soil microbial biomass carbon content at different succession stages of coastal wetlands in Jiangsu Province[J]. Journal of Zhejiang A&F University, 2020, 37(4): 623-630. doi: 10.11833/j.issn.2095-0756.20190565
Citation: HE Dongmei, JIANG Hao, ZHU Yayun, LU Xiaozhen, WANG Lei. Characteristics and influencing factors of soil microbial biomass carbon content at different succession stages of coastal wetlands in Jiangsu Province[J]. Journal of Zhejiang A&F University, 2020, 37(4): 623-630. doi: 10.11833/j.issn.2095-0756.20190565

Characteristics and influencing factors of soil microbial biomass carbon content at different succession stages of coastal wetlands in Jiangsu Province

doi: 10.11833/j.issn.2095-0756.20190565
  • Received Date: 2019-09-25
  • Rev Recd Date: 2020-03-01
  • Available Online: 2020-07-21
  • Publish Date: 2020-07-21
  •   Objective  The objective is to explore distribution characteristics and seasonal variations of soil microbial biomass carbon (MBC) content at different succession stages of coastal wetlands in Jiangsu Province, and to reveal its main influencing factors.  Method  Five typical succession stages of coastal wetlands in Jiangsu were selected as the research objects, including coastal mudflats, Spartina auglica wetland, Suaeda glauca wetland, Phragmites australis wetland, and Robinia pseucdoacacia forest. The distribution characteristics of soil MBC at the different succession stages, the effects of vegetation succession, soil layer and season on MBC, the relationship between soil MBC and soil physical and chemical properties were analyzed. The key factors affecting soil MBC in coastal wetlands were discussed.  Result  Soil MBC content ranged from 116.91 to 326.18 mg·kg−1, with a significant difference between different succession stages, but the distribution trend was not consistent with the succession direction. The highest was Sp. auglica, followed by P. australis, coastal mudflats, Su. glauca, and R. pseucdoacacia. In 0−10 cm soil depth, soil MBC content in Sp. auglica wetland was significantly higher than that of other succession stages in four seasons. Soil MBC content at different succession stages first increased and then decreased with variation of seasons in the three soil layers, reaching its peak in autumn but lower in spring or winter. Soil MBC in coastal wetlands was significantly affected by seasons and succession stages, among which the seasonal factors had the largest impact, accounting for 32.29%. There existed a significant positive correlation between soil MBC content and total organic carbon, total nitrogen and soil moisture content, but a significant negative correlation with soil pH.  Conclusion  Vegetation succession and seasons are the main factors affecting the distribution and dynamic characteristics of soil MBC in coastal wetlands, among which seasonal factors have the greatest influence, and soil organic matter, moisture content and pH are the key factors that directly affect soil microbial activity. [Ch, 1 fig. 2 tab. 35 ref.]
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Characteristics and influencing factors of soil microbial biomass carbon content at different succession stages of coastal wetlands in Jiangsu Province

doi: 10.11833/j.issn.2095-0756.20190565

Abstract:   Objective  The objective is to explore distribution characteristics and seasonal variations of soil microbial biomass carbon (MBC) content at different succession stages of coastal wetlands in Jiangsu Province, and to reveal its main influencing factors.  Method  Five typical succession stages of coastal wetlands in Jiangsu were selected as the research objects, including coastal mudflats, Spartina auglica wetland, Suaeda glauca wetland, Phragmites australis wetland, and Robinia pseucdoacacia forest. The distribution characteristics of soil MBC at the different succession stages, the effects of vegetation succession, soil layer and season on MBC, the relationship between soil MBC and soil physical and chemical properties were analyzed. The key factors affecting soil MBC in coastal wetlands were discussed.  Result  Soil MBC content ranged from 116.91 to 326.18 mg·kg−1, with a significant difference between different succession stages, but the distribution trend was not consistent with the succession direction. The highest was Sp. auglica, followed by P. australis, coastal mudflats, Su. glauca, and R. pseucdoacacia. In 0−10 cm soil depth, soil MBC content in Sp. auglica wetland was significantly higher than that of other succession stages in four seasons. Soil MBC content at different succession stages first increased and then decreased with variation of seasons in the three soil layers, reaching its peak in autumn but lower in spring or winter. Soil MBC in coastal wetlands was significantly affected by seasons and succession stages, among which the seasonal factors had the largest impact, accounting for 32.29%. There existed a significant positive correlation between soil MBC content and total organic carbon, total nitrogen and soil moisture content, but a significant negative correlation with soil pH.  Conclusion  Vegetation succession and seasons are the main factors affecting the distribution and dynamic characteristics of soil MBC in coastal wetlands, among which seasonal factors have the greatest influence, and soil organic matter, moisture content and pH are the key factors that directly affect soil microbial activity. [Ch, 1 fig. 2 tab. 35 ref.]

HE Dongmei, JIANG Hao, ZHU Yayun, LU Xiaozhen, WANG Lei. Characteristics and influencing factors of soil microbial biomass carbon content at different succession stages of coastal wetlands in Jiangsu Province[J]. Journal of Zhejiang A&F University, 2020, 37(4): 623-630. doi: 10.11833/j.issn.2095-0756.20190565
Citation: HE Dongmei, JIANG Hao, ZHU Yayun, LU Xiaozhen, WANG Lei. Characteristics and influencing factors of soil microbial biomass carbon content at different succession stages of coastal wetlands in Jiangsu Province[J]. Journal of Zhejiang A&F University, 2020, 37(4): 623-630. doi: 10.11833/j.issn.2095-0756.20190565
  • 土壤有机碳对大气温室气体的贡献主要来源于土壤活性有机碳的分解[1-3]。土壤活性碳是土壤碳库中能直接参与土壤生物化学过程、易被土壤微生物分解利用、对植物养分供应有直接作用的有机碳,虽然只占土壤总有机碳的很小比例,但是由于其易分解和周转快,能快速地反映外界干扰和环境因素对土壤有机质造成的微小变化[4-5]。因此,土壤活性有机碳常作为响应土地利用变化、植被演替过程、环境变化和气候变化等的敏感指标[6],对预测未来全球气候变化具有重要作用。微生物生物量碳(microbial biomass carbon,MBC)是活性有机碳库的一个重要组成部分,常用来表征土壤活性有机碳库的变化。土壤MBC的含量受土壤温度、pH、含水量、养分含量的共同影响,而这些因子通常随着季节变化而变化,因此土壤MBC的变化通常呈现一定的季节变化规律[79]。目前,关于土壤微生物生物量碳及其影响因素已开展了较多研究,主要集中在农田、森林、草地以及淡水湿地生态系统[10-13],而对于滨海湿地生态系统的相关研究还比较缺乏。在滨海湿地生态系统中,土壤MBC通常会受气候、土壤和植被等因子的影响。植被演替是滨海湿地形成和演变的重要标志,伴随着植被演替进程,物种组成发生变化,有机质来源的地表凋落物和地下根系分泌物类型也发生相应的变化,从而影响土壤中MBC含量[14-15]。江苏滨海湿地位于北亚热带向南暖温带的过渡地带,湿地面积达100 万hm2,其中淤泥质海滩面积约41.56 万hm2,是中国淤泥质滨海湿地的重要组成部分。随着滩涂的逐渐淤积抬升,水分和含盐量则逐渐降低,江苏滨海湿地的环境条件呈现出了有序变化,植被呈明显的条带分布。植被分布由海向陆分布为光滩、大米草Spartina anglica、碱蓬Suaeda glauca、芦苇Phragmites australis和刺槐Robinia pseudoacacia群落。对江苏滨海湿地不同演替阶段土壤MBC的质量分数和季节动态进行研究,对揭示滨海湿地植被演替对土壤碳库动态的影响以及科学预测滨海湿地土壤有机碳在大气碳循环中的作用都具有重要的意义。

    • 研究区位于江苏北部,黄海和东海交汇处,江苏大丰国家级麋鹿Elaphurus davidianus保护区内(33°05′N,120°44′E)。该区地处北亚热带向暖温带的过渡地带,受海洋和大陆性气候的影响,具有明显的过渡性、海洋性和季风性。四季分明,气温适中,雨量充沛,年均气温为14.1 ℃,年均降水量为1 047.5 mm,降水多集中在夏季。大丰国家级麋鹿保护区为典型的淤泥质滩涂湿地,原始植被类型简单,植被演替序列相对完整,由海向陆植被演替阶段依次为光滩、大米草群落、碱蓬群落、芦苇群落和刺槐群落。

    • 以空间代替时间的方法,在研究区沿与海岸线垂直的方向,自海向陆随机设置3条约30 m宽的样带,样带之间的空间分隔距离在300~500 m。在样带上自海向陆分布有光滩、大米草、碱蓬、芦苇和刺槐群落共5个演替阶段;同时,在每个对应的演替阶段分别设置3个5 m×5 m的样方,每个样方间距离不小于50 m。在每个样方内随机选取3个点挖取土壤剖面,按0~10、10~25和25~40 cm共3个土层进行分层采样。采集的土壤样品用自封袋装好标记后,迅速带回实验室,剔除肉眼可见的根系、动物、植物残体和石砾等,并将土壤样品分成2份。一份鲜土于4 ℃下冷藏,用于测定土壤MBC及土壤含水量;另一份土样经风干处理后,磨细过筛,用于土壤理化性质分析。

    • 土壤MBC测定:采用氯仿熏-硫酸钾浸提法[6],熏蒸和未熏蒸的样品分别用0.5 mol·L−1的硫酸钾溶液浸提30 min,用岛津TOC-VCPH仪测定浸提液有机碳质量分数。土壤MBC质量分数wMBC$= $EC/0.45。其中:EC为熏蒸与未熏蒸土壤样品浸提液中有机碳质量分数的差值,mg·kg−1;0.45为MBC浸提系数。

    • 采用LY/T 1210~1275−1999《森林土壤分析方法》[16]测定土样基本理化性质。重铬酸钾外加热法测定土壤总有机碳(SOC);元素分析仪(ElementarVarioEL,德国)测定总氮(TN);玻璃电极 (土水质量比为1.0∶2.5)测定土壤pH;烘干恒量法(105 ℃)测定土壤含水率;环刀法测定容重。

    • 利用单因素和多因素方差分析方法分析植被演替、季节和土层因素对土壤MBC的影响;运用Pearson相关系数法分析MBC与土壤理化因子的相关性,数据分析软件为SPSS 20.0。

    • 江苏滨海湿地不同演替阶段土壤MBC在0~40 cm土层的质量分数分别为:刺槐群落116.91~254.61 mg·kg−1,碱蓬群落168.12~276.19 mg·kg−1,芦苇群落219.45~290.76 mg·kg−1,大米草群落211.37~380.14 mg·kg−1,光滩117.00~326.18 mg·kg−1。平均质量分数从大到小依次为大米草、芦苇、光滩、碱蓬、刺槐群落,未表现出沿演替方向的变化趋势,其中碱蓬和刺槐群落显著低于其他3个演替阶段(图1)。0~10 cm土层,各演替阶段土壤MBC质量分数范围为157.66~380.14 mg·kg−1,在夏季、秋季和冬季从大到小均为大米草、芦苇、碱蓬、刺槐群落。其中,夏季大米草群落土壤MBC质量分数显著高于芦苇、碱蓬和刺槐群落;秋季,刺槐和碱蓬群落土壤MBC质量分数显著低于大米草群落和光滩;冬季,大米草和芦苇群落土壤MBC质量分数显著高于刺槐和碱蓬群落。10~25 cm土层,各演替阶段土壤MBC质量分数范围为140.73~357.12 mg·kg−1,土壤MBC质量分数在春季和夏季从大到小依次为芦苇、大米草、光滩、碱蓬、刺槐群落;秋季,刺槐和碱蓬群落土壤MBC质量分数均显著低于其他3个演替阶段。25~40 cm土层,各演替阶段土壤MBC质量分数范围为116.91~350.48 mg·kg−1;春季,刺槐林土壤MBC质量分数显著低于芦苇和大米草群落;秋季,刺槐群落显著低于其他演替阶段;冬季,刺槐和碱蓬群落土壤MBC质量分数显著低于大米草群落和光滩。

      Figure 1.  Seasonal variations of soil MBC contents under different succession stages

    • 图1可以看出:不同演替阶段的土壤MBC质量分数在3个土层的季节变化趋势一致,均随季节先增加再下降,在秋季达到峰值;除芦苇群落外,各演替阶段土壤MBC质量分数均呈现出明显的季节变化规律。在0~10 cm土层,刺槐群落土壤MBC质量分数从大到小依次为秋季、夏季、春季、冬季;碱蓬群落土壤MBC质量分数在冬季显著低于夏季、秋季;大米草群落土壤MBC质量分数的季节变化表现为秋季最高,春季最低;光滩土壤MBC质量分数在春季、冬季显著低于夏季、秋季。10~25 cm土层,各演替阶段土壤MBC质量分数随季节的变化趋势与0~10 cm层一致,但是变化幅度不同;刺槐和碱蓬群落土壤MBC质量分数秋季较高,春季显著较低;大米草群落呈现出了明显的季节差异性,差异性从高到低依次为秋季、冬季、夏季、春季;光滩土壤MBC质量分数差异性表现为秋季和冬季显著高于春季和夏季。25~40 cm,各演替阶段土壤MBC质量分数的季节变化趋势与其他土层一致;刺槐群落土壤MBC质量分数的季节从高到低依次为秋季、冬季、夏季、春季;碱蓬群落土壤MBC质量分数在秋季最高,其他季节变化不明显;大米草群落和光滩土壤MBC质量分数在秋季和冬季显著高于春季和夏季。

    • 利用多因素方差分析可得出:本研究中植被演替和季节对土壤MBC质量分数具有极显著影响(P<0.01),而土层深度对土壤MBC质量分数的影响较小且不显著(表1)。从3个影响因素间的交互作用看,季节分别与演替和土层的交互作用对土壤MBC质量分数均具有极显著影响(P<0.01)。表1中分布值可表示不同因素对土壤MBC质量分数的影响效应大小。根据分布值数据可知,季节因素对土壤MBC质量分数的影响最大,影响效应占32.29%;其次是演替因素的影响,效应占26.23%;季节和土层的交互作用对土壤MBC质量分数的影响效应占7.05%;季节与演替的交互作用对土壤MBC的影响效应相对较弱,占5.86%。

      影响因素分布值/%P
      植被演替26.230.000
      土层 0.910.087
      季节32.290.000
      植被演替×土层 0.960.728
      植被演替×季节 5.860.003
      土层×季节 7.050.000
      植被演替×土层×季节 4.840.348

      Table 1.  Effects of vegetation succession, soil layer and season on soil MBC contents

    • 滨海湿地土壤理化性质也是影响土壤MBC质量分数的主要因素,本研究中滨海湿地土壤基本理化性质见文献[17]。本研究分析了不同演替阶段土壤MBC质量分数与土壤理化性质间的相关性(表2)。结果显示:土壤MBC质量分数与土壤总有机碳和总氮之间呈显著(P<0.05)的正相关关系;土壤pH与MBC质量分数之间呈负相关,且相关性达极显著水平(P<0.01);土壤MBC质量分数与土壤容重呈显著的负相关关系(P<0.05),而与土壤含水率表现出极显著的正相关关系(P<0.01)。本研究中C/N与土壤MBC质量分数的相关性不显著(P>0.05)。

      项目土壤
      有机碳
      总氮C/NpH容重含水率
      MBC0.187*0.173*0.062−0.225**−0.190*0.461**
       说明:*表示显著相关水平(P<0.05);**表示极显著相关水平   (P0.01)

      Table 2.  Pearson correlation coefficients (r-value) between MBC and physic-chemical factors of soil

    • 不同演替阶段由于植物群落不同,地表凋落物、地下根系分泌物以及土壤微生物种类也存在差异,从而影响土壤MBC的质量分数[18]。不同演替阶段土壤MBC质量分数在不同土层从高到低均依次为大米草群落、光滩或芦苇群落、碱蓬群落、刺槐群落。杨文英等[11]研究杭州湾滩涂湿地4种典型植被的活性有机碳质量分数发现:不同植被土壤MBC质量分数从高到低依次为光滩、海三棱藨草Scirpus mariqueter群落、互花米草Spartina alterniflora群落、芦苇群落;孔小琳等[19]研究胶州湾滨海湿地不同群落土壤微生物生物量碳变化得出从高到低依次为碱蓬群落、互花米草群落、芦苇群落、光滩,均与本研究的结果不一致。表明在不同区域环境下,由于土壤因子、气候因子以及凋落物等共同影响,土壤微生物有其独特的分布规律[20]。本研究中大米草群落的土壤MBC质量分数在不同土层均显著大于其他演替阶段。YANG等[21]研究了江苏盐城的互花米草、碱蓬、芦苇及光滩的土壤有机碳组分,同样发现互花米草土壤MBC质量分数较高。一方面,大米草作为一种入侵植物,具有较强的生产力和繁殖力,其大量的凋落物和地下根系分泌物促进了土壤有机碳输入,为土壤微生物提供了丰富的代谢底物,从而使土壤MBC的质量分数增加[22-24],这与本研究中土壤MBC与土壤有机碳质量分数具有正相关关系的结论一致;另一方面大米草群落所处的演替阶段容易受潮汐作用和干湿交替的影响,土壤含水率能够刺激土壤微生物活性,从而增加土壤MBC质量分数[25]。张静等[12]研究表明:土壤含水率是影响土壤MBC质量分数的一个重要因素,在一定范围内,土壤含水率高可增强植物根系的活动能力,促进大量根系分泌物的产生,从而使土壤MBC质量分数增加,这与本研究中土壤含水率较高的大米草群落具有较高的土壤MBC质量分数相符合。可见,土壤有机质、土壤含水率、土壤pH等土壤理化因子都是影响不同演替阶段土壤MBC质量分数变化的关键因子。

    • 不同演替阶段的土壤MBC质量分数在3个土层均在秋季和冬季达到显著性差异。表明土壤MBC的动态变化是一个复杂过程,即使气候条件相同,不同植被下土壤MBC的季节变化也有差异。本研究中,除芦苇群落外,其他演替阶段土壤MBC质量分数均具有明显的季节变化规律,说明季节因素对不同演替阶段土壤MBC质量分数具有显著的影响。不同演替阶段不同土层土壤MBC质量分数的季节变化幅度不一致,但是均在秋季达到最大峰值,这与田舒怡等[18]的研究结果一致。土壤MBC质量分数在秋季最高,可能是由于秋季大量凋落物、衰老根系及碳水化合物由地上向地下转移,为微生物提供更多的能量[24];土壤MBC质量分数在植物开始生长的春季最低,可能是由于春季微生物活性以及凋落物分解速率较慢[26]

    • 植被演替、季节,以及植被演替和季节的交互作用均显著影响土壤MBC质量分数。植被演替对土壤MBC质量分数的影响主要是由于各演替阶段的植被组成不同,其凋落物质量和数量的差异会引起输入土壤的养分不同,进而影响土壤微生物活性;凋落物分解速率快,为土壤微生物提供的养分多,土壤微生物生物量则较大[27]。土壤MBC质量分数受季节与演替的交互影响,是由于季节变化通常会引起不同演替阶段植被生长节律和土壤微生物对养分吸收能力的改变,从而影响土壤MBC的质量分数[28]。本研究中土壤深度虽然对土壤MBC质量分数的影响不明显,但是土层与季节的交互作用却对土壤MBC质量分数存在显著影响,表明季节是影响土壤MBC的主导因子,且其影响在不同土层间存在差异。刘平等[26]研究渤海泥质海岸典型防护林土壤MBC季节动态,同样得到季节因素是影响土壤MBC质量分数变化的重要因素,且不同林分类型和不同土层,季节因素的影响作用存在差异。从植被演替、季节与土层及其之间的交互作用对土壤MBC质量分数的影响效应看,季节因素的影响效应所占比例最大,表明季节因素是影响滨海湿地土壤MBC质量分数最关键的因素。土壤MBC质量分数的季节动态是一个复杂的生物化学过程,可能受不同机制的驱动,季节变化通常能够引起地表凋落物、地下根系分泌物以及土壤有机质、温度、湿度、pH等理化因子的改变,从而综合影响土壤微生物活性,使土壤MBC质量分数表现出季节差异性[29]。本研究中土壤MBC质量分数随季节变化先增加后减少并在秋季达到最大值,这是由于冬季过渡到春季这段时间,温度上升缓慢,凋落物分解速率较慢,土壤中微生物可利用的有机质仍然较少,土壤MBC仍然较低[29];夏季雨水充足,土壤温湿度适宜,植物进入生长季,微生物活性逐渐增加,使土壤MBC增加[30];从夏季到秋季,虽然降雨量减少,土壤含水率下降,导致土壤微生物活性减弱,但是由于大量植物凋落物分解,为微生物提供了丰富的营养物质,使土壤中MBC继续增加[29];从秋季到冬季,随着气温的降低,微生物活性收到抑制,土壤中MBC减少[30]

    • 土壤性质是影响土壤MBC质量分数和分布的直接因素[26]。相关性分析显示:土壤MBC质量分数与土壤总氮和土壤有机碳均呈显著正相关,这与ZHOU等[31]的研究结果一致,表明土壤有机质是影响土壤MBC的重要因素,有机质含量高,能够为土壤微生物提供进行自身合成和代谢所需的碳、氮物质来源以及能量来源[32]。刘平等[26]同样得到渤海泥质海岸土壤MBC质量分数与土壤总氮和土壤有机碳具有极显著正相关关系的结论。也有部分研究结果显示:土壤MBC与土壤有机碳、全氮质量分数间的相关性不显著[32-33],研究结果的差异性可能是由于研究区空间尺度较大,受区域气候、土壤类型等因素的综合影响导致的[32]。本研究中土壤MBC质量分数与土壤pH、含水率成呈极显著相关,表明土壤pH和含水率都是影响滨海湿地土壤MBC质量分数的限制性因子[12]。土壤pH、含水率可直接影响土壤微生物活性,是调节土壤微生物活性的主要因子[34]。范志平等[35]研究辽东山地不同森林类型土壤有机碳季节动态及其驱动因子发现,土壤MBC质量分数与土壤pH呈显著线性正相关;张静等[12]和刘明慧等[24]研究发现:土壤含水率是土壤MBC等活性有机碳变化的主要驱动因子。

    • 江苏滨海湿地土壤MBC质量分数在不同演替阶段的分布从高到低依次为大米草群落、芦苇群落、光滩、碱蓬群落、刺槐群落,其分布规律与演替方向不一致。不同演替阶段不同土层土壤MBC质量分数的季节动态均表现为随季节先增加再下降的趋势,且在秋季达到最大峰值。江苏滨海湿地土壤MBC质量分数在不同土层无显著差异,但是受季节和植被演替的影响较显著,其中季节因素的影响效应占较大比例。土壤理化因子是影响滨海湿地土壤MBC质量分数的直接因素,其中土壤有机碳、土壤总氮、土壤含水率与土壤MBC质量分数具有显著正相关关系,而土壤pH与土壤MBC呈显著负相关,表明滨海湿地土壤有机质、土壤含水率、土壤pH都是影响土壤MBC质量分数的限制性因子。

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