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  中国水土保持科学   2021, Vol. 19 Issue (2): 27-32.  DOI: 10.16843/j.sswc.2021.02.004
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引用本文 

王谦, 李明蔚, 李强, 陈景玲, 杨喜田, 寇渊博, 张劲松. 基于栓皮栎幼苗叶绿素荧光参数的不同质地土壤干旱胁迫指标[J]. 中国水土保持科学, 2021, 19(2): 27-32. DOI: 10.16843/j.sswc.2021.02.004.
WANG Qian, LI Mingwei, LI Qiang, CHEN Jingling, YANG Xitian, KOU Yuanbo, ZHANG Jinsong. Drought stress indexes of soil with different texture based on chlorophyll fluorescence parameters of Quercus variabilis seedling[J]. Science of Soil and Water Conservation, 2021, 19(2): 27-32. DOI: 10.16843/j.sswc.2021.02.004.

项目名称

国家自然科学基金"基于气候空间上限列线的栓皮栎幼苗高温叠加干旱胁迫机制研究"(31370621),"番茄叶片低温胁迫气象指标的气候空间列线研究"(31071321)

第一作者简介

王谦(1963-), 男, 博士, 教授。主要研究方向:农林生态。E-mail:wangqianhau@163.com

通信作者简介

陈景玲(1964-), 女, 本科, 副教授。主要研究方向:农林气象。E-mail:chenjingling5@163.com

文章历史

收稿日期:2020-05-06
修回日期:2021-02-22
基于栓皮栎幼苗叶绿素荧光参数的不同质地土壤干旱胁迫指标
王谦 1, 李明蔚 1, 李强 1, 陈景玲 1, 杨喜田 1, 寇渊博 1, 张劲松 2     
1. 河南农业大学林学院, 450002, 郑州;
2. 中国林业科学院林业研究所, 100091, 北京
摘要:为了确定黄河小浪底不同土壤对栓皮栎幼苗的质地效应,在6个样点(A~F)采集土壤盆栽栓皮栎幼苗,测定不同土壤湿度下栓皮栎幼苗叶绿素荧光参数的变化,以最大量子效率Fv/Fm和实际量子产量Y(Ⅱ)开始下降和下降50%时的值为土壤干旱胁迫指示参数,确定干旱胁迫的土壤湿度指标,分析土壤的质地效应。结果表明:1)Fv/FmY(Ⅱ)随土壤湿度降低呈幂函数下降。2)6个样点Fv/FmY(Ⅱ)开始下降时的土壤湿度θk和下降50%时的土壤湿度θ50,方差分析表明6个样点θkθ50可分为2类。3)6个样点栓皮栎幼苗的干旱胁迫指标。A、B、C和D为:>13%无干旱,>10%~13%轻度干旱,>8%~10%中度干旱,>5%~8%重度干旱;E、F为:>19%无干旱,>15%~19%轻度干旱,>13%~15%中度干旱,>9%~13%重度干旱。4)θkθ50与土壤粒级的黏粒和粉粒相关性密切,与砂粒负相关。综上:土壤质地对栓皮栎幼苗的作用呈"反质地效应",即质地越细,土壤水分的有效性越差,土壤干旱的水分指标也越高;砂粒含量较高的土壤质地的土壤水分有效性好,土壤干旱的水分指标偏低。
关键词栓皮栎    干旱    叶绿素荧光    胁迫    质地效应    
Drought stress indexes of soil with different texture based on chlorophyll fluorescence parameters of Quercus variabilis seedling
WANG Qian 1, LI Mingwei 1, LI Qiang 1, CHEN Jingling 1, YANG Xitian 1, KOU Yuanbo 1, ZHANG Jinsong 2     
1. College of Forestry, Henan Agricultural University, 450002, Zhengzhou, China;
2. Research Institute of Forestry, Chinese Academy of Forestry, 100091, Beijing, China
Abstract: [Background] The drought stress index of Quercus variabilis is not perfect, and it can only be roughly divided into three levels: light, medium and heavy drought stress. In addition, it is not clear whether soil texture has a positive or negative effect on Q. variabilis seedlings. This work is to determine the texture effect of soil in the Xiaolangdi of the Yellow River on Q. variabilis seedlings photosynthesis and drought stress index. [Methods] Five different sample points(A, B, E, D and F) of soil and a soil sample point (C) in plain region were selected. 1-year old Q. variabilis seedlings were pot cultured.The pots were watered until saturated and then let dry naturely. Changes of chlorophyll fluorescence parameters of Q. variabilis seedling under different soil moisture were measured during the period. The chlorophyll fluorescence parameters of maximum quantum efficiency Fv/Fm and the actual quantum yield Y(Ⅱ) were used to analyze soil texture effect. The soil moistures of Fv/Fm and Y(Ⅱ) while starts decreasing and decreasing 50% were used as soil drought stress indices to analyze the differences among different soil texture types and then to determine the soil texture effect. [Results] 1) The changes of Fv/Fm and Y(Ⅱ) with the decrease of soil moisture content was simulated by power function, and the relationship coefficients of simulation were between 0.6 and 0.9. 2) The soil moistures θk of 6 sample points while Fv/Fm and Y(Ⅱ) started decreasing and θ50 while Fv/Fm and Y(Ⅱ) was decreasing 50% were determined. The significance test of ANOVA showed that the soil water stress indices of 6 sample points were divided into 2 categories, and passed the significance test of difference under the reliability of 0.05. The difference between A, B, D of sandy soil mountain land and C of plain area was not obvious. 3) Based on chlorophyll fluorescence parameters Fv/Fm and Y(Ⅱ), drought stress indexes of 6 sample points were obtained. The drought stress index of A, B, C and D was as follows: >13% no drought, >10%-13% mild drought, >8%-10% moderate drought, and >5%-8% severe drought. The drought stress index of E and F was: >19% no drought, >15%-19% mild drought, >13%-15% moderate drought, and >9%-13% severe drought. 4) θk and θ50 were closely correlated with clay and powder grains of soil grain size, and negatively correlated with sand grains. [Conculsions] The influence of soil texture on Q. variabilis seedlings soil moisture was "anti-texture effect", that is, the finer the soil texture is, the worse the soil water availability is, and higher the moisture index of soil under drought stress is higher. The higher the sand content is, the better the water availability is, and the lower the moisture index of soil drought is.
Keywords: Quercus variabilis    drought    chlorophyll fluorescence    stress    texture effect    

华北太行山石质山区土壤发育差异较大。有砂性和黏性的不同。在这个地区开展的科学研究,其结果必然因土壤质地不同而不同。土壤质地对不同植被的影响有“正、反质地效应”。“反质地效应”认为质地越黏,植物生产力越小[1-4]。“正质地效应”认为质地越粗树木死亡率越大[5-6]。土壤质地影响植物生长,而植物生长状况直接影响水土保持。有学者关注小尺度的土壤水分空间异质性[7-8],和不同质地土壤水对不同植被的影响[8],都是在研究土壤的质地效应。

栓皮栎(Quercus variabilis),壳斗科(Fagaceae)落叶乔木,是太行山区的主要水土保持树种。其生长也受到土壤质地效应影响。栓皮栎幼苗阶段死亡率高[9],需要研究死苗的原因,以降低造林的死苗率。一般认为死苗的外因是生境条件。生境条件包括光、温、水、土等环境因素。这些因素中土壤水缺乏导致的干旱胁迫是栓皮栎死苗的主要因素。所以,需要有不同质地土壤水分的干旱胁迫指标,以便分析干旱胁迫程度,进而理解死苗的原因[10];但是,目前栓皮栎的干旱胁迫指标很不完善,仅粗略地分轻、中、重3个干旱胁迫等级[10]。有学者[11-12]的研究曾经指出,轻度干旱不影响光合作用,不产生干旱胁迫;重度干旱时光合速率才迅速下降,才有明显的干旱胁迫。另外,土壤质地效应影响干旱胁迫指标值,即不同土壤质地的土壤,即使土壤水分含量相同,栓皮栎幼苗受到的干旱胁迫程度也会不同。所以,需要研究不同土壤质地、不同土壤水分含量的干旱胁迫指标。太行山石质山地土壤对栓皮栎幼苗的质地效应如何?质地效应对土壤干旱的指标影响有多大?

叶绿素荧光是植物干旱的敏感指针[13-14],对太行山小浪底地区不同质地土壤干旱胁迫下栓皮栎叶绿素荧光参数进行测定和分析,研究土壤水分的质地效应,并确定干旱胁迫指标,可为栓皮栎实生苗幼苗生态分析和人工调控生态环境、提高幼苗存活率和促进种群增长提供依据。

1 材料与方法 1.1 试验材料

在太行山南麓黄河小浪底选5个样点(样点位置分别在:沙石坡、全树岭、瞭望塔、气象站、蒸渗仪),平原林地选1个样点(样点位置在郑州市)作为对照。将6个样点的土壤样本,用Mastersize 2000土壤粒径分析仪,分别测定土壤颗粒 < 2、2~50和50~2000μm 3个不同等级的土壤颗粒数目。以粉粒占比递增、砂粒占比递减、黏粒占比基本递增的原则,排序并编号A~F。根据美国农部制土壤质地三角图,6个土壤样本分为3种土壤质地类型。样点分布及其自然地貌、土壤性状、土壤质地和土壤粒径分布如表 1

表 1 试验样点地貌及土壤特征 Tab. 1 Landfroms and soil characteristics of experimental sample points
1.2 试验方法

用盆栽1年生栓皮栎实生苗,浇水至土壤含水量达到饱和状态,移入遮雨棚自然降低土壤湿度。从浇水后第2天开始,用德国WALZ公司的Mini-PAM叶绿素荧光仪测定叶绿素荧光最大量子效率(Fv/Fm)和实际量子产量Y(Ⅱ)。测定后用天平称花盆质量。每天重复以上测定,直至叶片枯死。完成以上测定过程后,取出花盆中土壤和幼苗,将幼苗、栓皮栎种子和土壤分开称质量,烘干土壤称得干土质量。计算出各花盆测定时的土壤湿度。

1.3 数据处理 1.3.1 叶绿素荧光参数模拟

栓皮栎幼苗叶绿素荧光参数中,Fv/FmY(Ⅱ)在土壤水分胁迫下随土壤湿度降低而降低,可用幂函数模拟。

Fv/FmY(Ⅱ)随土壤湿度的变化均为幂函数关系,可以统一用下式表示

$ y = {y_\rm {m}} - \alpha {\theta ^{ - b}} $ (1)

式中:yFv/FmY(Ⅱ),量纲为1;ymFv/FmY(Ⅱ)的最大值,量纲为1;θ为土壤湿度,%。

1.3.2 胁迫开始下降点模拟方法

Fv/FmY(Ⅱ)随土壤湿度减少而下降,下降由慢到快的转折点,对应幂函数曲线斜率为1的点,是曲线的一阶导数等于1的1个特征点。这个点即是开始下降点的土壤湿度θk,对应的叶绿素荧光参数用Fv/FmkY(Ⅱ)k表示。

1.3.3叶绿素荧光参数下降50%计算方法

参考Ulrich Schreiber[15]的分析方法,土壤水分胁迫导致抑制50%电子传递的“临界值”,用θ50表示。

根据前述得到的Fv/FmY(Ⅱ)随土壤湿度的变化的模拟方程,令

$ y = 0.5{y_m} $ (2)

则可反求得θ50

2 结果与分析 2.1 Fv/FmY(Ⅱ)与土壤湿度的关系

Fv/FmY(Ⅱ)与土壤湿度的关系,用散点表示,并用式(1)的方法模拟,给出模拟曲线。如图 1(以样点A和F为代表其余略去)。幂函数能较好地模拟Fv/FmY(Ⅱ)随土壤湿度降低的变化规律,Fv/Fm模拟值与散点间关系系数在0.7~0.9之间,Y(Ⅱ)模拟值与散点间关系系数在0.6~0.8之间。

图 1 Fv/FmY(Ⅱ)随土壤湿度的变化 Fig. 1 Fv/Fm and Y (Ⅱ) changing with soil humidity
2.2 Fv/FmY(Ⅱ)的θkθ50及不同样点间差异性检验

Fv/Fm开始下降时的土壤湿度θk(表 2)在7.9%~15.5%之间,不同土壤样点有较大的变化。方差分析结果本试验样点在0.05信度下可分为2类。A、B、C、D与E、F之间有较显著的差异。Y(Ⅱ)的开始下降时的土壤湿度θk在11.2%~19.3%之间,不同土壤样点也有较大的变化。A、B、C、D与E、F之间也有较显著的差异。

表 2 6个土壤样点干旱胁迫下Fv/FmY(Ⅱ)开始下降时的土壤湿度θk及其方差 Tab. 2 Soil humidity and standard deviation while Fv/Fm and Y(Ⅱ) starts decreasing under drought stress in 6 soil sample points  

Fv/FmY(Ⅱ)的θ50(表 3)与前述开始下降点类似,也是A、B、C、D与E、F之间有较显著的差异。同一样点θ50(Fv/Fm) < θ50(Y(Ⅱ)),Y(Ⅱ)比Fv/Fm更加敏感的反应植物对环境胁迫的表征[16]

表 3 6个土壤样点干旱胁迫下Fv/FmY(Ⅱ)下降50%时的土壤湿度θ50及其方差 Tab. 3 Soilhumidity and standard deviation while Fv/Fm and Y(Ⅱ) decreases 50% under drought stress in 6 soil sample points  
2.3 由θkθ50确定干旱胁迫指标

综合2.2中的结果,干旱胁迫下土壤样点A、B、C和D的叶绿素荧光参数开始下降时的土壤湿度θk(Fv/Fm)的平均值为9.6%,θk(Y(Ⅱ))的平均值为12.9%,下降50%时的土壤湿度θ50(Fv/Fm)的平均值是5.7%,θ50(Y(Ⅱ))的平均值为7.9%。以θ > θk(Y(Ⅱ))为无干旱,θk(Y(Ⅱ)) > θ > θk(Fv/Fm)为轻度干旱,θk(Fv/Fm) > θ > θ50(Y(Ⅱ))为中度干旱,θ < θ50(Y(Ⅱ))为重度干旱,确定干旱胁迫土壤湿度指标。若θ < θ50(Fv/Fm)则接近死苗。干旱胁迫下土壤样点E和F的叶绿素荧光参数开始下降时的土壤湿度θk(Fv/Fm)的值为14.9%,θk(Y(Ⅱ))为18.7%,下降50%时的土壤湿度θ50(Fv/Fm)为9.8%,θ50(Y(Ⅱ))为12.8%。类似于土壤样点A、B、C、D,可确定土壤样点E、F的各干旱级别土壤湿度指标。综合如表 4所示。

表 4 栓皮栎幼苗6个土壤样点的干旱胁迫指标 Tab. 4 Drought stress index of Quercus variabilis seedlings in 6 soil sample points  
3 讨论

目前,对栓皮栎幼苗的干旱胁迫程度研究区分不细致,以轻、中、重3个等级来划分[9]。不能适应精准林业需要。植物叶绿素荧光参数对环境胁迫敏感,这为植物干旱指标界限值的确定提供了很好的手段[13]。监测跟踪这些叶绿素荧光特性的变化,就可以及时掌握环境胁迫的发生,预知对植物的影响的程度,及时采取防御措施。小浪底地区植被的生态恢复过程中,栓皮栎幼苗的存活问题是关键[8, 16-20],而干旱胁迫是影响存活的主要因素[8-9, 16-17]。准确的栓皮栎幼苗的干旱胁迫指标是科学研究和生产所需。笔者分析了6个样点3种土壤质地类型下栓皮栎幼苗的叶绿素荧光参数随土壤湿度的变化,得到了干旱胁迫的土壤水分指标。砂壤土和粉壤土的干旱胁迫指标差异不大,它们与粉土差异是比较明显的,相差4%~6%左右。这说明了研究不同质地类型是有意义的。

分析栓皮栎幼苗干旱胁迫下6个样点叶绿素荧光参数的开始下降和下降50%时所对应的土壤湿度可知,6个土壤样点干旱胁迫指标可分为2类,砂壤土和粉壤土的样点A、B、C、D为1类;粉土的E、F为1类。Fv/FmY(Ⅱ)同一叶绿素荧光参数样点间相比,样点A、B、C、D中平原砂壤土C所对应的土壤湿度最低,顺序为C < A < B < D,这与土壤含砂比例越大,土壤水分可利用率越高不同。这可能与山区土壤和平原土壤物理性质不同有关,平原壤土C兼具砂壤土和粉壤土的性质,植物对其水分利用率最高。样点E和F中,粉粒占比E < F,叶绿素荧光参数开始下降和下降50%所对应的土壤湿度E>F,样点的E最易对栓皮栎幼苗产生干旱胁迫,这与土壤粉粒比例越大,土壤水分可利用率越低不同。这可能与土壤的类型、结构、质地都有很大关系,有待进一步研究。

4 结论

1) 土壤质地对栓皮栎幼苗的作用呈“反质地效应”,即质地越细,土壤水分的有效性越差,土壤干旱的水分指标越偏高;砂粒含量较高质地的土壤水分有效性好,土壤干旱的水分指标偏低。来自于平原地区(郑州市,编号C)的土壤与山地砂性土的A、B、D差异不明显。

2) 基于叶绿素荧光参数Fv/FmY(Ⅱ),确定了2种干旱胁迫指标。砂壤土A、B和粉壤土C、D的干旱胁迫指标为:> 13%无干旱,> 10%~13%轻度干旱,> 8%~10%中度干旱,> 5%~8%重度干旱。粉土E和F的干旱胁迫指标为:> 19%无干旱,> 15%~19%轻度干旱,> 13%~15%中度干旱,> 9%~13%重度干旱。

3) 质地效应主要是土壤黏粒和粉粒含量高,土壤水分有效性下降,Fv/FmY(Ⅱ)随土壤水分降低而下降得较快。Fv/FmY(Ⅱ)随土壤水分降低而下降50%的土壤水分指标与土壤质地的黏粒和粉粒关系虽未通过显著性检验,但相关系数为0.41~0.54,且也与砂粒负相关,也表现出了质地效应的内涵主要是黏粒和粉粒含量的作用。

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