放牧对晋北农牧交错带赖草草地生态系统碳交换的影响

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邢鹏飞, 李刚, 陈晓鹏, 李德颖, 王常慧, 董宽虎, 赵祥. 放牧对晋北农牧交错带赖草草地生态系统碳交换的影响. 草业学报, 2019,28(10): 1-11
XING Peng-fei, LI Gang, CHEN Xiao-peng, LI De-ying, WANG Chang-hui, DONG Kuan-hu, ZHAO Xiang. Effects of grazing on carbon exchange in a Leymus secalinus grassland ecosystem in the agro-pastoral ecotone of Northern Shanxi . Acta Prataculturae Sinica,2019,28(10): 1-11 复制到剪切板

Doi:10.11686/cyxb2018724
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放牧对晋北农牧交错带赖草草地生态系统碳交换的影响

邢鹏飞¹, 李刚¹, 陈晓鹏¹, 李德颖², 王常慧³, 董宽虎¹, 赵祥^1,^*

1.山西农业大学动物科技学院, 山西太谷030801

2.北达科他州立大学植物科学系, 美国北达科他法戈58108

3.中国科学院植物研究所植被与环境变化国家重点实验室,北京100093

通信作者. E-mail:sxndzhaox@126.com

作者简介:邢鹏飞(1994-),男,山西高平人,在读硕士。E-mail:sxpfxing@163.com

收稿日期: 2018-11-07

基金项目:国家自然科学基金(31572452、31870438),山西省科技创新团队建设项目(2015013001-10)和山西省工程技术研究中心项目(201605D141001)资助

摘要

生态系统净碳交换(NEE)是评估碳循环及收支的重要指标,由生态系统总初级生产力(GEP)及生态系统呼吸(ER)共同决定。以晋北农牧交错带赖草草地为研究对象,利用LI-840a静态箱法,通过观测为期2年(2015-2016)围封和放牧管理下NEE、ER和GEP的日动态和季动态,分析其与气温、土壤温度(0~10 cm)、土壤含水量(0~10 cm),以及地上和地下生物量的相关性,旨在说明放牧对农牧交错带赖草草地生态系统碳交换的影响。结果表明:放牧显著降低了赖草草地地上、地下生物量;NEE、ER和GEP的日变化及季节变化特征明显,均呈现单峰型变化,在5、6、9月较低,在7-8月较高;生态系统碳交换的日变化主要受气温影响,而季节变化主要受表层土壤温度影响;同时NEE、ER和GEP与地上、地下生物量也存在极显著相关性;相比围封,放牧明显降低了该草地生物量和生态系统碳交换速率,但未改变日、季变化趋势。说明放牧通过破坏草地植被光合组织,降低了草地生态系统碳交换能力,减弱了草地生态系统碳汇功能。

关键词: 放牧; 赖草草地; 生态系统净碳交换; 生态系统呼吸; 生态系统初级生产力

Effects of grazing on carbon exchange in a Leymus secalinus grassland ecosystem in the agro-pastoral ecotone of Northern Shanxi

XING Peng-fei¹, LI Gang¹, CHEN Xiao-peng¹, LI De-ying², WANG Chang-hui³, DONG Kuan-hu¹, ZHAO Xiang^1,^*

1.College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu 030801, China

2.Department of Plant Science, North Dakota State University, Fargo 58108, United States

3.State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China

Corresponding author. E-mail:sxndzhaox@126.com

Abstract

Ecosystem net carbon exchange (NEE) is an important index to evaluate the carbon cycle, and is calculated from total primary productivity (GEP) and ecosystem respiration (ER). The aim of this study was to explore the effects of grazing on carbon exchange in the Leymus secalinus grassland ecosystem in the agro-pastoral ecotone of Northern Shanxi. Using the static chamber technique (LI-840a), we measured the daily and seasonal dynamics of NEE, ER, and GEP in the L. secalinus grassland under grazing during 2015 and 2016, and analyzed the correlation between these indexes and atmospheric temperature, soil temperature, soil moisture content, and aboveground and belowground biomass. The NEE, ER, and GEP showed clear daily and seasonal variations, which were the unimodal type. The values of NEE were lower in May, June, and September, but higher in July and August. The daily dynamics of NEE were mainly controlled by air temperature, while the seasonal changes were mainly controlled by soil temperature. Correlations between aboveground biomass as well as belowground biomass and NEE, ER, and GEP were extremely significant. Compared with fencing, grazing significantly decreased the NEE rate of the ecosystem in this grassland, but it did not affect the daily and seasonal trends in NEE. These results showed that, compared with enclosure, grazing can decrease the carbon exchange capacity and weaken the carbon sink function of a grassland ecosystem by reducing the proportion of photosynthetic matter in grassland vegetation.

Keyword: grazing; Leymus secalinus grassland; net ecosystem carbon exchange; ecosystem respiration; gross ecosystem primary productivity

文章图片

生态系统净碳交换(net ecosystem carbon exchange, NEE), 是由光合作用碳吸收量与呼吸作用碳释放量之间的不平衡所决定的^[1], 是生态系统总初级生产力(gross ecosystem primary productivity, GEP)与生态系统呼吸(ecosystem respiration, ER)两个过程的平衡^[2], 它体现生态系统的碳汇或碳源能力^[3]。由于植物光合作用与生态系统呼吸作用受到植被、土壤和环境因子等多种因素的调控, 而生态系统的气候、养分条件又处于不断变化的状态, 所以不同生态系统的碳源/汇状态也处于不断变化中^[4]。同时, 人类活动也会影响生态系统净碳交换^[5]。研究表明, 草地的固碳能力对不同草地类型、不同放牧利用方式的响应不同^[6]。

草地作为陆地生态系统重要组成部分之一^[7], 在陆地碳循环中占有重要地位。放牧作为草地的主要利用方式, 家畜的采食行为和践踏作用影响着草地环境, 改变草地植被结构和功能特征。首先, 家畜采食植被, 减少了地上净初级生产力。Semmartin等^[8]的研究表明草地地上净初级生产力与放牧强度之间存在负线性关系, 放牧强度的变化控制了地上净初级生产力的变化。家畜采食植物茎叶, 减少了群落地上生物量, 破坏了植物的光合组织, 因此影响了草地生态系统对碳的吸收。其次, 放牧对植物地下生物量结构的影响很难预测, 已有的研究结果对此意见不一。有研究表明放牧降低了草地地下生物量^[9], 而Rueda等^[10]在地中海一带的研究表明, 在一些低地中放牧增加了草地表层土的根生物量。此外, 放牧转移植物生物量, 食草动物改变了草地冠层结构及能量平衡, 引起土壤温度和土壤水分平衡的反馈, 因而影响土壤微生物活性, 最终影响净碳吸收^[11]。土壤温度的降低也会减慢植被根系的生长、对矿质元素等养分的吸收及向地上部的转运速率、微生物的活动, 从而减小ER^[11]。

赖草(Leymus secalinus)为禾本科赖草属植物, 其根茎繁衍迅速, 耐寒并耐旱, 且具有较强的耐盐性^[12]。赖草草地作为山西北部农牧交错带低地盐渍化草地的一种重要草地资源, 近年来由于不合理的放牧致使草地群落结构简单化, 生产功能弱化, 从而影响了草地的碳输入, 因此要准确评估我国北方农牧交错带上该草地生态系统碳收支, 有必要对其生态系统碳交换进行研究。本研究对围封和放牧管理8年的赖草草地碳交换速率的日、季动态进行连续观测2年, 分析其与土壤温度、含水量及生物量的关系, 旨在揭示这两种管理方式下赖草草地净碳交换速率的变化特征。

1 材料与方法

1.1 试验区概况

本实验在山西省朔州市右玉县(E 112° 19.660', N 39° 59.808')山西农业大学右玉草地生态系统野外观测研究站进行。海拔1348 m, 年均气温4.7 ℃, 最冷月(1月)均温-14 ℃(-17.8~-9.9 ℃), 最热月(7月)均温20.5 ℃(18.9~22.4 ℃), ≥ 0 ℃年积温2600~3600 ℃。终霜期在5月初, 初霜期在9月中、上旬, 无霜期100~120 d。全年太阳总辐射量为598 kJ· cm^-2, 年日照2600~2700 h; 年均降水量435 mm, 属温带大陆性季风气候。样地土壤类型为苏打草甸碱土, pH 9.2。地区植被类型属温性草原类, 试验地草地属低地草甸类盐化低地草甸亚类, 草地型为赖草-鹅绒委陵菜(Potentilla anserina)-杂类草群丛, 主要生长有赖草、鹅绒委陵菜、蒲公英(Taraxacum mongolicum)、艾蒿(Artemisia argyi)、碱地风毛菊(Saussurea runcinata)、碱茅(Puccinellia distans)、碱蓬(Suaeda glauca)、车前(Plantago asiatica)、西伯利亚蓼(Polygonum sibiricum)、芦苇(Phragmites communis)等。

1.2 试验设计

试验地于2008年开始围栏封育, 放牧地为全年自由放牧, 放牧强度为每公顷2.00个羊单位, 放牧和围栏样地面积150 m× 150 m。在样地对角线上等距离设10个1 m× 1 m样方。

1.3 测定内容及方法

2015和2016年5-9月每月的4和24日测定生态系统净碳交换速率(NEE)、生态系统呼吸(ER)、大气温度、0~10 cm土壤温度、0~10 cm土壤含水量、植被地上生物量、0~100 cm地下生物量, 其中植被地上、地下生物量于每月中旬进行测量。

1.3.1 NEE和ER的测定采用静态箱法, 测定前1周在放牧和围封样地各安装10个底座(即测定重复)。采用样线法每隔10~15 m安装一个底座。底座高8 cm, 插入地下5 cm, 地上部露出3 cm。箱体由透明有机玻璃构成, 长宽高均为50 cm, 箱体内配有2个风扇, 使箱内气体充分混匀, 测量时通过导气管与LI-840a CO₂/H₂O红外分析仪连接, 将同化箱盖在底座上测定箱内CO₂和H₂O浓度的变化, 测量时间120 s, 记录开始和结束时箱体内的温度。完成NEE测定后通风、复扣同化箱, 盖上遮阳罩测定ER, 最后计算GEP。在测定生态系统碳交换速率的同时测定0~10 cm土壤温度、0~10 cm土壤湿度、大气温度等, 大气和土壤温度用空气温度计和土壤温度计直接测得, 土壤湿度采用TDR 300土壤水分速测仪(Specctrum, USA)测得。每月上旬和下旬各测定一次, 每次监测时间为24 h, 当日7:00开始, 次日7:00结束, 每3 h测定一次。

采用线性拟合的方法计算CO₂浓度变化速率(dc/dt), 即斜率。CO₂交换速率的计算采用以下公式:

Fc= $\frac{V \times P_{av} (1000 - W_{av})}{R \times S (T_{av} + 273)}$ × $\frac{dc}{dt}$

其中, Fc为CO₂通量(μ mol· m^-2· s^-1); V为箱体的体积, 即V=同化箱长× 宽× (箱体高度+底座露出地上部的高度); P_av为测量期间箱体内的平均大气压强(kPa); W_av是测量期间箱体内的水气分压(mmol· mol^-1); R是大气常数8.314 J· mol^-1· K^-1; S是同化箱的面积; T_av是测量期间箱体内的平均温度(℃)。

GEP=ER-NEE

当NEE为负值时, 表示吸收, 即为碳汇; NEE为正值时, 表示释放, 即为碳源。

日平均土壤温度是用各个时间段的土壤温度累加平均求得, 日平均土壤含水量是用各个时间段的土壤含水量累加平均求得。

1.3.2 草地地上、地下生物量的测定草地群落地上和地下生物量采用收获法测定。在生长季每月中旬于样方内齐地面剪下全部植物称鲜重。把所有刈割的样品放入信封, 于烘箱中恒温65 ℃烘干48 h至恒重后称重。采用根钻法(直径70 mm)测定地下生物量, 在地上部分刈割完的样方内按对角线法取根样各3钻, 分7层(0~5 cm、5~10 cm、10~20 cm、20~30 cm、30~50 cm、50~70 cm、70~100 cm)取样, 取得的地下生物量放入网袋带回实验室洗根, 剔除死根, 然后65 ℃烘干至恒重称重。

1.4 数据处理

采用Microsoft Excel 2010进行基础数据的输入与整理, 用Sigma Plot 12.5进行回归分析和绘图, 同时采用SPSS 19.0统计分析软件进行数据独立样本t检验和单因素方差分析, 用Pearson进行双因素相关分析。

2 结果与分析

2.1 赖草草地生长季生物量动态

生长季内围封和放牧的赖草草地群落地上、地下生物量均呈单峰型动态变化(图1), 除围封下地下生物量最大值出现在9月, 其余最大值均出现在8月。植物在4月底5月初期进入返青期, 但气温仍然较低, 植物生长缓慢。之后温度升高, 降水增加, 植物生长加快, 8月生物量达到最大值, 之后生物量呈下降趋势。围封草地每月地上生物量均显著高于放牧草地(P< 0.05), 放牧作用下, 草地地上生物量最高月份比围封草地减少了62.32%, 分别为389.33和146.69 g· m^-2。围封样地地下生物量除5月外均显著大于放牧样地(P< 0.05), 放牧下的地下生物量最高月份比围封草地减少了43.29%, 分别为4052.97和2298.45 g· m^-2, 放牧作用下, 赖草草地年均地上和地下生物量分别减少了64.55%和44.54%。

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图1 封围和放牧下赖草草地生物量的动态
图中不同小写字母表示生长季内不同月份间差异显著(P< 0.05), 不同大写字母表示放牧与围封样地间差异显著(P< 0.05)。Fig.1 Growth dynamics of biomass in L. secalinus communities under fencing and grazing
The different small letters mean different months have significant differences; the different capital letters mean the difference between grazing and fencing are significant (P< 0.05).

2.2 赖草草地土壤、大气温度及土壤含水量季节动态

2015及2016年围封和放牧样地大气和土壤温度变化趋势一致, 均在7月达到最大值(图2), 而0~10 cm土壤含水量在8月达到最大值。通过比较发现, 与围封相比, 放牧后的土壤温度有上升的趋势, 土壤含水量有下降趋势。两者最高的月份, 放牧比围封土壤温度提高了1.83 ℃, 土壤含水量下降了3.74%, 可能是由于家畜采食导致植被盖度降低, 太阳直射土壤表面导致土壤水分蒸发量加大。整个生长季放牧草地上平均土壤温度提高了1.23 ℃, 平均土壤含水量降低了2.39%。

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	图2 不同样地大气温度、土壤温度、土壤含水量的季节动态Fig.2 Seasonal dynamics of air temperature, soil temperature, soil water content in different plots

2.3 赖草草地生长季NEE、ER、GEP的日动态

2.3.1 赖草草地生长季NEE的日动态赖草草地NEE具有明显的日变化特征, 表现出白天为负值, 夜晚为正值(图3A)。日出后, NEE由正值转换为负值, 随温度的升高, NEE逐渐增大, 在13:00左右CO₂吸收达到最大值, 之后CO₂吸收速率逐渐降低, 到傍晚19:00, NEE由负值转化为正值, 昼夜交替的日变化非常明显。生长季放牧草地CO₂吸收的最强值出现在10:00-13:00, 为5.22 μ mol CO₂· m^-2· s^-1, 围封草地CO₂的吸收最强值也出现在10:00-13:00, 为6.95 μ mol CO₂· m^-2· s^-1, 放牧及围封样地夜间CO₂释放的最强值均出现在19:00-22:00, 分别为4.04 和4.58 μ mol CO₂· m^-2· s^-1。NEE日均值均为负值(图3B), 表现为碳吸收, 且放牧地大于围封地, 分别为-0.75和-1.27 μ mol CO₂· m^-2· s^-1, 但未达到显著水平(P> 0.05)。

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	图3 放牧和围封草地生态系统净碳交换的日动态(A)和日均值(B)Fig.3 Daily dynamics(A) and daily average value(B) of NEE of grazing grassland and fencing grassland

2.3.2 赖草草地生长季ER的日动态赖草草地ER的日动态呈单峰型变化趋势(图4A), 白天随气温的升高ER上升, 夜间随气温下降ER逐渐降低, 不同时期由于温度的不同生态系统呼吸速率(ER)的日变化有不同的特点。放牧和围封样地ER的最大值均出现在13:00-16:00, 分别为6.74和7.56 μ mol CO₂· m^-2· s^-1。放牧草地和围封草地的最小值出现在凌晨1:00-4:00, 分别为3.10和4.46 μ mol CO₂· m^-2· s^-1。图4B显示ER的日均值表现为围封地高于放牧地, 分别为5.84和4.67 mmol CO₂· m^-2· s^-1, 高出了25.05%, 未达到显著水平(P> 0.05)。

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	图4 放牧和围封草地生态系统呼吸的日动态(A)和日均值(B)Fig.4 Daily dynamics (A) and daily average value (B) of ER of grazing grassland and fencing grassland

2.3.3 赖草草地生长季GEP的日动态 GEP的日变化趋势也呈单峰型变化(图5A)。上午随温度升高, 光合作用逐渐加强。放牧草地和围封草地GEP最高值都在午后13:00-16:00出现, 分别为11.72 和14.23 μ mol CO₂· m^-2· s^-1。夜晚植物无法进行光合作用, 不吸收碳, NEE与ER相同, 由于GEP=ER-NEE, 故GEP为0。图5B中显示日均值围封地高于放牧地, 分别为5.42和7.10 μ mol CO₂· m^-2· s^-1, 但差异不显著(P> 0.05)。

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	图5 放牧和围封草地生态系统总生产力的日动态(A)和日均值(B)Fig.5 Daily dynamics(A) and daily average value(B) of GEP of grazing grassland and fencing grassland

2.4 赖草草地生长季NEE、ER、GEP的季节动态

放牧地和围封地NEE、ER、GEP的季节动态趋势一致, 均在8月达到峰值。如图6A所示, 放牧草地和围封草地的NEE季节变化规律一致, 表现为先降低再升高的趋势, 从5月开始, 随着水热条件逐渐转好, 植物生长加快, 光合作用加强, 8月NEE达到最大, 此时放牧和围封草地的NEE值分别为-1.13和-1.70 μ mol CO₂· m^-2· s^-1。赖草草地在两种处理下的NEE均为负值, 表现为碳汇, 可能是测定生长季植物生长良好, 同时施加的放牧处理强度适中, 使得植物群落在生长季都处于碳汇状态。且NEE均值为放牧草地大于围封草地, 在放牧作用下净碳吸收速率下降了40.94%, 但差异不显著(P> 0.05)。

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图6 放牧和围封草地生态系统NEE、ER、GEP的季节动态
图A、B为NEE的季节动态和均值图, C、D为ER的季节动态和均值图, E、F为GEP的季节动态和均值图。Fig.6 Seasonal dynamics of NEE、ER、GEP of grazing grassland and fencing grassland
A and B show the seasonal dynamics and average value of NEE, respectively; C and D show the seasonal dynamics and average value of ER, respectively; E and F show the seasonal dynamics and average value of GEP, respectively.

从图6C可以看出, 在植物生长季ER具有明显的季节特征, 围栏内外表现出很好的一致性, 即单峰曲线。从5月开始, 赖草草地ER迅速上升, 到8月出现峰值, 此时围封草地的生态系统呼吸速率显著高于放牧草地(P< 0.05), 分别为8.82和7.11 μ mol CO₂· m^-2· s^-1, 9月随着气温降低, 降水减少, 土壤酶活性降低, ER迅速下降。整个生长季ER均值放牧草地低于围封草地(图6D), 放牧作用使ER降低了21.35%, 差异不显著(P> 0.05)。

图6E显示, GEP的季节动态特征也很明显, 且变化趋势与ER一致, 各月GEP值均是放牧草地低于围封草地, 尤其7、8月, 生长旺季差异显著(P< 0.05), 但两种处理下的草地GEP均值差异不显著(P> 0.05), 放牧使得生态系统总生产力降低了23.66%。

2.5 赖草草地NEE、ER和GEP的日变化与温度、土壤含水量的关系

围栏内外NEE、ER、GEP的日动态与气温及土壤温度的相关性分析表明(表1), 放牧草地和围封草地的NEE、ER、GEP与大气温度均存在极显著相关性(P< 0.01)。而与0~10 cm土壤温度间的相关性较为复杂, 整个生长季NEE与土壤温度均无显著相关性(P> 0.05), 除7月围栏内外及8月围封草地的ER与土壤温度有极显著相关性外(P< 0.01), 其他月份均无显著相关性(P> 0.05); 7月围封地GEP与土壤温度有显著相关性(P< 0.05), 8月放牧地的GEP 与土壤温度之间相关性达到极显著水平(P< 0.01), 其余月份两种处理方式下的草地GEP与土壤温度之间均无显著相关性(P> 0.05)。同时由于土壤含水量在一天之内变化很小, 所以NEE、ER、GEP的日变化在生长季的每个月份, 在放牧草地与围封草地上与土壤含水量之间均无显著相关性(P> 0.05), 表明在日尺度上气温是对生态系统碳交换过程主要的影响因子。

表1 赖草草地NEE、ER、GEP与大气温度和0~10 cm土壤温度及土壤含水量相关性 Table 1 The correlation coefficients between NEE, ER, GEP and atmospheric temperature, 0-10 cm soil temperature and soil water content in L. secalinus grassland

2.6 赖草草地NEE、ER和GEP的季节变化与温度、土壤含水量及植物生物量的关系

回归分析表明(表2), NEE的季节变化与土壤温度和大气温度间不存在显著相关性(P> 0.05), 与土壤含水量仅在放牧地存在显著线性负相关(P< 0.05), 因为NEE均为负值, 而在围封地则无显著相关性(P> 0.05)。ER与温度、土壤含水量的相关性均为指数关系(P< 0.05), 即随着温度和土壤水分含量的升高ER逐渐增大。GEP与3个环境因子之间均存在显著相关关系(P< 0.05), 且以线性负相关为主。而NEE、ER、GEP与生物量之间以线性正相关为主(P< 0.05), NEE与地上和地下生物量之间有二次项关系, 可能是由于优势植物生长茂盛, 阻断了太阳光向地面及下层植物的照射, 同时随着根系增多土壤呼吸增多, 导致CO₂净吸收先上升后下降。由表2可以看出, 各自变量与土壤温度的拟合效果要优于土壤含水量, 表明在季节尺度上土壤温度成为影响生态系统碳交换的主要因子。

表2 赖草草地NEE、ER和GEP的季节变化与温度、土壤含水量及植物生物量的关系 Table 2 Relationship between seasonal change of NEE, ER, GEP and temperature, soil moisture, plant biomass in L. secalinus grassland

3 讨论

3.1 生态系统碳交换与环境因子的关系

温度和水分是影响生态系统碳交换的重要环境因子^{[13, 14, 15, 16]}。温度通过影响光合作用酶活性、空气湿度控制气孔导度而影响植物光合作用^{[17, 18]}, 而土壤水分则与土壤微生物活性、植物生理活性有关。武倩等^[19]的增温实验表明, 增温使得植物冠层温度增加, 光合作用增强, 同时也增强了土壤微生物活性, 增强了土壤呼吸进而使得ER增加; 胡毅等^[20]的研究则表明土壤含水量与NEE和GEP呈线性负相关关系, 与ER呈现指数相关关系。本试验中赖草草地NEE、ER和GEP均具有明显的日变化特征, 白天随日出温度升高, NEE、ER和GEP逐渐增大, 由碳释放转为碳吸收, 中午13:00左右达到一天中的最大值, 之后随温度降低开始下降, 由碳吸收转为碳释放。但由于土壤温度在一天中变化较小, 故对NEE、ER和GEP日变化的影响不显著。此外, 其季节变化趋势也较为明显, 呈现“ 钟型” 趋势, 先增大后降低, 最大值均出现在8月。并通过分析NEE、ER和GEP季节变化与温度、土壤含水量的相关性, 发现NEE与环境因子之间相关性不显著, 可能是由于试验过程中7月的气温及土壤温度最高, 而土壤含水量较低, 过高的温度以及一定程度上的水分亏缺使得空气饱和水汽压差增大, 从而导致蒸腾增加, 植被叶片气孔关闭^[21], 从而降低生态系统净碳吸收, 而此时较高的温度也可能会提升相关酶活性, 促进土壤呼吸作用^[13], 也会影响净碳交换及其对环境因子的响应。ER和GEP与环境因子之间存在极显著相关性, 说明环境因子不直接影响生态系统净碳交换, 而是通过影响生态系统呼吸和光合来间接影响净碳交换, 这与伏玉玲等^[22]研究羊草(Leymus chinensis)草原的结果基本一致。ER和GEP与温度的相关性大于与水分的相关性, 说明生态系统碳交换对温度的敏感性大于水分, 这与靳宇曦等^[23]关于短花针茅(Stipa breviflora)荒漠草原的研究结果基本一致, 即土壤温度对生态系统净碳交换的贡献大于土壤湿度。

3.2 放牧对生态系统碳交换的影响

放牧家畜主要通过采食和践踏直接影响植物群落组成、地上生物量(或地上净初级生产力)、凋落物而影响NEE^[24], 此外, 还会引起土壤温度和土壤水分平衡的反馈, 最终影响净碳吸收^[25]。本研究中围封和放牧下NEE、ER和GEP在日尺度和季节尺度上的变化趋势没有差异, 但是与放牧相比, 围封显著增加了碳交换速率。在季节尺度上, 放牧和围封样地NEE值分别为-0.75和-1.27 μ mol CO₂· m^-2· s^-1, 表明在季节尺度上围封样地的碳吸收速率大于放牧样地, 原因是围封后植被得以恢复^[26]。地上绿色植被是植物固定光能的唯一途径, 而放牧家畜通过采食, 降低了植被地上生物量, 破坏了植株的光合器官, 使群落光合作用下降, 因此降低了生长季群落的碳汇功能。同时, 放牧地ER小于围封地。因为地上生物量减少, 导致每年的凋落物及立枯物较少, 从而使得土壤C、N含量减少^[27], 且地上植被是根系获得能量的途径, 地上植被的减少必然影响到植被地下根系, 进而影响根系呼吸, 而根呼吸是土壤呼吸的重要组成部分^[28]。因此, 围封通过增加群落地上、地下生物量进而增强了群落总呼吸^[29]。由于GEP等于碳净交换量与生态系统呼吸释放碳量之和, 故放牧同时也降低了群落GEP。2015年赖草群落围封样地和放牧样地GEP总值分别为3826.49和3002.81 g CO₂· m^-2, ER释放CO₂分别为3082.2和2675.2 g CO₂· m^-2, 净固碳量分别为744.3和327.6 g CO₂· m^-2, 2016年围封样地和放牧样地GEP总值分别为4699.15和3501.78 g CO₂· m^-2, 生态系统呼吸总释放量分别为3923.64和2925.85 g CO₂· m^-2, 净固碳量分别为775.51和575.93 g CO₂· m^-2。说明围封对于提高草地生产力, 增强生长季群落的碳吸收能力是有效果的。同时, 土壤含水量也是限制群落生产力和土壤生物活性的主导因素^[30], 含水量过低或过高都会影响土壤微生物活性^{[13, 27]}及土壤的物理性质和植被的生长^[25], 但是本研究结果表明, NEE只在放牧条件下与土壤含水量的相关性达显著水平(P< 0.05), 围封地中生物量大于放牧地, 对土壤的保水作用较大, 在放牧地的水分胁迫程度高于围封地, 土壤水分利用效率也较高。因此, 提高草地植被可利用的土壤含水量也可以促进草甸草原生态系统碳交换。

4 结论

温度和土壤含水量是影响赖草草地生态系统碳交换的两个重要因子, 生态系统碳交换与温度和土壤含水量存在显著的相关关系, 土壤温度的作用大于土壤含水量。赖草草地生态系统碳交换规律都表现为明显的日变化和季节变化, 均呈单峰曲线; 放牧并没有改变生态系统碳交换的变化规律, 而降低了草地生态系统净碳交换能力, 减弱了草地生态系统碳汇功能, 但围栏封育通过保护植被, 其碳吸收显著高于围栏外放牧草地。

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[25]	Li X R, Ma F Y, Xiao H L, et al. Long term effects of revegetation on soil water content of sand dunes in arid region of Northern China. Journal of Arid Environments, 2004, 57: 1-16. [本文引用:2]
[26]	Yang Y, Han G D, Li Y H, et al. Response of soil respiration to grazing intensity, water contents, and temperature of soil in different grassland s of Inner Mongolia. Acta Prataculturae Sinica, 2012, 21(6): 8-14. 杨阳, 韩国栋, 李元恒, 等. 内蒙古不同草原类型土壤呼吸对放牧强度及水热因子的响应. 草业学报, 2012, 21(6): 8-14. [本文引用:1]
[27]	Barger N N, Ojima D S, Belnap J, et al. Changes in plant functional groups, litter quality, and soil carbon and nitrogen mineralization with sheep grazing in an Inner Mongolia grassland . Rangel Ecol Management, 2004, 57: 613-619. [本文引用:2]
[28]	Zhang Y, Hong M. Response of soil respiration to experimental warming and nitrogen addition in inner mongolia desert steppe. Acta Agrestia Sinica, 2014, 22(6): 1227-1231. 张宇, 红梅. 内蒙古荒漠草原土壤呼吸对模拟增温和氮素添加的响应. 草地学报, 2014, 22(6): 1227-1231. [本文引用:1]
[29]	Zhang W L, Chen S P, Miao H X, et al. Effects on carbon flux of conversation of grassland steppe to cropland in China. Journal of Plant Ecology, 2008, 32(6): 1301-1311. 张文丽, 陈世苹, 苗海霞, 等. 开垦对克氏针茅草地生态系统碳通量的影响. 植物生态学报, 2008, 32(6): 1301-1311. [本文引用:1]
[30]	Zhu H S, Li G, Dong K H, et al. *Effect of grazing on diurnal and seasonal dynamics of soil respiration rate of Leymus secalinus* communities*. Chinese Bulletin of Botany, 2015, 50(5): 605-613. 朱慧森, 李刚, 董宽虎, 等. 放牧对赖草草地土壤呼吸日、季动态的影响*. 植物学报, 2015, 50(5): 605-613. [本文引用:1]

2004

0.0

... 生态系统净碳交换(net ecosystem carbon exchange, NEE),是由光合作用碳吸收量与呼吸作用碳释放量之间的不平衡所决定的^[1],是生态系统总初级生产力(gross ecosystem primary productivity, GEP)与生态系统呼吸(ecosystem respiration, ER)两个过程的平衡^[2],它体现生态系统的碳汇或碳源能力^[3] ...

2017

0.0

2001

0.0

. 2001, 25(4):414-419

Implications and estimations of four terrestrial productivity parameters

生物生产力的#cod#x0201c;4P#cod#x0201d;概念、估算及其相互关系

Fang J Y , Ke J H , Tang Z Y

方精云, 柯金虎, 唐志尧

2014

0.0

... 由于植物光合作用与生态系统呼吸作用受到植被、土壤和环境因子等多种因素的调控,而生态系统的气候、养分条件又处于不断变化的状态,所以不同生态系统的碳源/汇状态也处于不断变化中^[4] ...

2015

0.0

... 同时,人类活动也会影响生态系统净碳交换^[5] ...

2015

0.0

. 2015, 32:1748-1756 DOI:10.11829/j.issn.1001-0629.2015-0096

Effects of livestock exclosure and grazing on carbon sequestration in grassland ecosystem

围栏禁牧与放牧对草地生态系统固碳能力的影响

Zou J R , Zhao X Q

邹婧汝, 赵新全

1.Northwest Plateau Institute of Biology, Chinese Academy of Sciences, Xining 810001, China; 2.University of Chinese Academy of Sciences, Beijing 100049, China

Carbon sequestration in the grassland ecosystems has important effects on the global carbon stocks. Grazing as one of the most widely land usage methods affects carbon sequestration in the grassland.However, unreasonable and over-grazing can lead to grassland degradation which has negative effects on carbon stocks in the grassland. Livestock enclosure and grazing affect carbon sequestration in the grassland by altering the vegetation productions and soil carbon stocks. This review indicated that livestock exclosure and grazing had positive or negative effects on the vegetation production which were affected by some other factors and their interaction, such as aboveground litter, vegetation structure, climate conditions, and so on. The effects of grazing on vegetation production were also related to the grazing intensity. Livestock exclosure and grazing had positive or negative effects on soil carbon stocks by affecting many processes in the soil carbon cycling. In summary, the effects of livestock exclosure and grazing on carbon sequestration in grassland were complicated. In order to make the scientific decision on grassland managements,the estimations of carbon stocks and researches on the related mechanisms are necessary in the further study.

草地生态系统固碳能力对全球碳贮量的大小有重要影响。放牧作为草地最广泛的利用方式之一影响着草地的碳贮量,过度和不合理的放牧方式造成草地退化,引起草地碳的损失。围栏禁牧与放牧对草地生态系统固碳能力的影响主要包括对植被生产力和土壤碳贮量的影响,本文对有关的报道进行了综述。结果显示,由于受植被凋落物、群落结构和气候等多因素的影响,围栏禁牧对草地植被生产力有正面或负面的效应;放牧对植被生产力的影响也没有一致的结果,此外,放牧对植被生产力的影响还与放牧的强度有关。围栏禁牧与放牧可以通过多种途径对草地土壤碳贮量产生正面或负面的影响。总之,围栏禁牧与放牧对草地生态系统固碳能力的影响是复杂多样的,需要对草地碳贮量进行估算,并对相关的机制进行研究,这样才能在草地管理方面做出合理的决策。

... 研究表明,草地的固碳能力对不同草地类型、不同放牧利用方式的响应不同^[6] ...

1993

0.0

... 草地作为陆地生态系统重要组成部分之一^[7],在陆地碳循环中占有重要地位 ...

2006

0.0

... Semmartin等^[8]的研究表明草地地上净初级生产力与放牧强度之间存在负线性关系,放牧强度的变化控制了地上净初级生产力的变化 ...

2008

0.0

... 有研究表明放牧降低了草地地下生物量^[9],而Rueda等^[10]在地中海一带的研究表明,在一些低地中放牧增加了草地表层土的根生物量 ...

2010

0.0

... 有研究表明放牧降低了草地地下生物量^[9],而Rueda等^[10]在地中海一带的研究表明,在一些低地中放牧增加了草地表层土的根生物量 ...

1999

0.0

... 此外,放牧转移植物生物量,食草动物改变了草地冠层结构及能量平衡,引起土壤温度和土壤水分平衡的反馈,因而影响土壤微生物活性,最终影响净碳吸收^[11] ...

... 土壤温度的降低也会减慢植被根系的生长、对矿质元素等养分的吸收及向地上部的转运速率、微生物的活动,从而减小ER^[11] ...

2010

0.0

... 赖草(Leymus secalinus)为禾本科赖草属植物,其根茎繁衍迅速,耐寒并耐旱,且具有较强的耐盐性^[12] ...

2018

0.0

... 1 生态系统碳交换与环境因子的关系温度和水分是影响生态系统碳交换的重要环境因子^{[13,14,15,16]} ...

... 并通过分析NEE、ER和GEP季节变化与温度、土壤含水量的相关性,发现NEE与环境因子之间相关性不显著,可能是由于试验过程中7月的气温及土壤温度最高,而土壤含水量较低,过高的温度以及一定程度上的水分亏缺使得空气饱和水汽压差增大,从而导致蒸腾增加,植被叶片气孔关闭^[21],从而降低生态系统净碳吸收,而此时较高的温度也可能会提升相关酶活性,促进土壤呼吸作用^[13],也会影响净碳交换及其对环境因子的响应 ...

... 同时, 土壤含水量也是限制群落生产力和土壤生物活性的主导因素^[30],含水量过低或过高都会影响土壤微生物活性^[13,27]及土壤的物理性质和植被的生长^[25],但是本研究结果表明,NEE只在放牧条件下与土壤含水量的相关性达显著水平(P#cod#x0003C ...

1998

0.0

... 1 生态系统碳交换与环境因子的关系温度和水分是影响生态系统碳交换的重要环境因子^{[13,14,15,16]} ...

2017

0.0

... 1 生态系统碳交换与环境因子的关系温度和水分是影响生态系统碳交换的重要环境因子^{[13,14,15,16]} ...

2013

0.0

. 2013, 24(11):3057-3064

Net carbon exchange and its environmental affecting factors in a forest plantation in Badaling, Beijing of China

北京八达岭林场人工林净碳交换及其环境影响因子

Tang X , Chen W J , Li C Y

唐祥, 陈文婧, 李春义

( 1 School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China;  2 Beijing Forestry Carbon Administration (BFCA), Beijing 100013, China;  3 Zhongguancun Institute of Green Carbon, Beijing 100083, China)

By using eddy covariance technique, a year-round (November, 2011-October, 2012) continuous measurement of net ecosystem carbon dioxide exchange (NEE) was conducted in a 4year old mixed forest plantation in Badaling of Beijing. The forest plantation ecosystem was a net carbon sink in July and August, but a carbon source in the rest months. The monthly net carbon loss and uptake were the largest in April and July, respectively. The annual net ecosystem productivity was (-256±21) g C·m -2 ·a -1 , in which, the ecosystem respiration was (950±36) g C·m -2 ·a -1 , and the gross ecosystem productivity was (694±17) g C·m -2 ·a -1 . The nighttime NEE increased exponentially with the soil temperature at 10 cm depth, with the estimated temperature sensitivity of ecosystem respiration ( Q 10 ) being 2.2. During the growth season (May-September), the daytime NEE increased with photosynthetically active radiation (PAR) as described by the Michaelis-Menten rectangular hyperbola. The ecosystem quantum yield varied seasonally, ranging from 0.0219 μmol CO 2 ·μmol -1  in May to 0.0506 μmol CO 2 ·μmol -1  in July. The maximum carbon assimilation rate and the average daytime respiration followed the seasonal trends of PAR and air temperature. In July and August, vapor pressure deficit and soil moisture played a significant role in determining daytime NEE.

2011年11月—2012年10月,采用涡度相关法对北京市八达岭林场4年生针阔混交人工林的碳交换特征进行了连续观测.结果表明：观测期间,该森林生态系统在7、8月为碳汇,其余月份均为碳源,净碳释放量与吸收量分别在4月和7月达到最大.生态系统净生产力为(-256±21) g C·m -2 ·a -1 ,其中生态系统呼吸为(950±36) g C·m -2 ·a -1 ,总初级生产力为(694±17) g C·m -2 ·a -1 .生态系统呼吸与10 cm深度土壤温度呈较好的指数关系,其温度敏感性系数( Q 10 )为2.2.在5—9月,白天生态系统净碳交换对光合有效辐射的响应符合直角双曲线方程,表观量子效率呈明显的季节变化(0.0219～0.0506 μmol CO 2 ·μmol -1 ),生态系统最大光合速率和白天平均生态系统呼吸强度与光合有效辐射和温度的季节变化趋势相似.此外,7、8月饱和水汽压差与土壤含水量对白天生态系统净碳交换有显著的影响.

... 1 生态系统碳交换与环境因子的关系温度和水分是影响生态系统碳交换的重要环境因子^{[13,14,15,16]} ...

2004

0.0

... 温度通过影响光合作用酶活性、空气湿度控制气孔导度而影响植物光合作用^[17,18],而土壤水分则与土壤微生物活性、植物生理活性有关 ...

2011

0.0

. 2011, 31(17):4889-4899

Characteristics and controlling factors of photosynthesis in a maize ecosystem on the North China Plain

华北平原玉米田生态系统光合作用特征及影响因素

Tong X J , Li J , Liu D

同小娟, 李俊, 刘渡

Light-response parameters of plant photosynthesis are important indices characterizing ecosystem productivity. Gross primary production ( GPP ) is one of the most basic energetic and biogeochemical characteristics of an ecosystem. The study of plant photosynthesis at the canopy and ecosystem scales is improved by using micrometeorological methods such as the eddy covariance technique. To investigate photosynthesis and its light-response characteristics, CO 2 flux was continuously measured using the eddy covariance technique in a summer maize field on the North China Plain from 2003 to 2006. Net ecosystem carbon exchange ( NEE ) rose with increase in photosynthetically active radiation and their relationship was expressed by a rectangular hyperbola function. Light-response parameters and GPP showed temporal variation and generally peaked at the heading/grain filling stage. The seasonal mean initial light use efficiency (α), maximum photosynthesis rate ( P max ) and dark ecosystem respiration ( R d ) in the summer maize field varied from 0.054 to 0.124 μmol/μmol, from 1.72 to 2.93 mg CO 2 · m -2 · s -1 , from 0.23 to 0.38 mg CO 2 · m -2 · s -1 , respectively. Light-response parameters were significantly affected by maize growth. Monthly mean α, P max and R d rose exponentially with the increase in leaf area index ( LAI ). About 50% of the changes in α, P max and R d can be ascribed to the variation in LAI . Usually, weak light reaching the ground is mainly composed of scattered light. Under a large LAI , a suitable canopy structure was advantageous for absorbance of scattered light from all directions and led to a high use efficiency of weak light. In summer, the temperature was high and varied within a narrow range. The influence of temperature on R d was insignificant. LAI was the main factor controlling R d . Total seasonal GPP in the maize field was 806.2, 741.5, 703.0 and 817.4 g C/m 2 in 2003, 2004, 2005 and 2006, respectively. The interannual differences in GPP were largely attributable to climatic variation. Compared with the other years, the low GPP in 2005 was a result of the lower soil water content. Monthly mean GPP increased exponentially with an increase in air temperature ( P GPP variation. During the vegetative growth period, GPP increased significantly with increasing LAI ( P GPP and LAI was expressed by a rectangular hyperbola function. During the reproductive growth period, GPP decreased exponentially with declining LAI ( P LAI , GPP during the reproductive growth period was lower than that during the vegetative growth period, because of the decline in leaf chlorophyll content and the lower air temperature during the reproductive growth period.

采用涡度相关法对华北平原夏玉米田进行了连续4a(2003-2006年)的碳通量观测,结果表明:夏玉米田生态系统初始量子效率(α)、最大光合速率( P max )、暗呼吸速率( R d )和总初级生产力( GPP )随作物生长发育而变化。在夏玉米生育前期和后期,α 、P max 、 R d 和 GPP 都比较小,其最大值出现在抽穗期/灌浆期。2003-2006年,夏玉米生长季平均α 、P max 、 R d 的范围分别为0.054-0.124 μmol/μmol、1.72-2.93 mg CO 2 · m -2 · s -1 、0.23-0.38 mg CO 2 · m -2 · s -1 。α、 P max 和 R d 均随叶面积指数( LAI )增加呈指数增长。2003-2006年夏玉米生长季 GPP 总量分别为806.2、741.5、703.0、817.4 g C/m 2 ,年际差异较大。玉米田生态系统 GPP 随温度升高呈指数增长。在玉米营养生长阶段, GPP 随 LAI 增加而增大,两者之间的关系可用直角双曲线方程来表示;生殖生长阶段, GPP 随 LAI 降低而下降.相同 LAI 下,生殖生长阶段的 GPP 明显低于营养生长阶段。

... 温度通过影响光合作用酶活性、空气湿度控制气孔导度而影响植物光合作用^[17,18],而土壤水分则与土壤微生物活性、植物生理活性有关 ...

2016

0.0

. 2016, 35(6):1427-1434

Effects of warming and N addition on ecosystem carbon exchange in a desert steppe

模拟增温和氮素添加对荒漠草原生态系统碳交换的影响

Wu Q , Han G D , Wang Z W

武倩, 韩国栋, 王忠武

(College of Ecology and Environmental Science, Inner Mongolia Agricultural University, Hohhot 010018, China).

Global warming and atmospheric nitrogen (N) deposition are two of the most important global change drivers. In grassland ecosystem, increasing atmospheric temperature and nitrogen deposition are expected to modify the carbon sequestration; however, how warming and nitrogen addition affect ecosystem carbon exchange in the given conditions is unclear. The objective of this study was to assess the effects of global warming and N addition on C exchange of the desert steppe. A random split plot experiment (2×2 factors) in a desert steppe with dominant species of  Stipa breviflora  was conducted to mimic the climate warming using the infrared heaters and enrichment of nitrogen deposition by fertilizer addition. The gross ecosystem productivity (GEP), ecosystem respiration (ER) and net ecosystem exchange (NEE) were measured in different conditions. The integrated impact factors on ecosystem carbon exchange were analyzed during 2013 and 2014. The results showed that: (1) Warming significantly increased soil temperature and soil moisture about 0.70 ℃ ( P P P P >0.05). (3) In 2013, GEP peaked in early August, but ER reached peak during late August and early September, so NEE changed with GEP and ER. GEP, ER and NEE all peaked during late August and early September in 2014. (4) ER and GEP increased with the increasing air temperature and precipitation. Furthermore, soil temperature and soil moisture were also two of the most important factors affecting ecosystem carbon exchange.

气候变暖和大气氮沉降是全球变化的重要驱动因子。在草地生态系统中，气温升高和大气氮沉降都会改变草地固碳（C）状况，然而温度增加和大气氮沉降是如何影响生态系统碳交换目前还不明确。本研究旨在研究增温和氮素添加对荒漠草原碳交换的影响。在短花针茅荒漠草原上采用2×2因素完全随机区组的裂区设计，使用红外辐射器来模拟气候变暖并且使用添加氮肥的方法来模拟大气氮沉降，在不同处理条件下测定生态系统净碳交换（NEE）、生态系统呼吸（ER）和总生态系统生产力（GEP），分析了2013和2014年影响短花针茅荒漠草原生态系统C交换的因素，结果如下：（1）增温使土壤温度显著增加了0.70 ℃（ P P P P >0.05）。（3）2013年GEP在8月初达到峰值，ER在8月末9月初达到峰值，NEE随着GEP和ER的变化而波动；2014年GEP、ER和NEE均在8月末9月初达到峰值。（4）ER和GEP随着大气温度升高和降水增加而增大，土壤温度和土壤湿度也是影响生态系统C交换的重要因素。

... 武倩等^[19]的增温实验表明,增温使得植物冠层温度增加,光合作用增强,同时也增强了土壤微生物活性,增强了土壤呼吸进而使得ER增加 ...

2018

0.0

. 2018, 42(3):372-381 DOI:10.17521/cjpe.2016.0049

Effects of fencing on ecosystem carbon exchange at meadow steppe in the northern slope of the Tianshan Mountains

围栏封育对天山北坡草甸草原生态系统碳交换的影响

Hu Y , Zhu X P , Jia H T

胡毅, 朱新萍, 贾宏涛

1 College of Grassland and Environmental Sciences, Xinjiang Agricultural University, ürümqi 830052, China; 2 Xinjiang Key Laboratory of Soil and Plant Ecological Processes, ürümqi 830052, China;

Aims The carbon exchange between ecosystems and the atmosphere and its response to environmental factors is the focus of current research. The aim of this study was to examine the effects of fencing on ecosystem carbon exchange at meadow steppe in the northern slope of Tianshan Mountains. Methods The static box method with a LI-840 CO 2 /H 2 O infrared analyzer was used to evaluate daily and seasonal changes of ecosystem carbon exchange and their relationship with environmental factors in the inside fence and outside fence after 9 years fencing. Important findings We found the ecosystem carbon exchange inside the fence was significantly ( p 2 exchange ( NEE ) in the inside and outside of the fences were -7.62 and -6.63 μmol·m -2 ·s -1 , respectively; the maximum ecosystem respiration ( ER ) were 8.55 and 7.04 μmol·m -2 ·s -1 , respectively; and the maximum gross ecosystem productivity ( GEP ) were -14.66 and -13.89 μmol·m -2 ·s -1 , respectively. Due to the protection of fence, the vegetation in the fence was flourished with higher photosynthesis, and thus resulted in lower NEE . Meanwhile, organic carbon input enhanced ecosystem respiration. Besides, the ecosystem carbon exchange significantly correlated with the air temperature and soil temperature of 0 to 10 cm depth, and the correlation with the air temperature was higher than soil temperature of 0 to 10 cm depth. Also, the correlation in the inside of the fence was higher than that in the outside of the fence. Ecosystem carbon exchange had correlation with soil water content, but the correlation was slightly lower than that with soil temperature.

草本层和大气间的碳交换及其对环境因子的响应是目前研究的热点。该研究通过静态箱法, 采用LI-840 CO 2 /H 2 O红外分析仪, 对新疆天山北坡草甸草原围封9年的样地和围栏外自然放牧生态系统碳交换进行监测, 分析了围栏内外生态系统碳交换的差异性、日变化、季节变化及其与环境因子的关系。结果表明: 围栏内生态系统碳交换高于围栏外, 围栏内外表现出明显的差异性; 围栏内外生态系统碳交换均存在明显的日变化和季节变化规律, 呈单峰曲线, 且在植物生长季峰形比较明显。在整个监测期间, 围栏内外生态系统CO 2 净交换最小值分别为-7.62和-6.63 μmol·m -2 ·s -1 , 生态系统呼吸最大值分别为8.55和7.04 μmol·m -2 ·s -1 , 生态系统总初级生产力最大值分别为-14.66和-13.89 μmol·m -2 ·s -1 。因围栏内植被得到保护, 草本植物生长茂盛, 光合作用强, 生态系统CO 2 净交换较小, 同时有机碳的输入增强了生态系统呼吸。分析发现生态系统碳交换与气温和0-10 cm土壤温度显著相关, 与气温的相关性高于与0-10 cm土壤温度的相关性, 且围栏内禁牧处理相关性高于围栏外自然放牧草地; 土壤含水量与生态系统碳交换存在一定的相关性, 但其相关性略低于温度与生态系统碳交换的相关性。

... 胡毅等^[20]的研究则表明土壤含水量与NEE和GEP呈线性负相关关系, 与ER呈现指数相关关系 ...

1981

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2006

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... ER和GEP与环境因子之间存在极显著相关性,说明环境因子不直接影响生态系统净碳交换,而是通过影响生态系统呼吸和光合来间接影响净碳交换,这与伏玉玲等^[22]研究羊草(Leymus chinensis)草原的结果基本一致 ...

2018

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... ER和GEP与温度的相关性大于与水分的相关性,说明生态系统碳交换对温度的敏感性大于水分,这与靳宇曦等^[23]关于短花针茅(Stipa breviflora)荒漠草原的研究结果基本一致,即土壤温度对生态系统净碳交换的贡献大于土壤湿度 ...

2013

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. 2013, 21(1):3-10

Effects of grazing on the net ecosystem exchange of carbon dioxide in grassland ecosystems (research review)

放牧对草地生态系统CO 2 净气体交换影响研究概述

Zhu L L , Rong Y P , Wang W G

朱玲玲, 戎郁萍, 王伟光

Institute of Grassland Science, College of Animal Science & Technology, China Agricultural University, Beijing 100193, China

The net ecosystem exchange of carbon dioxide (NEE) between terrestrial ecosystems and atmosphere is a major component of carbon cycle of terrestrial ecosystems called "breathing" of the terrestrial biosphere, and is great concerned in the research of global climate change. Grasslands, as a major component of the terrestrial ecosystems, comprising approximately 40% of the world's terrestrial surface, is sensitive to climate change. Grazing plays a significant role in the land use and management of grasslands. With the change in global climate, the impacts of different grazing intensities on grazing ecosystems have different ways. In this review, the effects of grazing on the characteristics of NEE in grassland ecosystems are focused in general based on factors in NEE composition and the pathways of grazing effects on NEE in grasslands. Grazing mainly disturbs the soil-vegetation interface of grasslands then affects grassland NEE through the disturbances on 1) plant, including effects on plant community composition, above and below-ground net primary production and litter; 2) soil, including the effects on soil respiration, soil nutrients especially soil carbon and nitrogen, soil temperature and moisture. The pathways of grazing effects on grasslands can also be applied in disturbances such as cultivation and defoliation and is of great importance in the investigating of NEE characters and carbon flux of different grassland ecosystems, particularly grasslands in different land-use, whether in carbon source or sink in certain degrees and their carbon storage capacity.

陆地生态系统与大气之间的CO 2 净气体交换(net ecosystem exchange of carbon dioxide,NEE)被称为生物圈的呼吸,它是陆地生态系统碳循环的重要组分,是全球气候变化研究的重点。草地生态系统是陆地生态系统的主体,约占陆地表面的40%,是气候变化的敏感区域。放牧是草地生态系统的主要利用方式,伴随着气候变化,放牧利用强度不同,对草地生态系统NEE的影响也不同。本文以放牧草地生态系统NEE组成为基础,从放牧干扰途径出发,综述了放牧对草地生态系统CO 2 净气体交换特征的影响。放牧主要干扰草地土壤-植被界面,通过影响植物群落组成、地上净初级生产力、地下净初级生产力来影响植被群落的光合作用和呼吸作用,使草地生态系统的NEE发生变化;放牧也可通过影响土壤包括土壤呼吸、土壤养分以及土壤温度和水分来影响NEE。放牧干扰途径的研究亦可应用于草地开垦和刈割等利用方式中,这对了解和研究草地不同利用方式下生态系统的CO 2 交换特征、草地碳源或碳汇的转换状态,以及草地碳贮存功能的强弱具有重要意义。

... 2 放牧对生态系统碳交换的影响放牧家畜主要通过采食和践踏直接影响植物群落组成、地上生物量(或地上净初级生产力)、凋落物而影响NEE^[24],此外,还会引起土壤温度和土壤水分平衡的反馈,最终影响净碳吸收^[25] ...

2004

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2012

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. 2012, 21(6):8-14 DOI:10.11686/cyxb20120602

Response of soil respiration to grazing intensity, water contents, and temperature of soil in different grasslands of Inner Mongolia

内蒙古不同草原类型土壤呼吸对放牧强度及水热因子的响应

Yang Y , Han G D , Li Y H

杨阳, 韩国栋, 李元恒

土壤呼吸的测定对于预测不同生态系统碳收支起着关键性作用。本研究利用Ｌｉ８１００开路式碳通量测定系统，对内蒙古荒漠草原、典型草原和草甸草原生态系统在不同放牧强度（零放牧的对照、轻度放牧、中度放牧和重度放牧）下土壤呼吸速率进行测定，并分析了土壤呼吸与土壤温度（１０ｃｍ处）和空气相对湿度的相关性。结果表明，草地类型、放牧强度及它们的交互作用都对土壤呼吸有显著影响（ P ＜０．０５），放牧强度对土壤呼吸的影响主要表现在荒漠草原和典型草原生态系统，对草甸草原没有显著影响。在不同草地生态系统中，随着放牧强度的增加，土壤呼吸速率呈先升高后降低的变化规律。方差结果显示，不同草原类型的土壤１０ｃｍ温度和空气相对湿度有极显著性的差异（ P ＜０．００１），不同放牧强度对土壤１０ｃｍ温度和空气相对湿度无显著性影响。

... s^-1,表明在季节尺度上围封样地的碳吸收速率大于放牧样地,原因是围封后植被得以恢复^[26] ...

2004

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... 因为地上生物量减少,导致每年的凋落物及立枯物较少,从而使得土壤C、N含量减少^[27],且地上植被是根系获得能量的途径,地上植被的减少必然影响到植被地下根系,进而影响根系呼吸,而根呼吸是土壤呼吸的重要组成部分^[28] ...

2014

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. 2014, 22(6):1227-1231 DOI:10.11733/j.issn.1007-0435.2014.06.012

Response of soil respiration to experimental warming and nitrogen addition in inner mongolia desert steppe

内蒙古荒漠草原土壤呼吸对模拟增温和氮素添加的响应

Zhang Y , Hong M

张宇, 红梅

College of Ecology and Environmental Science of lnner Mongolia Agriculture University, Hohhot, Inner Mongolia 010019, China

The effects of experimental warming and nitrogen addition on soil respiration were investigated using Li-8100 soil carbon flux measuring system in the desert steppe of Inner Mongolia. The results showed that infrared radiator raised soil temperature obviously in 2010 and 2011, and the temperature of 0~30 cm soil layer was 0.4~1.0℃ higher than control. The experimental warming didn't change the soil moisture significantly. Both nitrogen addition and warming didn't change soil respiration significantly. The rate of soil respiration had significant seasonal variation, ranging from 0.15 to 3.66μmol CO 2 ·m -2 ·s -1 . There was strong correlation between soil respiration and precipitation, and between soil respiration and the moisture of 10 cm soil layer, the correlation coefficients were 0.67 and 0.70, respectively.There was strong water stress occurred in the desert steppe of Inner Mongolia, so soil moisture was the predominant factor of affecting soil respiration. Nitrogen addition had no obvious effect on soil respiration.

以内蒙古荒漠草原为研究对象,采用Li-8100土壤碳通量测量系统测定法,研究了控制性增温和氮素添加对荒漠草原土壤呼吸的影响.研究表明:红外辐射加热器在2年间显著提升了试验样地的土壤温度,0~30 cm土壤温度的增幅达0.4~1.0℃;但增温未能显著改变0~30 cm土壤湿度,也未能促进土壤呼吸;施氮、增温＋施氮的交互作用都未显著改变试验样地的土壤呼吸值.试验期间,土壤呼吸存在明显的季节变化,其变化幅度为0.15~3.66 μmol CO 2 ·m -2 ·s -1 .土壤呼吸与降水量和10 cm土壤含水量存在较强的相关性,相关系数分别达0.67和0.70.内蒙古荒漠草原存在明显的水分胁迫,这使得土壤湿度取代土壤温度成为控制土壤碳通量的主要环境因子,而施加矿质氮肥对土壤呼吸的影响不显著.

2008

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. 2008, 32(6):1301-1311 DOI:10.3773/j.issn.1005-264x.2008.06.011

Effects on carbon flux of conversation of grassland steppe to cropland in China

开垦对克氏针茅草地生态系统碳通量的影响

Zhang W L , Chen S P , Miao H X

张文丽, 陈世苹, 苗海霞

1College of Chemistry and Life Science, China Three Gorge University, Yichang, HuBei 443002, China;2State Key Laboratory Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China

Aims In light of increasing interest in understanding carbon fluxes of terrestrial ecosystems under changing climate and escalating human influences, our study examined the dependence of carbon fluxes on abiotic and biotic factors and explored the effects of conversion of grassland to cropland on eco-system C fluxes. Methods Our study was carried out in Duolun (42o02′ N, 116o17′ E; 1 350 m asl), a semiarid agriculture-pasture transition region in southeastern Inner Mongolia, China. We used the chamber method during the growing season. Important findings There was no difference in net ecosystem exchange of carbon dioxide ( NEE ) between wheat field and steppe at the beginning of the growing season. NEE of wheat field became higher than that of steppe in late June. No differences were found between the two ecosystems from mid-July to August 1st. NEE of wheat field became significantly lower than that of steppe starting in mid-August. During the growing season, the maximum of NEE in steppe was –11.26 µmol CO 2 &# 8226;m –2 &# 8226;s –1 , while that in wheat field was –12.29 µmol CO 2 &# 8226;m –2 &# 8226;s –1 . Mean NEE in steppe (–5.33 µmol CO 2 &# 8226;m –2 &# 8226;s –1 ) was a little lower than that in wheat field (–7.66 µmol CO 2 &# 8226;m –2 &# 8226;s –1 ). Leaf area index ( LAI) was the main factor controlling NEE of the two ecosystems. Poor soil nutrient levels also might limit NEE in these ecosystems. Because of characteristics of wheat, the sensitivity of NEE response to LAI was lower in wheat field than steppe in the middle and late growing season. Lower soil volume water content (10 cm depth) in wheat field limited total ecosystem respiration (TER) and decreased the sensitivity of TER to temperature.

植被–大气间CO 2 净交换及其对环境变化的响应是目前全球变化研究的热点问题。该研究通过同化箱式法, 在内蒙古农牧交错带对比研究生长季草地生态系统和耕种多年的小麦田生态系统碳通量的变化, 以探讨该地区碳通量的变化规律及影响碳通量主要因子, 并揭示农田开垦对草原碳通量的影响。结果显示: 两个生态系统的群落净气体交换(Net ecosystem exchange, NEE )有明显的季节变化。整个测定期间, 草地生态系统的净气体交换NEE的最高值为–11.26 µmol CO 2 &# 8226;m –2 &# 8226;s –1 , 平均群落净气体交换为–5.33 µmol CO 2 &# 8226;m –2 &# 8226;s –1 ; 小麦田群落NEE最大值为–12.29 µmol CO 2 &# 8226;m –2 &# 8226;s –1 , 平均群落净气体交换为–7.66 µmol CO 2 &# 8226;m –2 &# 8226;s –1 。分析发现, 叶面积指数 LAI 是影响该地区生态系统 NEE 的主要因子, 相对贫瘠的土壤也是限制该地区生态系统碳固定的一个重要因子。因小麦的生长特性, 在生长中后期, 小麦田生态系统 NEE 随 LAI 的变化没有草地生态系统的敏感。此外, 较低的土壤含水量限制了小麦田群落呼吸, 使得小麦田群落呼吸对温度的敏感性降低。

... 因此,围封通过增加群落地上、地下生物量进而增强了群落总呼吸^[29] ...

2015

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. 2015, 50(5):605-613 DOI:10.11983/CBB15064

Effect of grazing on diurnal and seasonal dynamics of soil respiration rate of Leymus secalinus communities

放牧对赖草草地土壤呼吸日、季动态的影响

Zhu H S , Li G , Dong K H

朱慧森, 李刚, 董宽虎

1 College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu 030801, China 2 Institute of Loess Plateau, Shanxi University, Taiyuan 030006, China

Soil respiration, as a key process in soil CO 2 emission, is strongly affected by land-use change. To explore the factors affecting carbon cyclic processes of Leymus secalinus communities under grazing, we measured diurnal and seasonal dynamics of soil respiration by the closed static chamber technique (LI-840a) during 2012 and 2013 to provide some basis for the rational use of L. secalinus communities. Furthermore, we analysed the correlation of soil respiration and air temperature, soil temperature, and soil moisture content. Diurnal and seasonal dynamics of soil respiration rate showed a unimodal distribution, with the peak value occurring at about 13:00 and the lowest at 4:00; the peak soil respiration rate appeared in July and August and the lowest in May, June and September. During the growing season, grazing could reduce the soil respiration rate, but the trend in rate did not significantly change. Diurnal dynamics of soil respiration rate was significantly correlated with air temperature. Seasonal dynamics of soil respiration rate was mainly regulated by the temperature of the 0- to 10-cm soil layer. We found an exponential model that could simulate the relationship between soil respiration rate and surface-layer temperature. Using the model, the caculated R s were 1.040 8e 0.086 Ts (fencing plots) and 1.016e 0.075 2 Ts (grazing plots). Temperature was the main factor affecting the soil respiration rate of L. secalinus communities, and grazing could decrease the soil respiration rate by changing the surface layer temperature.

土壤呼吸是土壤碳向大气排放的关键过程, 受土地利用变化的强烈影响。利用LI-840a静态箱法, 对放牧利用下赖草( Leymus secalinus )草地土壤呼吸速率日、季动态进行为期2年(2012–2013)的观测, 并分析其与大气、土壤温度和土壤含水量的相关性, 旨在为合理利用赖草草地提供依据。结果表明, 赖草草地土壤呼吸日、季动态均呈单峰型变化, 一天中的最高值出现在午间13点, 凌晨4点最低, 在生长季初的5–6月和生长季末的9月较低, 在生长旺盛期7–8月较高。放牧降低了土壤呼吸速率, 但并不改变土壤呼吸速率的变化趋势。土壤呼吸速率日变化与大气温度呈显著相关( P R s =1.040 8e 0.086 Ts ( R 2 =0.91, P R s =1.016e 0.075 2 Ts ( R 2 =0.95, P