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地理研究 >

2016 , Vol. 35 >Issue 2: 271 - 284

DOI: https://doi.org/10.11821/dlyj201602006

研究论文

内蒙古草地NPP变化特征及其对气候变化敏感性的CENTURY模拟研究

  • 郭灵辉 , 1 ,
  • 郝成元 , 1 ,
  • 吴绍洪 2, 3 ,
  • 赵东升 2, 3 ,
  • 高江波 2, 3
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  • 1. 河南理工大学测绘与国土信息工程学院,焦作 454000
  • 2. 中国科学院地理科学与资源研究所,北京 100101
  • 3. 中国科学院陆地表层格局与模拟重点实验室,北京 100101
通讯作者：郝成元（1969- ）,男,山东曹县人,教授,主要从事矿区生态学与区域环境变迁研究。E-mail:

作者简介：郭灵辉（1983- ）,男,河南宜阳人,博士,主要从事气候变化与生态系统风险评估研究。E-mail:

收稿日期: 2015-07-16

  要求修回日期: 2015-12-08

  网络出版日期: 2016-02-20

基金资助

国家十二五科技支撑计划（2012BAC19B04,2012BAC19B10）

国家重点基础研究发展计划（973计划）（2011CB403206）

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Analysis of changes in net primary productivity and its susceptibility to climate change of Inner Mongolian grasslands using the CENTURY model

  • GUO Linghui , 1 ,
  • HAO Chengyuan , 1 ,
  • WU Shaohong 2, 3 ,
  • ZHAO Dongsheng 2, 3 ,
  • GAO Jiangbo 2, 3
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  • 1. School of Surveying and Land Information Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China
  • 2. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
  • 3. Key Laboratory of Land Surface Pattern and Simulation, CAS, Beijing 100101, China

Received date: 2015-07-16

  Request revised date: 2015-12-08

  Online published: 2016-02-20

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《地理研究》编辑部
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摘要

气候变化及其对植被净初级生产力的影响是全球变化研究的核心内容之一。基于空间化的CENTURY生物过程模型,分析1981-2010年内蒙古草地净初级生产力（NPP）的时空演变规律及其对关键气候因子的敏感性特征。结果表明：近30年内蒙古草地大部分区域NPP呈下降态势但趋势并不显著,全区平均降速约为1.17 g C/m2·a;NPP年代际变化时空差异较大,1980s至1990s约69.65%的区域NPP下降,1990s至2000s NPP下降加剧,下降面积较前者扩大了17.50%;NPP对降水与温度的敏感性特征空间异质性较强,但总体上区域降水减少可能是近30年内蒙古草地NPP下降的主要因素,温度升高同样会导致草地NPP下降,但作用程度较小。

关键词： 气候变化; 草地; 净初级生产力（NPP）; 敏感性; 内蒙古

本文引用格式

郭灵辉 , 郝成元 , 吴绍洪 , 赵东升 , 高江波 . 内蒙古草地NPP变化特征及其对气候变化敏感性的CENTURY模拟研究[J]. 地理研究, 2016 , 35(2) : 271 -284 . DOI: 10.11821/dlyj201602006

Abstract

Climate change significantly influences regional terrestrial carbon balances. The grasslands of Inner Mongolia, located within the mid-Eurasian continental steppe zone, play an important role in the study of global change processes in the context of their particular geographical location, characterized by climatic variability and a complex natural environment. In this study, a CENTURY-based modeling system (converting the CENTURY model from a site-based model to a spatial model) was used to investigate climate change -- driven spatiotemporal variations in the vegetation net primary production (NPP) within Inner Mongolian grasslands from 1981 to 2010. Our simulation indicated that the NPP has decreased over the majority (88.62%) of the Inner Mongolian grasslands since 1981, at an average rate of 1.17 g C/m2·a over the entire area. However, there is significant decadal variability. From the 1980s to 1990s, some 69.65% of the domain experienced a reduction in the decadal average NPP, while the NPP decreased over 81.84% of the total area from the 1990s to 2000s, suggesting the worsening status of vegetation in recent decades. At the regional scale, changes in precipitation and temperature respectively accounted for 78% and 22% of the NPP decrease; however, their relative contributions were not constant across the study area or across different grassland types.

Key words： climate change; grasslands; NPP; susceptibility; Inner Mongolia

1 引言

草地作为地球上分布最广的植被类型之一,在全球气候变化研究领域占据非常重要的地位[1-4]。探讨草地生态系统碳循环机制,估算其碳收支变化,对系统分析草地植被在全球气候变化中的生态价值以及全球碳收支平衡具有重要意义,也是目前国际地圈—生物圈研究计划中碳循环研究的重要组成部分[5,6]。植被净初级生产力反映植物固定和转化光合产物的效率,表征着植被群落的生产能力与生态系统的健康状况[7],是估算地球支持能力和评价陆地生态系统可持续发展的重要生态指标,也是碳元素生物地球化学循环的重要环节,在全球变化以及生态系统碳循环中扮演着重要角色[8]。植被净初级生产力及其对气候变化的敏感性研究一直是全球变化与陆地生态系统的核心内容之一[9-11],已成为全球变化中的热点问题[12]。
内蒙古草地约占全区土地面积的3/4,占全国天然草地面积的1/5,在维护区域乃至全国生态环境稳定、畜牧产品供给以及经济建设方面起着重要作用[13-15]。该区地处东亚季风区的北缘,属干湿气候过渡带,气候变率大,近50年该区增温速率约0.4 ℃/10 a[16,17],变化幅度远远超过中国大陆平均增温水平,是中国气候变化敏感的区域之一[18],这使得气候变化对内蒙古草地净初级生产力的影响研究成为学者和决策者共同关注的话题[19-22]。
然而,由于观测站点数量有限,无法在区域尺度上直接和全面地测量植被的生产能力,因此,利用模型估算陆地植被的生产力已成为一种重要而且被大多数学者们所接受的研究方法[6]。在当前众多的生态模型中,CENTURY模型是基于草地生态系统发展起来的,能够较好地模拟草地生态系统的碳循环过程,已在全球草地生态系统中得到广泛应用[23,24]。目前,该模型已成功应用于气候变化对内蒙古草地生态系统植被净初级生产力的影响研究,但多局限于对特定草地类型点尺度的探讨,全面系统地分析区域气候变化对内蒙古草地净初级生产力的影响有待加强[25-27]。
本文以内蒙古草地生态系统为对象,基于对国家气象台站站点数据的空间插值,运用空间化后的模型CENTURY,分析探讨气候变化下1981-2010年内蒙古草地生态系统NPP时空演变规律,并借助情景分析方法初步辨析NPP对关键气候因子的敏感程度,以期为进一步认识气候变化对内蒙古草地的影响提供理论依据,也为该区畜牧业适用性管控提供参考。

2 研究方法与数据来源

2.1 CENTURY模型及其空间化

CENTURY模型是由美国科罗拉多州立大学开发的,以气候、人类活动、土壤性状、植物生产力以及凋落物和土壤有机质分解等之间的相互关系为基础而建立的草地生态系统生物地球化学循环模型[1,28]。该模型是从草地生态系统发展起来的,已在全球草地生态系统中得到广泛应用,包括中国主要草原区[23,27,29]。CENTURY模型的运行以月为时间步长,主要输入参数包括4类：① 地理位置参数,包括经度、纬度等;② 气候参数,包括月降水量、月平均最高气温和月平均最低气温等;③ 土壤参数,包括土壤层深度、质地、容重、pH值,初始土壤C、N、P、S水平等;④ 植被参数,主要包括植被类型、植物物候、植物生长最适宜温度和最高温度等。
CENTURY 4.5模型是一个基于点尺度的生物地球化学循环模型,每次运行都需要用户手动输入参数并通过DOC命令行进行设置和进程控制,无法满足本文的研究需求。为此,本文通过编译程序实现其空间化。具体过程为：首先,构建空间栅格参数集,将模型所需的气候数据、土壤数据、地点数据以及植被类型参数插值成统一的栅格数据;然后,根据同一草地类型具有较为相似的生物学特征这一原理,选择三大草地类型中面积占优的优势种代表性样点,通过CENTURY模型参数敏感性分析,筛选出样点模拟结果与实测数据线性关系最为一致的优势种参数设置方案,以此构建以草地类型为单元的植被生理参数体系;之后,逐个格点调用CENTURY模型主程序进行模拟,并根据空间模拟效果来检验、反馈空间化过程参数,进而开展空间模拟（图1）。当然,由于草地生态系统植物种类较多,其时空格局变化涉及众多复杂的生物与非生物因素,而在大中尺度的生态模拟中往往不可避免的要对其某些生态过程、参数进行简化,本文受数据可获得性的限制,仅就草甸草原、典型草原以及荒漠草原等主要草地类型设置了相应的植被参数,并没有根据物种特性进行细化。
Fig. 1 The diagrammatic sketch of complying CENTURY model from a site-based model into spatial model

图1 CENTURY模型空间化过程示意图

2.2 数据来源与预处理

草地类型数据来自于中国科学院1:100万植被图集,参照中华人民共和国农业部畜牧兽医司和全国畜牧兽医总站主编的《中国草地资源》进行分类。由于草甸受局部隐域环境影响较大,而荒漠区域植被覆盖较低,波动大,本文主要关注内蒙古自治区草甸草原、典型草原、荒漠草原等主要草原类型,并运用ArcGIS将草地类型数据转化为栅格图,空间分辨率为8 km,同时为了尽量降低混合像元对模拟效果的影响,本文仅考虑草原面积超过50%的栅格（图2）。空间化模拟所需的主要输入参数及数据来源如表1所示。气候数据源于1981-2010年内蒙古自治区境内及内蒙古周边92个气象台站（图2）月数据集（平均温度、最高温度、最低温度以及降水量等）,该数据来自于中国气象局中国气象科学数据共享服务网,然后使用澳大利亚ANUSPLIN 4.3插值软件进行空间插值,插值方法选择样条函数法,空间分辨率设为8 km,插值过程中主要考虑经纬度变化的影响,同时在对温度插值过程中也考虑了高程的影响,插值效果较好[30];土壤质地、容重以及pH值等土壤属性数据来自于联合国粮农组织（FAO）和维也纳国际应用系统研究所（IIASA）所构建的土壤数据库（Harmonized World Soil Database,HWSD）,并通过重采样得到与草地分布和气候数据空间分辨率一致的土壤要素空间图;大气干湿氮沉降系数和非生物固氮系数等外部养分输入参数主要参照相关文献[25-27];参照CENTURY模型植被参数说明文件,并结合代表性样地参数敏感性调试与验证获得植被参数集;大气CO2浓度数据来自美国夏威夷Mauna Loa的观测资料数据。
Tab. 1 Input parameters of the CENTURY-based spatial model

表1 CENTURY模型空间模拟所需的主要输入参数及数据来源

Fig. 2 The distribution of the major grassland types in Inner Mongolia and the 92 meteorological stations

图2 内蒙古主要草地类型分布及所选气象站点

2.3 情景设置

首先以1961-2010年气候插值数据多年平均值来驱动模型,使其运行5000年达到平衡状态,然后根据1961-2010年气候插值月数据和CO2数据重新驱动模型模拟分析气候变化下内蒙古草地NPP演变特征,而1961-1980时段的模拟仅为1981-2010年提供一个较为真实的初始输入参数（土壤养分、水分等）（记作S3）。为进一步辨析草地NPP对关键气候因子（温度和降水）的敏感性程度,参照已有研究[31-33],在1981-2010年设置了另外2个模拟方案：方案一（S1）,仅降水变化,温度与CO2保持不变;方案二（S2）,仅温度变化,而降水和CO2保持不变,如表2所示。最后,将不同方案下（S1、S2）生态系统NPP变化趋势率与S3方案下的NPP变化趋势率之比值定义为草地NPP对相应气候因子（降水、温度）的敏感程度[34]。趋势率以最小二乘法线性拟合的斜率来表示,正值表示增加趋势,正值越大表示增速愈快,否则相反。
Tab. 2 Experiment scheme design

表2 敏感性实验方案

实验名称 降水变化 温度变化 CO2变化 模拟时段
S1 √ 1981-2010
S2 √ 1981-2010
S3 √ √ √ 1961-2010

3 结果分析

3.1 模型模拟效果评价

区域NPP模拟效果评价一直是一个非常困难的问题,一方面NPP的实测数据获取比较困难,另一方面实测点尺度数据也很难推广到区域尺度。为验证空间化后CENTURY模型的适用性,本文根据已有研究[35],首先利用均一化植被指数数据对面上模拟结果变化趋势进行验证。从图3可以看出,从变化趋势来看,无论是草地全区还是具体草地类型年NPP均与年平均NDVI具有很好的一致性（相关系数在0.5及以上）,NDVI较大年份往往对应NPP模拟值极大年,极小年也基本对应NPP极小年。NDVI是反映气候变化和人为因素共同作用下牧草的总体生长状况,而本文中NPP的模拟没有考虑人为因素的影响,两者存在部分差异在所难免。
Fig. 3 Inter-annual variations of the annual NPP in the Inner Mongolia grasslands and corresponding NDVI

图3 内蒙古草地年NPP模拟值与同期NDVI年平均值时间变化特征

采用与他人研究成果对比的方法进一步探讨模型模拟能力。从空间分布上,本文1981-2010年内蒙古草地NPP模拟结果的均值（图4）与陶波等[36-38]关于内蒙古草地NPP的研究结果在数值与分布上较为一致。1981-2010年内蒙古草地NPP平均值约为161.05 g C/m2·a,略高于李刚等[39]利用光能利用率模型估算的1982-2003年内蒙古草地生长季NPP的结果（132.29 g C/m2·a）、孙睿等[40]利用光能利用率模型模拟的中国草原NPP结果（116 g C/m2·a）与朴世龙等[41]利用CASA模拟的中国温带草原草甸NPP结果154 g C/m2·a,但低于王国成等[42]通过CASA模型估算的内蒙古草地1981-2001生长旺季NPP的结果（192.0 g C/m2·a）。就草地类型而言,模拟的1981-2010年中,典型草原的多年平均值为151.22 g C/m2·a,与陈四清[43]模拟1978-2000年内蒙古大针茅群落的NPP结果159.26 g C/m2·a和羊草群落NPP结果161.85 g C/m2·a较为相近（表3）。这在一定程度上说明空间化的CENTURY模型能够较好地模拟内蒙古草地生态系统NPP动态变化,研究时段、范围以及所用模型结构的差别可能是差异产生的主要原因。
Fig. 4 Spatial distribution of the mean annual NPP over the Inner Mongolia grasslands during 1981-2010

图4 1981-2010年内蒙古草原NPP均值空间分布

Tab. 3 Comparison of CENTURY based modeling and other researchers' results on NPP in grassland

表3 年均净初级生产力与其他研究结果比较

3.2 近30年NPP变化特征

（1）区域尺度
从时间序列上来看,1981-2010年内蒙古各草原NPP变化趋势相似,年际变化较大（图5）。具体而言,1981-2010年内蒙古草甸草原NPP平均值最大,为353.23 g C/m2·a,变化范围在243.90~465.56 g C/m2·a之间;典型草原与荒漠草原NPP较小,多年平均值分别为151.22 g C/m2·a和65.03 g C/m2·a,变化范围分别为124.08~178.03 g C/m2·a和23.73~93.87 g C/m2·a。1981-2010年内蒙古草原NPP均呈显著下降趋势,其中草甸草原NPP在波动中降低速率最大,为2.94 g C/m2·a,荒漠草原最小,仅为0.73 g C/m2·a,草原全区下降趋势约为1.17 g C/m2·a。
Fig. 5 Interannual changes of the annual NPP in the Inner Mongolia grasslands from1981 to 2010

图5 1981-2010年内蒙古草原NPP年际变化特征

从年代际来看,1980s、1990s和2000s内蒙古全区草原NPP分别为169.64 g C/m2·a、165.95 g C/m2·a、147.57 g C/m2·a,其中1980s NPP变化不大,而近20年明显下降,2000s下降幅度为11.08%。不同草原类型间,NPP年代际变化趋势与全区一致,其中1990s荒漠草原NPP下降幅度最大,为6.57%,而2000s草甸草原NPP降低幅度更为明显,为14.83%（表4）。
Tab. 4 Interdecadal variations of the annual NPP in the Inner Mongolia grasslands from 1981 to 2010

表4 1981-2010年内蒙古草原年代际NPP变化特征

草原
类型		 平均值（g C/m2·a）/变化幅度（%）
1980s 1990s 2000s
草甸草原 372.74 371.00/-0.47 315.96/-14.83
典型草原 158.29 154.51/-2.39 140.86/-8.83
荒漠草原 71.20 66.52/-6.57 57.35/-13.79
全区 169.64 165.95/-2.18 147.57/-11.08
（2）空间格局
图6为1981-2010年内蒙古草原NPP变化趋势空间分布特征,从图6可以看出,30年来内蒙古草原NPP变化趋势空间差异较大。NPP增加区域约占总面积的11.38%,仅分布在鄂尔多斯市部分地区、呼伦贝尔市陈巴尔虎旗以及鄂温克族自治旗一带,而在锡林郭勒盟中部、东部、兴安盟以及通辽等地NPP下降趋势明显,速率超过2 g C/m2·,其他地区也均有不同程度的降低,速率在1 g C/m2·a左右。从草原类型角度看,草甸草原NPP下降迅速,64.65%的区域减速在2 g C/m2·a以上,典型草原与荒漠草原也以下降趋势为主,但降速主要波动在0~2 g C/m2·范围内,分别占各自面积的73.06%和96.09%。
Fig. 6 Spatial distributions of trends in annual NPP over the Inner Mongolia grasslands from 1981 to 2010

图6 1981-2010年内蒙古草原NPP变化趋势空间分布

从年代际空间变化来看（图7）,额尔古纳市—陈巴尔虎旗—新巴尔虎左旗一带、锡林郭勒盟的西乌珠穆沁旗与锡林浩特市南部地区以及赤峰市大部等草原NPP由1980s到1990s增加明显,增加幅度在0~10%左右,部分地区可达10%~20%,而同时段内,大部分草原（约69.65%）NPP呈下降态势,尤其在巴彦淖尔、包头以乌兰察布市的荒漠草原区,降幅达10%~20%。进入2000s以后,NPP降低区域扩大,约占81.84%,其中大兴安岭—阴山以北地区下降幅度多在20%以上,约占全区面积的21.75%,该线以南NPP降低幅度多在10%以下（表5）。1980s-1990s内蒙古荒漠草原、典型草原和草甸草原分别约82.15%、69.07%和53.58%的区域NPP在下降,且均以降幅低于10%为主,分别各自面积的55.21%、64.06%与49.25%。1990s-2000s,各大草原NPP下降程度加剧,分别有87.44%,76.74%和97.83%的草原NPP降低,其中荒漠草原与草甸草原降幅以10%~20%为主,分别占各自面积的36.2%和42.68%,典型草原依然以低于10%为主;降幅超过20%以上的区域,也分别由1980s-1990s的0.22%、0.05%、0增加到1990s-2000s的26.78%、19.46%以及25.12%（表5）。
Fig. 7 Variation of decadal average NPP in the Inner Mongolia grasslands during 1981-2010

图7 1981-2010年内蒙古草原NPP年代际均值变化幅度空间分布

Tab. 5 Amplitude of variation in decadal average NPP over the Inner Mongolia grasslands during 1981-2010

表5 1981-2010年内蒙古草原NPP年代际均值变化幅度比例构成

草原
类型		 年代 百分比（%）
<-20% -20%~-10% -10%~0 0~10% 10%~20% >20%
荒漠
草原		 1980s-1990s 0.22 26.72 55.21 13.55 4.08 0.22
1990s-2000s 26.78 36.20 24.46 11.29 1.27
典型
草原		 1980s-1990s 0.05 4.96 64.06 30.35 0.55 0.03
1990s-2000s 19.46 27.07 30.21 12.08 11.16 0.02
草甸
草原		 1980s-1990s 4.33 49.25 38.94 7.49
1990s-2000s 25.12 42.68 30.03 2.16
全区 1980s-1990s 0.08 9.37 60.20 28.05 2.23 0.07
1990s-2000s 21.75 31.09 29.00 10.56 7.59 0.01

3.3 NPP对气候因子的敏感性

（1）区域尺度
图8为不同模拟方案下1981-2010年内蒙古草原NPP距平年际变化特征。如图8所示,在S3方案下1981-2010年内蒙古草原NPP呈现显著下降趋势,下降速率为1.17 g C/m2·a（P<0.05）。在S1与S2方案下近30年来内蒙古草原NPP均有所下降,其中S1方案下NPP下降速率为0.91 g C/m2·a（P<0.05）,大于S2方案下降低速率,并且S1与S3情况下NPP年际变化规律一致,相关系数达0.9以上（P<0.01）,这说明从区域整体角度上看,区域降水可能是1981-2010年内蒙古草原NPP变化的主要影响因素,相对作用为78%。从草原类型上分析,降水是内蒙古荒漠草原、典型草原与草甸草原NPP降低的主要驱动因素,作用比值分别为73%、85%和69%,且S1方案下NPP年际变化规律与S3方案下NPP年际变化规律最为一致;温度升高同样会导致不同草原NPP下降,但是其作用程度远低于降水（图8）。
Fig. 8 Spatial distribution of trends in annual NPP derived by different simulation scenarios over the Inner Mongolia grasslands from 1981 to 2010

图8 不同模拟方案下1981-2010年内蒙古草原NPP距平年际变化特征

（2）空间格局
气候变化下近30年内蒙古草原大部分地区NPP呈下降趋势,主要因降水减少所致（图9）。在S1和S3方案下,锡林郭勒盟中部、东部、兴安盟以及通辽等地NPP减少趋势明显,减少速率在2 g C/m2·a以上,其他地区也均有不同程度的减少,速率在1 g C/m2·a左右,而NPP增加的区域主要分布在鄂尔多斯市部分地区以及呼伦贝尔市陈巴尔虎旗周边一带。在S2方案下,近30年来内蒙古草原西北半部NPP整体下降,而东南半部增加为主,变化速率主要集中在0~1 g C/m2·a之间。本文将导致NPP变化速率最快的因素定义为主要驱动因素（图9d）。由此可见,内蒙古草原区大部分地区NPP的变化主要受制于降水的变化,而呼伦贝尔市陈巴尔虎旗以及鄂温克族自治旗一带NPP增加可能是因为温度升高所致。
Fig. 9 Spatial distributions of trends in annual NPP (a-c) and their dominant driving factors (d) of grasslands over Inner Mongolia from 1981 to 2010

图9 不同模拟方案下1981-2010年内蒙古草原NPP变化趋势（a-c）与主要驱动因素空间分布（d）

4 结论与讨论

模拟结果显示：内蒙古草地NPP空间上总体呈现从东北向西南递减的趋势,大兴安岭西侧草甸草原区NPP最高,一般在200~450 g C/m2·a,鄂尔多斯市、锡林郭勒盟大部以及呼伦贝尔市西北部等典型草原NPP多在100~200 g C/m2·a,巴彦淖尔市、包头市、乌兰察布以及锡林郭勒盟西北等部分地区荒漠草原的NPP较低,多为0~100 g C/m2·a,与已有研究结果比较一致[36,38]。从区域平均角度,本文估算的内蒙古草原1981-2010年NPP平均值与已有研究较为一致[39,41,43]。这在一定程度上说明利用空间化后的CENTURY模型模拟内蒙古草地生态系统NPP动态变化的可行性。
气候变化对于草地植被的生长有着重要的影响。李兴华等[44]通过对内蒙古7个牧业气象试验站1983-2012年的牧草生育期观测资料进行统计分析,发现近30气候暖干化情况下内蒙古草原牧草盖度、产量总体呈降低趋势,20世纪80年代末和90年代变化差异较小,但2000-2012年与20世纪90年代相比下降急剧。郝璐等[45]基于草地资源普查资料发现2000-2003年与1981-1985年相比,大部分地区生物单产及可食牧草产量均明显减少,这与本文结果NPP降低尤其是2000s的结果较为一致。Wu等[46]在对1981-2011内蒙古典型草原植被NPP变化研究时,也得出相似结论。然而,也有些学者认为该区草原净初级NPP主要呈上升趋势[47],这可能是因为研究时段不同所致,后者仅探讨了2001-2010年内蒙古不同植被类型净初级NPP变化。
区域降水可能是1981-2010年内蒙古草地NPP下降的主要影响因素,相对贡献约为78%,但不同草地类型草地NPP变化对温度和降水的敏感性程度存在差异。从草甸草原至典型草原草地NPP对于降水的敏感性升高,荒漠草原介于两者之间,但荒漠草原NPP对于温度的敏感性最高。内蒙古草地主要分布于干旱、半干旱气候区,生长期温度高,降水少,水分亏缺严重,降水是该区植被生长的关键限制因子[39,42,48],草地NPP的时空变化主要受降水控制[47,49]。然而,内蒙古草地跨度较大,水热梯度明显,不同草地类型对降水、温度或水热组合的响应特征差异明显,从草甸草原过渡到典型草原、荒漠草原,生境水分亏缺状况、植物水分利用效率、干旱适应策略等异质性较强[22,50],降水与草地植被生长之间的正相关关系先增强后减弱[51],而随着温度升高,温度诱发水分胁迫增强、降低光合与改变呼吸作用、抑制作物生长[5,21],温度与草地植被生长的关系逐渐趋于负相关且不断加强[30,51]。另一方面,近30年来内蒙古草地区气候变化异质性也较大,从草甸草原至典型草原,荒漠草原降水减少趋势减弱,温度升高趋势加强[30]。生境条件变化特征与草地植被响应策略差异可能是造成本文中草地NPP对气候因子的敏感性分异的原因。
本文结果尚存在一定不确定性：一方面在模拟过程中仅考虑了气候变化和CO2浓度增加的作用,未考虑土地利用/覆被变化、放牧等人为活动对内蒙古草原碳循环的影响。另一方面,内蒙古境内国家基准气象台站较少,境外气象数据无法获取,尽管本文适当选取了其周边其他省份的46气象台站予以补充,但对于面积约120万km2、东西跨度约2400 km的区域来说,这些站点仍显不足。

The authors have declared that no competing interests exist.

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[Meng Shuhong, Yang Sheng, Tian Ying.Present situation, problems and countermeasures of Inner Mongol ia grassland resources and practaculture. Grassland of China, 2004, 26(5): 70-75.]

[14]
Deng X, Huang J, Huang Q, et al.Do roads lead to grassland degradation or restoration? A case study in Inner Mongolia, China. Environment and Development Economics, 2011, 16(6): 751-773.We use satellite remote sensing data of grassland cover in Inner Mongolia, China to test whether the existence of and the size of roads in 1995 is associated with the nature of the grassland in 2000 and/or if it affects the rate of change of the grassland between 1995 and 2000. The regression results show that the impact of roads on grassland cover depends on the nature of the resource. When the grassland is composed of relatively high quality grassland, roads lead to degradation, whereas when grassland resources are sparse, access to a road results in the restoration of the resource.

DOI

[15]
Zhang G, Kang Y, Han G, et al.Effect of climate change over the past half century on the distribution, extent and NPP of ecosystems of Inner Mongolia. Global Change Biology, 2011, 17(1): 377-389.The response of natural vegetation to climate change is of global concern. In this research, changes in the spatial pattern of major terrestrial ecosystems from 1956 to 2006 in Inner Mongolia of China were analyzed with the Holdridge Life Zone (HLZ) model in a GIS environment, and net primary production (NPP) of natural vegetation was evaluated with the Synthetic model, to determine the effect of climate change on the ecosystem. The results showed that climate warming and drying strongly influenced ecosystems. Decreased precipitation and the subsequent increase in temperature and potential evapotranspiration caused a severe deficiency, and hence decreased ecosystem productivity. Climate change also influenced the spatial distribution of HLZs. In particular, new HLZs began to appear, such as Warm temperate desert scrub in 1981 and Warm temperate thorn steppe in 2001. The relative area of desert (Cool temperate desert scrub, Warm temperate thorn steppe, Warm temperate desert scrub, Cool temperate desert and Warm temperate desert) increased by 50.2% over the last half century, whereas the relative area of forest (Boreal moist forest and Cool moist forest) decreased by 36.5%. Furthermore, the area of Cool temperate steppe has continuously decreased at a rate of 5.7% per decade; if the current rate of decrease continues, this HLZ could disappear in 173 years. The HLZs had a large shift range with the mean center of the relative life zones of desert shifting northeast, resulting a decrease in the steppe and forest area and an increase in the desert area. In general, a strong effect of climate change on ecosystems was indicated. Therefore, the important role of climate change must be integrated into rehabilitation strategies of ecosystem of Inner Mongolia.

DOI

[16]
Hu Q, Pan F, Pan X, et al.Spatial analysis of climate change in Inner Mongolia during 1961-2012, China. Applied Geography, 2015, 60: 254-260.In summary, Inner Mongolia has become warmer and drier with increasing temperature and decreasing precipitation during the past several decades.

DOI

[17]
包云, 李晓兵, 李超, 等. 1961-2007年内蒙古气温时空变化特征分析. 干旱区资源与环境, 2010, 24(12): 80-84.利用1961-2007年长时间序列的气温资料,采用线性倾向估计、EOF（经验正交函数） 分析和功率谱分析逐年、逐季地分析了内蒙古气温47年时空变化特征。结果表明：在全球变暖的大背景下,内蒙古气温也以0.45℃/10a的速度升高。东、 中、西部年均温均一致升高,西部平均温度最高,中部次之,东部最低。东、中、西部四季的气温也呈现明显的增温趋势。年气温与四季气温的空间分布具有典型的 一致性,反映了全区气温状况在大尺度的气候系统支配下,冷、暖趋于一致的空间特征。对内蒙古年、季气温EOF分解得到的时间系数进行功率谱分析,提取各模 态时间变化的潜在周期,分析结果反映了内蒙古气温变化以长周期为主要振荡特征。

[Bao Yun, Li Xiaobing, Li Chao, et al.Spatial-temporal distribution characteristics of temperature in Inner Mongolia during 1961-2007. Journal of Arid land Resources and Environment, 2010, 24(12): 80-84.]

[18]
任国玉, 郭军, 徐铭志, 等. 近50年中国地面气候变化基本特征. 气象学报, 2005, 63(6): 942-956.采用国家基准气候站和基本气象站的地面资料，系统地分析了中国大陆地区1951年以来近地表主要气候要素演化的时间和空间特征。结果表明，中国近50 a来年平均地表气温变暖幅度约为1.1 ℃，增温速率接近0.22 ℃/（10 a），比全球或半球同期平均增温速率明显偏高。地表气温增暖主要发生在最近的20余年，其季节和空间特征与前人分析结论基本一致。降水量变化趋势对所取时间段和区域范围敏感。1951年以来全国平均降水量变化趋势不明显，但1956年以来略有增加。降水变化的空间特征明显而相对稳定，东北北部、包括长江中下游的东南部地区和西部广大地区降水增加，而华北地区以及东北东南部和西北东部地区降水明显减少。分析还发现，近50 a来全国平均的日照时数、平均风速、水面蒸发等气候要素均呈显著下降趋势，但积雪地带的最大积雪深度却有所增加。中国日照时间和水面蒸发量变化的空间特征很相似，减少最明显的地区均发生在华北和华东，新疆次之。影响中国年代以上尺度气候变化的因子错综复杂，人类活动引起的大气中温室气体浓度增高可能在一定程度上影响了中国近50 a来的气候，但考虑到尚存的不确定性，目前仍不能给出明确结论。中国东部大部分地区日照时间和水面蒸发量减少可能均起源于人为排放的气溶胶影响，平均风速减弱也有利于水面蒸发量下降，而在西部地区云量和降水量的变化可能更重要。

DOI

[Ren Guoyu, Guo Jun, Xu Mingzhi, et al.Climate changes of china's mainland over the past half century. Acta Meteorologica Sinica, 2005, 63(6): 942-956.]

[19]
张新时, 周广胜, 高琼, 等. 全球变化研究中的中国东北森林_草原陆地样带(NECT). 地学前缘, 1997, 4(1-2): 145-151.陆地生态样带已成球变化研究的重要方法和手段。国际地圈－生物圈计划（ＩＧＢＰ）的陆地样带 －－中国东北森林－－草原陆地样带（ＮＥＣＴ）的提出为中国全球变化研究奠定了基础。该样带在东经１１２－１３０°３０北纬４３°３０设置，长约 １６００ｋｍ，是一条中纬度温带以降水为驱动因素的梯度，具有良好的植被、土壤、土地利用、气候等环境因素的过渡特征。文章介绍了中国东北森林－－草原样 带的确定、手表主在数据库建设、植被

DOI

[Zhang Xinshi, Zhou Guangsheng, Gao Qiong, et al.Northeast china transect for global change studies. Earth Science Frontiers, 1997, 4(1-2): 145-151.]

[20]
胡中民, 樊江文, 钟华平, 等. 中国温带草地地上生产力沿降水梯度的时空变异性. 中国科学D辑: 地球科学, 2006, 36(12): 1154-1162.研究生态系统生产力沿空间降水 梯度的时空变异性是认识生态系统对降水变化的响应特征及适应机理的有效途径．利用内蒙古草原自东向西的天然降水梯度,采用样带研究方法,结合多年实测资 料,系统分析了中国温带草地生态系统地上净初级生产力(ANPP)沿降水梯度的时空变异性．结果表明,沿样带自西南向东北,草地生态系统ANPP显著增 加,荒漠草原、典型草原、草甸草原的ANPP分别为60．86,167．14和288．73g·m-2·a-1；随着年均降水量(MAP)的增 加,ANPP呈指数增加趋势(ANPP=24．47e0.005MAP,R2=0．48)；温度也对ANPP造成了一定的影响,ANPP随温度的升高而降 低．同时考

DOI

[Hu Zhongmin, Fan Jiangwen, Zhong Huaping, et al.The spatial and temporal variability of ANPP in China's temperate grassland along precipitation gradient. Science in China Series D: Earth Sciences, 2006, 36(12): 1154-1162.]

[21]
Gang C, Zhou W, Wang Z, et al.Comparative assessment of grassland npp dynamics in response to climate change in China, North America, Europe and Australia from 1981 to 2010. Journal of Agronomy and Crop Science, 2015, 201(1): 57-68.Abstract Although climate change has been modifying grassland ecosystems for a long time, few studies on grassland ecosystems have focused on large-scale responses to climate change. Hence, grassland net primary productivity (NPP) from 1981 to 2010, as well as its variations in China, North America, Europe and Australia, was assessed and compared using a synthetic model in this study. Subsequently, the correlations between the NPP of each grassland type and climate factors were evaluated to reveal the responses of grassland eco-systems to climate change. The results showed that North America, which has the largest area of grassland ecosystems, exhibits maximum grassland NPP of 4225.30±215.43 Tg DW year 611 , whereas Europe, which has the least area of grassland ecosystems among the four regions, exhibits minimum grassland NPP of 928.95±24.68 Tg DW year 611 . Grassland NPP presented an increasing trend in China and Australia, but decreasing in Europe and North America from 1981 to 2010. In addition, grassland NPP is positively correlated with mean annual precipitation, but demonstrates notable differences with mean annual temperature. In conclusion, climate change has a significant role in explaining the spatiotemporal patterns of and the variations in grassland NPP in the four regions.

DOI

[22]
Wang Z, Zhang Q, Xin X, et al.Response of the annual biomass production of a typical steppe plant community to precipitation fluctuations. The Rangeland Journal, 2014, 36(6): 527-534.The Rangeland Journal publishes papers of scientific merit for a readership of scientists, educators, managers and users. Contributions may be on any aspect of the ecology, use, management or conservation of rangelands, either within Australia or internationally.

DOI

[23]
Chiti T, Papale D, Smith P, et al.Predicting changes in soil organic carbon in mediterranean and alpine forests during the Kyoto Protocol commitment periods using the CENTURY model. Soil Use and Management, 2010, 26(4): 475-484.Abstract Six Italian research sites, representative of Mediterranean and mountain forests and equipped with eddy covariance towers, were used in this study to test the performance of the CENTURY 4.5 model in predicting the dynamics of soil organic carbon (SOC) changes during the commitment periods (CP) of the Kyoto Protocol (2008鈥2012; 2013鈥2017). We show that changes in SOC stocks over short periods of time are difficult to detect, and explore the potential for models to be used for reporting SOC changes for forests that will remain forests, under Article 3.4 of the Kyoto Protocol. As the eddy covariance flux sites have been active for 10yr on average, being initiated over the period between 1996 and 1998, the model was evaluated by comparing the modelled SOC stocks with those directly measured at each site in different years. Since long term series of observed values for soil carbon were not available, the validation of other model outputs such as net primary production (NPP) and soil nitrogen stocks, gives some confidence in long term simulations. Once the model performance was evaluated, two climate change scenarios, A1F1 (world markets-fossil fuel intensive) and B2 (local sustainability), were considered for prediction of C stock changes during the commitment periods of the Kyoto Protocol. In general, despite the need to consider the uncertainties in the direct measurements, at each site model fit with measured SOC stocks was good, with the simulated values within the standard deviation of the measurements. In this regard, the similarity between the SOC measured in 2008 and that predicted for the two forthcoming commitment periods points out the difficulty of detecting carbon stock changes by direct measurements, given the closeness in time to the present of the commitment periods. In any case, all sites show positive variations that are possibly related to the fertilization effects of increasing CO 2 and to longer growing seasons, since no change in management occurred. Compared with the SOC measured in 2008, at the end of the second commitment period, the modelled SOC variations were smaller than 2% in the Mediterranean forests and comprised between 2% and 7% in the mountain forests. These variations, although small, indicate it might be possible to statistically detect differences after 10yr in mountain forests with a reasonable number of samples. In conclusion, this work shows that since SOC stock changes are minimal within both CP, models can be effective tools for estimating future changes in SOC amounts, as an alternative to, or in support of, direct measurements when a short period of time is considered.

DOI

[24]
Lugato E, Berti A.Potential carbon sequestration in a cultivated soil under different climate change scenarios: A modelling approach for evaluating promising management practices in north-east Italy. Agriculture, Ecosystems & Environment, 2008, 128(1-2): 97-103.Crop productivity and soil organic carbon (SOC) turnover are strongly influenced by climatic and environmental conditions, so climate change projections are fundamental for a reliable assessment of C stock variations. Article 3.4 of the Kyoto protocol recognized cropland management as a human-induced strategy to sequester CO 2 in agricultural soil, but only an evaluation of interactions with climate change can help in identifying the promising recommended management practices (RMPs) in the first commitment period and in the long term. In a long-term trial began in 1966, previously simulated with Century SOC model, we selected a specific treatment as ‘business as usual scenario’ (BU). We projected the simulations from 2008 to 2080, hypothesizing different reliable SOC sequestration practices to be compared with BU: farm manure application (FM), reduced tillage (RT) and grassland conversion (GR). For this, we used climate data from four global climate models (CMs: Had3, GCM2, CSIRO2, PCM) forced by four IPCC emission scenarios (SRES). The results clearly indicated that RMPs could affect the C balance in agroecosystems more strongly than climate change. Conversion to grassland was the most promising practice for sequestering C, allowing an average accumulation of 245 and 137702g02C02m 612 at the end of the first commitment period and in 2080, respectively. Manure application (at the rate considered) was anyway a potential C sequestration option that was more effective than reduced tillage in the first commitment period, but slightly less efficient at the end of the simulation. BU was a source of C at 2080 only for the pessimistic climate model Had3, as a consequence of increasing temperature and reduced precipitation, with a depletion of 619402g02C02m 612 in 2080. With the other CMs, the BU always resulted in a carbon sink. Despite inherent sources of variability we discussed, simulation results demonstrated that RMPs could contribute towards achieving the Kyoto targets in northern Italy.

DOI

[25]
袁飞, 韩兴国, 葛剑平, 等. 内蒙古锡林河流域羊草草原净初级生产力及其对全球气候变化的响应. 应用生态学报, 2008, 19(10): 2168-2176.利用CENTURY模型对内蒙古锡林河流域羊草草原在未来气候变化以及大气CO<SUB>2</SUB>浓度增高条件下的年地上净初级生产力(annual aboveground net primary productivity，ANPP)动态进行了模拟研究.结果表明：CENTURY模型可以较好地预测ANPP的变化.进一步的情景模拟发现，虽然全球气候变化所引起的温度和降水改变、以及大气CO<SUB>2</SUB>浓度升高都会影响ANPP，但降水是关键的影响因子.多个全球气候模型(GCM) 预测该地区未来降水量会减少，故可能导致其ANPP降低，但在以下气候变化情景下研究区ANPP可能会升高：1)CO<SUB>2</SUB>浓度倍增，温度升高2 ℃，降水保持不变或增加10%～20%；2)CO<SUB>2</SUB>浓度保持不变，温度升高2 ℃，降水增加20%.气候变化将对内蒙古锡林河流域羊草草原产生显著影响.

[Yuan fei, Han Xingguo, Ge Jianping, et al. Net primary productivity of Leymus chinensis steppe in Xilin River basin of Inner Mongolia and its responses to global climate change. Chinese Journal of Applied Ecology 2008, 19(10): 2168-2176.]

[26]
莫志鸿, 李玉娥, 高清竹. 主要草原生态系统生产力对气候变化响应的模拟. 中国农业气象, 2012, 33(4): 545-554.利用历史气候数据（1961-2010年）和气候情景数据（1961-2100年）驱动CENTURY模型模拟高寒草甸、温性草甸草原、温性草原和温性荒漠4类主要草原生态系统的地上净初级生产力(ANPP)，分析考虑和不考虑大气CO2 浓度增加的直接效益（以下简称“CO2增益”）未来气温和降水量变化对ANPP的影响。结果表明：（1）1961-2010年，高寒草甸的ANPP呈极显著增加趋势（P＜0.01），与生长季内最低气温上升密切相关；温性草甸草原、温性草原和温性荒漠的ANPP变化趋势不显著，但年际波动较大，均与同期降水量具有极显著的正相关（P＜0.01），而与同期气温的相关性较弱。（2）若不考虑大气CO2增益，在A2和B2情景下2020s(2011-2040年)、2050s(2041-2070年)、2080s(2071-2100年)时段该4类草原生态系统的ANPP相对于基准时段(1961-1990年)的平均增幅分别为4.9%、12.0%、18.6%和3.0%、6.6%、8.9%，其中温性草原的ANPP增幅最大，其次是温性荒漠，而温性草甸草原和高寒草甸的ANPP有增有减，变幅较小。（3）若考虑大气CO2增益，在A2和B2情景下2020s、2050s、2080s时段该4类草原生态系统的ANPP较不考虑大气CO2增益均有显著增加（P＜0.05），平均增幅分别为20.0%、31.8%、45.6%和9.0%、13.7%、18.0%，其中温性草原的ANPP增幅最大，其次是高寒草甸和温性荒漠，而温性草甸草原的ANPP增幅稍小。

DOI

[Mo Zhihong, Li Yue,Gao Qingzhu.Simulation on productivity of main grassland ecosystems responding to climate change. Chinese Journal of Agrometeorology, 2012, 33(4): 545-554.]

[27]
王明玖, 张存厚. 内蒙古草地气候变化及对畜牧业的影响分析. 内蒙古草业, 2013, 25(1): 5-12.在介绍了内蒙古草地自然环境特点及重点草原区分布的基础上，讨论了气候变化的现状、特点及对内蒙古草地的影响。利用Century模型，模拟预测了草地气候变化的未来趋势，提出了适应和应对气候变化的宏观对策和具体措施。内蒙古草地具有先天的环境和生态脆弱性，气候变化集中体现在整体暖干化、增温强度大、时空变化多元、复杂和极端气候事件增多4个方面，使脆弱性加强，畜牧业经营的风险加大。气候变化的影响有正、负两方面的特征，主要体现在对草地地上净初级生产力的影响和对气象灾害的影响方面。总体表现为多数草地区草地地上净初级生产力提高，但气象灾害的危害程度和范围加大，增加了生物灾害的可能性。为此，在宏观方面建议，首先应加强对气候变化的科学研究，进一步掌握气候变化及其影响规律；其次是加强信息网络平台建设，提供及时准确的气候变化信息服务；第三是政府部门应加强抗灾能力建设，变被动抗灾为主动预防；第四是根据预测的未来草地生产力变化趋势，及时调整畜牧业产业布局，优化产业结构。提出的具体对策建议包括：加快全面建立和完善牧区饲草料储备制度和市场、流通制度的步伐；鼓励探索体制、机制创新；在逐步减轻草地放牧压力的情况下，促进草地自身生态好转；在沙地草地植被恢复重建中，应以草、灌植物为主．力Ⅱ强人工、半人工和改良草地建设及健全和完善草原防灾减灾体系。

DOI

[Wang Mingjiu, Zhang Cunhou.Climate change in Inner Mongolia grassland and the effects on pastural animal husbandry. Inner Mongolia Prataculture, 2013, 25(1): 5-12.]

[28]
Ojima D S, Parton W J, Schimel D S, et al.Modeling the effects of climatic and CO2 changes on grassland storage of soil C. Water Air & Soil Pollution, 1993, 70(1): 643-657.

[29]
Xu W, Chen X, Luo G, et al.Using the CENTURY model to assess the impact of land reclamation and management practices in oasis agriculture on the dynamics of soil organic carbon in the arid region of North-western China. Ecological Complexity, 2011, 8(1): 30-37.<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="spar0005">Large-scale reclamation of arid land in North-western China over the past 50 years has converted the natural desert landscape into anthropogenic oasis, particularly in the lower part of watersheds. Drastic human activities may have caused the change of soil organic carbon (SOC) in anthropogenic oasis. This study employs the CENTURY model (Version 4.0) to investigate the effects of land reclamation and management practices in oasis agriculture on the dynamic of SOC at the lower part of Sangong river watershed, a typical anthropogenic oasis reclaimed at 50 years ago. Based on field investigation, history of crop rotations, and past farm practices in study area, land management practices were divided into five categories, corresponding five periods, 0&ndash;1958, 1959&ndash;1984, 1985&ndash;1992, 1993&ndash;1998 and 1999&ndash;2008. The model successfully simulated the SOC dynamics of the top layer soil (0&ndash;20&#xA0;cm) in the different periods. The state of equilibrium of total SOC and the active, slow, and passive carbon pools were built by CENTURY model in 0&ndash;1959. Over the 50 years&rsquo; cultivation (1959&ndash;2008), the mean change in total SOC exhibited complex ways. SOC increased rapidly in the first 2 years (1959&ndash;1960) after shrubland reclamation, and declined slowly during the period 1961&ndash;1984 and then decreased rapidly from 1985 to 1992. Between 1993 and 1998, it remained relatively stable, and climbed rapidly again during 1999&ndash;2008. The trend in total SOC showed &ldquo;N&rdquo; shape, i.e., increase, decrease, then increase. Finally, total SOC is greater (8.2%) in 2008 than the original level of SOC under the natural desert shrub. The improvements of land management practices such as ploughing being replaced with no tillage, straw being crushed before returning it to soil, and reasonable application of fertilizers, played a key role in the change in total SOC. Especially, soil carbon sequestration was obviously increased since protective management practices were implemented in 1993, such as no tillage, straw returning to soil, and the balanced fertilization technique. The results were different from the conclusions that loss of soil organic carbon would happen due to reclamation and continuous farming in tropical forests, semiarid grasslands of northern China and Nigerian semiarid Savannah.</p>

DOI

[30]
Guo L, Wu S, Zhao D, et al.NDVI-based vegetation change in Inner Mongolia from 1982 to 2006 and its relationship to climate at the biome scale. Advances in Meteorology, 2014, 66(1): 79-92.中国科学院机构知识库(中国科学院机构知识库网格（CAS IR GRID）)以发展机构知识能力和知识管理能力为目标，快速实现对本机构知识资产的收集、长期保存、合理传播利用，积极建设对知识内容进行捕获、转化、传播、利用和审计的能力，逐步建设包括知识内容分析、关系分析和能力审计在内的知识服务能力，开展综合知识管理。

DOI

[31]
Cramer W, Bondeau A, Woodward F I, et al.Global response of terrestrial ecosystem structure and function to CO2 and climate change: Results from six dynamic global vegetation models. Global Change Biology, 2001, 7(4): 357-373.

[32]
Lucht W, Prentice I C, Myneni R B, et al.Climatic control of the high-latitude vegetation greening trend and pinatubo effect. Science, 2002, 296(5573): 1687-1689.A biogeochemical model of vegetation using observed climate data predicts the high northern latitude greening trend over the past two decades observed by satellites and a marked setback in this trend after the Mount Pinatubo volcano eruption in 1991. The observed trend toward earlier spring budburst and increased maximum leaf area is produced by the model as a consequence of biogeochemical vegetation responses mainly to changes in temperature. The post-Pinatubo decline in vegetation in 1992-1993 is apparent as the effect of temporary cooling caused by the eruption. High-latitude uptake during these years is predicted as a consequence of the differential response of heterotrophic respiration and net primary production.

DOI PMID

[33]
Piao S, Tan K, Nan H, et al. Impacts of climate and CO2 changes on the vegetation growth and carbon balance of Qinghai-Tibetan grasslands over the past five decades. Global and Planetary Change, 2012, 98-99: 73-80.

[34]
Piao S, Friedlingstein P, Ciais P, et al.Changes in climate and land use have a larger direct impact than rising CO2 on global river runoff trends. Proceedings of the National Academy of Sciences, 2007, 104(39): 15242-15247.The significant worldwide increase in observed river runoff has been tentatively attributed to the stomatal “antitranspirant” response of plants to rising atmospheric CO 2 [Gedney N, Cox PM, Betts RA, Boucher O, Huntingford C, Stott PA (2006) Nature 439: 835–838]. However, CO 2 also is a plant fertilizer. When allowing for the increase in foliage area that results from increasing atmospheric CO 2 levels in a global vegetation model, we find a decrease in global runoff from 1901 to 1999. This finding highlights the importance of vegetation structure feedback on the water balance of the land surface. Therefore, the elevated atmospheric CO 2 concentration does not explain the estimated increase in global runoff over the last century. In contrast, we find that changes in mean climate, as well as its variability, do contribute to the global runoff increase. Using historic land-use data, we show that land-use change plays an additional important role in controlling regional runoff values, particularly in the tropics. Land-use change has been strongest in tropical regions, and its contribution is substantially larger than that of climate change. On average, land-use change has increased global runoff by 0.08 mm/year 2 and accounts for ≈50% of the reconstructed global runoff trend over the last century. Therefore, we emphasize the importance of land-cover change in forecasting future freshwater availability and climate.

DOI PMID

[35]
马文红, 方精云, 杨元合, 等. 中国北方草地生物量动态及其与气候因子的关系. 中国科学 C 辑: 生命科学, 2010, 40(7): 632-641.草地生态系统在全球碳循环中扮演重要角色.中国草地约占中国陆地面积的1/3,但对其碳库大小、动态及其与气候变化的关系缺乏系统研究.基于341个样地调查的地上、地下生物量资料和1982~2006年的卫星遥感数据,利用地上生物量与遥感数据之间及地上生物量与地下生物量之间的关系,估算了中国北方草地生物量碳库及其空间分布,分析了过去25年生物量碳密度和碳库的时间动态及其与气候变化的关系.结果显示:(1)中国北方草地生物量碳库为557.5TgC,地上、地下生物量密度分别为39.5和244.6gC/m2,地下部分占总生物量碳库的86%;(2)1982~2006年间中国草地生物量碳库呈微弱增加趋势,平均年增量为0.2TgC,但自20世纪80年代末,草地生物量并未呈现显著的变化趋势;(3)草地生物量的年际波动主要受1~7月降水的影响,而与温度关系较弱.不同草地类型之间生物量-气候关系存在一定差异,较为干旱的荒漠草原和典型草原的生物量波动与降水关系密切;高寒草甸的生物量则与1~7月均温显著正相关,而与降水的关系较弱.结果表明,不同草地生态系统对未来气候变化的响应可能存在差异.

DOI

[Ma Wenhong, Fang Jingyun, Yang Yuanhe, et al.Grassland biomass dynamics and its relationship with climate factors over the North China. Science in China Series D: Scientia Sinica Vitae, 2010, 40(7): 632-641.]

[36]
陶波, 李克让, 邵雪梅, 等. 中国陆地净初级生产力时空特征模拟. 地理学报, 2003, 58(3): 372-380.<p>应用生态系统机理性模型估算1981～1998年中国陆地生态系统净初级生产力 (NPP) 的时空变化，并分析了NPP对年际间气候变化的响应。结果表明，中国陆地生态系统1981～1998年NPP总量波动于2.86～3.37 Gt C/yr之间，平均约为3.09 Gt C /yr ，单位NPP平均约为342 g C m<sup>2</sup>/yr。在研究时段内，NPP有缓慢增长趋势，年增长率约为0.32%，NPP总量平均值从 1980年代 (1981～1989年) 的3.03 Gt C/yr上升到1990年代 (1990～1998年) 的3.14 Gt C/yr。在一些厄尔尼诺 (El Nino) 发生年，NPP有明显的下降，但由于地域差异和季风环流的影响，NPP同ENSO的关系还十分复杂。从全国来看，在厄尔尼诺现象发生的1982年、1986年、1991年和1997年，NPP都有一定程度的减少。但在1993年和1994年两个厄尔尼诺发生年，NPP并没有表现为明显的下降趋势，1994年NPP总量甚至比上一年增加了0.12Gt，这主要是由于温度和降水量在不同地区的分布差异以及不同地区对厄尔尼诺现象的响应差异造成的。</p>

DOI

[Tao Bo, Li Kerang, Shao Xuemei, et al.temporal and spatial pattern of net primary production of terrestrial ecosystems in China. Acta Geographica Sinica, 2003, 58(03): 372-380.]

[37]
潘耀忠, 史培军, 朱文泉, 等. 中国陆地生态系统生态资产遥感定量测量. 中国科学 D辑: 地球科学, 2004, 34(4): 375-384.生态系统的自然价值及其服务功能效益是地球生命支持系统的重要组 成部分,也是社会与环境可持续发展的基本要素.生态资产是生态系统生物资源直接价值及其生态服务功能价值的总和.对生态资产价值进行定量估算不仅可以从经 济学的角度对生态环境进行定量评价,而且能够引起全社会对生态环境建设的高度重视,同时也是最终将其纳入社会与市场经济体系、建立绿色GDP核算体系、制 定生态环境建设补偿政策的必要前提.本文在传统生态学生态资产单位面积价值研究的基础上提出了基于遥感定量测量的生态资产价值评估模型,并利用 NOAA/AVHRR和其他辅助数据对模型所需要的参数,如:陆地生态系统地表覆盖类型、植被覆盖度(f)、植被第一性净生产力(NPP)进行了定量测 量,并参考Costanza等人的经济参数,对中国陆地生态系统生态资产价值进行了全覆盖的定量测量,并据此绘制了中国陆地生态系统生态资产价值空间分布 图.结果表明:中国陆地生态系统每年的生态资产总价值为64441.77亿元人民币;较之传统的生态学静态计算方法,遥感测量克服了以点代面的缺点,测量 结果可以更加客观地反映中国陆地系统生态资产及其空间分布的现实情况,为今后开展相关研究奠定了良好的基础.

DOI

[Pan Yaozhong, Shi Peijun, Zhu Wenquan, et al.Chinese land ecosystem assets' remote sensing quantitative measurement. Science in China Series D: Earth Sciences, 2004, 34(4): 375-384.]

[38]
朱文泉, 潘耀忠, 张锦水. 中国陆地植被净初级生产力遥感估算. 植物生态学报, 2007, 31(3): 413-424.该文在综合分析已有光能利用率模型的基础上，构建了一个净初级生产力(<EM>NPP</EM>)遥感估算模型，该模型体现了3方面的特色：1)将植被覆盖分类引入模型，并考虑植被覆盖分类精度对 <EM>NPP</EM> 估算的影响，由它们共同决定不同植被覆盖类型的归一化植被指数(<EM>NDVI</EM>)最大值；2)根据误差最小的原则，利用中国的<EM>NPP</EM>实测数据，模拟出各植被类型的最大光能利用率，使之更符合中国的实际情况；3)根据区域蒸散模型来模拟水分胁迫因子，与土壤水分子模型相比，这在一定程度上对有关参数实行了简化，使其实际的可操作性得到加强。模拟结果表明，1989～1993年中国陆地植被<EM>NPP</EM>平均值为3.12 Pg C (1 Pg=10<SUP>15</SUP> g)，<EM>NPP</EM>模拟值与观测值比较接近，690个实测点的平均相对误差为4.5%；进一步与其它模型模拟结果以及前人研究结果的比较表明，该文所构建的<EM>NPP</EM>遥感估算模型具有一定的可靠性，说明在区域及全球尺度上，利用地 理信息系统技术将遥感数据和各种观测数据集成在一起，并对<EM>NPP</EM>模型进行参数校正， 基本上可以实现全球范围不同生态系统<EM>NPP</EM>的动态监测。

[Zhu Wenquan, Pan Yaozhong, Zhang Junshui.Estimation of net primary productivity of Chinese terrestrial vegetation based on remote sensing. Journal of Plant Ecology, 2007, 31(3): 413-424.]

[39]
李刚, 周磊, 王道龙, 等. 内蒙古草地NPP变化及其对气候的响应. 生态环境, 2008, 17(5): 1948-1955.植被净初级生产力(Net Primary Productivity,NPP)是衡量植物群落在自然环境条件下生产能力的重要指标,NPP的变化直接反映了生态系统对环境气候条件的响应,因此可以 作为生态系统功能对气候变化响应的研究指标.本文利用卫星遥感资料和地面气象观测资料,利用光能利用率模型估算了内蒙古地区1982-2003年4-10 月草地NPP,并计算了与NPP密切相关的几个气候因子,分析了1982-2003年内蒙古地区草地NPP年际性变化规律、气候因子的年际变化规律,以及 草地NPP对主要气候因子的响应关系.结果表明:1982-2003年内蒙古草地生长季的NPP呈波动中增加趋势,NPP的年平均递增率为C0.0036 g·m-2·Gr-1;草地NPP的空间分布与生物温度(BT)及可能蒸散率(PER)呈显著负相关,与降雨量(RAIN)、湿润度(K)及实际蒸散 (AE)呈极显著正相关.内蒙古地区,草地NPP受降雨量(RAIN)及生物温度(BT)的影响较大.但NPP的变化受RAIN的影响更为明显;内蒙古地 区不同草地类型的NPP变化对气候因子的响应略有不同.

DOI

[Li Gang, Zhou Lei, Wang Daolong, et al.Variation of net primary productivity of grassland and its response to climate in Inner Mongolia. Ecology and Environment, 2008, 17(5): 1948-1955.]

[40]
孙睿, 朱启疆. 中国陆地植被净第一性生产力及季节变化研究. 地理学报, 2000, 55(1): 36-45.利用植被指数与植被吸收的光合有效辐射比例之间的线性关系,由 1992年4月～1993年3月12 个月的1 km AVHRR NDVI资料及同期地面气象资料确定地表植被吸收的光合有效辐射,然后由光能利用率得到植被净第一性生产力(NPP).为了更准确计算NPP,本文还考虑 了温度及土壤水分条件对光能利用率的影响,最后得到我国陆地植被年NPP分布图,并对中国陆地植被净第一性生产力分布情况的季节变化及不同植被类型的 NPP季节变化进行了初步研究.结果表明,我国NPP的分布主要受水分条件的影响,呈从东南到西北递减的趋势,全国年总净第一性生产力约为 2.645×109tC.

DOI

[Sun Rui, Zhu Qijiang.Distribution and seasonal change of net primary productivity in China from April , 1992 to March, 1993. Acta Geographica Sinica, 2000, 55(1): 36-45.]

[41]
朴世龙, 方精云, 郭庆华. 利用CASA模型估算我国植被净第一性生产力. 植物生态学报, 2001, 25(5): 603-608.

DOI

[Piao Shilong, Fang Jingyun, Guo Qinghua.Application of CASA model to the estimation of Chinese terrestrial net primary productivity. Journal of Plant Ecology, 2001, 25(5): 603-608.]

[42]
王国成, 张稳, 黄耀. 1981-2001年内蒙古草地净初级生产力时空变化特征. 草业科学, 2011, 28(11): 2016-2025.<p>利用遥感和气象数据，采用CASA(CarnegieAmesStanford Approach)模型和统计分析方法，研究了1981-2001年内蒙古自治区草地7-8月植被净初级生产力(net primary productivity, NPP)的时空变化特征，并分析了气候因素和放牧强度对NPP的影响。结果表明，1）1981-2001年，内蒙古草地NPP显著减少、显著增加和变化不明显的面积分别占1%、30%和69%；NPP显著增加的区域位于内蒙古东北、东南和南部，NPP显著减少的区域零星分布于该区中部荒漠草原和典型草原分界处。总体而言，该区NPP增加不甚明显， 21年7-8月草地NPP（均以C变化计）平均值为192.0 g/m2，年际变化范围为150.5～255.5 g/m2。2）7-8月降水是该区NPP年际变化的主要驱动因子，降水量高的年份NPP亦高。NPP与气候因素间的关系表现为NPP随降水增多而升高，随温度升高而下降，辐射对NPP的影响不明显。3）综合考虑气候因素与人类活动对草地NPP的影响发现，21年间，土默特左旗和土默特右旗境内放牧强度增加导致NPP显著下降。</p>

[Wang Guocheng, Zhang Wen, Huang Yao.Spatial and temporal variation of net primary productivity in Inner Mongolian grassland from 1981 to 2001. Prataculture Science, 2011, 28(11): 2016-2025.]

[43]
陈四清. 基于遥感和GIS的内蒙古锡林河流域土地利用/土地覆盖变化和碳循环研究. 北京: 中国科学院研究生院博士学位论文, 2002.该文运用遥感、GIS技术和生态模型方法,以内蒙古锡林河流域草 原生态系统为例,研究中国北方干旱/半干旱草原地区土地利用/土地覆盖变化和碳循环问题.文章首先对内蒙古锡林河流域四个时期的Landsat TM/ETM+影像进行土地利用/土地覆盖分类、成图;通过对比,分析了锡林河流域近20年的来的土地利用/土地覆盖变化;并进一步运用GIS方法研究了 锡林河流域草地退化的演化路径;最后运用CENTURY模型模拟了内蒙古锡林河流域大针茅草原、羊草草原的碳循环过程,绘制了其碳循环模式图;并进一步分 析了锡林河流域典型草原生态系统对大气碳库的源/汇功能.

[Chen Siqing.Study on land-use/cover change and carbon cycle of Xilin River Basin, Inner Mongolia based on remote sensing and GIS. Beijing: Doctoral Dissertation of Graduate School of Chinese Academy of Sciences, 2002.]

[44]
李兴华, 刘秀荣, 曹艳芳. 气候变化对内蒙古草地牧草长势影响研究. 见: 南京信息工程大学. 第30届中国气象学会年会论文集. 南京: 南京信息工程大学, 2013.通过对内蒙古草原区81个气象站1971～2010年的气象资料和7个牧业气象试验站1983～2012年牧草资料的统计分析,得出近40年内蒙古草原区年平均气温呈直线上升趋势,增温率为0.34℃·(10a)-1;年降水量存在5～7年的周期性,20世纪70年代到90年代降水呈波动略增加趋势,2000年以后降水明显减少;多年平均风速呈减小趋势,风速减小率为(0.24m·s-1)·(10a)-1;气候经历了冷湿-冷干-暖湿-暖干期。气候变暖使内蒙古牧草在降水正常年份,返青期提前5～15天,黄枯期推后5～18天,青草期延长10～30天;降水的减少,干旱的频发又使部分年份牧草的生长季明显缩短,部分地区牧草在春季出现二次返青现象。气候暖干化使近12年内蒙古草甸草原、典型草原和荒漠化草原分别比20世纪90年代的牧草平均高度降低了2.4cm、9.3cm和9.8cm;牧草平均盖度降低了11%、13%和4%;干草平均产量减产1019.8Kg/hm2、671.4Kg/hm2和372.5Kg/hm2。

[Li Xinghua, Liu Xiurong, Cao Yanfang.Research in the climatic change influencing pasture growth in Inner Mongolia grassland. In: Nanjing University of Information Science & Technology. The 32th Chinese Meteorological Society. Nanjing: Nanjing University of Information Science & Technology, 2013.]

[45]
郝璐, 吴向东. 内蒙古草地生产力时空变化及驱动因素分析. 干旱区研究, 2006, 33(4): 577-582.基于草地资源普查资料和GIS 技术,以生物量与可食牧草比例作为影响草地生产力的主要因子,以县域为单位,对内蒙古草地生产力的时空变化特征及其分布的地域差异性进行了分析。结果表 明:2000-2003年与1981-1985年相比,大部分地区生物单产及可食牧草产量均明显减少,可食牧草比例也明显降低;生物单产、可食牧草产量以 及可食牧草比例高值区与次高值区均明显减少;大部分地区草量变化与草质变化具有时空一致性。最后从气候变化、草畜矛盾、现有草原管理制度及建设状况方面, 对内蒙古草地生产力变化成因进行了分析。

[Hao Lu, Wu Xiangdong.Analysis on the Spatio-temporal change of steppe productivity and its driving factors in Inner Mongolia. Arid Zone Research, 2006, 33(4): 577-582.]

[46]
Wu X, Li P, Jiang C, et al.Climate changes during the past 31 years and their contribution to the changes in the productivity of rangeland vegetation in the Inner Mongolian typical steppe. The Rangeland Journal, 2014, 36(6): 519-526.The Rangeland Journal publishes papers of scientific merit for a readership of scientists, educators, managers and users. Contributions may be on any aspect of the ecology, use, management or conservation of rangelands, either within Australia or internationally.

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[47]
穆少杰, 李建龙, 杨红飞, 等. 内蒙古草地生态系统近10年NPP时空变化及其与气候的关系. 草业学报, 2013, 22(3): 6-15.<p>植被净初级生产力（ｎｅｔｐｒｉｍａｒｙｐｒｏｄｕｃｔｉｖｉｔｙ，ＮＰＰ）及其对气候变化的响应研究是全球变化的核心内容之一。通过改进的光能利用率模型（ＣＡＳＡ 模型），利用ＭＯＤＩＳＮＤＶＩ数据、土地覆盖分类数据、气象数据等，逐像元模拟２００１－２０１０年内蒙古草地生态系统ＮＰＰ的时空变化，分析其对气候因子变化的响应关系。结果表明，１）２００１－２０１０年内蒙古草地多年平均ＮＰＰ为２８１．３ｇＣ／（ｍ<sup>２</sup>&middot;ａ），空间分布呈由西南向东北递增的趋势，草甸草原、典型草原和荒漠草原平均ＮＰＰ分别为４３１．８，２８８．７和１２３．５ｇＣ／（ｍ<sup>２</sup>&middot;ａ）；２）２００１－２０１０年间内蒙古草地ＮＰＰ 总体上呈上升趋势。ＮＰＰ上升趋势最明显的草地主要分布在毛乌素沙地、浑善达克沙地、科尔沁沙地、呼伦贝尔盟和大兴安岭南麓地区，而下降趋势最明显的草地主要分布在阴山山脉和锡林郭勒盟中部的典型草原区；３）总体而言，降水量是内蒙古草地净初级生产力的主要影响因素。草甸草原ＮＰＰ与降水量、温度的关系均很密切，而且与温度的相关性更强；典型草原和荒漠草原ＮＰＰ则主要受降水量控制，其中荒漠草原ＮＰＰ与降水量的关系更密切。</p>

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[Mu Shaojie, Li Jianlong, Yang Hongfei, et al.Spatio-temporal variation analysis of grassland net primary productivity and its relationship with climate over the past 10 years in Inner Mongolia. Acta Prataculturae Sinica, 2013, 22(3): 6-15.]

[48]
龙慧灵, 李晓兵, 王宏, 等. 内蒙古草原区植被净初级生产力及其与气候的关系. 生态学报, 2010, 30(5): 1367-1378.利用NOAA/AVHRR GIMMS NDVI数据、土地覆盖分类数据、气象数据等，基于改进的基于光能利用率的净初级生产力（Net Primary productivity，NPP）遥感估算模型对内蒙古草原区1982-2006年的NPP进行估算，并分别以年、季节和月为时间单位，计算基于像元的NPP与降水、温度之间的相关及偏相关系数，分析不同时间单位及尺度上NPP与气候的关系。结果表明，1982-2006年内蒙古草原区NPP总量呈波动增加的趋势，平均增加值为0.861Mt C/a。以年为时间单位，内蒙古草原区年NPP与降水的关系比较明显。以季节为时间单位，年际春季和夏季NPP与降水的关系比较明显，秋季二者关系相对较弱，春季和秋季NPP与温度的相关系数和偏相关系数空间格局比较一致，且相关性明显高于夏季。以月为时间单位的相关水平明显高于年际水平，多年平均年内月NPP与降水、温度的相关程度明显增强，除去降水的影响，月均温对NPP的影响明显下降，且空间格局也有明显的变化，说明以月为时间单位在年内尺度上降水对植被生长的影响比温度要大。而以4、7、10月份为例，在年际尺度上，虽然各月份NPP均受降水的影响较大，但与降水关系最为密切的是4月份和10月份NPP，与之相比，7月份NPP与温度的关系明显高于其他两月。

[Long Huiling, Li Xiaobing, Wang Hong, et al.Net primary productivity of grassland ecosystem and its relationship with climate in Inner Mongolia. Acta Ecologica Sinica, 2010, 30(5): 1367-1378.]

[49]
Tian H, Cao C, Chen W, et al.Response of vegetation activity dynamic to climatic change and ecological restoration programs in Inner Mongolia from 2000 to 2012. Ecological Engineering, 2015, 82: 276-289.To address devastating land desertification and soil erosion and to improve human well-being, central government in China has implemented a number of ecological restoration programs. It is essential to rigorously monitor the dynamic of vegetation activity and evaluate the effectiveness of these programs, not only to provide scientific support for ecosystem monitoring in arid and semi-arid region, but also to assess the efficiency of ecological restoration policy. Taking Inner Mongolia as study area, we used 13 years (2000-2012) of both climatic data and MODIS NDVI data to (1) assess the spatiotemporal vegetation dynamic and map areas of significant vegetation restoration and degradation, (2) analyze the impacts of climatic changes on vegetation activity and map areas where vegetation activity dynamic was significantly affected by climatic change, (3) map main driving forces of significant vegetation restoration or degradation, (4) validate the zones where vegetation significant restoration were mainly impacted by ecological restoration programs with vegetation fractional cover data in 2000 and 2012. Results showed an overall greening (15.38% significant NDVI increasing) and partial degradation (1.64% significant NDVI decreasing) in Inner Mongolia. It was estimated that annual precipitation most strongly and significantly limited vegetation growth over 45.1% of Inner Mongolia, whereas sunlit hours significantly limited growth over 3.37% and air temperature significantly over 0.73% of Inner Mongolia. Among the 15.38% significant greening region, 5.86% was caused by climatic changes, 5.67% was caused by ecological restoration programs, and the other 3.8% was caused by multi-factors. Among the 1.64% significant degradation region, 0.17% was caused by climatic changes and other 1.47% can be explained by human activities, such as population growth and city expansion.

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[50]
Bhandari J, Pan X, Bijaya G C D. Spatial and seasonal variation in rain use efficiency in semiarid grasslands of Inner Mongolia. Advances in Meteorology, 2015, (2015): 1-7.Rain use efficiency (RUE) is an important indicator for identifying the response of plant production to variation in precipitation patterns, especially in semiarid ecosystem grasslands of Inner Mongolia. We have investigated the response and spatial patterns of RUE to precipitation patterns based on five years (2006, 2007, 2008, 2012, and 2013) of records from semiarid ecosystem sites across Inner Mongolia. Our results showed that RUEADM was lowest in the wettest year (2012) and highest in the year following the driest year (2008). There was no significant correlation between RUEADM and RUETDM in typical and desert steppe. RUETDM was strongly correlated with both annual precipitation (AP) and growing season precipitation (GSP) compared to RUEADM. RUEADM, therefore, cannot be used in place of RUETDM. RUEADM increased with species richness. The relationship between RUEADM and species richness was significantly correlated in meadow steppe, typical steppe, and desert steppe. Our findings can shed light on the spatial utilization pattern of seasonal rainfall in semiarid grassland ecosystems.

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[51]
Piao S L, Mohammat A, Fang J Y, et al.NDVI-based increase in growth of temperate grasslands and its responses to climate changes in China. Global Environmental Change, 2006, 16(4): 340-348.This study analyzes the temporal change of Normalized Difference Vegetation Index (NDVI) for temperate grasslands in China and its correlation with climatic variables over the period of 1982–1999. Average NDVI of the study area increased at rates of 0.5%02yr 611 for the growing season (April–October), 0.61%02yr 611 for spring (April and May), 0.49%02yr 611 for summer (June–August), and 0.6%02yr 611 for autumn (September and October) over the study period. The humped-shape pattern between coefficient of correlation ( R ) of the growing season NDVI to precipitation and growing season precipitation documents various responses of grassland growth to changing precipitation, while the decreased R values of NDVI to temperature with increase of temperature implies that increased temperature declines sensitivity of plant growth to changing temperature. The results also suggest that the NDVI trends induced by climate changes varied between different vegetation types and seasons.

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