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GEOGRAPHICAL RESEARCH >

2018 , Vol. 37 >Issue 11: 2206 - 2217

DOI: https://doi.org/10.11821/dlyj201811007

Articles

Spatial-temporal change of soil organic carbon density and storage in Anhui province from 1980 to 2010

  • ZHAO Mingsong , 1, 2 ,
  • LI Decheng , 2 ,
  • ZHANG Ganlin 2 ,
  • WANG Shihang 1
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  • 1. School of Geodesy and Geomatics, Anhui University of Science and Technology, Huainan 232001, Anhui, China
  • 2. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, CAS, Nanjing 210008, China

Received date: 2018-04-27

  Request revised date: 2018-07-09

  Online published: 2018-11-20

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《地理研究》编辑部
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Abstract

In this paper, Anhui province was selected as a subject for a case study. A comparative study was conducted based on the data of the Second National Soil Survey and the data collected during 2010 and 2011. The study, applying GIS spatial analysis, focuses on the spatial-temporal change of soil organic carbon (SOC) density and storage in the surface layer (0-20 cm) and 0-100 cm layer of the study area during the period (1980-2010). Furthermore, this research explored the impact of land use change on SOC density and storage. The results are as follows: (1) From 1980 to 2010, the mean SOC density decreased by 0.37 kg/m2 in the surface layer, and by 1.63 kg/m2 in the 0-100 cm layer in the whole province. SOC density in the cultivated land increased, yet it decreased in the non-cultivated land. (2) The map of SOC density change showed that SOC density increased in the north and decreased in the south. The increment rate decreased from north to south within the province. The area with SOC density increment was slightly more than the area where SOC density decreased. (3) From 1980 to 2010, SOC storage decreased by 34.23×109 kg and 197.26×109 kg in the surface layer and 0-100 cm layer, respectively. SOC storage increased in Huaibei plain, Jianghuai hilly land and Yangtze plain, and decreased in western and southern hilly mountains. (4) SOC density and storage reduction is relatively slow in the context of non-cultivated land changing to cultivated land, rather than in the remaining original land functions or transferring to other non-cultivated functions. The internal transfer of cultivated land functions, i.e., changing to paddy field or upland, will result in more increment in SOC density and storage than the land with the remaining functions. The research will provide support in decision making related to regional soil carbon sequestration potential and soil fertility changes.

Key words： soil organic carbon; spatial-temporal change; GIS; Anhui province

Cite this article

ZHAO Mingsong , LI Decheng , ZHANG Ganlin , WANG Shihang . Spatial-temporal change of soil organic carbon density and storage in Anhui province from 1980 to 2010[J]. GEOGRAPHICAL RESEARCH, 2018 , 37(11) : 2206 -2217 . DOI: 10.11821/dlyj201811007

1 引言

土壤有机碳（SOC）是全球碳循环过程中非常重要的碳库[1],也是全球气候变化模拟中重要的输入参数。全球SOC总储量约是植被系统中碳储量的3倍,是大气中碳储量的2倍[2,3,4]。此外,SOC也是土壤肥力和耕地质量的重要指标之一。揭示区域SOC及储量的变化规律是研究区域土壤固碳潜力和土壤质量管理的关键。如Zhang等[5]利用地统计方法研究了爱尔兰东南部草地30年间SOC时空变化;Maia等[6]分析巴西亚马逊东南部不同耕作措施下SOC的变化;Minasny等[7]在爪哇岛和韩国的研究表明,长期种稻促进水田表层SOC密度和储量大幅增加。
国内学者大多利用全国第二次土壤普查资料,结合不同时期的土壤采样或出版文献等数据,研究第二次土壤普查以来不同地区的SOC密度及储量变化特征。国家尺度上,Pan等[8]通过对比第二次土壤普查和耕地质量监测数据分析了全国水稻土表层SOC储量变化和固碳潜力。黄耀等[9,10,11]利用文献数据研究了第二次土壤普查以来全国农田表层SOC含量变化。Yu等[12]利用Agro-C模型模拟了1980-2009年全国耕地30 cm土层SOC储量变化。区域尺度上,根据样点的代表性和数量,多采用经典统计、或与GIS、地统计学相结合研究SOC的时空变化。Liao等[13]采用统计和GIS技术探讨了江苏省表层SOC储量变化与影响因素;揣小伟等[14]基于GIS技术估算了江苏省表层SOC储量的变化及其对土地利用变化的响应;张春华等[15]采用地统计方法研究了松嫩平原SOC的时空变化;王相平等[16]利用克里格插值法分析了玛纳斯地区农田SOC储量的变化特征;高建峰等[17]利用长期定位实验数据讨论了吴江市水田表层SOC储量的变化。此外付友芳等[18]采用《2006年IPCC国家温室气体清单指南》Tier2和基于文献数据的转移矩阵方法,估算2000-2007年内蒙古锡林郭勒盟草地30cm土层SOC储量变化。
据第二次土壤普查统计,安徽省约有31.1%的耕地的有机质含量低于15 g/kg[19],一定程度上制约了农业生产。许信旺等[20,21]利用安徽省第二次土壤普查资料分析了全省SOC密度空间分布特征,但对于SOC密度变化特征和驱动因素的研究较少。因此,本文利用安徽省第二次土壤普查数据和2010-2011年土壤调查数据,运用GIS技术探讨第二次土壤普查以来全省表层（0~20 cm）和1 m土体中SOC密度和储量的时空变化特征及对土地利用变化的响应,为土壤固碳潜力和肥力管理等研究提供基础数据。

2 研究方法与数据来源

2.1 研究区概况

安徽省（114°54′E~119°37′E、29°41′N~34°38′N）地处长江、淮河流域中下游,属亚热带与暖温带的过渡地区,年均气温14°C~16°C,年均降雨800~1800 mm,总面积13.96万km2。全省地貌南北差异较大,分为五个地理区域：由北至南为淮北平原、江淮丘陵岗地、沿江平原区、皖西大别山区和皖南丘陵山区（图1）,分布着潮土、水稻土、砂姜黑土、黄棕壤和黄褐土等土壤。淮北平原以小麦—玉米（大豆）轮作为主,沿江平原和江淮丘陵区以小麦（油菜）—晚稻轮作为主,皖西和皖南地区林、茶为主。
Fig. 1 Spatial distribution of typical soil profiles in Anhui province

图1 安徽省典型土壤剖面空间分布

注：I. 淮北平原、II. 江淮丘陵岗地、III. 沿江平原、IV. 皖西大别山区、V. 皖南丘陵山区。

2.2 数据来源

2.2.1 土壤样品采集 1980年土壤数据来源于《安徽土种》[22]记录的218个典型土壤剖面,采样在1980年前后,本文将时间定为1980年。2010年土壤数据来源于国家科技基础性工作专项“我国土系调查与《中国土系志》编制”（2008FY110600）、中国科学院战略性先导科技专项子课题“华东农田固碳潜力与速率研究”（XDA05050503）中安徽省土壤数据集,共208个典型土壤剖面,采样时间为2010-2011年。样点采集按照地形—母质—土地利用等景观要素组合,同时样点尽量布设在第二次土壤普查时期的典型剖面附近（图1）。SOC含量采用重铬酸钾（K2Cr2O7）氧化—滴定法测定[23]。
2.2.2 空间数据 空间数据包括：① 安徽省1:50万土壤类型图;② 1980年和2010年土地利用图,由长江三角洲科学数据共享平台（http://nnu.geodata.cn）提供,该数据主要利用Landsat MSS和TM影像目视解译获得,ArcGIS矢量格式;③ 安徽省地貌单元分区图。

2.3 有机碳密度和储量的计算方法

SOC密度的估算公式如下：
SOCD = ∑ i = 1 n ( 1 - θ i % ) × ρ i × C i × T i / 100 （1）
式中：SOCD为一定厚度土体的SOC密度（kg/m2）;n为土层数;θi为第i层>2 mm的砾石的体积百分比;ρi为第i层土壤容重（g/cm3）;Ci为第i层SOC含量（g/kg）;Ti为第i层土层的厚度（cm）。第二次土壤普查中,部分土层的容重数据未测,根据所属的土壤类型采用相同土层的容重的平均值代替。
SOC储量的估算公式如下：
C = ∑ i = 1 n SOCD × S i / 1000 （2）
式中：C表示区域的SOC储量（t）;Si表示某一土壤类型图斑的面积（m2）;n表示区域内GIS图层中土壤类型图斑的数量。

2.4 研究方法

按照公式（1）估算出两个时期安徽省典型土壤剖面的表层和1m土体中SOC密度,利用SPSS 18对SOC密度进行描述性统计、方差分析等。然后利用基于土壤学专业知识（pedological professional knowledge-based,PKB）的方法[24]在ArcGIS中将土壤剖面与数字化土壤图连接,绘制安徽省SOC密度的空间分布图,并估算SOC储量。按100m栅格分辨率将两个时期土壤有机碳图转换为栅格格式,并利用区域统计功能分析全省、不同土壤类型、土地利用和地理区域的SOC密度时空格局演变及碳储量变化。

3 结果分析

3.1 土壤有机碳密度的时间变化

1980-2010年,全省表层SOC密度平均减少0.37 kg/m2,极差和标准差均减小（表1）。变异系数从78.20%降低至37.79%,相比1980年,2010年SOC密度的变异程度降低。与1980年相比,全省1 m土体中SOC密度平均减少1.63 kg/m2（表1）,其标准差和变异系数均有大幅度的降低,表明2010年1 m土体中SOC密度的变异程度也有较大幅度降低。
Tab. 1 Statistics of SOC density of Anhui province in 1980 and 2010

表1 1980-2010年安徽省土壤有机碳密度的统计值

统计单元 样本数（个） 表层SOC密度（kg/m2） 1 m土体SOC密度（kg/m2）
1980年 2010年 1980年 2010年 变化 1980年 2010年 变化
总体 218 208 3.44±2.691) 3.07±1.16 -0.37 9.62±8.28 7.99±3.84 -1.63
地理区域 淮北平原 44 49 1.54±0.57a2) 2.68±0.64a 1.14 5.45±2.17a 7.05±2.56a 1.60
江淮丘陵岗地 16 33 2.90±1.50b 2.78±0.93a -0.12 8.19±4.77ab 8.08±3.23a -0.11
沿江平原 72 39 3.12±1.63b 3.65±1.20c 0.53 10.24±7.50bc 10.02±4.05b -0.22
皖西大别山区 19 18 4.49±4.24c 2.78±1.16ab -1.71 14.37±18.06c 6.93±4.21a -7.44
皖南丘陵山区 67 69 4.86±3.21c 3.28±1.35b -1.58 10.69±6.90bc 7.74±4.29a -2.95
土地利用 旱地 78 85 2.00±1.32a 2.69±0.78a 0.69 6.57±4.51a 7.48±2.91ab 0.91
水田 85 77 3.68±1.52b 3.80±1.12b 0.12 11.22±7.10b 10.35±4.16b -0.87
草地 15 3 2.75±1.58ab 2.23±1.33a -0.52 5.76±8.28a 5.25±6.10a -0.51
林地 40 43 5.98±4.44c 2.77±1.39a -3.21 13.69±13.47b 6.39±3.81ab -7.30

注：1）均值±标准差;2）同一列中数字后的相同字母表示不同地理区域间属性无显著性差异（p<0.05）

1980-2010年,安徽省不同地理区域和不同土地利用的SOC密度变化差异较大。淮北平原SOC密度增加最多,表层和1 m土体平均增加了1.14 kg/m2和1.60 kg/m2。皖西大别山区和皖南丘陵山区表层和1 m土体中SOC密度减少较多,表层平均减少1.71 kg/m2和1.58 kg/m2,1 m土体平均减少7.44 kg/m2和2.95 kg/m2。不同土地利用中,旱地和水田的SOC密度增加,林地和草地的SOC密度减少。旱地的SOC密度增加较多,表层和1 m土体中平均增加了0.69 kg/m2和0.91 kg/m2;林地的SOC密度减少最多,表层和1 m土体中平均减少了3.21 kg/m2和7.30 kg/m2。结果表明,近30年间全省耕地SOC密度呈增加趋势,非耕地呈减少趋势。这主要因为耕地在长期的农业耕作中,大量生物量的不断输入,使得SOC累积较快。
从全省表层SOC密度频率分布（图2a）来看,1980年和2010年SOC密度均主要分布在1.5~3.0 kg/m2和3.0~4.5 kg/m2区间,2010年的样点比例较1980年分别下降了7.71%和13.60%。2010年表层SOC密度在<1.5 kg/m2和>6 kg/m2区间的样点比例较1980年分别增加了11.22%和10.95%。从1 m土体的SOC密度频率分布（图2b）来看,1980年和2010年SOC密度均主要分布在4~8 kg/m2和8~12 kg/m2区间,2010年的样点比例均略有下降,不足5%。在<4 kg/m2、12~16 kg/m2和>20 kg/m2三个区间,2010年1 m土体的SOC密度均有不同程度的增加。
Fig. 2 Frequency distribution of SOC density in Anhui province

图2 安徽省土壤有机碳密度频率分布

3.2 土壤有机碳密度空间分布特征

图3和图4为两个时期安徽省表层和1 m土体中SOC密度空间分布图。1980年全省表层和1 m土体中SOC密度空间分布特征明显,总体上均由北向南呈递增趋势,南北差异较大;到2010年这种空间分布趋势减弱,全省SOC密度空间差异减弱,沿江平原和江淮丘陵地区的SOC密度较高。
Fig. 3 Spatial distribution of SOC density in surface layer in Anhui province

图3 安徽省表层土壤有机碳密度空间分布图

Fig. 4 Spatial distribution of SOC density (1 m) in Anhui province

图4 安徽省1 m土体中有机碳密度空间分布图

1980年全省表层SOC密度主要分布在1.5~3.0 kg/m2和3.0~4.5 kg/m2,分别占土壤总面积的39.75%和21.91%,主要分布在江淮丘陵和沿江平原。表层SOC密度高值（>6.0 kg/m2）分布在皖南丘陵山区西部占土壤面积的14.00%,低值（<1.5 kg/m2）占土壤面积的19.57%,主要分布在淮北平原（图3a）。相比1980年,2010年全省表层SOC密度仍然集中分布在1.5~3.0 kg/m2和3.0~4.5 kg/m2,但面积比例有所增加,分别为39.81%和48.09%。SOC密度高值和低值的区域大幅度减少,面积比例分别减少12.41%和16.83%,零星分布在皖南丘陵山区和皖西大别山区（图3b）。
1980年全省1 m土体中SOC密度集中在4~8 kg/m2,占土壤总面积的53.19%,主要分布在全省平原地区和丘陵岗地的大部分地区。1 m土体中SOC密度高值（>20 kg/m2）主要分布在皖南丘陵地区西部,占土壤面积的9.31%;低值（<4 kg/m2）主要分布在淮北平原最北端和皖西大别山区（图4a）。对比1980年,2010年全省1m土体中SOC密度空间分布格局有所变化,集中在8~12 kg/m2,占总面积的60.02%,主要分布在江淮丘陵和沿江平原;其次是4~8 kg/m2,占土壤总面积的21.84%,主要分布在淮北平原和皖南丘陵地区。2010年SOC密度高值区域大幅度减少,不足总面积的1%;低值区域主要分布在皖西大别山区（图4b）。

3.3 土壤有机碳密度空间变化特征

图5为1980-2010年安徽省SOC密度空间变化。1980-2010年,全省SOC密度变化为北增南减,增加幅度由北向南依次减小。1980-2010年,全省表层SOC密度增加的面积占56.97%,主要分布在淮北平原,在沿江平原的东部和江淮丘陵区的西部也有零星分布。增加的范围集中在0~1 kg/m2和1~2 kg/m2之间（图5a）,分别占总面积的24.34%和20.82%。增加最多（>2 kg/m2）的区域在江淮丘陵岗地的西部,占总面积的11.81%。表层SOC密度减少集中在-1~0 kg/m2和<-2 kg/m2之间,占总面积的22.32%和14.38%,主要分布在皖南丘陵山区;该地区西部SOC密度降幅为<-2 kg/m2,东部变化为-1~0 kg/m2。皖西大别山区和沿江平原连接区,SOC密度降幅主要在-1~0 kg/m2和<-2 kg/m2之间。
Fig. 5 Spatial changes of SOC density in Anhui province

图5 安徽省土壤有机碳密度空间变化分布图

1980-2010年,全省1 m土体中SOC密度增加的面积占58.21%,主要分布在淮北平原、江淮丘陵岗地（图5b）,其中集中在0~3 kg/m2的占34.65%,其次为3~6 kg/m2,占总面积的17.50%。沿江平原的长江沿岸、淮北平原东部的零星区域SOC密度增加最多（>6 kg/m2）,占总面积的5.86%。SOC密度降低的范围集中在-3~0 kg/m2和<-6 kg/m2,占总面积的20.46%和17.21%,主要分布在皖南丘陵山区,该地区西部SOC密度降幅较大,东部降幅较小。皖西大别山区的东南部,有机碳密度降幅也较大,在6 kg/m2以上。
对比各地理区域SOC密度变化的面积比例发现,由北至南SOC密度增加的面积比例逐渐减少。例如,淮北平原表层和1 m土体中SOC密度增加的面积分别占该区域总面积的88%和76%;沿江平原SOC密度增加和减少的面积基本上持平;皖南丘陵山区表层和1 m土体中SOC密度增加的面积占该区域总面积的15%和27%。

3.4 1980-2010年安徽省土壤有机碳储量变化

1980-2010年间安徽省表层SOC储量减少34.23×109 kg,1 m土体中SOC储量减少197.26×109 kg（表2）,虽然这一时期全省SOC储量总体减少,但不同区域SOC储量变化存在较大差异。近30年来淮北平原、江淮丘陵岗地和沿江平原表层SOC储量有不同程度的增加,淮北平原增加最多,为49.56×109 kg;皖西大别山区和皖南丘陵山区SOC储量大幅度减少,分别减少77.10×109 kg和17.23×109 kg。与表层SOC储量相比,1 m土体中SOC储量变化略有不同,仅淮北平原和江淮丘陵岗地SOC储量增加,其余地区均减少。
Tab. 2 SOC storage changes in various geographic areas and soil types from 1980 to 2010

表2 1980-2010年各地理区域和土壤类型有机碳储量变化

面积
（km2）		 表层SOC储量（×109 kg） 变化
（×109 kg）		 1 m土体SOC储量（×109 kg） 变化
（×109 kg）
1980年 2010年 1980年 2010年
全省 134843.79 450.97 416.74 -34.23 1231.55 1034.29 -197.26
地理
区域		 淮北平原 47460.75 91.31 140.87 49.56 294.96 375.79 80.83
江淮丘陵岗地 15062.73 40.77 48.42 7.65 107.84 123.30 15.46
沿江平原 29631.25 99.79 102.67 2.88 287.90 269.69 -18.21
皖西大别山区 13333.60 49.72 32.49 -17.23 133.66 60.41 -73.25
皖南丘陵山区 29355.46 169.38 92.29 -77.09 407.20 205.10 -202.10
土壤
类型		 砂姜黑土 20948.22 34.47 62.80 28.33 126.08 172.41 46.33
水稻土 40157.67 135.18 154.480 19.30 377.08 385.72 8.64
黄褐土 13512.70 22.79 37.79 15.00 76.89 97.54 20.65
潮土 16827.32 31.64 45.13 13.49 98.66 130.12 31.46
石质土 825.57 1.40 1.78 0.38 1.40 1.78 0.38
山地草甸土 1.30 0.02 0.00 -0.02 0.02 0.02 0.00
棕壤 928.55 5.63 2.11 -3.52 13.82 5.78 -8.04
紫色土 3207.88 8.91 5.05 -3.86 27.55 7.81 -19.74
黄壤 969.85 7.68 3.79 -3.89 12.92 10.68 -2.24
黄棕壤 4785.08 22.74 13.98 -8.76 45.54 33.67 -11.87
石灰岩土 3947.48 31.17 20.28 -10.89 57.05 42.00 -15.05
粗骨土 10422.74 44.39 20.01 -24.38 160.25 26.72 -133.53
红壤 18309.43 104.94 49.53 -55.41 234.28 120.05 -114.23
不同土壤类型中,砂姜黑土、水稻土、黄褐土、潮土、石质土的SOC储量增加,其他土壤类型的SOC储量均降低。从表层SOC储量变化看,砂姜黑土和水稻土增加较多,粗骨土和红壤减少较多;从变化速率来看,砂姜黑土和黄褐土较高,为450.74 kg/hm2/a和369.98 kg/hm2/a;山地草甸土和黄壤较低,为-3580.77 kg/hm2/a和-1336.78 kg/hm2/a。从1 m土体中SOC储量变化看,砂姜黑土和潮土增加较多,粗骨土和红壤减少较多;从平均变化速率来看,砂姜黑土和潮土较高,粗骨土和棕壤较低。
总体上,1980-2010年全省耕作区域SOC储量呈增加趋势,非耕作区域SOC储量减少。安徽省SOC储量变化的空间差异主要与各地理区域的自然和人为因素有关。淮北平原、江淮丘陵岗地和沿江平原以农业耕作为主,主要分布着潮土、砂姜黑土和水稻土等耕作土壤,长期的耕作管理和肥料使用等,不断有大量的生物量进入土壤,使得SOC密度和储量总体增加。而皖西和皖南地区以林地和草地为主,地形起伏较大,严重的水土流失可能是导致区域内SOC储量大量减少的主要原因。1980-2010年,皖西大别山区土壤侵蚀模数平均535.05 t/km2/a~1406.16 t/km2/a,土壤侵蚀总量占全省侵蚀总量的21.52%~30.09%;皖南丘陵山区土壤侵蚀模数平均为697.28 t/km2/a~1117.85 t/km2/a,侵蚀总量占全省的50.49%~61.69%[25]。皖西和皖南地区的土壤侵蚀强度相当于土壤流失厚度平均为0.37 mm/a~0.74 mm/a。严重的水土流失导致土层变薄。1980-2010年皖西地区土体（1 m土体内）的有效土层厚度由79.58±24.41 cm（19个剖面）减少到71.16±28.34 cm（18个剖面）;其中林地的土层厚度由77.88±26.55 cm（9个剖面）减少到47.89±14.49 cm（9个剖面）,减少达30 cm。1980-2010年皖南地区的有效土层厚度虽然由80.88±25.49 cm（67个剖面）增加到84.85±24.50 cm（69个剖面）,但是林地的土层厚度由68.36±29.39 cm（21个剖面）减少到60.65±24.25 cm（26个剖面）。而皖南丘陵山区土壤的形成速率仅为0.06 mm/a[26],水土流失和土壤形成速率的不平衡,使得区域内SOC含量较高的表土不断流失,进而导致该地区SOC储量大幅降低。

3.5 土地利用变化对土壤有机碳储量变化的影响

表3为1980-2010年不同土地利用变化区域的SOC变化结果。土地利用保持不变的区域中,SOC储量变化也存在较大差异。如旱地—旱地类型（1980、2010年土地利用均为旱地）的表层和1 m土体的SOC储量增加最多,为346.32×108 kg和589.27×108 kg。水田—水田类型表层SOC储量增加了76.22×108 kg,1 m土体的SOC储量减少了191.14×108 kg。草地—草地、林地—林地和荒地—荒地类型的表层和1 m土体的SOC密度减少程度相当,由于林地—林地类型面积较大,其SOC储量减少较多。
Tab. 3 Eigenvalues of changes in SOC storage caused by land use change in 1980 and 2010

表3 1980-2010年不同土地利用变化的土壤有机碳储量变化特征值

土地利用变化 面积（km2） 表层SOC 1 m土体SOC
密度变化（kg/m2） 储量变化（108 kg） 密度变化（kg/m2） 储量变化（108 kg）
水田—水田 41109.35 0.19±2.191) 76.22 -0.46±7.10 -191.14
水田—旱地 109.65 0.36±2.27 0.39 0.23±6.26 0.26
水田—林地 147.93 -0.88±2.73 -1.30 -2.01±8.95 -2.98
水田—草地 11.08 0.33±3.01 0.04 0.75±8.80 0.08
水田—荒地 3.79 -0.23±2.26 -0.01 -0.30±4.60 -0.01
旱地—旱地 34634.95 1.00±1.20 346.32 1.70±3.62 589.27
旱地—水田 333.61 1.01±1.49 3.35 1.80±3.75 6.00
旱地—林地 91.08 -1.42±3.63 -1.29 -6.71±13.80 -6.11
旱地—草地 22.14 -2.14±3.68 -0.48 -4.74±8.20 -1.05
旱地—荒地 6.07 -0.24±2.82 -0.01 -2.55±10.04 -0.16
林地—林地 31242.56 -2.29±3.19 -716.98 -6.72±10.90 -2100.38
林地—水田 45.26 -1.57±2.84 -0.71 -6.19±12.14 -2.80
林地—旱地 151.65 -0.70±2.13 -1.06 -1.01±8.20 -1.53
林地—草地 246.57 -3.47±4.05 -8.55 -7.99±11.26 -19.71
林地—荒地 28.42 -2.99±3.09 -0.85 -4.36±5.32 -1.24
草地—草地 7412.10 -2.03±3.36 -150.48 -5.23±9.55 -387.76
草地—水田 16.52 -1.55±3.73 -0.26 -4.78±7.78 -0.79
草地—旱地 239.98 0.05±2.32 0.11 0.87±11.37 2.09
草地—林地 157.26 -0.18±2.11 -0.29 0.45±6.84 0.71
草地—荒地 146.60 -3.17±4.51 -4.65 -5.91±6.89 -8.66
荒地—荒地 4.72 -2.01±2.95 -0.10 -5.98±12.87 -0.28

注：1）均值±标准差。

一般来说水田的1 m土体中SOC密度和储量变化由表层SOC变化决定,且变化相对一致,但本文中二者的变化趋势相反。通过分析1980-2010年土壤采样数据认为,长期机械化耕作、同时机耕深度一般达25~30 cm（较传统的耕作深度13~18 cm要深）,打破了水稻土（水田）原有的犁底层,导致犁底层的容重降低,增加了土壤的通气性[27],加快了表下层土壤的有机质矿化分解,从而使得表下层SOC含量和密度下降。1980-2010年全省水田的耕作层（Ap层）厚度由15.11±2.54 cm增加到19.30±5.14 cm;水田表层（0~20 cm）的土壤容重由1.30±0.12 g/cm3（39个剖面①(① 二次普查时期土壤容重不是必测属性,仅有39个水稻土剖面的所有土层均有容重数据,所以1980年的容重分析样点为39个。)）降低到1.26±0.11 g/cm3（77个剖面）,表下层（20~40 cm）的容重由1.52±0.10 g/cm3（39个剖面）降低到1.46±0.12 g/cm3（77个剖面）。近30年全省水田表下层（20~40 cm）土壤有机质含量由15.19±15.80 g/kg（85个剖面）下降到11.98±7.15 g/kg（77个剖面）。1980-2010年,全省机械耕作面积由1.04×104 km2增加到4.06×104 km2,一般机耕深度达30 cm,机械收割面积由0.06×104 km2增加到5.26×104 km2 [28]。这些数据证实了本文的推测。因此,农业耕作措施的改变,机械化深耕,是安徽水田1 m土体中SOC储量下降的主要诱因。
而全省林地—林地、草地—草地类型的1 m土体SOC储量大幅度减少的主要原因是水土流失导致富含SOC的表土流失,裸露出的SOC含量较低的表下层土壤成为新的表土,同时1 m土体内有效土层厚度变薄。1980-2010年全省80%以上的林地面积,60%以上的草地面积分布在皖西和皖南地区,约有30%的草地面积分布在江淮丘陵地区和沿江平原的低矮山丘上,这些区域水土流失较严重[25]。通过上文分析得知,皖西和皖南的水土流失严重,在30年来区域内1 m土体内的实际土层的厚度、林地和草地的土层厚度减少较多。1980年、2010年林地和草地的土壤采样剖面大多数分布在皖西和皖南地区。根据采样点数据分析,1980-2010年全省林地土壤的有效土层厚度由75.43±25.49 cm（40个剖面,其中30个剖面位于皖西和皖南地区）减少到68.86±26.03 cm（43个剖面,其中35个位于皖西和皖南地区）;其中皖西地区林地的土层厚度由77.88±26.55 cm（9个剖面）减少到为47.89±14.49 cm（9个剖面）;皖南地区林地的土层厚度由68.36±29.39 cm（21个剖面）减少到60.65±24.25 cm（26个剖面）。1980-2010年草地土壤的有效土层厚度由68.13±36.08 cm（15个剖面,其中13个位于皖西和皖西地区）减少到36.00±21.17 cm（3个剖面均位于皖西地区）。
对于土地利用发生变化的区域,表层SOC密度变化从-3.47±4.05 kg/m2到1.01±1.49 kg/m2。旱地—水田（1980年到2010年旱地转变为水田）表层SOC密度平均增加了1.01 kg/m2,储量增加了3.35×108 kg。水田—旱地和水田—草地类型有机碳密度平均增加了0.36 kg/m2和0.33 kg/m2,储量分别增加了0.39×108 kg和0.04×108 kg。草地—旱地类型略有增加。其他变化类型的SOC密度有不同程度的减少,其中林地—草地和草地—荒地类型的SOC密度减少较多,为-3.47 kg/m2和-3.17 kg/m2,表层SOC储量分别减少8.55×108 kg和4.65×108 kg。土地利用变化区域中1 m土体的SOC密度变化规律与表层SOC密度变化规律相似。旱地—水田、水田—旱地、水田—草地、草地—旱地和草地—林地类型SOC密度增加,其余变化类型有机碳密度减少。
上述这些结果表明：对于非耕地（林地、草地和荒地）来说,转换为耕地（水田和旱地）比保持用地类型不变或转换为其他非耕地类型,SOC密度和储量减少相对较慢。耕地转换为非耕地,SOC密度和储量减少。耕地内部转换（水田—旱地、旱地—水田）比保持用地类型的SOC密度和储量增加较多。

4 结论与讨论

（1）1980-2010年安徽省表层和1 m土体中SOC密度总体呈减少趋势,平均减少0.37 kg/m2和1.63 kg/m2,但全省耕地SOC密度呈增加趋势,非耕地SOC密度呈减少趋势。全省SOC密度的变异程度大幅度降低。全省表层和1 m土体中SOC碳储量减少34.23×109 kg和197.26×109 kg。淮北平原、江淮丘陵岗地和沿江平原SOC储量增加,皖西大别山区和皖南丘陵山区减少。在空间分布上,全省表层和1 m土体中SOC密度变化呈现出北增南减趋势,SOC密度增加的面积略多于减少的面积。各地理区域SOC密度增加的面积比例由北至南逐渐减少。
（2）1980-2010年,全省土地利用变化对于SOC密度和储量变化影响差异较大。非耕地转换为耕地,比保持用地类型不变或变为其他非耕地类型,SOC密度和储量减少相对较慢。耕地转换为非耕地,SOC密度和储量减少。耕地类型内部转换比保持类型不变的SOC密度和储量增加较多。
（3）SOC密度和储量的空间变化除了受母质、气候、地形等结构化因素的影响,还受耕作管理等随机因素的影响,因此相同土壤类型的SOC密度和储量也存在一定范围的随机变异。本研究采用GIS软件将典型土壤剖面与数字化土壤类型图斑连接估算了SOC密度和储量的空间变化。全省范围内两个时期的典型土壤剖面包含了所有土壤图中的土属类型,估算的结果能够反映全省SOC密度和储量的变化趋势。而淮北平原（I区）和江淮丘陵区（II区）的两个时期的典型土壤剖面点的空间分布存在较大差异,SOC储量变化结果中会存在由随机因素引起的不确定性;但是两个时期、两个区的土壤剖面基本覆盖了相应区域的主要土壤类型（土壤图中的亚类或土属级别）,因此估算结果也能够反映区域SOC储量的变化趋势。
此外,根据2010-2011年的采样调查数据,安徽省农作物以机械收割为主,留茬较高。小麦平均留茬高度在20.2 cm,机械收割比例占95.2%;早、中、晚稻平均留茬高度在18.2 cm、23.1 cm、18.5 cm,机械收割比例45.3%、78.1%、52.4%;大豆留茬高度7.8 cm,机械收割比例85.3%。油菜和玉米机械收割比例较低,分别为21.3%和4.9%,留茬高度在20.1 cm和11.3 cm。基本上高于安徽省农机作业质量标准中的15 cm留茬高度。在积极推行秸秆还田、严禁焚烧秸秆等农业管理措施的影响下,大量农作物的残茬在机械化耕作中被碾碎还田,增加了进入土壤中的有机物质。因此机械化收割比例大、留茬高等,在一定程度上促进了安徽省SOC的累积。
致谢：感谢中国科学院南京土壤研究所博士研究生杨帆,在数据整理中给予的帮助。

The authors have declared that no competing interests exist.

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DOI

[9]
黄耀, 孙文娟. 近20年来中国大陆农田表土有机碳含量的变化趋势. 科学通报, 2006, 51(7): 750-763.调研并分析了中国大陆1993年以来关于区域农田土壤有机碳变化的文献200余篇. 为了客观评价中国大陆农田有机碳的变化, 从中选出132篇具有代表性的文献, 这些文献涵盖了不同地区60000余个土壤样品的测定结果. 分析结果表明, 近20年来占中国大陆农田面积53%~59%的土壤有机碳含量呈增长趋势, 30%~31%呈下降趋势, 4%~6%基本持平. 进一步分析结果指出, 中国大陆农田表土有机碳贮量总体增加了311.3~401.4 Tg. 其中, 华东和华北地区增加明显, 但东北地区呈下降趋势. 有机碳含量增加明显的土壤类型为水稻土和潮土, 黑土下降显著. 有机碳含量增加主要归因于秸秆还田与有机肥施用、化肥投入增加与合理的养分配比以及少(免)耕技术的推广; 黑土区有机碳含量下降的主要原因是水土流失和投入不足. 为了有效地促进农田土壤碳固定, 最大限度地遏制东北地区土壤有机碳下降的趋势, 未来应通过配套技术的研究、农户培训和政府补贴等措施, 进一步推广秸秆还田、平衡施肥、少(免)耕等保护性耕作措施, 加大水土流失的综合治理力度. 与此同时, 为了应对后《京都议定书》时代对中国可能产生的减排压力, 未来需加强4个方面的研究: (1)第二次土壤普查期间及目前中国农田土壤有机碳贮量, (2)由自然因素和人为因素控制的农田土壤有机碳变化机理, (3)增加土壤碳固定及减少碳损失的有效途径, (4)农田土壤的固碳潜力及未来演变趋势.

[Huang Yao, Sun Wenjuan.Changes of topsoil organic carbon content in Chinese mainland in recent 20 years. Chinese Science Bulletin, 2006, 51(7): 750-763.]

[10]
于严严, 郭正堂, 吴海斌. 1980-2000年中国耕作土壤有机碳的动态变化. 海洋地质与第四纪地质, 2006, 26(6): 123-130.

[Yu Yanyan, Guo Zhengtang, Wu Haibin.Change in organic carbon of cultivated soils in China from 1980 to 2000. Maine Geology & Quaternary Geology, 2006, 26(6): 123-130.]

[11]
许信旺, 潘根兴, 汪艳林, 等. 中国农田耕层土壤有机碳变化特征及控制因素. 地理研究, 2009, 28(3): 601-612.通过收集我国1980～2006年以来966个样点农田耕层土壤有机碳的实测数据,以及各样点的气温和降水数据,分析中国农田土壤有机碳变化特征,对变化的原因和发展趋势进行了探讨,对比分析了气温与降水对水稻土与旱作土固碳能力的差异,以及气温和降水对不同区域土壤有机碳的影响.结果表明:总体上我国实测点耕作表层土壤有机碳呈上升趋势,79%增幅样本主要集中在年增幅为O～3%的区间.农田土壤有机碳的含量受制于气温与降水,及水热条件的组合.20年来,全国农田土壤耕层有机碳含量的分布格局没变.农田土壤有机碳的变化,主要受人类活动的影响.土地利用方式对土壤同碳差异明显,水稻土有机碳水平明显高于旱地,水田耕层有机碳含量为旱地耕层有机碳含量的175～176%.

DOI

[Xu Xinwang, Pan Genxing, Wang Yanlin, et al.Research of changing characteristics and control factors of farmland topsoil organic carbon in China. Geographical Research, 2009, 28(3): 601-612.]

[12]
Yu Y Q, Huang Y, Zhang W. Modeling soil organic carbon change in croplands of China, 1980-2009. Global and Planetary Change, 2012, 82-83: 115-128.78 We reported the spatiotemporal SOC changes in croplands of China with Agro-C model. 78 The SOC has increased by 730 (329 to 1095) Tg C since 1980. 78 The carbon sequestration was attributed to the production increase and the removal decrease. 78 Soils in Heilongjiang Province, northeast China suffered net carbon loss.

DOI

[13]
Liao Q L, Zhang X H, Li Z P, et al.Increase in soil organic carbon stock over the last two decades in China's Jiangsu province. Global Change Biology, 2009, 15(4): 861-875.Estimates of regional and national topsoil soil organic carbon (SOC) stock change may help evaluating the soil role in mitigation of greenhouse gas (GHG) emissions through carbon (C) sequestration in soils. However, understanding of the exact mitigation role is often constrained by the uncertainty of the stock estimation associated with different methodologies. In this paper, a soil database of topsoil (0–20 cm) SOC measurements of Jiangsu Province, China, obtained from a soil survey in 1982, and from a geological survey in 2004, was used to analyze the variability of topsoil SOC among soil groups and among soil regions, and to estimate the change in SOC stocks that have occurred in the province over the last two decades. The soil survey data was obtained from measurements of 662 690 randomly collected samples, while the geological survey data was from 24 167 samples taken using a 2 km × 2 km grid. Statistical analysis was conducted on SOC values for 1982 and 2004 for different categories of soil groups, soil regions, and administrative municipalities, respectively. Topsoil SOC storage was then calculated and the provincial topsoil SOC stock was estimated for each sampling time. There were remarkable differences in SOC levels between soil groups and soil regions and different municipalities. The grid sampling with the geological survey in 2004 yielded smaller variability of topsoil SOC averages, both with soil groups and with soil spatial distribution than the random sampling method used in 1982. Variation of SOC was greater with soil groups than with soil regions in both sampling times, although it was less variable across soil taxonomic categories than within a spatial category. Little variance of the SOC level with soil groups could be explained by clay content. However, the prevalence of paddy fields in the total cropland area governed the regional and municipal average SOC levels. The average provincial topsoil SOC content increased from 9.45 g kg 611 in 1982 to 10.9 g kg 611 in 2004, and the total provincial topsoil SOC stock was enhanced from 149.0±58.1 Tg C in 1982 to 173.2±51.4 Tg C in 2004, corresponding to a provincial average SOC sequestration rate of 0.16±0.09 t C ha 611 yr 611 . The SOC sequestration trend for the last two decades could be, in part, attributed to the enhanced agricultural production, symbolized by the grain yield per hectare. The results of SOC stock changes suggest a significant C sequestration in soils of Jiangsu, China, during 1980–2000, with paddy management playing an important role in regional SOC storage and sequestration capacity.

DOI

[14]
揣小伟, 黄贤金, 赖力, 等. 基于GIS的土壤有机碳储量核算及其对土地利用变化的响应. 农业工程学报, 2011, 27(9): 1-6.土地利用变化是影响土壤有机碳储量变化的重要驱动因素，为了进一步探讨土地利用变化对土壤碳储量的影响，该文根据土壤样点数据、土壤类型图、土地利用类型图，分析了江苏省1985年和2005年表层土壤有机碳密度的变化以及土地利用变化对表层土壤有机碳密度的影响，主要结论如下：1）江苏省表层土壤有机密度的空间变化趋势为：黄淮平原生态区南北差异明显，北部的沂沭泗平原丘岗以增加为主，南部的淮河下游平原以减少为主；沿海滩涂与海洋生态区持平为主；而长江三角洲平原生态区表现不一：沿江平原丘岗生态亚区以增加为主，而茅山宜溧低山丘陵生态亚区和太湖水网生态亚区均表现为有机碳密度的减少；2）各地类表层土壤有机碳密度均有所增加；耕地-林地、草地；草地-林地、建设用地；建设用地-耕地、草地、林地；水域的转出以及未利用地的转出等转换类型有利于土壤碳储量的增加、其他地类间的转换会造成一定的碳排放。

DOI

[Chuai Xiaowei, Huang Xianjin, Lai Li, et al.Accounting of surface soil carbon storage and response to land use change based on GIS. Transactions of the CSAE, 2011, 27(9): 1-6.]

[15]
张春华, 王宗明, 任春颖, 等. 松嫩平原玉米带土壤有机质和全氮的时空变异. 地理研究, 2011, 30(2): 256-268.采用地统计学和GIS相结合的方法,研究了松嫩平原玉米带1980~2005年间土壤有机质和全氮的时空变异特征。结果表明:去除异常值后,土壤有机质和全氮均符合对数正态分布,两个时期土壤有机质的平均含量分别为2.14%和2.54%,土壤全氮的平均含量均为0.12%。通过变异函数分析,两个时期土壤有机质和全氮均符合高斯模型,1980年土壤有机质和全氮的最大相关距离分别为532.6km和776.1km,而2005年二者的最大相关距离分别减小为269.7km和242.1km。1980年土壤有机质和全氮的空间变异受人为因素影响较小,2005年土壤有机质具有中等的空间变异性,全氮仍具有强烈的空间自相关性,但比1980年有所减弱。通过普通Kriging法局部插值,两个时期土壤有机质和全氮的空间分布呈现出非常相似的"高"和"低"含量区域,并具有明显的地理分布规律,整体保持着中部地区高、边缘地区低的分布特征。旱田、水田、林地和草地四种主要土地利用类型的有机质含量均有不同程度的提高;水田和林地的全氮含量有所提高,但旱田和草地变化不大。

DOI

[Zhang Chunhua, Wang Zongming, Ren Chunying, et al.Temporal and spatial variations of soil organic and total nitrogen in the Songnen Plain maize belt. Geographical Reaseach, 2011, 30(2): 256-268.]

[16]
王相平, 杨劲松, 金雯晖, 等. 近30a玛纳斯县北部土壤有机碳储量变化. 农业工程学报, 2012, 28(17): 223-229.研究玛纳斯县北部土壤有机碳时空变异特征，可以为当地土壤肥力管理提供理论依据。本文采用地统计学和GIS相结合的方法，研究了玛纳斯县北部地区1980－2011年间土壤有机碳的时空变异特征。研究结果表明：研究区32 a来1 m深土体土壤有机碳密度和储量呈现增加的趋势，分别较1980年二次土壤普查时增加1.81 kg/m2和7.7 ×106 kg；2011年0～20、>20～60和>60～100 cm土壤有机碳质量分数平均值为5.74、4.44和2.17 g/kg；0～20 cm和>20～60 cm土壤有机碳含量符合正态分布特征，相应土壤有机碳变异函数理论模型分别符合指数和球状模型；0～20 cm土壤有机碳和>20～60 cm土壤有机碳均具有中等程度的空间变异性，土壤有机碳的空间分布受土壤母质、地形等结构因素和耕作、施肥等随机因素的共同影响并呈现出南部和东北部高，中部地区偏低的分布特征；>60～100 cm土壤有机碳呈现出南部高北部低的空间分布特征。本文获取了玛纳斯县北部地区土壤有机碳时空变异特征，该结果对研究区域土壤肥力管理具有重要意义。

DOI

[Wang Xiangping, Yang Jinsong, Jin Wenhui, et al.Change of soil organic carbon reserve in northern Manasi county in last 30 years. Transactions of the CSAE, 2012, 28(17): 223-229.]

[17]
高建峰, 潘剑君, 刘绍贵, 等. 土地利用变化对吴江市水田土壤有机碳储量的影响分析. 地球信息科学学报, 2011, 13(2): 164-169.农业表层土壤碳库容易受人为强烈干扰,而又可以在较短的时间尺度上进行调节,当今我国经济发达地区土地利用变化必然会对土壤固碳产生重要影响。本研究以江苏省吴江市水稻土为例,利用新一代中分辨率成像光谱仪(MODIS)和TM/ETM影像提取了1984年稻田面积,以及这部分稻田在2000-2005年的土地利用变化状况。研究中以最大似然法对TM/ETM、MODIS影像应用归一化植被指数(NDVI)、增强型植被指数(EVI)和陆地水分指数(LSWI)掩膜的方法作了识别提取;同时,结合第二次全国土壤普查、2003年耕地地力调查点和吴江市农林局土肥指导站长期定位点的土壤有机碳数据估算了1984年和2000-2005年土壤碳库变化情况。结果表明:近20多年来尽管吴江市水稻土水耕熟化过程中有机碳总体呈增加的趋势,但由于大量稻田被非农用地所取代,导致土壤固碳能力大幅度下降,尤其从2001年开始从&quot;碳汇&quot;变成&quot;碳源&quot;。因此,在我国经济发达区应密切关注耕地转换成非农用地而导致的土壤有机碳的损失。

DOI

[Gao Jianfeng, Pan Jianjun, Liu Shaogui, et al.Influence of land use change on topsoil organic carbon storage of paddy fields in Wujiang city. Journal of Geo-Information Science, 2011, 13(2): 164-169.]

[18]
付友芳, 于永强, 黄耀. 2000-2007年内蒙古锡林郭勒盟草地土壤有机碳变化估计. 草业科学, 2011, 28(9): 1589-1597.以内蒙古锡林郭勒盟历年草地管理面积和不同草地管理下土壤有机碳变化的文献数据为基础，分别采用《2006年IPCC国家温室气体清单指南》Tier2和基于文献数据的转移矩阵方法，估算2000-2007年该盟草地土壤有机碳变化。结果表明，研究期内该盟草地土壤有机碳增加量为20.85~29.80 Tg，年均增加量2.61~3.72 Tg。其中，东乌珠穆沁旗、西乌珠穆沁旗、苏尼特左旗、苏尼特右旗、阿巴嘎旗和锡林浩特市有机碳增加占全盟总增加量的80%以上。采用IPCC方法2与转移矩阵法估算的土壤有机碳变化量在空间上具有很好的一致性，但前者的估计值比后者约低1/3。用两种方法估算的逐年有机碳变化量在时间序列上不具可比性，IPCC方法2估算的土壤碳贮量前3年增加迅速，转移矩阵法估算的土壤碳贮量后5年增加迅速。

[Fu Youfang, Yu Yongqiang, Huang Yao.Changes of soil organic carbon of grassland in the Xilinguole, Inner Mongolia from 2000 to 2007. Pratacultural Science, 2011, 28(9): 1589-1597.]

[19]
安徽省土壤普查办公室. 安徽土壤. 北京: 科学出版社, 1996.

[Office of Soil Survey in Anhui Province. Soil of Anhui Province. Beijing: Science Press, 1996.]

[20]
许信旺, 潘根兴, 曹志红, 等. 安徽省土壤有机碳空间差异及影响因素. 地理研究, 2007, 26(6): 1077-1086.

[Xu Xinwang, Pan Genxing, Cao Zhihong, et al.A study on the influence of soil organic carbon density and its spatial distribution in Anhui province of China. Geographical Research, 2007, 26(6): 1077-1086.]

[21]
程先富, 谢勇. 基于GIS的安徽省土壤有机碳密度的空间分布特征. 地理科学, 2009, 29(4): 540-544.在GIS技术支持下,建立安徽省土壤数据库,揭示安徽省土壤有机碳密度空间分布特征。结果表明:安徽省0~100 cm土体中土壤有机碳密度在0.92~40.97 kg/m<sup>2</sup>之间,均值为10.39 kg/m<sup>2</sup>;从空间分布上看,从北向南有机碳密度逐渐增加,有机碳密度大部分在3~19 kg/m<sup>2</sup>之间,其分布面积占总面积的89.72%;在各土壤类型中山地草甸土有机碳密度最大,而潮土、黄褐土、石质土有机碳密度较小;草地的有机碳密度最大,耕地最小;土壤有机碳密度与海拔高度之间存在高度相关,随着坡度、降雨量的增加,平均有机碳密度逐渐加大。

DOI

[Cheng Xianfu, Xie Yong.Sparial distribution of soil organic carbon density in Anhui province based on GIS. Scientia Geographica Sinica, 2009, 29(4): 540-544.]

[22]
安徽省土壤普查办公室. 安徽土种志. 北京: 科学出版社, 1996.

[Office of Soil Survey in Anhui Province. Soil Series of Ahui Province. Beijing: Science Press, 1996.]

[23]
张甘霖, 龚子同. 土壤调查实验分析方法. 北京: 科学出版社.. 2012.

[Zhang Ganlin, Gong Zitong.Soil Survey Laboratory Methods. Beijing: Science Press, 2012.]

[24]
Zhao Y C, Shi X Z, Weindorf D C, et al.Map scale effects on soil organic carbon stock estimation in North China. Soil Science Society of America Journal, 2006, 70(4): 1377-1386.ABSTRACT Digital soil maps of different scales have been compiled in China, but exactly how map scale affects the estimation of regional SOC (soil organic carbon) stocks remains unclear. To test the effect, median, mean, and a pedological professional knowledge based method (PKB) were used to link soil profiles to soil maps at five scales ranging from 1:500000 to 1:10000000 for the Hebei Province. Excluding the 1:4000000 soil map, SOC stocks decreased as the map scale decreased. The estimated SOC stocks obtained using the mean were always higher than those using the median or PKB method. The changes in estimation due to different map scales and linking methods affected the process of assigning SOCD (soil organic carbon density) values to digital soil surveys. The differences in SOCD values resulted from the change in the total nonurban land area of each soil type as a result of the different methods and scales of maps used in the regional SOC stock estimation process.

DOI

[25]
赵明松, 李德成, 张甘霖. 1980-2010年间安徽省土壤侵蚀动态演变及预测. 土壤, 2016, 48(3): 588-596.

[Zhao Mingsong, Li Decheng, Zhang Ganlin.Dynamic evolution and prediction of soil erosion in Anhui province from 1980 to 2010. Soils, 2016, 48(3): 588-596.]

[26]
Huang L M, Zhang G L, Yang J L.Weathering and soil formation rates based on geochemical mass balances in a small forested watershed under acid precipitation in subtropical China. Catena, 2013, 105(6): 11-20.Accurate weathering and soil formation rates in natural environment and their quantitative dependences on environmental factors remain poorly understood, despite their significance in the understanding of biogeochemical cycling and for the development of sustainable land-use strategies. In the present study, rates of weathering and soil formation on granite and their dependences on add precipitation were studied in a small forested watershed, Fengxingzhuang (FXZ), in subtropical China using geochemical mass balance equations and multiple regression analysis. Atmospheric input from wet and dry deposition, and stream output through runoff were monitored from March, 2007 to February, 2010. The physical and chemical properties of soil and granite rock were also determined. The results show that acid precipitation is very severe in the FXZ forested watershed by bringing in H+ both directly from strong acids (741 mol ha(-1) yr(-1)) and indirectly from nitrogen and sulfur transformations (831 mol ha(-1) yr(-1)), which serves as an important driving force for weathering and soil formation. The FXZ forested watershed currently remains as a net sink for hydrogen ion, inorganic nitrogen, sulfur, potassium, and aluminum, with a mean of 0.07, 1.60, 1.48, 0.10, and 0.44 g m(-2) yr(-1), respectively, and a net source for dissolved silicon, sodium, calcium, and magnesium, with a mean of 533, 2.95, 1.04, and 0.34 g m(-2) yr(-1), respectively. Based on geochemical mass balance equations, the weathering rate of granite (R) in the FXZ forested watershed is 1.04 +/- 0.65 t ha(-1) yr(-1), but varying according to the changes in environmental conditions such as rainfall amount, air temperature, and H+ input within different seasons. Correspondingly, soil formation rate (S) is 0.95 +/- 0.69 t ha(-1) yr(-1), which equals to 0.066 +/- 0.048 mm yr(-1) of soil depth, suggesting a base for establishing the soil loss tolerance value in the granitic region of subtropical China. Acid precipitation significantly promotes weathering and soil formation by the input of rainfall and H+, although air temperature effects occur simultaneously. A proposed model that quantitatively describes weathering and soil formation rates is a combined product of rainfall amount (x(1)), H+ input (x(2)) and air temperature (x(3)) resulting from multiple regressions: R = 0.00045(*)x(1) + 0.026(*)e(0.0022x2) + 0.012(*)e(0.0459x3); S = 0.00035(*)x(1) + 0.029(*)e(0.002x2) + 0.016(*)e(0.0424x3), which improves the prediction from simple linear regression. (C) 2013 Elsevier B.V. All rights reserved.

DOI

[27]
孙国峰, 徐尚启, 张海林, 等. 轮耕对双季稻田耕层土壤有机碳储量的影响. 中国农业科学, 2010, 43(18): 3776-3783.<P><FONT face=Verdana>【目的】针对南方稻田连续免耕存在的有机碳表层富集现象,进行土壤轮耕效应的初步研究。【方法】试验选择双季稻区连续免耕7年稻田,研究了轮耕对耕层土壤有机碳含量及其对等质量法计算的耕层土壤有机碳储量影响。【结果】长期免耕后,翻耕、旋耕降低了表层0—5 cm土壤有机碳含量,提高了下层5—20 cm土壤有机碳含量,进而降低了耕层土壤有机碳层化率;而翻耕、旋耕后免耕土壤有机碳含量相对于翻耕、旋耕分别呈相反的趋势。2006—2009年表层600 Mg<I>&#</I>8226;hm-2土壤有机碳储量均以长期免耕最高。长期免耕后,翻耕、旋耕秸秆还田会提高下层土壤有机碳储量,进而在一定程度上影响耕层2 550 Mg<I>&#</I>8226;hm-2土壤有机碳的累积;而翻耕、旋耕后免耕耕层土壤有机碳储量较翻耕、旋耕有所降低。【结论】长期免耕后,连续免耕秸秆还田会增加表层600 Mg<I>&#</I>8226;hm-2土壤有机碳储量;而翻耕、旋耕秸秆还田会提高下层土壤有机碳储量。<BR></FONT></P>

[Sun Guofeng, Xu Shangqi, Zhang Hailin, et al.Effects of rotational tillage in double rice cropping region on organic carbon storage of the arable paddy soil. Scientia Agricultura Sinica, 2010, 43(18): 3776-3783.]

[28]
安徽省统计局. 安徽统计年鉴(1999-2011年)电子版. , 2018-03-02.

[Statistical Bureau of Anhui Province. Statistical Yearbooks of Anhui (1999-2011). , 2018-03-02.]

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