水保所知识产出(1956---)知识库

准确获取农田局域尺度上土壤有机碳变化影响因子是准确估算农田土壤有机碳
储量的基础，研究农田土壤有机碳储量及固碳机制，对进一步探讨我国农业固碳的潜
力和途径具有重要意义。本研究立足西北干旱区县域尺度（以平罗县为例），研究农
田土壤固碳现状和速率；采用物理分组方法研究农田土壤及其团聚体有机碳含量的分
布特征，并结合 XANES 技术研究土壤有机碳主要官能团的含量组成与化学稳定性特
征，探讨农田土壤团聚体对有机碳的物理保护及化学稳定性机制，为该区域农田土壤
固碳潜力估算和固碳机制提供依据。主要研究结果如下：
1、表层土壤容重空间变异性特征：
平罗县农田表层土壤容重的变化范围是 1.079～1.612 g/cm 3 ，平均值为 1.355±
0.107 g/cm 3 ，变异系数为 0.080，属于弱变异性；在空间上呈由西向东逐渐减小的南
北走向的条带状分布格局。粉粒、砂粒含量和土地利用方式是影响其空间分布的主要
因素。
2、土壤有机碳储量与固碳速率：
从 1980 年到 2011 年，平罗县农田土壤有机碳含量与有机碳密度（SOCD）均显
著增加。31 年中平罗县农田表层有机碳固碳量增加 45.5 万t，单位面积有机碳增量为
6690.38 kg C·ha -1 ，SOCD平均变化速率为 215.82 kg C·ha -1 ·yr -1 。农田土壤表层固碳量
增加的面积占 95.15%、减少的面积占 3.17%、相对平衡的面积占 1.69%。除灰钙土外，
各土壤类型的固碳量均有所增加，灌淤土、盐土、潮土三种土壤类型对固碳量提高的
贡献较明显。土壤初始有机碳含量、根茬量、氮肥投入量、留茬量是土壤固碳的主要
影响因子。
3、土壤有机碳组分特征：
不同土壤类型的总土壤有机碳含量（1m 剖面加权平均值）表现为：盐土（5.37
±0.17 g/kg）>灌淤土（4.89±0.40 g/kg）>潮土（4.06±0.55 g/kg）。耕层有机碳含量
最高，并表现为灌淤土（8.49±0.49 g/kg）>盐土（8.14±0.81 g/kg）>潮土（6.52±0.65g/kg）。
在旱作条件下，土壤重组有机碳（HFOC，1 m 剖面加权平均值）含量表现为灌
淤土（5.12±0.65 g/kg）>盐土（4.37±0.48 g/kg）>潮土（3.29±0.34 g/kg）、矿物结
合态有机碳（MOM）含量表现为灌淤土（4.40±0.56 g/kg）>盐土（4.25±0.44 g/kg）
>潮土（3.12±0.14 g/kg）；颗粒有机碳（POC）含量表现为灌淤土（1.08±0.44 g/kg）
>盐土（0.98±0.41 g/kg）>潮土（0.64±0.08 g/kg），而轻组有机碳（LFOC）含量表
现为盐土（0.87±0.18 g/kg）>潮土（0.46±12 g/kg）>灌淤土（0.37±0.11 g/kg）。水
田利用方式下，HFOC、MOM 含量在潮土中最高，其次为盐土、灌淤土。LFOC、POC
表现为灌淤土中含量最高，其次为盐土与潮土。旱作条件下各有机碳组分含量均高于
水田。
耕层土壤 HFOC、MOM、POC 三种有机碳组分的含量最高。随着剖面深度的增
加呈现出明显的降低趋势。土壤 POC、MOM、HFOC 与总有机碳含量均呈极显著正
相关（P<0.01），而 LFOC 与总有机碳含量关系不明显。
4、土壤团聚体及其有机碳分布特征：
1）>0.25 mm 的水稳性团聚体含量在耕层最高，为 63.81%，明显高于母质层
（36.15%）；团聚体破坏率在耕层最低，为 27.71%，而母质层为 46.28%。灌淤土团
聚体破坏率平均为 32.27%，低于盐土（44.36%）、潮土（44.72%），说明灌淤土团聚
体稳定性最强。旱地土壤团聚体稳定性高于水田土壤，旱地土壤>0.25 mm 水稳定性
团聚体含量（51.25%）>水田（40.60%）；旱地的团聚体破坏率为 37.60%，明显低于
水田（43.30%）。>0.25 mm 水稳性团聚体含量和土壤有机碳含量呈正相关，说明土壤
有机碳含量的提高对土壤大团聚的形成有促进作用。
2）土壤有机碳主要蓄存在>0.25 mm 粒径的团聚体中。不同土壤类型的>0.25 mm
粒径的团聚体有机碳平均含量为灌淤土（8.35±0.08 g/kg）>盐土（8.05±0.12 g/kg）
>潮土（6.92±0.09 g/kg）。旱地>0.25 mm 粒径的团聚体有机碳平均含量为 8.13±0.08
g/kg，明显大于水田（7.83±0.42 g/kg）。
3）土壤团聚体的 HFOC、MOM、POC 主要固定在>0.25 mm 的各级团聚体中。
灌淤土与盐土各粒级团聚体 HFOC、MOM、POC 含量明显高于潮土；旱地各个粒级
团聚体 HFOC、POC 含量略高于水田。
4）>0.25 mm 土壤团聚体稳定性有机碳（HFOC、MOM）与团聚体有机碳均呈极
显著的正相关（P<0.01）。
5、表层土壤有机碳官能团特征：随着团聚体粒径增大，灌淤土活性较强的 O-烷基-C、羧基-C 相对百分含量有所
减少，较稳定的芳香-C 相对百分含量有所增加。而盐土，较稳定的芳香-C 相对百分
含量均有所减少，活性的羧基-C 相对百分含量均有明显增加。与旱地相比，水田条
件土壤有机碳官能团的化学稳定性提高。
关键词：土壤固碳速率，团聚体，有机碳组分，有机碳官能团

Accurately obtain farmland soil organic carbon impact factor on a local scale is the
basis of exactly estimating farmland soil organic carbon storage. The research of soil
organic carbon storage and sequestration mechanism is great importance to understand the
potentials and means of agricultural carbon sequestration. In this study, based on the
regional scale in Northwest Arid Area (A case of Pingluo county), soil carbon sequestration
and rate were studied;The distribution characteristics of soil, and aggregates organic
carbon contents were studied by using the physical method of grouping, combined with
using XANES Spectroscopy to measure the distributions and chemical composition
stability characteristics of the main SOC functional groups; soil aggregates physical
protection of organic carbon and chemical stability mechanism were studied, which is to
provide the basis of more accurate estimate the potential of soil carbon sequestration and
carbon sequestration mechanisms.   The main results and conclusions were presented as
follows:
1. The spatial variability characteristics of topsoil bulk density:  
The results showed that the bulk density of farmland topsoil in Pingluo ranged from
1.079 to 1.612 g·cm -3 , with the mean of 1.355±0.107 g·cm -3 and with the variation
coefficient of 0.080. The topsoil bulk density is a weak variability and decreases gradually
from west to east, but shows the certain north-south zonal distribution pattern in Spatial
variability on county scale. Soil texture and land-use patterns are key factors, which affect
the variability of soil bulk density on county scale.  2. Soil organic carbon storage and sequestration rate:
From 1980 to 2011, soil organic carbon and organic carbon density in Pingluo (SOCD)
were significantly increased. In the last 31 years，organic carbon sequestration of farmland
topsoil increased 455,000 t; the increment of organic carbon per unit area is 6690.38 kg
C·ha -1 , the average rate of SOCD is 215.82 kg C·ha -1 ·yr -1 . Topsoil carbon sequestration
increased area rated 88.24 %, decreased   area rated 3.17%, with the relative balance of the
area accounted for 1.69%. In addition to sierozem, the carbon sequestration of other soil
types has increased, while irrigating warped soil, saline soil and aquatic soil had greatly
increased carbon sequestration. In terms of farmland soil factor, total nitrogen is one of the
principal factors influencing the organic carbon content, followed by total phosphorus,
total potassium; In terms of farmland management factors, the amount of root stubble is
one of the major factors chief factors affecting the rate of soil organic carbon change,
followed by nitrogen fertilizer inputs, the amount of retention stubble.
3. The characteristics of soil organic carbon fractions:
The content of total soil organic carbon in different soil types (the weighted mean
value in 100 cm) were as follows: saline soil (5.37±0.17 g/kg) > irrigating warped soil
(4.89±0.40 g/kg) > alluvial soil (4.06±0.55 g/kg). The content of topsoil organic carbon
were as follows: irrigating warped soil (8.49±0.49 g/kg) > saline soil (8.14±0.81 g/kg) >
alluvial soil (6.52±0.65 g/kg).
Under aerobic conditions, the content of heavy fraction organic carbon (HFOC, the
weighted mean value in 100 cm) expressed as follows: irrigating warped soil (5.12±0.65
g/kg) > saline soil (4.37±0.48 g/kg) > alluvial soil (3.29±0.34 g/kg); the content of
mineral-incorporated organic carbon (MOM) expressed as follows: irrigating warped soil
(4.40±0.56 g/kg) > saline soil (4.25±0.44 g/kg) > alluvial soil (3.12±0.14 g/kg); the content
of particulate organic matter (POC) expressed as follows: irrigating warped soil (1.08±
0.44 g/kg) > saline soil (0.98±0.41 g/kg)> alluvial soil (0.64±0.08 g/kg); the content of 
light fraction organic carbon (LFOC) expressed as follows: saline soil (0.87±0.18 g/kg) >
alluvial soil (0.46±12 g/kg)> irrigating warped soil (0.37±0.11 g/kg). In paddy fields, it
is the highest content of HFOC and MOM in alluvial soil, followed by saline soil,
irrigating warped soil. It is the highest content of LFOC and POC in irrigating warped soil,
followed by saline soil and alluvial soil. The contents of organic carbon fractions   under  aerobic conditions were higher than in paddy fields.
The content of soil organic carbon fractions (HFOC, MOM, POC) is highest in topsoil
of all the soil layers, with depth of profiles increasing showed a clear decreasing trend.
POC, MOM, HFOC and total organic carbon content showed a significant positive
correlation (P<0.01), while no significant relationship between LFOC and total organic
carbon content.
4. Distribution of organic carbon and soil aggregates:
1) The content of >0.25 mm water-stable aggregate is most highest in the topsoil with
the percentage of 63.81%, significantly higher than the parent material (36.15%);
aggregate destruction rate in topsoil is lowest with the percentage of 27.71%, while the
parent material layer is 46.28%. The average of irrigating warped soil aggregate
destruction rate is 32.27%, lower than the saline soil (44.36%) and alluvial soil (44.72%),
indicating that aggregate stability of irrigating warped soil is highest. Soil aggregate
stability of upland soil is higher than paddy soil, the content of >0.25 mm water-stable
aggregate in upland soil is 51.25%, which is higher than paddy soil (40.60%); the
aggregate destruction rate of upland soil is 37.60%,significantly lower than paddy soil
(43.30%). The content of >0.25 mm water-stable aggregates and soil organic carbon were
positively correlated, indicating that increasing of soil organic carbon content played an
important role in promoting the formation of aggregates.
2) Soil organic carbon are mainly fixed in the aggregates of >0.25 mm particle size.
The average content of >0.25 mm aggregate organic carbon in different soil types showed
that irrigating warped soil (8.35±0.08 g/kg) > saline soil (8.05±0.12 g/kg) > alluvial soil
(6.92±0.09 g/kg). The average content of >0.25 mm aggregate organic carbon in upland
soil is 8.13±0.08 g/kg, significantly higher than paddy (7.83 ± 0.42 g/kg).
3) The content of soil aggregate organic carbon fractions (HFOC, MOM, POC) fixed
in the aggregates of >0.25 mm particle size. The content of HFOC, MOM and POC in the
different size aggregate is significantly higher in irrigating warped soil and saline soil than
aquatic soil; the content of HFOC and POC in the different size aggregate is slightly higher
in upland soil than the paddy soils.
4) The stable organic carbon (HFOC, MOM) in >0.25 mm aggregate showed
significant positive correlation with aggregate organic carbon(P < 0.01).
iv
5. Characteristics of topsoi organic carbon functional gro  5. Characteristics of topsoi organic carbon functional groups:
With the aggregate particle size increases, in irrigating warped soil, the relative
percentage of organic carbon labile functional groups (carbonyl-C, O-alkyl-C) had
decreased, while the relative percentage of organic carbon stable functional groups
(aromatic-C) had increased. However, in saline soil, the relative percentage of organic
carbon stable functional groups (aromatic-C) had   decreased, the relative percentage of
organic carbon labile functional groups (carbonyl-C) had significantly increased.
Compared with the upland soil, paddy field could improve the chemical stability of soil
organic carbon.
Key Words：soil carbon sequestration rate, aggregates, organic carbon fractions, soil
organic carbon functional groups