December, 2011
Journal of Resources and Ecology
J. Resour. Ecol. 2011 2(4) 328-337
Vol.2 No.4
Article
DOI:10.3969/j.issn.1674-764x.2011.04.006
www.jorae.cn
Evaluation of Ecosystem Services Provided by 10 Typical Rice
Paddies in China
XIAO Yu*, AN Kai, XIE Gaodi and LU Chunxia
Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
Abstract: Based on reference review, this study investigated ecosystem services supported by 10 typical
rice paddies in six rice planting regions of China. The services were primary production, gas regulation,
nitrogen transformation, soil organic matter accumulation, and water regulation and flood control. The
results indicated that grain production of the 10 rice paddies was between 4.71 and 12.18 t ha-1 y-1; straw
production was 4.65 to 9.79 t ha-1 y-1; gas regulation was calculated to emit O2 ranging from 8.27 to 19.69
t ha-1 y-1 and to assimilate greenhouse gases ranging from -2.13 to 19.24 t ha-1 y-1 (in CO2 equivalent);
nitrogen transformation was estimated as nitrogen input ranging from 209.70 to 513.93 kg N ha-1 y-1 and
nitrogen output of 112.87 to 332.69 kg N ha-1 y-1; soil organic matter accumulation was calculated to be
between 0.69 and 4.88 t C ha-1 y-1; water regulation was estimated to consume water resources of 19875
m3 ha-1 y-1 and to support water resources of 6430 m3 ha-1 y-1; and flood control of several of the rice
paddies was calculated to be 1500 m3 ha-1 y-1. The integrated economic value of ecosystem services of
these rice paddies was estimated at USD 8605–21 405 ha-1 y-1, of which 74%–89% of the value can be
ascribed to ecosystem services outside primary production. The results also indicated that the integrated
economic value of the ecosystem services of the 10 rice paddies was higher when nitrogen fertilizer was
applied in the range of 275 to 297 kg N ha-1. Until now, the economic value of the rice paddy ecosystem
has been underestimated as only the economic value of grain and straw production was previously
calculated. As more and more forest land and grassland is lost to urban and industrial use, cropland
and especially rice paddies, will become more ecologically important to society. The economic value of
ecosystem services supplied by rice paddies, outside primary production, are worthy of increased research
attention.
Key words: rice paddy; ecosystem services; gas regulation; soil organic matter accumulation; nitrogen
transformation
1 Introduction
Rice paddies are the largest human controlled ecosystem.
They provide a number of ecosystem services such as
food production, nutrient cycling, soil protection, flood
control, gas regulation, pollination, aesthetic scenery and
provide habitat for birds, insects and soil organisms (Xiao
et al. 2005b; Pan et al. 2009; Köel-Knabner et al. 2010;
Verhoeven and Setter 2010; Yoshikawa et al. 2010; Zhang
et al. 2010a). At the same time, rice paddy ecosystems can
have adverse effects on the environment when there is an
excessive addition of chemical fertilizers and pesticides
and through greenhouse gases emissions (Knoblauch et al.
2010; Itoh et al. 2011).
According to FAOSTAT, 1.58×10 8 ha of rice was
planted globally in 2009, and the rice grain yield was
6.85×10 8 t, accounting for 28% of the world grain
production. In 2009, the rice grain yield in China was
1.95×108 t, which amounted to 40% of the total grain yield
in China (NBSC 2010). For most countries in Southeast
Asia rice is the most important food source. Further, rice
straw is the main fuel for many rural families and is an
important material for several industries (Ferng 2005; de
Fraiture et al. 2010; Godfray et al. 2010). During the rice
growth period, the rice plant assimilates CO2 and emits
O2 through photosynthesis, and emits CO2 and consumes
Received: 2011-06-27 Accepted: 2011-10-21
Foundation: Strategic Priority Research Program of the Chinese Academy of Sciences (XDA05050203); National Natural Science Foundation of China
(31140048, 30770410 and 31070384); Innovation Project of Institute of Geographic Sciences and Natural Resources Research, CAS (200905010).
* Corresponding author: XIAO Yu. Email: [email protected].
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XIAO Yu, et al.: Evaluation of Ecosystem Services Provided by 10 Typical Rice Paddies in China
O 2 through respiration. The rice paddy ecosystem has
received considerable attention as the main source of CH4
and N2O (Lee et al. 2010; Itoh et al. 2011). Bousquet et al.
(2006) indicated that CH4 emission from natural wetlands
and rice paddies accounted for 34% of the total CH 4
emissions globally. The IPCC (2007) estimated that N2O
emissions from agricultural sources amounted to 60% of
the global N2O emissions from anthropogenic sources, and
that N2O emissions from agricultural sources increased by
17% from 1990 to 2005. Rice paddy soil is one of the main
sources of N2O as paddy soil alternates between dry and
wet conditions with intermittent irrigation.
Nutrient transformation in the rice paddy improves soil
nutrient levels and enhances rice yield. Based on a long
term field experiment from 1986 to 2003, Tong et al. (2009)
found that the soil nitrogen content of rice paddy increased
5.2%–27.1% when NPK fertilizer was applied, compared
to farming practices without the application of fertilizer.
This occurred irrespective of the amount of manure
applied. However, over-use of fertilizer usually increases
nutrient loss through surface water and ground water from
drainage, leaching and NH3 volatilization, and this can
result in eutrophication and ground water nitrite pollution
(Köel-Knabner et al. 2010; Xiao et al. 2010). From field
experiments, Liang et al. (2007) found that the proportion
of nitrogen loss from rice paddy by NH3 volatilization,
drainage and leaching was 27.9%, 6.6% and 9.6% of total
nitrogen added, respectively.
Paddy soil organic matter increases following rice
cultivation. Based on a long term experiment Rui and
Zhang (2010) estimated that paddy soil organic matter
increased between 0.41 Mg ha-1 y-1 and 0.34 Mg ha-1 y-1
through straw abandonment and the application of manure.
Rice paddy ecosystems consume water through irrigation,
supplied surface water with drainage systems, and recharge
ground water after irrigation and precipitation. The
integration of rice paddies, ditches and ponds in rural areas
serve as a reservoir to control flooding. In Niigata, Japan,
Yoshikawa et al. (2010) simulated the flood mitigation
performance of paddy fields where runoff control devices
had been installed. The results showed that the main
channel discharge would have decreased by 26% and the
water level dropped by 0.17 m in the case of the largest
observed rainfall event.
There has been controversy around the outcomes of
intensive rice farming and rice paddy ecosystems. The
passive effects of intensive rice farming are things such
as environmental pollution and climate change. The
traditional rice paddy ecosystem is now seen to support
many fundamental and essential goods and services for
people. Thus, it is crucial to investigate the integrated
impacts of rice paddy ecosystems on human well-being.
Here, ecosystem services such as primary production, gas
regulation, nitrogen transformation, soil organic matter
accumulation and water regulation and flood control by
10 typical rice paddies across six rice planting regions of
China were examined. The impact of nitrogen fertilizer
application is also investigated.
N
Legend
Focal rice paddy
Provincial boundary
Rice planting region
Ⅰ
Ⅱ
Ⅲ
Ⅳ
Ⅴ
Ⅵ
Fig. 1 Distribution of 10 focal rice paddies in China. Different color represents the different rice planting areas in China.
I: DHRASC; II: DSHRACC; III: SDHRAPSC; IV: SHRANC; V: SEHRANC, and VI is SHRAARNC.
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Journal of Resources and Ecology Vol.2 No.4, 2011
2 Material and methods
2.1 Focal rice paddies
According to biophysical characteristics (temperature,
sunlight and location) and management practices (planting
system, application of fertilizer and water management),
rice planting in China is divided into six rice planting
regions (CNRRI 1988). They are the Double Harvest Rice
Area in South China (DHRASC), the Double and Single
Harvest Rice Area in Central China (DSHRACC), the
Single and Double Harvest Rice Area on the Plateau of
Southwest China (SDHRAPSC), the Single Harvest Rice
Area in North China (SHRANC), the Single Early Harvest
Rice Area in Northeast China (SEHRANC), and the
Single Harvest Rice Area in the Arid Region of Northwest
China (SHRAARNC) (Fig. 1). We selected 10 typical
rice paddies from these rice planting regions to examine
ecosystem services of rice paddies. They were located
at Guangzhou in Guangdong Province, Changshu in
Jiangsu Province, Chengdu in Sichuan Province, Taoyuan
in Hunan Province, Yingtan in Jiangxi Province, Bijie in
Guizhou Province, Fengqiu in Henan Province, Shenyang
in Liaoning Province, Hailun in Heilongjiang Pronvince,
and Lingwu in Ningxia Hui Autonomous Region (Table 1).
2.2 Method to estimate ecosystem services by rice
paddies and their economic values
2.2.1 Primary production
Primary product outputs from rice paddies include grain
and straw. The economic value of primary production is
estimated by the following equation:
Vpp=qs×ps+qst×pst
(1)
where Vpp is the economic value of primary production
of the rice paddy (USD ha-1 y-1); qs is the quantity of rice
grain (kg ha-1 y-1); ps is the price of rice grain (USD 0.28
kg-1 for early rice, USD 0.29 kg-1 for late rice, and USD
0.31 kg-1 for single rice) (DPNDRC 2010) (USD 1 = 6.831
CNY in 2009); qst is the quantity of rice straw (kg ha-1);
and pst is the price of rice straw (USD 0.01 kg-1) (DPNDRC
2010).
2.2.2 Gas regulation
In the rice paddy ecosystem, plants transform solar energy
into biotic energy through photosynthesis, fixing CO2 and
releasing O2. At the same time, plants and organisms in
the soil emit CO2 and consume atmospheric O2 through
respiration. In this study, O2 emission and the economic
value were estimated using the following equations (Xiao
et al. 2011):
Qo=1.19×mnpp−qso
(2)
Vo=Qo×po
(3)
where Qo is the quantity of O2 regulation of the rice paddy
(t ha-1 y-1); 1.19 is the coefficient of net primary production
to O 2 emission through photosynthesis; m npp is the net
primary production (t ha-1 y-1); qso is the O2 consumption by
organisms in the soil (t ha-1 y-1); Vo is the economic value
of O2 regulation of the rice paddy (USD ha-1 y-1); po is the
replacement price of O2 (USD 0.35 kg-1) (Wang 2010).
In addition to CO2 regulation rice paddy ecosystems
also emit or assimilate CH 4 and N 2O throughout the
growing season. Greenhouse gases regulation of the rice
paddies and the economic value were calculated by the
following equations:
Qg = (1.63×mnpp−qsc)−(24.5×qm+320×qne)/1000
(4)
Vg= Qg×pg
(5)
where Qg is the quantity of greenhouse gases regulation
of the rice paddy (t ha-1 y-1, in CO2 equivalent); 1.63 is the
coefficient of net primary production to CO2 assimilation
through photosynthesis; q sc is the CO 2 emission by
organisms in the soil (t ha -1 y -1 ); 24.5 is the GWP
coefficient of CH4 (Björklund et al. 1999); qm is the CH4
emission of the rice paddy (kg ha-1 y-1); 320 is the GWP
coefficient of N2O (Björklund et al. 1999); qne is the N2O
Table 1 Characteristics of focal rice paddies.
Rice planting Study site Temperature Rainfall
areas
(℃)
(mm)
DHRASC
Guangzhou
20.2
1875
DSHRACC
SDHRAPSC
SHRANC
Changshu
Chengdu
Taoyuan
15.5
17
16.5
1038
1050
1448
Yingtan
17.5
1600
13
13.9
7.5
1.5
8.6
1122
600
675
570
202
Bijie
Fengqiu
Shenyang
SEHRANC
Hailun
SHRAARNC Lingwu
Rice
seasons
Early
Late
Single
Single
Early
Late
Early
Late
Single
Single
Single
Single
Single
Growth stage
March to July
July to November
June to October
April to September
April to July
July to October
April to July
July to October
April to September
June to October
May to September
May to September
May to September
Fertilizer dose
(kg N ha-1)
220
183
173
218
121
168
120
120
135
428
187
150
300
Source
Yang et al. (1996); Li et al. (1998)
Xu et al. (1998); Wang et al. (2004)
Ren et al. (2002)
Li et al. (1997)
Liu et al. (1995); Xiong et al. (2003)
Yu (2002); Ye and Zhang ( 2002)
Cai et al. (1998); Xu et al. (2000)
Luo et al. (1999); Shi et al. (2003)
Han et al. (2003); Yue et al. (2003)
Zhang et al. (2010b); Yin et al. (2002)
XIAO Yu, et al.: Evaluation of Ecosystem Services Provided by 10 Typical Rice Paddies in China
emission of the rice paddy (kg ha-1 y-1); Vg is the economic
value of greenhouse gases regulation of the rice paddy
(USD ha-1 y-1); and pg is the cost of Sweden carbon tax
(USD 0.55 kg-1 CO2).
2.2.3 Nitrogen transformation
In our study, nitrogen transformation in the rice paddy
ecosystem refers to N transference between the rice
paddy ecosystem, the atmosphere, surface water, ground
water and human society (Xiao et al. 2005a). Nitrogen
transformation between the rice paddy ecosystem and
the atmosphere included biological N2 fixation, nitrogen
deposition, N2O emission and NH3 volatilization. Drainage
and irrigation were the methods of nitrogen transformation
between rice paddy ecosystem and surface water while
leaching and irrigation were the main methods of nitrogen
transformation between the rice paddy ecosystem and
ground water. Nitrogen transformation between human
society and the rice paddy ecosystem was through the
application of fertilizer, seedlings and harvesting.
Nitrogen inputs to the rice paddy and the economic
value were estimated by the following equations:
Qni=qf+qbf+qs+qr+qi
(6)
Vni=Qni×pn
(7)
where Q ni is the quantity of nitrogen input of the rice
paddy (kg ha-1 y-1 in pure N); qf is the nitrogen input by
application of fertilizer (kg ha-1 y-1 in pure N); qbf is the
nitrogen input by biological nitrogen fixation (kg ha-1 y-1 in
pure N); qs is the nitrogen input by seedlings (kg ha-1 y-1 in
pure N); qi is the nitrogen input by irrigation (kg ha-1 y-1 in
pure N); Vni is the economic value of nitrogen input by the
rice paddy (USD ha-1 y-1); and pn is the replacement price
of nitrogen (USD 0.62 kg-1 in pure N) (DPNDRC 2010).
Nitrogen output of the rice paddy and the economic
value were calculated with the following equations:
Qno=qsh+qth+qnv+qne+qd+ql
(8)
Vno=qsh×pp+qth×pn−( qnv+qd+ql)×pd−qne×320*pg
(9)
where Qno is the quantity of nitrogen output of the rice
paddy (kg ha-1 y-1 in pure N); qsh is the harvest nitrogen in
rice grain (kg ha-1 y-1 in pure N); qth is the harvest nitrogen
in rice straw (kg ha-1 y-1 in pure N); qnv is the nitrogen
loss by NH3 volatilization (kg ha-1 y-1 in pure N); qd is the
nitrogen loss by drainage (kg ha-1 y-1 in pure N); ql is the
nitrogen loss by leaching (kg ha-1 y-1 in pure N); Vno is the
economic value of nitrogen output of the rice paddy (USD
ha -1 y -1); p p is the replacement marginal price of grain
protein (USD 11.75 kg-1 in pure N; USWA 2009); pn is the
replacement price of nitrogen fertilizer (USD 0.62 kg-1 in
pure N) (DPNDRC 2010); and pd is the replacement cost
of nitrogen loss in drainage and leaching water and NH3
volatilization (USD 9.61 kg-1 y-1 in pure N in 2009 price)
331
(Turner et al. 1999).
2.2.4 Soil organic matter accumulation
In rice paddies organic matter input and output changes
soil organic matter (SOM) content. The methods of SOM
input included manure application, withered leaves,
ineffective tillers, roots, root exudation and abandoned
straw. In our study, only the roots, root exudation and
abandoned straw were calculated as the sources of SOM
increase. The methods of SOM output were CO2 and CH4
emissions. SOM accumulation and economic value were
estimated with the following equations:
Qsa=qfc+qas+qr+qre−qsc−qm
(10)
Vsa=Qsa×pom
(11)
where Qsa is the quantity of SOM accumulation of the
rice paddy soil (kg ha-1 y-1 in pure C); qfc is the organic
matter by manure application (kg ha-1 y-1 in pure C); qas
is the abandoned straw in the rice paddy (calculated as
11% of the total straw biomass) (kg ha-1 y-1 in pure C);
qr is the biomass of rice root (kg ha-1 y-1 in pure C); qre is
the biomass of rice root exudation (estimated as the four
times of the root biomass) (Watanabe and Roger 1985)
(kg ha-1 y-1 in pure C); Vsa is the economic value of SOM
accumulation of the rice paddy (USD ha-1 y-1); and pom is
the replacement price of SOM (USD 0.71 kg-1 in pure C).
2.2.5 Water regulation and flood control
Rice paddy irrigation consumes surface water and/or
ground water. Draining the rice paddy supplies surface
water and leaching recharges the ground water. Water
regulation of the rice paddy and the economic value were
calculated with the following equations:
Qwr= (vd+vl−vi)×10
(12)
Vwr=Qwr×pw
(13)
where Qwr is the quantity of water regulated of the rice
paddy (m3 ha-1 y-1); vd is the quantity of drainage water
(mm); vl is the quantity of leaching water (mm); vi is the
quantity of irrigation water (mm); Vwr is the economic
value of water regulation (USD ha-1 y-1); and pw is the price
of irrigation water (USD 0.01 m-3) (MWR 2010).
As one of the important types of wetlands in China,
rice paddies, with their ridges and rice plants, serve as
reservoirs that reduce flooding. The economic value of
flood control of the rice paddy was calculated with the
following equation:
Vwc=qwc×pwc×10
(14)
where Vwc is the economic value of flood control of the rice
paddy (USD ha-1 y-1); qwc is the quantity of flood control by
ridge of rice paddy (mm, calculated as 150 mm y-1); and
pmc is the replacement price of flood control (USD 0.25 m-3
in 2009 price) (Zhang and Gu 2004).
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Journal of Resources and Ecology Vol.2 No.4, 2011
2.3 Data compilation
From scientific literature published up until 2010, we
compiled data on grain yield, greenhouse gases emissions,
nitrogen transformation, soil organic matter and water
management of rice paddies in China. Data from the
CERN (Chinese Ecosystem Research Net) data center was
also collected. All data from the literature and CERN were
classified according to the six rice planting areas of China.
Based on data compilation, we estimated the economic
values of ecosystem services of 10 focal representative
rice paddies.
3 Results
3.1 Primary production
The grain yield per unit area of the 10 typical rice paddies
in China ranged from 4.71 to 12.18 t ha-1 y-1, and the straw
yield per unit area from 4.65 to 9.79 t ha-1 y-1. The grain
and straw yields per unit area of Taoyuan, Guangzhou and
Yingtan were relatively higher than others because of their
double rice planting systems, and those of Fengqiu, Hailun
and Bijie were much lower. Of the sites in the single rice
planting system, the grain yields in Changshu, Shenyang
and Lingwu were a little higher than others (Fig. 2a).
30
Grain
12
Gas regulation (t ha-1 y-1)
Primary production (t ha-1 y-1)
13
Straw
9
6
3
0
FQ
HL
BJ
CD
LW
SY
CS
YT
GZ
GHGs regulation
18
12
6
0
-6
TY
FQ
BJ
HL
600
SY
YT
LW
GZ
CS
TY
240
N input
520
N output (kg N ha-1 y-1)
N output
440
360
280
HL
BJ
Grain harvest
200
CS
SY
CD
YT
TY
LW
GZ
Straw harvest
160
NH3 volatilization
Leaching
120
Drainage
200
80
40
0
FQ
FQ
HL
(c) N input and output
(d) Main ways of N output
10
10
Water regulation and flood
control (×103m3 ha-1 y-1)
SOM output
SOM Balance
6
4
2
SY
HL
BJ
LW
CS
YT
CD
GZ
TY
0
-5
-10
LW
CS
BJ
CD
GZ
YT
(e) SOM accumulation
Fig. 2 Ecosystem services supported by 10 rice paddies.
TY
Water regulation
-15
Flood control
-20
-25
0
FQ
SY
5
SOM input
8
SOM accumulation
(×103 t ha-1 y-1)
CD
(b) Gas regulation
(a) Primary production
N transformation (kg N ha-1 y-1)
O2 regulation
24
LW
HL
YT
TY
(f) Water regulation and flood control
CD
CS
FQ
SY
BJ
GZ
XIAO Yu, et al.: Evaluation of Ecosystem Services Provided by 10 Typical Rice Paddies in China
3.2 Gas regulation
O2 regulation was between 8.27 and 19.69 t ha-1 y-1, and
greenhouse gases (GHGs) regulation ranged from –2.13
to 19.24 t ha-1 y-1 (in CO2 equivalent) (Fig. 2b). The O2
regulation of the rice paddy ecosystems in Taoyuan,
Changshu and Guangzhou was a little higher than the
others, while that in Fengqiu, Hailun and Chengdu was
relatively lower. The integrated regulation of GHGs by
the rice paddy in Yingtan was estimated to emit 2.13 t ha-1
y-1 (in CO2 equivalent) of GHGs (including CO2, CH4 and
N2O) into the atmosphere (Fig. 2b). Quantities of CO2
assimilation through photosynthesis and respiration were
similar in the double rice planting system in Guangzhou,
Taoyuan and Yingtan, but CH4 and N2O emissions from the
rice paddy in Yingtan were significantly higher because of
the application of fertilizer before seedling transplantation.
With enough soil organic matter input, CH4 emission from
paddy soil was accelerated, and the legume supported
reaction substrate and energy to soil denitrification which
improved N2O emission (Xiong et al. 2003).
3.3 Nitrogen transformation
Nitrogen input ranged from 209.70 to 513.93 kg N ha-1
y-1, and nitrogen output from 112.87 to 332.69 kg N ha-1
y-1 (Fig. 2c). Nitrogen input was mainly through the use
of fertilizer, which accounted for more than 60% of the
total nitrogen input. For the majority of rice paddies in this
study, the most important methods of nitrogen output were
grain and straw harvest, which amounted to 50%–77% of
the total nitrogen output. The proportion of nitrogen output
through NH3 volatilization was also high, amounting to
10%–34% of total output. The proportions of nitrogen
output through drainage and leaching were less than 10%
of the total output (Fig. 2d). However, there were several
exceptions. The proportion of nitrogen output through
NH 3 volatilization of total nitrogen output of the rice
paddy in Fengqiu was 54% because of a high soil pH of
8.6. Nitrogen output through leaching of the rice paddies
in Lingwu and Shenyang amounted to more than 20%
of total output. This was because there was no drainage
during the rice growth period, resulting in higher nitrogen
loss through leaching. The proportion of nitrogen output
through drainage to the total output in the rice paddies in
Bijie and Chengdu was more than 15% because of higher
volumes of drainage water.
In total, soil nitrogen was in surplus after one rice
growth season for most paddies, ranging from 1.90–253.15
kg N ha-1 y-1. It can be concluded that, even though we
did not consider nitrogen loss from NH 3 volatilization,
drainage, leaching and N2O, the application of nitrogen
fertilizer provided more nitrogen than was needed for
rice growth. The surplus nitrogen that accumulated in
the paddy soil may provide nutrients for the next growth
season. However, it could also be argued that surplus
333
nitrogen in the soil increased the risk of atmospheric
pollution and eutrophication because of higher nitrogen
loss from NH3 volatilization, drainage and leaching.
3.4 Soil organic matter accumulation
Soil organic matter (SOM) input was 1.83–7.70 t C ha-1 y-1,
and SOM output 1.11–3.17 t C ha-1 y-1 (Fig. 2e). Most of
SOM input was from root and root exudation, accounting
for 37%–91% of the total. The main mode of SOM output
was soil CO2 emission (not including CO2 emission from
root respiration), which amounted to more than 85% of the
total. The SOM surplus ranged from 0.69–4.88 t C ha-1 y-1.
The SOM surplus of the rice paddies in Taoyuan, Yingtan
and Guangzhou was much higher than others as they
had SOM input from rice root and root exudation from a
double rice planting system.
3.5 Water regulation and flood control
Water regulation ranged from -19 875–6430 m3 ha-1 y-1
(Fig. 2f). The rice paddies in Lingwu, Hailun, Yingtan
and Taoyuan were net consumers of water resources
as irrigation water use for these rice paddies was much
higher than water output by drainage and leaching. The
rice paddies in Guangzhou, Bijie and Shenyang supplied
surface water and recharged ground water as water
output by drainage and leaching was more than the water
consumed by irrigation. As there was no drainage water
in the rice paddies in Shenyang, Hailun and Lingwu, their
flood control function was not assessed. The ridges of the
other seven rice paddies served as the reservoir walls that
could contain flooding up to 15 cm, or 1500 m3 ha-1 y-1.
3.6 Economic values of ecosystem services by rice paddies
The integrated economic value per unit area of ecosystem
services for the 10 rice paddies was estimated at USD
8605–21 405 ha-1 y-1. The proportion of economic value
per unit area of gas regulation by the rice paddies to the
total ranged from 48% to 88%, and primary production
from 11% to 26% (Table 2). The nitrogen transformation
of rice paddies in Fengqiu, Lingwu and Chengdu and
water regulation of rice paddies in Lingwu and Hailun
caused economic losses. The integrated economic values
per unit area of ecosystem services of the rice paddies in
Guangzhou (DHRASC), Taoyun, Changshu and Chengdu
(DSHRACC), Shenyang and Hailun (SEHRANC), and
Lingwu (SHRAARNC) were higher than others. The
integrated economic values per unit area of ecosystem
services by rice paddies in Bijie (SDHRAPSC) and
Fengqiu (SHRANC) were a little lower. The rice biomass
and yield in Bijie and Fengqiu were less than other sites.
This was because paddy soil in Bijie and Fengqiu was
not suitable for rice planting, having lower nutrient and
organic matter content. To compensate for this more
chemical fertilizer was used to improve rice yield. This
resulted in higher N2O emissions and NH3 volatilization
334
Journal of Resources and Ecology Vol.2 No.4, 2011
Table 2 Integrated economic values per unit area of ecosystem services of 10 rice paddies in China (USD ha-1 y-1).
Sites
Guangzhou
Changshu
Chengdu
Taoyuan
Yingtan
Bijie
Fengqiu
Shenyang
Hailun
Lingwu
Primary production
Gas regulation
3013
2665
2219
3564
2556
2166
1484
2622
1810
2283
11 557
15 095
11 654
14 735
4610
5486
7532
14 353
13 687
16 719
Nitrogen
transformation
287
317
–71
264
58
497
–1498
381
632
–906
SOM accumulation Water regulation
2538
852
2063
3487
2509
1145
494
739
979
1213
444
387
385
367
359
414
387
32
-22
-204
Integrated
economic values
16 525
18 351
15 407
21 405
9677
8605
8657
17 002
16 338
18 878
Note: As values of grain and straw harvest in nitrogen transformation and primary production were recalculated, only the economic value of primary production
was calculated in the integrated value. As the economic value of N2O emission was also recalculated in gas regulation and nitrogen transformation, only the
economic value of N2O emission in gas regulation was calculated in the integrated value.
and led to lower integrated values per unit area of
ecosystem services.
4 Discussion
Until now only the economic value of primary production
(grain and straw) was calculated in the economic value
of rice paddies in the social-economic statistical system.
According to our study, the economic value per unit
area of primary production amounted to only 11% to
26% of the integrated economic value per unit area of
ecosystem services. The economic value per unit area of
gas regulation, nitrogen transformation, soil organic matter
accumulation and water regulation and flood control
accounted for 74% to 89% of the integrated value per
unit area. Based on field experiments and investigation,
Wang et al. (2010) estimated the economic value per
unit area of ecosystem services to be USD 10 807 ha-1 y-1
(USD 1 = 6.831 CNY in 2009). This included primary
production, social security, gas regulation, soil organic
matter accumulation and water conservation. According
to Wang et al. (2010) the economic value of ecosystem
services per unit area, not including the value of primary
production, accounted for 74% of the total value per unit
area. Qin et al. (2010) calculated economic value per
unit area of primary production, gas regulation, water
conservation, soil organic matter accumulation and
nutrient retention by the conventional rice paddy and riceduck paddy to be between USD 2236 and USD 2650 ha-1
y-1, in which economic value per unit area of ecosystem
services, not including the value of primary production,
amounted to 63% of the total economic value per unit area.
Lv et al. (2010) evaluated the environmental externalities
of the rice-wheat farming in Zhejiang Province, which
included GHGs regulation, non-point pollution, carbon
sequestration by crops, and soil and flood control. The
environmental externalities were estimated to be USD
2.28×109 y-1 in total and averaged USD 13 202 ha-1 y-1.
Even though the economic loss through GHGs emission
and non-point pollution was counted, the economic
value of environmental externalities of the rice-wheat
system in Zhengjiang was large. From this research it
is apparent that the economic value of rice paddies has
been underestimated and their importance to society not
taken into account. Furthermore, the economic values
of aesthetic scenery and the maintenance of biodiversity
were not calculated in the above studies because data was
unavailable. Therefore, the estimates of the economic
value of ecosystem services provided by rice paddies in
these studies were conservative. The economic value of
the ecosystem services of rice paddies was much higher
than we estimated.
Since the 1960’s increasing amounts of chemical
fertilizer have been used in agriculture in China. Chemical
fertilizer has been the most important way to enhance soil
fertility and grain yield. However, while increasing grain
yields, chemical fertilization has also resulted in severe
environmental problems, such as eutrophication and nitrite
pollution of ground water (Huang 2011).
According to our study, the integrated value per unit
area of ecosystem services increased with nitrogen
fertilizer dose, peaked at the fertilizer dose of 278 kg N
ha-1 with the average of USD 17 967 ha-1 y-1, and then
decreased with higher fertilizer doses. For different kinds
of ecosystem services, the economic value of primary
production peaked at the nitrogen fertilizer dose of 285 kg
N ha-1, gas regulation at 275 kg N ha-1, soil organic matter
accumulation at 297 kg N ha-1, and nitrogen transformation
obviously decreased with fertilizer dose (Fig. 3). The
economic value per unit area of ecosystem services was
relatively higher at a nitrogen fertilizer dose ranging from
275 to 297 kg N ha-1.
Based on field experiments Zhu (2006) suggested
that the integrated values of the social, economic and
environmental benefits of rice paddies in Changshu,
Jiangsu Province were optimal with a nitrogen fertilizer
dose of 218 kg N ha-1. However, most rice paddies were
335
XIAO Yu, et al.: Evaluation of Ecosystem Services Provided by 10 Typical Rice Paddies in China
Economic values of ecosystem
services (×103 USD ha-1 y-1)
Economic values of ecosystem
services (×103 USD ha-1 y-1)
4.0
3.2
2.4
1.6
y = -0.0393x2+22.397x−346.69
R2=0.3148
0.8
0.0
100
200
300
400
18
15
12
9
6
y = -0.1899x2+104.52x−970.61
R2=0.1448
3
0
500
100
200
Fertilizer doses (kg N ha )
500
5.0
1.0
0.5
0.0
-0.5
-1.0
y = -4.5522x+1144.5
R2=0.4697
-1.5
-2.0
100
200
300
400
500
Economic values of ecosystem
services (×103 USD ha-1 y-1)
Economic values of ecosystem
services (×103 USD ha-1 y-1)
400
(b) Gas regulation
(a) Primary production
y = -0.0686x2+40.812x−3691.6
R2=0.3939
4.0
3.0
2.0
1.0
0.0
100
200
Fertilizer doses (kg N ha-1)
300
400
500
Fertilizer doses (kg N ha-1)
(c) Nitrogen transformation
(d) SOM accumulation
25
Economic values of ecosystem
services (×103 USD ha-1 y-1)
0.6
Economic values of ecosystem
services (×103 USD ha-1 y-1)
300
Fertilizer doses (kg N ha-1)
-1
0.4
0.2
y = 0.0068x2−3.3852x+612.46
R2=0.1023
0.0
-0.2
-0.4
100
200
300
400
500
20
15
10
y = -0.2892x2+160.86x−4395.3
R2=0.291
5
0
100
Fertilizer doses (kg N ha )
(e) Water regulation
200
300
400
500
Fertilizer doses (kg N ha-1)
-1
(f) Integrated value of ES
Fig. 3 Relationship between economic values per unit area of ecosystem services produced by 10 rice paddies in China and
fertilizer dose.
applying nitrogen fertilizer at 300 kg N ha-1. The nitrogen
loss from rice paddies at this level of fertilizer application
was 45 kg N ha-1 more than the loss that would occur
with the suggested optimal fertilizer application rate
of Zhu. With field experiments and Coase principle in
environmental economics, Huang et al. (2007) found that
ecological and economic benefits of rice paddies in Taihu
Lake area would be optimal with nitrogen fertilization
ranging from 219 to 255 kg N ha-1; higher rates of nitrogen
fertilizer application would result in serious environmental
problems.
Therefore, nitrogen application has important impacts
on ecosystem services provided by rice paddies. The
economic value per unit area of ecosystem services by
rice paddies would peak at a specific nitrogen fertilizer
dose. For this study, the appropriate nitrogen fertilizer
application range was based on an ecosystem services
valuation of rice paddies with conventional nitrogen
application in different rice planting areas. The results
indicate that nitrogen fertilizer was over-used in most of
the rice paddies in China, and the efficient use of nitrogen
fertilizer was very low (Li 2009; Huang 2011). If the
efficiency of nitrogen use of rice paddies increased, the
appropriate range for nitrogen fertilizer application would
change.
336
5 Conclusions
We estimated the economic value of ecosystem services
of 10 typical rice paddies across six rice planting regions
in China. These services comprised primary production,
gas regulation, nitrogen transformation, soil organic matter
accumulation, and water regulation and flood control.
Our results indicated that the integrated economic value
per unit area of ecosystem services of the 10 rice paddies
ranged from USD 8605–21 405 ha -1 y-1. The economic
value per unit area of ecosystem services, not including
the value of primary production, accounted for 74%–89%
of the integrated value per unit area. The integrated value
per unit area of ecosystem services increased with nitrogen
fertilizer dose, peaked at fertilizer use of 275–297 kg N ha-1,
and decreased at higher application rates.
It appears that the economic value of rice paddies has
been underestimated as the economic value of primary
production was the only input used when calculating
the economic value of the rice paddy. This neglected the
economic value of gas regulation, nitrogen transformation,
soil organic matter accumulation and flood control.
As more and more forest land and grassland has been
converted into urban and industrial use, cropland,
especially rice paddies, will become more ecologically
important to society. Apart from primary production,
the economic value of ecosystem services such as gas
regulation, soil organic matter accumulation, water
regulation, and biodiversity maintenance is worthy of
considerably more research attention.
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中国10类典型稻田生态系统服务评价
肖 玉，安 凯，谢高地，鲁春霞
中国科学院地理科学与资源研究所，北京 100101
摘要：在公开发表数据基础上，本研究评价了全国6大稻作区10类稻田提供的生态系统服务。研究的服务包括稻田初级产品
生产、气体调节、氮素转化、土壤有机质累积以及水调节和洪水控制等5项生态系统服务。研究结果显示，稻田谷物产量为4.71–
12.18 t ha-1 y-1，稻草为4.65–9.79 t ha-1 y-1；O2调节量为8.27–19.69 t ha-1 y-1，温室气体调节量为-­2.13–19.24 t ha-1 y-1 (CO2 当量)；
氮素输入量为209.70–513.93 kg N ha-1 y-1，输出量为112.87–332.69 kg N ha-1 y-1；土壤有机质库变化为0.69–4.88 t C ha-1 y-1；水调
节量为-19 875–6430 m3 ha-1 y-1，洪水控制量为1500 m3 ha-1 y-1。研究结果还显示，10类稻田的生态系统服务价值为8605–21 405 美
元 ha-1 y-1，除了初级产品生产以外的其他生态系统服务价值仅占74%–89%。在施氮量为275–297 kg N ha-1时，稻田生态系统服务
价值相对较高。目前仅以农产品生产来计算稻田生态系统的价值显著低估了稻田生态系统对人类社会的重要性。随着越来越多的
森林、草地等转为城市和工业用途，农田特别是稻田生态系统将具有越来越高的生态重要性。农田生态系统农产品生产以外的生
态系统服务将受到越来越多的关注。­
关键词：稻田；生态系统服务；气体调节；土壤有机质累积；氮素转化