Terrestrial organic carbon storage modes based on relationship between soil and lake carbon, China

Journal of Environmental Management 250 (2019) 109483

Contents lists available at ScienceDirect

Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman

Research article

Terrestrial organic carbon storage modes based on relationship between soil and lake carbon, China

T

Lingmei Xu, Yu Li∗, Wangting Ye, Xinzhong Zhang Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Center for Hydrologic Cycle and Water Resources in Arid Region, Lanzhou University, China

A R T I C LE I N FO

A B S T R A C T

Keywords: Terrestrial ecosystems Carbon sinks Carbon storage modes Carbon sequestration Climate change

Terrestrial ecosystems have received considerable attention as a significant sink for organic carbon at regional to global scales. Previous studies were focused on assessment and quantification of carbon sinks for one ecotype, and few have worked on the interconnection of terrestrial sinks. In this paper, we synthesized the data from China's second national soil survey and direct measurements from 54 lakes. Meanwhile, we investigated the controlling factors of carbon accumulation dynamics in soils and lakes. Results showed varied spatial distribution of soil and lake organic carbon in different regions, and three storage modes were found. The storage mode of watershed collection was observed in the region of the Qinghai-Tibetan Plateau, while the northeast China and Yunnan-Guizhou Plateau revealed another storage mode of autochthonous deposition, and the mode of human activities affection was represented by the East Plain and Mongolia-Xinjiang Plateau. The spatial difference throughout China was regulated by various climate patterns, geological conditions and anthropogenic interference. Our results provide insights into carbon storage modes in various regions, and also inform strategies for enhancing global carbon sequestration and future mitigation policies towards global climate change.

1. Introduction Increased concern about global climate change has spurred greater attention to increasing carbon sinks as a means of removing greenhouse-gas from the atmosphere (Gruber et al., 2019; Yvondurocher et al., 2017; Marcott et al., 2014; Kaplan, 2015; Lubowski et al., 2005). Soils and lakes as important components of terrestrial ecosystem are considered to play an important role in the global carbon cycle (Montañez et al., 2016; Doetterl et al., 2015; Wang et al., 2015; Raymond et al., 2013). They mineralize a large amount of organic carbon produced in situ or transported from other regions into CO2, N2O and CH4 by heterotrophic microorganisms (Guenet et al., 2018; Doetterl et al., 2015; Wang et al., 2015; Kastowski et al., 2011). It is estimated that approximately 5–20 percent CO2, 15–30 percent CH4, as well as 80–90 percent N2O in the atmosphere are released from soils every year (Liu et al., 2014). Meanwhile, lakes are estimated to account for about 0.07–0.15 Pg C year−1 of CO2 flux and 103 Tg CH4 emissions globally (Mendonça et al., 2017; Wang et al., 2015; Raymond et al., 2013; Sobek et al., 2005). Therefore, management of both soil and lake carbon pools can help reduce atmospheric concentrations of greenhouse gases (Jordon et al., 2019; Doetterl et al., 2015; Yu et al., 2007; Lal, 2004).

∗

Soil organic carbon storage worldwide at l m depth is estimated to be ~1100–1700 Pg C with a mean of ~1500 Pg C, twice the value in either living vegetation or atmospheric carbon (Guenet et al., 2018; Scharlemann et al., 2014; Yu et al., 2007; Eswaran et al., 1993). Global lakes are estimated to store about 23–120 Pg carbon, despite only covering ~2% of the world's surface area (Wang et al., 2015; Kastowski et al., 2011; Kortelainen et al., 2004). While previous studies have focused on estimating the total amount of carbon burial for one ecotype, the interaction between terrestrial soil and lake carbon storage has received little attention. Conventional understanding indicates that lake carbon stock is closely related to soil carbon storage, because considerable soil organic matter usually responds to abundant exogenous carbon deliveries to lakes. But recent advances suggest that regional lake carbon accumulation has different responses than soil carbon sequestration (Wang et al., 2015; Zhang et al., 2013; Zheng et al., 2011; Wu et al., 2003). For a more thorough understanding the roles of soils and lakes in regional carbon cycling, the relationship between terrestrial soil and lake carbon storage needs investigation. Soils and lakes in China distribute through all the climatic zones including tropic, temperate and frigid zones with a significant elevation change from east to west (Wang et al., 2015; Shen, 2013; Wu et al., 2003; NSSO, 1998; Wang and Dou, 1998). Therefore, China is an

Corresponding author. E-mail address: [email protected] (Y. Li).

https://doi.org/10.1016/j.jenvman.2019.109483 Received 16 February 2019; Received in revised form 22 August 2019; Accepted 26 August 2019 0301-4797/ © 2019 Elsevier Ltd. All rights reserved.

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

Fig. 1. Overview map showing study region, soil profiles and lake sites in China.

used to calculate sediment accumulation rate in individual lakes. The total area of China's lakes was estimated to ~9.10 million ha (Wang and Dou, 1998). Other data used include: quality-controlled global Digital Elevation Model (DEM) at 1 km × 1 km from the National Oceanic and Atmospheric Administration, 0.5° × 0.5° monthly gridded precipitation and temperature datasets from 1961 to 2013 at meteorological stations released by the National Meteorological Information Center, spatial distribution of yearly normal differential vegetation index (NDVI) in China produced by Resource and Environment Data Cloud Platform (Xu, 2018), as well as WESTDC Land Cover Products 2.0 at 1 km × 1 km derived from Environmental and Ecological Science Data Center for West China (Ran and Li, 2006).

appropriate area to explore terrestrial soil and lake carbon storage mechanisms in a range of ecosystems with different climates and geologies. In this study, we synthesized the data of China's second national soil survey and records from 54 lakes to (1) evaluate the factors controlling the spatial patterns of soil and lake carbon storage, (2) explore the terrestrial organic carbon storage modes based on relationship between soil and lake carbon, and (3) outline soil and lake management options to reduce the enrichment of atmospheric CO2. 2. Materials and methods 2.1. Study regions This paper divided mainland China into the Qinghai-Tibetan Plateau (TP), northeast China (NEC), East Plain (EP), Yunnan-Guizhou Plateau (YG) and Mongolia-Xinjiang Plateau (MX), based on physiography and regional climatic characteristics (Wang et al., 2015; Shen, 2013; Duan et al., 2008; Wang and Dou, 1998) (Fig. 1). EP, situated in the subtropical zone, is the warmest and wettest region of China, followed by YG (Wang et al., 2015). TP is high in elevation with a prevailing cold climate, while MX experiences dry conditions due to the barrier effect of the Tibetan Plateau and the long distance from the ocean (Chen et al., 2008; Wu et al., 2003). Processes involved in the formation and evolution of both soils and lakes are greatly varied between these regions (Wang et al., 2015; Shen, 2013).

2.3. Estimate of soil organic carbon storage Soil organic carbon density (SOCD, kg C m−2) of each profile was calculated using the following equation: n

SOCD =

∑ 0.58 × Ti × ρi × OMi × (1 − Ci)/10 i=1

(1)

where n represents the number of soil profile layers, 0.58 is the Bemmelen index, Ti , ρi , OMi and Ci are thickness (cm), bulk density (g cm−3), organic matter content (%) and volumetric percentage of the fraction > 2 mm (%) in the layer i , respectively. Only a part of soil profile had bulk density data. We established empirical relationships between soil bulk density and organic carbon content based on coincident, parallel measurements of 1249 samples (Wu et al., 2003). The data showed two regression patterns: Pattern I was suitable for samples with high OC content (> 6%) and Pattern II was suitable for samples with low OC content (≤6%) (Appendix A; Fig. A1). The rock fragment volume (Ci ) for soil sections without measured value was obtained using mean value of the same subgroups (Wu et al., 2003). Soil organic carbon storage (SOCS, Pg C) was then obtained by

2.2. Data materials Soil data used in this study were collected from soil profiles of the second national soil survey during 1980–1996 (Pan and Shi, 2015). Among those, 2444 profiles were considered representative of soils in different regions of China (Fig. 1a). Soil profile depth involved in this study for calculation was fixed as 1 m, and for profiles that were less than 1 m, data of the unobserved portion were estimated by the statistics derived from same soil groups (Yu et al., 2007; Sun, 2003). The soil classification was referred from Chinese soil taxonomy (NSSO, 1998) which was generally used in the soil survey (Table 1). Excluding rocky mountain regions and water, glacial and permanent snow-covered areas, the considered soil surface area in this study amounted to ~881.81 million ha (Wu et al., 2003; NSSO, 1998). Lake records in this paper were chosen from available published sources across China based on two criteria: (1) the record must have reliable chronologies and continuous sedimentary sequences; and (2) the record length should be at least 1 m without documented depositional hiatuses. Fifty-four lakes from different regions of China were selected for this study (Fig. 1b, Table 2). All radiocarbon ages (14C yr BP) were calibrated to calendar years (Cal yr BP) using the software of Calib 6.1.0 (Stuiver and Reimer, 1993) and the calibrated ages were

n

SOCS =

∑ Ai

× SOCDi

i=1

(2)

where n is the number of soil subgroups. Ai and SOCDi represent surface area and organic carbon density of soil subgroup i , respectively. 2.4. Estimate of lake organic carbon storage Organic carbon accumulation rate (CAR, g C m−2 year−1) in each lake was gathered using the following equation (Alin and Johnson, 2007; Müller et al., 2005):

CAR = SAR × OC (%) × ρ × (1 − ϕ) 2

(3)

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

Table 1 (continued)

Table 1 Organic carbon content, density and storage of soil groups in China. Soil group in Chinese soil taxonomy

Number of soil profiles

Area (million ha)

Mean SOC (%)

SOC density (kg C m−2)

Total SOC Storage (Pg C)

Humid-thermo ferralitic Lateritic red earths Red earths Yellow earths Yellow-brown earths Yellow-cinnamon soils Brown earths Dark-brown earths Brown coniferous forest soils Albic soils Podzolic soils Cinnamon soil Gray forest soils Torrid red soils Gray-cinnamon soils Black soils Chernozems Castanozems Castano-cinnamon soils Dark loessial soils Brown pedocals Sierozems Gray desert soils Gray-brown desrt soils Brown desert soils Takyr Aeolian soils Red primitive soils Alluvial soils Limestone soils Volcanic soils Purplish soils Lithosoils Phospho-calcic soils Skeletol soils Loessial soil Meadow soils Shruby meadow soils Fluvo-aquic soils Mountain meadow soils Lime concretion black soils Bog soils Peat soils Coastal solonchaks Acid sulphate soils Meadow solonchaks Frigid plateau solonchaks Desert solonchaks Solonetzs Paddy soils Cumulated irrigated soils Irrigated desert soils Felty soils Dark felty soils Cold calcic soils Frigid desert soils

23

4.27

0.58

10.20

0.44

31 130 76 35

18.13 57.85 23.93 18.42

0.56 0.52 0.85 0.85

10.55 8.42 10.22 11.19

1.91 4.87 2.45 2.06

23

3.81

0.28

5.69

0.22

88 64 9

20.16 40.11 11.66

0.68 1.45 2.30

7.48 13.75 18.41

1.51 5.52 2.15

20 1 133 8 16 19

5.27 0.00 25.17 3.15 0.69 6.18

0.70 4.75 0.41 1.20 0.39 1.85

10.67 46.83 6.91 9.82 6.03 17.50

0.56 0.00 1.74 0.31 0.04 1.08

36 69 68 17

7.36 13.22 37.50 4.82

0.89 0.92 0.55 0.27

12.39 11.98 8.32 5.42

0.91 1.58 3.12 0.26

18 15 33 11 10

2.55 26.56 5.38 4.60 30.73

0.42 0.33 0.29 0.23 0.21

9.78 4.18 4.84 3.64 2.68

0.25 1.11 0.26 0.17 0.82

8 2 38 28 45 48 12 80 3 2

24.30 0.68 67.57 2.28 4.29 10.77 0.19 18.90 18.53 0.00

0.17 0.06 0.13 0.81 0.68 1.20 1.50 0.48 0.16 0.70

2.57 0.88 2.08 9.72 6.25 10.19 13.74 5.07 1.81 11.96

0.62 0.01 1.41 0.22 0.27 1.10 0.03 0.96 0.33 0.00

51 36 86 2

26.11 12.29 25.09 2.48

0.78 0.22 0.82 0.33

4.38 4.73 9.69 4.86

1.14 0.58 2.43 0.12

224 20

25.68 4.22

0.33 5.23

5.24 18.95

1.35 0.80

25

3.77

0.71

7.01

0.26

38 4 22 4 28

12.62 1.47 2.12 0.02 10.44

4.02 14.70 0.40 1.18 0.23

26.12 99.43 6.97 20.94 3.80

3.30 1.46 0.15 0.00 0.40

4

0.69

0.29

3.68

0.03

5 21 525 24

2.87 0.87 30.68 1.52

0.30 0.24 0.69 0.47

4.61 3.83 9.76 8.12

0.13 0.03 2.99 0.12

Soil group in Chinese soil taxonomy

Number of soil profiles

Area (million ha)

Mean SOC (%)

SOC density (kg C m−2)

Total SOC Storage (Pg C)

Cold desert soils Frigid frozen soils Frigid calcic soils Cold brown calcic soils Total

2 4 6 14

5.22 30.65 68.85 0.96

0.38 1.90 0.44 0.62

1.81 12.58 5.31 7.25

0.09 3.85 3.66 0.07

2444

881.81

Lake sediment accumulation rate (SAR, mm year−1) was typically established using dated depths of the sediment profiles (Wang et al., 2015), and organic carbon content (OC, %) was directly derived from 54 lake sediment records. Sediment density (ρ) and porosity (ϕ) could be calculated using Eq. (4) (Alin and Johnson, 2007) and Eq. (5) (Avnimelech et al., 2001; Danielson and Sutherland, 1986).

ρ = 2.65 − 0.0523 × OC (%)

0.91

0.53

8.95

0.08

20 21 14 5

53.54 19.44 11.29 8.96

2.57 2.07 0.73 0.30

13.78 13.58 8.07 3.01

7.38 2.64 0.91 0.27

(4)

DBD ⎞ ϕ = ⎜⎛1 − ⎟ × 100% ρ ⎠ ⎝

(5) −3

Dry bulk density (DBD, g cm ) for lake sediments without measured value was then obtained using the empirical relationships (Wang et al., 2015; Kastowski et al., 2011; Avnimelech et al., 2001; Dean and Gorham, 1998).

DBD = 1.665 × (OC )−0.887 (OC > 6%)

(6)

DBD = 1.776 − 0.363 × ln(10 × OC ) (OC ≤ 6%)

(7)

Eq. (6) was given by Dean and Gorham (1998), and Eq. (7) was reported by Avnimelech et al. (2001). Lake organic carbon storage (LOCS, Pg C) was computed by following equation: n

LOCS =

∑ Ai

× ti × CARi

i=1

(8)

where n is the number of regions. Ai , ti and CARi represent surface area, basal date at 1 m depth, and carbon accumulation rate of region i , respectively. 2.5. Evaluation of the factors controlling organic carbon sequestration Pearson's correlation analysis was applied to explore the influence of topographical, climatic, vegetational or anthropic factors on SOC density in different regions of China (Appendix A; Table A1). Altitude, aspect, slope and relief degree of land surface were extracted from the global DEM at 1 km × 1 km. Temperature, summer temperature, precipitation and summer precipitation data were calculated based on a series of monthly gridded precipitation and temperature datasets. Normal differential vegetation index was calculated from a dataset of spatial distribution of yearly NDVI in China (Xu, 2018). Land-use comprehensive index was obtained from the WESTDC Land Cover Products 2.0 dataset (Ran and Li, 2006), and the computational formula was: n

La = 100 ×

∑ Ai i=1

20

72.53

× Ci La ∈ [100, 400]

(9)

The model was reported by Zhuang and Liu (1997) (Appendix A; Table A2). La represents land-use degree comprehensive index, Ai is classification values of land use degree i , and Ci is area percentage of land use degree i . We carried out regression analysis between lake CAR and environmental variations or lake characteristics. Summer temperature and 3

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

3. Results

Table 2 Organic carbon content, sediment and carbon accumulation rates of lake records at a depth of 1 m in China. ID

Region

1 2 3 4 5 6 7 8 9 10 11 12 13

TP TP TP TP TP TP TP TP TP TP TP TP TP

14 15 16 17 18 19

TP TP TP TP TP NEC

20 21

NEC NEC

22 23 24

NEC NEC EP

25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Mean

EP EP EP EP EP EP EP YG YG YG YG YG MX MX MX MX MX MX MX MX MX MX MX MX MX MX MX MX MX MX

Site

Bangong Co Songxi Co Naleng Lake Chen Co Nam Co Zigetang Co Ngoin Co Paru Co Pumoyum Co Koucha Lake Ximen Co Qinghai Lake Donggi Cona Lake Gahai Lake Chaka Salt Lake Genggahai Lake Hala Lake cuo'e Lake Erlongwan Maar Lake Xingkai Lake Sihailongwan Maar Lake Moon Lake Dabusu Lake Huguangyan Maar Lake Dajiuhu Lake Jiangling Dahu Lake Chaohu Lake Tai Lake Longgan Lake Sanqing Chi Erhai Lake Dian Chi Xima Chi Xingyun Lake Lugu Lake Bosten Lake Aibi Lake Yitang Lake Balikun Lake Wulungu Lake Zhuye Lake Juyanze Lake Huahai Lake Yan Chi Sanjiaocheng Daihai Lake Dali Lake Gonghai Lake Hulun Lake Bojianghaizi Tengger Nuur Yanhaizi Lake Wulagai Lake

Mean OC (%)

Mean SAR (mm year−1)

Mean CAR (g C m−2 year−1)

Basal date (Cal yr BP)

2.64 0.29 9.01 9.14 0.42 1.42 2.21 31.50 1.13 14.76 9.82 1.26 1.17

1.23 0.28 0.70 1.38 0.49 0.82 0.67 0.28 0.27 0.50 0.21 0.44 0.25

20.26 1.09 14.94 29.47 1.02 9.58 9.93 6.79 2.78 11.85 4.54 5.07 2.59

3917 3400 1200 1420 2130 800 2375 2250 6828 1350 2445 2465 3632

1.78 0.07 1.94 13.20 2.14 2.36

1.47 3.54 0.97 0.67 0.07 0.49

19.52 4.75 14.00 12.29 1.05 7.38

5960 377 1905 4278 2250 1450

0.51 10.13

0.07 0.08

0.41 4.62

13796 1714

15.02 8.30 1.88

0.51 0.93 0.64

11.84 19.92 8.77

1336 1070 545

41.06 0.59 48.76 0.83 0.72 1.26 1.19 2.64 2.35 4.67 0.58 9.98 4.49 0.52 0.53 1.84 0.60 0.28 1.51 0.44 0.57 1.87 0.68 4.35 9.51 1.11 9.74 1.49 0.24 0.90 5.51

0.26 2.21 0.12 1.50 0.35 2.01 0.10 0.36 0.47 0.12 0.46 0.39 1.04 0.49 1.03 0.28 0.38 1.88 1.34 0.26 0.12 0.89 1.99 2.39 2.04 1.51 0.20 0.27 1.18 0.05 0.79

6.78 15.13 4.42 12.80 1.56 22.04 23.73 8.07 7.10 2.21 3.19 8.57 19.16 3.06 6.60 3.95 2.64 7.66 16.25 1.46 0.80 12.90 14.81 42.70 46.39 16.41 4.36 3.17 4.12 0.30 10.13

3502 1142 6537 6952 7207 2266 5581 2139 2434 7728 2150 2355 1428 4362 1828 4484 2859 447 2141 4047 17250 2954 1179 503 529 3511 7020 3227 846 19106 3641

3.1. Soil organic carbon content and density Soil organic carbon content, density and storage of all soil groups in China are displayed in Table 1. SOC content ranges from 0.06% (Takyr) to 14.70% (Peat soils), with a mean value of 1.33%. SOC density ranges from 0.88 (Takyr) to 99.43 kg C m−2 (Peat soils), with a mean value of 8.80 kg C m−2. SOC storage ranges from 0.00 (Podzolic soils, Phosphocalcic soils, Acid sulphate soils) to 7.38 Pg C (Felty soils), with a total value of 72.53 Pg C. Spatial distribution patterns of SOC content and density across China are calculated based on the geographic coordinates of the 2444 soil profiles mentioned above (Figs. 1a and 2b, Table 3). SOC content and density are highest in the forest soils of YG, around 1.27%, 10.55 kg C m−2. The lowest SOC content (0.56%) and density (7.49 kg C m−2) are observed in the desert soils of the MX region (Table 3). Overall, SOC content and density increase from west to east in northern China, and decrease from north to south in eastern China. 3.2. Lake organic carbon content, sediment and carbon accumulation rates Organic carbon content, sediment and carbon accumulation rates for each lake of China are showed in Table 2. Sediment OC content of China's lakes ranges from 0.07 (Chaka Salt Lake) to 48.76% (Dahu Lake), with a mean value of 5.51%. Lake sediment accumulation rates range from 0.05 (Wulagai Lake) to 3.54 mm year−1 (Chaka Salt Lake), with a mean value of 0.79 mm year−1. Lake carbon accumulation rates range from 0.30 (Wulagai Lake) to 46.39 g C m−2 year−1 (Gonghai Lake), with a mean value of 10.13 g C m−2 year−1. The carbon storage in lakes of China is estimated at 3.37 Pg C, suggesting lake organic carbon has five percent the storage capacity as soil (Table 3). Fig. 2a shows spatial variation patterns of lake organic carbon content, sediment and carbon accumulation rate in the different regions of China. The observed peak of the sediment OC content is 12.04% in EP, three and six times higher than the average content of YG (4.05%) and MX (2.26%) (Table 3). The average sediment and carbon accumulation rates differ significantly among the regions: 0.79 mm year−1, 9.53 g C m−2 year−1 in TP; 0.42 mm year−1, 8.84 g C m−2 year−1 in NEC; 0.90 mm year−1, 11.90 g C m−2 year−1 in EP; 0.36 mm year−1, 5.83 g C m−2 year−1 in YG; and 0.96 mm year−1, 11.49 g C m−2 year−1 in MX (Fig. 2a, Table 3). 3.3. Relationship between soil and lake carbon accumulation Organic carbon storage modes based on the relationship between soil and lake carbon are investigated. The results indicate three storage modes for soil and lake organic carbon in different areas of China. The storage mode of watershed collection characterized by high soil organic carbon density and high lake carbon accumulation rate, is observed in region of TP. While NEC and YG reveal another storage mode of autochthonous deposition, with relatively high soil organic carbon density and low lake carbon accumulation rate. Finally, the storage mode of human activities affection shows low soil organic carbon density and high lake carbon accumulation rate, represented by the EP and MX region.

summer precipitation were calculated according to datasets of 0.5° × 0.5° monthly gridded precipitation and temperature during 1961–2013. Altitude, annual evaporation, annual precipitation, annual temperature, and mean depth, max depth, surface areas and catchment area of lakes were partly from Wang et al. (2015) and partly from other available publications (Appendix A; Table A3).

3.4. Soil and lake carbon storage and influences factors Soil organic carbon density in China is significantly correlated to altitude, relief degree of land surface, temperature, precipitation, summer temperature and summer precipitation (Appendix A; Table A1). Regionally, SOC density in TP shows significant correlation with slope, relief degree of land surface, summer precipitation and NDVI. SOC density in NEC is significantly correlated to temperature and summer temperature. In EP region, SOC density indicates significantly 4

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

Fig. 2. Regional difference in (a) organic carbon content, sediment and carbon accumulation rates of lakes, and (b) soil organic carbon content and density in China.

Table 3 Organic carbon distribution and storage in soil and lake for various regions of China. Region

TP NEC EP YG MX Total

Soil data

Lake data

Soil area (million ha)

Number of soil profiles

SOC (%)

SOC density (kg C m−2)

Total OC storage (Pg C)

Lake area (million ha)

SAR (mm year−1)

OC (%)

CAR (g C m−2 year−1)

Total OC storage (Pg C)

/ / / / / 88.81

207 359 1075 306 497

1.26 0.94 0.57 1.27 0.56

10.53 9.76 8.24 10.55 7.49

/ / / / / 72.53

4.5 0.4 2.12 0.12 1.97 9.1

0.79 0.42 0.9 0.36 0.96

5.77 7.26 12.04 4.05 2.26

9.53 8.84 11.9 5.83 11.49

1.17 0.14 1.06 0.02 0.98 3.37

4. Discussion

correlated to altitude, relief degree of land surface, temperature and summer precipitation. In YG region, SOC density has significant correlation with altitude, slope, relief degree of land surface, temperature, summer temperature, land-use degree comprehensive index and summer precipitation. In MX region, SOC density shows significant correlation with altitude, slope, relief degree of land surface, temperature, precipitation, summer temperature, summer precipitation and NDVI. The average CAR of overall lakes in China is not significantly related to the environmental variables or lake characteristics. However, the correlation between CAR and the influences factors varies among regions (Fig. a2). The average CAR of lakes in TP is negatively correlated with altitude, water mean depth and water maximum depth. The mean CAR of lakes in NEC has negative correlations with precipitation, maximum water depth and ratio of catchment area to lake area. In EP region, lake CAR shows positive correlations with mean depth and ratio of catchment area to lake area, negative correlations with temperature and summer temperature. In YG region, lake CAR indicates positive correlations with mean depth and maximum depth and lake area, negative correlations with altitude, temperature, summer temperature and ratio of catchment area to lake area. Lake CAR in MX is positively correlated with altitude, precipitation and summer precipitation, negatively correlated with temperature, summer temperature and ratio of catchment area to lake area.

4.1. Controls on soil and lake carbon storage This study demonstrated that altitude, relief degree of land surface, temperature and precipitation were significantly related to SOC density in China, suggesting that difference in regional topography and climate could partly explain the variability in SOC density among various regions. TP, with an average elevation of more than 4000 m a.s.l., played an important role in determining regional climate patterns in China, and thus had strong impacts on the spatial distribution of soil organic carbon density (Chen et al., 2008; Wu et al., 2003). Cold conditions prevailing across this region formed a weak overall pattern of organic matter mineralization, resulting in high SOC density of TP. In eastern China, the climate was humid due to considerable precipitation brought by Asian summer monsoon, while the barrier effect of the Tibetan Plateau to moisture and the long distance from the ocean led to dry conditions for the western China (Li and Morrill, 2010; Chen et al., 2008; Wu et al., 2003). Therefore, the decrease of SOC density from east to west could be attributed to the lower vegetation productivity owing to the increased aridity. On the other hand, the decreasing trend of SOC density from north to south in eastern China was related to the gradually increasing intensity of organic matter mineralization induced by temperature increase (Wu et al., 2003). Regression analysis suggested that CAR of overall lakes in China was not significantly linked to either environmental variables or lake 5

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

productivity, in agreement with dry conditions. Furthermore, the rapid desertification, regional drought trend, salinization and high-intensity agricultural utilization in the ecologically fragile area of northwest China could also contribute to low SOC density (Huang et al., 2016; Zheng et al., 2011; Lal, 2004; Wu et al., 2003). High lake CAR in MX was essentially due to high sediment accumulation rate associated with the soil erosion by water and wind. Conclusively, various climate patterns, geological conditions and anthropogenic interference regulated the spatial distribution and storage of soil and lake organic carbon in China. Our results overturned the conventional understanding that lake carbon stock was closely related to soil carbon storage, indicating soils and lakes had different carbon storage mechanisms in various regions.

characteristics, and there were close correlations between them at regional scale. In MX, lake CAR showed positive correlation to summer precipitation. Indeed, vegetation growth in arid areas was strongly influenced by moisture conditions and the rainfall of this regions was mainly concentrated in the summer months (Wang et al., 2005). Negative relationships between lake CAR and temperature were observed in EP, YG and MX, because hotter conditions were favorable for the decomposition of organic matter. In TP where organic matter decomposition was weak, vegetation productivity was the major factor restricting carbon sequestration. However, high altitude usually corresponded to sparse vegetation; hence, lake CAR showed negative correlation to altitude. Aside from the natural factors, soil and lake organic carbon storage was strongly influenced by human activities (Ballantyne et al., 2017; Yvondurocher et al., 2017; Kaplan, 2015; Zhang et al., 2013). Our results showed lake CAR was significantly related to lake area and ratio of catchment area to lake area in many regions, suggesting that human activity had a large effect on lake carbon accumulation. Conversely, SOC density did not show correlation with land-use comprehensive index, which demonstrated that the influence of human activities on soil carbon storage was quite diverse and could not be described by a simple linear relationship. Human interference was mainly characterized by pastoralism in TP, and deforestation, agricultural cultivation in the other regions of China (Wang et al., 2015; Schlütz and Lehmkuhl, 2009). Deforestation, agriculture and pastoralism destroyed the stability of regional terrestrial ecosystems, resulting in accelerated soil erosion and lake sediment accumulation (Wang et al., 2015; Ran and Lu, 2014; Zhang et al., 2013).

4.3. Regional significance and management implications of soil and lake carbon storage in China This paper estimated the total amount of organic carbon burial in soils of China to be ~72.53 Pg C. Thus, China accounted for ~4.8% of global SOC storage with ~6.4% of the world's surface area (Guenet et al., 2018; Yu et al., 2007; Geng et al., 2000). Moreover, we found the average SOC density of ~8.8 kg C m−2 was also lower than the global mean value of ~10.60 kg C m−2 (Wu et al., 2003; Post et al., 1982). Lower SOC storage and density in China were mainly attributed to large semi-arid regions (~40% of total land surface the country) and long history of agricultural exploitation (Huang et al., 2016; Zheng et al., 2011; Lal, 2004; Wu et al., 2003). The lake organic carbon accumulation rate at 1 m depth of China was estimated to ~10.13 g C m−2 year−1 (the mean basal date of this study was 3641 Cal yr BP), higher than that of ~7.7 g C m−2 year−1 on millennial scale (Wang et al., 2015), but lower than that of ~28.31 g C m−2 year−1 at a short-term scale (Duan et al., 2008). This suggested a significant increase in exogenous organic matter input due to increasing human activities. Although human activities have improved lake carbon sequestration capacity per unit area, it would eventually lead to shrinkage of lake area and aggravation of the aging process (Cao et al., 2018; Zeng, 2016; Duan et al., 2008). The lower soil organic carbon and human-induced change in lake carbon accumulation of China suggested a considerable potential to enhance the carbon sequestration through improved management (Kaplan, 2015; Wang et al., 2015; Zheng et al., 2011; Pan et al., 2003; Wu et al., 2003). It was estimated that the improvement of land management during the next 20–50 years would sequestrate ~3.5 Pg carbon from the atmosphere (Wu et al., 2003), while the implementation of returning the farmland to lake might improve the carbon sequestration potential of China's lakes as 30.26 Gg C year−1 (Duan et al., 2008). With the implementation of the Kyoto protocol, climate change mitigation has become a major environmental issue for both China and the international community (Zheng et al., 2011; Yu et al., 2007). Vast areas of the drylands (47.2% of the world's land area) and various human activities are also major factors restricting global carbon sequestration (Huang et al., 2016; Ahlstrom et al., 2015; Lal, 2004). Soil erosion, salinization, desertification prevailing in arid region, eutrophication, area shrinkage pervading in globally lakes, often result in emission of CO2 into the atmosphere as well as other environmental degradation (Liang et al., 2018a, 2018b; Huang et al., 2016; Zheng et al., 2011; Taylor et al., 2005; Lal, 2004). Therefore, management of drylands and human activities can play a major role in reducing CO2 emissions. Management practices to sequester soil and lake organic carbon include soil management on cropland, runoff prevention, and restoration of degraded soil and lake ecosystems (Liang et al., 2018a, 2018b; Liu, 2015; Machado and Mielniczuk, 2010; Víctor and Carmen, 2008; Lal, 2004) (Table 4). Recommended soil management practices include conservation tillage, mulching, application of biosolids, growing improved species, water harvesting, and more efficient irrigation systems (Liang et al., 2018a, 2018b; Malik et al., 2015; Lymbery

4.2. Terrestrial organic carbon storage modes based on relationship between soil and lake carbon storage in China The transformation of organic carbon in various terrestrial sinks occurred as follows: plants fixed CO2 from the atmosphere through photosynthesis; dead plant material entered the soil and stores as soil organic matter; part of soil carbon was transported to lakes by water run-off over the soil surface; finally, soils and lakes mineralized organic carbon to CO2 or CH4 by heterotrophic microorganisms (Keenan and Williams, 2018; Chapin et al., 2011). Therefore, the conventional understanding indicated that considerable soil organic matter usually responded to abundant exogenous carbon to lakes. Here, we tested the ideas in mainland China with different climate patterns and various geological conditions, while our result showed different spatial distribution and storage of soil and lake organic carbon in various regions. The watershed collection storage mode, primarily observed in the TP region, showed high soil organic carbon density and high lake carbon accumulation rate. A weak overall pattern of organic matter decomposition in the plateau caused high SOC density there. However, high lake CAR was consistent with high sediment accumulation rate connected to organic carbon transport by runoff from soils. NEC and YG revealed another storage mode of autochthonous deposition with high soil organic carbon density and low lake carbon accumulation rate. High SOC density in the two regions could be attributed to relatively low temperature and favorable vegetation, associated with lower intensity of organic matter mineralization and higher bioproductivity. On the other hand, low lake CAR was closely related to low sediment accumulation rate in the regions. The storage mode of human activities affection was characterized by low soil organic carbon density and high lake carbon accumulation rate, represented by EP and MX. Low SOC density in EP was attributed to the hotter conditions, favorable to the mineralization of soil organic matter (Wu et al., 2003), while high lake CAR was strongly linked to high sediment accumulation due to terrestrial organic matter input (Zhang et al., 2013). Additionally, lake eutrophication caused by intensive human activities was another reason for high lake CAR in EP (Wang et al., 2015; Shen, 2013; Zhang et al., 2013). The MX region had low SOC density owing to lower vegetation 6

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

Table 4 Strategies of soil and lake management for carbon sequestration. Problem

Strategy

Practice

Location/region

Reference

Soil erosion

1 Conservation tillage 2 Runoff prevention

No-till farms Mulch Stone cover Residue mulch Plants shelter 1) Soil amendments 2) Conservation management 3) Mycorrhizal fungi 1) Salt-tolerance plant 2) Saline aquaculture 1) Drip and furrow irrigation systems 2) Saline irrigation 3) Drainage by shaft wells 1) Bio- and organic fertilizers 2) Sewage sludge 1) Legumes 2) Rotations 3) Enclosure degraded grassland Mulch

Central Kansas, USA

Langemeier (2010)

Negev Desert Chihuahuan Desert Mediterranean region Central Ohio, USA Rio Grande do Sul, Brazil Plastic greenhouse / Australia Shibin El-Kom, Egypt Shibin El-Kom, Egypt Xinjiang, China Green house, Cairo South Madrid, Spain Sudan Mexico Yanchi, Ningxia Sudan Mediterranean region Israel China Sudan Drylands Australia Melbourne, Australia Longhu Lake, China Mangueira Bay / Laboratory / Dongting Lake, China Poyng Lake, China Balkhash Lake, Kazakhstan Taihu Lake, China Australia Kasumigaura Lake, Japan

Lahav and Steinberger (2001) Rostagno and Sosebal (2001) Víctor and Carmen (2008) Liang et al. (2018a) Machado and Mielniczuk (2010) Wu et al. (2008) Liang et al. (2018b) Lymbery et al. (2013) Malash et al. (2008) Malash et al. (2008) Ren and Xu (2003) Leithy et al. (2009) Marqués et al. (2005) Malik et al. (2015) Follett et al., 2005 Liu (2015) Malik et al. (2015) Víctor and Carmen, 2008 Hillel (1998) Su et al. (2010) Malik et al. (2015) Lal (2004) Wen et al. (2011) Taylor et al. (2005) Zeng (2016) Niencheski and Baumgarten (2007) Nes et al. (2002) Blecken et al. (2010) Cao et al. (2018) Pan et al. (2011) Lai et al. (2012) Benndorf and Miersch (1991) Hu et al. (2008) Wen et al. (2011) Nishihiro et al. (2006)

3 Improved soil structure and quality

Salinization

1 Improved species 2 Irrigation management

3 Nutrient management and recycling Desertification

1 Crop diversification

2 Runoff prevention 3 Water management

Eutrophication

1 External input control

2 Reducing internal loading

Lake shrinkage

1 Restoration of lake area

1) Irrigation with sewage 2) Irrigation with silt-laden water 3) Water harvesting 4) 1) 2) 3) 1) 2) 3) 1) 2)

River regulation Stormwater management Sewage interception N and P fertilizer control Submerged plants Sediment removal Chemical coagulation sedimentation Returning farmland to lake Water storage project management

3) River regulation and water diversion 2 Restoration of lakeside ecosystem

Soil seed banks

Acknowledgments

et al., 2013; Langemeier, 2010; Su et al., 2010). Recommended lake management practices include reducing exogenous nutrients in lakes, growing appropriate plants, nutrient removal, returning farmland to lake, water diversion, and restoration of lakeside ecosystems (Cao et al., 2018; Zeng, 2016; Pan et al., 2011; Wen et al., 2011; Nishihiro et al., 2006; Taylor et al., 2005). If two-thirds of the historic SOC loss in the degraded soils are restored, the soils in drylands could sequester 12–20 Pg C from the atmosphere over a 50-year period (Lal, 2004). The potential of lake carbon sequestration is relatively low compared to the soil, but it will also contribute greatly towards mitigating global climate change (Mendonça et al., 2017; Raymond et al., 2013).

This work was supported by the National Natural Science Foundation of China (Grant Nos. 41822708 and 41571178), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA20100102), the Fundamental Research Funds for the Central Universities (Grant No. lzujbky-2018-k15), and the Second Tibetan Plateau Scientific Expedition (STEP) program (Grant No. XDA20060700). Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.jenvman.2019.109483.

5. Conclusions Global climates are changing rapidly, with unpredictable consequences. Understanding the interconnection between terrestrial sinks is critical for protecting and increasing carbon storage in the future. In this study, we used the data from China's second national soil survey and direct measurements from 54 lakes, to synthesize terrestrial organic carbon storage modes based on relationship between soil and lake carbon. Our results overturned the conventional understanding that considerable soil organic matter usually responded to abundant exogenous carbon deliveries to lakes. China mainland with different climate patterns and various geological conditions showed three storage modes including watershed collection, autochthonous deposition, human activities affection. The results provide insights into carbon storage modes in various regions, and also inform strategies for enhancing global carbon sequestration and future mitigation policies towards global climate change.

Declarations of interest None. References Ahlstrom, A., Raupach, M.R., Schurgers, G., Smith, B., Arneth, A., Jung, M., Reichstein, M., Canadell, J.G., Friedlingstein, P., Jain, A.K., Kato, E., Poulter, B., Sitch, S., Stocker, B.D., Viovy, N., Wang, Y.P., Wiltshire, A., Zaehle, S., Zeng, N., 2015. The dominant role of semi-arid ecosystems in the trend and variability of the land CO2 sink. Science 348, 895–899. Alin, S.R., Johnson, T.C., 2007. Carbon cycling in large lakes of the world: a synthesis of production, burial, and lake atmosphere exchange estimate. Glob. Biogeochem. Cycles 21, 1–12. Avnimelech, Y., Ritvo, G., Meijer, L.E., Kochba, M., 2001. Water content, organic carbon and dry bulk density in flooded sediments. Aquacult. Eng. 25, 25–33. Ballantyne, A., Smith, W., Anderegg, W., Kauppi, P., Sarmiento, J., Tans, P., Shevliakova,

7

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

Machado, F., Mielniczuk, João, 2010. Recovering Soil Structure by Management Practices in a Sandy Clay Loam Acrisol Degraded by Agricultural USA. World Congress of Soil Science: Soil Solutions for A Changing World. . Malash, N.M., Flowers, T.J., Ragab, R., 2008. Effect of irrigation methods, management and salinity of irrigation water on tomato yield, soil moisture and salinity distribution. Irrig. Sci. 26, 313–323. Malik, M., Osman, X.N., Khidir, A., 2015. Traditional and Modern Cultural Practices for the Cultivation of Deserts and Desertification-Affected Lands in Sudan. University of Khartoum. Marcott, S.A., Bauska, T.K., Buizert, C., Steig, E.J., Rosen, J.L., Cuffey, K.M., Fudge, T.J., Severinghaus, J.P., Ahn, J., Kalk, M.L., McConnell, J.R., Sowers, T., Taylor, K.C., White, J.W.C., Brook, E.J., 2014. Centennial-scale changes in the global carbon cycle during the last deglaciation. Nature 514, 616–719. Marqués, M.J., Jiménez, L., Pérez-Rodríguez, R., GarcÍa-Ormaechea, S., Bienes, R., 2005. Reducing water erosion in a gypsic soil by combined use of organic amendment and shrub revegetation. Land Degrad. Dev. 16, 339–350. Mendonça, R., Müller, Roger A., Clow, D., Verpoorter, C., Raymond, P., Tranvik, L.J., Sobek, S., 2017. Organic carbon burial in global lakes and reservoirs. Nat. Commun. 8, 1–6. Montañez, I.P., Mcelwain, J.C., Poulsen, C.J., White, J.D., Dimichele, W.A., Wilson, J.P., Griggs, G., Hren, M., 2016. Climate, pCO2 and terrestrial carbon cycle linkages during late palaeozoic glacial-interglacial cycles. Nat. Geosci. 9, 824–828. Müller, B.M., Maerki, M., Schmid, M., Vologina, E.G., Wehrli, B., Wüest, A., Sturm, M., 2005. Internal carbon and nutrient cycling in Lake Baikal: sedimentation, upwelling, and early Diagenesis. Glob. Planet. Chang. 46, 101–124. National Soil Survey Office (NSSO), 1998. Soil of China. China Agricultural Press, Beijing (in Chinese). Nes, E.H.V., Scheffer, M., Berg, M.S.V.D., Coops, H., 2002. Dominance of charophytes in eutrophic shallow lakes—when should we expect it to be an alternative stable state? Aquat. Bot. 72, 275–296. Niencheski, L.F., Baumgarten, M.G.Z., 2007. Water quality in Mangueira bay: anthropic and natural contamination. J. Coast. Res. 10047, 56–62. Nishihiro, J., Nishihiro, M.A., Washitani, I., 2006. Restoration of wetland vegetation using soil seed banks: lessons from a project in Lake Kasumigaura, Japan. Landsc. Ecol. Eng. 2, 171–176. Pan, G., Li, L., Wu, L., Zheng, X., 2003. Storage and sequestration potential of topsoil organic carbon in China's paddy soils. Glob. Chang. Biol. 10, 79–92. Pan, X.Z., Shi, J.P., 2015. Soil Species Data of the Second National Soil Survey during 1980-1996. National Earth System Science Data Sharing Infrastructure, National Science and Technology Infrastructure of China. http://www.geodata.cn. Pan, M.Q., Yu, X.B., Zhang, C., 2011. Community-based wise-use and sustainable management of wetland: case study from polder xipanshanzhou, Dongting Lake, China. J. Res. Ecol. 2, 66–73 (in Chinese). Post, W.M., Emanuel, W.R., Zinke, P.J., Stangenberger, A.G., 1982. Soil carbon pools and world life zones. Nature 298, 156–159. Ran, L.S., Lu, X.X., 2014. Sediment Load and Carbon Burial in the Yellow River during the Holocene. Pages Magazine April. Ran, Y.H., Li, X., 2006. WESTDC Land Cover Products 2.0. The Environmental and Ecological Science Data Center for West China sponsored by the National Natural Science Foundation of China (NSFC). http://westdc.westgis.ac.cn. Raymond, P.A., Hartmann, J., Lauerwald, R., Sobek, S., Mcdonald, C., Hoover, M., Butman, D., Strieg, R., Mayorga, E., Humborg, C., Kortelainen, P., Durr, H., Meybeck, M., Ciais, P., Guth, P., 2013. Global carbon dioxide emissions from inland waters. Nature 503, 355–359. Ren, J.G., Xu, M., 2003. Research on the relation between salinization of soil and the shaft irrigation and drainage. Chin. J. Geol. Hazard Control 14, 55–57 (in Chinese). Rostagno, C.M., Sosebal, R.B., 2001. Surface application of biosolids in the Chihuahuan Desert: effects on soil physical properties. Arid Land Res. Manag. 15, 233–244. Scharlemann, J.P., Tanner, E.V., Hiederer, R., Kapos, V., 2014. Global soil carbon: understanding and managing the largest terrestrial carbon pool. Carbon Manag. 5, 81–91. Schlütz, F., Lehmkuhl, F., 2009. Holocene climatic change and the nomadic Anthropocene in Eastern Tibet: palynological and geomorphological results from the Nianbaoyeze Mountains. Quat. Sci. Rev. 28, 1449–1471. Shen, J., 2013. Spatiotemporal variations of Chinese lakes and their driving mechanisms since the last glacial maximum: a review and synthesis of lacustrine sediment archives. Sci. Bull. 58, 17–31. Sobek, S., Tranvik, L.J., Cole, J.J., 2005. Temperature independence of carbon dioxide supersaturation in global lakes. Glob. Biogeochem. Cycles 19, GB2003. Stuiver, M., Reimer, R.W., 1993. Extended 14C database and revised CALIB radiocarbon calibration program. Radiocarbon 35, 215e230. Su, Y.Z., Yang, R., Liu, W.J., Wang, X.F., 2010. Evolution of soil structure and fertility after conversion of native sandy desert soil to irrigated cropland in arid region, China. Soil Sci. 175, 246–254. Sun, W., 2003. Distribution pattern and density calculation of soil organic carbon in profile. Soils 35, 236–241 (in Chinese). Taylor, G.D., Fletcher, T.D., Wong, T.H.F., Breen, P.F., Duncan, H.P., 2005. Nitrogen composition in urban runoff—implications for stormwater management. Water Res. 39, 0–1989. Víctor, H., Carmen, R., 2008. Soil-erosion and runoff prevention by plant covers. a review. Agron. Sustain. Dev. 28, 65–86. Wang, G., Han, J., Zhou, L., Xiong, X., Wu, Z., 2005. Carbon isotope ratios of plants and occurrences of C4 species under different soil moisture regimes in arid region of northwest China. Physiol. Plant. 125, 74–81. Wang, M., Chen, H., Yu, Z., Wu, J., Zhu, Q., Peng, C., Wang, Y., Qin, B., 2015. Carbon accumulation and sequestration of lakes in China during the Holocene. Glob. Chang.

E., Pan, Y., Poulter, B., Anav, A., Friedlingstein, P., Houghton, R., Running, S., 2017. Accelerating net terrestrial carbon uptake during the warming hiatus due to reduced respiration. Nat. Clim. Chang. 7, 148–152. Benndorf, J., Miersch, U., 1991. Phosphorous loading and efficiency of biomanipulation. In Verh. Intenat. Limnol. 24, 2482–2488. Blecken, G.T., Zinger, Y., Deletić, A., Fletcher, T.D., Hedström, A., Viklander, M., 2010. Laboratory study on stormwater biofiltration: nutrient and sediment removal in cold temperatures. J. Hydrol. 394, 507–514. Cao, D.W., Li, H.L., Jin, Q., Li, W., Chen, L.G., Li, X.N., 2018. Study on the coagulation and sedimentation effect of the entrophication by the modified chemical. Environ. Sci. Technol. 31 (160), 9–12 (in Chinese). Chapin, F.S., Matson, P.A., Vitousek, P.M., 2011. Principles of Terrestrial Ecosystem Ecology. Springer, New York. Chen, F., Yu, Z., Yang, M., Tto, E., Wang, S., Madsen, D., Huang, X., Zhao, Y., Sato, T., Birks, J., Boomer, I., Chen, J., An, C., Wunnemann, B., 2008. Holocene moisture evolution in arid central Asia and its out-of-phase relationship with Asian monsoon history. Quat. Sci. Rev. 27, 351–364. Danielson, R.E., Sutherland, P.L., 1986. Porosity. In: Klute, A. (Ed.), Methods of Soil Analysis, Part 1, Physical and Mineralogical Methods, second ed. Soil Science Society of America, Madison, WI, USA, pp. 443–461. Dean, W.E., Gorham, E., 1998. Magnitude and significance of carbon burial in lakes, reservoirs, and peatlands. Geology 26, 535–538. Duan, X.N., Wang, X.K., Lu, F., 2008. Carbon sequestration and its potential by wetland ecosystems in China. Acta Ecol. Sin. 28, 463–469 (in Chinese). Doetterl, S., Stevens, A., Six, J., Merckx, R., Oost, K.V., Pinto, A.C., Casanova-Katny, A., Muñoz, C., Boudin, M., Venegas, E.Z., Boeckx, P., 2015. Soil carbon storage controlled by interactions between geochemistry and climate globally. Nat. Geosci. 8, 780–783. Eswaran, H., Evert, V.D.B., Reich, P., 1993. Organic carbon in soils of the world. Soil Sci. Soc. Am. J. 57, 269–273. Follett, R.F., Castellanos, J.Z., Buenger, E.D., 2005. Carbon dynamics and sequestration in an irrigated vertisol in central Mexico. Soil Till. Res. 83, 148–158. Geng, Y.B., Dong, Y.S., Meng, W.Q., 2000. Progresses of terrestrial carbon cycle studies. Prog. Geogr. 19, 297–306 (in Chinese). Gruber, N., Clement, D., Carter, B.R., Feely, R.A., Heuven, S., Hoppema, M., Ishii, M., Key, R.M., Kozyr, A., Lauvset, S.K., Monaco, C.L., Mathis, J.T., Murata, A., Olsen, A., Perez, F.Z., Sabine, C.L., Tanhua, T., Wanninkhof, R., 2019. The oceanic sink for anthropogenic CO2 from 1994 to 2007. Science 6432. Guenet, B., Camino-Serrano, M., Ciais, P., Tifafi, M., Maignan, F., Soong, J.L., Janssens, I.A., 2018. Impact of priming on global soil carbon stocks. Glob. Chang. Biol. 24, 1873–1883. Hillel, D., 1998. Environmental Soil Physics. Academic Press, San Diego, pp. 640–642. Hu, W., Zhai, S., Zhu, Z., 2008. Impacts of the Yangtze river water transfer on the restoration of lake Taihu. Ecol. Eng. 34, 30–49. Huang, J., Yu, H., Guan, X., Wang, G., Guo, R., 2016. Accelerated dryland expansion under climate change. Nat. Clim. Chang. 6, 166–171. Jordon, D.H., Daniel, H.R., Katherine, E.G., Sarah, Z.R., Timothy, I.E., Louis, A.D., Valier, V.G., 2019. Mineral protection regulates long-term global preservation of natural organic carbon. Nature. https://doi.org/10.1038/s41586-019-1280-6. Kaplan, J.O., 2015. Holocene carbon cycle: climate or humans? Nat. Geosci. 8. Kastowski, M., Hinderer, M., Vecsei, A., 2011. Long‐term carbon burial in European lakes: analysis and estimate. Glob. Biogeochem. Cycles 25. Keenan, T.F., Williams, C.A., 2018. The terrestrial carbon sink. Annu. Rev. Environ. Resour. 43, 219–243. Kortelainen, P., Pajunen, H., Rantakari, M., Saarnisto, M., 2004. A large carbon pool and small sink in boreal Holocene lake sediments. Glob. Chang. Biol. 10, 1648–1653. Lai, X.J., Jiang, J.H., Huang, Q., 2012. Water storage effects of Three Gorges project on water regime of Poyang lake. J. Hydroelectr. Eng. 31, 132–136 (in Chinese). Lal, R., 2004. Carbon sequestration in dryland ecosystems. Environ. Manag. 33, 528–544. Lahav, I., Steinberger, Y., 2001. The contribution of stone cover to biological activity in the Negev Desert, Israel. Land Degrad. Dev. 12, 35–43. Leithy, S., Gaballah, M.S., Gomaa, A.M., 2009. Associative impact of bio- and organic fertilizers on geranium plants grown under saline conditions. Electron. J. Environ. Agric. Food Chem. 1, 617–626. Langemeier, M., 2010. Relative technical and cost efficiency of no-till farms. J. Int. Farm Manag. 5, 1–11. Li, Y., Morrill, C., 2010. Multiple factors causing Holocene lake-level change in monsoonal and arid central Asia as identified by model experiments. Clim. Dyn. 35, 1119–1132. Liang, Y., Lal, R., Guo, S., Liu, R., Hu, Y., 2018a. Impacts of simulated erosion and soil amendments on greenhouse gas fluxes and maize yield in miamian soil of central Ohio. Sci. Rep. 8, 520. Liang, W., Ma, X., Wan, P., Liu, L., 2018b. Plant salt-tolerance mechanism: a review. Biochem. Bioph. Res. Co. 495, 286–291. Liu, H.F., Wu, X., Li, Y., Li, Z.S., Liu, G.H., 2014. Effects of land use change on greenhouse gas fluxes from soils: a review. Chinese J. Ecol. 33, 1960–1968 (in Chinese). Liu, X.D., 2015. The Studies of Effects of Enclosure Measure on Vegetation Restoration in the Degradeed Glassland: Taking Yanchi County in Ningxia as an Example (Doctoral dissertation). Beijing Forestry University. Lubowski, R.N., Plantinga, A.J., Stavins, R.N., 2005. Land-use change and carbon sinks: econometric estimation of the carbon sequestration supply function. J. Environ. Econ. Manag. 51, 135–152. Lymbery, A.J., Kay, G.D., Doupé, R.G., Partridge, G.J., Norman, H.C., 2013. The potential of a salt-tolerant plant (distichlis spicata cv. nypa forage) to treat effluent from inland saline aquaculture and provide livestock feed on salt-affected farmland. Sci. Total Environ. 445–446, 192–201.

8

Journal of Environmental Management 250 (2019) 109483

L. Xu, et al.

680–689. Yvondurocher, G., Hulatt, C.J., Woodward, G., Trimmer, M., 2017. Long-term warming amplifies shifts in the carbon cycle of experimental ponds. Nat. Clim. Chang. 7, 209–213. Zeng, L.D., 2016. A study on measures to prevent water eutrophication in longhu lake, Jinjiang. Hydraul. Sci. Tech. 3, 12–15. Zhang, F.J., Xue, B., Yao, S.C., Gui, Z.F., 2013. The organic carbon burial rates in Chinese lake sediments during Holocene megathermal. Quat. Sci. 33, 401–402 (in Chinese). Zheng, J.F., Cheng, K., Pan, G.X., Pete, S., Li, L.Q., Zhang, X.H., Zheng, J.W., Han, X.J., Du, Y.L., 2011. Perspectives on studies on soil carbon stock and the carbon sequestration potential of China. Chin. Sci. Bull. 56, 3748–3758 (in Chinese). Zhuang, D., Liu, J.Y., 1997. Study on the model of regional differentiation of land use degree in China. J. Nat. Resour. 2, 105–111 (in Chinese).

Biol. 21, 4436. Wang, S., Dou, H., 1998. Lakes in China. Science Press, Beijing, China (in Chinese). Wen, L., Rogers, K., Ling, J., Saintilan, N., 2011. The impacts of river regulation and water diversion on the hydrological drought characteristics in the lower Murrumbidgee river, Australia. J. Hydrol. 405, 382–391. Wu, H., Guo, Z., Peng, C., 2003. Land use induced changes of organic carbon storage in soils of China. Glob. Chang. Biol. 9, 305–315. Wu, Q.S., Xia, R.X., Zou, Y.N., 2008. Improved soil structure and citrus growth after inoculation with three arbuscular mycorrhizal fungi under drought stress. Eur. J. Soil Biol. 44, 0–128. Xu, X.L., 2018. A Data Set of Spatial Distribution of Yearly NDVI in China. Resource and Environment Data Cloud Platformhttps://doi.org/10.12078/2018060601. Yu, D.S., Shi, X.Z., Wang, H.J., Sun, W.X., Chen, J.M., Liu, Q.H., Zhao, Y.C., 2007. Regional patterns of soil organic carbon stocks in China. J. Environ. Manag. 85,

9