SESolid EarthSESolid Earth1869-9529Copernicus PublicationsGöttingen, Germany10.5194/se-8-83-2017Leguminous species sequester more carbon than gramineous species in cultivated
grasslands of a semi-arid areaLiuYuhttps://orcid.org/0000-0003-0706-4026TianFupingJiaPengyanZhangJinggeHouFujiangWuGaolingaolinwu@gmail.comhttps://orcid.org/0000-0002-5449-7134State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, ChinaUniversity of Chinese Academy of Sciences, Beijing 100049, ChinaThe Lanzhou Scientific Observation and Experiment Field Station of Ministry of Agriculture for Ecological System in the Loess Plateau Area,
Lanzhou Institute of Animal and Veterinary Pharmaceutics Sciences, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu 730050, ChinaState Key Laboratory of Grassland Agro-Ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, Gansu 730020, ChinaGaolin Wu (gaolinwu@gmail.com)23January20178183914August201612September201620December20168January2017This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from https://se.copernicus.org/articles/8/83/2017/se-8-83-2017.htmlThe full text article is available as a PDF file from https://se.copernicus.org/articles/8/83/2017/se-8-83-2017.pdf
The establishment of grasslands on abandoned cropland has been proposed as
an effective method to mitigate climate change. In this study, five
cultivated grasslands (three leguminous species and two gramineous species),
one abandoned cropland, and one natural grassland were studied to examine
how soil organic carbon (SOC) sequestration rate and sequestration
efficiency change in a semi-arid area in China. Our results showed that
leguminous grasslands had greater total biomass (above- and belowground
biomass), SOC storage, SOC sequestration rate, and efficiency than gramineous
grasslands, abandoned cropland, and natural grassland during the
experimental period. The largest soil carbon (C) accumulation in leguminous
grassland was mainly attributed to the capacity to incorporate C and the
higher biomass production. Leguminous grasslands accumulated more SOC than
gramineous grasslands by 0.64 Mg C ha-1 yr-1. The average SOC
sequestration efficiency in leguminous grassland (1.00) was about 2 times
greater than gramineous grassland (0.34). The results indicate that
cultivated leguminous grassland sequestered more SOC with higher SOC
sequestration efficiency than cultivated gramineous grassland in arid and
semi-arid areas. Our results provide a reference for ecological management
in arid and semi-arid areas.
Introduction
Soil is a key component of the Earth system and contributes to services,
goods, and resources to humankind (Brevik et al., 2015). Soil stores more
carbon (C) than the atmosphere and vegetation (Köchy et al., 2015a;
Keesstra et al., 2016). Soil organic carbon (SOC) is a key component of the
global C cycle, and its potential to sink from atmosphere carbon dioxide
(CO2) has been widely discussed in the scientific literature throughout
the world (Guo and Gifford, 2002; Lal, 2004; De Deyn et al., 2008; Deng et
al., 2014a; Parras-Alcántara et al., 2015). In terrestrial ecosystems,
SOC pool dynamics can be affected by many factors, such as climate change
(Lal, 2004; Field et al., 2007), management practices (Luo et al., 2010; Ono
et al., 2015), land use, etc. (Post and Kwon, 2000; Don et al., 2011; Deng et al., 2014b; Muñoz-Rojas et
al., 2015).
SOC plays a critical role in controlling soil fertility and cropping system
productivity and sustainability (Hurisso et al., 2013; De Moraes Sá et
al., 2015), particularly in low-productivity arid and semiarid
agro-ecosystems (Behera and Shukla, 2015; Willaarts et al.,
2016). To develop farming methods that conserve SOC
is therefore of a great importance (Lal, 2004) in this area. Cultivated
grasslands have many more advantages than natural grassland regeneration,
such as accelerating vegetation restoration and improving grassland
productivity. Establishing artificial grassland is therefore an effective
method to restore vegetation and improve soil fertility by accumulation of
SOC (Fu et al., 2010; Wu et al., 2010; Li et al., 2014). Vegetation
degradation and exponential population growth have caused massive amounts of
soil and water to be lost. The Chinese government has implemented the most
ambitious ecological program titled “Grain-for-Green” Project (converting
degraded, marginal land, and cropland into grassland, shrubland, and forest),
with the objective of transforming the low-yield slope cropland into
grassland, reducing soil erosion, maintaining land productivity, and
improving environmental quality (Fu, 1989; Liu et al., 2008). The large scale
of the project can enhance C sequestration capacity in China, especially in
arid and semi-arid areas (Chang et al., 2011; Song et al., 2014).
The studied site localization and schematic figure of the sampling
strategies.
Many prior studies about SOC have paid much attention to converting farmland
to grassland, shrubland, or forest (Fu et al., 2010; Deng et al., 2014a).
However, less attention has been devoted to the SOC among different
species of grasslands. In this study, we focused on ascertaining the influence
of leguminous and gramineous grasslands on SOC sequestration capacity and
efficiency. Many studies have demonstrated that there is a significant and
positive relationship on SOC and nitrogen (Deng et al., 2013; Zhu et al.,
2014). Therefore, we hypothesize that leguminous grassland has higher SOC
sequestration capacity than gramineous grassland. More specifically, our
objectives are (i) to analyze the differences of storage efficiency under
different grasslands and (ii) to determine which type of cultivated
grassland might better improve SOC storage in arid and semi-arid areas.
Description of studied grassland types.
Grassland typesSpeciesSeeding rates(kg ha-1)Leguminous grasslandCoronilla varia L.7.5Onobrychis viciifolia Scop.30Medicago sativa L.12Gramineous grasslandPoa pratensis L.7.5Agropyron cristatum (L.) Gaertn.15Uncultivated grasslandAbandoned cropland. Natural successional species were present, e.g., Chenopodium album L., Agropyron cristatum L.Natural grasslandA local native grassland community. Dominant species were Stipa breviflora Griseb., Stipa aliena Keng, Artemisia capillaris Thunb., Artemisia annua L.Material and methodsExperimental site and design
The study was conducted at the Lanzhou Scientific Observation And Experiment
Field Station of the Ministry of Agriculture for Ecological System in the
Loess Plateau Area (103∘44.342′ E, 36∘02.196′ N;
1635 m a.s.l.) in Lanzhou, Gansu Province, China (Fig. 1). The site is
located the temperate continental climate zone. Data from the National
Meteorological Information Center of China showed that the mean annual
temperature is 9.3 ∘C. Mean annual precipitation is 324.5 mm, of
which approximately 80 % falls during the growing season (from May to
September). The topography of study area is typical of the Loess Plateau and
comprises plains, ridges and mounds, etc. Soil parent material is Quaternary
eolian loess and the main soil type is sierozem, which is a calcareous soil
and characteristic of the Chinese loess region (Li et al., 2010). Sierozem
is the soil developed in the dry climate and desert steppe in warm temperate
zone, which has low humus content and weak leaching (National Soil Census
Office, 1998). There is a patch or pseudohyphae calcium carbonate deposition
and strong lime reaction within the full sierozem profile (Shi et
al., 2013).
The experimental site was originally under sorghum (Sorghum bicolor L.) continuously from
1970 to 2005, and it was abandoned from 2005 to 2007 (grazing exclusion). In
2007, five cultivated grasslands, one uncultivated grassland (abandoned
cropland, Un-G), and one natural grassland (Na-G) were established in the
study site. Five main forage grasses, widely grown across semi-arid
areas, were selected to establish the five types of cultivated grassland,
namely three leguminous species (Coronilla varia L., L-CV; Onobrychis viciifolia Scop, L-OV; Medicago sativa L., L-MS) and two
gramineous species (Poa pratensis L., G-PA; Agropyron cristatum L. Gaertn., G-AC). Seeding rates in different
grasslands are shown in Table 1. The different seeding rates were selected
based on the germination percentage and to guarantee the equal plant density
in each type of grassland. These rates were determined based on local
farmland crop density reference values. We designed the experiment to be a
randomized plot design. Three experimental plots (10 m × 20 m) were
established randomly within each of the grassland areas. The forage grasses
were planted in early April of 2007, and all plots were weeded manually and
watered three times (April, June, October) annually from 2008 to 2012 to
preserve the monocultures. The plots were not fertilized during cultivation.
All the plots were harvested once a year in October.
Aboveground plant and belowground biomass sampling
Ten quadrats (1 m × 1 m) were randomly set up in each plot in late
August every year (2008–2012). Aboveground biomass was measured by
harvesting the upper plant parts (clipping their stems at the soil surface)
from each quadrat. At each quadrat, all green aboveground plant parts and
litter were collected with the labeled envelops. Then samples were dried at
105 ∘C until their mass was constant, and then their mass was
weighed and recorded.
Belowground biomasses and soil samples were taken in the four corners and
the center of each quadrat where the aboveground biomass sampling point was
located (Fig. 1). Belowground biomass was collected using a soil drilling
sampler with 9 cm inner diameter at 0–100 cm soil layer (separated into
increments every 10 cm). Roots in the soil samples were obtained by a 2 mm
sieve. Then the remaining roots in the soil samples were isolated by shallow
trays, allowing the flowing water from the trays to pass through a 0.5 mm
mesh sieve. All the roots samples were oven-dried at 65 ∘C until
their mass was constant, and then they were weighed.
Soil sampling and determination
To collect the soil samples at each quadrat, the same layer samples as
those collected for belowground biomass (every 10 cm) were mixed together
to form a composite sample. The samples were passed through a 2 mm sieve to
remove the roots and other debris. A 5 cm diameter and 5 cm high stainless
steel cutting ring (100 cm3) was used to measure soil bulk density (BD)
at adjacent points to the soil sampling. Soil bulk density was measured at
the depth of 0–100 cm (10 cm a layer and then averaged). The dry mass was
measured after oven-drying at 105 ∘C. SOC content was measured
using the method of the vitriol acid-potassium dichromate oxidation (Walkley
and Black, 1934). For each sample, analyses were replicated three times.
The p values of homogeneity of variances by the Levene test and
normality by the Shapiro–Wilk test in soil organic carbon content (SOC),
soil C storage, and soil bulk density (BD).
Levene test Shapiro–Wilk test Grassland typesBDSOCSOC storageBDSOCSOC storageL-MS0.050.270.540.070.120.15L-OV0.180.030.040.190.320.36L-CV0.170.840.100.530.180.18G-PA0.120.100.010.070.030.02G-AC0.020.090.260.090.170.22Un-G0.010.100.060.030.050.03Na-G0.780.270.370.030.310.44Relative calculation
BD was calculated based on the oven-dried weight of the composite soil
samples (Deng et al., 2013).
SOC stock for each soil layer was calculated using the equation as follows
(Deng et al., 2013):
Cs=BD×SOC×D10,
where Cs is the SOC stock (Mg ha-1); BD is the soil bulk density
(g cm-3); SOC is the soil organic carbon content (g kg-1); and
D is the thickness of the sampled soil layer (cm).
SOC sequestration rate (SSR, Mg ha-1 yr-1) was calculated as
follows (Hua et al., 2014):
SSR=Ct-C0t,
where (Ct-C0) is SOC sequestration; Ct is the SOC stock
in 2012; C0 is the SOC stock in 2008; t was the duration of experiment
(year).
The SOC sequestration efficiency was estimated using the SOC sequestration
in the weight of total biomass (aboveground biomass and belowground biomass)
of per unit area:
Cse=ΔCBT10,
where Cse is the SOC sequestration efficiency; C
(Mg ha-1) is the SOC sequestration from 2008 to 2012; BT
(kg m-2) is the total biomass (above ground and below ground) from 2008
to 2012.
Total biomass (a), SOC sequestration (b), SOC
sequestration rate (c), and SOC sequestration efficiency (d)
for different grasslands from 2008 to 2012. The grassland types are
L-CV, Coronilla varia; L-OV, Onobrychis viciifolia; L-MS,
Medicago sativa; G-PA, Poa pratensis; G-AC,
Agropyron cristatum; Un-G, uncultivated grassland; Na-G, natural
grassland. Bars indicate mean ± standard error. Bars with the different
lowercase letters above them indicate there was significant difference between
the means at p < 0.05 level. The dotted lines indicate the means
of the same grassland types.
Statistical analyses
Data were examined for normality using the Shapiro–Wilk test and homogeneity
of variances by the Levene test before analysis (Table 2). Data non-normally
distributed were log-transformed. All data were expressed as mean values
± standard error (M ± SE). The total biomass (aboveground
and belowground biomass) means the average of 5 years during the
experimental period. The means of SOC sequestration rate and SOC
sequestration efficiency among the different grassland types were assessed
using one-way analysis of variance (ANOVA). Two-way ANOVA of Type III was
performed to test the influences of grassland types and time on SOC content,
storage, and bulk density. Tukey's test was conducted to test the significance
at p < 0.05 level. All the statistical analyses were performed with
SPSS version 18.0 (SPSS Inc., Chicago, IL, USA).
Two-way ANOVA F and p values for the effects of plot types,
year, and interactions on total biomass (TB), soil organic carbon content
(SOC), soil C storage, and soil bulk density (BD).
Between 2008 and 2012, the five cultivated grasslands had in general greater
total biomass values (mean by 189.36 %) than the uncultivated grassland
and natural grassland. In addition, the three grasslands cultivated with the
leguminous species had greater annual total biomass (mean by 72.6 %) than
two gramineous grasslands. L-MS grassland consistently had the greatest
total biomass throughout the study period (Fig. 2a).
Soil C concentration (M ± SE g kg-1, average value of
100 cm soil depth) in different years and grassland types. The grassland
types are L-CV, Coronilla varia; L-OV, Onobrychis viciifolia; L-MS, Medicago sativa; G-PA, Poa pratensis;
G-AC, Agropyron cristatum; Un-G, uncultivated grassland; Na-G,
natural grassland. Values followed by different lowercase letters within
columns and uppercase letters within rows are significantly different at
p < 0.05.
Soil bulk density (M ± SE g cm-3, average value of
100 cm soil depth) in different years and grassland types. The
grassland types are L-CV, Coronilla varia; L-OV,
Onobrychis viciifolia; L-MS, Medicago sativa; G-PA,
Poa pratensis; G-AC, Agropyron cristatum; Un-G,
uncultivated grassland; Na-G, natural grassland. Values followed by different
lowercase letters within columns and uppercase letters within rows are
significantly different at p < 0.05.
SOC stock (M ± SE Mg C ha-1) at the depth of
0–100 cm in different years and grassland types. The grassland types
are L-CV, Coronilla varia; L-OV, Onobrychis viciifolia;
L-MS, Medicago sativa; G-PA, Poa pratensis; G-AC,
Agropyron cristatum; Un-G, uncultivated grassland; Na-G, natural
grassland. Values followed by different lowercase letters within columns and
uppercase letters within rows are significantly different at
p < 0.05.
Results from two-way ANOVA showed that the plots, year, and interactions all
significantly affected total biomass, SOC content, and BD
(p < 0.001; Table 3). The average SOC content during the study
period followed leguminous grasslands (4.21 ± 0.31 g kg-1),
natural grasslands (2.90 ± 0.14 g kg-1), uncultivated grasslands
(2.58 ± 0.17 g kg-1), gramineous grasslands
(2.46 ± 0.15 g kg-1), and it increased over time in all
grasslands (Table 4). The effects of grassland types on BD followed
uncultivated and natural grassland (1.44 ± 0.02 g cm-3),
gramineous grasslands (1.43 ± 0.01 g cm-3), leguminous
grasslands (1.40 ± 0.01 g cm-3, Table 5).
SOC storage under all grassland types increased significantly throughout the
study period (Table 6). The three leguminous grasslands accumulated C with
an average rate of 1.00 Mg C ha-1 yr-1, which is more than the 0.34 Mg C ha-1 yr-1 in gramineous grassland, and more than the average of
uncultivated and natural grasslands (0.25 Mg C ha-1 yr-1;
Fig. 2c). The mean SOC sequestration efficiency in the leguminous grassland
was 0.26, which was significantly greater than other grassland types (0.13;
p < 0.05; Fig. 2d).
Discussion
Grasslands can have a significant effect in arid and semi-arid areas' C cycle
through changing soil C accumulation rates and turnover, soil erosion, and
vegetation biomass (Deng et al., 2014a; Liu et al.,
2017). Plants regulate SOC stock by controlling,
assimilating, and accumulating C in the plant root system, and then through
plant respiration and leaching release from soil to atmosphere (De Deyn et
al., 2008; Garcia-Diaz et al., 2016). SOC inputs mostly originate from
decaying aboveground and belowground plant tissue, so greater soil C
accumulation can be mainly ascribed to increasing soil C input from higher
biomass production (Deng et al., 2014c; Wu et al., 2016). Mutualistic
symbionts (N-fixing bacteria and mycorrhizal fungi) are also an important
source of C input to soil, especially in actively growing plants (Bardgett et
al., 2005). In grasslands, atmospheric C (CO2) is sequestrated through
photosynthesis and respiration. Then, C fixes in a stable SOC pool or
releases back into the atmosphere (Post and Kwon, 2000). Therefore, studying
the C sequestration in grassland ecosystems can help to identify the
magnitude of global C sinks and sources (Li et al., 2014). Our results showed
that leguminous grassland had greater SOC contents and storage efficiency
than gramineous grassland. Different species may incorporate more or less C
according to their specific metabolism. Legumes have been identified as a key
driver of C sequestration in many studies (Fornara and Tilman, 2008; Wu et
al., 2016). These species live in symbiosis with Rhizobium bacteria,
which fix atmospheric N. Moreover, many previous studies have demonstrated
that soil C and total nitrogen are significantly and positively correlated
(Deng et al., 2013; De Oliveira et al., 2015). Since mycorrhizal fungi can
immobilize C in their mycelium and improve C sequestration in soil aggregates
(Rillig and Mummey, 2006), it might be expected that the cultivated
leguminous grasslands significantly improved soil N content that led to
larger C sequestration ability than the non-leguminous grasslands.
The biomass fraction resulting in SOC build-up (plant residuals) was possibly
strongly affected by management practices including the selection of plant
species (Don et al., 2011). Species composition may have had a critical role
in determining the aboveground productivity (Liu et al.,
2016). Over a relatively long time, the proportion of
the aboveground biomass enters soil as organic matter and incorporates into
soil through physical and biological processes. Some leachates from plant
material in the litter layer, root exudates, solid decomposed litter, and
fragmented plant structure materials could have been the main sources of soil
organic matter (Jones and Donnelly, 2004; Novara et al., 2015). The amount of
plant residuals returned to the soil may have affected the SOC (Musinguzi et
al., 2015; Wasak and Drewnik, 2015). Mostly perennial plants were managed
with high planting densities to produce greater biomass exports (Hobbie et
al., 2007; Köchy et al., 2015b). Deng et al. (2014c) found that plant
biomass is the key driver in soil C sequestration. In this study, SOC
increased dramatically in leguminous grassland most likely due to the greater
total biomasses of the leguminous grasses, which result in the increasing
soil C inputs from the litter layer and root biomass (De Deyn et al., 2008;
Wu et al., 2010; Novara et al., 2015). Moreover, symbiosis might have
increased plant productivity through enhancing the acquisition of limited
resources. Our results demonstrate that a key variable associated with higher
SOC content in leguminous grasslands compared to gramineous grasslands is the
greater total biomass accumulation. The leguminous grasslands had both higher
above- and belowground biomasses than gramineous grasslands. Total biomass
was 16.35 kg m-2 in leguminous grasslands, which was
9.47 kg m-2 higher than in gramineous grasslands from 2008 to 2012.
The grasslands in our study harvested the aboveground biomass once annually,
so all the stubble and plant litters input to soil as a C supply.
SOC sequestration rates in the leguminous grasslands were significantly
higher than those found in the gramineous grasslands (Fig. 1c). This maybe
resulted from the different decomposition rates in soils, because the
leguminous and gramineous grass species result in multifarious nutrient
conditions. Litter and fragmented plant parts at the soil surface are
decomposed by micro-organisms and are gradually incorporated into the soil
through some complex processes, such as humification and mineralization
(Novara et al., 2015). Legumes have the ability to develop root nodules and
to fix nitrogen in symbiosis with compatible rhizobia, which can improve the
soil nutrient status and microbial community (Hurisso et al., 2013). Root
nodules promote the symbiosis with micro-organisms, which are responsible
for the decomposition of the plants and therefore constitute the key of the
transmission of the stored C into the soil. Furthermore, the increasing
fertility of the soils in the leguminous grasses should facilitate the
increasing productivity of the plants (Wu et al., 2016). Our results showed
that SOC sequestration efficiency under leguminous grassland was evidently
greater than that in the gramineous grassland (Fig. 1d). It is noteworthy
that L-MS grassland had the highest total biomass of 22.59 kg m-2, which is
2.38 times as much as the average of gramineous grasslands (Fig. 2a).
Moreover, SOC sequestration in L-MS grassland was 3 times higher than
the average of gramineous grasslands (Fig. 2b).
Despite the indications from this study of higher SOC sequestration rate and
efficiency in leguminous grassland, specific research is still needed to
determine the potential mechanisms of each species in sequestrating C. Many
studies have demonstrated that legumes are high water-consuming plants
compared to gramineous ones in arid and semi-arid areas, so it is necessary to
balance the ecological effect of grassland for rational utilization of
resources.
Conclusion
Leguminous grassland had greater SOC storage, sequestration rate, and
efficiency than gramineous grassland. The greater soil C accumulation of
leguminous grasslands was mainly ascribed to the capacity to incorporate C
and the higher biomass production. Leguminous grasslands accumulated an
average rate of 0.64 Mg C ha-1 yr-1 more than
gramineous grasslands. The average SOC sequestration efficiency in
leguminous grasslands was 2 times greater than that in the gramineous
grasslands. Our results provide a reference for ecological management in
arid and semi-arid areas.
Data availability
The data are not publicly available due to copyright issues.
The authors declare that they have no conflict of
interest.
Acknowledgements
We thank the editor for suggestions on this article. This research was funded
by the National Natural Science Foundation of China (41525003, 31372368,
41371282, and 41303062), the Youth Innovation Promotion Association CAS
(2011288), the “Light of West China Program” of CAS (XAB2015A04), and
Lanzhou Institute of Animal
and Veterinary Pharmaceutics Sciences of Chinese Academy of Agricultural
Sciences (CAAS-ASTIP-2014-LIHPS-08). Edited
by: M. Muñoz-Rojas Reviewed by: M. Ledevin, B. Turgut, and
two anonymous referees
ReferencesBardgett, R. D., Bowman, W. D., Kaufmann, R., and Schmidt, S. K.: A temporal
approach to linking aboveground and belowground ecology, Trends Ecol. Evol.,
20, 634–641, 10.1016/j.tree.2005.08.005, 2005.Behera, S. K. and Shukla, A. K.: Spatial distribution of surface soil acidity,
electrical conductivity, soil organic carbon content and exchangeable
potassium, calcium and magnesium in some cropped acid soils of India, Land
Degrad. Dev., 26, 71–79, 10.1002/ldr.2306, 2015.Brevik, E. C., Cerdà, A., Mataix-Solera, J., Pereg, L., Quinton, J. N.,
Six, J., and Van Oost, K.: The interdisciplinary nature of SOIL,
SOIL, 1, 117–129, 10.5194/soil-1-117-2015, 2015.Chang, R. Y., Fu, B. J., Liu, G. H., and Liu, S. G.: Soil carbon
sequestration potential for “Grain for Green” Project in Loess Plateau,
China, Environ. Manage., 48, 1158–1172, 10.1007/s00267-011-9682-8, 2011.De Deyn, G. B., Cornelissen, J. H., and Bardgett, R. D.: Plant functional
traits and soil carbon sequestration in contrasting biomes, Ecol. Lett., 11,
516–531, 10.1111/j.1461-0248.2008.01164.x, 2008.De Moraes Sá, Jã. C., Séguy, L., Tivet, F., Lal, R., Bouzinac,
S., Borszowskei, P. R., Briedis, C., Dos Santos, J. B., Da Cruz Hartman, D.,
Bertoloni, C. G., Rosa, J., and Friedrich, T.: Carbon depletion by plowing
and its restoration by no-till cropping systems in oxisols of subtropical and
tropical agro-ecoregions in Brazil, Land Degrad. Dev., 26, 531–543,
10.1002/ldr.2218, 2015.Deng, L., Shangguan, Z. P., and Sweeney, S.: Changes in soil carbon and
nitrogen following land abandonment of farmland on the Loess Plateau, China,
PLoS ONE, 8, e71923, 10.1371/journal.pone.0071923, 2013.Deng, L., Liu, G. B., and Shangguan, Z. P.: Land-use conversion and changing
soil carbon stocks in China's “Grain-for-Green” Program: a synthesis, Glob.
Change Biol., 20, 3544–3556, 10.1111/gcb.12508, 2014a.Deng, L., Shangguan, Z. P., and Sweeney, S.: “Grain-for-Green” driven land
use change and carbon sequestration on the Loess Plateau, China, Sci. Rep.,
24, 414–422, 10.1038/srep07039, 2014b.Deng, L., Wang, K. B., Li, J. P., Shangguan, Z. P., and Sweeney, S.: Carbon
storage dynamics in alfalfa (Medicago sativa) fields on the Loess Plateau,
China, CLEAN-Soil, Air, Water, 42, 1253–1262, 10.1002/clen.201300079,
2014c.De Oliveira, S. P., De Lacerda, N. B., Blum, S. C., Escobar, M. E. O., and De
Oliveira, T. S.: Organic carbon and nitrogen stocks in soils of northeastern
Brazil converted to irrigated agriculture, Land Degrad. Dev., 26, 9–21,
10.1002/ldr.2264, 2015.Don, A., Schumacher, J., and Freibauer, A.: Impact of tropical land-use
change on soil organic carbon stocks – a meta-analysis, Glob. Change Biol.,
17, 1658–1670, 10.1111/j.1365-2486.2010.02336.x, 2011.Field, C. B., Lobell, D. B., Peters, H. A., and Chiariello, N. R.: Feedbacks
of terrestrial ecosystems to climate change, Annu. Rev. Env. Resour., 32,
1–29, 10.1146/annurev.energy.32.053006.141119, 2007.Fornara, D. A. and Tilman, D.: Plant functional composition influences rates
of soil carbon and nitrogen accumulation, J. Ecol., 96, 314–322,
10.1111/j.1365-2745.2007.01345.x, 2008.Fu, B. J.: Soil erosion and its contrrol in the Loess Plateau of China, Soil
Use Manage., 5, 76–81, 10.1111/j.1475-2743.1989.tb00765.x, 1989.Fu, X. L., Shao, M. A., Wei, X. R., and Horton R.: Soil organic carbon and
total nitrogen as affected by vegetation types in northern Loess Plateau of
China, Geoderma, 155, 31–35, 10.1016/j.geoderma.2009.11.020, 2010.Garcia-Diaz, A., Bienes-Allas, R., Gristina, L., Cerdà, A., Novara, A.,
and Pereira, P.: Carbon input threshold for soil carbon budget optimization
in eroding vineyards, Geoderma, 271, 144–149,
10.1016/j.geoderma.2016.02.020, 2016.Guo, L. B. and Gifford, R. M.: Soil carbon stocks and land use change, Glob.
Change Biol., 8, 345–360, 10.1046/j.1354-1013.2002.00486.x, 2002.Hobbie, S. E., Ogdahl, M., Chorover, J., Chadwick, O. A., Oleksyn, J.,
Zytkowiak, R., and Reich, P. B.: Tree species effects on soil organic matter
dynamics: the role of soil cation composition, Ecosystems, 10, 999–1018,
10.1007/s10021-007-9073-4, 2007.Hua, K. K., Wang, D. Z., Guo, X. S., and Guo, Z. B.: Carbon sequestration
efficiency of organic amendments in a long-term experiment on a vertisol in
Huang-Huai-Hai Plain, China, PloS ONE, 9, e108594,
10.1371/journal.pone.0108594, 2014.Hurisso, T. T., Norton, J. B., and Norton, U.: Soil profile carbon and
nitrogen in prairie, perennial grass–legume mixture and wheat-fallow
production in the central High Plains, USA, Agr. Ecosyst. Environ., 181,
179–187, 10.1016/j.agee.2013.10.008, 2013.Jones, M. B. and Donnelly, A.: Carbon sequestration in temperate grassland
ecosystems and the influence of management, climate and elevated CO2,
New Phytol., 164, 423–439, 10.1111/j.1469-8137.2004.01201.x, 2004.Keesstra, S. D., Bouma, J., Wallinga, J., Tittonell, P., Smith, P.,
Cerdà, A., Montanarella, L., Quinton, J. N., Pachepsky, Y., van der
Putten, W. H., Bardgett, R. D., Moolenaar, S., Mol, G., Jansen, B., and
Fresco, L. O.: The significance of soils and soil science towards realization
of the United Nations Sustainable Development Goals, SOIL, 2, 111–128,
10.5194/soil-2-111-2016, 2016.Köchy, M., Hiederer, R., and Freibauer, A.: Global distribution of soil
organic carbon – Part 1: Masses and frequency distributions of SOC stocks
for the tropics, permafrost regions, wetlands, and the world, SOIL, 1,
351–365, 10.5194/soil-1-351-2015, 2015a.Köchy, M., Don, A., van der Molen, M. K., and Freibauer, A.: Global
distribution of soil organic carbon – Part 2: Certainty of changes related
to land use and climate, SOIL, 1, 367–380, 10.5194/soil-1-367-2015,
2015b.Lal, R.: Soil carbon sequestration to mitigate climate change, Geoderma, 123,
1–22, 10.1016/j.geoderma.2004.01.032, 2004.Li, X. D., Fu, H., Guo, D., Li, X. D., and Wan, C. G.: Partitioning soil
respiration and assessing the carbon balance in a Setaria italica
(L.) Beauv. Cropland on the Loess Plateau, Northern China, Soil Biol.
Biochem., 42, 337–346, 10.1016/j.soilbio.2009.11.013, 2010.Li, Y. Y., Dong, S. K., Wen, L., Wang, X. X., and Wu, Y.: Soil carbon and
nitrogen pools and their relationship to plant and soil dynamics of degraded
and artificially restored grasslands of the Qinghai-Tibetan Plateau,
Geoderma, 213, 178–184, 10.1016/j.geoderma.2013.08.022, 2014.Liu, J. G., Li, S. X., Ouyang, Z. Y., Tam, C., and Chen, X. D.: Ecological
and socioeconomic effects of China's policies for ecosystem services. P.
Natl. Acad. Sci. USA, 105, 9477–9482, 10.1073/pnas.0706436105, 2008.Liu, Y., Wu, G. L., Ding, L. M., Tian, F. P., and Shi, Z. H.:
Diversity–Productivity Trade-off During Converting Cropland to Perennial
Grassland in the Semi-arid Areas of China, Land Degrad. Dev.,
10.1002/ldr.2561, online first, 2016.Liu, Y., Dang, Z. Q., Tian, F. P., Wang, D., and Wu, G. L.: Soil organic
carbon and inorganic carbon accumulation along a 30-year grassland
restoration chronosequence in semi-arid regions (China), Land Degrad. Dev.,
28, 189–198, 10.1002/ldr.2632, 2017.Luo, Z. K., Wang, E. L., and Sun, Q. J.: Soil carbon change and its response
to agricultural practices in Australian agro-ecosystems: a review and
synthesis, Geoderma, 155, 211–223, 10.1016/j.geoderma.2009.12.012, 2010.Muñoz-Rojas, M., Jordán, A., Zavala, L. M., De la Rosa, D.,
Abd-Elmabod, S. K., and Anaya-Romero, M.: Impact of land use and land cover
changes on organic carbon stocks in mediterranean soils (1956–2007), Land
Degrad. Dev., 26, 168–179, 10.1002/ldr.2194, 2015.Musinguzi, P., Ebanyat, P., Tenywa, J. S., Basamba, T. A., Tenywa, M. M., and
Mubiru, D.: Precision of farmer-based fertility ratings and soil organic
carbon for crop production on a Ferralsol, Solid Earth, 6, 1063–1073,
10.5194/se-6-1063-2015, 2015.
National Soil Census Office: Soil in China, China agriculture press, Beijing,
China, 56–434, 1998 (in Chinese).Novara, A., Rühl, J., La Mantia, T., Gristina, L., La Bella, S., and
Tuttolomondo, T.: Litter contribution to soil organic carbon in the processes
of agriculture abandon, Solid Earth, 6, 425–432, 10.5194/se-6-425-2015,
2015.Ono, K., Mano, M., Han, G.H., Nagai, H., Yamada, T., Kobayashi, Y., Miyata,
A., Inoue, Y., and Lal, R.: Environmental controls on fallow carbon dioxide
flux in a single-crop rice paddy, Japan, Land Degrad. Dev., 26, 331–339,
10.1002/ldr.2211, 2015.Parras-Alcántara, L., Díaz-Jaimes, L., and Lozano-García, B.:
Management effects on soil organic carbon stock in mediterranean open
rangelands-treeless grasslands, Land Degrad. Dev., 26, 22–34,
10.1002/ldr.2269, 2015.Post, W. M. and Kwon, K. C.: Soil carbon sequestration and land-use change:
proceses and potential, Glob. Change Biol., 6, 317–327,
10.1046/j.1365-2486.2000.00308.x, 2000.Rillig, M. C. and Mummey, D. L.: Mycorrhizas and soil structure, New Phytol.,
171, 41–53, 10.1111/j.1469-8137.2006.01750.x, 2006.Shi, R. X., Yang, X. H., Zhang, H. Q., and Wang L. X.: Vertical
differentiation analysis of sierozem profile characteristics in Yili-River
valley, China, Afr. J. Agr. Res., 8, 6509–6517, 10.5897/AJAR12.498,
2013.Song, X. Z., Peng, C. H., Zhou, G. M., Jiang, H., and Wang, W. F.: Chinese
Grain for Green program led to highly increased soil organic carbon levels:
A meta-analysis, Sci. Rep., 4, 4460, 10.1038/srep04460, 2014.Walkley, A. and Black, I. A.: An examination of the Degtjareff method for
determining soil organic matter, and a proposed modification of the chromic
acid titration method, Soil Sci., 37, 29–38,
10.1097/00010694-193401000-00003, 1934.
Wasak, K. and Drewnik, M.: Land use effects on soil organic carbon
sequestration in calcareous Leptosols in former pastureland – a case study
from the Tatra Mountains (Poland), Solid Earth, 6, 1103–1115,
10.5194/se-6-1103-2015, 2015.Willaarts, B. A., Oyonarte, C., Muñoz-Rojas, M., Ibáñez, J. J.,
and Aguilera, P. A.: Environmental factors controlling soil organic carbon
stocks in two contrasting mediterranean climatic areas of southern Spain,
Land Degrad. Dev., 27, 603–611, 10.1002/ldr.2417, 2016.Wu, G. L., Liu, Z. H., Zhang, L., Cheng, J. M., and Hu, T. M.: Long-term
fencing improved soil properties and soil organic carbon storage in an alpine
swamp meadow of western China, Plant Soil, 332, 331–337,
10.1007/s11104-010-0299-0, 2010.Wu, G. L., Liu, Y., Tian, F. P., and Shi, Z. H.: Legumes functional group
promotes soil organic carbon and nitrogen storage by increasing plant
diversity, Land Degrad. Dev., 10.1002/ldr.2570, online first, 2016.Zhu, H. H., Wu, J. S., Guo, S. L., Huang, D. Y., Zhu, Q. H., Ge, T. D., and
Lei, T. W.: Land use and topographic position control soil organic C and N
accumulation in eroded hilly watershed of the Loess Plateau, Catena, 120,
64–72, 10.1016/j.catena.2014.04.007, 2014.