Plant species effects on soil carbon and

Plant Soil
DOI 10.1007/s11104-011-0822-y

REGULAR ARTICLE

Plant species effects on soil carbon and nitrogen dynamics
in a temperate steppe of northern China
Lili Jiang & Xingguo Han & Ning Dong &
Yanfen Wang & Paul Kardol

Received: 18 October 2010 / Accepted: 5 May 2011
# Springer Science+Business Media B.V. 2011

Abstract We evaluated plant species effects on soil
carbon (C) and nitrogen (N) dynamics in a steppe
ecosystem of northern China. In two subsequent years,
we measured soil properties in the top 10 cm of the soil
under replicated mono-dominant plant patches in two
sites that differed in land-use history: a cultivated site
(old field) and an uncultivated site (steppe). Both in the
cultivated site and the uncultivated site, we selected

patches of three of the dominant plant species. Contrast
analyses in ANOVA showed that soil organic carbon
(SOC) and total N content (g per m2) was on average
lower in the cultivated site than in the uncultivated site.
On average, soil respiration was also lower in the
cultivated site than in the uncultivated site. However,
overall differences in soil C and N dynamics between

Responsible Editor: Hans Lambers.
L. Jiang : N. Dong : Y. Wang
College of Resources and Environment,
Graduate University of the Chinese Academy of Sciences,
19 Yuquanlu,
Beijing 100049, China
L. Jiang : X. Han (*) : N. Dong
State Key Laboratory of Vegetation and Environmental Change,
Institute of Botany, Chinese Academy of Sciences,
Xiangshan,
Beijing 100093, China
e-mail: xghan@ibcas.ac.cn

P. Kardol
Department of Forest Ecology and Management,
Swedish University of Agricultural Sciences,
901 83 Umeå, Sweden

the cultivated site and the uncultivated site (if existing)
were generally small compared to the effects of
individual plant species. Soil respiration differed
among plant species in the cultivated site, but not
in the uncultivated site. In contrast, SOC content,
total N, and N mineralization rate differed among
plant species in the uncultivated site, but not in the
cultivated site. Mineralization and nitrification rates
strongly varied among the dominant plant species,
particularly in the uncultivated site. Variation in both
C and N pools and fluxes could be best explained by a
combination of plant biomass, litter, and soil microbial and micro-climatic parameters. Cultivation can
directly affect soil C and N dynamics. However,
importantly, our data suggest that indirect effects
through changes in plant species composition are

also important, and probably strongly interact with
direct effects in affecting soil C and N dynamics after
land-use change. Hence, evaluation of land-use history
on soil C and N dynamics requires integral analyses of
changes in plant community composition.
Keywords Cultivation . Carbon sequestration .
N-mineralization rate . Old-field . Restoration . Soil
carbon and nitrogen . Soil respiration . Succession

Introduction
In northern China, steppe is a dominant form of
landscape and an integral component of the Eurasian

Plant Soil

continent, in 2001 covering a total of 4×106 km2
(National Statistics Bureau of China 2002). Steppe
plays important roles in servicing the ecological
environment and socio-economics of the region.
Since the mid 1950’s, about 4.8% of the steppe area

was claimed for agriculture. In recent years, more
than 10% of former agricultural land has been
restored to grassland or forest (Ministry of Environmental Protection 2004). Change of land use will
have important implications for local and global
biogeochemical cycles and local vegetation dynamics (Foster et al. 2003; Degryze et al. 2004). For
example, soils may act as a source or sink of carbon
dioxide (CO2) in exchange with the atmosphere;
soils contain a large stock of soil organic carbon
(SOC), and slight changes in SOC stock represent
large CO2 fluxes (Krogh et al. 2003). Thus understanding effects of land use change on biogeochemical cycles is of high importance in predicting future
atmospheric CO2 levels (IPCC 2001).
Cultivation of grassland and steppe has caused
large losses of soil carbon and nitrogen (Wu and
Tiessen 2002; McLauchlan 2006; Wang et al. 2009).
For example, short-term cultivation has been shown
to increase soil respiration because of improved
conditions for decomposition of soil organic matter,
such as increased soil aeration and moisture content,
and disruption of soil aggregates, exposing stable,
adsorbed organic matter to microbial activity (Six et

al. 1998). However, the loss of organic matter in soil
means depletion of substrates for soil respiration
(Luo and Zhou 2006), which indicates that on the
long term effects of cultivation may be difficult to
predict.
On the other hand, changes in soil nitrogen
mineralization rate after agricultural abandonment
are still not very well understood and may be
context-dependent (Grandy and Robertson 2006).
For instance, some studies showed highest N mineralization rates in early secondary succession (Baer et
al. 2002; Camill et al. 2004) while others found that
net nitrogen mineralization increased with time after
abandonment (Angus et al. 2006; Fraterrigo et al.
2006). Differences in historical management could be
one of the reasons why shifts in nitrogen mineralization rate after land-use change vary from site to site
(e.g., Vitousek et al. 1989). For example, historical
manure inputs may stimulate soil net nitrification
rates (Compton and Boone 2000).

Historical land use explains part of the variation

and distribution in present vegetation (Matlack 1994;
Motzkin et al. 1996). Importantly, variation in plant
dominance patterns may affect patterns of soil C and
N accumulation and cycling rates (Bardgett et al.
1999; Camill et al. 2004; Ehrenfeld et al. 2005; Angus
et al. 2006; Fraterrigo et al. 2006). For example,
plant-induced variation in soil C has been demonstrated in a shortgrass steppe ecosystem (Burke et al.,
1999). Camill et al. (2004) found that the increase of
soil C mineralization rates and decrease of soil N
mineralization rates were correlated with the increase
of C4 grasses during secondary grassland succession.
However, so far, little is known about the importance
of shifts in dominant plant species after land use
change on soil carbon and nitrogen dynamics.
Former studies have evaluated the relative
importance of land-use history and plant species
effect on soil properties and processes using a full
factor design (Burke et al. 1999; Compton et al.
1998). However, land-use history may select for
plant species with particular functional traits (De

Deyn et al. 2008), and the dominant plant species
generally vary with land use history. Hence, a full
factor design often does not realistically reflect the
combined effect of plant species and land use history
on soil properties. Therefore, we used a nested
design (i.e., plant-species nested within land-use) to
explore soil C and N dynamics in a previously
cultivated old-field and in a typical steppe that was
not cultivated. We compared variation in soil C and
N parameters (top 10 cm of the soil profile) among
plant species within the cultivated site and uncultivated site with the overall variation between the
cultivated site and uncultivated site.
Historically, the main disturbance of steppe ecosystems in northern China resulted from low-intensity
grazing by antelopes and rabbits, and wildfire (Zhou
et al. 2007). After economic reforms began in the late
1970’s, large areas of steppe were converted to crop
land, or to grazing systems. In this study, we selected
two sites that used to be part of the same steppe
ecosystem: an old-field that was abandoned from
agriculture in 2001, and a steppe site which had been

grazed by cattle and sheep until 2001, but still could
be considered as typical steppe. Plant dominance
patterns differed between the two sites; the cultivated
site was dominated by early-successional pioneer
species, while the steppe was dominated by K-

Plant Soil

strategic plant species adapted to stable environmental
conditions (see Jiang et al. 2010).

Methods
Study site
This study was conducted in Duolun County (42°02′N,
116°17′E, 1,324 m a.s.l.), Inner Mongolia, China.
Mean monthly air temperature ranges from −17.5°C
in January to 18.9°C in July, with a mean annual
temperature of 2.1°C. Mean annual precipitation
(1958–2008) is 380 mm; 67% falls from June to
August. The annual precipitation in 2007 (198 mm)

was among the lowest values of the last 50 years,
while the annual precipitation in 2008 (370 mm)
was among the highest values of the last 50 years.
The soil is classified as chestnut soils (Chinese
classification) or Calcicorthic Aridisol in the USA
Soil Taxonomy classification, with 63% sand, 20%
silt, and 17% clay and mean pH is 6.84.
Experimental design
Within the research area, we selected an old-field
(abandoned for 5 years; previously cultivated with
Chinese oat, Avena chinensis) (hereafter referred to as
the ‘cultivated site’) and, adjacent to the cultivated
site, a typical steppe site (hereafter referred to as the
‘uncultivated site’). The cultivated and uncultivated
sites used to be part of the same steppe area. Before
1978 the grassland area was not managed and the
major disturbance resulted from antelope and rabbit
grazing, and wildfire. Since the economic reforms and
open-door policy in 1978, lands were opened to
private use. The intensive farming, grazing and

subsequent land-use changes resulted in reduced area
of typical grasslands and severe land degradation
Table 1 Plant species
beneath which soil samples
were collected (from Jiang
et al. 2010)

(Yuan et al. 2005, 2006). Since 1997, bans on grazing
and farming have been carried out by the local
government; e.g., the local government implemented
the “Fence” project for grazing (e.g., grazing-free)
and the “Grain for Green” project for farming
(converting low-yield farmland to forest and pasture).
The overall aim of these projects is to control soil
erosion and combat desertification by restoring forest
or grassland vegetation on degraded and ‘desertified’
land (Chen et al. 2009). Both in the cultivated and the
uncultivated site mono-dominant plant species
patches commonly occur (Jiang et al. 2010).
We selected mono-dominant plant patches for three

of the dominant species at each of the two sites
(Table 1), and we established 2×2 m plots in each
patch. At the cultivated site we selected patches of
Artemisia capillaris (Art cap; C3 forb), Artemisia
lavandulaefolia (Art lav; C3 forb), and Pennisetum
centrasiaticum (Pen cen; C4 grass) which are typical
species in abandoned agricultural land in northern
China (Zhang 2005; Wang et al. 2009). At the
uncultivated site we selected patches of Artemisia
frigida (Art fri; C3 forb), Leymus chinenses (Ley chi;
C3 grass), and Stipa krylovii (Sti kry; C3 grass) which
are typical dominant plant species in steppe in this
region (Bai et al. 2004). For each plant species we
selected six randomly replicated patches which were
at least 2 to 3 m apart from each other. Across all
plant species, the patches were randomly distributed
in the cultivated and uncultivated site, and all patches
were distributed within 60 m. The soils in the study
area are homogeneous (Jiang et al. 2010); hence, the
pattern of historical land-use depended on ownership
boundaries rather than on inherent soil properties.
Root, shoot, and litter biomass
We used a root in-growth method to determine
belowground net primary production (BNPP). In

Plant species

Site

Species code

Family

Life form

Artemisia capillaris
Artemisia lavandulaefolia
Pennisetum centrasiaticum
Artemisia frigida
Leymus chinenses
Stipa krylovii

Cultivated
Cultivated
Cultivated
Uncultivated
Uncultivated
Uncultivated

Art cap
Art lav
Pen cen
Art fri
Ley chi
Sti kry

Asteraceae
Asteraceae
Poaceae
Asteraceae
Poaceae
Poaceae

perennial
perennial
perennial
perennial
perennial
perennial

forb
forb
grass
forb
grass
grass

Plant Soil

April 2007 and 2008 respectively, in each plant patch,
we collected two 40 cm-depth soil cores using an
8 cm diameter soil core sampler. We washed the roots
from the soils over a 2 mm sieve, oven-dried the roots
at 70°C for at least 48 h, and then weighed biomass.
After that, the root-free soils were placed back into
the hole they were collected from. We then collected
roots in late October in 2007 and 2008, respectively,
by using a 6 cm diameter soil core sampler at the
center of the original root in-growth holes. The roots
were washed from the soils, oven-dried at 70°C for at
least 48 h, and weighed as BNPP. In August 2007 and
2008, at peak standing biomass, all living plant tissue
as well as the litter was collected from two 1 m×
0.15 m rectangular subplots in each patch. Plant
material and litter was oven-dried at 70°C for at least
48 h prior to being weighed. Plant material was
analyzed for C and N concentration.
Soil analyses
In August in 2007 and 2008, three soil cores
underneath each plant patch were collected using a
metallic tube (10 cm in height and in 6 cm diameter).
For each plant species, the three cores were bulked
and air-dried for measurements of SOC and total soil
N (see below).
Soil respiration – In August 2007 and 2008, a LI8100 portable soil CO2 fluxes system (Li-Cor, Inc.,
Lincoln, NE, USA) was used to measure soil respiration. Soil respiration was measured once a week
between 2:00 PM and 4:00 PM. One PVC collar
(11 cm in diameter and 5 cm in height) was
permanently inserted 2–3 cm into the soil at the center
of each plot. Measurements were taken by placing the
LI-8100 chamber on the PVC collars for 1–2 min.
Living plants inside the soil collars were removed by
hand at least one day before the measurement to
eliminate aboveground plant respiration.
Soil net N mineralization – We used a PVC cores
method (Raison et al. 1987; Hook and Burke 1995) to
measure N mineralization. Briefly, in May, July and
August 2007 and 2008, in each plant patch, two PVC
tubes (5 cm diameter×12 cm long) were placed 10 cm
into the ground. The PVC tubes were covered with
plastic film to prevent water penetration and allow gas
exchange. Prior to inserting the tubes, the litter was
removed; litter was placed back after the PVC tubes
were installed. Simultaneously, using similar PVC

tubes, two soil samples were collected in adjacent
locations; the two samples were bulked and mixed
and sieved through a 2-mm mesh. Subsamples were
used to measure initial content of inorganic N (NH4+N and NO3--N), indicated as SInNI (SNO3-NI and
SNH4+NI). After incubation for one month, the PVC
tubes were collected, and soil inorganic N was
measured, indicated as SInN F (SNO 3 - N F and
SNH4+NF). Net N mineralization (Rmin), nitrification
(Rnit) and ammonification (Ramm) rates were calculated as (SInNF - SInNI)/T, (SNO3-NF - SNO3-NI)/T and
(SNH4+NF - SNH4+NI)/T, where T was the incubation
period in days (Turner et al. 1997).
Soil temperature, moisture, and bulk density – In
each plant patch, adjacent to the PVC tubes soil
temperature was measured twice in August 2007 and
in August 2008. Soil temperature was measured at
10 cm depth using a thermocouple probe (Li-8100-201)
connected to the LI-8100 at the same time of soil
respiration measurements. One soil core (3 cm diameter,
10 cm depth) was collected weekly in each plant patch
in May, July, and August 2007 and 2008, and then dried
for 48 h at 105°C to determine soil moisture content.
Soil bulk density was determined in August 2007 using
a coring method (for details, see Wang et al. (2008)).
Plant, litter, soil, and microbial C and N – Plant C, and
SOC content (g kg−1) were analyzed using a H2SO4K2Cr2O7 oxidation method (Nelson and Sommers
1982). We calculated SOC and total N concentration
(g cm−3) as: SOC (or total N) concentration = Oi × Bi ×
103, where Oi is the mean SOC (or total N) content
(g kg−1) in the upper 10 cm of the soil profile. Bi is the
bulk density (g cm−3). Total N was analyzed using a
Kjeldahl digestion method with an Alpkem autoanalyzer (Kjektec System1026 Distilling Unit, Sweden).
NO3--N and NH4+-N was extracted with 2 M KCl.
Statistical analysis
We analyzed soil and plant properties using two-way
analysis of variance (ANOVA) with year (2007, 2008)
and plant species (Art cap, Art lav, Pen cen, Art fri,
Ley chi, Sti kry) as fixed factors. When significant
plant species effects were observed, Duncan’s hsd
posthoc tests were used to test for differences among
species. A priori contrasts were specified for testing
overall, across-year differences between plant species
from the cultivated site and plant species from the
uncultivated site. To determine those factors that best

Plant Soil

explained variation in soil C and N dynamics across
plant patches in the cultivated and in the uncultivated
site, we used stepwise multiple regressions, including
mean August temperature and soil moisture, plant C,
N and C/N, litter C, N and C/N, shoot biomass, root
biomass, BNPP, litter biomass, and microbial biomass
C, N and C/N. Linear correlations were run to test for
relationships of soil temperature and soil moisture with
soil inorganic N, nitrification rate, and ammonification
rate. We ran regression analyses separately for 2007 and
2008, and separately for the cultivated site and the
uncultivated site. For all ANOVAs, the assumption of
normality was checked with Kolmogorov-Smirnov tests
and the assumptions of homogeneity of variances were
checked using Levene’s test. If the assumptions were
not met, data were log-transformed prior to analysis.
Statistical analyses were performed using SPSS, version
15.0 (SPSS Inc, Chicago, Illinois).

SOC
SOC content (g kg−1) was on average a little higher in
the uncultivated site than in the cultivated site. However,
SOC content strongly varied depending on the plant
species beneath which the soils were collected (Fig. 1A),
and plant species explained more of the variation in
SOC content than did cultivation history (Table 2). SOC
content did not differ significantly between 2007 and
2008, and no significant interactive effects of year and
plant species were observed (Table 2). None of the plant
or soil parameters correlated significantly with SOC
content in the cultivated site, while in the uncultivated
site there was a negative correlation with microbial
biomass C/N in 2007 and a positive correlation with soil
moisture in 2008 (Appendix 1).

2008
Cultivated site

A a

SOC (g kg-1)

Uncultivated site

A

15

2.0

B
C b

10

C

bc

C b

C

c

C c

2.5

B

A a

a

B b

1.5

C c
D d

D c

1.0

5

0.5

SOC (g cm-3)

0
15

A
B b

a

BC

dc

A a

BC

C de

B b

D e

10

B bc

B c

B c

2.0

C d

1.0
5
0

F

E
Respiration
(µmol m-2 s-1)

0.0

D

C

dc

0.0

a

10

5

a

B c

A bc

A

A

ab

a

ab

AB

Art cap

b

b

a

0.2

c

Art lav Pen cen

Art fri

Ley chi

0.4

A

A

0

ab

Sti kry

Plant species
Fig. 1 Mean soil organic carbon (SOC) (A) and total N (B)
content (g kg−1), SOC (C) and total N (D) concentration (g m−3),
soil respiration rate (E) and soil net N mineralization rate (F)
(means ± SE; N=6) for soils (0–10 cm depth) under different
plant species within land use histories (cultivated and uncultivated). Date (mean ± s.e.) are shown for 2007 and 2008.

Art cap

A

A

Art lav Pen cen

A
Art fri

Total N (mg kg-1)

Uncultivated site

Total N (mg cm-3)

20 Cultivated site

Rmin (mg kg-1 d-1)

2007

Results

B
Ley chi

Sti kry

0.0

Plant species
Uppercase and lower case letters indicate significant differences
among species (Duncan’s hsd posthoc tests, P

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