Effects of artificial grassland establis

Plant Soil (2010) 333:469–479
DOI 10.1007/s11104-010-0363-9

REGULAR ARTICLE

Effects of artificial grassland establishment on soil nutrients
and carbon properties in a black-soil-type degraded
grassland
Gao-Lin Wu & Zhen-Heng Liu & Lei Zhang &
Tian-Ming Hu & Ji-Min Chen

Received: 12 October 2009 / Accepted: 22 March 2010 / Published online: 23 April 2010
# Springer Science+Business Media B.V. 2010

Abstract Disturbance and management approaches
can contribute significantly to restoration of degraded
grassland ecosystems. This study has examined the
re-establishment of artificial grassland to renew
extremely degraded black-soils in an alpine area of
the Qinghai-Tibetan Plateau, in China. We evaluated
this method for which grassland ecosystem responses


Responsible Editor: Tibor Kalapos.
G.-L. Wu : L. Zhang : J.-M. Chen
State Key Laboratory of Soil Erosion and Dryland Farming
on the Loess Plateau of Northwest A&F University,
Yangling 712100 Shaanxi, People’s Republic of China
G.-L. Wu : T.-M. Hu (*) : J.-M. Chen (*)
College of Animal Science & Technology
of Northwest A&F University,
Yangling, Shaanxi 712100, People’s Republic of China
e-mail: hutianming@126.com
e-mail: gyzcjm@ms.iswc.ac.cn
Z.-H. Liu
Maqu Alpine Grassland Workstation,
Maqu, Gansu 747300, People’s Republic of China
G.-L. Wu (*) : J.-M. Chen
State Key Laboratory of Soil Erosion and Dryland Farming
on the Loess Plateau, Institute of Soil and Water
Conservation of CAS&MWR,
No. 26 Xinong Road,

Yangling, Shaanxi 712100, People’s Republic of China
e-mail: gaolinwu@gmail.com

to this restoration approach are needed. Here, we
evaluated the response of aboveground plant communities and belowground soil nutrient and soil carbon
storage to the establishment of artificial grassland in
grasslands on black-soils in the eastern QinghaiTibetan Plateau. Three grasslands sites were selected:
a degraded grassland on an original black-soil, and 3and 6-year-old Elymus nutans artificial grasslands.
Artificial grassland establishment significantly improved aboveground biomass, but also significantly
decreased species richness, diversity and evenness for
black-soil-type degraded grassland. Artificial grassland establishment resulted in significantly improved
soil total nitrogen and phosphorus, and decreased soil
organic matter, available nitrogen, and phosphorus,
especially in the depth of 20–30 cm soil layer.
Although artificial grassland establishment significantly improved soil organic carbon in the topsoil
(0–10 cm), it decreased at depths of 10–20 and 20–
30 cm. Six-year artificial grassland significantly
increased soil carbon storage compared with blacksoil-type degraded grasslands. Accordingly, artificial
grassland can be used as effective restoration and
rehabilitation approach to improve productivity and

regulate community and soil properties in black-soiltype degraded grasslands. Our results suggest that
ecosystem functions such as production of aboveground biomass, the provision of soil surface cover,
and nutrient accumulation may be provided by
artificial grassland. However, more time is needed

470

for plant diversity and soil carbon storage functions to
recover fully from degradation.
Keywords Alpine grassland . Artificial grassland
establishment . Community . Soil carbon storage . Soil
properties . Succession

Introduction
Restoration of degraded grassland ecosystems has
become an increasingly important research subject,
not at least due to increasing problems associated
with ecosystem functioning, e.g., maintenance of
biodiversity and carbon sequestration (Tiessen et al.
1994; Neill et al. 1997). In China, 90% of grasslands

(3.99 billion ha) are degraded (Ren et al. 2007a), and
in recent years, alpine grasslands on the Tibetan
Plateau have also suffered from quite severe degradation. This has resulted in both a decline in herbage
yields and ecological quality of the environment,
with severe pest damage, species loss, desertification, wetland degradation, soil erosion, etc. (Hao
2008). Globally, grassland ecosystems play important roles both as sinks and sources of atmospheric
carbon with soils being the largest source of
uncertainty in the terrestrial carbon balance (Piao et
al. 2009). Grassland ecosystems can influence global
environmental change through their strong potential
for carbon and nitrogen sequestration (Wright et al.
2004). An important component of “disturbance”,
restoration and rehabilitation modes of natural
degraded grassland ecosystems has a potential to
alter not only the aboveground community, but also
belowground soil properties and the soil carbon-sink
function (Lal 2004; Wright et al. 2004; Piao et al.
2009). Wang et al. (2005) found that artificial
grassland establishment followed by fencing could
significantly enhance soil C and N concentrations in

alpine grassland. External disturbance can not only
accelerate succession of vegetation, but also renew
soil nutrient cycling and carbon storage (Schippers
and Joenje 2002). Accordingly, to counteract degradation, approaches, such as fencing, reseeding and/
or the use of fertilizers, control of rats, were
conducted to accelerate the restoration and rehabilitation process of degraded grassland ecosystems
(Akiyama and Kawamura 2007; Choi 2007; Wu et
al. 2009).

Plant Soil (2010) 333:469–479

However, none of these restoration and rehabilitation approaches have shown significant positive
effects on degraded grassland black-soils in alpine
areas of the Qinghai-Tibetan Plateau (Shang and Long
2007). This is largely a consequence of the special
and extremely degraded conditions of these soils
(Shang and Long 2007; Shang et al. 2008). Favorable
natural restoration approaches have been found to be
difficult to establish. Black-soil-type degraded grasslands, which range from 10 to 15 cm in depth, occur
after complete removal of surface layer by intensive

grazing and activities of rodents leaving the sub-soil
uncovered (Shang and Long 2007). In the cold season
especially, it is not covered with vegetation, which
leaves the soil bare and prone to erosion, while in the
warm season grasslands are covered by toxic weeds,
inedible for livestock (Shang and Long 2007). This not
only leads to ecological problems, but also greatly
reduces the productivity of those grasslands. The
common restoration and rehabilitation approach to this
degradation is an establishment of artificial and semiartificial grassland (Shang and Long 2007; Shang et al.
2008). Although more recent studies focus on effects
of different restoration and management on plant
species composition and diversity, soil properties and
soil carbon and nitrogen dynamics (Smith et al. 2000;
Burke 2001; Wright et al. 2004; Shang et al. 2008; Wu
et al. 2009), relatively little information is available on
artificial grassland establishment, which may be seen
as a stronger disturbance on natural grassland, affecting
soil properties and the soil carbon-sink function in a
black-soil-type degraded grassland ecosystem of the

Qinghai-Tibetan Plateau.
The present study, within the Maqu-pilot-project
“Returning to Grassland by Excluding Grazing”,
analyzed effects of artificial grassland establishment
on aboveground community properties, and belowground soil nutrient properties and soil carbon storage
were examined. Elymus nutans-grassland was the
most representative artificially established grassland
in the whole Qinghai-Tibetan Plateau. In this study,
we selected a black-soil-type degraded grassland and
a 3-year and 6-year artificial Elymus nutans-grassland. We hypothesized that establishment of artificial
grassland increases soil carbon storage. This study is
relevant to the restoration and rehabilitation of blacksoil-type degraded grassland, and is broadly relevant
to studies of plant community and soils in response to
ecosystem disturbance.

Plant Soil (2010) 333:469–479

Materials and methods
Study sites
This experiment was conducted in alpine meadow at

3,500 m a.s.l. at Manrima (33°42′21″N, 102°07′02″
E) in Gansu Province, PR China, which is located at
the eastern Qinghai-Tibetan Plateau. The mean
annual temperature is 1.2°C, ranging from −10°C
in January to 11.7°C in July, with about 270 frost
days. The mean annual precipitation is 620 mm,
with a main rain period during a short, cool summer.
The annual cloud-free solar radiation was about
2,580 h (Wu et al. 2009). The vegetation is typical
alpine meadow and is dominated by clonal grasses
(Festuca ovina, Poa poophagorum, Roegneria
nutans, Agrostis sp., Kobresia sp., grasses and
sedges) and forbs (Saussurea sp., Asteraceae and
Anemone rivularis, Ranunculaceae).
In this study, we selected a highly degraded blacksoil-type grassland, in the alpine area of the QinghaiTibetan Plateau, which was dominated by Potentilla
anserina L. and Helenia corniculata (L.) Cornaz and
some other subordinate species.

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establishment of Elymus nutans. Each grassland plot
was about 0.5 ha and comprised five sampling plots
(30 m×30 m) (Fig. 1). Plots were separated by fences
with a partition section of 20 m. Artificial grassland
plots were excluded from livestock grazing with
fencing during the plant growth seasons from April
to October, and slight grazing was provided for
Tibetan sheep and yaks (1.3 individuals per hectare
with a ratio sheep vs yaks of 2:1) only during the haystage in winter. In each of the five sampling plots of
the three grassland types, we established five diagonal
sampling quadrats (1 m×1 m) (Fig. 1).
Vegetation sampling

In this study, we compared three grasslands: a blacksoil-type degraded, and 3-year and 6-year artificial

All plant species composition samples were taken
from five quadrats from every sampling plot, when
peak biomass was reached (early September 2008).
The experiment contained a total of 75 quadrats. The
density, frequency and biomass of each species in

each quadrat were counted separately. Total aboveground biomass, species richness, and abundance of
each quadrat in three grassland types were measured.
Every shoot was counted for each species, clipped
and put in marked paper bags per species per quadrat.
We determined the total dry biomass in every quadrat
by weighing the plants after drying at 80°C for 48 h
to a constant weight. The mean number of shoots in
sampling plots represented the abundance of the

Fig. 1 Field experiment setup and sampling arrangement.
Three grassland types were contained (black-soil-type degraded
grassland CK, 3-year artificial grassland 3-y AG, and 6-year
artificial grassland 6-y AG) and five sampling plots (30 m×

30 m) were selected , respectively, in each type, and five
quadrats (1 m×1 m) were determined for community investigation and soil sampling collection in each sampling plot. A
total of 75 quadrats were included in this study

Experimental design


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Plant Soil (2010) 333:469–479

community. Shannon-Wiener diversity index (H) and
Evenness index (E) of the three grassland types
communities were calculated as:
Richness index (R):

R=S

Shannon-Wiener diversity index (H):
s
P
H ¼ − ðPiln PiÞ;

Data analysis

i¼1

Evenness index (E):

The content of each nutrient trait calculated by the
proportions of soil organic matter, total nitrogen,
available nitrogen, total phosphorus and available
phosphorus account for air-dry weight of soil samplings.

E ¼ lnHS ;

where S is the total species numbers of meadow
community, H is the Shannon-Wiener diversity index
and Pi is the abundance proportion of i species.
Soil sampling
We collected five soil samples at different soil depths
(from 0∼10 cm, 10∼20 cm and 20∼30 cm respectively) using a bucket auger from each quadrat and every
sampling plot in the three grassland types in a
diagonal pattern. Soil samples at the same depths in
each sampling quadrat were mixed. Then, 25 mixed
soil samples from each soil depth in each plot were
used to analyze soil properties and soil carbon
storage. All soil samples were air-dried and then
passed through a 0.14-mm sieve. Soil pH was
determined using a soil–water ratio of 1:5. Soil
organic matter was measured using the WalkleyBlack acid digestion method by K2Cr2O7 (Soil
Science Society of China 1983). Soil total nitrogen,
available nitrogen, total phosphorus and available
phosphorus were measured by the methods of Miller
and Keeney (1982) in the laboratory. The organic
carbon content in the soil samples were determined by
wet oxidation with potassium dichromate (K2Cr2O7)
and dry combustion with a carbon analyzer using a
Mebius method by the Walkley-Black acid digestion
(Nelson and Sommers 1982). We calculated the total
soil organic carbon storage density (TSOC, g cm−2)
by the method of He et al. (2008) on a ground area
basis up to a 30-cm depth as follows:
X
Di  Pi  OMi  S
TSOC ¼

where Di, Pi, OMi, and S represent, respectively, the
soil thickness (cm), bulk density (g cm−3), organic
carbon concentration (%), and cross-sectional area
(cm-2) of the ith layer; i=1, 2, and 3.

Data is expressed as mean±standard error of mean.
The soil sample data for the 0–10-cm, 10–20-cm and
20–30-cm soil layers were used to analyze the soil
properties and soil organic carbon storage potentials
of the three grassland types. To assess the effects of
establishment time of artificial grassland on soil depth
and their interaction on soil properties and soil
organic carbon, an LSD tests for significance (P<
0.05) of between-subjects effects were conducted with
two-way ANOVA of General Linear Model (GLM)
for soil properties and soil organic carbon among
three grassland types and three soil depths. To assess
the effect of establishment time of artificial grassland
on community properties and soil carbon storage,
one-way ANOVA analyses were conducted for
vegetation community characteristics and soil carbon
storage among three grassland types. All statistical
analyses were performed using the software program
SPSS, ver. 13.0 (SPSS, Chicago, IL, USA).

Results
Response of plant community and soil nutrient
properties
Artificial grassland establishment significantly increased aboveground biomass, but also significantly
decreased species richness, diversity and evenness for
black-soil-type degraded grassland (Fig. 2; Table 1).
As for soil nutrient properties among black-soil-type
grassland, 3-year and 6-year artificial grasslands,
there were significant effects of grassland type, soil
depth and their interaction on soil pH, soil organic
matter, soil total nitrogen, soil available nitrogen, soil
total phosphorus, and soil available phosphorus in this
study (Table 1). Artificial grassland had a lower soil
pH, soil available phosphorus and higher soil total
nitrogen than black-soil-type grassland throughout
different soil depths in this study (Fig. 3a, d, f). For
soil organic matter and soil total nitrogen, 3-year and
6-year artificial grasslands were both significantly

Plant Soil (2010) 333:469–479

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Fig. 2 Effect of artificial grassland planting on aboveground
biomass (a), species richness index (b), Shannon-Wiener
diversity index (c) and Evenness index (d) of grassland
community. Values (±SE) are means of 25 quadrates for

black-soil-type degraded grassland (CK), 3-year artificial
grassland (3-y AG) and 6-year artificial grassland (6-y AG).
Different letters indicate significant differences at P