Introduction
Grassland
is an important part of the terrestrial ecosystem, and it is a comprehensive
natural body composed of grass and its living land (Jiang et al.
2016). The total area of grassland in China is 3.9×108 ha, accounting for 13% of the world’s grassland area and about 41% of the
national land area. It is the largest ecosystem in China's land area. It is not
only an important animal husbandry production base, but also an important
ecological barrier, which plays an important role in the global ecosystem
balance. In recent years, destructive activities such as artificial reclamation of
grasslands have been increasingly intensified because of the one-sided pursuit of economic benefits. The grassland ecosystem in
China, whether in southern or northern, has experienced extensive widespread grassland degradation, desertification, and even ecosystem imbalances (Xiang et al. 2019; Yang et al.
2019).
At present, as an artificial alternative to grazing, mowing
is the most common and extensive way of grassland utilization. A large number of studies on the effects of mowing on grassland have
been carried out at home and abroad (Dyke et al. 2004; Field et al. 2008;
Valliere et al. 2019). It
can affect the interception of light by species with a higher spatial position,
change the growth response of inherent plants to existing resources and the
intensity of interspecific
competition and then modify the community structure and species composition (Staalduinen et al.
2010a; Bernhardt-Römermann et al. 2011; Wan 2014). Moderate mowing can
increase species diversity and maximize the use of resources (Ljubicic et al. 2014), which helps to increase species diversity and productivity, but the
effects of mowing to varying degrees on productivity and diversity are
different (Yamauchi and Yamamura 2004; Hooper et al. 2005). Grasslands in different habitats have different responses to mowing due
to the influence of community types, climatic conditions and soil properties.
Compared with typical steppe, meadow steppe and desert steppe, there are few
studies on the effect of mowing on grassland in a wetland habitat.
The Tian-E Island Elk Reserve is a national
nature reserve with the main purpose of
ex situ protection of elk, which
has a typical wetland habitat. Its unique
geographical, hydrological, and climatic
conditions make it a paradise for many endangered animals (Peng
and Zhao 2004). In recent years, due to the increase of the elk
population, the opening of wetlands and climate change, the wetlands in the reserve have been significantly degraded (Wen et al. 2012). As a favourite species of elk and a constructive species in the
reserve, C. argyi grassland is
mainly managed by mowing; however, information about the effects of
mowing on C.
argyi grassland community
structure and soil characteristics is lacking. Therefore, this study was
conducted to evaluate the role of mowing frequency
on community characteristics and soil properties of C. argyi grassland to find the
appropriate mowing frequency to maintain the sustainable utilization of grassland and provide
natural forage for elk better in the reserve.
Materials and Methods
Research area
The
study area is located in the Tian-E Island Elk
National Nature Reserve in Shishou city, Hubei Province, China (E112°33', N29°49'), which
covers an area of 1567 ha, and the core area is
about 1167 ha. The average altitude is 35 m, of which the highest point is 38.44 m,
the lowest point is 32.91 m, and the relative height difference is not obvious.
It is a subtropical monsoon climate area, with hot summer, dry and cold winter
climate, distinct seasons and abundant rainfall. On the other hand, the annual
average temperature in those areas is 16.5°C, with 28.5°C in the hottest month
(July) and 3.5°C in the coldest month (January). The annual precipitation is
more than 1200 mm, rainy in spring, early summer and late autumn. The average
annual relative humidity is 80%. The frost-free period lasted for 261 days. The
main trees and herbaceous plants in this region are Populus nigra, Salix matsudana, Melia azedarace, Phragmites communis, Miscanthus
saccharifloru,
Carex argyi, and Roegneria kamoji.
Field and laboratory studies
In 2018, research was started in the
wetland environment of Tian-E island natural reserve
located in Shishou, Jingzhou,
and found that: as a favourite species of elk and a constructive
species in the reserve, some C. argyi lawns in the reserve are growing well, while some
are stunted. After asking the staff of the reserve, we learned that there is no
other management except mowing in routine maintenance. A preliminary experiment
was conducted from April to May. At that time, control group without mowing was
set up, and the other two treatments were mowing once and two times,
respectively. The results showed that mowing decreased the aboveground biomass, density, sand proportion, as well as
the contents of soil organic matter and soil nutrients.
In 2019, the mowing frequency was increased and the experimental design was improved by adopting a randomized
complete block design and replicated three times. For that randomly selected 15
plots of grassland with net plot size of 2 m × 3 m were
used, and borders
were defined by natural barriers. Four different mowing
treatments with mowing once (M1), mowing 2 times (M2), mowing 3
times (M3), mowing 4 times (M4), and the control without
mowing (M0) were used.
By artificial cutting, all the aboveground parts of the plants in the plot that
needed to be mowed were processed and removed from the base at a time. The mowing treatment was begun on March
6th, and completed on June 6th,
with a
one-month interval of each mowing.
On October 6th,
2019, the community characteristics of each treatment plot were investigated in
the field, and soil samples were also collected for further analysis. Three
sample plots with an area of 50 cm × 50 cm were randomly selected in each
treatment plot to determine the plant species composition, plant height, plant
number, and coverage. Plants of all three sample plots in each treatment plot
were mowed from the base and collected into marked plastic sealed bags, and
then they were taken back to the laboratory of the Yangtze University to weigh
fresh, and dried at 85°C for 48 h to the constant weight to weigh the dry
weight.
The soil texture was
determined by American soil particle size rapid method (Zhang and Wang 2002), soil organic matter
was determined by potassium dichromate volumetric method-dilution thermal
method, the available nitrogen was determined by alkali hydrolysis diffusion
method, the available phosphorus was determined by ammonium carbonate
soaking-molybdenum antimony sulfate colorimetric
method, available potassium was determined by Flame Spectrophotometry (Bao 2008).
Statistical analysis
All
collected data were analysed using one-way ANOVA to check the overall
significance of data while Duncan's new multiple range test were performed
using SAS 9.0 software to separate treatments means at P ≤ 0.05, and the graphs were prepared using Microsoft Excel
program 2003.
The variation of community characteristics
With the
increase of mowing frequency, both fresh weight and dry weight of the
aboveground biomass decreased significantly (P < 0.05). Compared
with the control treatment, the fresh weight and dry weight of aboveground
biomass decreased by a minimum of 1.4 and 10.2% under M1, and by a
maximum of 60.5 and 74.7% under M4 (Fig.
1).
With increase in mowing frequency, the community density decreased significantly (P < 0.05). Compared
with the control treatment, the community density decreased by a minimum of
19.1% under M3, and by a maximum of 31.9% under M2, but there was no significant difference among different
mowing treatments except M3 (Fig. 2).
The variation of community diversity
Fig. 1: Effect of different
mowing frequency on the aboveground biomass of C. argyi grassland
M0 represents the
treatment without mowing. M1, M2, M3 and M4
represent the treatment with mowing one, two, three, four times, respectively.
FW and DW represent the fresh weight and dry weight, respectively. Different
capital letters denote significant differences in fresh weight, while different
lowercase letters denote significant differences in dry weight (P < 0.05)
Fig. 2: Effect of
different mowing frequency on the community density of C. argyi grassland
M0 represents the
treatment without mowing. M1, M2, M3 and M4
represent the treatment with mowing one, two, three, four times,
respectively. Different lowercase letters denote significant differences among
treatments (P < 0.05)
With the
increase of mowing frequency, the community diversity
indices all increased significantly (P < 0.05). Compared
with control treatment, the Margarlef, Simpson, Shannon-Wiener and Pielou indices
were increased
by a maximum of 88.8, 24.1, 58.8 and 26.2% under M4, respectively. Among the different mowing frequencies,
the Shannon-Wiener index of M2 was significantly lower than that
of the other treatments, and the other indexes were not significantly
different (Table 1).
The variation of soil particle proportion
With increase of
mowing frequency, the sand proportion in each soil layer of 0–30
cm increased
significantly (P < 0.05), except the sand proportion under M1 and M4 were lower
than that under M0 in the 0–10 cm soil layer. Compared with the
control treatment, the sand proportion increased
by a maximum of 26.0% under M3, and decreased by a
maximum of 9.2% under M4 in the 0–10 cm soil layer (Table 2).
With the increase of mowing frequency, it has no significant effect on the silt proportion
in the 0–30 cm soil layer (Table 2). With the
increase of mowing frequency, the clay proportion in
each soil layer decreased significantly (P < 0.05). Compared
with control, the clay proportion was
decreased by a minimum of 16.1% under M4, and by a maximum of 52.3%
under M2 in the 0–10 cm soil layer. The changing trend of clay proportion was consistent in each soil layer of 0–30 cm (Table 2).
The variation of soil nutrient
element content
With the increase of
mowing frequency, the soil organic matter decreased insignificantly in the 0–20
cm soil layer (Table 3). Compared with control, the soil organic matter was
decreased by a maximum of 7.7% under M4 in the 0–10 cm soil layer.
With the increase of mowing frequency and soil depth, the content of available
nitrogen, available phosphorus and available potassium all had a significant
decreasing trend (P < 0.05),
except the available nitrogen decreases insignificantly in the 0–10 cm (Table 3).
Compared with control, the available nitrogen content
were decreased by a maximum of 8.2% under M1, but the difference
among different mowing frequencies was not significant in 0–10 cm soil layer.
However, the available phosphorus contents were decreased by a minimum of 1.5% under
M1, and by a maximum of 51.5% under M4. Likewise, available potassium contents were also decreased by a minimum of 21.5%
under M3, and by a maximum of 32.2% under M1 in 0–10 cm
soil layer (Table 3).
Table 1: Effect of
different mowing frequency on the diversity index of C. argyi grassland
Mowing events |
Margarlef index |
Simpson index |
Shannon-Wiener index |
Pielou index |
M0 |
0.98 ± 0.09b |
0.58±0.03b |
1.31 ± 0.12d |
0.65 ±0.03b |
M1 |
1.75 ± 0.05a |
0.77±0.03a |
1.93 ± 0.05ab |
0.78 ±0.07a |
M2 |
1.40 ± 0.07ab |
0.72±0.05a |
1.72 ± 0.09c |
0.75 ±0.02a |
M3 |
1.81 ± 0.04a |
0.72±0.06a |
1.85 ± 0.12bc |
0.72±0.03ab |
M4 |
1.85 ± 0.18a |
0.80±0.04a |
2.08 ± 0.05a |
0.82 ±0.08a |
M0 represents the
treatment without mowing. M1, M2, M3 and M4
represent the treatment with mowing one, two, three, four times, respectively.
Within each column, different lowercase letters denote significant differences
among treatments (P < 0.05)
Table 2: Effect of
different mowing frequency on soil particle content
Soil particle types |
Mowing events |
Depth of soil |
||
0–10 cm |
10–20 cm |
20–30 cm |
||
|
M0 |
30.49±1.90bc |
9.43±0.45c |
7.35±0.42d |
|
M1 |
27.96±0.79c |
11.70±0.02b |
8.31±0.23cd |
Sand (%) |
M2 |
32.71±1.86b |
12.93±0.96b |
9.86±0.77b |
|
M3 |
38.41±1.08a |
19.65±1.90a |
10.42±0.79a |
|
M4 |
27.68±2.05c |
11.61±0.97b |
9.15±1.03bc |
|
M0 |
59.79±4.32ab |
82.71±7.15a |
86.09±2.68a |
|
M1 |
64.86±3.05a |
82.62±6.18a |
87.81±1.92a |
Silt (%) |
M2 |
62.65±4.11ab |
84.03±5.34a |
86.86±5.63a |
|
M3 |
56.84±1.45b |
76.35±1.08a |
86.43±1.48a |
|
M4 |
64.15±5.69a |
81.94±1.35a |
85.10±3.13a |
|
M0 |
9.72±0.86a |
7.85±0.53a |
6.57±0.46a |
|
M1 |
7.18±0.12c |
5.68±0.38c |
3.88±0.32c |
Clay (%) |
M2 |
4.64±0.21d |
3.04±0.04e |
3.29±0.18d |
|
M3 |
4.75±0.18d |
4.01±0.38d |
3.15±0.11d |
|
M4 |
8.16±0.70b |
6.46±0.43b |
5.75±0.13b |
M0 represents the
treatment without mowing. M1, M2, M3 and M4
represent the treatment with mowing one, two, three, four times, respectively
Within each column, different
lowercase letters denote significant differences among treatments (P < 0.05)
Table 3: Effect of
different mowing frequency on soil nutrient element
content
Nutrient types |
Mowing Events |
Depth of soil |
||
0–10 cm |
10–20 cm |
20–30 cm |
||
Organic matter (g kg-1) |
M0 |
79.18 ± 4.47a |
24.42 ± 1.60a |
12.96 ± 0.99b |
M1 |
77.20 ± 7.53a |
21.92 ± 1.47a |
16.94 ± 0.56a |
|
M2 |
73.52 ± 2.65a |
22.58 ± 2.24a |
18.73 ± 1.68a |
|
M3 |
75.00 ± 4.69a |
23.58 ± 1.45a |
13.50 ± 0.68b |
|
M4 |
73.09 ± 3.40a |
22.34 ± 0.77a |
12.72 ± 1.68b |
|
Available nitrogen (mg kg-1) |
M0 |
182.66±10.97a |
70.74 ± 5.49ab |
40.46 ± 2.62cd |
M1 |
167.75 ± 8.17a |
62.23 ± 3.14c |
48.03 ± 4.10b |
|
M2 |
180.53 ± 4.02a |
63.88 ± 3.49bc |
54.89 ± 1.72a |
|
M3 |
182.18 ± 9.99a |
73.11 ± 2.48a |
42.35 ± 1.54c |
|
M4 |
170.12 ± 7.94a |
67.55±4.63a-c |
36.29 ± 2.80d |
|
Available phosphorus (mg kg-1) |
M0 |
2.74 ± 0.18a |
1.46 ± 0.05a |
1.07 ± 0.03c |
M1 |
2.70 ± 0.18a |
1.22 ± 0.06b |
0.99 ± 0.08c |
|
M2 |
1.71 ± 0.10b |
1.22 ± 0.09b |
1.08 ± 0.02c |
|
M3 |
1.75 ± 0.11b |
1.19 ± 0.11b |
1.38 ± 0.19b |
|
M4 |
1.33 ± 0.16c |
1.08 ± 0.03b |
2.40 ± 0.22a |
|
Available potassium (mg kg-1) |
M0 |
296.07±26.71a |
276.86±10.19a |
224.42±16.62a |
M1 |
200.78±17.96c |
189.70±9.98c |
157.94±11.67b |
|
M2 |
217.03±5.52bc |
193.39±7.68c |
174.19±11.30b |
|
M3 |
232.54±14.07b |
225.15±12.98b |
187.43±10.47b |
|
M4 |
227.37±6.37bc |
203.73 ± 5.17c |
148.33 ± 8.39b |
M0 represents the
treatment without mowing. M1, M2, M3 and M4
represent the treatment with mowing one, two, three, four times, respectively
Within each column, different
lowercase letters denote significant differences among treatments (P <
0.05)
Discussion
The results
of this study showed that the aboveground biomass of the grassland
community was decreased by increasing mowing frequency, and the community
density of C.
argyi as a constructive species was also decreased
(Fig. 1–2). As one of the main ways of grassland utilization, mowing can have different effects on plant community productivity and
species diversity by affecting the habitat resource status of plants or
directly affecting plant growth, respectively (Rajaniemi
2002; Staalduinen et al. 2010b). Long-term non-mowing will increase the accumulation of litter, a large
amount of ground cover will cause plant seeds unable to touch the soil and
cannot germinate, and lead to a decline in grassland species and productivity
ultimately (Wang et al. 2014). However,
with the increase of mowing frequency, the destruction of
grassland vegetation by humans will exceed the threshold of ecosystem
restoration, resulting in a sudden decrease in aboveground biomass (Ritchie et al. 1998). Community plants respond
to mowing in varying degrees, mowing often causes greater damage to the growth
of dominant species, and increases the available resources and space in the
community, which is conducive to the expansion of less damaged non-dominant
species populations, thereby reducing the population density of dominant
species (Han et al. 2010; Sun 2012).
The diversity of grassland communities largely maintains the sustainability of grassland
ecosystems and the stability of grassland productivity (Tilman
et al. 1996). However, the academic
community has not formed a unified consensus on the response of grassland
community diversity to mowing. Grime et al. (1987) and Wang et al. (2012) believed that mowing
enhanced grassland species richness to a certain extent, while Huhta et al. (2001) believed that long-term mowing had no significant effect on species richness. Community diversity is
affected by a combination of biological factors, environmental factors,
community succession, natural disturbances, and human disturbances. In this study, the
increase of mowing frequency inhibited the competitive production of dominant
species of C. argyi in its growth period, and provided
breeding opportunities for other species with poor competitiveness (Miguel et al. 2005). The competition
caused by mowing is conducive to species occupying different niche to maximize
the utilization of limited light resources, and the dominant species and
functional groups of the grassland community will change accordingly (Hooper
1998). Thus, the community diversity of C. argyi grassland was
increased.
The plant-soil system
is an organic whole that interacts and influences each other. When the ground
part of the plant changes due to human disturbance such as mowing, it will
inevitably affect the physical and chemical properties of the soil (Greene et al. 1994). Soil
bulk density is an important physical property of soil, which reflects the
degree of soil degradation to a certain extent. The increase in sand proportion
means the increase in soil bulk density, the
larger the bulk density value, the more serious the soil degradation (Wheeler et al. 2002;
Keller and Håkansson 2010; Suuster et al. 2011). In this study, mowing increased the sand proportion and decreased the clay proportion in each soil layer, which was the most significant when mowing three times. As the main material and energy source to regulate
soil biological ecological dynamics, Soil organic matter has the properties of improving soil structure and
maintaining soil moisture, and is an important
indicator of soil properties (Zhang et al.
2005).
Excessive mowing
can cause the damages and degradation of the aboveground parts
of the community, leading to a loss of soil resources and not being well replenished (Sun et al.
2016). It can also change the cycle and behaviour characteristics of chemical elements in
the grassland ecosystem. Continuous mowing makes the output of nutrients greater than the input of the grassland, breaking the dynamic balance of soil nutrients, and has negligible effect on the chemical properties of soil (Liu et al. 2016). In this
study, mowing reduced the content of soil organic matter. Because the
decomposition of the litter in the control took a long time (Wang et al. 2003), the
difference between the treatments and the control was not obvious in the
short term. However, with the increase of
mowing frequency, the removed plants took away more N, P and K, but less
returned to the soil (Curtin et al. 1998), which reduced the content of available nitrogen, available phosphorus, and available
potassium in the soil.
Conclusion
Results of
this study unveiled that mowing frequency had
considerable effects on C. argyi community structure and soil characteristics. Moreover,
mowing once during growth period is more appropriate to maintain above-ground
biomass and community diversity of C. argyi grassland in the wetland habitat in
a good state and to improve soil particle structure and nutritional status, which is
beneficial to C.
argyi as the
forage of elk.
This
work was supported by the National Natural Science Foundation of China (Grant No. 31170400; Grant No.31460132).
We thank Prof. Gudrun Bornette of The French National
Centre for Scientific Research (CNRS) for his valuable comments on the original
manuscript.
Author Contributions
LYY designed the experiments, HBY wrote the manuscript, PF and YQL performed the experiments, HBY, PF and
LL statistically analyzed the data and made illustrations.
Bao SD (2008). Anal soil Agrochem, pp:67‒224. China Agricultural Press, Beijing, China
Bernhardt-Römermann
M, C Römermann, S Sperlich, W Schmidt (2011). Explaining grassland
biomass – the contribution of climate, species and functional diversity depends on
fertilization and mowing frequency. J Appl Ecol 48:1088‒1097
Curtin D, CA Campbell, A Jalil (1998). Effects of acidity on mineralization: pH-dependence of organic
matter mineralization in weakly acidic soils. Soil Biol Biochem 30:57‒64
Dyke FV, SEV Kley,
CE Page, JGV Beek (2004). Restoration efforts for
plant and bird communities in tallgrass prairies
using prescribed burning and mowing. Restor Ecol 12:575‒585
Field CB, JE Campbell, BD Lobell
(2008). Biomass energy: The scale of the potential resource. Trends Ecol Evol 23:65‒72
Greene RSB, PIA Kinnell,
JT Wood (1994). Role of plant cover and stock trampling on
runoff and soil-erosion from semi-arid wooded rangelands. Soil Res 32:953‒973
Grime JP, JML Mackey, SH Hillier, DJ Read (1987). Floristic diversity in a model system using
experimental microcosms. Nature 328:420‒422
Han L, YJ Guo, JG Han, YJ Guo,
H Tang (2010). A study on the diversity and aboveground
biomass in a Leymus chinensis
meadow steppe community under different cutting intensities. Acta Pratac Sin 19:70‒75
Hooper DU (1998). The role of complementarity and competition in ecosystem responses to variation in plant
diversity.
Ecology 79:704‒719
Hooper DU, FS Chapin, JJ Ewel, A
Hector, P Inchausti, S Lavorel, B Schmid (2005). Effects of biodiversity on
ecosystem functioning: A consensus of current knowledge. Ecol Monogr 75:3‒35
Huhta AP, P Rautio, J Tuomi, K Laine (2001). Restorative mowing on an
abandoned semi-natural meadow: Short-term and predicted long-term effects. J Veg Sci 12:677‒686
Jiang L, Y Xiao, EM Rao,
LY Wang, Z Ouyang (2016). Effects of land use and
cover change (LUCC) on ecosystem sand fixing service in Inner Mongolia. Acta Ecol Sin 36:3734‒3747
Keller T, I Håkansson
(2010). Estimation of reference bulk density from soil particle
size distribution and soil organic matter content. Geoderma 154:398‒406
Liu XQ, X Zhang, LF Zhang, YN Li, L Zhao, SX Xu, S Gu (2016). Effects of exclosure
duration on the community structure and species diversity of an alpine meadow
in the Qinghai-Tibet Plateau. Acta Ecol
Sin 36:5150‒5162
Ljubicic I, M Britvec,
SD Jelaska, S Husnjak (2014). Plant diversity and chemical soil composition of
rocky pastures in relation to the sheep grazing intensity on the Northern
Adriatic Islands (Croatia). Acta Bot Croat 73:419‒435
Miguel JMD, L Ramírez-Sanz,
I Castro, M Costa-Tenorio, MA Casado,
FD Pineda (2005). Plant species richness and spatial
organization at different small scales in western Mediterranean landscapes. Plant Ecol 176:185‒194
Peng H, LJ Zhao (2004). Research
on evaluation of tourism resources of Swan Island wetland
in Shishou, Hubei. Land Resour Sci Technol Manage 21:26‒29
Rajaniemi TK (2002). Why does
fertilization reduce plant species diversity? Testing three
competition-based hypotheses. J Ecol 90:316‒329
Ritchie ME, D Tilman, JM Knops (1998). Herbivore effects on
plant and nitrogen dynamics in oak savanna. Ecology 79:165‒177
Staalduinen MAV, B Peco, I Dobarro (2010a). Interactive effects of
clipping and nutrient availability on the compensatory growth of a grass
species. Plant Ecol 208:55‒64
Staalduinen MAV, I Dobarro,
B Peco (2010b). Interactive effects
of clipping and nutrient availability on the compensatory growth of a grass
species. Plant Ecol
208:55‒64
Sun L, Y Liu, GL Wu, XH Wei (2016). The relationships between community biomass
and soil nutrients in the northern Tibet degradation grassland. Pratac Sci 33:1062‒1069
Sun YM (2012). The research of cutting methods on plant community
succession of grassland. Master Thesis. Inner Mongolia University,
Hohhot, China
Suuster E, C Ritz, H Roostalu, E Reintam, R Kõlli, A Astover
(2011). Soil bulk density pedotransfer functions of
the humus horizon in arable soils. Geoderma 163:74‒82
Tilman D, D Wedin, J Knops (1996). Productivity and sustainability influenced by biodiversity in grassland
ecosystems. Nature 379:718‒720
Valliere JM, S Balch, C Bell, C
Contreras, BE Hilbig (2019). Repeated
mowing to restore remnant native grasslands invaded by nonnative
annual grasses: Upsides and downsides above and below ground. Restor Ecol 27:261‒268
Wan ZQ (2014). Effects
of different cutting frequency on community characteristics and compensatory growth of Stipa grandis steppe in Inner Mongolia. Master Thesis. Inner Mongolia University, Hohhot, China
Wang CS, FD Meng, XE Li, LL Jiang, SP Wang (2014). Factors affecting plant primary productivity of grasslands: A review. Acta Ecol Sin 34:4125‒4132
Wang GL, B Wu, QL Yang, CL Jia, YB Sheng (2012). Effect
of cutting on grassland species diversity and productivity of shrub-grass in
Hilly areas. Acta Agrest Sin
20:1020‒1025
Wang W, JX Guo,
BT Zhang (2003). Seasonal dynamics of environmental factors and decomposition rate of
litter in the Leymus
chinensis community in Songnen
grassland in Northeast China. Acta Pratac Sin 12:47‒52
Wen HJ, P Sha, YM Zhang, T Yang (2012). Habitat
degradation and its conservation strategies in Shishou
Milu National Nature Reserve. J Green Sci Technol 6:249‒251
Wheeler MA, MJ Trlica,
GW Frasier, JD Reeder (2002). Seasonal grazing affects soil physical properties of a montane riparian community. J Range Manage Arch 55:49‒56
Xiang MX, D Lha, JX Wu, JJ Wu (2019). The response of plant
community characteristics and soil nutrients to different grazing intensities
in the Lhasa river valley. Plateau Sci Res
3:32‒39
Yamauchi A, N Yamamura (2004). Herbivory promotes plant production and
reproduction in nutrient-poor conditions: Effects of plant adaptive phenology. Amer Nat 163:138‒153
Yang Y, LX Jia, JR Qiao, MR Li, F Zhang, DL Chen, H Zhang, ML Zhao (2019). Effects of heavy grazing on soil nutrients and
microbial diversity in a desert steppe. Chin J Grassl 41:72‒79
Zhang JE, WG Liu, JQ Chen, YC Shi, YF Cai
(2005). Effect of mowing on soil nutrients and soil enzyme
activities in the lower root zone of pasture. Ecol Environ 14:387‒391
Zhang QL, ZM Wang (2002). A simple method for the
determination of soil Particle size in the United States, Vol. 3, pp:18‒20. Applied Technology
for Soil and Water Conservation, China