Combination of grazing exclusion and grassland type altered soil
properties and fungal β-diversity but not α-diversity11Fund
Project: Supported the 2022 National Natural Science
Foundation(32260355).* Corresponding author: DONG Yiqiang (1989-), male, native of
Pizhou, Jiangsu, lecturer, master supervisor, doctor, mainly engaged
in grassland resources and ecological research, E-mail:
xjdyq1210@163.com
Zhou Shijie a, Dong Yiqiang a,b,c,
*, Yang Helong a,b,c, Yang Suwena,b,c,, Asitaiken·Julihaiti a, Liu
Zeyu a, Nie Tingting a, Jiang Anjinga, Wu Yue a, An Shazhoua,b,c
a School of Grassland, Xinjiang Agricultural
University, Urumqi, 830052;
b Key Laboratory of Grassland Resources and Ecology
Autonomous Region, Xinjiang, Urumqi, 830052;
c Key Laboratory of Grassland Resources and Ecology,
Ministry of Education, Western Arid Region, Urumqi, 830052
Abstract: Soil fungi are involved in the decomposition of
organic matter, alter soil structure and physicochemical properties and
drive the material cycle and energy flow in terrestrial ecosystems.
Grazing exclusion is one of the most common measures to restore degraded
grasslands worldwide. However, changes in soil fungal community
characteristics during grazing exclusion in different types of
grasslands are unknown, and in particular, there is a lack of
experimental evidence on the effects of grassland type and grazing
exclusion on soil fungal diversity. Here, we investigate the effects of
a 9-year grazing exclusion on soil properties, fungal community
composition and diversity in three grassland types (Temperate desert,
Temperate steppe and Mountain meadow). The results showed that soil
fungal community composition differed between grassland types, and that
grazing exclusion, grassland type and the interaction between the two
did not significantly affect soil fungal α-diversity and composition,
but significantly altered fungal β-diversity. Overall, our results
highlight the importance of soil nutrient content on fungal diversity,
particularly soil total nitrogen, total phosphorus and organic carbon,
and provide key evidence to reveal the mechanisms by which soil fungi
respond to grazing exclusion in different grassland types.
Keywords: Grazing exclusion; Grassland type; Fungal diversity;
Fungal communities; Soil properties
Introduction
Grasslands cover 20% of the land surface and play an important role in
preventing soil erosion and supporting livestock farming in semi-arid
areas (Jing et al., 2013;Jing et al., 2014). In recent decades,
grassland degradation has become widespread globally due to increased
human activity and climate change (O’Mara, 2012; Jalaludin et al.,
2020). China has about 400 million hectares of grasslands of various
types, accounting for about 41.7% of the country’s land area (Xu et
al., 2016), and more than 90% of the grasslands are in a degraded state
(Wang et al., 2020). This will lead to a severe weakening of grassland
ecological functions, degradation of soil nutrients (Jing et al., 2014),
and disruption of the original balance of the system, transforming it
into a fragile ecosystem (Zheng et al., 2012). How to effectively
rehabilitate degraded grasslands is a huge scientific and technical
challenge for humans (Wang et al., 2020). The most widely used technical
measure for ecological management of degraded grasslands is grazing
exclusion, which can restore vegetation biomass (Su et al., 2005),
improve soil fertility (Mekuria et al., 2007) and increase grassland use
efficiency (Yang et al., 2005). Previous studies have focused on the
effects of grazing exclusion on plant communities and soil properties
(Wu, 2021; Dong et al., 2016), while research on the effects of soil
fungal communities has been limited.
Soil fungal communities are sensitive to environmental change and have
been recognised as early warning and important indicators of change in
soil ecosystems (Kennedy et al., 1995; Somova et al., 2001) and play a
key role in regulating material cycling in terrestrial ecosystems (Bais
et al., 2006). The structure and function of soil fungal communities in
degraded grasslands are often disintegrated and limited (Zhou et al.,
2011). Therefore, rebuilding soil microbial communities is the primary
task in restoring degraded grasslands. Furthermore, soil fungal
communities play an essential role in reflecting environmental change
(Chen et al., 2020). The composition and diversity of soil fungal
communities have been extensively used as an important biological
indicator for restoring soil quality and ecosystem function in degraded
grasslands (Gao et al., 2021). Therefore, it is critical to assess
changes in soil fungal communities under grazing exclusion conditions
for soil and vegetation restoration and to predict changes in grassland
ecosystem dynamics under environmental change.
Different types of grasslands have an integral part in maintaining the
stability and diversity of grassland ecosystems (Yang et al., 2018).
Numerous studies have shown that the response of soil microorganisms to
grazing exclusion is not consistent across different grassland types. In
alpine grasslands, soil microbial richness indices were significantly
higher than in grazed samples, grazing changed the structure of soil
microbial communities (Jing et al., 2021), while in alpine meadows, the
total number of soil microorganisms was significantly lower after
grazing (Xie et al., 2017). Sun et al. found that grazing exclusion had
no significant effect on the overall numbers of soil bacteria and fungi
(Sun et al., 2018). Hence, the response pattern of soil microorganisms
to grazing exclusion still needs further study. Fungi can be closely
associated with host plants through symbiosis or parasitism (García et
al., 2014) and play a dominant role in soil nutrient cycling (Mcguire et
al., 2010; Treseder et al., 2013). However, former studies have largely
shown that grazing exclusion does not significantly affect the diversity
of fungal communities, probably due to the greater stability of fungi
compared to bacteria (Cheng et al., 2016; Zhang et al., 2018). The
results of studies on the effects of grazing exclusion on the
characteristics of soil fungal communities in different grassland types
are still highly controversial, which limits our understanding of the
changes in soil fungal communities after grazing exclusion. The total
area of natural grassland in Xinjiang is about 5.7×107
hm2 , accounting for 34.4% of the land area (Xu et
al., 1993), which is a valuable resource for the development of the
livestock industry and national economy in Xinjiang. Among them,
temperate desert, temperate steppe and mountain meadow grasslands
account for 48.28% of the total grassland area in Xinjiang (Wang et
al., 2006). Therefore, it is vital to understand the changes in soil
fungal communities of different types of grassland in Xinjiang during
grazing exclusion in order to assess the factors that influence the
fungi communities’ characteristics in different grassland types of
exclusion, this has great significance for grassland managers and
policymakers.
Here, we conducted a regional field experiment to assess the effects of
grazing exclusion, grassland type and their interaction on soil
physicochemical properties, soil fungal community composition and
diversity in combination with plant community characteristics and soil
properties. We attempted to answer three questions: 1) Does fungal
composition and diversity respond consistently to grazing exclusion in
different grassland types? 2) Do grazing exclusion and grassland types
alter fungal communities and diversity? 3) Is soil fungal diversity
indirectly driven by plant and abiotic factors under the grazing
exclusion and grassland type treatments? This study contributes to the
understanding of changes in soil nutrients, especially soil fungi in
different grassland types and provides new ideas for grassland
management in the semi-arid zone.
Materials and methods
2.1. Study area
The study area is located in Changji Hui Autonomous Prefecture
(43.62°-44.39°N, 88.15°-90.25°E, 514-2611m elevation) in the eastern
section of the northern slope of the Tianshan Mountains in Xinjiang. The
region has a typical temperate continental arid climate, with high
temperatures and rainy summers and cold, dry winters, with an average
annual precipitation of 150-300 mm and an average annual temperature of
5-6°C. In the temperate desert zone(Fukang City), the main dominant
plants are Haloxylon ammodendron and Seriphidium
santolinum ; in the temperate steppe zone(Mubi County), the main
dominant plants are Festuca ovina and Carex liparocarpos ;
in the mountain meadow zone(Qitai County), the dominant plants are
mostly grasses and weedy grasses.