Effects of grazing exclusion on soil properties, fungal community
structure and diversity in different grassland types11Fund
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, and they 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 used to
restore degraded grasslands worldwide. However, changes in soil fungal
community characteristics during grazing exclusion in different types of
grasslands are unknown. Here, we investigated 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 in the 0-5 cm soil layer,
grazing exclusion significantly affected the physicochemical parameters
of all three studied grassland types. In the 5-10 cm soil layer, grazing
exclusion significantly increased total phosphorus (TP) in temperate
deserts by 34.1%, while significantly decreasing bulk density (BD) by
9.8% and the nitrogen: phosphorus ratio (N:P) by 47.1%. The soil
fungal community composition differed among the grassland types, For
example, significant differences were found among the three grassland
types for the Glomeromycota and Mucoromycota , Grazing
exclusion, grassland type, and the interaction between the two did not
significantly affect soil fungal α-diversity or community
composition(P > 0.05), but significantly altered
fungal β-diversity (P < 0.05). Overall, our results
highlight the importance of soil nutrient content, especially soil
Kjeldahl nitrogen, total phosphorus and organic carbon on fungal
diversity, and the results provide key insights into how soil fungi
respond to grazing exclusion in different grassland types.
Keywords: Grazing exclusion; Soil properties; Soil fungi;
Diversity; Driving factor; Grassland type
Introduction
Grasslands cover 20% of the land surface and play an important role in
preventing soil erosion and supporting livestock farming in semiarid
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 approximately 400 million hectares of grasslands of
various types, accounting for approximately 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). The low quality of grasslands leads
to a severe weakening of grassland ecological functions, the degradation
of soil nutrients (Jing et al., 2014), and disruption in the original
balance of the system, transforming them into a fragile ecosystems
(Zheng et al., 2012). How to effectively rehabilitate degraded
grasslands is an enormous scientific and technical challenge (Wang et
al., 2020). The most widely used measure for the 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 on soil fungal communities has been
limited.
Soil fungal communities are sensitive to environmental change. Changes
in local fungal communities are recognized as an early warning of
problems andan important indication of changes in soil ecosystems
(Kennedy et al., 1995; Somova et al., 2001). Soil fungi also 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 limited (Zhou et al., 2011). Soil fungi
can decompose macromolecules such as lignin and cellulose in plant
residues, and play important roles in soil nutrient accumulation,
transformation and cycling(Oriol et al., 2017). Rebuilding soil
microbial communities is the primary task in restoring degraded
grasslands. Therefore, it is necessary 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
conditions of environmental change.
Different types of grasslands have integral roles in maintaining the
stability and diversity of grassland ecosystems (Yang et al., 2018).
Numerous studies have shown that the response of soil bacteria and fungi
to grazing exclusion are not consistent across different grassland
types. Soil microbial richness indices in alpine grasslands under
grazing exclusion were higher than those in grazed grasslands of the
same type and grazing changed the structure of soil microbial
communities (Jing et al., 2021). In alpine meadows, the total number of
soil microorganisms was significantly lower after grazing exclusion (Xie
et al., 2017). Sun et al. (2018) found that grazing exclusion had no
significant effect on the overall numbers of soil bacteria and fungi in
a Seriphidium transiliense desert. Therefore, the state of
knowledge regarding the variation in grazing exclusion of soil bacteria
and fungi in different grassland types is insufficient and further
research is necessary. Fungi can be closely associated with host plants
through symbiosis or parasitism (García-Guzmán and Heil., 2014; Zhu et
al., 2017; Maron et al., 2011) and play a dominant role in soil nutrient
cycling (Mcguire et al., 2010; Treseder and Holden., 2013). However,
studies indicate that grazing exclusion does not significantly affect
the diversity of fungal communities, probably due to the greater
stability of fungi than that of 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 unclear, which limits our knowledge of the changes in
soil fungal communities after grazing exclusion.
The total area of natural grassland in Xinjiang is approximately 5.7×107
ha , accounting for 34.4% of the land area (Xu et al., 1993), and this
area is a valuable resource for the development of the livestock
industry and national economy in Xinjiang. Among the Xinjiang
grasslands, temperate desert, temperate steppe and mountain meadow
grasslands account for 48.28% of the total grassland area (Wang et al.,
2006). Considering the importance of grasslands in Xinjiang, it is vital
to understand the effects of grazing exclusion on soil fungal
communities in different grassland types in the region. This knowledge
will have great significance for grassland managers and policy-makers.
Here, we conducted a regional field experiment to assess the effects of
grazing exclusion, grassland type and their interaction on soil
physicochemical properties, and soil fungal community composition and
diversity in combination with plant community characteristics and soil
properties. We attempted to answer three questions: 1) Do grazing
exclusion and grassland types alter fungal communities and diversity? 2)
Do fungal composition and diversity respond consistently to grazing
exclusion in different grassland types? 3) What are the main drivers of
changes in soil fungal diversity under grazing exclusion and grassland
type treatments?
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, 514-2611 m elevation) in the eastern
section of the northern slope of the Tianshan Mountains in Xinjiang. The
region has a typical temperate 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
(Zhou et al., 2012). In the temperate desert zone (Fukang city), the
main dominant plants are Haloxylon ammodendron (C.A.Mey.) Bunge
and Seriphidium santolinum (Schrenk) Poljakov ; in the temperate
steppe zone (Mulei County), the main dominant plants species areFestuca ovina and Carex liparocarpos ; in the mountain
meadow zone (Qitai County), the dominant plants are mostly grasses and
weedy grasses(Astiken et al., 2023).