1
274
LIU ET AL.
native vegetation (Yang, Dou, & An, 2017) or soil quality assessments
in this unique region (Dang et al., 2017; Zhang, 2017). Through vege-
tation restoration of the Loess Plateau, its croplands were converted
into grasslands or shrubs via natural succession. Both soil conditions
and vegetation coverage have been improved, along with soil micro-
bial community succession fostered by greater ecological stability in
restored lands compared with degraded lands on the Loess Plateau
soil bacterial communities (Anderson & Cairney, 2004; Pautasso,
2013; Tedersoo et al., 2014).
Soil bacteria and fungi can have different biogeographic patterns
and environmental filters as well as co‐occurrence patterns over con-
tinental scales, implying their distinctive community assembly mecha-
nisms and ecological functions (Ma et al., 2017; Xiao, Liang, Zhou,
Zhuang, & Sun, 2018). The co‐occurrence networks of soil fungal
and bacterial communities are varied in different spatial habitats and
keystone species in networks changed with alterations in soil nutrient
levels (Zheng, Zhao, Gong, Zhai, & Li, 2018). Fungi and bacteria prefer
to decompose recalcitrant soil carbon and simple carbohydrates,
respectively (Xiao et al., 2018). They are often presumed to be more
important in natural ecosystems than in intensively managed systems
that are mostly dominated by bacteria (Franciska T. de Vries, Hoffland,
Nvan, Brussaard, & Bloem, 2006). The communities of soil bacteria
and fungi are correlated with different soil edaphic factors under
two distinct grazing systems dominating on the Tibetan Plateau (Yang
et al., 2019). In particular, strong interactions occur between soil fun-
gal diversity and edaphic variables in natural ecosystems (Zhang,
Dong, et al., 2017), and soil fungi may be greater affected by the pro-
cess of woody plant encroachment compared with soil bacteria (Hol-
(
Guo et al., 2018; Liu et al., 2017; Zhang, Liu, Xue, & Wang, 2016).
In this context, distribution patterns of the soil microbial commu-
nity and their drivers are central issues, as they are crucial for under-
standing and predicting the role played by soil microbes in
maintaining ecosystem functioning and stability when making land
management decisions (Kubartová, Ottosson, Dahlberg, & Stenlid,
2
012). An enhanced appreciation of the link between environment
and microbial ecology, in recent years, has led to many studies
focused on soil bacterial communities in the Loess Plateau region
(
Dang et al., 2017; Xue, Ren, Li, Leng, & Yao, 2017). The crucial con-
tribution of soil fungi for determining the decomposition of recalci-
trant carbon (Treseder, Marusenko, Romero‐Olivares, Maltz,
016) and nutrient cycling in terrestrial ecosystems (Tedersoo
&
2
et al., 2014) is now established. Although less well studied is the
succession of soil fungal communities along a long‐term restoration
chronosequence combined with their spatial discrepancy. From eco-
systems in transition, such as this chronosequence of restored grass-
lands, we can extract valuable information on microbial community
shifts and consequently how these may contribute to soil ecosystem
development. To sum it up: it would be timely to evaluate the eco-
logical restoration process and status from the perspective of soil
fungal community succession combined with soil quality analysis
across time and space.
lister, Schadt, Palumbo, James Ansley,
& Boutton, 2010). The
restoration of grasslands changes the local environment, by directly
modifying the litter layer, root systems, and their exudates as well indi-
rectly affecting edaphic variables that eventually translate into alter-
ations in ecological succession (Franciska T. de Vries et al., 2006).
Only by exploring fungal distribution patterns and dynamics could
we obtain a comprehensive recognition how they develop across time
and space in a restored ecosystem environment. Yet, such knowledge,
especially of environmental adaptation of soil fungal communities, is
rarely elucidated because many soil fungal species remain unrecog-
nized and feature complicated interactions with edaphic factors. Some
of the main obstacles to the study of fungal dynamics are the hetero-
geneity of growth environments and the limited scope of laboratory
experiments. There is one study that presents a highly versatile tool
combining image analysis and graph theory to monitor spatio‐
temporal fungal dynamics (Vidal‐Diez de Ulzurrun et al., 2015). Using
traditional tissue isolation method, community structure and temporal
dynamics of fungi from bagged fruits and unbagged fruits were inves-
tigated in apple orchards (Xue et al., 2016). And that due to the cost
reduction and efficiency improvement of next‐generation sequencing,
which was used to explore the soil fungal dynamics at the community
level as an effective means (Chen et al., 2017).
Fungi harbor a large proportion of Earth's genetic diversity and
fungal activity influences the structure of plant and animal communi-
ties as well as rates of ecosystem processes (Peay, Kennedy, & Talbot,
2
016). Undoubtedly, the distributions and dynamics of soil fungal
communities have been extensively studied. For example, at the local
scale (within 28 km distance), soil fungal communities were found dis-
tributed along an age gradient of managed Pinus sylvestris stands
(
Kyaschenko, Clemmensen, Hagenbo, Karltun, & Lindahl, 2017) and
to reciprocally interact with plant factors and soil properties (Bender
et al., 2014; Heijden, Bruin, Luckerhoff, Logtestijn, & Schlaeppi,
2
016). Along with elevation gradient, soil fungal communities show
lineage‐specific biogeographic patterns in grassland system (Pellissier
et al., 2014); similarly, abiotic factors and woody sagebrush range
expansion have significant effects on the patterns that soil fungal
diversity declines and community composition changes with increas-
ing elevation in shrubland system (Collins, Stajich, Weber, Pombubpa,
Currently, the response of soil fungal communities to vegetation
succession is an outstanding problem in microbial ecology, one tackled
by much complex research (Gao et al., 2018; Hannula et al., 2017;
Purahong, Wubet, Kruger, & Buscot, 2017; Tedersoo et al., 2014).
Succession in a particular environment assumes, by definition, that
communities change over time in an orderly manner (Koch, Brown, &
Lomolino, 1998). A soil chronosequence is a powerful tool for studying
the rates and directions of soil development (Huggett, 1998). Not sur-
prisingly, due to this unique characteristic, it has been widely used to
study changing patterns and drivers of soil fungal communities over
&
Diez, 2018). In addition, soil fungal species composition differs
between forests, depending on the dominant tree species (Yamashita
Hijii, 2006) and forest management practices (Kranabetter, Friesen,
&
Gamiet, & Kroeger, 2005). On the Loess Plateau, one study reported
that land use types can affect soil fungal community composition
(
Yang, Dou, Huang, & An, 2017). In stark contrast, soil fungal commu-
nities generally remain poorly studied in restored lands compared with
Liu, Di
