1 INTRODUCTION
Changes in land use, and its main vegetation cover, modify soil
physico-chemical properties, including soil organic carbon content
(Guillaume et al., 2015), phosphorous content and fractions (Maranguit
et al., 2017). Land use change is a major driver of soil bacterial and
fungal communities (Szoboszlay et al., 2017; Tian et al., 2017; Meng et
al., 2019), leading to changes in microbial community composition. These
changes are likely to influence ecosystem functioning (Sala et al.,
2000; Lauber et al., 2008; Zhu et al., 2011; Xue et al., 2017).
Increased land-use intensity, such as conversion of natural vegetation
to arable agriculture, hampers disturbance-sensitive species, thereby
selecting for species tolerant of such disturbance (Balmford, 1996;
Williams et al., 2017). It leads to decreased populations and often to
reduced soil microbial diversity (De Vries et al., 2012; Tsiafouli et
al., 2015; Williams et al., 2017; Delgado-Baquerizo et al., 2017a;
Newbold et al., 2018) as well as homogenization of microbial assemblage
biodiversity across space (McKinney et al., 1999; Newbold et al., 2018;
Tian et al., 2018). This effect have been consistently observed across
the continental scale (Szoboszlay et al., 2017).
The effects of land use change on soil microbial communities has the
potential to affect soil ecosystem multifunctionality and stability
(Naeem & Li, 1997; Lefcheck et al., 2015; Maestre et al., 2015).
Ecological stability consists of two components: resistance (the amount
of change caused by a disturbance), and resilience (the speed with which
a system returns to its pre-disturbance level) (Pimm, 1984).Recent
studies have shown that changes in microbial properties, such as
bacterial ⍺-diversity (Jing et al., 2015) affected multifunctional
resistance of ecosystem(De Vries & Shade, 2013; Luo et al., 2019). At
the same time, microbial communities can regulate the multifunctional
resistance of ecosystems to global change (Delgado-Baquerizov et al.,
2017b). Microbial diversity is a strong predictor of ecosystem
multifunctionality (Luo et al., 2017). Soil microbial communities drive
biogeochemical processes, including carbon dynamics and nutrient
transformation (Camenzind et al., 2018), litter decomposition
(Delgado-Baquerizov et al., 2016), and plant productivity (Creamer et
al., 2010). Increased bacterial abundance raises the protozoa abundance
(Valencia et al., 2018) and conversely, reduces bacterial abundance is
related to multifunctionality (Wagg et al., 2014). As a result,
microbial function has a positive linear relationship with the
multifunctional resistance of ecosystems (Luo et al., 2019).
Karst ecosystems account for 15-20% of global ice-free surface area (Hu
et al., 2016). The karst area in southwestern China is one of the
largest in the world (Liang et al., 2015). Widespread soil degradation
observed in the southwest Chinese karst has been driven by rapid
population growth, intensive agriculture and urbanization over the last
50 years (Huang & Cai,2006; Chen et al., 2011; Gao et al., 2013).
Increasing land use intensity in the region has caused increased
exposure of carbonate rock outcrops leading to loss and limitation of
nitrogen and phosphorus nutrients (Zhang et al., 2015), decreasing soil
organic carbon and microbial biomass carbon concentration in aggregates
(Xiao et al., 2017). Recent studies have reported effects of land use
change on soil microbial communities in the Chinese karst (Yun et al.,
2016; Xiao et al., 2017; Wang et al., 2017; Li et al., 2018). However,
direct evidence on how microbial communities regulate the
multifunctional resistance of ecosystems following land-use change in
karst areas is still lacking, particularly on the quantifiable impact of
microbial communities on multifunctional resistance of ecosystems and
the key bacterial taxa involved.
We hypothesize that (1) changes in land use reduces multifunctional
resistance of ecosystems by affecting microbial communities; (2) the
composition of microbial communities are a significant driver of
ecosystem multifunctional resistance. A specific aspect is that
oligotrophic bacteria have high resistance with increasing land use
disturbance because they are well adapted to soils with low substrate
availability (Fierer et al., 2007; Tian et al., 2017). To test our
hypotheses, the present study focused on the link between bacterial
community structure and ecosystem multifunctionality along a land-use
change gradient in the karst region. We (1) evaluated multifunctional
resistance of the soil ecosystems and the resistance of major bacterial
taxa and (2) determined the main predictors of multifunctional
resistance of ecosystems and quantified the ability of specific
bacterial groups to predict both multifunctional and single function
resistance of ecosystems including carbon, nitrogen, and phosphorus
cycling.