Effect of vegetation types on soil arbuscular mycorrhizal fungi and nitrogen-fixing bacterial communities in a karst region

Abstract

Arbuscular mycorrhizal (AM) fungi and nitrogen-fixing bacteria play important roles in plant growth and recovery in degraded ecosystems. The desertification in karst regions has become more severe in recent decades. Evaluation of the fungal and bacterial diversity of such regions during vegetation restoration is required for effective protection and restoration in these regions. Therefore, we analyzed relationships among AM fungi and nitrogen-fixing bacteria abundances, plant species diversity, and soil properties in four typical ecosystems of vegetation restoration (tussock (TK), shrub (SB), secondary forest (SF), and primary forest (PF)) in a karst region of southwest China. Abundance of AM fungi and nitrogen-fixing bacteria, plant species diversity, and soil nutrient levels increased from the tussock to the primary forest. The AM fungus, nitrogen-fixing bacterium, and plant community composition differed significantly between vegetation types (p < 0.05). Plant richness and pH were linked to the community composition of fungi and nitrogen-fixing bacteria, respectively. Available phosphorus, total nitrogen, and soil organic carbon levels and plant richness were positively correlated with the abundance of AM fungi and nitrogen-fixing bacteria (p < 0.05). The results suggested that abundance of AM fungi and nitrogen-fixing bacteria increased from the tussock to the primary forest and highlight the essentiality of these communities for vegetation restoration.

Soil enzyme activity and stoichiometry along a gradient of vegetation restoration at the Karst Critical Zone Observatory in Southwest China

“…By contrast, AP activity in the primary forests was decreased relative to C‐acquiring enzyme activities in the primary forest at Tianlong Mountain. Unlike P‐limitation observed in the primary forest by Zhang, Dong, et al (), we suggest that the natural forest ecosystem studied herein was well adapted to P‐deficiency through the development of mutualistic relationships between trees and arbuscular mycorrhizal fungi, for example (Liang, Pan, He, Chen, & Su, ). The larger soil microbial biomass in undisturbed primary forests in karst ecosystems (Zhu et al, ), relative to grasslands or shrublands, is likely adapted to alleviate P limitation by releasing hydrolase enzymes to catalyse SOM decomposition and promote nutrient recycling.…”

Relationships between plant diversity and soil microbial diversity vary across taxonomic groups and spatial scales

“…Contrary to our expectation, a weak plant-mycorrhizal fungal (AMF and ECMF) correlation was observed. For instance, nitrogen fixation bacteria seem to hold a stronger correlation with plant diversity (Liang et al 2016, Zhou et al 2016. For example, some ECMdominated ecosystems (e.g., boreal and tropical monodominant forests) tend to have low plant diversity despite the high richness in these fungal communities (McGuire 2007, Corrales et al 2016, Garcia et al 2018.…”

“…These summary statistics of different taxonomic groups in the same work were considered as separate results to avoid subjective decisions and lost information. Abundance in our dataset represents the relative abundance of a specific phylum (e.g., Wu et al 2012 or taxonomic group (e.g., Alvarez-S anchez et al 2012, Liang et al 2016. Since some literature provided information on soil composition of sand, silt, and clay, the widely used United States Department of Agriculture (USDA) soil textural classification system which determines soil types based on the physical texture (i.e., the percentage of sand, silt, and clay) was used.…”

“…For example, based on a sitelevel analysis, the richness of certain bacterial taxa, such as nitrogen-fixing bacteria, was more closely related to plant diversity than were other taxonomic groups (Liang et al 2016, Zhou et al 2016. First, the plant-microbial relationship can vary among different microbial taxonomic groups.…”

Rhododendron aureum Georgi formed a special soil microbial community and competed with above‐ground plants on the tundra of the Changbai Mountain, China

“…Nitrogen is one of the most important limiting factors for organism productivity; thus, nitrogen‐fixing organisms play a key role in microbial and plant biomass production, as well as organic matter accumulation in soils (Jhp et al., 1997). Nitrogen‐fixing bacteria are important functional microorganisms in soil quality (Ahmad et al., 2016) because they promote the establishment and growth of plants by increasing the nutrient supply (Jasper, Abbott, & Robson, 1989; Liang, Pan, He, Chen, & Su, 2016). Our results show that the abundance of N‐fixing genes has a significant positive correlation with soil nutrients, especially total nitrogen and available nitrogen.…”