Background In the karst region of Southwest China, where is characterized with the fragile ecological environment, the bedrock is bare and soil is shallow, vegetation recovery is difficult. A symbiotic relationship between arbuscular mycorrhizal fungi(AMF) and plants, which is an adaptation strategy by root morphological changes, to cope with nutrient stress by increasing plant nutrient use efficiency. The objective of this study is to provide a microbial interference pathway for vegetation restoration, soil and water conservation. Meanwhile, it would provide the basis for screening dominant strains in karst region.
Methods Zenia insignis is a common afforestation species in limestone areas of Southwest China. We used AMF Funneliformis mosseae, Rhizoglomus intraradices and mixed mycorrhizal fungi(Mi) to inoculate Z. insignis seedlings. The effects of mycorrhizal fungi on root morphology of Z. insignis seedlings in different nutrient condition of karst soil habitats were studied after 150 d of cultivation.
Results 1) In nutrient-poor karst soil habitat, Z. insignis inoculated with F.mosseae showed the highest colonization rate and high-intensity mycorrhizal dependency. F.mosseae significantly increased the root biomass, total root length, total root surface area, total root volume and average root diameter by 460.49%, 233.91%, 258.99%, 293.04% and 9.29%, respectively. Z. insignis inoculated with R.intraradices reduced root biomass, total root length, total root surface area and total root volume by 10.49%, 46.67%, 42.70% and 39.30%, respectively. At the same time, the average root diameter increased 6.14%, which showed no significant difference from the control. Z. insignis inoculated with Mi significantly increased the average root diameter. While the influence on root biomass, total root length, total root surface area and total root volume was between single inoculations. 2) In nutrient-rich karst soil, Z.insignis inoculated with F.mosseae significantly increased root biomass, total root length, total root surface area, total root volume and average root diameter by 138.04%, 28.51%, 50.79%, 76.37% and 20.71%, respectively, which was significantly lower than that by F. mosseae treatment in low nutrient karst soil habitat except for average root diameter. When inoculated with R.intraradices, root biomass, total root length, total root surface area, total root volume and average root diameter significantly increased by 128.62%, 57.30%, 66.27%, 75.68% and 8.63%, respectively. There was significant difference from the R.intraradices inoculation in low nutrient karst soil habitat except for average root diameter. Mi treatment increased root biomass, total root length, total root surface area, total root volume and average root diameter by 51.45%, 39.79%, 38.89%, 36.99% and 1.29%, respectively.
Conclusions The AMF affect the root morphology of Z.insignis in the different nutrient conditions of karst soil habitats. Under the nutrient stress, F.mosseae is more conducive to changing root morphology, making the host plant easier to colonize and survive. Thus, F. mosseae can be used as a dominant strain for the intervention of mycorrhizal fungi for vegetation restoration in nutrient-poor karst soil habitat.
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