Responses Of Glomalin-related Soil Proteins To Nitrogen And Phosphorus Addition In Temperate Desert Steppe

Arbuscular mycorrhizal fungi(AMF)are vital components of soil micororganisms in temperate desert steppe ecosystem,and which have multiple ecological functioning,including changing plant productivity,diversity conservation and nutrient cycling.AMF can secrete kinds of glycoproteins in soil,which were defined as glomalin-related soil proteins(GRSP).Experimental evidence found that GRSP can alter multiple ecological processes,such as soil carbon(C)sequestration and soil physical structure.Soil fertility,plant and AMF may shape the contents of GRSP in natural grassland ecosystem.However,how GRSP content responds to soil fertility in temperate desert steppe is still unclear.Hence,we conducted in situ experiment(2019-2021)to evaluate the impacts of AMF activity regulation(fungicide addition)and inputs of nitrogen(N)and phosphorus(P)on GRSP contents in a temperate desert steppe in Eastern Ningxia.Further,we tested the main and interactive effects of plant identity and P addition on GRSP contents through a greenhouse study.Main results as follows:(1)The results of field study found that P supply and bemomyl application significantly reduced the contents of easily extractable GRSP(EEG)and total GRSP(TG)after three consecutive years(20192021).N input alone had a minimal effect on the contents of TG and EEG.P input and bemomyl application significantly decreased mycorrhizal root colonization and hyphal density.N,P and benomyl addition significantly enhanced aboveground net primary productivity(ANPP)and shoot biomass of C3 grasses,N and P inputs significantly increased soil inorganic N and available P,respectively.Structural equation model(SEM)found that all treatments explained 27%of the variation in EEG content and 41%of the variation in TG content.The addition of P and benomyl suppressed the contents of EEG and TG mainly by reducing hyphal density.(2)The results of greenhouse study showed that plant identity and P input interactively altered the EEG content,but had no effect on TG content.P input s ignificantly reduced the EEG content in root zones of Medicago sativa,Agropyron mongolicum,Cleistogenes squarrosa and Bupleurum smithii,enhanced it in root zone of Stipa breviflora,but had no impacts on it for other plants.P supply decreased TG content in the root zone of M.sativa and C.squarrosa,but had no impacts on TG content in the root zone of other species.P input greatly improved aboveground biomass and total biomass,and mainly reduced the rootshoot ratio of legumes.P input increased the root lengths(0-0.5 and 0.5-1 mm)of Lespedeza daurica,Trifolium repens,Astragalus adsurgens,Leymus chinensis,and Bromus inermis,but reduced those of M.sativa.Summary,the GRSP contents in temperate desert steppe o was mainly shaped by soil available phosphorus level.The contents of EEG and TG were changed by the hyphal density of AMF.The interaction between plant identity and P supply was the main controlling factor for EEG content in temperate desert steppe soil in Ningxia.