| The soil micro-food web is an important component of the soil ecosystem,consisting of a variety of biological groups such as microorganisms and microfauna in the soil,which interact with each other through the food chain and food web to promote the decomposition and transformation of organic matter in the soil.The native plant Phragmites australis(PA)and invasive plant Spartina alterniflora(SA)are typical of halophytes in China,and their decomposition will produce a large amount of organic matter,promote the growth and reproduction of microorganisms,and have an important impact on the nutrient cycle of halophytic marshland.In order to study the role of soil micro-food web in the litter decomposition of two plants,I carried out the following two studies: 1)three microcosms were constructed using different doses of γ-ray irradiation,complete sterilization(irradiated by 60 k Gy γradiation,γ60),only microorganisms(irradiated by 6 k Gy γ radiation,γ6)and intact micro-food web(unirradiated,RAW),in order to examine the influence of micro-food web components on the decomposition process of SA and PA;2)adding the bacterivorous nematode Diplolaimella stagnosa(D)to the microcosms after removing microfauna,I studied the role of individual soil microfauna in the decomposition of litter from PA and SA.The main findings are as follows:The effects of soil micro-food web components on the decomposition process of invasive plant SA and native plant PA litter were studied.The results showed that: 1)litter type and micro-food web composition had a significant impact on the decomposition rate and enzyme activity of the litter,and the decomposition rate of SA and its mixed litter was significantly higher than that of PA,the β-glucosidase(BG)and amino-grape glycosidase(NAG)enzyme activity of plant litter tended to increase and the decomposition accelerated;2)in terms of litter of SA,the decomposition rate of γ6 was not significantly different from that of γ60,but the presence of soil microfauna in RAW could stimulate a significant increase in bacterial richness,BG and NAG enzyme activity,and significantly accelerate the decomposition rate;3)in PA litter,the decomposition rate of γ6 was significantly higher than that of γ60,but the decomposition rate,BG enzyme activity,bacterial richness and diversity of RAW were not different from γ6;4)in the soil layer,the presence of microorganisms(γ6)had no significant effects on soil carbon content,nitrogen content and BG enzyme activity,but the presence of soil animals(RAW)stimulated significant increases in soil bacterial diversity,richness,and enzyme activity,with significant increases in soil carbon content in the treatment groups of S.alterniflora and mixed litter.The results above indicate that the different components of the micro-food web all play an important role in the decomposition process of halophyte litter.Compared to native plants,the decomposition rate of invasive plants is not only accelerated due to their litter characteristics,but also accelerated by the interaction between micro animals and microorganisms in the micro-food web.The effects of the single nematode D.stagnosa(D)on the litter decomposition process of the invasive plant SA and native plant PA showed that: 1)the addition of nematodes had no significant effect on the decomposition rate and enzyme activity of litter of the two plants,but could significantly increase soil carbon content and increase the activity of BG and NAG in soil;2)the addition of nematodes can change the bacterial community structure of the litter layer and soil layer,but the effect on the bacterial community is different between the two plants,SA can better promote the growth of Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes in litter and soil,and the bacterial richness tends to increase.In summary,soil fauna can promote the transfer of carbon from litter to soil and change the carbon and nitrogen cycle process of soil,but the interaction between soil fauna and microorganisms is affected by litter input during plant invasion. |
