Effects Of Simulated Acid Rain And Herbicide On Soil Fauna In Urban Turfgrass Ecosystem

Lawn is an indispensable component of the urban green space system,which is responsible for beautifying ecological environment and constructing green landscape.As the most active form of life in turf soil ecosystems,soil fauna play a vital role in maintaining ecosystem function.However,severe acid rain pollution and a large amount of herbicides directly act on the soil,affecting soil fauna and threatening the soil ecosystem.Acid rain and herbicides can also influence each other's toxicity by altering the soil environment.At present,most of the studies on the effects of acid rain and herbicides on soil fauna remain in forest or farmland ecosystems,while the urban ecosystems are not paid enough attention,mainly focusing on single pollution stress.Studying the effects of acid rain and herbicides on soil fauna under single and combined stresses is helpful to further understand the effects of coexistence on soil fauna,and is of great significance to the selection of herbicides and the diagnosis and treatment of pollutants in acid rain areas.Based on this,three simulated acid rain acidity(pH4.5,pH3.5 and pH2.5)and three herbicide concentrations(1‰,2‰ and 4‰)were set up in this study.Aiming at urban lawn,the effects of simulated acid rain and herbicides on soil animal community composition,dominant groups,community diversity and functional community structure under single and combined stresses were studied,and the soil environmental factors were determined to explore the ways of acid rain and herbicides affecting soil animals.The results are as follows:(1)A total of 53421 individuals were obtained in this study,belonging to 6 phyla,28 orders and 81 families.There were significant differences in individual and group numbers of soil fauna under different treatments.Most of the soil fauna decreased after adding acid rain and herbicides,but the individual number of meso-micro fauna(Baermann method)increased with the increase of acid rain acidity.There was no simple linear relationship between the number of soil fauna and the intensity of pollution.Different types of soil fauna had different tolerance ranges to the intensity of pollutants.Under combined stress,acid rain and herbicides had significant interactions with soil macrofauna and meso-micro fauna(Tullgren method),and interactions with meso-micro fauna(Baermann method)were not obvious.(2)The diversity index of soil fauna community under different treatments was significantly different.Shannon index H' and Pielou index J were negatively correlated with acid rain acidity in generally,but positively correlated with herbicide concentration.In single acid rain treatment,the richness index D was positively correlated with acid rain acidity,but no significant correlation under other treatments.(3)The proportions of individual number of soil fauna functional groups were as follows: saprophagy(77.59%)> fungivore(13.79%)> predator(4.90%)> omnivore(2.24%)> phytophagy(1.47%).The difference was not significant between the treatments.(4)Sampling results from different treatment time showed that with the prolongation of test time,simulated acid rain and herbicide treatment did not have significant cumulative effect on soil macrofauna,but had a certain inhibitory effect on the number of individuals and groups of meso-micro fauna.(5)There were significant differences in soil environmental factors under different treatments,which gradually decreased with the extension of the test time.At the end of the experiment,soil water content,ammonium N,available P,available K and acid phosphatase activity decreased to a certain extent compared with the initial period.Relevant analysis showed that soil pH value and ammonium N content had the greatest impact on the diversity of soil fauna community,which were significantly positively correlated with Shannon index H' and Pielou index J,and Simpson index C showed a significant negative correlation.Canonical correlation analysis showed that soil pH value,ammonium N content,water content and urease activity were the main factors affecting the distribution of soil fauna,and different soil fauna had different preferences for environmental factors.