Study On Microbial And Enzymatic Characteristics And Plant Species Differences In Rhizosphere Soil Of Halophytes

Saline-alkali soil has become a global soil degradation problem due to its high salt content,poor soil quality and low utilization efficiency.Halophytes have been gradually applied in the phytoremediation of saline-alkali land due to their strong tolerance to saline-alkali environment.At present,the research on the effect of halophyte root activity on soil quality improvement in saline-alkali land is still in the exploratory stage.Therefore,in this study,the physical and chemical properties,extracellular enzyme activities and amino sugar contents of rhizosphere soil of six typical halophytes from inland saline-alkali land in the semi-arid area of northwest China were measured,and the response characteristics of soil enzyme activities and microbial residues to halophyte types and growth seasons were discussed.The main results are as follows:(1)Halophytes significantly affect soil p H,soil salt content and soil electrical conductivity.The p H of rhizosphere soil of halophytes was lower than that of bare soil,and the p H of Suaeda glauca and Calamagrostis epigeios decreased significantly.The soil salt content and electrical conductivity of the rhizosphere soil of Kalidium foliatum,Phragmites australis Calamagrostis epigeios and Tamarix chinensis were significantly decreased by 32%,88%,79%,65% and 30%,87%,78%,59%,respectively,while the soil salt content and electrical conductivity of the rhizosphere soil of Suaeda glauca and Nitraria sibirica increased slightly.The influence of halophytes on soil p H,salt content and electrical conductivity was the largest in the middle of growing season.(2)Halophytes significantly increased the contents of organic matter and soil nitrogen,phosphorus and other mineral nutrients in rhizosphere soil.The effects of Suaeda glauca on the contents of soil organic matter,total nitrogen,nitrate nitrogen,ammonium,total phosphorus and soil available phosphorus were higher than those of other plants.Among the halophytes,Nitraria sibirica,Phragmites australis,Calamagrostis epigeios and Suaeda glauca had the greatest effects on soil organic matter and total nitrogen in the middle of the growing season,while Tamarix chinensis had the greatest effects on soil organic matter and total nitrogen in the early growing season.The increasing effects of Phragmites australis and Calamagrostis epigeios on soil nitrate nitrogen was the largest in the middle of the growing season,while that of Nitraria sibirica,Kalidium foliatum,Tamarix chinensis and Suaeda glauca were at the end of the growing season.The effects of Nitraria sibirica,Kalidium foliatum,Phragmites australis,Calamagrostis epigeios,Tamarix chinensis and Suaeda glauca on soil ammonium increased the most in the early growing season.The increasing effects of Nitraria sibirica,Phragmites australis,Suaeda glauca and Tamarix chinensis on soil total phosphorus were the largest in the middle of the growing season.The effects of Phragmites australis on soil available phosphorus was the highest in the middle of the growing season,and that of Suaeda glauca was the highest at the end of the growing season.(3)Halophytes significantly increased the activities of carbon cycling enzyme,nitrogen cycling enzyme and phosphorus cycling enzyme in rhizosphere soil.The effects of Suaeda glauca on the activities of carbon cycling enzyme,nitrogen cycling enzyme and phosphorus cycling enzyme were higher than those of other plants.The activities of CBH and BG were most affected in the middle of growing season by Nitraria sibirica,Kalidium foliatum,Phragmites australis,Calamagrostis epigeios,Tamarix chinensis and Suaeda glauca.Phragmites australis,Calamagrostis epigeios,Tamarix chinensis and Suaeda glauca had the greatest effect on soil NAG activity in the middle of growing season.In the middle of the growing season,Nitraria sibirica,Kalidium foliatum and Calamagrostis epigeios had the greatest effects on soil LAP activity,while Phragmites australis,Tamarix chinensis and Suaeda glauca had the greatest effects on soil LAP activity at the end of the growing season.Soil ALP activity was most affected by Kalidium foliatum,Suaeda glauca and Calamagrostis epigeios in the middle of growing season,while soil ALP activity was most affected by Nitraria sibirica and Phragmites australis at the end of growing season.The contents of soil organic matter,soil total phosphorus,soil total nitrogen and soil available phosphorus were significantly affected the enzyme activities in the rhizosphere soil of halophytes,and the concentration of soil organic matter was the most important factor.(4)Halophytes significantly increased the content and ratio of amino sugars in rhizosphere soil.Among different halophytes,Suaeda glauca and Calamagrostis epigeios had the greatest effect on the contents of glucosamine,galactose and the total amount of aminosugars;Suaeda glauca had the greatest effects on the concentration of Muramic acid,while Nitraria sibirica and Phragmites australis had the greatest effects on soil Glu N/Mur A.The effects of these halophytes on glucosamine,galactose and total amino sugars were the highest in the middle of growing season.The effects of Nitraria sibirica,Calamagrostis epigeios,Kalidium foliatum and Suaeda glauca on Muramic acid and Glu N/Mur A were the largest in the middle of growing season.Soil physical-chemical properties and enzyme activities affected the accumulation of amino sugars in soil,and soil organic matter,soil total nitrogen,soil total phosphorus,nitrogen cycling enzyme(NAG,LAP)and phosphorus cycling enzyme(ALP)were the main factors affecting the accumulation of amino sugars in soil.The rhizosphere soil of six typical halophytes in inland saline-alkali land of northwest China was studied under different growing seasons.The results showed that halophytes had positive effects on soil physical and chemical properties,soil enzyme activities and microbial residue accumulation.The influence of Suaeda glauca on these indexes was greater than that of other plants.Therefore,the role of Suaeda glauca should be emphasized in the bioremediation of saline-alkali land in the future.