湿地植物根系及其分泌物对土壤脲酶、硝化-反硝化的影响

Effect of Plant Roots and Its Exudates on Urease Activity,Nitrification and Denitrification in Wetland Soil

植物根际是人工湿地通过物理、化学、生物三重协同作用达到污染物去除的重要反应区域,然而关于植物根际土壤酶活性分布及根系分泌物及对人工湿地除污效果的影响目前仍缺乏系统研究。为了明确人工湿地中植物对脱氮的贡献,试验选取当地常见的7种经济耐寒性湿地植物——富贵竹(Dracaena sanderiana)、千屈菜(Spiked loosestrlfe)、美人蕉(Canna indica)、水葱(Scirpus tabernaemotani)、菖蒲(Acorus calamus)、香蒲(Typha angustiolia)、芦苇(Phragmites australis)作为研究对象,考察了不同植物的根际与非根际脲酶活性分布,并探究了植物根系分泌物对土壤脲酶活性及硝化-反硝化作用强度的影响。结果表明:湿地植物根系可以影响脲酶活性,表现为稳定生长的植物根际脲酶活性普遍高于非根际,以美人蕉和香蒲最为显著;不同植物根系对土壤脲酶活性的影响存在差异性,其中,富贵竹、美人蕉和菖蒲根际的脲酶活性接近,且明显高于香蒲、芦苇等其他受试植物;土著微生物对植物植入具有适应期和调整期,使植物对土壤酶活性的刺激效应滞后,表现为植物生长稳定期的脲酶活性平均值基本低于空白样,植物生长迅速期的脲酶活性平均值普遍明显高于空白样,说明植物的存在对土壤脲酶活性具有促进作用;25%的菖蒲根系分泌物对土壤脲酶具有一定程度的促进作用,在培养第25天时达到最佳效果;菖蒲根系分泌物对硝化作用强度有一定的促进作用,但对反硝化作用强度的影响不明显。

The rhizosphere is a key zone where pollutant removal in constructed wetland mainly depends on a synergistic effect ofphysical,chemical and biological mechanisms.However,much less is known about the distribution of soil enzyme in rhizosphereand the effect of root exudates on performance of constructed wetland.In order to determine the contribution of plant to the nitrogenremoval in constructed wetland,seven local and common plants(Dracaena sanderiana,Spiked loosestrlfe,Canna indica,Scirpustabernaemotani,Acorus calamus,Typha angustiolia,Phragmites australis)with higher cold tolerance were used.The ureasedistribution in different plant rhizosphere and non-rhizosphere,influence of root exudates on soil urease activity,nitrification strengthand denitrification strength were observed.The results indicated that wetland plants had an effect on urease activity and the ureaseactivity in rhizosphere was higher than that in non-rhizosphere,especially in Canna indica and Typha angustiolia.The difference ofurease activity was found in different plant roots,and the higher urease activity was occurred in Dracaena sanderiana Canna indicaand Acorus calamus.The indigenous microorganism had adaptation and adjustment to plant implantation,leading to delay insimulating effect of plants on urease activity.It caused that urease activity with plants was lower than that with unplanted at stableplant growth stage which was opposite with fast growing stage.The presence of plants improved the urease activity of soil.Resultsalso revealed that25%of plant root exudates was able to promote soil urease activity in a certain degree and showed best effect onthe twenty-fifth day.Plant root exudates also had a promotion effect on nitrification strength,however,its influence on denitrificationstrength was not obvious.