黄河デルタ地帯の異なる植物群集の土壌酵素活性の特徴と要因

[Characteristics and Factors of Soil Enzyme Activity for Different Plant Communities in Yellow River Delta].

• Xue Mo
• Fei-Jie Chen
• Chong You
• Fu-de Liu

抄録

土壌酵素は沿岸湿地群集の構築と継承に重要な役割を果たしているが，水ストレスや塩ストレス条件下での酵素活性の駆動機構は未だ明らかになっていない．本研究では、黄河デルタ地域の根圏土壌および非根圏土壌におけるスクラーゼ、ホスファターゼ、カタラーゼ、ウレアーゼの活性と分布を調査した。さらに，土壌の物理化学的性質の変化と合わせて，ハロフィティ植物群集の継代に伴う土壌酵素活性の変化とその影響因子について検討した。その結果，根圏土壌では，非根圏土壌に比べて，根圏土壌の酵素活性と土壌肥沃度パラメータが有意に高いことがわかった（<0.05）．根圏土壌では、ホスファターゼとカタラーゼの活性が<<の順に上昇し、スクラーゼ活性は<<、ウレアーゼ活性は<<の順に上昇した。さらに、根圏土壌の物理化学的性質には、異なる葉緑体群集間で有意な差が認められ（<0.05）、植物の種類や根圏効果が土壌酵素活性や肥沃度特性に影響を与える可能性が示唆された。さらに、二元分散分析の結果、根圏効果は植生の種類よりも大きいことが示された。土壌スクラーゼ活性は、利用可能なカリウム（AK）、利用可能なリン（AP）、アンモニウム窒素（NH-N）と有意に正の相関を示した（<0.05）。一方、ウレアーゼ活性は全窒素（TN）、有機物（SOM）、AK、AP、NH-N、硝酸性窒素（NO-N）と有意に正の相関を示した（<0.01）。また、両酵素は土壌の電気伝導度（EC）と負の相関を示した（<0.01）。また、ホスファターゼおよびカタラーゼ活性は、土壌水分量（MC）、総炭素（TC）、総リン（TP）、SOM、AK、NH-Nと有意に正の相関が認められた（<0.05）。また、pH、総カリウム（TK）、NO-Nもカタラーゼ活性と有意に関連していた。最後に、冗長性分析（RDA）の結果、土壌酵素活性に影響を与える主な因子は、TC（<0.01）、SOM（<0.01）、MC（<0.01）、TN（<0.05）、NH-N（<0.05）、EC（<0.05）であることが明らかになった。これらの結果から、黄河デルタ地帯の異なる葉緑植物群集において、土壌の肥沃度、水、塩分が土壌酵素活性に最も影響を与える要因であることが示唆された。

Soil enzymes play key roles in the construction and succession of coastal wetland communities, while the driving mechanism of their activities under water and salt stress conditions is still unclear. The activities and distributions of sucrase, phosphatase, catalase, and urease in the rhizosphere and non-rhizosphere soils of , , and communities were studied in the Yellow River Delta. Moreover, the changes in soil enzyme activities and their influencing factors during the succession of halophytic plant communities were discussed in combination with changes in the physicochemical properties of soil. The results showed significantly higher soil enzyme activities and soil fertility parameters in the rhizosphere soils of , , and communities than those in the non-rhizosphere soils (<0.05). In the rhizosphere soils, the activities of phosphatase and catalase increased in the order of < < , while they increased in the order of < < for sucrase activity, and < < for urease activity. Further, significant differences were found in the physicochemical properties of rhizosphere soils between different halophyte communities (<0.05), which indicated that plant types and their rhizosphere effects could affect soil enzyme activities and fertility characteristics. Furthermore, a two-way analysis of variance showed that the rhizosphere effect was greater than that of vegetation type. The soil sucrase activity was significantly positively correlated with available potassium (AK), available phosphorus (AP), and ammonium nitrogen (NH-N) (<0.05). Meanwhile, urease activity was significantly positively correlated with total nitrogen (TN), organic matter (SOM), AK, AP, NH-N, and nitrate nitrogen (NO-N) (<0.01). Both of the two enzymes were negatively correlated with soil electrical conductivity (EC) (<0.01). The phosphatase and catalase activities were found to be significantly positively correlated with soil water content (MC), total carbon (TC), TN, total phosphorus (TP), SOM, AK, and NH-N (<0.05). Additionally, parameters of pH, total potassium (TK), and NO-N were also significantly associated with catalase activity. Finally, the redundancy analysis (RDA) revealed that main factors affecting the overall soil enzyme activity were TC (<0.01), SOM (<0.01), MC (<0.01), TN (<0.05), NH-N (<0.05), and EC (<0.05). The findings suggested that soil fertility, water, and salinity are the most influential factors of soil enzyme activity in different halophytic plant communities of the Yellow River Delta.