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由城市化进程改变的城市空间热环境对城区土体湿度产生了重要影响。为了了解城区与郊区土体湿度的差异,以南京市为例,分别在城区、郊区建立了土体湿度监测站,分析2009年6月1日至2010年6月7日南京城区、郊区地下1 m范围内裸土、草地及混凝土覆盖环境下土体湿度的时空演化特征。研究结果表明,南京城区土体湿度总体上小于郊区,存在显著的城市土体＂干岛效应＂,年平均干岛强度为-7.4%。在时间尺度上,1月的干岛强度最小,为-2.1%;7月最大,达到-20.5%。在空间尺度上,郊区土体湿度随深度增加而增大,城区土体则无明显规律。在不同地面覆盖环境下,城区、郊区土体湿度变化规律不同：城区裸土环境下土体湿度日变化明显,而草地及混凝土下的土体湿度日变化相对较小,3种地面覆盖环境的年均土体湿度变化规律为草地（19.0%）〈混凝土（26.4%）〈裸土（29.5%）;郊区3种地面覆盖环境下土体湿度日变化区间及变化频率均比城区大,且年均土体湿度为混凝土（27.4%）〈草地（34.7%）〈裸土（36.2%）。最后,分析了造成城区、郊区土体湿度差异的原因。“,”Urbanization has already significantly influenced urban thermal environment.Two monitoring stations were built both in urban and suburban Nanjing.The spatio-temporal characteristics of soil moisture,starting from June 1st,2009 to June 7th,2010,under three different land covers（bare soil,grass,concrete） within 1 m depth were studied.The result indicated that soil moisture in urban area was lower than that in suburban area,and revealed an obvious ＂urban dry island＂ effect in soil.The corresponding annual average urban dry island intensity（UDII） was approximately-7.4%.The UDII reached its gully and peak value in January and July,respectively,and the monthly average UDII was about-2.1% and-20.5%.In addition,soil moisture in suburban area increased with depth but this tendency is not significant in urban area.Moreover,it was observed that soil moisture under different land covers presented different characteristics.In urban area,daily soil moisture under bare soil cover was more variable than that under grass and concrete covers.The variation ranges of soil moisture under the three covers were all great.The sequences of yearly average soil moisture under the three covers were grass（19.0%）〈concrete（26.4%）〈bare soil（29.5%） in urban area and concrete（27.4%）〈grass（34.7%）〈bare soil（36.2%） in suburban area.The fluctuation of soil moisture in urban area is less severe than that in suburban area due to the large area of artificial land covers.The causes of the diversities in soil moisture were discussed and the urban heat island effect is one of the main reasons induce urban dry island effect.