洞庭湖退田还湖区不同土地利用方式对土壤养分库的影响

以钱粮湖垸为例，研究了洞庭湖退田还湖区的林地（Ⅰ）、园地（Ⅱ）、旱地（Ⅲ）、水田（Ⅳ）和荒地（Ⅴ）等不同土地利用方式下的土壤养分含量、养分库综合指数以及养分相关性。研究表明：土壤养分分布的表聚效应明显，0～50 cm土层土壤有机质含量为3.40～32.32 g/kg，全氮、水解氮含量为2.23～9.71 g/kg、12.95～112.00 mg/kg，全磷、速效磷含量为29.50～69.35 g/kg、4.15～75.68 mg/kg，全钾、速效钾含量为603～3069 g/kg、37.70～217.50 mg/kg；林地土壤全氮含量最高，有机质含量最低，水田有机质、全钾及速效磷含量均最高，旱地水解氮含量最高，而荒地土壤全氮、全磷、全钾、水解氮及水解磷均最低；土壤养分库综合指数变化范围为24.33～295.93，排序为IⅣ（231.96）＞IⅢ（193.46）＞IⅡ（70.90）＞IⅠ（59.57）＞IⅤ（35.59）；土壤养分要素的相关性分析结果表明，有机质与全磷、全磷与速效磷、全氮与全钾、水解氮与速效磷均呈显著正相关关系，相关系数分别为 0.5760、0.5961、0.6864 和 0.5701。

EFFECTS OF DIFFERENT LAND USE PATTERNS UNDER CONVERTING POLDERS BACK INTO WETLANDS ON SOIL NUTRIENT POOLS IN THE DONGTING LAKE REGION

Based upon the case of Qianlianghu polder in the Dongting lake region,soil nutrient contents,synthetical indexes of nutrient pool and relative coefficients among soil nutrient indexes were studied for five typical land use patterns under converting polders back into wetlands, which include forestland (Ⅰ),garden land (Ⅱ),dry land (Ⅲ),paddy land (Ⅳ) and waste land (Ⅴ).The results showed that there was an obvious regularity that soil nutrient contents were higher in 0～25 cm soil layers than in 25～50 cm soil layer.In different patterns and 0～50 cm soil layers,the contents of organic matter (OM),total nitrogen (TN),available nitrogen (AN),total phosphorus (TP),available phosphorus (AP),total potassium (TK) and available potassium (AK) were 340～3232 g/kg,223～971 g/kg,1295～11200 mg/kg,2950～6935 g/kg,415～7568 mg/kg,603～3069 g/kg and 3770～21750 mg/kg respectively.The highest contents of TN and the lowest OM occurred in pattern Ⅰ,the highest contents of OM,TK and AP were in pattern Ⅳ,and the highest AN were pattern Ⅲ.However,the contents of TN,TP,TK,AN and AP were the lowest in pattern Ⅴ.Soil nutrient pool synthetical indexes ranged from 2433 to 29593 in five land use patterns,which showed by regularities of 〖WTBX〗IⅣ（23196）＞IⅢ（19346）＞IⅡ（7090）＞IⅠ（5957）＞IⅤ〖WTBZ〗（3559）.Through Pearson coefficient analyzing,it was showed that there existed highly positive relation between OM and TP,TP and AP,TN and TK,AN and AP which relative coefficients were 0.5760,0.5961,0.6864 and 0.5701 respectively.