活性铁铝矿物对农田土壤有机碳固定的研究

Organic carbon fixation by iron and aluminum reactive minerals in farmland soil

为了解活性铁铝矿物对农田土壤有机碳固定的贡献,量化了重庆西部地区不同土壤类型与耕作制度下61个典型农田土壤的表层(0~30 cm)、中层(30~60 cm)、底层(60~100 cm)3层的活性铁铝矿物所固定的有机碳量(OC_(Fe-Al))。结果表明:OC_(Fe-Al)表现为表层(均值2.02 g·kg^(-1))>中层(均值1.37 g·kg^(-1))>底层(均值1.19 g·kg^(-1));OC_(Fe-Al)占土壤总有机碳的范围为12.8%~83.6%。3层土壤的活性铁铝矿物平均固碳量,在不同土壤类型中,石灰岩土最高(1.83 g·kg^(-1)),紫色土最低(1.40 g·kg^(-1));在不同耕作制度中,水旱轮作用地最高(1.65 g·kg^(-1)),旱作用地最低(1.50 g·kg^(-1));在不同地形中,陡坡地最低(0.97 g·kg^(-1)),平地(1.53 g·kg^(-1))与缓坡地(1.54 g·kg^(-1))较高;OC_(Fe-Al)与土壤Fe、Al及TOC含量呈显著正相关(P<0.01),与土壤pH呈显著负相关(P<0.01)。总体而言,活性铁铝矿物固碳是土壤固碳的重要机制且对底层土壤碳库的贡献率更大;而土壤类型、耕作制度、土壤pH等均会影响活性铁铝矿物对土壤有机碳的固定。

In order to understand the contribution of organic carbon retained by iron and aluminum reactive minerals in farmland soils,the amount of organic carbon fixed by the iron and aluminum reactive minerals(OC_(Fe-Al))on the surface layer(0~30 cm),middle layer(30~60 cm),and bottom layer(60~100 cm)of 61 typical farmland soils of different soil types and farming systems in western Chongqing was quantified.The results showed that:OC_(Fe-Al) was in the following order:surface layer(mean 2.02 g·kg^(-1))>middle layer(mean 1.37 g·kg^(-1))>bottom layer(mean 1.19 g·kg^(-1)),accounting for 12.8%~83.6%of the total soil organic carbon.The average OC_(Fe-Al) in the three soil layers was the highest in limestone soils(1.83 g·kg^(-1))and lowest in purplish soils(1.40 g·kg^(-1))among different soil types.The paddy-upland rotation crop displayed the highest OC_(Fe-Al)(1.65 g·kg^(-1))in different tillage systems,whereas the uplands had the lowest(1.50 g·kg^(-1)).In terms of terrain,gentle-sloped and flat land had the highest OC_(Fe-Al) and steep-sloped land the lowest(1.54,1.53 g·kg^(-1),and 0.97 g·kg^(-1),respectively).The carbon sequestration of iron-and aluminum-bearing reactive minerals was significantly positively correlated with Fe,Al,and soil total organic carbon contents(P<0.01)and negatively correlated with soil pH(P<0.01).In general,the carbon sequestration of iron and aluminum reactive minerals is an important mechanism for soil carbon sequestration and contributes more to the bottom soil carbon pool.Soil type and the farming system will affect the iron and aluminum reactive minerals′ability to fix soil organic carbon.