长期撂荒对黑土土壤有机碳组分的影响

Effect of long-term fallow on soil organic carbon fractions in black soil

为明确长期撂荒对黑土不同土层土壤有机碳及其组分的影响,以吉林公主岭黑土长期定位试验为对象,选取不施肥和撂荒2个处理,采用改良的Walkley-Black土壤有机碳分组方法,研究不同层次(0~0.2、0.2~0.4和0.4~0.6 m)土壤有机碳及其组分的变化。结果表明:(1)0~0.6 m土壤剖面中,撂荒处理下土壤有机碳储量和固存量分别提高了17.1%和10倍;其中0~0.2和0.2~0.4 m土壤有机碳储量分别提高了27.3%和33.4%,固存量分别提高了8和7倍;而在0.4~0.6 m土层,有机碳储量和固存量则分别降低了26.2%和118%。(2)整体来看,2个处理的组分储量均表现为高活性有机碳(VLC)>惰性有机碳(NLC)>中活性有机碳(LC)>低活性有机碳(LLC);在0~0.2和0.2~0.4 m土层,撂荒能显著提高VLC、LLC、NLC的储量,而对LC没有显著影响;在0.4~0.6 m土层,撂荒显著提高VLC和NLC的储量,而对LC和LLC没有显著影响。(3)在0~0.2和0.2~0.4 m土层,撂荒处理下活性有机碳库(AC)和惰性有机碳库(PC)的碳储量分别显著提高了14.3%、26.5%和39.3%、42.7%,而在0.4~0.6 m土层,AC和PC的碳储量则分别显著降低26.5%和24.7%。同时,相较于AC,撂荒提高了PC所占比例,并且在0~0.2和0.2~0.4 m土层,PC提高的比例相对较大。(4)土壤有机碳与VLC、NLC、LC和LLC的储量呈极显著的正相关关系(P?0.01),VLC与土壤有机碳相关性更为紧密(r=0.998)。上述结果表明:长期撂荒利于表层碳积累和稳定,而较深土层的碳固持能力会变弱;VLC对撂荒的响应较为敏感,可作为撂荒农田土壤有机碳动态的一个敏感性指标。

In order to clarify the effect of long-term fallow on soil organic carbon and its fractions in different layers of black soil,the long-term black soil experiment in Gongzhuling was taken as the object and the soils under without fertilization and fallow treatments were selected.The modified Walkley-Black method was selected to determinate the soil organic carbon fractions to explore the effects of long-term fallow on soil organic carbon and its fractions at different soil layers(0 ~ 0.2, 0.2 ~ 0.4,0.4 ~ 0.6 m).Results showed that(1)In the whole soil profile of 0 ~ 0.6 m,soil organic carbon stock and sequestered increased by 17.1% and 10 times,respectively,and in 0 ~ 0.2 and 0.2 ~ 0.4 m soil layers,the soil organic carbon stock and sequestered increased by 27.3%,33.4% and 8,7 times,respectively,however,in 0.4 ~ 0.6 m soil layer,they were reduced by 26.2% and 118%.(2)Without fertilization and fallow treatments in all soil layers were characterized by very-labile carbon(VLC)>non-labile carbon(NLC)>labile carbon(LC)>less-labile carbon(LLC). In 0 ~ 0.2 and 0.2 ~ 0.4 m soil layers,fallow significantly increased the stock of VLC,LLC and NLC,but with no significant effect on LC.In 0.4 ~ 0.6 m soil layer,fallow significantly increased VLC and NLC,but had no significant effect on LC and LLC.(3)In 0 ~ 0.2 and 0.2 ~ 0.4 m soil layers,active carbon pool(AC)and passive carbon pool(PC)increased significantly by 14.3%,26.5% and 39.3%,42.7%,respectively.However,in the 0.4 ~ 0.6 m soil layer,the carbon stock of AC and PC decreased significantly by 26.5% and 24.7%,respectively.At the same time,compared with AC,fallow increased the proportion of PC,and in the 0 ~ 0.2 and 0.2 ~ 0.4 m soil layers,the increase percentage of PC was relatively large.(4)There was a positive significant correlation between soil organic carbon and VLC,NLC,LC and LLC(P?0.01).VLC was more closely correlated with soil organic carbon(r=0.998).It shows that long-term fallow is conducive to surface carbon accumulation and stability,which will be weaker in deeper soil layers.VLC can be used as a sensitive indicator of soil organic carbon dynamics in fallow cropland.