PARTICULATE SOIL ORGANIC-MATTER CHANGES ACROSS A GRASSLAND CULTIVATION SEQUENCE
PARTICULATE SOIL ORGANIC-MATTER CHANGES ACROSS A GRASSLAND CULTIVATION SEQUENCE
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DOI：
10.2136/sssaj1992.03615995005600030017x
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发表时间：
1992-05-01
影响因子：
2.9
通讯作者：
ELLIOTT, ET
中科院分区：
文献类型：
--
作者：
CAMBARDELLA, CA;ELLIOTT, ET
为了描述土壤有机质（SOM）周转的动态，已经构建了许多模型，其中大多数包括2到3个动力学定义的有机质库。对这些概念化的SOM库进行物理和化学定义一直很困难。我们描述了一种分散土壤以分离颗粒有机质（POM）组分的简单方法，该组分可能代表草原土壤中一个重要的SOM库。通过将土壤分散在5克/升的六偏磷酸钠中，并使分散的土壤样品通过53微米的筛子来分离POM组分。我们比较了内布拉斯加州西德尼的三种耕作处理（耕种20年）和未受干扰的草原之间的POM和与矿物质结合的碳。原生草皮中的POM碳占土壤总有机碳的39%。20年的裸地休闲、留茬覆盖和免耕管理分别使该组分中的碳含量降低到总有机碳的18%、19%和25%。与草原土壤相比，裸地休闲处理中与矿物质结合的有机质组分的碳含量没有降低，但在免耕和留茬覆盖处理中有所增加。氮动态通常与观察到的碳动态相似。对POM组分的木质素和纤维素含量分析表明，该组分含47%的木质素，木质纤维素指数为0.7。POM组分的稳定碳同位素组成表明，小麦衍生的POM比草衍生的POM周转更快。我们认为POM组分与被不同描述为缓慢、可分解或稳定的有机质的SOM库的特征紧密匹配。
Many models have been constructed in an attempt to describe the dynamics of soil organic-matter (SOM) turnover, most of which include 2 to 3 kinetically defined organic-matter pools. Physical and chemical definition of these conceptualized SOM pools has been difficult. We describe a simple method for dispersion of soil to isolate a particulate organic-matter (POM) fraction that may represent an important SOM pool in grassland soils. The POM fraction was isolated by dispersing the soil in 5 g L-1 hexametaphosphate and passing the dispersed soil samples through a 53-mu-m sieve. We compared POM and mineral-associated C among three tillage treatments (20 yr under cultivation) and an undisturbed grassland at Sidney, NE. The POM C in the native sod represented 39% of the total soil organic C. Twenty years of bare-fallow, stubble-mulch, and no-till management reduced the C content in this fraction to 18, 19, and 25%, respectively, of the total organic C. The mineral-associated organic-matter fraction showed no reduction in C content in the bare-fallow treatment compared with the grassland soil but increased in the no-till and stubble-mulch treatments. Nitrogen dynamics generally mirrored those observed for C. Analysis of the POM fraction for lignin and cellulose content indicated that this fraction was 47% lignin and had a lignocellulose index of 0.7. The stable C-isotope composition of the POM fraction suggests that wheat-derived POM turns over faster than grass-derived POM. We suggest the POM fraction closely matches the characteristics of a SOM pool variously described as slow, decomposable, or stabilized organic matter.