Characterization of recently 14C pulse-labelled carbon from roots by fractionation of soil organic matter

被引:11
作者
Bhupinderpal-Singh
Hedley, MJ
Saggar, S
机构
[1] Massey Univ, Nat Resources Inst, Palmerston North, New Zealand
[2] Landcare Res, Palmerston North, New Zealand
关键词
D O I
10.1111/j.1365-2389.2004.00669.x
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
The inability of physical and chemical techniques to separate soil organic matter into fractions that have distinct turnover rates has hampered our understanding of carbon ( C) and nutrient dynamics in soil. A series of soil organic matter fractionation techniques ( chemical and physical) were evaluated for their ability to distinguish a potentially labile C pool, that is 'recent' root and root-derived soil C. 'Recent' root and root-derived C was operationally defined as root and soil C labelled by (CO2)-C-14 pulse labelling of rye grass - clover pasture growing on undisturbed cores of soil. Most ( 50 - 94%) of total soil + root C-14 activity was recovered in roots. Sequential extraction of the soil + roots with resin, 0.1 M NaOH and 1 M NaOH allocated 'recent' soil + root C-14 to all fractions including the alkali-insoluble residual fraction. Approximately 50% was measured in the alkali-insoluble residue but specific activity was greater in the resin and 1 M NaOH fractions. Hot 0.5 M H2SO4 hydrolysed 80% ofthe C-14 in the alkali-insoluble residue of soil + roots but this diminished specific activity by recovering much non-C-14 organic matter. Pre-alkali extraction treatment with 30% H2O2 and post-alkali treatment extractions with hot 1 M HNO3 removed organic matter with a large C-14 specific activity from the alkali-insoluble residue. Density separation failed to isolate a significant pool of 'recent' root-derived C-14. The density separation of C-14-labelled roots, and roots remixed with non-radioactive soil, showed that the adhesion of soil particles to young C-14-labelled roots was the likely cause ofthe greater proportion of C-14 in the heavy fraction. Simple chemical or density fractionations of C appear unsuitable for characterizing 'recent' root-derived C into fractions that can be designated labile C ( short turnover time).
引用
收藏
页码:329 / 341
页数:13
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