Carbonate recrystallization in root-free soil and rhizosphere of Triticum aestivum and Lolium perenne estimated by 14C labeling
Carbonate recrystallization in root-free soil and rhizosphere of Triticum aestivum and Lolium perenne estimated by 14C labeling
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DOI：
10.1007/s10533-010-9456-z
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发表时间：
2011-04-01
期刊：
影响因子：
4
通讯作者：
Kuzyakov, Yakov
中科院分区：
文献类型：
--
作者：
Gocke, Martina;Pustovoytov, Konstantin;Kuzyakov, Yakov
在干旱和半干旱条件下，土壤中的次生碳酸盐是由土壤母质中的Ca 2+与来自根和根际微生物呼吸的溶解CO2沉淀而形成的。次生CaCO 3的δ C-13值记录了以前植被的光合作用途径，因此被用作古环境研究的工具。成土碳酸盐岩形成的时间尺度以及几个环境因素的影响是至关重要的，但知之甚少。用碳14同位素交换法估算了成土碳酸盐岩的重结晶速率。（CO2）-C-14被植物吸收，经呼吸进入根际，再通过原生黄土碳酸盐重结晶进入次生碳酸盐中。随着（CO2）-C-14脉冲次数的增加，根际C-14在黄土CaCO 3中的回收量线性增加，导致小麦和黑麦草的重结晶速率分别为3.2 × 10（-5）和2.8 × 10（-5）天（-1）。在黄土接近根，重结晶率的两倍以上的高。外推这些速率，我们表明，几百年是必要的原生黄土CaCO 3在无根基板完全重结晶，假设原生和次生碳酸盐重结晶几次。相比之下，如果根周围形成碳质结壳，阻碍重复重结晶，则根际黄土中的这一过程可能只需几十年。这表明根际过程（如根和微生物的呼吸，分泌）次生碳酸盐形成的重要性。
Under arid and semiarid conditions, pedogenic (secondary) carbonates are formed in soil by precipitation of Ca2+ from soil parent material with dissolved CO2 originating from root and rhizomicrobial respiration. delta C-13 values of secondary CaCO3 record the photosynthetic pathway of former vegetation and is therefore used as a tool for paleoenvironmental studies. The time scale of pedogenic carbonate formation as well as the influence of several environmental factors are crucial, yet poorly known. We estimated the recrystallization rate of pedogenic carbonate by the C-14 isotopic exchange method. (CO2)-C-14 was assimilated by plants, respired into the rhizosphere and subsequently incorporated into secondary carbonate by recrystallization of primary loess carbonate. With ascending number of (CO2)-C-14 pulses, the amount of rhizosphere C-14 recovered in loess CaCO3 increased linearly, leading to recrystallization rates of 3.2 x 10(-5) and 2.8 x 10(-5) day(-1) for wheat and ryegrass, respectively. In loess close to roots, recrystallization rates more than twice as high were obtained. Extrapolating these rates we showed that several hundred years are necessary for complete recrystallization of primary loess CaCO3 in root-free substrate, assuming that both primary and secondary carbonate is recrystallized several times. In contrast, the process probably takes only decades in rhizosphere loess if carbonaceous encrustations form around the root, impeding repeated recrystallization. This indicates the importance of rhizosphere processes (e.g. respiration of roots and microorganisms, exudation) for secondary carbonate formation.