Decomposition of labelled roots and root-C and -N allocation between soil fractions in mountain grasslands

详细信息	查看全文 | 推荐本文 |

• 作者：Jordi Garcia-Pausas^a ; ^b ; ^{jordi.garcia@ctfc.cat} ; Pere Casals^a ; Pere Rovira^a ; Sara Vallecillo^a ; Maria-Teresa Sebastià ; ^a ; ^c ; Joan Romanyà ; ^d
• 关键词：13C- and 15N- labelled roots ; C and N stabilisation ; Mountain grassland soils ; Particle size fractionation ; Biochemical recalcitrance ; Root decomposition
• 刊名：Soil Biology & Biochemistry
• 出版年：2012
• 期刊代码：96_00380717
• 类别：abs
• 出版时间：June, 2012
• 卷：49
• 期：Complete
• 页码：61-69
• 文件大小：427 K

摘要

Given the high turnover of fine roots in mountain grasslands, knowledge of their decomposition rates and the capacity of mountain grassland soils to stabilize root-derived C are central to understand the role of these ecosystems as potential C sinks. Here we studied the decomposition of fine roots in mountain grasslands and estimated the rates at which root-C and -N incorporated into protected pools at two soil聽depths. For this purpose, we incubated standard ¹³C- and ¹⁵N-labelled wheat roots mixed with unlabelled soil at 5 and 20聽cm depth in two mountain grassland sites. Particle size fractionation allowed the quantification of the labelled wheat root-C and -N allocated to each size fraction (coarse sand, fine sand and silt plus clay sized) as well as their incorporation rates into the finest fraction. Between 62%and 78%root-C remained in the soil after one year of field incubation, faster decomposition being registered at the warmest site. In the following two years, roots decomposed much more slowly. In contrast to reports in the literature, our results indicate that decay rates during the first year were highest in the deep layer. The incorporation of wheat root-derived organic matter into the silt plus clay size fraction was also much greater during the first year of decomposition than in the following two years and also slightly higher in the deep soil than in topsoil. The incorporation rates of root-¹³C and root-¹⁵N into this fraction also suggest that the wheat-derived organic matter associated with this fraction was N-enriched and less recalcitrant (i.e., less resistant to acid hydrolysis) than that recovered from the coarser fractions. Furthermore, recalcitrant organic matter incorporated much more slowly than labile organic matter did. We conclude that the conditions of the subalpine grassland subsoil are more favourable for root decomposition than the topsoil and that the organic matter that incorporates into the protected pool is characterised by a high N content and low biochemical recalcitrance.