The role of plants and land management in sequestering soil carbon in temperate arable and grassland ecosystems

• Published in: Geoderma 2005-09, Vol.128 (1), p.130-154
• Main Authors: Rees, R.M., Bingham, I.J., Baddeley, J.A., Watson, C.A.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Carbon sequestration; CO 2; Cropping systems. Cultivation. Soil tillage; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Land management; Rhizodeposition; Rhizosphere; Roots; Soil management; Soil organic matter; Soil respiration; Soil tillage; Soils; Surficial geology; Tillage. Tending. Growth control
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2004.12.020

Global climate change and concerns about soil quality have led to a widespread interest in the opportunities that are available to sequester carbon in soils. To achieve a better understanding of the changes in C storage, we need to be able to accurately measure and model inputs and losses of C from soils. This in turn requires a thorough understanding of the biological processes involved and the way in which they are influenced by the soil's physical and chemical environment. The amount of C present in a soil is determined by the difference between C addition and C loss. Because these fluxes are large relative to changes in C storage, net storage can be very difficult to measure, particularly in the short term. Carbon is added to soil from plant and animal materials deposited on the soil surface. It is known that approximately 50% of C assimilated by young plants can be transferred below ground; some is used for root construction and maintenance as well as root respiration; some organic C is lost to the soil through exudation and root turnover. A comparison of eight studies has shown that the input to the soil of root derived organic C during a growing season can range between 0.1 and 2.8 t C ha −1. Quantifying inputs from different processes has proved difficult and the relative importance of exudation and root death under field conditions remains uncertain. The chemical composition of substrates released by exudation and root death is known to be very different. Exudates contain high concentrations of soluble organic substrates and as a consequence are highly labile, whereas additions of C from root death have structural organic substrates with lower potential decomposition rates. Losses of C from soil occur as a consequence of plant and microbial respiration. However, identifying the source of evolved CO 2, whether it be from root or microbial respiration, is much more difficult. Some new methods using isotopic labelling and pool dilution have been developed to separate plant and microbial respiration, and despite difficulties, these promise to provide valuable information on the processes of C input and loss from soils. At a field scale measurements and models would suggest that soil and crop management can play a significant role in determining the extent of C sequestration by soils and the proportion of labile C present. A comparison of 11 field studies showed that soil respiration varies between 4 and 26 t C ha −1 year −1, with management such as ti