The changes in soil organic matter in a forest-cultivation sequence traced by stable carbon isotopes

Abstract

There is an obvious difference in δ13C values between plants that assimilate carbon via the C3 photosynthetic pathway and those that do so by the C4 photosynthetic pathway. In terms of this characteristic, we analysed the organic carbon content and δ13C values of total soil and δ13C values in different size and density fractions of profile-soil samples either in farmland or in forestland near the Maolan Karst virgin forest, south-west China. This is an area where C3 plants grew previously, now replaced by C4 plants. Deforestation has accelerated the decomposition rate of soil organic matter and reduced the proportion of active components in soil organic matter and thus soil fertility. The δ13C values of different size fractions in forest soil are δ13Ccoarse sand < δ13Cfine sand < δ13Ccoarse silt < δ13Cclay < δ13Cfine silt, and the δ13C values of different size fractions in farmland soil are δ13Ccoarse sand > δ13Cfine sand > δ13Ccoarse silt > δ13Cclay > δ13Cfine silt, indicating that soil organic matter is fresh in coarse sand and oldest in fine silt. The δ13C values of different density fractions in forest soil are δ13Clight < δ13Cheavy, and the δ13C values of different density fractions in farmland soil are δ13Clight > δ13Cheavy, indicating that the soil organic matter is fresh in light fractions and old in heavy fractions.

Comparison and detection of total and available soil carbon fractions using visible/near infrared diffuse reflectance spectroscopy

“…Therefore, total soil C is not always a useful indicator for monitoring purposes, where the changes in land management are not drastic enough to result in significant total C changes and early detection of the changes in soil C status is desirable. On the other hand, various labile C forms are known to respond more rapidly to changes in land use than bulk soil organic C (OC), which could serve as early indicators for overall C stock change and offer alternatives for environmental performance monitoring (Ahn et al, 2009;Angers and Mehuys, 1990;Leifeld and Kogel-Knabner, 2005;Liu et al, 2003;Römkens et al, 1999;Sarkhot et al, 2008).…”

Effects of forest management intensity on carbon and nitrogen content in different soil size fractions of a North Florida Spodosol

“…For example, identifying the pools responsible for diVerent functions such as short-term nutrient turnover (e.g., sand size fraction) and long-term C storage (e.g. Wne silt fraction; Liu et al 2003) may help in the development of more accurate C dynamics models.…”

Plant growth, biomass partitioning and soil carbon formation in response to altered lignin biosynthesis in Populus tremuloides

“…In order to improve understanding of how plant inputs and tissue quality influence soil C formation, model systems are needed that: simultaneously vary lignin quantity or quality without changing other plant properties that can influence decomposition rates; and allow for tracing the fate of C from plants into soils. The genetic alteration of lignin biosynthesis in aspen (Li et al ., 2003) coupled with 13 C isotope techniques (Amundson et al ., 1998; Collins et al ., 1999; Liu et al ., 2003; Loya et al ., 2003; Pataki et al ., 2003; Giardina et al ., 2004; Hobbie et al ., 2004; Steinmann et al ., 2004; Heath et al ., 2005) offers a powerful approach for understanding how plants influence ecosystem processes.…”