Soil Change: Impacts and Responses

Peer reviewe

Panel discussion and Q&A

Other Approaches to Adaptatio

Time for non-illuvial Bt horizons?

The Bt horizon is the diagnostic horizon of the Luvisolic Order in Canada. According to the Canadian System of Soil Classification (CSSC), the Bt must be formed from clay illuviation through the processes of lessivage (i.e., physical transport of clay). In a study of a Luvisol catena in the central Saskatchewan, we demonstrate that Ae/Bm horizons overlying IIBt horizons are formed in a sandy mantle overlying till (i.e., a lithological discontinuity) and that the sandy mantle contributed negligible amounts of illuvial clay despite the presence of clay skins on ped surfaces in the IIBt horizon. We extended the results of this study to the regional scale by examining sand fractions in 63 pedons of Luvisol-dominated soil associations from soil surveys in the Northern Forest Reserves (between latitudes 53The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Will changes in climate and land use affect soil organic matter composition? Evidence from an ecotonal climosequence

As the largest actively cycling pool of terrestrial C, the response of soil organic matter (SOM) to climate change may greatly affect global C cycling and climate change feedbacks. Despite the influence of SOM chemistry—here defined as soil organic C (SOC) and soil organic N (SON) functional groups and compounds—on decomposition, uncertainty exists regarding the response of SOM chemistry to climate change and associated land use shifts. Here, we adopt a climosequence approach, using latitude along a uniform glacial till deposit at the grassland–forest ecotone in central Canada as a surrogate for the effects of climate change on SOM chemistry. Additionally, we evaluate differences in SOM chemistry from paired native grassland, native trembling aspen (Populus tremuloides) forest, and arable soil profiles to investigate the effects of likely climate-induced land use alterations. The combination of C and N K-edge X-ray absorption near edge structure (XANES) with pyrolysis-field ionization mass spectrometry (Py-FIMS) techniques was used to examine SOM chemistry at atomic and molecular scales, respectively. These techniques revealed only modest differences in surface SOM chemistry related to land use and latitude. Greater variation was apparent in the vertical stratification of SOM constituents from soil depth profiles. These findings indicate that pedon-scale processes have greater control over SOM chemistry than do processes operating on landscape (e.g. land use) and regional (e.g. climate) scales. Additionally they imply that SOM chemistry is largely unresponsive to climatic change on the magnitude of the mean annual temperature (MAT) gradient under study (~ 0.7 °C), despite its location at the grassland–forest boundary highlighting its sensitivity, and is similarly unresponsive to associated land use shifts