Measurement and estimation of land-use effects on soil carbon and related properties for soil monitoring: a study on a basalt landscape of northern New South Wales, Australia

Abstract

There is a growing need for information relating to soil condition, its current status, and the nature and direction of change in response to management pressures. Monitoring is therefore being promoted regionally, nationally, and internationally to assess and evaluate soil condition for the purposes of reporting and prioritisation of funding for natural resource management. Several technical and methodological obstacles remain that impede the broad-scale implementation of measurement and monitoring schemes, and we present a dataset designed to (i) assess the optimum size of sample site for soil monitoring, (ii) determine optimum sample numbers required across a site to estimate soil properties to known levels of precision and confidence, and (iii) assess differences in the selected soil properties between a range of land-use types across a basalt landscape of northern NSW. Sample site size was found to be arbitrary and a sample area 25 by 25 m provided a suitable estimate of soil properties at each site. Calculated optimum sample numbers differed between soil property, depth, and land use. Soil pH had a relatively low variability across the sites studied, whereas carbon, nitrogen, and bulk density had large variability. Variability was particularly high for woodland soils and in the deeper soil layers. A sampling intensity of 10 samples across a sampling area 25 by 25 m was found to yield adequate precision and confidence in the soil data generated. Clear and significant differences were detected between land-use types for the various soil properties determined but these effects were restricted to the near-surface soil layers (0–50 and 50–100 mm). Land use has a profound impact on soil properties near to the soil surface, and woodland soils at these depths had significantly higher carbon, nitrogen, and pH and lower bulk density than the other land uses. Soil properties between the other non-woodland land-use types were largely similar, apart from a modestly higher carbon content and higher soil acidity under improved pasture. Data for soil carbon assessment should account for equivalent mass, since this significantly modified carbon densities, particularly for the lighter woodland soils. Woodland soils had larger quantities of carbon (T/ha corrected for equivalent mass) than any other land-use type, and in order to maintain the largest quantity of carbon in this landscape, retaining trees and woodland is the most effective option. Results from this work are being used to inform further development the NSW Statewide Soil Monitoring Program.

Soil carbon and related soil properties along a soil type and land‐use intensity gradient, New South Wales, Australia

“…Similar land‐use differences have been found in soils of this region (Dalal & Chan, 2001; Young et al. , 2005; Wilson et al. , 2008, 2010) and, in this part of Australia, land‐use effects on soils appear to be shallower and more readily predicted than soils in other part of the world (Hiederer, 2009).…”

“…Previous work in the region (e.g. Wilson et al. , 2002, 2007b, 2008, 2010) has illustrated that land‐use induced change in soil properties is most strongly expressed in the near surface layers and so, the soil core was subdivided into discrete depth increments (0–5 cm, 5–10 cm, 10–20 cm and 20–30 cm depths) to elucidate patterns with increasing soil depth.…”

Factors Controlling Soil Organic Carbon Stocks with Depth in Eastern Australia

“…Land use, as represented by LDI is shown to have a relatively low influence on SOC levels at this sub-continental scale, but it may be at least partly masked by the vegetation cover factor. Its influence appears to decline further with depth, similarly reported by others (Luo et al, 2010;Wilson et al, 2010Wilson et al, , 2011Allen et al, 2013;Badgery et al, 2013), Nevertheless the factor is still considered important in subsoils (Guo and Gifford, 2002;Wright et al, 2007;Meersmans et al, 2009;Follett et al, 2009;Vasques et al, 2010;Rumpel and Kögel-Knabner 2011). It has been suggested that SOC in deeper soil layers might reflect historic rather than current land use (Schulp and Veldkamp, 2008;Wilson and Lonergan, 2013).…”

“…Difficulties achieving this have been attributed to the inherent variability of SOC under uniform soil types (Batjes, 1996;Cotching, 2012) even under localized areas with apparently uniform environmental conditions (Cerri et al, 2000;Wilson et al, 2010), and difficulty in reliably estimating bulk densities .…”

Targeting perennial vegetation in agricultural landscapes for enhancing ecosystem services

“…For the Great Plains region, McLauchlan 142 estimated that reestablishment of perennial grasslands on former agricultural lands could rebuild soil organic C pools to levels equivalent to unplowed native prairie within 55-75 years, while Matamala et al 145 estimated that within a century restored tallgrass prairie vegetation in Illinois would reach 50% of its soil C storage potential. Differences in C accrual rates across sites and soil depths due to variation in root distribution, rhizosphere activity 146,147 and vertical retranslocation of soil C 47,146 may account for some of this variability.…”