Long-term grazing effects on grassland soil properties in southern British Columbia

Abstract

<jats:p>Evans, C. R. W., Krzic, M., Broersma, K. and Thompson, D. J. 2012. Long-term grazing effects on grassland soil properties in southern British Columbia. Can. J. Soil Sci. 92: 685–693. Although grazing effects on soil properties have been evaluated on various temperate grasslands, no study has dealt with these effects in the southern interior of British Columbia. The objective of this study was to determine the effects of spring versus fall season grazing as well as grazing [at a moderate rate of 0.6 animal unit months (AUM) ha<jats:sup>−1</jats:sup>] versus non-grazing by beef cattle on selected soil properties. Effects were determined 20 and 30 yr after the establishment of the field experiment. Soil properties were determined for the 0- to 7.5-cm, 7.5- to 15-cm, and 15- to 30-cm depths. In comparison with fall grazing, spring grazing had greater soil bulk density, greater mechanical resistance within the top 15 cm of the soil profile, higher pH, and lower polysaccharides. This was true for both 20 and 30 yr of treatment. Grazing effects on aggregate stability were observed only after 30 yr with spring grazing leading to a more stable structure with a mean weight diameter (MWD) of 1.5 mm and 32% and 10% of aggregates in the 2- to 6-mm and 1- to 2-mm size fractions, respectively, compared with a MWD of 1.0 mm and 20% and 6% under fall grazing. Greater soil bulk density, mechanical resistance, and pH were observed under the grazed treatment relative to the control without grazing, but as we used a moderate stocking rate the impacts were not as great as in previous studies, which used heavy stocking rates. Our findings show that long-term grazing at a moderate stocking rate of 0.6 AUM ha<jats:sup>−1</jats:sup>did not have critical detrimental effects on soil properties as some land managers and ranchers have suggested.</jats:p>

Long-term impacts of season of grazing on soil carbon sequestration and selected soil properties in the arid Eastern Cape, South Africa

“…Reduced root allocation usually influences soil C inputs and also decreases N retention within the soil (Derner et al 2006). Our results confirm the findings of Evans et al (2012) who reported reduced SOC when lands grazed during plant growing season (spring to summer) partly due to increased soil compaction. On the other hand, in the WG treatment vegetation was usually grazed after fully matured, and as a result plants were resistant to grazing pressure (Du Toit et al 2011).…”

“…reported for arid rangelands (Lal 2000). The C and N stock obtained in this study is closer to the average for Africa (Beukes and Cowling 2003;Koetze et al 2013) while smaller than reports elsewhere in the world (Evans et al 2012;Liu et al 2012). ).…”

“…There is limited information on factors controlling the spatial and temporal variability of SOC stocks through C decomposition and dynamics, and other soil properties under different grazing managements (Kotze et al 2013). Although season and frequency of grazing are factors manipulated to achieve desired management goals in grazing lands (Evans et al 2012), little has been documented about the long-term effects of seasonal grazing management on C and N dynamics in the arid karoo biome of South Africa. Moreover, due to multifaceted interactions between C and N in a karoo ecosystem, grazer effect on SOC is highly context-specific (McSherry and Ritchie 2013) and site-specific information is essential for various management scenarios (Derner and Schuman 2007;Du Preez et al 2011).…”

Comparing grazing and resting electivity of beef cattle for BC bunchgrass communities using GPS collars

“…The high concentration of resting sites in the Dis and Poa communities may cause significant soil compaction to a greater extent than reported for cattle use in the Pse community (Evans et al 2012) because the risk of soil compaction is greater for wet soil. Soil compaction in the Dis community may reduce habitat quality for the Great Basin spadefoot toad, a species at risk, which inhabits these ephemeral ponds (Karl Larsen, unpublished observation).…”

Vegetation traits and soil properties in response to utilization patterns of grassland in Hulun Buir City, Inner Mongolia, China

“…Trampling of grazing animals was reported to affect soil by increasing bulk density and mechanical resistance, and reducing porosity, water infiltration, and aggregate stability (Evans et al, 2012). Zhou et al (2010) denoted that grazing and trampling by livestock cause deterioration of soil physical properties and increased soil erodibility.…”