Spatial distribution of soil phosphorus and herbage mass in beef cattle pastures: effects of slope aspect and slope position

Abstract

Characterizing and assessing spatial distribution of soil phosphorus and herbage mass in relation to landscape properties, land use, or landscape positions is important for understanding how pasture sustainability can be managed and improved properly. Our reason for conducting this study was to determine the effects of different slope aspects and slope positions on spatial distribution of soil phosphorus and herbage mass in subtropical pastures. Soil and forage samples were collected from contiguous south-, north-, east-, and west-facing slopes across different landscape positions (top slope, middle slope, and bottom slope) in 100 ha of bahiagrass (Paspalum notatum)-based pastures from 2003 to 2006 in subtropical region of southeastern USA. Averaged across years, soils on the north-facing slope contained the greatest amount of soil phosphorus (12.4 ± 2.7 mg kg -1 ) when compared with other slope aspects. Slope aspect may be acting as an important topographic factor influencing local site microclimate mainly because it determines the amount of solar radiation received. The greatest herbage mass (averaged across year) of 2,967 ± 980 kg ha -1 and the highest phosphorus accumulation of 7.7 ± 3.0 kg ha -1 for bahiagrass were from the top slope position. There was a significant (P B 0.05) decrease in the average herbage mass and phosphorus accumulation with decreasing slope (top to middle slope). Between the top slope and the bottom slope, herbage mass declined from 2,967 ± 980 to 1,805 ± 370 kg ha -1 while phosphorus accumulation was reduced by approximately 40% (7.7-4.6 kg ha -1 ). Results of our study may increase awareness on how the arrangement of food, water, and shelter and their interactions with topographic and landscape features can significantly influence the movement of animals and utilization of different pastures' resources. While our study supports our hypothesis that slope aspect and slope position could be of relative importance in controlling spatial distribution of soil phosphorus and herbage mass, broad knowledge of cattle movement in pasture situations is as critical to understanding their impact on agroecosystems.

Differences in early dynamics and effects of slope aspect between naturally regenerated and planted Pinus sylvestris woodland on inland dunes in Poland

“…Similarly, Calvo et al (2008) found that the density and height of Pinus pinaster seedlings were higher on north-facing slopes than on south-facing slopes in the three years following a forest fire in north-west Spain. The generally higher moisture and/ or fertility of soils on north-facing slopes could explain these results (Rezaei & Gilkes 2005, Calvo et al 2008, Sigua et al 2011. The Ellenberg's indicator values obtained in this study confirmed that soil moisture was higher on the north-facing slopes of the examined sites.…”

“…In the northern hemisphere, north-facing slopes receive less solar radiation than south-facing slopes, and thus generally have a more humid microclimate, more fertile soil, and lower temperatures (Cantlon 1953, Egli et al 2006, Sewerniak et al 2011, Sigua et al 2011. Hence, aspect also strongly influences the species composition of trees, shrub communities, and herb layers (Yimer et al 2006, Jankowski 2010, Sewerniak et al 2011.…”

Forest Understorey Vegetation: Colonization and the Availability and Heterogeneity of Resources

“…Additionally, poorly drained lowlands possess a greater abundance and diversity of understorey vegetation than rapidly-draining uplands, which suggests that the abundance and diversity of understorey vegetation are positively influenced by the availability of soil moisture [77]. In the Northern Hemisphere, north-facing slopes typically favour higher abundance and diversity of understorey vegetation than do south-facing slopes, despite less light availability, but more soil moisture [80][81][82]. Moreover, access to soil moisture is intimately related with time since a stand-replacing fire disturbance.…”

“…Further, elevation, slope aspect, and slope position play a considerable role in the development of understorey vegetation communities [15,18,112,113]. In the Northern Hemisphere, northern slopes typically favor more highly abundant understorey vegetation and diversity than southern slopes, as the damp forest microclimates and fertile soils of north-facing slopes promote the generation of understorey vegetation [80][81][82]. In mountain landscapes, topography can affect the hydrological conditions of the area by controlling the patterns of evapotranspiration and water flow, which may significantly change the availability of resources and heterogeneity in the understorey layer (e.g., light, soil moisture, and nutrients), thereby affecting the composition and diversity of understory vegetation [114,115].…”

Changes in Soil C, N, and P Concentrations and Stoichiometry in Karst Trough Valley Area under Ecological Restoration: The Role of Slope Aspect, Land Use, and Soil Depth

“…Slope aspect is widely regarded as the crucial topography factor altering soil C, N, and P concentrations and stoichiometry [11][12][13] as a result of the distinct microclimates in different aspects [14]. Nevertheless, the effects of slope aspect on C, N, and P traits are still unclear.…”