Productivity of two Douglas fir/subclover/sheep agroforests compared to pasture and forest monocultures

Abstract

Resource sharing between tree and forage plant components in silvopastoral systems includes a complex set of facilitative and competitive interactions. To the extent that facilitation exceeds competition, agroforests are expected to outyield monocultures of their components. Pasture and Douglas fir (Pseudotsuga menziesii) tree production of young agroforests was compared to pasture and forest monocultures under both grid and cluster patterns of tree planting near Corvallis, Oregon, USA, during 1983USA, during -1987. The height and diameter growth of forest and agroforest trees was similar, regardless of tree planting pattern. Five-year average annual forage production was 6500, 5800, and 2800 kg ha ~ on pasture, agroforest, and forest plots, respectively. The total cumulative 1982-1987 above-ground phytomass yield of forage plus trees was similar for pasture and conventional grid forest monocultures. The total productivity of agroforests, however, was over 30% greater than either pasture or forest components grown in monoculture. Approximately 1.6 ha (0.96 ha forest + 0.64 ha pasture) of monocultures would be needed to equal the productivity of 1 ha of agroforest.

Tree establishment and growth using forage ground covers in an alley-cropped system in Midwestern USA

“…Similar to findings by Sharrow et al (1996), where 1.0 ha of agroforest approximated 0.96 ha of forest and 0.64 ha of clover, the combination of hay harvests in a black walnut alley-cropped system were found to provide greater returns than black walnut alone (Holzmueller 2003). Although tree biomass yields were not measured at this point in the study, similar studies (Colletti et al 1991) reported Populus yields of up to 13.2 t ha À1 yr À1 .…”

“…Less competitive, forage-based agroforestry systems have been shown to be more compatible than graincrop-based alley-cropping systems, due to the shading from mature tree species having a greater impact on grain crops compared to forages (Garrett and Kurtz 1983;Gillespie 1996). Greater system productivity (increased timber production, higher crop yields and/or livestock growth) has been obtained in various silvopastoral systems, including cattle grazing under loblolly pine (Pinus taeda L.) (Harwell and Dangerfield 1991), subterranean clover (Trifolium subterraneum L.) intercropped with Douglas-fir (Pseudotsuga menziesii L.) (Sharrow et al 1996), rhizoma-peanut (Arachis glabrata L.) under pine (Pinus spp.) (Johnson et al 1994), tall fescue (Festuca arundinacea L.) and orchardgrass (Dactylis glomerata L.) under mature (35-yr-old) black walnut (Garrett and Kurtz 1983), and red clover with black walnut and honeylocust trees (Gleditsia triacanthos L.) (Alley et al 1999).…”

Carbon Storage of Different Soil‐Size Fractions in Florida Silvopastoral Systems

“…Th e increase in SOC under silvopasture in the current study could be a direct manifestation of the higher rates of net primary productivity (NPP) in tree-based land use relative to open grass pasture, as reported by Archer et al (2001) and Hibbard et al (2001). Better resource sharing and use and consequent productivity increases in multi-species systems compared with single-species stands of the component species have been well documented from a number of agroecosystems (e.g., Lefroy et al, 1999), including agroforestry systems (Van Noordwijk et al, 1998;Sharrow et al, 1996). Sharrow et al (1996), for instance, reported that 10-yr-old Douglas fi r (Pseudotsuga menziesii (Mirbel) Franco)/grass/clover (Trifolium spp.)…”

“…Better resource sharing and use and consequent productivity increases in multi-species systems compared with single-species stands of the component species have been well documented from a number of agroecosystems (e.g., Lefroy et al, 1999), including agroforestry systems (Van Noordwijk et al, 1998;Sharrow et al, 1996). Sharrow et al (1996), for instance, reported that 10-yr-old Douglas fi r (Pseudotsuga menziesii (Mirbel) Franco)/grass/clover (Trifolium spp.) pasture/sheep agroforest was over 30% greater in total productivity than pasture or forest components grown in monoculture.…”

Soil compaction by grazing livestock in silvopastures as evidenced by changes in soil physical properties

“…Restorative effects of physical processes such as shrink/swell of vertic soils (Taddese et al 2002) and freezing/thawing and biological processes such as microchannel formation by soil fauna may vary with change in soil surface microclimate and vegetation structure in forests vs. silvopastures. Increased forage production on silvopastures compared to forests (Sharrow et al 1996;Clason and Sharrow 2000) increases soil organic matter (Sharrow and Ismail 2004) and potentially provides a cushion of stubble between hoof and soil during grazing (Greenwood and McKenzie 2001). However, compaction effects are cumulative over the first few impacts (McNabb et al 2001;Lei 2004), so higher producing sites, such as silvopastures, may be more subject to compaction because of the greater number of animal days of grazing they will support (Krzic et al 1999(Krzic et al , 2001.…”