Formulation of pasture seed mixtures with reference to competition and succession in pastures.

Harris, W.; Tow, P. G.; Lazenby, Alec

doi:10.1079/9780851994413.0149

Cited by 17 publications

(18 citation statements)

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“…An outcome of our simulation modeling was that genotypic diversity of the foundation species, measured as niche spacing, remained constant at the local scale through time even though individual poorly adapted genotypes were extirpated from the assembling community. Experiments with cultivar mixtures have shown genetic shifts in sown mixtures with superior genotypes assuming local dominance at the expense of less competitive genotypes (Harris 2001). Under these conditions, local dominance of a highly adapted and dominant genotype of a foundation species is likely to lead to low diversity of subordinate species except where local environmental heterogeneity allows for the maintenance of species diversity through coexistence (Taylor and Aarssen 1990, Baer et al 2004, 2005, Levine and HilleRisLambers 2009).…”

Section: Discussionmentioning

confidence: 99%

Effects of foundation species genotypic diversity on subordinate species richness in an assembling community

Gibson

Allstadt

Baer

et al. 2011

Oikos

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Foundation (dominant or matrix) species play a key role in structuring plant communities, influencing processes from population to ecosystem scales. However, the effects of genotypic diversity of foundation species on these processes have not been thoroughly assessed in the context of assembling plant communities. We modified the classical filter model of community assembly to include genotypic diversity as part of the biotic filter. We hypothesized that the proportion of fit genotypes (i.e. competitively superior and dominant) affects niche space availability for subordinate species to establish with consequence for species diversity. To test this hypothesis, we used an individual-based simulation model where a foundation species of varying genotypic diversity (number of genotypes and variability among genotypes) competes for space with subordinate species on a spatially heterogeneous lattice. Our model addresses a real and practical problem in restoration ecology: choosing the level of genetic diversity of re-introduced foundation and subordinate species. Genotypic diversity of foundation species significantly affected equilibrium community diversity, measured as species richness, either positively or negatively, depending upon environmental heterogeneity. Increases in genotypic diversity gave the foundation species a wider niche breadth. Under conditions of high environmental heterogeneity, this wider niche breadth decreased niche space for other species, lowering species richness with increased genotypic diversity until the genotypes of the foundation species saturated the landscape. With a low level of environmental heterogeneity, increasing genotypic diversity caused the foundation species niche breadth to be overdispersed, resulting in a weak positive relationship with species richness. Under these conditions, some genotypes are maladapted to the environment lowering fitness of the foundation species. These effects of genotypic diversity were secondary to the larger effects of overall foundation species fitness and environmental heterogeneity. The novel aspect of incorporating genotype diversity in combination with environmental heterogeneity in community assembly models include predictions of either positive or negative relationships between species diversity and genotypic diversity depending on environmental heterogeneity, and the conditions under which these factors are potentially relevant. Mechanistically, differential niche availability is imposed by the foundation species.

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Section: Discussionmentioning

confidence: 99%

Effects of foundation species genotypic diversity on subordinate species richness in an assembling community

Gibson

Allstadt

Baer

et al. 2011

Oikos

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“…Further, our assessment of 'persistence' did not consider changes in the genotypic or phenotypic structure of the ryegrass populations compared with the original seed sown; such changes may influence the DM yield of the pasture (Harris 2001;Parsons et al 2011). Genotypic and phenotypic changes are the subject of current research using the survivor populations from the paddocks included in this study.…”

Section: Survey Methods and Data Limitationsmentioning

confidence: 98%

Botanical survey of perennial ryegrass-based dairy pastures in three regions of New Zealand: implications for ryegrass persistence

Tozer

Chapman

Bell

et al. 2014

New Zealand Journal of Agricultural Research

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A botanical survey of 24 commercial dairy pastures ranging in post-sowing age and perennial ryegrass type (mid-season diploid, late-season diploid, tetraploid) was undertaken in each of Waikato-Bay of Plenty (BoP), Taranaki and Canterbury during autumn/winter. The mean perennial ryegrass proportion (85% of total DM) and tiller density (3252 m −2 ) was greatest in Canterbury and the broadleaved weed proportion lowest (2%). Conversely, Waikato-BoP had the lowest ryegrass proportion (59%), tiller density (1817 m −2 ) and greatest proportion of broadleaved weeds (15%), with Taranaki intermediate. Tiller density was greater in pastures sown with diploid rather than tetraploids (averaging 3033 vs. 1784 m −2 ). Grass grub (Costelytra zealandica, 11 m −2 ) populations were lowest in the youngest age category pastures where nematode populations were highest (80 g −1 dry soil). The soil seedbank was dominated by unsown species (with total species emergence averaging 4594 seeds m −2 ), with negligible ryegrass emergence.

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“…This requires far greater knowledge and experience than the current, simpler monoculture approach prevalent in North America. A multi‐species approach may sometimes work when insufficient information is available to guide species selection when establishing mixtures. Including multiple grass, legume or other forb species in pastures or rangeland seed mixtures with varying slopes, soils, weed pressures or grazing pressure may result in a less‐uniform pasture but can also result in more successful establishment across the entire diverse landscape (Harris, 2001). Diversity lends itself to more even forage distribution and nutritive value over seasons and years.…”

Section: What We Know So Farmentioning

confidence: 99%

“…A multi‐species approach may sometimes work when insufficient information is available to guide species selection when establishing mixtures. Including multiple grass, legume or other forb species in pastures or rangeland seed mixtures with varying slopes, soils, weed pressures or grazing pressure may result in a less‐uniform pasture but can also result in more successful establishment across the entire diverse landscape (Harris, 2001).…”

Section: What We Know So Farmentioning

confidence: 99%

Sustainable, low‐input, warm‐season, grass–legume grassland mixtures: mission (nearly) impossible?

Muir

Pitman

Foster

2011

Grass and Forage Science

105

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Grazing lands in warm-temperate and subtropical North America have become less diverse. Pastures are typically grass monocultures, while rangelands are generally managed for the grass components. Overstocking, selective herbicides, fire exclusion and heavy rates of nitrogen fertilizer have contributed to near exclusion of native, warm-season legumes. The simplicity of managing grass monocultures, pasture production responses to nitrogen fertilizer and profitability of grass-only systems have limited interest in legume-based approaches. Changing economics and ecological concerns with ecosystem accumulation of industrial inputs contribute to an increasing interest in legumes. Unlike the development of temperate pasture legumes and recent research in the tropics, legumes tolerant of both freezing temperatures and hot weather have received less attention. Poor establishment, limited persistence and potential invasiveness limit currently available introduced species. Native, herbaceous, warm-season legume species occur throughout warm-temperate North America, but little attention has been directed to these plants as potential forage species. Some success with a few native legume species, primarily in the genus Desmanthus, suggests potential for expanded assessment of forage value of the many species available. Current assessments of native legumes, primarily for conservation purposes, provide an opportunity to expand evaluations of these species for pasture and rangeland potential while economics of livestock production and public interest in ecosystem health are supportive. Experiences with legumes of warm-temperate origin in North America, along with results with temperate and tropical pasture legumes globally, provide a starting point for future efforts at incorporating greater legume diversity in pastures and rangelands of subtropical and warm-temperate regions around the world.

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Formulation of pasture seed mixtures with reference to competition and succession in pastures.

Cited by 17 publications

References 0 publications

Effects of foundation species genotypic diversity on subordinate species richness in an assembling community

Effects of foundation species genotypic diversity on subordinate species richness in an assembling community

Botanical survey of perennial ryegrass-based dairy pastures in three regions of New Zealand: implications for ryegrass persistence

Sustainable, low‐input, warm‐season, grass–legume grassland mixtures: mission (nearly) impossible?

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