Seedling Establishment in Adult Neighbourhoods--Intraspecific Constraints in the Regeneration of the Bunchgrass Bouteloua Gracilis

Aguilera, Manuel O.; Lauenroth, William K.

doi:10.2307/2261495

Cited by 114 publications

(97 citation statements)

References 57 publications

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“…The observation that the proportion of B. pictus individual plants that grow in association with less palatable species increases with grazing intensity confirm previous measurements (Oesterheld and Oyarzá bal 2004) and supports a general pattern for the Patagonian steppe. It also raises questions about the implications for other population processes, such as seedling establishment, because other local processes, like interspecific competition, increase in importance (Soriano and Sala 1986;Owens and Norton 1992;Aguilera and Lauenroth 1993;Moretto and Distel 1997;Eccles et al 2002). The response of seedling performance to competition with less palatable grasses was different in the 2 years.…”

Section: Resultsmentioning

confidence: 99%

“…Competition is a common biotic interaction in arid ecosystems (Fowler 1986;Goldberg and Barton 1992;Aguilera and Lauenroth 1993), but its intensity varies in space and time. Because competition occurs between neighbors, the frequency Table 2.…”

Section: Resultsmentioning

confidence: 99%

“…Closeness to a less palatable species promotes the seeding (Oesterheld and Oyarzá bal 2004), but on the other hand, seedling survival can be strongly constrained by competition (Aguilera and Lauenroth 1993). In communities with sparse vegetation, seeds tend to accumulate close to established vegetation (see references in Aguiar and Sala 1997).…”

Section: Introductionmentioning

confidence: 99%

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Interspecific Competition Interacts with the Spatial Distribution of a Palatable Grass to Reduce Its Recruitment

Cipriotti¹,

Aguiar²

2005

REM

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Most arid and semiarid ecosystems around the world have been grazed by domestic herbivores. In many cases, grazing has degraded vegetation and soil. The possibility of restoring rangeland's good condition depends, partially, on the ability of remaining populations of desirable species to recover. In this work, we studied the exact spatial distribution of remaining palatable adult plants in fields with different grazing history (i.e., seed sources) and quantified the effect of interspecific competition with less palatable grasses on seedling emergence and survival (i.e., regeneration constraints). We worked in a Patagonian steppe composed of shrubs and perennial tussock grasses that has been grazed by sheep for .100 years. In order to evaluate the location of seed sources, we mapped the location of a palatable species (Bromus pictus Hook.) in paddocks with different long-term grazing intensity. In addition, we sowed seeds of B. pictus close to 2 dominant, less palatable grasses in 2 different years to evaluate the role of interspecific interactions on regeneration and the effects of climate variability. The proportion of B. pictus plants growing in protected places near less palatable species significantly increased with grazing intensity. Competition effects on emergence, survival, and growth depended on the year's moisture regime. During the dry year, competition with less palatable grasses reduced the emergence, survival, height, and number of leaves of palatable grass seedlings by 30%, 55%, 48%, and 40%, respectively. In the wet year, there were no effects of competition on emergence and height, and the effects on survival depended on the species of the less palatable neighbors. Our study supports the idea that management for recovering degraded rangelands in this ecosystem may benefit from considering the spatial distribution of remaining plants. It also indicates that the susceptibility of demographic processes to interspecific competition depends on the year and neighbor species. ResumenLa mayoría de los ecosistemas á ridos y semiá ridos del mundo han sido apacentados por herbívoros domésticos. En muchos casos, el apacentamiento ha deteriorado la vegetació n y el suelo. La posibilidad de restaurar la buena condició n de estos pastizales depende parcialmente de la habilidad de las poblaciones remanentes de especies deseables para recuperarse. En este trabajo, estudiamos la distribució n espacial exacta de las poblaciones remanentes de plantas adultas de un pasto palatable en pastizales con diferente historial de apacentamiento (fuentes de semillas) y cuantificamos el efecto de la competencia interespecífica con pastos menos palatables sobre la emergencia y supervivencia de plá ntulas (restricciones a la regeneració n). Trabajamos en una estepa semiárida Patagó nica co-dominada por arbustos y pastos perennes, que había sido apacentada por ovinos durante más de 100 añ os. Para evaluar la localizació n de las fuentes de semilla mapeamos la ubicació n de una especie palatable (Bromus pictus Hook.) en po...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Interspecific Competition Interacts with the Spatial Distribution of a Palatable Grass to Reduce Its Recruitment

Cipriotti¹,

Aguiar²

2005

REM

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“…Light gaps at the soil surface are recognized as important sites for plant establishment in grassland ecosystems (e.g., Aguilera andLauenroth 1993, Morgan 1998), with both root biomass and belowground competition within light gap areas substantially reduced compared to non -gap areas (Cahill and Casper 2002). Gap size may influence plant establishment (e.g., Werner 1983, Morgan 1998), with species reproducing by clonal growth (e.g., rhizomatous grasses) being highly sensitive to patch size with a preference for small openings, whereas species with the ability to have large seed banks or abundant seed dispersal (e.g., annual grasses) are not affected by patch size (Kotanen 1997).…”

Section: Resultsmentioning

confidence: 99%

Spatial patterns of light gaps in mesic grasslands

Derner¹,

Wu²

2004

REM

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The spatial pattern of light gaps in mesic grasslands in central Texas with contrasting disturbance histories was assessed using patch -based landscape metrics determined from a threshold level (25% of full sunlight), as light intensities below this threshold substantially decrease survival of honey mesquite (Prosopis glandulosa var. glandulosa Torr.) seedlings. The spatial pattern of light gaps, with the exception of edge density, were significantly different between annually-disturbed and non -disturbed grasslands on all sample dates (2 April, 30 April, 29 May, and 26 June 1998). Differences in patch metrics did not occur between nondisturbed grasslands despite contrasting vegetation composition [perennial forbs and perennial bunch (tussock) grasses]. Patchbased landscape metrics of light gaps did vary temporally in both annually-disturbed and non -disturbed grasslands. The structure and spatial configuration of light gaps were distinctly different between annually-disturbed and non -disturbed grasslands: a low density of large patches characterized light gaps in annually -disturbed grassland, whereas non -disturbed grasslands had a high density of small patches. Our findings demonstrate that the current disturbance regime is the principal environmental driver influencing species dominance and composition, and indirectly vegetation structure, which collectively contribute to the observed dynamics of light gap patches in these mesic grasslands. Incorporating spatially explicit consideration of light gap structure and dynamics into experimental studies addressing invasion of weedy plant species such as honey mesquite may be an effective approach to address mechanisms and the ecological significance of disturbance operating as a driver facilitating woody plant invasions in mesic grasslands.

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“…Among those seed mechanisms, predation is one of the major causes of species composition of eastern deciduous forests and fields (Myster 1993). On the basis of studies in similar forest/grass areas, sources of variation in the working of seed predation that warrant investigation include: (1) increased predation by litter sheltering predators (Reader 1990;Aguilera & Lauenroth 1995;Bullock et al 1995), (2) different predators having different seed preferences (Myster & Pickett 1993), (3) different seed densities leading to different predator responses (Myster & Pickett 1993), (4) different seasons of the year and different years eliciting different predator responses (Lindroth & Batzli 1984), and (5) predation levels differing among microsites (Collins & Adams 1983;Collins & Uno 1985;Knapp et al 1998).…”

Section: Introductionmentioning

confidence: 99%

The role of seed predation in the maintenance of the Cross Timbers ecotone of Oklahoma, USA

Myster

2013

Journal of Plant Interactions

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I investigated how seed predation differed among tree species and among microhabitats across the Cross Timbers and what that variation may tell us about how this ecotone is maintained. The ecotone is located in Oklahoma, USA, between the eastern deciduous forest and tallgrass prairie where seeds of eight common tree species were placed in three microhabitats (oak forest, tallgrass prairie, and sumac shrub/small-tree/grass mix). After nine days in the field, percent seeds remaining were scored for each of the 120 (8 species )3 microhabitats )5 replicates) dishes. I found for both wind-dispersed tree species, (ash, elm) there was significantly more predation in the prairie microsite, with similar small predation levels in the shrub and forest. For two of the three bird-dispersed species (dogwood, hackberry), there was significantly more predation in the prairie and shrub microsites compared to the forest. Red cedar, however, was not taken by predators very much anywhere. Finally, all three mammal-dispersed tree species (two oaks, pecan) showed significantly more predation in the shrub and forest microsites compared to the prairie. Whereas wind-and bird-dispersed species suffered less predation as microsites became more woody and dark, the dominant oaks showed the opposite trend. Consequently, seed predators are not preventing oaks from advancing across this ecotone, but yearly fluctuations in predator population density, especially in the shrub transitional zone, could be helping to maintain it.

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Seedling Establishment in Adult Neighbourhoods--Intraspecific Constraints in the Regeneration of the Bunchgrass Bouteloua Gracilis

Cited by 114 publications

References 57 publications

Interspecific Competition Interacts with the Spatial Distribution of a Palatable Grass to Reduce Its Recruitment

Interspecific Competition Interacts with the Spatial Distribution of a Palatable Grass to Reduce Its Recruitment

Spatial patterns of light gaps in mesic grasslands

The role of seed predation in the maintenance of the Cross Timbers ecotone of Oklahoma, USA

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