Integrating measurements of seed availability and removal to estimate weed seed losses due to predation

Westerman, Paula R.; Liebman, Matt; Heggenstaller, Andrew H.; Forcella, Frank

doi:10.1614/ws-05-067r.1

Cited by 68 publications

(64 citation statements)

References 30 publications

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“…More research is needed to clarify mechanisms that may lead to enhanced seed decay in organic systems. Surface weed seed removal by insect and small mammal predators from the soil surface is thought to substantially reduce weed seed banks, but predation rates can vary with tillage systems [77]. For example, Menalled et al [78] observed that activity density of granivorous carabids and removal of fall panicum (Panicum dichotomiflorum Michx.)…”

Section: Organic Zero Tillage Effects On Weedsmentioning

confidence: 99%

Impacts of Organic Zero Tillage Systems on Crops, Weeds, and Soil Quality

2013

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Abstract:Organic farming has been identified as promoting soil quality even though tillage is used for weed suppression. Adopting zero tillage and other conservation tillage practices can enhance soil quality in cropping systems where synthetic agri-chemicals are relied on for crop nutrition and weed control. Attempts have been made to eliminate tillage completely when growing several field crops organically. Vegetative mulch produced by killed cover crops in organic zero tillage systems can suppress annual weeds, but large amounts are needed for adequate early season weed control. Established perennial weeds are not controlled by cover crop mulch. Integrated weed management strategies that include other cultural as well as biological and mechanical controls have potential and need to be incorporated into organic zero tillage research efforts. Market crop performance in organic zero tillage systems has been mixed because of weed, nutrient cycling, and other problems that still must be solved. Soil quality benefits have been demonstrated in comparisons between organic conservation tillage and inversion tillage systems, but studies that include zero tillage treatments are lacking. Research is needed which identifies agronomic strategies for optimum market crop performance, acceptable levels of weed suppression, and soil quality benefits following adoption of organic zero tillage. OPEN ACCESSSustainability 2013, 5 3173

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Section: Organic Zero Tillage Effects On Weedsmentioning

confidence: 99%

Impacts of Organic Zero Tillage Systems on Crops, Weeds, and Soil Quality

2013

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“…The consumption of fruits by birds may not necessarily result in successful dispersal (MandonDalger et al 2004;Westerman et al 2006;Combs et al 2011). This is because some frugivorous birds are seed predators (Jordano 1983).…”

Section: Introductionmentioning

confidence: 99%

Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

et al. 2015

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Avian frugivores play a key role in seed dispersal of many plant species, including invasive alien plants. We assessed the effect of gut passage on the germination of selected invasive alien plant species in South Africa. Fruits of four fleshly-fruited invasive alien plant species: Solanum mauritianum, Cinnamomum camphora, Psidium guajava, and Morus alba, were fed to two species of indigenous turacos, Knysna (Tauraco corythaix) and purple-crested (Gallirex porphyreolophus) turacos, and to invasive roseringed parakeets (Psittacula krameri). Seed retention time was determined as this can influence both seed dispersal and germination success. Germination success of ingested seeds was compared with that of manually de-pulped seeds, as well as to seeds in whole fruit. The germination success of seeds of all the invasive plant species increased significantly after ingestion by both turaco species compared with seeds from whole fruits. Germination success of manually de-pulped seeds did not differ significantly from that of turaco ingested seeds. In contrast, seed passage through the digestive tract of rose-ringed parakeets significantly reduced germination success and viability of ingested invasive plant species. Our results suggest that Knysna and purple-crested turacos are legitimate seed dispersers of fleshy-fruited invasive plants, while rose-ringed parakeets are mainly seed predators. Although seed predation by rose-ringed parakeets negatively affects the reproductive success of these plants, it is unlikely that this will suppress the spread of these invasive alien plants in South Africa as they are already well established. Furthermore, they can facilitate dispersal by seed regurgitation and dropping uneaten fruits away from the parent plant. Similar trends could be expected for indigenous seeds that rose-ringed parakeets feed on and therefore these birds remain a negative influence within invaded ecosystems.

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“…Past research has, nonetheless, shown that the relative abundance and impact of seed predator guilds vary among habitats (Hulme 1998;Menalled et al 2000), and they can be affected by the type of crop management used (Carmona and Landis 1999;Gallandt et al 2005). Point estimates of seed predation do not accurately estimate the cumulative numbers of weed seed removed by predators because seed predation is affected by several temporally variable factors not easily assessed, including seed demand by predators, microsite predator density, the timing of seed dispersal, and seed residence time on the soil surface (Westerman et al 2006).…”

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Postdispersal Weed Seed Predation Is Affected by Experimental Substrate

et al. 2008

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A standard method for evaluating weed seed predation is needed to facilitate generalizations across studies. Identification of general trends could allow practical recommendations for enhancing weed seed predation in agricultural systems. The objective of this study was to compare the commonly used sandpaper and soil substrate methods for offering weed seeds when assessing seed predation rates. Invertebrate seed predators and associated weed seed predation levels were measured in June to July, August, and September of 2005 and 2006 within a conventionally managed corn system. Seed predation levels of three common weed species, velvetleaf, giant foxtail, and common lambsquarters, were estimated using feeding trials in which 40 seeds of each species were offered over a 48 h period using the two substrates. Exclosures were used to distinguish total predation from predation by invertebrates alone. In addition, we investigated the use of geospatial analysis to estimate spatial autocorrelation of invertebrate populations and seed removal rates. Results suggest caution in using synthetic substrates, such as sandpaper, when assessing seed predation, especially when investigating small-seeded species (< 1 mg seed−1) or when seed predators are predominantly invertebrates. By contrast, predation of the larger-seeded species, velvetleaf, was less affected by substrate, perhaps because of removal predominately by vertebrates. One way to overcome problems with the sandpaper substrate method is for studies to include some soil substrate samples for on-site calibration of the sandpaper substrate. If necessary, data could then be corrected by multiplying by the ratio of soil substrate measured-predation rate to sandpaper measured-predation rate. Spatial autocorrelation explained between 6 and 9% of the variation in giant foxtail and common lambsquarters removal rates attributed to invertebrates alone. Researchers should, therefore, be careful not to neglect the impact of clustered invertebrate populations and associated seed removal rates.

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Integrating measurements of seed availability and removal to estimate weed seed losses due to predation

Cited by 68 publications

References 30 publications

Impacts of Organic Zero Tillage Systems on Crops, Weeds, and Soil Quality

Impacts of Organic Zero Tillage Systems on Crops, Weeds, and Soil Quality

Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

Postdispersal Weed Seed Predation Is Affected by Experimental Substrate

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