Assessing the significance of soil erosion to arable weed seedbank composition and biotic function 1,2
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Ashley Gorman , Cathy Hawes , Blair M. McKenzie , John S. Rowan 1
Centre for Environmental Change and Human Resilience, University of Dundee, Nethergate, Dundee DD14HN, Scotland UK The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland UK Email: ashley.gorman@hutton.ac.uk 2
Overview Seeds are the principle means by which plants disperse across the landscape, relying upon regeneration and persistence, with their fate playing a central role in the assemblage, functioning and dynamics of plant communities. Variation in composition and density of the weed seedbank is closely linked to cropping history of the land and tillage practices. Current farm management places an ever-increasing pressure upon weed seedbank diversity, with intensification thought to be responsible for recent declines in biodiversity and associated ecosystem services through a reduction in the provision of food, shelter and adequate reproduction sites for higher trophic groups. Thus, sustainability and resilience within the agroecosystem is challenged during a time when climate change is predicted to increase the frequency of erosional storm events. The relationship between soil processes and weed seedbank dynamics and composition from field to catchment scale may therefore be critical for improving sustainability whilst maintaining profitable crop yield. Recent studies have shown a stronger link between seed movement and sediment than with overland water movement (Lewis et al., 2013). However, relatively little is understood about the significance of soil erosion impacting upon seedbank composition via selectively altering species specific recruitment, dispersal, germination and seedling survival rates. Determining this significance therefore requires the investigation of 'tolerable soil loss' and the biophysical linkages between seedbank composition, soil properties, land management histories and landscape complexity.
Conducting Emergence Assessments for Seedbank Diversity
EPIZOOCHORY
FECUNDITY
EROSION
SECONDARY DISPERSAL
SEED TRAITS
ENDOZOOCHORY
SECONDARY DISPERSAL
PRIMARY DISPERSAL
SIZE
BIOTIC
ABIOTIC
ANTHROPOCHORY
SHAPE
PARENT SURVIVAL
APPENDAGES
ANEMOCHORY
SURFACE SEED
MUCILAGE SECRETION
Machinery, Tyres, Clothing etc. HYDROCHORY
EMERGENCE
FATAL GERMINATION
BURIAL
ACTIVE SEEDBANK SUN
WATER AGRO MANAGEMENT Disturbance, Application of Herbicides, Tillage
PREDATION
OTHER PHYSICAL DAMAGE
MORTALITY
DISEASE
Acknowledgements This PhD studentship is funded by CECHR (UoD) and The James Hutton Institute. References
Bochet, E. (2015) ‘The fate of seeds in the soil: a review of the influence of overland flow on seed removal and its consequences for the vegetation of arid and semiarid patchy ecosystems’ SOIL, 1:131-146 Lewis et al. (2013) ‘Assessing the significance of soil erosion for arable weed seedbank diversity in agro-ecosystems’ Progress in Physical Geography, 37:622-641
TEMPERATURE
SECONDARY DORMANCY
GERMINATION
DEPOSITION
Quantifying Seed Fate
DEPTH
PHYSIOLOGICAL CHARACTERS
GAS
DORMANT SEEDBANK
Many of these processes are known and understood for other systems (Bochet, 2015) but erosive redistribution is still unclear in an arable context. The seedbank is regenerated through primary dispersal via the parent plant, as well as secondary dispersal. Dormancy allows for the seedbank to persist for long periods of time until germination is stimulated under a range of factors. Quantified losses to the seedbank have been demonstrated through mortality, germination, and some stages of secondary dispersal. The target of recreating a seed fate budget is to focus upon the unknown areas surrounding erosional and depositional implications to seed flow and the alterations to functionality within the agroecosystem.
Seed Input Process
Influences on Seed Input
Seed Loss Process
Influences on Seed Loss
Seed Flow Management (Site Specific) Key Questions
Objectives The aim of this project is to: Quantify the significance of sediment-associated redistribution of arable weed seeds in relation to seedbank diversity and function within agroecosystems. Undertake quantitative analysis of seed inputs (seed rain, deposition) and loss (germination, mortality, dispersal) to create a seed fate budget to quantify thresholds of seedbank abundance and export rates. Understanding seed fate conclusively will not only inform biodiversity policy but also better equip effective predictive modelling and weed management strategies.