Keywords: Aggregates; Arable Weeds; Biodiversity; Dispersal; Ecosystem Services; Interactions; Myxospermy; Seedbank; Soil Erosion; Sustainable Agriculture
The role of seedbank composition and biotic function in vulnerable erosive agroecosystems 1,2
2
1
Centre for Environmental Change and Human Resilience, University of Dundee, Nethergate, Dundee DD1 4HN, Scotland UK 2 The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland UK 3 School of Social Sciences, University of Dundee, Nethergate, Dundee DD1 4HN, Scotland UK Email: ashley.gorman@hutton.ac.uk
Myxospermous Species
Arable weeds provide important ecosystem services within simplified agroecosystems and may act as a buffer against short-term disturbance events. Differential mobility capacity depends on seed morphology causing selective transport of seeds. Myxospermous weed species have ecological significance for germination, dispersal and dormancy.
Acknowledgements Pete Iannetta, Linda Ford, Sandra Caul.
Myxospermy: Mucilage Secretion
Accelerated soil erosion degrades the physical and biogeochemical functioning of arable soils.
Arabidopsis thaliana
Capsella bursa-pastoris
Plantago major
Senecio vulgaris
Urtica urens
Veronica arvensis
Viola arvensis
Mouse-ear Cress
Shepard’s Purse
Broadleaf Plantain
Common Groundsel
Annual Nettle
Corn Speedwell
Field Pansy
The adhesive nature of mucilage may cause physical alterations to soil, stabilising structure and enhancing water retention.
This trait is common among many arid species and those adapted to continually disturbed environments such as agroecosystems. The adherent layer is comprised of cellulose fibres embedded in a pectinaceous matrix. The non-adherent layer is largely pectin which is readily dispersed in water, thus capable of influencing biogeochemistry and soil structure. When mucilage dries, it facilitates the prevention of seed transport by anchoring the seed to soil particles.
Mucilage Release
Quantitative studies are rare and limited to a single or few model species.
0.3 mm
0.3 mm
0.5 mm
1 mm
0.5 mm
0.4 mm
Upon hydration of mature seed, mucilage ruptures primary cell wall forming a two layered capsule and ray-like structure.
0.5 mm
Mucilage % Weight of Total Dry Seed Weight
Aims
3
Ashley Gorman , Cathy Hawes , Blair M. McKenzie , John S. Rowan
Background
2
40%
Investigate the extent to which specific weed community assemblages are capable of preventing both their removal and soil particle transport during runoff erosion events. Quantify the adhesive power of myxospermous seeds to retain soil structure in erosive environments.
35% 30% 25%
A volcano-shaped cytoplasmic column forms which is gradually displaced by the columella (secondary cell wall).
20% 15% 10% 5% 0%
Adherent
Non-Adherent
Experimental Design: Seed-Soil Interactions Range of Mucilage Influence
Adhered Particle Size Distribution
Soil Particle
Mucilage (M), Ray (R)
Adherent mucilage can be extracted by enzyme digestion; non-adherent mucilage can be extracted by dispersion in water.
Extracted Non-Adherent Mucilage
Going Forward
Seed + Adherent Mucilage
Testing the Response of Soil Properties
Seed Only Mucilage
Aggregate Scale
Seed + Both Layers
Mechanism
Runoff Erosion Assays with Rainfall Simulation
Patch Scale
Explore the underlying mechanisms occurring and how, and to what extent, they affect soil behaviour. Use this knowledge to infer processes occurring at the field scale to predict soil export fluxes under varying climate regimes. Highlight catchment and landscape scale soil security as well as biodiversity implications for the wider ecosystem. A better understanding of the biophysical linkages between seedbank composition, soil properties and land management will contribute to policy drivers of sustainability and food security.