Abstract
This paper investigates the tidal effects on aeration conditions for plant root respiration in a tidal marsh. We extend the work of Ursino et al. (2004) by using a two‐phase model for air and water flows in the marsh. Simulations have been conducted to examine directly the link between the airflow dynamics and the aeration condition in the marsh soil. The results show that the effects of entrapped air on water movement in the vadose zone are significant in certain circumstances. Single‐phase models based on Richards' equation, which neglect such effects, may not be adequate for quantifying the aeration condition in tidal marsh. The optimal aeration condition, represented by the maximum of the integral magnitude of tidally advected air mass (TAAM) flux, is found to occur near the tidal creek for the four soil textures simulated. This may explain the observation that some salt marsh plant species grow better near tidal creeks than in the inner marsh areas. Our analyses, based on the two‐phase model and predicted TAAM flux magnitude, provide further insight into the “positive feedback” mechanism proposed by Ursino et al. (2004). That is, pioneer plants may grow successfully near the creek where the root aeration condition is optimal. The roots of the pioneer plants can soften and loosen the rhizosphere soil, which increases the evapotranspiration rate, the soil porosity, and absolute permeability and weakens the capillary effects. These, in turn, improve further the root aeration conditions and may lead to colonization by plants less resistant to anaerobic conditions.
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Claims 5
Claim · model-written summary
Entrapped air significantly affected vadose-zone water movement in the model.
Not reportedTaxonDirection
Verbatim
e0“the effects of entrapped air on water movement in the vadose zone are significant in certain circumstances”
Claim · model-written summary
Modeled optimal aeration occurred near the tidal creek for four simulated soil textures.
Verbatim
e0“The optimal aeration condition, represented by the maximum of the integral magnitude of tidally advected air mass (TAAM) flux, is found to occur near the tidal creek for the four soil textures simulated”
t0“plant”
e1“pioneer plants may grow successfully near the creek where the root aeration condition is optimal”
Claim · model-written summary
The model suggests pioneer plants may grow successfully near creeks where root aeration is optimal.
Verbatim
e0“pioneer plants may grow successfully near the creek where the root aeration condition is optimal”
Claim · model-written summary
Pioneer plant roots can loosen rhizosphere soil, increasing evapotranspiration, porosity and permeability while weakening capillary effects.
Verbatim
e0“The roots of the pioneer plants can soften and loosen the rhizosphere soil, which increases the evapotranspiration rate, the soil porosity, and absolute permeability and weakens the capillary effects”
Claim · model-written summary
The modeled soil changes further improve root aeration and may allow less anaerobic-tolerant plants to colonize.
- Taxon
- plantsViridiplantaee0
- Outcome
- root aeration conditionse0
- Qualifier
- colonization by plants less resistant to anaerobic conditionse0
Verbatim
e0“These, in turn, improve further the root aeration conditions and may lead to colonization by plants less resistant to anaerobic conditions”