s2ary
09-16-2007, 06:40 AM
Inconsistencies with Salt Marsh Plant Biology
All plants need oxygen in their roots to survive. Many wetland plants have developed specific adaptations to bring oxygen from the air down into their roots. One such adaptation is called an Aerenchyma (ai-reng-kuh-muh) System. An aerenchyma system is a collection of hollow thin walled cells that circulate air down into the roots of non woody wetland plants. Species like cattails, sedges, and rushes that grow in saturated soils are called emergent wetland species because their roots are under shallow water or saturated soils and the plant emerges out of the water. All emergent species have highly developed aerenchyma systems. The dominate New England salt marsh species all have aerenchyma systems as well but they are poorly developed. This evolutionary trait leads to the fact that these salt mash species did not develop in soils that are continually saturated. Southern marshes that have narrow tidal prisms have salt marsh dominant species with highly developed aerenchyma systems. These species are absent in our northern marshes because saturated conditions did not prevail. As a result the southern species with developed aerenchyma systems did not evolve as a cold hardy species.
If New England Salt Marshes did not develop under saturated growing conditions than how is restricting tidal flow, raising the ground water to the marsh surface, and inundating marsh soils restoring these areas to their unimpaired condition?
Inconsistencies with Peat Formation
In New England, salt marsh peat is a dense layer of organic matter and sediments that have accumulated for more than 4,000 years. Because the peat is held together with interwoven fibrous plant roots and grass stems any cuts or interruptions in the formation process is very recognizable. When a trench or excavation pit is dug in the peat there is nothing that can fuse the deeper marsh back together. The same is true when a panne or pond is filled in. Nothing can be done to knit the peat back together.
In addition, because peat is held together by plant roots, areas that form in the absence of plants are unconsolidated fine materials. This is consistent with the bottom content in any and all naturally forming pannes and pools. It is not uncommon to sink past your knee if you unknowingly step into a natural panne on the marsh. When a ditch breaches a panne or pool the unconsolidated materials collapse into the ditch. There is no structure to the material, and the result is a widely sloped swale.
So if pannes and pools were the dominating salt marsh feature in a New England salt marsh, why do 70 - 150 year old ditches still have vertical sides? If these ditches breached panne and pool areas the unconsolidated materials would have collapsed into the ditch. Because of WPA ditching efforts in the 1930’s in many areas of New England ditch densities are as close as 30 feet apart. If pannes and pools were a dominant marsh feature wouldn’t at least some of them show evidence of breaching a pool? The fact is very few do. The original purposes for ditching marshes for mosquito control was to get the flood water off the marsh so the mosquitoes could not breed. There is very little evidence that supports pannes or pools being dominant marsh features.
Increases in Sulfur Toxicity
Sulfur is responsible for the familiar ‘rotten egg’ or ‘burnt match’ smell associated with a New England salt marsh. Sulfur is a naturally occurring substance in sea water in the form of Sulfate. When sulfate contacts saturated salt marsh soils that are low in oxygen sulfur eating bacteria convert the sulfate into Sulfite. Sulfite then becomes mobile in the saturated soils and travels to oxygenated soils where it oxidizes converting into sulfuric acid which inhibits plant growth. Sulfuric acid then reacts with iron in the soil. The reaction of iron and sulfuric acid removes an ion from sulfuric acid converting the acid compound into a salt compound called Hydrogen-sulfate which is extremely toxic to plants.
In New England salt marshes small portions of the marsh have high ground water elevations that are within the active root zone of the existing plants. Throughout the majority of New England salt marshes the groundwater elevations are deeper than 10cm from the surface of the marsh resulting in the sulfur cycle occurring mostly below the active root zone of the existing salt marsh plants. OWMM, OMWM, and IMM techniques raise the ground water elevation, or saturated soils that are low in oxygen, up into the active rooting zone of the existing salt marsh plants. This brings the toxic sulfur cycle up into the active root zone of the existing plants. Over time the sulfur cycle described above reduces the vigor and productivity of the existing plants. As these effects continue plant mortality increases and new mosquito breeding habitats that are inaccessible to fish begin to form. In addition these effects impact the near shore waters by decreasing salt marsh primary production and reducing the volume of nutrients available to the coastal species.
All plants need oxygen in their roots to survive. Many wetland plants have developed specific adaptations to bring oxygen from the air down into their roots. One such adaptation is called an Aerenchyma (ai-reng-kuh-muh) System. An aerenchyma system is a collection of hollow thin walled cells that circulate air down into the roots of non woody wetland plants. Species like cattails, sedges, and rushes that grow in saturated soils are called emergent wetland species because their roots are under shallow water or saturated soils and the plant emerges out of the water. All emergent species have highly developed aerenchyma systems. The dominate New England salt marsh species all have aerenchyma systems as well but they are poorly developed. This evolutionary trait leads to the fact that these salt mash species did not develop in soils that are continually saturated. Southern marshes that have narrow tidal prisms have salt marsh dominant species with highly developed aerenchyma systems. These species are absent in our northern marshes because saturated conditions did not prevail. As a result the southern species with developed aerenchyma systems did not evolve as a cold hardy species.
If New England Salt Marshes did not develop under saturated growing conditions than how is restricting tidal flow, raising the ground water to the marsh surface, and inundating marsh soils restoring these areas to their unimpaired condition?
Inconsistencies with Peat Formation
In New England, salt marsh peat is a dense layer of organic matter and sediments that have accumulated for more than 4,000 years. Because the peat is held together with interwoven fibrous plant roots and grass stems any cuts or interruptions in the formation process is very recognizable. When a trench or excavation pit is dug in the peat there is nothing that can fuse the deeper marsh back together. The same is true when a panne or pond is filled in. Nothing can be done to knit the peat back together.
In addition, because peat is held together by plant roots, areas that form in the absence of plants are unconsolidated fine materials. This is consistent with the bottom content in any and all naturally forming pannes and pools. It is not uncommon to sink past your knee if you unknowingly step into a natural panne on the marsh. When a ditch breaches a panne or pool the unconsolidated materials collapse into the ditch. There is no structure to the material, and the result is a widely sloped swale.
So if pannes and pools were the dominating salt marsh feature in a New England salt marsh, why do 70 - 150 year old ditches still have vertical sides? If these ditches breached panne and pool areas the unconsolidated materials would have collapsed into the ditch. Because of WPA ditching efforts in the 1930’s in many areas of New England ditch densities are as close as 30 feet apart. If pannes and pools were a dominant marsh feature wouldn’t at least some of them show evidence of breaching a pool? The fact is very few do. The original purposes for ditching marshes for mosquito control was to get the flood water off the marsh so the mosquitoes could not breed. There is very little evidence that supports pannes or pools being dominant marsh features.
Increases in Sulfur Toxicity
Sulfur is responsible for the familiar ‘rotten egg’ or ‘burnt match’ smell associated with a New England salt marsh. Sulfur is a naturally occurring substance in sea water in the form of Sulfate. When sulfate contacts saturated salt marsh soils that are low in oxygen sulfur eating bacteria convert the sulfate into Sulfite. Sulfite then becomes mobile in the saturated soils and travels to oxygenated soils where it oxidizes converting into sulfuric acid which inhibits plant growth. Sulfuric acid then reacts with iron in the soil. The reaction of iron and sulfuric acid removes an ion from sulfuric acid converting the acid compound into a salt compound called Hydrogen-sulfate which is extremely toxic to plants.
In New England salt marshes small portions of the marsh have high ground water elevations that are within the active root zone of the existing plants. Throughout the majority of New England salt marshes the groundwater elevations are deeper than 10cm from the surface of the marsh resulting in the sulfur cycle occurring mostly below the active root zone of the existing salt marsh plants. OWMM, OMWM, and IMM techniques raise the ground water elevation, or saturated soils that are low in oxygen, up into the active rooting zone of the existing salt marsh plants. This brings the toxic sulfur cycle up into the active root zone of the existing plants. Over time the sulfur cycle described above reduces the vigor and productivity of the existing plants. As these effects continue plant mortality increases and new mosquito breeding habitats that are inaccessible to fish begin to form. In addition these effects impact the near shore waters by decreasing salt marsh primary production and reducing the volume of nutrients available to the coastal species.