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Wetland Biochemistry. Chapter 5. The cycling and transfer of nutrients is essential for wetland production. Wetlands can occur in open or closed systems. Open areas exchange materials with their surroundings. There are inflows and outflows like in the case with tidal marshes.
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Wetland Biochemistry Chapter 5
The cycling and transfer of nutrients is essential for wetland production. • Wetlands can occur in open or closed systems. • Open areas exchange materials with their surroundings. There are inflows and outflows like in the case with tidal marshes. • Closed areas, like some of the cypress swamps in the area, have stagnant water and little exchange with the areas around them. They use intrasystem cycling (the produce needed chemical reactions themselves).
Types of Wetland Soils • Wetland soils are mostly anaerobic, meaning that they do not receive oxygen due to their water saturation. They can be classified as either mineral soils or organic soils. • The word “organic” in biology and chemistry means that it contains carbon. • There are two terms used in the next slide: organic matter is decaying matter that was once living. Organic carbon are simply carbon compounds from the organic matter.
When wetland soil contains at least 20-35% organic matter, it is considered organic. Otherwise it is considered mineral soil. • For wetlands where only saturated sometimes (like a few days at a time max.) they must contain at least 20% organic carbon. • For wetlands flooded longer, the organic material depends on the amount of clay in the soil. • 60% or more of the soil clay: need 18% or more organic carbon • No clay: can have as little as 12% organic carbon to be considered an organic soil.
Besides carbon content, what make organic soils different from mineral soils? • Organic soils have more minerals available for plants to use in an organic form. Some minerals need to be tied to carbon to use. There are not more nutrients in organic soils, but they are often more available. • Organic soils are less dense and can, therefore, hold more water.
Organic soils have a higher hydraulic conductivity (permeability). It means that water can flow easier through these soils. • They have a greater cation exchange capacity. A cation is a posivite atom. Like Na+ is sodium which is positively charged. The charge matters because that is often how they are kept around and not just washed away. For example, clay is negative, so it tends to hold on to positive things.
Mineral Soils • Within mineral soils, oxidation and reductions reactions are important. To define them the most simply as I can, it is the transfer of electrons from one atom to another and they involve oxygen. • Usually, oxygen ends up with extra elections and end up as a negative ion. • Minerals, particularly metals, like calcium or magnesium, end up loosing electrons and become positive.
Mineral soils develop certain features which allow them to be identified. They are called redoximorphic features. • In order for these features to be formed, they must be anaerobic (no available oxygen), there must be organic matter available, and the temperature of the soil must be high enough. • These redoximorphic features cause color changes within the soil due most often to iron and maganese reactions.
A color reaction made from iron. Normally a red clay when not flooded.
The Nitrogen Cycle • Nitrogen is one of the most essential nutrients for plant life. Yet it is the principal limiting factor in soils; both wetland and other soils. • Nitrogen mineralization, or ammonification is the process where organic nitrogen is converted to ammonia nitrogen. • This form of nitrogen can be taken up into the roots with the assistance of microorganisms (bacteria) or turned to a gas form and lost to the atmosphere.
Nitrogen (cont.) • Nitrogen fixing bacteria convert nitrogen gas to a form more readily useable by plants. Blue-green algae can often perform this process as well.
Iron and Manganese • Iron and manganese are the most common minerals to be oxidized/reduced. • This is performed mostly by bacteria. • Ferrous iron (a reduced, or positive charged form) can coat plant roots inhibiting subsequent nutrient uptake. • This type of iron can also immobilize phosphorus
Sulfur • After Nitrogen, Iron, and Manganese, Sulfur is the next largest electron acceptor from oxygen. • Rotten egg smell
Carbon • Carbon is most common in photosynthesis reactions where carbon dioxide is used by the plant to make energy. • Aerobic respiration involves the use of energy with carbon as a by-product. • Fermentation occurs under anaerobic conditions. • When certain bacteria use carbon for their source of electrons, methane gas is produced. This is sometimes referred to as swamp gas.
