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Forest Leaf Litter Nutrient Dynamics

Funded by: USDA NRCS    Researcher: Thomas Marler
 

When residues of plants are added to the forest floor litter pool, their constituents are released over time through decomposition. Decomposition of plant litter is a fundamental source of nutrients and energy for forested ecosystems. Numerous factors influence decomposition including the environment, the initial quality of the litter as defined by its physical traits and chemical constituents, and the decomposer community of microorganisms and soil animals. The influential environmental factors include the chemical traits of the soil and climatic factors like temperature and rainfall. The litter quality factors are defined by various characteristics such as plant species, plant organ, and age of the organ when it was released from the plant.

Chemistry of plant residues has been extensively studied in relation to decomposition. A high relative proportion of nutrients such as calcium, manganese, nitrogen, phosphorus, and potassium enable speedy decomposition by the decomposer community. In some cases, their relative proportion in relation to residue carbon is a better predictor of decomposition speed than their absolute amounts. Some of the larger plant compounds such as lignin are difficult to break down, so higher contents of these compounds can delay the decomposition process. Other plant compounds such as phenolics directly inhibit microbial colonization or function, and their presence also slows down decomposition.

In addition to the direct effect that a plant species exerts on litter decomposition through chemistry of its residues that are added to the litter layer, the chronic additions of litter from a tree also influence future decomposition indirectly through the changes in the soil over time. This is sometimes called the “footprint” that a tree imposes on the soil. These influences on soil properties are one way that invasive tree species bring about substantial changes in ecosystem properties. 

Understanding litter decomposition dynamics greatly contributes to understanding how terrestrial ecosystems function and factors that control storage of soil carbon. Although the literature on litter decomposition is robust, there is a conspicuous bias toward temperate ecosystems.

 

In this study: