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Forest Leaf Litter Nutrient Dynamics:
Site Traits

Researcher: Thomas E Marler

The soil characteristics of a farm or forest habitat may influence speed of decomposition in a manner that is distinct from the influence of litter traits.  For example:

Nutrient status of the soil directly influences decomposition. If leaf litter is deficient in nitrogen or other nutrients, a soil with high relative levels of nutrients may make up for the deficiency in the litter and speed up the decomposition process. 

Sites that are deficient also indirectly influence decomposition by increasing the nutrient resorption efficiency of the trees. As leaves begin to age and die, the plant can retrieve the nutrients prior to ultimate leaf death. This occurs to a greater extent in poor soils, and the result is slower decomposition of the resulting leaf litter.

A phenomenon called “home field advantage” often exerts strong control over litter decomposition traits. The concept is founded in the fact that the decomposer community that is highly efficient at decomposing litter from a particular species tends to increase in population nearby trees of that species. Therefore, if litter from that species falls in these microsites where the species-specific decomposers have increased in population, the decomposition speed is increased. 

The weather patterns of a farm or forest site also influence speed of decomposition. 

Temperature exerts a strong controlling effect on litter decomposition, with the decomposer microorganisms performing best in moderate temperatures. The temperatures in the Mariana Islands are ideal for growth and performance of these microorganisms. 

Rainfall abundance and seasonal distribution also control litter decomposition speed. As with all organisms, the community of microorganisms that decompose litter require abundant but not excessive available water to function.





















 

About 75% of the litter had decomposed by 4 months. The variation among the experimental sites was not substantial, especially in relation to the variation among the species. Litter decomposition in Tinian was slowest and litter decomposition in Saipan was most rapid. 

 

Site characteristics for Tinian farm site.

pH                                      7.20 
% Carbon      26.80
% Nitrogen        2.45
% Calcium       1.98
µg/g Phosphorus    278.00
mg/g Potassium    406.00
mg/g Magnesium   3004.00
mg/g Manganese    137.00
mg/g Iron      85.00
mg/g Copper      49.17
mg/g Nickel        3.06
mg/g Selenium        1.49
mg/g Zinc       96.61


Site characteristics for South Guam farm site.

 
pH                                      7.40 
% Carbon      13.30
% Nitrogen       1.04
% Calcium       1.38
µg/g Phosphorus      57.00
mg/g Potassium    206.00
mg/g Magnesium    405.00
mg/g Manganese    121.00
mg/g Iron      53.00
mg/g Copper      86.72
mg/g Nickel       56.25
mg/g Selenium        1.15
mg/g Zinc       49.28
 

 

Site characteristics for Rota farm site.

 

pH                                      7.10 
% Carbon      12.00
% Nitrogen       1.22
% Calcium       0.75
µg/g Phosphorus      57.00
mg/g Potassium      51.00
mg/g Magnesium    766.00
mg/g Manganese    234.00
mg/g Iron      41.00
mg/g Copper      11.74
mg/g Nickel       23.84
mg/g Selenium        0.56
mg/g Zinc       73.89
 

 

Site characteristics for North Guam farm site.

 

pH                                      7.40 
% Carbon      12.00
% Nitrogen       1.02
% Calcium       1.20
µg/g Phosphorus      54.00
mg/g Potassium      92.00
mg/g Magnesium    441.00
mg/g Manganese    143.00
mg/g Iron      16.00
mg/g Copper      23.12
mg/g Nickel      76.95
mg/g Selenium        1.72
mg/g Zinc       83.42

 

Site characteristics for Saipan farm site.

 

pH                                      7.40 
% Carbon      21.40
% Nitrogen        2.01
% Calcium       1.63
µg/g Phosphorus      28.00
mg/g Potassium      64.00
mg/g Magnesium    832.00
mg/g Manganese      37.00
mg/g Iron     121.00
mg/g Copper      46.02
mg/g Nickel        3.72 
mg/g Selenium        0.49
mg/g Zinc      39.49
 

 

Results indicate that site-to-site variation of leaf litter decomposition speed is not substantial in the southern portion of the Mariana Islands from Guam to Saipan. The variation in weather patterns is minimal, as most rainfall and cloud cover is controlled by weather patterns that are brought in from the open ocean by trade winds. The small size and  relatively limited elevation of the Mariana Islands also exert minimal orographic influence on rainfall patterns. Variation in leaf litter traits exerts much more control over nutrient and carbon turnover than does variation in site traits in the Mariana Islands.

 

 
 

 

 

 

 

 

 
 

 

 

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