Nutrient Cycling and Decomposition (scientific Report)

DEAPARTMENT OF BIOLOGICAL SCIENCES

COLLEGE OF ARTS AND SCIENCES

VISAYAS STATE UNIVERSITY

Visca, Baybay City, Leyte, Philippines

NUTRIENT CYCLING AND DECOMPOSITION

(Scientific Report)

Submitted by:

Diane A. Sotero

BSEd – 2

Submitted to:

                                MS. SYBEL P. TAJ

1. INTRODUCTION

                             Nutrient cycle (or ecological recycling) is the movement and exchange of organic and inorganic matter back into the production of living matter. The process is regulated by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within ecosystems. Ecosystems are interconnected systems where matter and energy flows and is exchanged as organisms feed, digest, and migrate about. Minerals and nutrients accumulate in varied densities and uneven configurations across the planet. Ecosystems recycle locally, converting mineral nutrients into the production of biomass, and on a larger scale they participate in a global system of inputs and outputs where matter is exchanged and transported through a larger system of biogeochemical cycles. Nutrient cycle describes how nutrients move from the physical environment into living organisms, and subsequently are recycled back to the physical environment. This movement of nutrients, essential for life, from the environment into plants and animals and back again, is a vital function of the ecology of any region. In any particular environment, the nutrient cycle must be balanced and stable if the organisms that live in that environment are to flourish and be maintained in a constant population. Currently, large parts of humankind influence the nutrient cycle in such a way that we remove nutrients from the land and discharge them into aquatic environments. On the one hand, this leads to soil depletion on the land, and on the other hand, an overabundance of nutrients and pollution of water sources.

                         Decomposition of plants is nature’s way of returning to the atmosphere the carbon element that had been fixed during photosynthesis. Organic matter decomposition is the main process that recycles nutrients back into the soil. Decomposition of organic matter begins with large soil organisms like earthworms, arthropods (ants, beetles and termites), and gastropods (slugs and snails). These shredder organisms break down the organic matter into smaller pieces which re further decomposed by microorganisms like fungi and heterotrophic bacteria. Decomposition of organic matter may take several months to several years to complete. In tropical regions, the whole process is quite quick because moist conditions and high temperatures enhance the rate of biological activity.

                           The aim or the objective of this experiment is to demonstrate the return to the environment of the nutrients present in plants tissues, recognize the role of decomposition in nutrient cycling, compare the rate of decomposition of leaf litter from different species and identify biotic and abiotic factors that bring about decomposition of organic matter.

1. METHODOLOGY

  Nutrient Cycling

1.  Prepare the fresh mature leaves of the plants assigned to your group; Gmelina arborea (yemane), Canarium ovatum (pili) and Rottboellia cochichinensisi (aguingay).
2. Using scissors cut the leaves into squares of 2” x 2” sizes.
3. Weigh 150 grams of leaves from each species.
4. Prepare 9 paper bags that will contain 50 grams of leaves from each species.
5. Label each bag; (P1R1, P1R2, P1R3 ) for the paper bags containing  pili leaves,  (P2R1, P2R2, P2R3 ) for yemane  and (P3R1, P3R2, P3R3 ) for the bags containing aguingay leaves.
6. Oven-dry these paper bags at 70°C for 48 hours. Coordinate properly with the laboratory instructor and technician. Record the oven-dry weight (Table 1).
7. Compute Daily Decomposition Rate (DDR) using the formula:

% DDR = ln Wt – ln W0 / t        where Wt  = weight at a given week

                                                W0 = initial weight (g)

                                                   t = number of days

Leaf litter decomposition

1. Weigh another 50 grams of fresh leaves. Cut the leaves into squares of 2” x 2” size.
2. Put 15 grams of cut leaves inside each of 9 net bags.
3. Bring the bags to a cool and moist area. Dig 9 shallow holes measuring about 12” wide and 5” deep.
4. Make 3 rows with 3 holes in each row. The distance between holes is 0.5 m. Put the bags at random in the holes and cover with soil.
5. Use the peg as the marker. Label the 9 pegs; (P1R1, P1R2, P1R3 ) for pili, (P2R1, P2R2, P2R3 ) for yemane and (P3R1, P3R2, P3R3 ) for aguingay.
6. Allow the leaves to decompose for a period of 4 weeks.
7. At the end of each week, retrieve the bags. Take note of the presence of decomposer, when possible count (Table 2). Weigh the bag with decomposed material. Clean the weighing scale after weighing each bag. Re-bury the bags after weighing.
8. Take the following data during each retrieval and record:

1.  weight of decomposed material
2. visual observation of the texture, color and overall appearance of the decomposed material
3. close-up photos of the decomposed material

1. DATA AND RESULT

Table 1. Fresh and dry weight of (specimen) Canarium ovatum (pili) Gmelina arborea (yemane) and Rottboellia cochichinensis (aguingay)