Question

What is the processing leaf litter (steps) in first-order streams?

Answer 1

Processing leaf litter is important for uptake and recycling nutrients and production of aquatic invertebrates. The forest produces a large amount of detritus, which accumulate in first order streams. This supports aquatic systems wit organic matter and nutrients. The leaf litters are thus subjected to physical abrasions, shredding and fragmentation by invertebrates, fungi, feeding, microbial degradations. The steps to facilitate the processing of leaf litters in these first order streams are:

1. Sampling of water:

• Water samples are collected at different time (or season). The samples are analysed for pH, total Nitrogen (TN), DOC, dissolved ions, phosphorous, nitrates, ammonium.
• Water temperature was continuously monitored. Pendant temperature/light loggers were attached on each side of the streams.
• Depth, height, width, of the streams should be measured at certain points (3 to 5) and averaged.

2. Study designing to measure decomposition:

• Samples of leaves are collected form various types of trees, in vicinity or littering the first order stream.
• Principal content analysis (PCA) is conducted
• The leaves are air dried and each type of samples are further separated for observation of processing by, invertebrates or microbial decomposition.
• Size of the bags were varied to exclude microbial decomposition from invertebrate processing. 15x15 cm fine mesh (0.5mm) bags could be used to observe microbial decomposition. 12x 17 cm coarse mesh (5mm) bags for invertebrates processing.
• At different sites of the stream, replicates of these bags, with each type of leaf samples in fine mesh or coarse mesh bags, are introduced. Some leaves require more time for decomposition, accordingly the bags are removed for analysis. Like, for conifers-around 85-95 days, for deciduous- around 55-60 days.

3. Calculation for mass loss and decomposition rates:

• The decomposed samples obtained from the study, are collected. Some of the samples are analysed for calculations.
• Mass loss = AFDM_INITIAL – AFDM_FINAL. (AFDM= ash free dry mass)
• Decomposition rate= ln(Mt/M0)/t (M_t = mass after time t, M₀= initial mass).

4. Litter input, characterization and isolation of decomposers: invertebrates, fungal bio mass, other organisms.

5. Fter detrmining the base line conditions, weather and climate, the streams are accordingly augmented ad leaf litters are processed.