Abstract
Pineapples (Ananas comosus (L.) Merr.) cultivation on drained peats could affect the release of carbon dioxide (CO2) into the atmosphere and also the leaching of dissolved organic carbon (DOC). Carbon dioxide emission needs to be partitioned before deciding on whether cultivated peat is net sink or net source of carbon. Partitioning of CO2 emission into root respiration, microbial respiration, and oxidative peat decomposition was achieved using a lysimeter experiment with three treatments: peat soil cultivated with pineapple, bare peat soil, and bare peat soil fumigated with chloroform. Drainage water leached from cultivated peat and bare peat soil was also analyzed for DOC. On a yearly basis, CO2 emissions were higher under bare peat (218.8 t CO2 ha/yr) than under bare peat treated with chloroform (205 t CO2 ha/yr), and they were the lowest (179.6 t CO2 ha/yr) under cultivated peat. Decreasing CO2 emissions under pineapple were attributed to the positive effects of photosynthesis and soil autotrophic activities. An average 235.7 mg/L loss of DOC under bare peat suggests rapid decline of peat organic carbon through heterotrophic respiration and peat decomposition. Soil CO2 emission depended on moderate temperature fluctuations, but it was not affected by soil moisture.
Highlights
Tropical peat soils are generally defined as soils formed by the accumulation of partially decayed woody plant materials under waterlogged condition
It was hypothesized that microbial respiration and peat decomposition will cause higher loss of CO2 and dissolved organic carbon (DOC) from the bare peat soil than from the peat soil cultivated with pineapple
The CO2 emission was estimated at about 218.8 t CO2 ha/yr under bare peat soil (B), followed by 205 t CO2 ha/yr under bare peat soil treated with chloroform (C), and 179.6 t CO2 ha/yr under peat soil cultivated with pineapple (A)
Summary
Tropical peat soils are generally defined as soils formed by the accumulation of partially decayed woody plant materials under waterlogged condition. Peats of the tropics are increasingly being cultivated. They store large amount of organic carbon, peat soils drained for agriculture in particular accelerate their decomposition rates. Carbon dioxide may be emitted from peatland through burning by wildfires, microbial respiration, root respiration, and physical oxidation [5, 6]. Carbon dioxide emissions are related to water table depth [7], soil temperature [8, 9], fertilization [10], land use type [11], and peat type [12]. Carbon in the form of DOC is lost through leaching due to microbial metabolism [13]. Carbon losses through emission and leaching may shift the peatland carbon balance from sink to source [14]
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