20170405-Raub-Thesis.pdf (7.37 MB)
The Ecology of Malaysian Peat Swamps with Microbial Implications
thesis
posted on 2017-04-09, 22:50 authored by Sonja Christine RaubTropical peat swamp
forests (TPSF) in Malaysia are infertile, ombrotrophic, acidic, and waterlogged
forests of mixed tree composition. Knowledge about microbes in peat is still
lacking, therefore ecological studies investigating microbial activity on leaf
litter, in peat, and in tree roots in the North Selangor Peat Forest (NSPF) of
Peninsular Malaysia were undertaken. Changes in peatland landuse were addressed
including logging, drainage, fire, and conversion to agriculture. Microbial
diversity and activity in a natural TPSF - Loagan Bunut in Sarawak, were
determined. Questions asked included: Which factors most influence microbes as
heterotrophs in tropical peat swamps - the environment, or the qualities of
peat and leaf litter? What are the roles of tree roots and microbes during
litter decomposition? Which anthropogenic manipulations most affect
heterotrophic activities in peatlands, and what are the consequences? Finally,
what is the microbial diversity and activity in peat of a natural TPSF? Does
microbial diversity change with peat depth?
Methods employed for these studies focused on leaf litter decay in the field complemented by peat core samples and the quantification of environmental factors, such as the watertable and its pH. In the lab, chemical and physical measurements of peat and leaves were complemented with microbial enzyme activity determinations, used as a proxy for microbial activity. DNA extractions of peat produced the metagenomes for microbial diversity using next generation sequencing.
Leaf quality of 4 species local to NSPF (Macaranga tanarius, M. pruinosa, Shorea uliginosa, and Koompassia malaccensis) was investigated to elicit their contributions to peat, and to show how life strategies of trees influence nutrient cycling in peatlands. Leaves in litterbags were decomposed for 2 yrs. in NSPF to determine their contributions to nutrient cycling, and to carbon seqestration in peat. Anthropogenic effects on peatland microbial ecology focusing on heterotrophic activity were contrasted by comparing 2 forested and 2 deforested sites in which M. tanarius and S. uliginosa leaf litter was decomposed for 6 mo. to show that deforestation enhances leaf decomposition that increases nutrient cycling through infertile peatlands. Two metagenomes created from peat revealed that bacteria dominated microbial diversity in surface and 100cm deep peat. Microbial activity occurred in surface, 10 cm, and 45 cm deep peat. In 100 cm deep peat microbes were present, but dormant, due to high energetic requirements in deeper peat, and a buildup of tannic acids.
The ecological importance for maintaining waterlogged low pH conditions in peatlands that house late successional tree communities to promote slowed nutrient cycling in infertile peat that allows for the accretion of carbon was demonstrated. Natural TPSF support diverse microbial communities that change when humans disrupt them, which threatens their existence.
Methods employed for these studies focused on leaf litter decay in the field complemented by peat core samples and the quantification of environmental factors, such as the watertable and its pH. In the lab, chemical and physical measurements of peat and leaves were complemented with microbial enzyme activity determinations, used as a proxy for microbial activity. DNA extractions of peat produced the metagenomes for microbial diversity using next generation sequencing.
Leaf quality of 4 species local to NSPF (Macaranga tanarius, M. pruinosa, Shorea uliginosa, and Koompassia malaccensis) was investigated to elicit their contributions to peat, and to show how life strategies of trees influence nutrient cycling in peatlands. Leaves in litterbags were decomposed for 2 yrs. in NSPF to determine their contributions to nutrient cycling, and to carbon seqestration in peat. Anthropogenic effects on peatland microbial ecology focusing on heterotrophic activity were contrasted by comparing 2 forested and 2 deforested sites in which M. tanarius and S. uliginosa leaf litter was decomposed for 6 mo. to show that deforestation enhances leaf decomposition that increases nutrient cycling through infertile peatlands. Two metagenomes created from peat revealed that bacteria dominated microbial diversity in surface and 100cm deep peat. Microbial activity occurred in surface, 10 cm, and 45 cm deep peat. In 100 cm deep peat microbes were present, but dormant, due to high energetic requirements in deeper peat, and a buildup of tannic acids.
The ecological importance for maintaining waterlogged low pH conditions in peatlands that house late successional tree communities to promote slowed nutrient cycling in infertile peat that allows for the accretion of carbon was demonstrated. Natural TPSF support diverse microbial communities that change when humans disrupt them, which threatens their existence.
