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Fungal and bacterial interaction during the colonization of litter in soil

Isacsson Nilsson, Elvira (2016) BIOM01 20161
Degree Projects in Biology
Popular Abstract
What decides how plant litter is decomposed, and by whom?

Trees take up carbon in form of atmospheric CO2 from the air and use as building material as they grow. This carbon, locked in plant material, enters the soil carbon cycle via aboveground litter for example in the form of fallen foliage, dead trees, lost bark or via the plants root system as root litter or root exudates. Fungi and bacteria are the two main decomposer groups of plant litter in soil. The dominance of fungi or bacteria has a great influence on decomposition as fungi and bacteria contribute differently to decomposition. Previous research shows that fungi grow better in acid soil and on litter that is difficult to decompose and nutrient poor litter. Bacteria grow... (More)
What decides how plant litter is decomposed, and by whom?

Trees take up carbon in form of atmospheric CO2 from the air and use as building material as they grow. This carbon, locked in plant material, enters the soil carbon cycle via aboveground litter for example in the form of fallen foliage, dead trees, lost bark or via the plants root system as root litter or root exudates. Fungi and bacteria are the two main decomposer groups of plant litter in soil. The dominance of fungi or bacteria has a great influence on decomposition as fungi and bacteria contribute differently to decomposition. Previous research shows that fungi grow better in acid soil and on litter that is difficult to decompose and nutrient poor litter. Bacteria grow better in alkaline soil and on nutrient rich litter where the carbon instead is easily available.
We tested a range of litters suitable for fungal and bacterial colonization. We used soil of different pH values, acid soil being dominated by fungi and alkaline soil dominated by bacteria, and we also experimentally inhibited fungi or bacteria using antibiotics. These treatments were used to estimate the relative contribution by fungi and bacteria to decomposition during the colonization of litter. To do this we measured fungal and bacterial growth. Fungal growth was measures using a method to estimate the rate of fat synthesis. Bacterial growth was measured by estimating the rate of protein production. In addition to this, respiration was measured in order to get information of the total litter decomposition rate.
First, we investigated the fungal and bacterial colonization of eight different litters to identified four litters differing in how fungi and bacteria colonized them. Secondly, we tested the concentration of the two different antibiotics needed to inhibit fungi or bacteria for the longest time without affecting the other decomposer organism. Then we were able to start our main study, investigating how fungi and bacteria colonized different litters by using different initial dominance (pH) and by monitoring how they colonized litter alone (antibiotics).
Overall, we found that bacteria grew better and quicker in high pH than low pH and fungi grew better in low pH than high. Fungi and bacteria were shown to have different growth on different litters, showing that fungal and bacterial contribution change when degrading litters from different sources.
We found that fungi grew better without bacteria, independently of litter and pH. Bacteria on the other hand, were found to grow better together with fungi on “difficult” litter and better without fungi on litter with easily available carbon. This was consistent with earlier findings showing that bacteria need fungi and fungal enzyme activity when colonizing “difficult” litter. Our results implied that the availability of carbon is of higher importance than nutrient content when determining the fungal and bacterial contribution to litter decomposition.
The obtained results are important knowledge when further examining decomposition and fungal/bacterial effects on carbon and nutrients in soil. As farming evolves, it is important to know how decomposition functions, all in order to maximize plant growth and minimizing negative effects on the environment, minimizing over-fertilization and nutrient leaching. In turn, this information could also contribute to evaluating the possibility of decreasing the atmospheric carbon by increasing the soil bound carbon.

Supervisor: Johannes Rousk Co-supervisor: Margarida Soares
Master´s Degree Project 30 ECTS, Microbial ecology, 2016
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Isacsson Nilsson, Elvira
supervisor
organization
course
BIOM01 20161
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8891712
date added to LUP
2016-09-14 12:12:21
date last changed
2016-09-14 12:12:21
@misc{8891712,
  author       = {Isacsson Nilsson, Elvira},
  language     = {eng},
  note         = {Student Paper},
  title        = {Fungal and bacterial interaction during the colonization of litter in soil},
  year         = {2016},
}