Loading in 2 Seconds...
Loading in 2 Seconds...
Climate change influence on decomposition and soil microbes. Bob Edmonds. Topics. 1) Evidence for climate change in the Pacific Northwest 2) Influence of climate change on ecosystems 3) Effects of climate change on soil microbes and decomposition 4) Importance of lignicolous fungi
1) Evidence for climate change in the Pacific Northwest
2) Influence of climate change on ecosystems
3) Effects of climate change on soil microbes and decomposition
4) Importance of lignicolous fungi
5) the diversity of fungi causing wood decay
6) brown versus white rot fungi
7) influence of global warming on wood decay fungi
Temperature effects on fungi
Influence on wood decay rates
Ecosystem responses to global warming will be complex and varied (Shaver et al. 2000)
Bardgett, Richard D., Freeman, Chris, Ostle, Nicholas J. 2008. ISME JOURNAL 2 (8): 805-814 Microbial contributions to climate change through carbon cycle feedbacks
Interacting effects of global change forcing factors on belowground processes act directly on plant communities to alter primary productivity, litter quantity and quality, and root production rates.
Atmospheric CO2 concentrations have indirect effects on soil moisture, while temperature can alter N and moisture availability.
The quantity and quality of soil organic matter and labile root exudates interact with microbial communities to alter rates of biogeochemical cycles.
Microbial activity regulates belowground feedbacks to climate change by altering rates of decomposition and reactive N (e.g. N2O) production.
Chemistry and long-term decomposition of roots of Douglas-fir grown under elevated atmospheric carbon dioxide and warming conditions JOURNAL OF ENVIRONMENTAL QUALITY 37 (4) : 1327-1336
Elevated atmospheric CO2, concentrations and warming may affect the quality of litters of form plants and their subsequent decomposition in ecosystems, thereby potentially affecting the global carbon cycle. We used small diameter roots of Douglas-fir seedlings that were grown for 4 yr in a 2 x 2 factorial experiment: ambient or elevated (+ 180 ppm) atmospheric CO2 concentrations, and ambient or elevated (+3.8 degrees C) atmospheric temperature.
Exposure to elevated CO2 significantly increased water-soluble extractives concentration, but had little effect on the concentration of N, cellulose, and lignin of roots. Elevated temperature increased %WSE and decreased the %lignin content of fine roots.
This study indicates that short-term decomposition (< 9 mo) and long-term responses are not similar. It also suggests that increasing atmospheric CO2 had little effect on the carbon storage of Douglas-fir old-growth forests of the Pacific Northwest.
Soil C decomposition is sensitive to changes in temperature, and even small increases in temperature may prompt large releases of C from soils. Older, more-resistant C fractions may be more temperature sensitive. We incubated soils at constant temperature to deplete them of labile soil OM and then successively assessed the CO2-C efflux in response to warming. We found that the decomposition response to experimental warming early during soil incubation (when more labile C remained) was less than that later when labile C was depleted. These results suggest that the temperature sensitivity of resistant soil OM pools is greater than that for labile soil OM and that global change-driven soil C losses may be greater than previously estimated.
The impact of carbon-nitrogen dynamics in terrestrial ecosystems on the interaction between the carbon cycle and climate was studied using an earth system model of intermediate complexity, the MIT Integrated Global Systems Model (IGSM).
Simulations show that consideration of carbon-nitrogen interactions not only limits the effect of CO2 fertilization but also changes the sign of the feedback between the climate and terrestrial carbon cycle.
In the absence of carbon-nitrogen interactions, surface warming significantly reduces carbon sequestration in both vegetation and soil by increasing respiration and decomposition (a positive feedback).
If plant carbon uptake, however, is assumed to be nitrogen limited, an increase in decomposition leads to an increase in nitrogen availability stimulating plant growth. The resulting increase in carbon uptake by vegetation exceeds carbon loss from the soil, leading to enhanced carbon sequestration (a negative feedback).
Under very strong surface warming, however, terrestrial ecosystems become a carbon source whether or not carbon-nitrogen interactions are considered.
Models that ignore terrestrial carbon-nitrogen dynamics will underestimate reductions in carbon emissions required to achieve atmospheric CO2 stabilization at a given level.
As a group, lignicolous fungi play a vital role in recycling the carbon and nutrients locked up in wood. Some species are capable of killing trees. They contribute CO2 to the atmosphere and organic matter to soil, and provide wildlife and plant habitat. They occur in all ecosystems with wood, including deserts
Most are saprophytes on dead wood, but many invade living plant to decay heartwood.
Each has its ecological niche
Mostly basidiomycetes with a few ascomycetes (Xylariaceae)
– may not be able to invade wood without alteration by hyphomycetes, bacteria or yeasts.
Tremellales – 101 species
Aphyllophorales – 948 species
Agaricales – 620 species
Total – 1669 species
There are fewer brown rot fungi (106 sp.) than white rot (1563 sp.) – 6% of total
They evolved from the white rot fungi.
Majority of brown-rot fungi are in the Polyporaceae
Most are associated with conifers
Initially brown rot fungi cause greater weight loss in wood than white rot fungi.
of wood decay fungi are generally more widely dispersed than species of higher plants
But some like E. tinctorium only occur only in the west even though suitable hosts (balsam fir and Fraser fir occur in the east).
So far all species are endemic, as far as we know.
Effect of temperature on growth and wood decay
Effect on fungal fruiting
On average optimum temperature for growth is about
28 C; as low as 20C and has high as 35 C
variation in CWD decay rates
Mackensen et al. (2003)
Over 56 years – 315 species, 1400 locations
First fruiting date is now earlier and last fruiting
date is later due to increases in later summer
temperature and October rainfall. Many species now fruit in spring as well as fall.