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CONCLUSIONS Oak mortality is caused by a combination of long- and short-term stresses. PowerPoint Presentation
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CONCLUSIONS Oak mortality is caused by a combination of long- and short-term stresses. - PowerPoint PPT Presentation


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Oak Mortality - influence of weather and environmental variables. Final thesis. Master’s programme in Ecology and the Environment, 2009. Marie Andersson. Supervisor: Karl-Olof Bergman. BACKGROUND - Severe o ak (Quercus spp.) declines have been recorded in many parts of Europe.

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Oak Mortality

-influence of weather and environmental variables

Final thesis. Master’s programme in Ecology and the Environment, 2009. Marie Andersson. Supervisor: Karl-Olof Bergman.

BACKGROUND

- Severe oak (Quercus spp.) declines have been

recorded in many parts of Europe.

- The causes of the declines are still poorly

understood.

AIM

- Clarifying the temporal process of oak

declines.

- Identifying environmental variables

that increase the risk of oak mortality.

METHODS

- Growth pattern of 72 dead and 72 living

oaks were analyzed using core samples.

- Tree and environmental variables were

analyzed for 216 dead and 335 living oaks.

Air pollutants

Summer droughts

Insect defoliations

Winter and

spring frosts

NH4+

Nitrogen compounds

Pathogenic fungi

Bacteria and viruses

Factors that have been shown to influence the oak’s vigour.

CONCLUSIONS

Oak mortality is caused by a combination of long- and short-term stresses.

Equal need of studying present as well as past factors influencing the oak’s vigour.

RESULTS & DISCUSSION

Highest mortality:

-during the last decade

Drought in 1992:

-triggering factor

Insect defoliation in 2003-2004:

-further reduced vigour

Environmental variables:

-weak influence

1992

2003-2004

Growth chronologies of dead and control oaks.

Bars represent the number of dead oaks per year.