From land to water: the impacts of forest disturbances on carbon cycling in northern catchments

Boreal forests hold 32% of the world’s terrestrial organic matter and are continually disturbed by biotic and abiotic events. These disturbances are especially important since they facilitate the redistribution of nutrients within and between ecosystems, which can alter resource use and productivity. Yet how various types of disturbances, both individually and in combination, impact the overall resource balance of northern forests remains poorly understood. This thesis aims to advance our understanding of forest disturbances as drivers of forest resource balances, primarily through shifts in carbon, to better facilitate management of forests under climate change. Chapter 1 reviews current knowledge on forest disturbances and cross- ecosystem linkages. It also provides a summary of current gaps in our understanding of disturbances as drivers of forest function and possible downstream effects. Chapter 2 explores how disturbance history influences long-term carbon balance in boreal forests. Theory predicts that disturbances will increase with climate change but how the order and timing of multiple disturbance events will impact ecosystem function remains unresolved. Chapter 3 extends our understanding of forest carbon balance by asking how different disturbance types change the phenology and surface reflectance of boreal forests. Understanding how single disturbance events change growing season length and radiative forcing of forests can help predict potential feedbacks of forest health on climate warming. Chapter 4 tests how outbreaks of defoliating insects alter biogeochemical cycling from land to receiving waters through the consumption of foliage and subsequent release of nutrient-rich waste. Forests typically provide a pulse of nutrients to nearby waters in autumn when leaves are shed but insects disrupt this pattern by changing the timing, quantity, and quality of resource transfers. Chapter 5 traces terrestrial nutrients within lakes and asks if they can promote productivity in zooplankton communities. Finally, Chapter 6 discusses the main findings of the thesis and ends with possible directions for future research.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2022

Author dc:creator

• Woodman, Samuel Grant

Advisor dc:contributor.advisor

• Tanentzap, Andrew

• aquatic ecosystems
• boreal forest
• carbon fluxes
• Climate change
• disturbance ecology
• terrestrial aquatic linkages

Licence

• https://www.repository.cam.ac.uk/bitstreams/409bfd00-6cb0-41da-afd1-5114a9f522bd/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.96997

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/350520