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Research

Carbon Dynamics

Carbon Dynamics in Trees

About 45% of plant biomass is carbon, thus rendering this element fundamental for plant growth and development. Trees generally have relatively large amounts of stored non structural carbon in their tissues (C that is not part of cell walls and membranes). C reserves are thought to help trees buffer environmental stress. However, trees often do not deplete their C reserves, even under strong C demands. Does this mean that tree growth is generally not limited by C availability? Can trees under drought (which decreases C assimilation) eventually make use of this carbon? Do trees store non structural C compounds for functions other than supplying C when C inputs via assimilation are not sufficient to meet growth demands? Link to Publications




FireResearch

Fire Regimes and Tree Physiology

Fire regimes in many fire-dependent forests of the US have changed substantially due to the active suppression of fires since the early 1900. As a result some forests are now much different than they were under their natural fire regimes. What are the consequences of these changes on resource availability and tree performance? Can management reverse negative effects of these changes on trees? Link to Publications




Conifer Ecophysiology

Ecophysiology of Conifers

Some conifer species in the interior Rocky Mountains hold a relatively large proportion of foliage relative to others. Yet, in spite of consequences on water use and resistance to drought, they may all co-occur in similarly dry sites suggesting that the variability in hydraulic traits is associated with species-specific biomass allocation patterns and physiology. How variable are hydraulic traits among species? How does this variability relate to tree physiology and biomass allocation? Link to Publications




Masting

Masting

In some plant populations flowering does not occur every year and when it occurs it is synchronous among individuals (masting). What are the physiological mechanisms underlying this synchrony? Link to Publications





Old Trees

Old Trees

Old trees are humbling: they have stood silent, still and brave for centuries or millennia in the precise spot where they germinated. What traits contribute to this extraordinary resilience? Link to Publications






Dormancy

Prolonged Dormancy

Some herbaceous, perennial plants show an intriguing life history strategy: they occasionally remain belowground and not come up for one or several years. What triggers these plants to stay below ground? Why do plants skip a growing season thereby foregoing the opportunity to acquire resources and to reproduce? Link to Publications




Bark Beetles and Conifers

Bark Beetles

In the Northern Rocky Mountains, mountain pine beetle outbreaks are occurring from lower elevation ponderosa pine to high elevation whitebark pine forests (where beetle outbreaks were historically very rare). When beetles overcome tree defenses, they establish under the bark where they disperse fungal spores carried in their bodies. Beetles then mate, lay eggs and developing larvae feed from phloem and fungal tissues. We are studying whether and how resources stored in the sapwood of host trees (which are accessible to the fungi but not to the beetles) affect beetle performance. We are also investigating whether changes in fire regimes have altered the defense capability of ponderosa pine and the subsequent susceptibility to beetle attack. This is work still in progress done by my graduate students.




Invasive Plants

Invasive plants are intriguing on many accounts. They become overabundant in new ranges, but not in their native ranges. What physiological traits contribute to their ability to spread and become invasive? Link to Publications


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