Shifts in the spatio-temporal growth dynamics of shortleaf pine

Previous studies focusing on the growth history of Pinus echinata at the edge of its geographical range have suggested that changes in growth correspond to climatic and non-climatic (e.g., anthropogenic) factors. We employ a regime-dependent state-space model that allows us to detect and characterize the changes in tree growth dynamics over space and time using readily available dendrochronological and climatic data in the presence of various sources of uncertainty. We utilize methods common in atmospheric sciences but relatively unknown in ecology and forestry to develop a hierarchical model for tree growth and describe the growth dynamics. The utility of such methods for addressing ecological problems will grow as more high dimensional spatio-temporal processes are considered and datasets become more readily available.     

The loss of an indigenous constructed landscape following British invasion of Australia: An insight into the deep human imprint on the Australian landscape

Indigenous people play an integral role in shaping natural environments, and the disruption to Indigenous land management practices has profound effects on the biosphere. Here, we use pollen, charcoal and dendrochronological analyses to demonstrate that the Australian landscape at the time of British invasion in the 18th century was a heavily constructed one—the product of millennia of active maintenance by Aboriginal Australians. Focusing on the Surrey Hills, Tasmania, our results reveal how the removal of Indigenous burning regimes following British invasion instigated a process of ecological succession and the encroachment of cool temperate rainforest (i.e. later-stage vegetation communities) into grasslands of conservation significance. This research provides empirical evidence to challenge the long-standing portrayal of Indigenous Australians as low-impact ‘hunter-gatherers’ and highlights the relevance and critical value of Indigenous fire management in this era of heightened bushfire risk and biodiversity loss.     

Monitoring the growth of American beech affected by beech bark disease in Maine using the Kalman filter

The effect of beech bark disease on tree growth was tracked using paired resistant and susceptible American beech trees in two locations in Maine. Within each site, the paired trees were chosen in close proximity and with similar morphological characteristics (e.g. stem diameter and crown class) to minimize environment effects in subsequent analysis. A Kalman filter approach was employed to analyse the yearly time-dependent mean differences between paired susceptible and resistant tree-ring widths using simple structural time series models in state space form. On one site, under the influence of a moderate maritime climate, stand dynamics is hypothesized to account for the 34 year difference in onset of decline of trees in codominant, versus those in the intermediate crown classes. The harsher winter conditions associated with the second, more northerly site and known to limit the insect component of the disease complex, are hypothesized to be more of a factor in the close (six year) difference in decline onset between the two crown classes on this site. Some strengths and cautions in the Kalman filter approach are discussed in relation to the analysis of time-dependent trends in tree-ring series.