Stand Dynamics and Disturbance History of Champlain Valley Clayplain Forests

Studies of stand dynamics can explain how species interactions and disturbances drive forest structure and recruitment patterns of tree species. It is difficult to generate an understanding of stand dynamics and successional trends of forests in areas that have a long history of intense land use such as the Champlain Valley of Vermont, where over 230 years of agricultural activity has acutely and permanently influenced the landscape. The valley clayplain forest, a rare natural community containing endangered herbaceous plants and overstory tree species assemblages that are rare in Vermont, has been fragmented by agricultural use of the Champlain Valley. This study used dendroecological methods and assessments of forest structural conditions to describe the tree recruitment history and structural dynamics of two old-growth valley clayplain forest patches. Our results indicate that the valley clayplain forest has a species composition and recruitment history that has been heavily influenced by human land use throughout at least the past 230 years. We found that Quercus spp., typically considered characteristic of the valley clayplain forest, are being replaced by late-successional species such as Tsuga canadensis. Additionally, other human influences such as invasive species threaten to further alter the composition and dynamics of valley clayplain forests in the near future

Dendroecology of Gymnanthes klotzschiana Müll. Arg. trees, naturally growing in Northern Uruguay.

Ameridendro

“These Trees Have Stories to Tell”: Linking Dënesǫ́łıné Oral History of Caribou Use with Trample Scar Frequency on Black Spruce Roots at Ɂedacho Kué

For thousands of years Ɂedacho Kué (Artillery Lake, Northwest Territories) has been a key water crossing site for barren-ground caribou (Rangifer tarandus groenlandicus). Human disturbance of barren-ground caribou habitat in northern Canada has emerged as an important focus of study in the last decade; particularly in the Bathurst range of the Northwest Territories where caribou populations have declined by more than 95% since the 1980s. Guided by local Indigenous leaders and Elders, a collaborative research project was developed with the Dënesǫ́łıné people of Łutsël K’e Dëne First Nation (2012 – 14). This paper describes linkages between knowledge derived from Dënesǫ́łıné oral history and quantitative dendroecological analysis of trample scars on black spruce (Picea mariana) root samples collected at Ɂedacho Kué to provide a better understanding of caribou use at this location. Findings from oral histories and dendroecology analysis were consistent with one another and with previous dendroecology study in the region, although some discrepancies were detected in data from 1995 – 2006 that require further study to elucidate. Key findings include relatively low caribou use at Ɂedacho Kué during the 1930s and late 1960s, with use increasing into the 1970s and peaking in the late 1980s, as well as Elder and hunter reports of no caribou in some years between 2005 and 2012. This work addresses a gap in scientific data about barren-ground caribou movements at Ɂedacho Kué prior to satellite collar use in 1996 and corroborates previously documented oral histories about the enduring value of Ɂedacho Kué as critical habitat to barren-ground caribou. Given the drastic decline of the Bathurst caribou over the last two decades, more research is needed to understand movements and their relationship to population dynamics. In this context, the research approach described in this paper could be used as an example of how to meaningfully bring together place-based Indigenous knowledge and science in addressing an urgent issue of Arctic sustainability.    Depuis des milliers d’années, Ɂedacho Kué (lac Artillery, Territoires du Nord-Ouest) sert d’important point de franchissement de cours d’eau pour le caribou de la toundra (Rangifer tarandus groenlandicus). La perturbation anthropique de l’habitat du caribou de la toundra dans le Nord canadien a fait l’objet d’études importantes ces dix dernières années, plus particulièrement dans l’aire de répartition de Bathurst, dans les Territoires du Nord-Ouest, où les populations de caribous ont chuté de plus de 95 % depuis les années 1980. Un projet de recherche collaborative guidé par des chefs et des aînés autochtones locaux a été conçu en consultation avec le peuple Dënesǫ́łıné de la Première Nation Łutsël K’e Dëne (2012 – 2014). Cet article décrit les liens entre les connaissances dérivées de l’histoire orale des Dënesǫ́łınés et l’analyse dendroécologique quantitative des cicatrices de piétinement se trouvant sur les échantillons de racines d’épinettes noires (Picea mariana) prélevés à Ɂedacho Kué afin de mieux comprendre l’utilisation de ce lieu par les caribous. Les constatations découlant de l’histoire orale et de l’analyse dendroécologique concordaient ensemble ainsi qu’avec une étude dendroécologique antérieure de la région, bien que certains écarts aient été décelés dans les données de 1995 à 2006, écarts qui se doivent d’être étudiés afin d’être élucidés. Parmi les principales constatations, notons l’utilisation relativement faible de Ɂedacho Kué par les caribous pendant les années 1930 et la fin des années 1960, une utilisation accrue dans les années 1970 ayant atteint un sommet vers la fin des années 1980, ainsi que le signalement de l’absence de caribous par les aînés et les chasseurs au cours de certaines années entre 2005 et 2012. Notre recherche comble un manque de données scientifiques relativement aux déplacements du caribou de la toundra à Ɂedacho Kué avant que les colliers émetteurs à transmission par satellite ne commencent à être employés en 1996. Elle corrobore l’histoire orale documentée précédemment au sujet de la valeur durable de ?edacho Kué en tant qu’habitat critique du caribou de la toundra. En raison de la chute importante de la population du caribou de Bathurst ces deux dernières décennies, de plus amples recherches s’imposent afin de comprendre les déplacements et leur lien avec la dynamique de la population. Dans ce contexte, la démarche de recherche décrite dans cet article pourrait servir d’exemple montrant comment concilier les connaissances autochtones d’un endroit avec la science pour faire face à un enjeu urgent de durabilité de l’Arctique.

Modelling shadow in agroforestry systems based on 3D data

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Dendroecology of Araucaria angustifolia under two geomorphological conditions in the seasonal semideciduous forest and mixed ombrophilous forest ecotone of Paraná, Brazil.

Ameridendro

Dendroecology of Drimys brasiliensis Miers (Winteraceae) in two Atlantic cloud forests in Paraná State, Southern Brazil.

Ameridendro

X-ray based tree ring analyses

In this thesis, two x-ray based dendro-analyses (batch-wise microdensitometry and energy dispersive x-ray fluorescence (EDXRF)) and the conditions under which these methods could be used on the two typical boreal conifers Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) were evaluated. For density measurements using batch scanning x-ray densitometry, sample preparation and density calibration are vital to acquire high resolution and precision in densitometric measurements. Thickness and alignment should be adapted to give optimal resolution without loss of precision. Samples should be extracted to remove resins before wood density measurements. Ca, Mn, Fe, and Sr and in most cases K and Zn could thus be measured in an efficient way using EDXRF. Significant differences in concentrations between tree rings were found for all of these elements except Sr, indicating that tree ring concentrations of these elements could be correlated to changes in the tree environment. For Mn a correlation between soil pH and Mn concentration in tree rings was found. Other correlations between tree ring element concentration and tree environmental factors were also found. For most elements in tree-rings of Scots pine and Norway spruce it seems that the concentration is due to environmental conditions during the year the tree-ring was developed and several years afterwards. It is concluded that microdensitometry and EDXRF analyses on increment cores are cost-efficient and non-destructive analyses of wood properties. Batch-wise, x-ray based dendrochemical analysis provides opportunities for more property-based use of wood raw material and for environmental monitoring