Title: Studying global change
through investigation of the plastic responses of xylem anatomy in tree rings
Journal: New Phytologist 2010, 185:42-53 (pdf)
Abstract:
Variability in xylem anatomy is of interest to plant scientists because of the role water transport plays in plant performance and survival. Insights into plant adjustments to changing environmental conditions have mainly been obtained through structural and functional comparative studies between taxa or within taxa on contrasting sites or along environmental gradients. Yet, a gap exists regarding the study of hydraulic adjustments in response to environmental changes over the lifetimes of plants. In trees, dated tree-ring series are often exploited to reconstruct dynamics in ecological conditions, and recent work in which wood-anatomical variables have been used in dendrochronology has produced promising results. Environmental signals identified in water-conducting cells carry novel information reflecting changes in regional conditions and are mostly related to short, sub-annual intervals. Although the idea of investigating environmental signals through wood anatomical time series goes back to the 1960s, it is only recently that low-cost computerized image-analysis systems have enabled increased scientific output in this field. We believe that the study of tree-ring anatomy is emerging as a promising approach in tree biology and climate change research, particularly if complemented by physiological and ecological studies. This contribution presents the rationale, the potential, and the methodological challenges of this innovative approach.
Title: Intra-annual growth of Larix decidua and Picea abies along an altitudinal gradient in the Lötschental, Switzerland (pdf)
Context: Trace 2009, Otočec (SL) April 16th - 19th 2009
Abstract:
By the end of the century, in the absence of significant curtailment in greenhouse gas emissions, models predict that the mean annual temperature will increase by 4-5 C, with the greatest increase occurring during autumn and winter. How forest trees, among the largest biomass carbon pool on Earth, will respond to the continued rise in temperature is unknown.
In order to further understand and perhaps predict the effects of projected temperature increase in alpine forest ecosystems, the Dendro Sciences Unit of the WSL in 2007 has begun observations of intra-annual forest growth along both the south and north facing slopes of the Lötschental valley, a central alpine valley in Switzerland. The air temperature difference (approx. 4 ºC) between the treeline and the valley bottom and the two ecologically different tree species make this site an ideal place in which to monitor the effects of climate change on tree growth under temperature limited conditions. A total of 7 sites with trees of Larix decidua and Picea abies have been selected along an elevation transect of approx. 1000m.
In our contribution will present how the effect from warming - as a function of elevation - has induced shifts in growing season length and cellular activity during the years 2007 and 2008. Differences along the gradient and between the species are discussed in a context of rising temperature changes.
Title: Temperature-induced differences in timing of intra-annual growth of subalpine Larix decidua and Picea abies. (pdf)
Context: EGU 2010, Vienna (CH), May 3rd- 7th 2010.
Abstract: Phenological observations of plants are mostly concentrated on foliar life-cycle events such as bud break, leaf unfolding or leaf falling, which are observable from “outside” the plant. Additionally, as such phenological cues primarily characterize the beginning and the end of the growing season, many important growth processes within the growing season and within the plants remain poorly quantified.
Our research aims at describing tree growth over the full life cycle, i.e., from the beginning to the end of both primary and secondary growth along a 4°C natural temperature gradient. This gradient is roughly what is projected to occur over most land areas due to global warming. In this talk, we will present results about differences in timing of needle break and tree-ring formation, including timing of cambial division, cell enlargement, cell wall thickening and maturation, between two different species (deciduous Larix decidua versus evergreen Picea abies) growing in the subalpine forest of the Lötchen valley, in the central Swiss Alps. Growth observations are based on weekly micro-coring of 48 trees distributed along a 900 m elevation gradient sampled during the 2007 and 2008 growing seasons. We observed that the onset of the growing season changed by 3–4 days per 100 m elevation whereas the ending of the growing season appeared minimally related to altitude. The timing of cell enlargement, wall thickening and maturing tend to delay in a somewhat cumulative manner and cause increasing lags with elevation. This cumulative behavior is not observed for phase endings.
If associated with the monitored altitudinal lapse rate of −0.5 °C per 100 m, these results translate into a lengthening of the growing season by ~7 days per degree Celsius.
Observed differences along the altitudinal/temperature gradient and between the species will be the focus of discussion and may be linked with possible species-specific growth response to projected climate warming.