Multi-scale Influence of Snowmelt on Xylogenesis of Black Spruce

Abstract

Snowmelt is considered to affect growth of the boreal forest. So, we tested the hypothesis that late snowmelts delay the onset of xylogenesis and reduce xylem production in trees. Timings of xylem formation were compared to the dates of complete snowmelt combining a 7-year monitoring of cambial activity with meteorological records in four plots of Picea mariana in Quebec, Canada. The spatial and temporal variability in snowfall was analyzed separately, so taking into account both the long-and short-term effects. Snowfall occurred from October to May, with a snow cover lasting 173-199 days. Overall, xylogenesis lasted 99-117 days, with onsets ranging from late May to mid-June. The highest cell productions were observed in the warmest site, where the longest periods of growth were observed. Although at long-term the effects of snowmelt were significant for both onset and duration of xylogenesis and cell production, at short-term only the relationship between the onset of xylogenesis and the date of complete snowmelt was significant. The initial hypothesis could be confirmed only partially. The different responses to the long-and short-term analyses demonstrate the multi-scale influence of snowfall on tree growth and the determinant role of nutrient cycling in the productivity of boreal ecosystems.

Effects of soil warming and nitrogen foliar applications on bud burst of black spruce

“…In this context snow characteristics, given its importance in the boreal forest during the resumption of the growing season, perform an important role as an interface between these two environments, favoring or limiting the exchange of heat. In North America, global warming resulting in decreased snow permanence on the ground and earlier snowmelt is strongly related to local year-to-year temperature trend and snow depth (Peng et al, 2013;Rossi et al, 2011). Although soil temperature requires several years to manifest an effect, it remains a crucial factor to consider when evaluating the effect of climate change on tree growth.…”

“…Significant effects of soil temperature on bud burst were found in BER, the site at higher altitude with shorter snow-free periods and growing seasons (Rossi et al, 2011). In this site, temperature is a more limiting factor and so the plants may be more sensitive to small increases.…”

“…Thus, at high latitudes the time of soil thaw, and consequently the availability of water in liquid form for roots, plays a key role in the resumption of vegetative growth (de Fay et al, 2000;Rossi et al, 2011). The increase in soil temperature in spring, which has been observed to cause earlier root activity (Lupi et al, 2012b), also anticipates water uptake and the onset of trunk sap flow (Repo et al, 2008).…”

“…As confirmation of this, the different seasonal pattern of temperature in the two years influenced the onset of bud burst, which was earlier in the year when spring temperatures (of both soil and air) were higher. Vice versa, SIM is a warmer site at the lower edge of the closed black spruce forest distribution, where snowmelt usually occurs in early May (DOY 120) and the growing season is consequently longer (Rossi et al, 2011). Independently of year, bud burst started on average on DOY 150 and soil warming didn't affect the onset.…”

Inter- and intra-annual patterns of seed rain in the black spruce stands of Quebec, Canada

“…The mean annual temperature ranges between -2.1 and 0.9°C , while total precipitation ranges between 1006 and 1162 mm (Rossi 2015). The sites are characterized by long winters with the coldest temperature reaching -44.8 °C and a snow cover deeper than 1.5 m (Rossi et al 2011). The summers are short, with the highest temperatures exceeding 29 °C in all sites.…”