Capacity of a forest to buffer temperature: Does canopy tree species matter?

article de 13 p.

International audience

英语. We studied the effects of tree species and tree density on the capacity of a forest to buffer understory temperatures during the summer period. We dissociated tree-species and light effects by integrating incident solar irradiance and its proportion intercepted by the canopy into our analyses. We measured solar radiation and air temperature over three consecutive years (2018, 2019 and 2020) in 16 plots in Central France composed of mature stands of sessile oak and Scots pine with three types of composition: monospecific oak, monospecific pine and oak-pine mixture, and two levels of tree density. Air temperature and solar radiation were recorded simultaneously in the experimental plots and in a reference plot without forest cover.<p>Our results show that the higher the incident irradiance the greater the difference in minimum temperature, and that the higher the intercepted irradiance the greater the difference in maximum temperature between below-canopy and open conditions. We found that tree species had a significant effect on the buffering capacity even when the light factor was taken into account. For a given incident irradiance and a given proportion of intercepted irradiance, the pine plots buffered understory temperatures less than the oak plots. Our results also show that higher maximum temperatures occurred in the understory than in open conditions for low values of intercepted irradiance and high values of incident irradiance, especially in the plots where Scots pine was present. The two species differ in leaf albedo and in their ability to regulate transpiration during droughts and these two characteristics may explain our results. Our study shows that Scots pine is less able to buffer summer temperatures than sessile oak. These results are of interest to forest managers since reducing stand density and mixing tree species are considered to be silvicultural strategies that can help cope with climate change.</p>