Is the Seasonal Variation in Frost Resistance and Plant Performance in Four Oak Species Affected by Changing Temperatures?

Abstract

Research Highlights: We found seasonal variation in frost resistance (FR) and plant performance which were affected by growth temperature. This helps to better understand ecophysiological processes in the light of climate change. Background and Objectives: FR and photosynthesis are important plant characteristics that vary with the season. The aim of this study was to find out whether there is a seasonal variation in FR, photosynthetic CO2 assimilation rates and leaf functional traits associated with performance such as specific leaf area (SLA), leaf dry matter content (LDMC), chlorophyll content, stomatal characteristics and leaf thickness in two evergreen and two deciduous species, and whether this is influenced by different temperature treatments. Additionally, the trade-off between FR and photosynthetic performance, and the influence of leaf functional traits was analyzed. By understanding these processes better, predicting species behavior concerning plant performance and its changes under varying climate regimes can be improved. Materials and Methods: 40 individuals of four oak species were measured weekly over the course of ten months with one half of the trees exposed to frost in winter and the other half protected in the green house. Two of these species were evergreen (Quercus ilex L., Quercus rhysophylla Weath.), and two were deciduous (Quercus palustris L., Quercus rubra L.). We measured FR, the maximum assimilation rate at light saturation under ambient CO2 concentrations (Amax), chlorophyll fluorescence and the leaf functional traits SLA, LDMC, stomatal pore area index (SPI), chlorophyll content (Chl) and leaf thickness. Results: All parameters showed a significant species-specific seasonal variation. There was a difference in all traits investigated between evergreen and deciduous species and between the two temperature treatments. Individuals that were protected from frost in winter showed higher photosynthesis values as well as SLA and Chl, whereas individuals exposed to frost had overall higher FR, LDMC, SPI and leaf thickness. A trade-off between FR and SLA, rather than FR and photosynthetic performance was found.

Artificial light at night decreases plant diversity and performance in experimental grassland communities

“…This shows an intraspecific change associated with a reduction in plant growth that could be related to an increase in resistance (indicated by higher LDMC) and light protection, which is provided by hairs [ 23 , 25 , 26 ]. This can again be a seasonal effect, as species increase LDMC and decrease SLA in autumn if leaves are not shed [ 53 , 54 ]. The increase in hairiness was especially noticeable in harvest 2, which could be due to the fact that they help the plant to insulate against cold temperatures and not just against high irradiation [ 26 , 52 ].…”

“…the fitness of the individual plants was consistent, as was the performance [ 41 , 55 , 56 ]. Previous studies showed a strong decrease in F v /F m and PI abs , with senescence effects at the end of the season [ 53 , 54 , 57 ]. Thus, senescence effects within the remaining plant species can be excluded as driving factor between patterns.…”