Frost hinders the establishment of trees in highland grasslands in the Atlantic Forest ecotone region of southern Brazil

• Published in: Journal of vegetation science Vol. 32; no. 4
• Main Authors: Araujo Frangipani, Marcelo, Cristina Müller, Sandra, Anand, Madhur, Collins, Beverly
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.07.2021
• Subjects: Araucaria forest; Atlantic forest; Brazil; climate change; Climate prediction; cold; Correlation analysis; disturbance; ecotones; field experimentation; Forests; forest‐grasslands mosaics; Freezing; Frost; Frost damage; frost incidence; Frost resistance; functional traits; Grasslands; Gymnosperms; plant height; Regeneration; Regrowth; regrowth ability; Species; Survival; survival rate; Trees; variance; Variance analysis; Winter; Brazil
• ISSN: 1100-9233; 1654-1103
• DOI: 10.1111/jvs.13053

Questions Cold temperatures and freezing may hinder the process of forest expansion in moist climate regions, as predicted by the frost hypothesis. We examined the role of frost on the survival and regrowth of tree saplings under field conditions of open grasslands. Location Cambará do Sul, Rio Grande do Sul. Methods We established a field experiment protecting one of two groups of saplings of forest species from frost in grassland areas during the winter. We monitored 672 saplings from a total of seven species for 56 days. Saplings were brought back to the laboratory to evaluate regrowth rate and height. Survival curves of the two groups were compared using a Kaplan–Meier estimator. Correlation analysis was undertaken to estimate the relationship between survival and regrowth rate and a variance analysis was used to compare plant height between both groups. Results Species respond distinctly to frost incidence, with some not being affected by frost (two gymnosperms and Myrcianthes pungens). Most protected saplings had a higher above‐ground survival rate than unprotected ones (96.4% and 73.2%, respectively). Moreover, saplings that were damaged by frost showed differences in regrowth and height according to species identity, notwithstanding the fact that those from protected plots showed higher regrowth and height (88% and 25.65 cm compared to 68% and 17.15 cm). Conclusions Our results showed clear negative effects of frost on the survival rate of aerial parts of saplings during the winter and the regeneration of damaged plants. Species‐specific traits can offer frost resistance; however, together with other disturbances, frost may hinder the establishment of forest trees over grassland areas where frost events are common during the winter. Grassland–forest mosaics are often subject to disturbances that help maintain these unique ecosystems. In this paper we show that frost can have a significant effect halting the expansion of forest species over grasslands areas where this type of disturbance is common during the winter. With a field experiment, we demonstrate a clear negative effect of frost on the survival rate of aerial parts and on the regrowth rate and height of saplings of forest species.