Effects of elevated mean and extremely high temperatures on the physio-ecological characteristics of geographically distinctive populations of Cunninghamia lanceolata

Abstract

Conventional models for predicting species distribution under global warming scenarios often treat one species as a homogeneous whole. In the present study, we selected Cunninghamia lanceolata (C. lanceolata), a widely distributed species in China, to investigate the physio-ecological responses of five populations under different temperature regimes. The results demonstrate that increased mean temperatures induce increased growth performance among northern populations, which exhibited the greatest germination capacity and largest increase in the overlap between the growth curve and the monthly average temperature. However,tolerance of the southern population to extremely high temperatures was stronger than among the population from the northern region,shown by the best growth and the most stable photosynthetic system of the southern population under extremely high temperature. This result indicates that the growth advantage among northern populations due to increased mean temperatures may be weakened by lower tolerance to extremely high temperatures. This finding is antithetical to the predicted results. The theoretical coupling model constructed here illustrates that the difference in growth between populations at high and low latitudes and altitudes under global warming will decrease because of the frequent occurrence of extremely high temperatures.

Figure 1. Sampling locations of the populations of Cunninghamia lanceolate.

ES stands for Enshi, XN stands for Xiuning, LC stands for Lechang, RS stands for Rongshui, and XY stands for Xinyin. Figure 1 was drawn by Xiaorong Jia, and the maps here was generated by Arc GIS 9.0 (www.esri.com/software/arcgis).

Figure 2. Response of the germination percentages of the seeds of different populations of C. lanceolata to temperature.

The data are expressed as average valuesLeaf starch (mg·g⁻¹) standard deviations. The lowercase letters indicate the analysis of the difference within the same population under different temperature treatments. The uppercase letters indicate the analysis of the difference among different populations under the same temperature treatment (P < 0.05).

Figure 3. Response of the biomass and RGRs of the seedlings of different populations of Cunninghamia lanceolata to temperature.

The data are expressed as average values ± standard deviations. The lowercase letters indicate the analysis of the difference within the same population under different temperature treatments. The uppercase letters indicate the analysis of the difference among different populations under the same temperature treatment (P < 0.05).

Figure 4. Environmental temperature ranges, current monthly average temperature variation ranges, and monthly average temperature variation ranges after a temperature increase of 3 °C of the five populations.

(a) Enshi, (b) Xiuning, (c) Lechang, (d) Rongshui, and (e) Xinyin. The curves shown in the figure are quadratic RGR-temperature function regression curves (Enshi: y  = −0.0001x² + 0.005x − 0.0297 [R² = 0.40, P = 0.001]; Xiuning: y = −0.00008x² + 0.0038x − 0.0227 [R² = 0.16, P = 0.081]; Lechang: y = −0.00007x² + 0.0038x − 0.0198 [R² = 0.24, P = 0.017]; Rongshui: y = −0.00009x² + 0.0044x − 0.0235 [R² = 0.18, P = 0.051]; Xinyi: y = −0.0001x² + 0.0057x − 0.0438 [R² = 0.38, P = 0.001]). The blue areas indicate the current monthly average temperature variation ranges of the provenances of the populations. The red areas indicate the monthly average temperature variation ranges of the provenances of the populations after a temperature increase of 3 °C.

Figure 5. Pattern of the responses of different populations of the same species in different latitudes/altitudes to an average temperature increase and an extremely high temperature and the coupling effect of the average temperature increase and the extremely high temperature.

The dotted line indicates a scenario in which the average temperature increases. The solid line indicates a scenario in which the average temperature increases, which is also accompanied by an increase in the frequency of the occurrence of extremely high temperatures. With greater latitude and altitude of the provenance of the population, the promoting effect of the temperature increase on the growth of the population becomes stronger, and the tolerance of the population to extremely high temperature stress may become weaker. Therefore, the advantages of populations in high latitudes/altitudes will decrease under extremely high temperature conditions.