دانلود رایگان مقاله زمان و گرما برای تولید مثل جنسی و مقایسه فنولوژی Chara hispida

Abstract

Geographical location affects the main ecological factors driving the timing of plants’ life events. In addition, studying phenology is the simplest procedure to track current global warming and its effects on the success and survival of different populations of the same species. Little is known about the effect of water temperature and its corresponding accumulated heat on charophytes’ phenology. We compared differences in water temperature and sexual reproductive phenology of Chara hispida in two ponds of two countries located at different latitudes (Spain and Switzerland) over the same year. We estimated the accumulated heat required to develop from one phenophase to another (unripe/ripe gametangia and oospores). Curve fitting techniques on water temperature showed an advance of 26 days in the Spanish spring onset. All phenological events happened for the first time around 40 days earlier in the Spanish pond, agreeing with the Hopkins’ Bioclimatic Law prediction. C. hispida sexually reproduced in a daily mean temperature (DMT) range of 10–25 ◦C and needed 600 growing degree-days (GDD) to ripen gametangia in the Spanish pond. The Swiss population required a higher DMT (15 ◦C) to begin to reproduce, and ∼700 GDD to initiate gametangia ripening. Temperature (as well as radiation) is one of the most important drivers of reproductive phenology, and accumulated heat is a better predictor than DMT for charophyte phenology. In the foreseeable warming scenario, we assume that C. hispida sexual events would advance by more than one month in Switzerland and expand at the end of the season, considerably lengthening its reproductive period.

4.4. Final remarks and conclusions

This study represents the first attempt to compare geographical differences of charophyte phenology. The effect of geography is important to understand the potential effect of future increases in temperatures at different latitudes, particularly higher ones. The current global warming trend is causing an advance of the spring onset, and this process is latitude dependent (Parmesan, 2007). Thus, climate change could be affecting the fulfilment of Hopkins’ Law. This study was exploratory and,therefore, comparatively long-term, inter-site and multi-latitude studies are needed to accurately define the interactive influences of all environmental factors (particularly temperature and solar radiation) on charophyte phenology and to provide a deeper understanding of the suitability of the application of Hopkins’ Law for aquatic ecosystems. For the moment, with the data obtained in this study, we can say that (i) temperature is one of the most important drivers of charophyte reproductive phenology, and (ii) accumulated heat (GDD) rather than daily mean temperature has to be known to predict phenological events. Ifthe foreseeable warming in Switzerland continues (an approximate increase of 3–5 ◦C in air temperature by the end ofthe century −(CH2011, 2011),the same difference currentlymeasured between the studied Spanish and Swiss ponds), we can foresee that the sexual events of C. hispida would be advanced by more than one month, considerably lengthening the reproductive season of the macrophyte species.