Abstract
Thermal time models are useful to determine the thermal and temporal requirements for seed germination. This information may be used as a criterion for species distribution in projected scenarios of climate change, especially in threatened species like red cedar. The objectives of this work were to determine the cardinal temperatures and thermal time for seeds of Cedrela odorata and to predict the effect of increasing temperature in two scenarios of climate change. Seeds were placed in germination chambers at constant temperatures ranging from 5 ± 2 to 45 ± 2 °C. Germination rate was analyzed in order to calculate cardinal temperatures and thermal time. The time required for germination of 50% of population was estimated for the current climate, as well as under the A2 and B2 scenarios for the year 2050. The results showed that base, optimal and maximal temperatures were −0.5 ± 0.09, 38 ± 1.6 and 53.3 ± 2.1 °C, respectively. Thermal time (θ1(50)) was 132.74 ± 2.60 °Cd, which in the current climate scenario accumulates after 5.5 days. Under the A2 scenario using the English model, this time is shortened to 4.5 days, while under scenario B2, the time is only 10 hours shorter than the current scenario. Under the German model, the accumulation of thermal time occurs 10 and 6.5 hours sooner than in the current climate under the A2 and B2 models, respectively. The seeds showed a wide range of temperatures for germination, and according to the climate change scenarios, the thermal time accumulates over a shorter period, accelerating the germination of seeds in the understory. This is the first report of a threshold model for C. odorata, one of the most important forest species in tropical environments.
Highlights
Cedrela odorata L. is a tree of the Meliaceae family and is native to the American tropics [1].According to Mendizábal-Hernández et al [2], it is distributed in warm to subwarm climates in Mexico and requires fertile soil with good drainage; as such it is mainly found in the humid and subhumid tropics, associated with tropical deciduous forest, tropical semi-deciduous forest, and tropical rainforest, in addition to humid montane forest
C. odorata began to temperature germinate after threepercentage days, and at lowest temperature odorata began to germinate after three days, and at the lowest temperature they began at 28 days after sowing
C. odorata presented a wide range of cardinal temperatures, from −0.5 ◦ C to above 53 ◦ C
Summary
Cedrela odorata L. is a tree of the Meliaceae family and is native to the American tropics [1].According to Mendizábal-Hernández et al [2], it is distributed in warm to subwarm climates in Mexico and requires fertile soil with good drainage; as such it is mainly found in the humid and subhumid tropics, associated with tropical deciduous forest, tropical semi-deciduous forest, and tropical rainforest, in addition to humid montane forest. According to Pérez-Salicrup and Esquivel [6] and Sampayo-Maldonado et al [7], it is the most economically viable species for establishing commercial plantations, the most important for the forestry industry in Mexico, and preferred on the international market. It has a wide range of uses in construction, carpentry and cabinetmaking and represents one of the most planted species in the country [8]
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