Abstract:
Due to the high deforestation and climate change, the forests of Ecuador are endangered. In the future, there will be increasing drought, which is why the necessary afforestation have to be carried out with native tree species that meet these requirements. Therefore, it has to be clarified which tree species and provenances are suitable for this purpose.
This thesis deals with the drought tolerance of Cedrela montana and Juglans neotropica in the greenhouse. The seeds of the plants come from four different regions in Ecuador. Ger-mination was carried out in two different temperature chambers. In the greenhouse, the two-year-old plants were divided into three groups that were supplied with different amount of water. During the drought stress-experiment group A received 100% of its water require-ment, group B 50% and group C 25%. After 14 weeks all groups were supplied with 100% of their water needs during the resilience-experiment. After three times of rehydration the desiccation-experiment started, in which the trees of all groups were no longer supplied with water. During the experiment series, water consumption, predawn and afternoon leaf water-potential and leaf status were documented. In addition, at the end of the test series, the growth and the root-shoot ratio were determined.
Both tree species reacted very similar to the drought. There were hardly any differences in water consumption and water-potential. Only Cedrela montana had a higher number of leaves. The provenance and different germination temperatures had no significant influence. All groups reacted quickly to irrigation, so the afternoon water-potential were very similar in all groups. In the leaf status the gradation of the groups was still visible, but group B and C formed more leaves as the irrigation continued. Cedrela montana also had a higher number of leaves than Juglans neotropica. The germination treatment or provenance did not signif-icantly affect resilience. In the subsequent desiccation-experiment Group C of Juglans was best at dealing with the renewed dryness. This was evident in all parameters taken. All groups of Cedrela continued to behave similar. Significant differences could now be noted between germination treatments and provenances. In the aboveground growth, the grading of the groups was clearly recognizable, so in both tree species group A grew the most and group C the least. The root-shoot ratio behaved exactly the other way round. Group A had the lowest value on average, group C the highest. Again, significant differences between provenances and germination treatments were found.Both tree species showed a similar reaction over the course of the experiment, therefor both can be recommended for reforestation. The effects of germination conditions on the response to drought are not clear. For the species Cedrela montana, the provenance Barabon, and for Juglans neotropica, the Provenance Jipiro are considered to be suitable. As these have the largest root-shoot ratio, what makes them better equipped for increasing drought.
