0890-B4
J. Farzadmehr 1
The phonology of forest tree species and gradient of temperature were studied in Caspian forests from sea level (0m) to altitude of 2200m. Thirtem study plot were chosen at the following elevations: 0, 200, 400, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000, 2100 and 2200 m. In each plot, one max-min thermometer was fixed on the northern aspect of a tree stem at a level of 2m from ground. Phenological studies and temperature records were done from November 1996 to December 1998. Time of occurrences of phonological phenomena such as foliation, defoliation, anthesis, and seed maturity was studied for 23 species. The study showed that during the critical months, the temperature variations accompanied by severe frosts are quite high, so that in April at 1200 m altitude, the temperature range was 35 0C and in May 1998 at altitudes above 1400m it was up to 32 up to37 0C. The phonological diagrams of tree species if overlaid on gradient of absolute temperature, show that important trees such as beeches, maples, and hombeams, which were located at altitudes above 1400m lost their leavers and flowers in May, and so there was no seed production by these trees in this year.
Iranian forests are one of the most valuable natural resources that a correct management to keep them in a sustainable status. Forest management operations should be done with regards to total ecological conditions of a forest. Phenological study is one of the main branches of a forest. The object of phonology is to find the precision time of occurrence of important phenomenous such as foliation, anthesis, seed ripeness act. These phenomena are mainly affected by climatological factors. Among different climatological factors, temperature and moisture are the mail factors in occurrence of phonological phenomena in wet and arid regions, respectively. Phenology is a strong instrument to find adaptable ecotypes of forest species in other to establish them in forest stands of different regions. Cold regions with late spring frost, need varieties, ecotypes and cultivars that are late growth and can escape from frost damages. According to what said above, one of the advantages of phenology in forestry is to choose adaptable ecotypes to forestation that in addition to easy establishment are of high potential for wood production. Numerous phonological studies have been carried out all over the world and northern forests of Iran (Burarel, 1974; Lacaz, 1969; Khtamsaz, 1984; Djavanshir, 1992; Rahami, 1993). These studies show that application of phenology different forest management operations lead to beneficial and reliable results.
The study was carried out in Bandepay forest, located in northern of Iran (Caspian forest). The range of altitude was 0-2200m. Thirteen study plots, each with area of 225 m2 (15 * 15) were established at the elevations of 0, 200, 400, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000, 2100 and 2200. Plots were established on the northern aspect of forest, and the interval of plots from each other was 200m. The plot 0 elevation was out of forest.
In each plot, one maximum- minimum thermometer was fixed on the northern aspect of a tree stem at a level of 2m from the soil surface. Phonological studies and temperature records were done from Nov. 1996 to Dec. 1998 every week for the months of March, April and May which phenologyally are critical periods, and every other week for the rest of the year.
Time of occurrence of important phenomena such as: foliation (50% of bursting and leaf tip appearance), anthesis (50% of flower are opened for pollination or fertilization), seed ripeness (50% of seeds with ripe color), and defoliation (50% of leaves are shed) was studied for different species in relation to different altitudes.
The means of maximum and minimum temperature records in relation to altitudes are show in figure 1 maximums and minimums of temperature for the critical period are shown in figure 2, and gradient of annual temperature is given in the figure 3. Absolute maximum and minimum for the study period are presented in table 1. The time of occurrence of studied phonological phenomena are shown in figures 4-7. Table 2 is the legend of figures 4-7.
According to the results of this study, during the critical months the temperature variations accompanished by severe frosts are quite high, so that in April at altitude the temperature range was 35 0C and in May 1998 at altitude above 1400m it was 32 0C up to 37 0C. The phonological diagrams of tree species) figure 4-7) if overplayed on gradient of absolute temperatures (figure2), show that important trees such as beeches, maples, and hornbeams which were located at altitudes above 1400m lost their leaves and flowers in May 1998, and therefore there was no seed production by these trees in this year. This fact shows that seed production took place at irregular intervals in trees, especially beeches. According to the results of different studies, beech produces seeds only every 3,5,7, or more years (Djavanshir, 1992;Rohami; 1993).
I fall 1996 there was a full seed crop for trees in Brndpay. In the following year there were no harmful frosts in the region as the absolute minimum temperature did not drop below 3.5 0C., yet despite this, there was little flowering. In spring 1998 there was plentiful flowering, but severe frost at altitudes higher than: 1400m, killed all flowering two years (1999 and 2000), there were also severe frosts in May I study region so there was no seed production in Bandpay between the years 1996-2000.
1- Bouvaral, P., 1974.L' Adaptation ecologigue des Arbers forestiers, Application a la selection in pesson, p(ed). Ecologie Foresteire Ganthier- Villars, Paris.
2- Diavanshir, K., 1992 Phenology of trees of Kheirud-kenar's forest, final draft, Natural Resources faculty, University of Tehran, Iran.
3- Khatamsaz, M., 1984. Phenology of trees of Nshahr arbotum, Reseach Institute of forest and Rangelands, Iran.
4- Lacaz, J.F., 1969. In bouvarel, P., 1976. L' Adaptation ecologigue des Arbers forestiers, Application a la selection in pesson, p(ed). Ecologie Foresteire Ganthier- Villars, Paris.
5- Rahmani, R., 1993. Phnological study of Kheirud-kenar's forest, M.Sc. dissertation, Natural Resources Faculty, University of Tehran.
1 - Ph.D. Student of Natural Resources, Range Management, Natural Resources Faculty, University of Tehran, Iran.