جستجوی مقالات مرتبط با کلیدواژه « تغییرات فصلی » در نشریات گروه « جنگلداری »

Recently, the most important topic in water management was to determine the effects of urban forests and green space on partitioning gross rainfall (GR) into the rainfall interception (I), stemflow (SF), and throughfall (TF). The main aim of this research was to quantify the seasonal variations [Growing Season (GS), and Non-Growing Season (NGS)]) in I by individual Fraxinus rotundifolia trees in the Chitgar Forest Park located in a semiarid climate zone of Iran. From the September 2012 to September 2013, GR and TF were collected through 6 and 12 rain-gauges, respectively. I was calculated as the difference between GR and TF. Fifty rainfall events were recorded and the cumulative GR was measured 156.0 mm. Over the study period, GS, and NGS, I ranged 19.4%, 23.0%, and 16.2%, respectively. Significant positive correlations were observed between I and GR over study period (R= 0.862), GS (R= 0.862), and NGS (R= 0.950) (p

Mycorrhizal fungi are essential components of sustainable soil–plant systems and have a main role in sustainable forestry. The present study was carried out to investigate the evaluating status of mycorrhizal symbiosis, activities of acid and alkaline phosphatase and some nutrients (phosphorus, nitrogen and potassium) in rhizosphere of Lonicera nummulariifolia located in Chahartagh Ardal habitat in Chaharmahal va Bakhtiari Province. For this purpose, roots of five trees of L. nummulariifoli and soils around them were sampled in spring and autumn. The results showed that Lonicera is an incredible symbiosis since the percentage of colonization was 90.2 and 80.6 in spring and autumn, respectively. The activity of acid and alkaline phosphatase also was 240.59 and 392.85 in spring and 146.48 and 295 (ρNP) in autumn, respectively. All measured elements had higher values in spring than autumn. Correlation was significant between soil phosphatases with total nitrogen and organic matter in spring and alkaline phosphatase with total nitrogen in autumn. High level of AMF colonization and acid phosphatase activity in spring may be due to good conditions of soil and growing of root hairs are in the early growing season. With regard to the microbial origin of alkaline phosphatase, increasing this enzyme in spring illustrated increasing the quality and quantity of microorganisms and mineralization of organic matter and rising nutrients. In general, impressive percentage of mycorrhizal colonization in L. nummulariifolia indicates dependency of this species to mycorrhizal symbiosis. Therefore, the role of these fungi in planting with this species, especially in destruction habitats, is vital.

The aim of this research is seed bank seasonal variation patterns in the Populus caspica reserved forest، Noor forest park. Above ground vegetation sampling were made by Braun-Blanquet method. Soil samples were collected during autumn، winter and spring and were studied using seedling emergence method. Seasonal variation in the soil seed bank during spring، autumn and winter indicated that maximum and minimum average size of soil seed bank were in autumn and spring by 747 and 426 seeding/m2 respectively. Numerical analysis of biodiversity showed that seed bank floristic data did not have differences during the third season، but its eveness in the spring was higer than autumn and winter seasons. Also the results indicate that only 5 tree species including; Ficus carica، Morus alba، Prunus divaricata، Alnus glutinosa and Populus caspica were able to produce persistent soil seed bank. In this case، seeds of P. caspica with average density of 83 seed/m2 were presented only in spring soil seed bank so we are cocluded that P. caspica to be included in transient soil seed bank. Totally، results of this study reiterd that the low seeds germination rate of P. caspica is not due to its low seed viability، but this failure is due to low persistence of its seeds. rather due to the low rate persistence Populus Caspica that has seeds lose their viability quickly، This is due to the failure to provide favorable conditions germination (light and high humidity) rapidly lose their viability.

Rainfall after passes through the biomass and necromass، penetrates into the soil and make large qualitative changes because of rhizospher، microorganisms، horizon thickness and organic matter. This process is the result of atmospheric، hydrological and biogeochemical reactions influenced by seasons. In this study we investigated seasonal variations of base cation leaching (Ca2+، Mg2+، Na+ and K+) in the soil of mixed Hyrcanian beech located in district one of Shastkolate forest، Golestan province. Shallow and deep soil leachate samples (0-10 and 10-50cm) were taken within a year (2008/12/21 to 2009/12/21). Amount of base-cations of shallow and deep soil leaching in different seasons were compared by the one way variance and Duncan test. Results showed the amount of Ca2+، Na+ and Mg2+ contents of shallow soil leaching in seasons are different significantly (P<0. 05) so that the most leaching of Sodium and Magnesium were observed in winter. Sodium and Magnesiumin deep soil leaching were different significantly (P<0. 05) so that the most leaching of them were observed in winter and spring respectively. With the recognition of chemical properties variations of shallow and deep soil leaching، we can suggest that exploitation programs perform in February to make optimized biogeochemical cycle and maximized base cation leaching.

Forest canopy leaching changing based on the different factors, is an effective factor causes to increase nutrition in a short time. We investigated the effect of seasons on the variation of base-cations (Ca2+, Mg2+, Na+ and K+) in throughfall and forest floor leaching of the beech species in the mixed Hyrcanian beech forest in Golestan province, Iran. Throughfall and forest floor leaching samples were taken through a year (2008/12/21 to 2009/12/21). Amount of base-cations in throughfall and forest floor leaching (Ca2+, Mg2+, Na+ and K+) were compared by One-Way variance analysis in the different seasons. Results showed that the amount of Ca2+, Na+ and K+ in throughfall were different in seasons significantly except for Mg2+ (p<0/05). Also all base cations were significantly different in forest floor leaching (p<0/05). The most and least cation leaching in throughfall and forestfloor leaching belonged to K+ (112/11 and 65/75 Kg ha-1year-1) and Mg2+ (6/1 and 4/5 kg ha-1 year-1), respectively. Forest canopy leaching increased the nutrition in soil solution especially in summer and fall that soil is dry and competition is intensive. So this process caused the competition between trees and organisms decreased and efficiency product increased finally. So the information of leaching intensity in different seasons is necessary for the economic-management programming to use the best leaching process.

The morphology of deciduous plants changes seasonally. In addition, deciduous and ever-green plants encounter with internal changes as a consequence of seasons. Enzymes activities alter with changes of temperature, drought and salinity. Plants adapt to environmental changes with alteration of enzymes activities. In this study, the peroxidase activity was measured in leaves and shoots of Eucalyptus viminalis during a year. Peroxidase activity was measured by spectrophotometer (530 nm) by use of Worthington method. Data were analyzed to determine statistical relationship in peroxidase activity of individual trees and seasonal changes of enzyme activity by SPSS software. Results showed that peroxidase activity was different in individual trees. The difference of peroxidase activity in different individual trees was little in April, July and January but differences were higher in September and November. The peroxidase activity decreased in all individual trees from April to July. Peroxidase activity of leaves was higher than those of branches in all of studied months. There was negative correlation between some month of peroxidase activity (α<0.05). There was not any correlation between leaves and branches peroxidase activity. Individuals were classified to three classes according to their peroxidase activities using JMP software (centroid method).

Quercus brantii var. persica (oak manna tree) is a valuable tree species in forests of western Iran. This species has been adapted to rough conditions of its habitat such as extreme summer and winter, long drought period and high elevation. For determining physiological patterns and alteration related to the establishment of oak in this environment, the changes of total non- structural carbohydrates and amylase activity in oak trees were studied in a less manipulated habitat during an annual cycle. The amount of total non- structural carbohydrates and amylase activity were measured by enzymatic and electrophoresis (PAGE) methods. Results indicated that non- structural carbohydrates concentration (glucose, fructose and sucrose) in March (before bud burst) was more than January ones. After bud burst and leaf expansion, when photosynthetic activity was high and after the beginning of drought period the concentrations of glucose and fructose increased continuously to September. Contrariwise the amount of sucrose and starch decreased slowly during this period. After summer and with falling temperatures, the total non-structural carbohydrates increased in November. In January, the content of starch was very low but the level of soluble carbohydrates was high. Thus the energy supply for metabolic processes in trees is secured during cold and hard winter seasons. Total non-structural carbohydrates ranged from 18.5 to 37.25 mg gdm-1. Seasonal changes of α-amylases coincided considerably with changes of starch and glucose concentrations of oak manna trees during the investigation period.