نوع مقاله : علمی- پژوهشی
نویسندگان
1 استادیار، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران
2 دانشیار، موسسه تحقیقات جنگل ها و مراتع، سازمان تحقیقات، آموزش و ترویج کشاورزی، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: Ground vegetation is an important component of the forest ecosystem, through which many indicators of biodiversity, stand stability, and the effects of global changes caused by human activities can be assessed. Changes in ecosystem components are studied by the "monitoring" process. Ground vegetation monitoring is being carried out as a part of forest monitoring projects in different regions of the world. In the Irano- Turanian forests, such studies have not been conducted yet, and the studies conducted have generally described the stractural and environmental features of the stand. In this study, ground vegetation in the Irano- Turanian forests of Khojir National Park in Tehran Province, Iran were investigated and monitored for three years.
Methodology: Khojir National Park is located in the Jajrud protected areas complex, in the eastern highlands of Tehran Province, about 25 km from Tehran megacity. The forest habitat has a gentle north-northeast slope and an average altitude of 1500 meters above sea level. Permanent sample plots of 100 square meters were used to study and monitor forest cover and its regeneration, and permanent microplots of one square meter were used to monitor ground cover. The floristic composition, quantitative and qualitative characteristics of vegetation cover, plant species diversity, and regeneration were studied in three consecutive years, 2021, 2022, and 2023, in mid-May. All plant species present in the microplots were recorded based on density (individuals per area unit), life form, and phenology. Also, the over of ground vegetation, moss and lichen cover, shrub cover, litter, bare soil, rocky outcrops, and surface gravel were accurately estimated and recorded in the microplots. Comparisons of the studied variables were performed using repeated measures analysis of variance or nonparametric Friedman and Wilcoxon tests.
Results: The ground vegetation cover in the microplots in the first year of the study (22.3%) was higher than in the second and third years (17 and 18.7%); however, the comparison of the means did not consider this difference significant. The moss/lichen cover (which in the study area were mainly soil surface mosses) had a decreasing trend and in 2023 (10%) was significantly lower than in previous years (16.4 and 15.8%). The percentage of litter cover decreased significantly from 2021 to 2023 (43% to about 16%) and the percentage of bare soil and surface gravel increased significantly. Based on the results obtained, from a total of 79 species recorded in the micro-plots of the Khojir site, 62% were annual plants (therophytes), 20% were hemicryptophytes, 13% were chamaephyte, 4% were cryptophyte, and 1% were phanerophyte (seedlings, saplings, or small woody stems). The Asteraceae family with 15 species was the largest plant family, followed by Brassicaceae, Poaceae, and Lamiaceae, respectively. The density of plant species fluctuated in the three years of the survey, so that there was no significant difference in the first and last years (Average 242 and 249 individuals per square meter); but the density was higher in the second year (Average 344 individuals per square meter). The density changes were not the same for all species, and significant differences were observed in this regard. Some therophyte species had a decrease in density and some had an increase. The density of hemicryptophytes increased significantly in the years of the study (Average 2.4, 3.8 and 5.9 individuals per square meter). Overall, species richness and diversity indices of the ground vegetation had an increasing trend in the years of the survey, and the evenness indices did not show a significant difference. In the Khojir habitat, only the regeneration of the mountain almond (Prunus lycioides (Spach) C.K.Schneid.) was recorded in the sample plots, and the wild pistachio (Pistacia atlantica Desf.) lacked regeneration. 80% of the almond regeneration was without nurse. The study of the abundance in height classes curve also showed that the number of saplings and young individuals of almond has decreased in recent years.
Conclusion: In general, a three-year study of permanent monitoring plots in Khojir National Park revealed that the vegetation and moss cover of the ground and surface litter decreased during this period, and bare soil, rocks, and surface gravels became more visible; changes in the density of different species had different trends; but the diversity and richness increased. The Khojir Pistacia- Prunus habitat was not in a good condition in terms of regeneration.
کلیدواژهها [English]
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