مطالعۀ فلوریستیک و مقایسۀ دو بخش مرکزی و ضربه‌گیر ذخیره‌گاه جنگلی تنگ‌خشک سمیرم در استان اصفهان

ذخیره‌گاه جنگلی تنگ‌خشک در شهرستان سمیرم واقع در جنوب استان اصفهان قرار دارد. در پژوهش حاضر، فلور این منطقه، دارای دو بخش مرکزی (تحت حفاظت و قرق) و ضربه‌گیر (بدون حفاظت)، به‌‌منظور معرفی ترکیب فلوریستیک، اشکال زیستی، پراکنش جغرافیایی و درک اثرات قرق بر ساختار پوشش گیاهی بررسی شد. در این منطقه، در مجموع 194 گونه (182 گونه از بخش مرکزی و 57 گونه از بخش ضربه‌گیر) متعلق به 45 تیره از نهاندانگان شناسایی شد. تیره‌‌های asteraceae، fabaceae و poaceae به ترتیب ازنظر تعداد گونه دارای بیشترین فراوانی در منطقه بودند. اشکال زیستی براساس سیستم رانکایر شامل 40 درصد همی‌کریپتوفیت‌‌ها، 27 درصد تروفیت‌‌ها، 17 درصد کامفیت‌ها، 10 درصد ژئوفیت‌ها و 6 درصد فانروفیت‌ها در بخش مرکزی و 44 درصد همی‌کریپتوفیت‌ها، 30 درصد کامفیت‌ها، 11 درصد ژئوفیت‌‌ها، 9 درصد تروفیت‌‌ها و 7 درصد فانروفیت‌ها در بخش ضربه‌گیر بود. بررسی پراکندگی جغرافیایی گونه‌ها نشان داد در هر دو بخش مرکزی و ضربه‌گیر به ترتیب با 60 و 61 درصد، بیشترین گونه‌ها به ناحیۀ رویشی ایران - تورانی تعلق داشتند. نتایج این پژوهش نشان داد قرق ذخیره‌گاه جنگلی تنگ‌‌خشک، موجب افزایش تنوع پوشش گیاهی، به‌‌ویژه حضور انواع گونه‌های درختی در بخش مرکزی شده است.

a floristic study and comparison of the core and buffer zones of the tange-khoshk forest reserve of semirom in isfahan province

in the present study, the flora of tange-khoshk forest reserve of semirom in isfahan with two zones, the core zone (under protection) and the buffer zone, was investigated to introduce the floristic composition, life forms, and geographical distribution, and understand the effects of exclosure on the vegetation structure. in this region, a total of 194 species belonging to 45 genera of plants were identified, of which asteraceae, fabaceae, and poaceae were the most abundant in terms of the number of species. in terms of life forms, hemicryptophytes were dominant in both core and buffer zones. the study of the geographical distribution of the species showed that in both core and buffer zones, most species belonged to the irano-turanian vegetation area. this research showed that the exclosure of the tange-khoshk forest reserve had increased the diversity of vegetation, especially the presence of various tree species in the core zone.key words: iran, endemic, zagros, chorology, flora, protected area. introductionthe method of protecting forests in iran is mainly in the form of reserves. each forest reserve has a central part that is fully protected. around it, there is a buffer zone where activities such as animal grazing, human interference, and recreational activities are allowed, which leads to the protection and existence of the core zone. the tange-khoshk forest reserve, with an area of 6000 hectares, is located in the south of isfahan province and 40 km from semirom city. it was enclosed as a reserve since 1372 ah (1993) to preserve the tree species pistachio (pistacia atlantica subsp. mutica). in this research, in addition to evaluating the flora, life forms, and chorology of the vegetation, the effect of exclosure on the structure of the vegetation in the core and buffer areas was investigated over 28 years. materials and methodsthe plants in the area were collected and identified based on reliable sources and the apg iv system (2016) and then deposited in the herbarium of the isfahan agricultural and natural resources research and education center. raunkiaer’s (1934) classification was used to determine their life form. also, the red data book of iran and some authoritative articles were used to evaluate endangered species. in addition, the chorotype of the species was identified according to their distribution areas in iran and other countries and the compilation of the geographical divisions of iranian vegetation by takhtajan (1986), zohary (1973), and assadi (1986-2018). results and discussionbased on the results, the number of species in the core and buffer zones was 182 and 57 species, respectively, which indicates a higher species diversity in the core area. in investigating the effect of exclosure on vegetation diversity, if it is assumed that the variables that affect plants, such as climate, soil, and slope, are the same, then the differences in the species diversity of the core and buffer zones are the result of grazing in the buffer area. among the identified plant species, there were 11 species of trees and shrubs, mainly growing in the core area, which is due to the influence of the area’s enclosure. in the end, it can be said that it is very likely that the enclosure can have positive effects on the improvement of soil conditions and, as a result, the establishment and reproduction of vegetation in the unprotected areas of zagros.in this research, there was a significant difference between the presence and absence of tree species inside and outside the reserve. tree species such as pistacia atlantica subsp. mutica, celtis australis subsp. caucasica, lonicera nummulariifolia, platanus orientalis, atraphaxis spinosa, rhamnus pallasii, prunus macrocarpa, and acer monspessulanum only grow in the core zone. however, species such as prunus lycioides have been easily established in both regions due to their long, sharp thorns, and rough and dense shape that protect them from grazing.also, the diversity of the poaceae family was more in the exclosure region than outside, which can be caused by the complete vegetative growth of these species due to the creation of desirable conditions, such as preventing livestock grazing in the core zone. this factor, along with the abundance of seeds in this family, can be one of the factors for the high distribution and diversity of these species in the entire reserve.the abundance of the genus astragalus, which is a genus special to the mountainous regions of the irano-turanian vegetation area, indicates the cold and semi-arid mountain conditions in the region. the herbaceous species of this genus were more present in the core area, which, due to the palatability of these plants, is most likely grazed by livestock in the buffer zone. also, the comparison of endangered plant species (en) and plants in lower risk (lr) showed that the number of these species is 13 in the buffer area and 32 in the core zone. it seems that the limited distribution and presence of these species in the buffer zone is due to grazing in this area.this research showed that the buffer zone had been destroyed due to reasons such as excessive livestock grazing, the existence of agricultural lands on the edge of the reserve, fire, harvesting, and cutting of trees. these factors have caused, in some parts of the region, invasive species such as scariola orientalis, euphorbia heteradena, and eremurus spectabilis that occupy the region. therefore, significant threats such as road construction and agricultural activities can cause the loss of reserves as the last natural habitat of some endangered species. the study of species endemism showed that in this region, there are 16 species endemic to iran belonging to 9 genera and five families, of which 12 species are relatively vulnerable. in this way, it can be said that 25.8% of the total species in semirom’s tange-khoshk forest reserve are endemic, and preserving and studying these specie seems to be necessary. fundingthis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.