مطالعات باستان­‌گیاه­‌شناسی حوضۀ آبگیر سد کنگیر برمبنای بقایای گیاهی مکشوف از بنای ساسانی جهانگیر در استان ایلام

Abstract
Jahangir building is one of the Sassanid sites in the catchment area of Kangir Dam in Ilam province. Due to dry and hot summers and short winters, the vegetal structure of the region includes thermophilic plants such as crops, pastures, forest and groves. Due to the lack of our knowledge about the vegetation of Ilam during the Sassanid era, this research presents the results of a study on the plant remains obtained from the Jahangir building. The purpose of these studies was to identify the types of plants in the area and its subsistence economy based on plant vestiges found from fireplace, tandoor, burnt layers and graves excavated at this site. The ecology and geographical distribution of identified plants in the Kangir basin and the nature of modern ecosystems in the region, indicates the presence of trees and shrubs such as almond, oak, maple, tamaris and willow in the Sassanid period. The presence of such species in the mentioned contexts shows that in the neighboring environment, there were forests, mountains, steppes and riverine structures similar to those are available today in the Kangir basin. The small amount of charcoal found in Jahangir building cannot be a suitable criterion for commenting on the distribution and density and identification of trees in the vegetation of this area during time. The remains of seeds and fruit stones also show that crops (especially cereals) have been consumed as the main source of food. The abundance of wheat and barley found in the in some context including the tandoor is an evidence for existence of Agricultural lands and a subsistence economy based on the agriculture in the Sassanid period. This is in parallel with the current agriculture ecosystem of the Kangir, basin that is located in an altitude between 700-2000 m above sea level. The study of possible changes in this ecosystem is subject to further archaeobotanical studies in the prehistorical and historic sites of Ilam.
Keywords: Archaeobotany, Steppe forest, Jahangir, Sassanid, Ilam.
Introduction
This Sassanid site is located in the catchment area of the Kangir Dam in the west of Iran on Quaternary sediments. The building, in connection with other contemporary buildings, is situated in the vicinity of Kangir River alongside one of the important routes connecting Iran to Mesopotamia. According to historical texts and seismotectonic and morphotectonic studies, in addition to political-social and environmental factors, the occurrence of earthquakes and also the socio-political reasons could be considered as the main factors for its decline. The various works of art obtained from this 17-hectare ancient site, which is referred to as a manor summer residence with a prestigious/residential function, are influenced by the features of the Sassanid art reserving for itself some independent local characteristics.
Based on the results of dating analysis and cultural artifacts obtained from the excavated spaces of the site, despite the reality that the settlement started from the Parthian period, indeed, the architectural vestiges of Jahangir is belonged to the Sassanid era, which were used by the nomads until the first Islamic centuries.
From a geological point of view, the ancient area of Jahangir is located in the structural zone of Zagros and folded Zagros subzone. The foothills and valleys of Zagros have been a suitable place for human settlements in the past due to the availability of water sources and agricultural lands. The vegetal cover of Kangir region belong to Nobo-Sindian and Irano-Turanian regions and include forester (especially Persian oak), stepped and grove vegetation’s. In addition, most of the invasive and annual plants grow in uncultivable lands, and hygrophilous plants grow on the banks and beds of river Jahangir. Arable lands also include planting crops such as cereals, vineyards and walnut and apple orchards.
In order to understand the vegetation cover of the Kangir during the Sassanid period, this research presents the results of the study of plant remains obtained from the Jahangir building. The purpose of these studies is to identify the types of plants in the Kangir catchment basin and the subsistence economy based on the plant remains found in the deposits collected from the fireplace, tandoor, burnt layer and excavated grave related to the first and second architectural phases. The paper aimed at answering to the questions such as what was the vegetation cover around the Jahangir building during the Sassanid period and how was the subsistence economy of the residents of the site in the Sassanid period?
The hypothesis of this research included the diversity of vegetation of this basin in the Sassanid period was also diverse and mostly belonged to steppe-forest and mountainous habitats like what is present today. The existence of rainfed and irrigated agricultural ecosystems in Ilam also shows that the subsistence economy of the inhabitants of Jahangir in the Sassanid period was based on the planting of garden and agricultural products, especially grains

Material and Methods
The results are coming from archeobotanical studies that included field operations (sampling and extraction of plant remains from the deposits collected by the dry method) and identification of them in the Archaeobotanical laboratory of the World Heritage Site of Shahr -i Sokhta was done with a binocular stereomicroscope with 80x magnification and a metallurgical microscope with 1000x magnification.
Discussion
The cultivable plants of the Kangir catchment area in the sassanied period based on 8481 seeds, included crops such as cereals (wheat and barley) was probably cultivated used rainfed irrigation in the region.
It should be noted that the identification of a piece of nut- shell of the peach in the contents of the excavated fireplace can represent horticultural activities. Peach pollen from the Rosaceae family is not easily distinguished by palynologists from apple and cherry pollen. Therefore, the remains of peach in Jahangir’s monumental building are important evidence of the planting of this tree in ancient Iran
Also, non-cultivable plants, such as wild grasses, wild pulses and wild plants have also been constant and disturbing companions of agricultural fields and gardens in the region. Pollen evidences of these plants have been identified from Maharlu lake in the Fars province. The study of 83 pieces of charcoal shows that the natural trees of the Kangir included oak, almond, maple, willow, tamaris, and goosefoot, which were used as fuel. The presence of oak charcoal remains in most contexts confirms the forester vegetation cover of the Kangir catchment area which we still see in the region today.
This ecosystem is under serious threat due to livestock grazing in the forests and agricultural operations (in the lower levels of the forest). Zagros oak forests up to 2500 cal. BP have had a relatively stable situation. During this period, Maharlu lake has humid hydrological conditions and humid climatic conditions prevailed on the Iranian plateau.
In the Lake Urmia, the high abundance of tree pollens, especially oak, and the relative lack of pollens of sagebrush and goosefoot indicate a more humid climate, a relatively high water level in the lake, and a lower level of salinity in the past 1200-1600 years. With the increase of human activities and the emergence of dry climatic conditions after 2000 cal. BP We are witnessing the decline of oak forests. During this period, livestock and agricultural activities and tree planting have played an important role in the vegetation dynamics of the region
Previously, the pollen evidence of oak (natural trees) and cereals (indicator of human activities) from Maharlu and Parshan lakes in the southwest and Almalu in the northwest have been reported from the Sassanid period.
The use of wood in the construction of the Sassanid palaces at Fars, (224-651 AD) was common. Evidence of cypress timber has been reported in Qale Dokhtar and Ardashir I Palace located in Firuzabad (period of power transfer from Parthian to Sassanid) and Sarostan Palace located east of Maharlu lake in Shiraz plain (late Sassanid period and early Islamic centuries).
Conclusion
These evidences most likely indicate the history of tree planting in ancient Iran. In addition, palynological studies show that since the beginning of the Sassanid period, we have seen a significant increase in planted trees, including plane tree. Pistachios and maples have decreased and we are facing an increase in desert bushes and shrubs. Probably, the increase of garden trees and the development of urbanization are effective factors in the destruction of the pistachio-almond forest steppes in the lower altitudes of the Maharlu lake basin and its drying. Pollen evidences of desert shrubs and natural or planted trees (willow, maple and tamaris) have also been reported from Maharlu Lake.
The study and identification of the plant remains of the Jahangir showed that according to the ecology and geographical distribution of the identified plants and the nature of the ecosystems at the Kangir region either they existed naturally (plant resources used as fuel) or were planted by the residents of the region to meet their daily needs (food or fodder). The large amount of wheat and barley grains found in tandoor and the grave is a proof of the existence of agricultural lands and subsistence economy based on agriculture in the region like today.