Evaluating the plantation success by mountain almond (Amygdalus scoparia Spach.) and its effect on vegetation and soil in Arjan habitats of Jamal Beyg region, Fars province

Introduction
In the last 30 years, many forests have been destroyed in the Zagros region of Iran. Afforestation is necessary to reduce the pressure on the natural forests. Forest plantation and protection should be at the center of conservation efforts, significantly since plantations can offset the negative impact of climate change and be effective in absorbing atmospheric pollutants and helping to improve air quality. This research was conducted with the aim of evaluating the success of afforestation with the mountain almond (Amygdalus scoparia Spach.) in Arjan (Amygdalus elaeagnifolia Spach.) habitats of Jamal Beyg, Fars province and its effect on the understory vegetation, especially herbal species and soil. Comparing Arjan with mountain almond can provide additional information, to know the conditions of the native species in the region and the planted species, and it is a kind of comparative mode. In fact, evaluating the success and quantifying the ecological effects of the afforestation carried out by the executive organizations, which has been done at great expense, can guide managers for better decision-making. As no study has been done in this area yet, this research is the first one that quantifies the results of almond plantations in the Jamal Beyg region.
 
Materials and Methods
In order to check the percentage of survival and according to the budget and facilities, since the plantation rows were very long, three rows of planted shrubs in the Jamal Beyg region of Euclid in Fars province were randomly selected and the number of empty planting holes was counted. There are naturally but rarely shrubs such as Arjan (Amygdalus elaeagnifolia Spach.). In order to evaluate the existing vegetation, after initial sampling and based on the adequacy of the sample, 30 circular sample plots of 1000 square meters were taken in the form of a random-regular grid with dimensions of 100×100 meters. In the sample plots, the density of shrubs, their crow width, and survival, as well as the frequency of regeneration were measured. In order to check the number of species present in the plantation and control areas, at the end of May and the beginning of June 2021, all the plant species in the sample plots were identified or after they were collected and transferred to the herbarium, with the help of photos taken in the field, were identified. The life form and biological form of plant species were determined using the Raunkiaer system. Some physical and chemical characteristics of the soil such as texture, percentage of organic matter, phosphorus, EC, and pH amount were also measured and compared with the control area in the vicinity of the range which has similar topographical characteristics without afforestation operation. Due to the non-normality of the data distribution and the failure of various transformations, the Mann-Whitney test was used to compare two species of Arjan and mountain almond in terms of density, regeneration frequency, and crown area.
 
 Results and Discussion
The survival rate of the plantation was 95 %, and the plantation area had a density of 342 trees per hectare, which created a canopy cover of five percent. The regeneration density of mountain almond and Arjan species was estimated to be 90 individuals and 4.5 individuals per ha, respectively. Afforestation with the mountain almond species in this area has increased the number of herbaceous species in such a way that there were 18 plant species belonging to 13 families in the afforestation area while 12 plant species belonging to eight families in the control area (without plantation area). In terms of canopy area, there was no significant difference between the two species of mountain almond and Arjan. In terms of regeneration density, there was a significant difference between the mountain almond and Arjan, and the regeneration density of the mountain almond was significantly higher than Arjan. The amount of organic matter (1.62), nitrogen (3.89), and phosphorus (11.02) of the soil in the afforestation area was higher than control area, and the ratio of carbon to nitrogen (C/N) in the afforestation area (0.46) was lower than control area.
 
Conclusion
The results of this research indicate the significant success of mountain almond afforestation in the Jamal Beyg region, Fars province. Afforestation in this area has increased organic matter and also the number of herbal species. The existence of a significant natural regeneration of the mountain almond indicates that the stand is on the true way of its succession. In order to control the grass cover and prevent fires, it is better to do light grazing in the spring season in the stands. Also, if there is a history of the presence of Pistacia atlantica in the area, planting its seeds or seedlings under the shelter of existing shrubs will help the stability of the stand. It is suggested that sufficient research be carried out to determine the appropriate method for determining the age of shrubs in such a way that natural regeneration can be separated from planted shrubs. The main goal of initializing a seed garden is to produce the modified seeds of the desired forest species in abundance, cheap, continuous, and easily accessible, far from the reach of unwanted pollen and with better genetic quality and quantity. To select suitable genotypes of a species in terms of traits such as resistance to drought stress, the genomic selection method can be used. Jamal Beyg aforestation is a valuable seed garden for future plantation. Considering the significant survival of mountain almonds and the possibility of natural reproduction, it is suggested to use this nurse species in the restoration of similar fields in the study area. Considering the effect of mountain almond afforestation in improving the soil properties of the region, it is suggested to give more importance to bioengineering operations and stabilization of slopes with this shrub in the Fars Province watersheds. As this afforestation has supported herbal species richness, it is suggested that the results of afforestation be explained to rural communities so that they are encouraged to preserve and protect forest plantations.