تنش محیطی

Global forest area has decreased by nearly 180 million ha in three decades. So, many ecosystem services provided by forests have been threatened. Reforestation and afforestation are the most effective strategies for mitigating deforestation. Therefore, in a variety of countries worldwide, including Iran, several afforestation projects have been implemented; however, the quantity and quality of many afforested lands have decreased over time under the influence of catastrophic factors, environmental stress, and different management methods. Awareness and continuous monitoring of forest programs are some of the most fundamental forestry policies. Therefore, the monitoring of annual afforestation in the eastern Golestan province using Google Earth software was put on the agenda to prepare an afforestation map and identify the reasons for the success and failure of the implemented plans. According to the findings, 19,377.39 ha of afforestation have been planted in Golestan province. Of these, Maraveh Tappeh city has the highest amount of afforestation with more than 9,256 ha with C. arizonica L, C. sempervirens L. var. horizontalis (Mill.) Gord. and P. brutia Ten, mostly. The presence of suitable climatic and edaphic conditions in the Golidagh of Maraveh Tappeh City and the ArabDagh area of Kalaleh City played a prominent role in the success of artificial forests in these areas. It should be noted that wood smuggling, the presence of livestock, the occurrence of fires, the presence of natural and human obstacles, and continuous monitoring have been other factors affecting the success or failure of afforestation programs in the eastern Golestan province.

At this research it was investigated the effects of three prevalent environmental stresses in Iranian silkworm rearing farms on 6 kinds of Iranian silkworm hybrid performance. The climate stresses included warm/humid, warm/dry and temperature fluctuating conditions which compared with standard rearing climate conditions. The trail carried out within spring and early autumn rearing conditions. Some economic characters such as the percentages of good, middle, low and double cocoons, larval, pupal and total mortality, weight of total and good cocoon per 10000 larvae, number and weight of cocoon per liter, single cocoon weight, single cocoon shell weight and single cocoon shell percentage were surveyed. The obtained results of ANOVA showed the rate of larval, pupal and total mortalities at spring rearing season (3.0, 3.84 and 6.49% respectively) were higher under warm/humid condition compare to warm/dry (2.16, 3.47 and 5.33) and temperature fluctuating (2.22, 4.33 and 6.2) conditions (P˂0.05). Similarly at autumn rearing season warm/humid climate resulted to higher larval, pupal and total mortalities (10.18, 20.66 and 28.07% respectively) compare to warm/dry (5.72, 16.73, and 21.28 %) and temperature fluctuating (3.93, 2.58 and 6.41 %) rearing conditions (P˂0.05). Furthermore at spring and autumn seasons, respectively 2.22 and 6.11 % at larval mortality, 4.07 and 11.0 % of pupal mortality and 5.97 and 16.09 % at total mortality were observed (P˂0.05). According to the results of this study, humidity had no effect of pupal mortality while warm/humid condition increased the larval mortality (P˂0.05). Therefore silkworm hybrids would demonstrate better performance under warm/dry rearing condition compare to warm/humid climate (P˂0.05). Under humid rearing climate the apparent weight of cocoon will increase which is due to higher pupal weight (P˂0.05). The results further showed the existence of negative genetic correlation between resistance and productive characters. It is cleared that the hybrids performances varies based on different environmental condition (P˂0.05).