پديد آورندگان :
حشمتي، مسيب سازمان تحقيقات و آموزش و ترويج كشاورزي - مركز تحقيقات و آموزش كشاورزي و منابع طبيعي كرمانشاه، تهران، ايران , قيطوري، محمد سازمان تحقيقات و آموزش و ترويج كشاورزي - مركز تحقيقات و آموزش كشاورزي و منابع طبيعي كرمانشاه، تهران، ايران , شيخ ويسي، مراد سازمان تحقيقات و آموزش و ترويج كشاورزي - مركز تحقيقات و آموزش كشاورزي و منابع طبيعي كرمانشاه , عرب خدري، محمود سازمان تحقيقات، آموزش و ترويج كشاورزي - پژوهشكده حفاظت خاك و آبخيزداري، تهران، ايران , حسيني، مجيد سازمان تحقيقات، آموزش و ترويج كشاورزي - پژوهشكده حفاظت خاك و آبخيزداري، تهران، ايران
چكيده لاتين :
Introduction Zagros forests (Quercus sp.) contribute to recharging groundwater, controlling air pollution, ecotourism, by products, livestock grazing, sustaining agriculture, soil conservation and flood control. Due to geological and topographical properties of Zagros area, however, these forests are more vulnerable to deforestation agents mainly drought driven die-off phenomenon. The effects of climate change are generally expected to reduce the growth and survival of forests, which not only predisposes them to being disturbed by insects and disease, but also increases the vulnerable ones to higher tree mortality. As a consequence of continued climate change, forest mortality has spread throughout Zagros areas inducing a severe environmental disaster. According to some research, several biotic and abiotic factors, such as extreme weather conditions, drought, storms, heat, and insect fluctuations, are responsible for oak reduction. Regarding rainfall deficit, soil moisture storage and reduction in evapotranspiration should be considered as the possible solutions through short term measures. Consequently, harvesting runoff by micro-catchment construction such as crescent -shaped bund (CSB) is a possible adapted measure in the semiarid regions for enhancement of soil moisture. In order to evaluate the effects of runoff harvesting on forest rehabilitation, the present research aimed to analyze the effects of CSB on soil soil moisture content. 2. Material and Methods This study was conducted in Kalehzard site located in Kermanshah, west of Iran (UTM; 38S682887E, 3748385N). The respective annual precipitation and temperature are 440 mm and 15.2 ºC, indicating the semiarid region. The winter is so cold that the temperature drops below zero on average for 90 days during December, January and February. The summer is relatively hot and dry. A hill with a 15% slope and south-eastern aspect was chosen as the experimental site to represent the dieback phenomenon in Zagros forests. The experiment was a randomized complete block design with four treatments and three replications. The experiment was conducted as a randomized complete block design with four treatments including crescent shaped bund with preservation (CSB+P), preservation treatment (PT), crescent shaped bund without preservation (CSB-P) and control treatment (CT). CSB+P was constructed to assist reduction in dieback rate and even re-vegetation of some dried forest trees through its effects on harvesting runoff. This technique is perpendicularly in the slope direction with the opening perpendicular to the flow of runoff, capturing runoff inside. The frequency of both dieback and healthy trees was recorded twice a year, therefore, the total number of trees was recorded before the construction of bunds within the plots using 100% inventory method. Soil quality, soil moisture and plant canopy were analyzed within treatments and repeated every year during the research period. 3. Results and Discussion Results explored that the effects of CSB+P treatment on reduction of dieback rate and re-growing of some dried trees was 36.7 and 19 tree ha-1 respectively (totally 55.7 ha-1 tree in the forest stand). Therefore, both the reduction of mortality rate and re-growing of dried trees are two main positive effects demonstrated by CSB+P measure. PT treatment has no effect on re-growing, while it contributes to the reduction of dieback severity (37.7 tree ha-1). Finally, CSB-P was found the lower level on dieback reduction was 6 tree ha-1, revealing the crucial importance of preservation for the protection of built bund. As a result, micro-catchment and preservation have a significant positive effect on forest restoration through soil moisture retention. Results also showed that the respective means SOC in the CSB+P, PT, CSP-P and CT treatments were 2.35, 2.40, 1.90 and 1.80 %, indicating no significant difference among them. However, the means significantly (p>0.05) increased in the CSB+P and P treatments over time. CSB+P significantly reduced bulk density from 1.46 (1st yr) to 1.32 (3rd yr) enhancing soil moisture content. The crescent shaped bund was designed as the adaptive micro-catchment runoff harvesting system (MCRHS) and measured within treatments plots. This technique has a lower soil and embankment movement than earthy or stone dams which can be built perpendicularly in the flow of runoff. Besides, it is arranged in staggered rows along the natural contour of the land with the open end facing uphill. Consequently, these bunds slow down runoff enabling the harvested water to be used in an effective way. This is particularly useful in increasing the soil moisture, especially when precipitation is scarce. 4. Conclusion It is concluded that CSB+P (first treatment) can be considered as the possible adaptation approach for combating Zagros forest mortality induced by drought stress and climate change. This technique is a possible measure for runoff harvesting and thereby enhancement of soil moisture during dry season. However, proper and holistic management of forests are needed to curtail forest dieback event. Furthermore, Zagros forest soil should be protected from disturbance factors in terms of tillage practice, machinery traffic, grazing, logging and charcoal extraction. In our experience, runoff harvesting through micro-catchment technique, forest preservation and sustaining SOC are crucial short term measures for combating forest mortality in Zagros regions
