جستجوی مقالات مرتبط با کلیدواژه "management plan" در نشریات گروه "آب و خاک"

Erosion, sediment yield (SY) as well as rainfall erosivity and vegetation cover show seasonality during a year. Basically, most SY occurs during high erosivity and poor soil cover periods. Therefore, in selecting crop and vegetation management programs at the basin level, it is necessary to underestand the temporal changes of erosivity and SY.

Two watersheds, Kasilian in Northern Alborz and Latyan in Southern Alborz were selected and their landuse maps were extracted. Then, spatiotemporal variations of NDVI for three hydrological years including dry, normal and wet years, were derived bimonthly form MODIS data. For estimating suspended sediment, we used a combination sediment rating curve and average daily discharge records. Erosivity factor, EI30, was calculated in the nearest gauging sites for both basins based on 1-minute interval rain records. Simultaneous to the NDVI, suspended SY and rainfall erosivity were computed. Then, based on the correlation of SY with erosivity and vegetation, the relationship was analyzed and finally, the appropriate time of exploitation for forests, rangelands and suitable crops with best ground cover during the erosion risk peaks was proposed.

In Kasilian, four main landuses were forest (97%), orchards, croplands and rangeland, and in Latyan, two landuses of rangeland (94%) and orchards were dominat. The average NDVI of Kasilian and Latyan was 0.67 was 0.13 respectively. However, the NDVI of similar landuses was measured to be about half and less in Latyan than Kasilian. For all landuses, NDVI reaches its lowest value in the colder months. Erosivity did not indicate a clear seasonal cycle, possibly due to occurring erosive storms even during the dry periods. The peaks of the SY did not occur at the same period of time in the studied years in Kasilian basin; while, for Latyan basin, the peaks were concurrent with snow melting and percipitation in the beginning of spring in all three years. In studied dry, normal and wet years, high negative correlations (-0.54, -0.45 and -0.85 respectively) were found between the NDVIs and SYs in Kasilian basin. In contrast, no significant correlation was observed between the two aforementioned factors in the studied years of Latyan basin. There was also no correlation between erosivities and basin SYs. Finally, according to the SY cycle, June and July were proposed as the best time for grazing of rangelands and exploiting the forests in Kasilian basin, and early June to September were proposed in the Latyan basin to minimize the risk of erosion. Due to the high sediment production in the Latyan basin, the number of livestock entering the area and the capacity of the grazing should be more closely monitored. From the point of view of erosion risk, summer Soybeans, Canola and Wheat and Barley, were introduced as suitable and spring Soybeans as unsuitable crops for Kasilian based on to their growth stages.

For soil conservation and management and sediment yield prevention, it is essential agricultural products and the time of exploitation of rangelands and forests be planned and managed based on the erosivity and sediment yield cycles in a way to limit soil erosion.

Desertification is one of the greatest environmental challenges at the present time. The aim of this research، the presentation of desertification management plan is based on desertification risk map. Once produced، the work-unit map (geomorphological facies) of Sabzevar،a scoring process in each unit according to the MICD model and the desertification hazard map was done. The risk number was defined for each work-unit by multiplying desertification hazard classes to elements at risk and vulnerability of the elements at risk which obtained risk classes by classification of risk number. Then، management strategies and schedules were defined on the basis of the risk classes، field’s characteristics and important desertification indices in each work unit. These strategies introduced in the frame of 4 strategy and 10 desertification management plans and prepared the map of desertification management plan for Sabzevar. The results showed that: The largest share of the area (i. e. 37. 44%) and the smallest (i. e. 0. 08%) were devoted to the classes of IIb and IIIc respectively. The IIb class covered mostly clay pans، alluvial fans and also enclosed a large proportion of the Erg-e-Khartouran sand dunes. The effective indices in desertification of the IIb class were effective vegetation cover in soil and soil’s pressure resistance in arid conditions in the rangeland category and were soil surface traces of wind abrasion and sand accumulation in the areas of lack of land-use. According to the effective desertification indices in the area for the IIb class، it was proposed a managerial plan such as planting shrubs، revitalizing the vegetation stand and establishing wind breaks.