An-Najah Staff

Despite the importance of arthropods in grassland ecosystems, few studies have examined how grassland arthropods have been impacted by disturbances especially in the Wadi Alfara’a area, West Bank. This work was aimed at studying the effects of animal grazing on arthropod diversity, including species composition, species richness and species diversity, in a semi-arid Mediterranean grassland ecosystem at Alfara'a area in the Palestinian West Bank. The field work was conducted at the Tallouza village, located in the north-eastern part of the West-Bank. The experiment was established in 2006 in an area of about 2000 donums of a mainly grassland ecosystem usually used for grazing sheep and goats herds, under different land use management systems: recently fenced grassland, undisturbed natural grassland, and recently reclaimed agricultural land. Terrestrial arthropod communities were sampled seasonally at the three sites using pitfall traps, over the period of Apr 2006 to Apr 2007. Arthropods communities were found to be sensitive to livestock grazing. Overall population levels of arthropods were highest in the undisturbed natural grassland, followed by grazed grasslands, and the recently fenced grassland. Certain insect orders (Coleoptera and Hymenoptera) were generally, negatively impacted by livestock grazing. However, members of the family (Carabidea, ground beetles) (order Coleoptera) especially Carabus impressus, were richer in grazed sites. On the other hand families of Hymenoptera like (Sphegidae, Cephidea and Apiddae) were not detected in the grazed grassland. On the other hand the unidentified species (Form 5) of the family (Formicidae) found only in the grazed grassland. A significant seasonal variation pattern was detected for total arthropod populations (P<0.05) at the different study sites, with the highest population levels detected in summer and early autumn, and lowest population levels detected in  winter. The fluctuation patterns were comparable in the three sites. Comparable fluctuation patterns were also found for Hymenoptera and Coleoptera.  Higher arthropod population levels in summer months coincided with higher air temperatures and lower soil moisture content, whereas, lower arthropod population levels in winter, coincided with lower temperatures and higher soil moisture content. Grazing has a considerable impact on the biodiversity of grassland arthropods in Alfara’a area. Some of the insect components, especially Carbus impressus, are well adapted to grazing disturbance, and therefore can be used as bioindicators of habitat disturbance such as grazing. 

 This study was carried out in Tallouza village which located in Wadi El-Far’a area in the West Bank in  order to study the effect of grazing and land reclamation on natural vegetation diversity during two growing seasons (2005-2006 and 2006-2007). Four sites of grassland ecosystem of different type of land use (reclaimed grassland, recently no-grazing grassland, under-grazing grassland, natural reserved grassland) were selected. Vegetation and soil sampling were carried out in mid April for each growing season, data about amount and distribution of rainfall and temperature were collected for the area during the two growing seasons. Vegetation sampling and above ground biomasses were determined by using quadrate method. Braun-Blanquet scale was used to visually estimate the relative vegetation cover of each species. The study showed that vegetation composition and percent vegetation cover differ between the sites. Percent vegetation cover was significantly increased in recently no-grazing grassland when  compared it with under-grazing grassland and the highest percent vegetation cover was in the natural  reserved grassland, and this was indicator for the high potential of this grassland for the rehabilitation in few years when we exclude grazing. Species diversity, evenness, above ground biomass and density were significantly higher in the recently no-grazing grassland and natural reserved grassland than undergrazing  grassland. Agricultural activities, especially ploughing were justifying the low natural species diversity evenness, above ground biomass and density in reclaimed grassland. Species found in undergrazing  grassland were mostly low palatable to grazing animals, mostly small, prostrate or rosette plants while in natural reserve grassland mostly palatable to grazing animals, mostly tall and erect plants. The vegetation cover observed in mid April 2007 was higher than mid April 2006 at natural reserve grassland and recently no-grazing grassland were due to the differences in distribution of precipitation in the two growing seasons and grazing exclusion. There was no significant difference between the sites in the edaphic factors, so we didn’t know the effect of these factors on natural vegetation diversity in the area.