Background:
Despite the importance of arthropods in grassland ecosystems, few
studies have examined how grassland arthropods have been impacted by
disturbances in the Wadi Afara in the West Bank Objectives: 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'
area in the Palestinian West Bank. Methodology: 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. Within this area, three sites
(2000m² each) with similar topographic and edaphic features were
selected to study the effect of land use management practices on
arthropods diversity including species composition, species richness and
species diversity:
one site was previously a part of a grassland suffering from grazing by
mainly sheep and goats herds. In October 2005 the land was fenced and
protected from any agricultural practices or grazing; a second site was
under grazing for the last 25 years, and the third site was undisturbed
natural grassland where no human activities, agricultural practices or
grazing had taken place for the last 5 years.
Terrestrial arthropod communities were sampled seasonally at the three
sites using pitfall traps, over the period of Apr 2006 to Apr 2007. One
year of collections at comparison sites were used to quantify the
seasonal variation of arthropod species and these parameters were
correlated with climatic and edaphic conditions. Results and
discussion: 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 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. Conclusion: Grazing has a
considerable impact on the biodiversity of grassland arthropods in
Alfara’ area. Some of the insect components, especially Carbus
impresses, of the family Carabidae (order Coleoptera) are well adapted
to grazing disturbance, and therefore can be used as bio indicators of
habitat disturbance such as grazing.