Species Richness, Evenness and Plant Community Stability 22 Years after Ploughing a Semiarid Rangeland
Authors
Abstract
Rangeland ploughing and cultivation using dry land farming crops may be a
major reason for the destruction of natural resources in the semiarid and sub-humid regions
which may significantly change the composition and reduce the stability of the affected
communities. In present research, an abandoned ploughed site was compared with a nearby
reference site in the semiarid rangelands of Baharkish, Quchan, Iran in spring and summer
of 2010. Frequency and canopy cover of all plant species were recorded within 40
quadrates of 1m2 area. Simpson, Shannon-Weiner, Hill and Macintosh indices for
biodiversity, Margalof and Menhening for richness and Camargo, Simpson, Modified Nee,
Smith and Wilson for evenness were used. Floristic composition, plant life forms, and
important value of major plant species were compared with respect to the sites. Land
ploughing and subsequent abandonment had increased total number of plant species
(richness) but decreased the species heterogeneity (evenness). It resulted to non-significant
differences in species diversity between the ploughed and reference sites. Ploughing had
increased (8%) the important values of respruting plant species. Therefore, patchy
distribution of clonal plants had reduced species evenness within the abandoned site.
Furthermore, there were some increases in number of therophytes (100%) but
hemicryptophytes (24%), chamaephyte (33%) and phanerophyte (100%) species were
reduced in the abandoned site. In conclusion, lower evenness and high proportion of
annual plants should make the abandoned site more fragile and sensitive against the future
environmental fluctuations.
