Analysis of mutual benefit and damage of interspecific association of plant species in sandy area in Yulin, Shaanxi of western China.

Interspecific association of plant species could bring mutual benefits to them. There are several forms of association, such as noncontact, parasitism, interspecific rejection and sometimes lethal damages to opponents, and as a result, community succession could be formed. A clear understanding of interspecific relationship of plants in drought, barren sandy area with very narrow niche breadth is important to build stable community of sand-fixing plant species, and improve sand-fixing benefits. In this study, we calculated probability of plant species association in the sandy area in Yulin, Shaanxi Province with a 2×2 contingency table, which could accurately explain the relationship between plant species. Results showed that the probability of association of main sand-fixing plants was smaller than 0.05 in this area. The low coefficient of association implies that plant species there have no connected growth, and they mainly grow independently. Negative coefficient of association indicates that plant species exclude each other instead of associating. Yulin sandy area is a semiarid desert, short of water and nutrients that plants need to survive, especially for those with similar ecological habit of same genera and same families. In order to survive, these plants compete for the very limited nutrients and thus the poor competitors are always eliminated. Therefore, in the drought area, survival of plants is restricted by narrow niche breadth, very hard to bear connected growth of many species. Our main experience of sand control in Yulin is to follow and adapt to the nature, instead of violating it.