| The edge effect and biodiversity of grasshoppers' communities were investigated and studied among seven types of edge zones and their adjacent communities in southern slope of Qinling Mountain: crop fieldroad edge zone, crop field-wasteland edge zone, wasteland-track edge zone, tall herbosa-track/road edge zone, tall herbosa-forest edge zone, sparse forest-crop field edge zone, river shoal-road edge zone. These edges were studied using 2X5m sample plots that formed at least lOOm linear transects perpendicular to the edges. All eighteen species of grasshopper (Orthoptera:Acridoidea) collected in the studied areas were classified as fifteen genus and five families, which composes two thirds of the total number of species of grasshoppers in the southern side of Qinling Mountain. Among them, the quantity of Catantopidae is the most while that of Acrididae is the fewest. The grasshoppers' diversities are higher than those in the interior of adjacent communities at the similar edges at different sea levels. But the order sequences of diversity of grasshoppers' communities on different edges co-existing at the same elevation are changeable and no regulation when compared among different elevations. On the whole, the diversity of grasshoppers' communities on mixed edges are higher than those of on non-mixed edges. Furthermore, wasteland-track edge zones possess the highest diversity among all non-mixed edge zones. With the ascending of elevation, the dominant species in different communities change accordingly, which is closely correlated with the tolerance of grasshoppers to natural environment. Comparison with the edge effect in different exposures any aspect, the intensity of edge effect on positive edge is stronger than that of on the negative edge. In order to make the results more cogent and precise, statistical method non-paired-t-test was introduced to detect the existence of edge effect. Results indicate that the differences of biodiversity index(H') are statistically significant, which demonstrates that positive edge effect can be detectable in grasshoppers' communities and is objective . Two formulas measuring the intensity of edge effect from the quantity of population and structure ofcommunity were used in analysis. They respectively are: EH. mH'/Z H,., E~= mC/3 C~. Through calculations, the characteristics of all kinds of edges can be decided by comprising the values of EH. with threshold value I. If the value of E~. is bigger than 1, then the edge effect is positive, vice verse. Similarly, the value of Ec can also be used to quantify edge effect. The different edge responses of various grasshoppers were discussed at the level of species and family separately. Analyses based on the level of species reveal that different species respond to the identical edge differently due to individual difference:Acrida cinerea Thunberg and Atractornorpha sinensis I. Bol. are habitat generalist edge exploiter, chorthippus chinensis Tarb., Thilophidia annulata (Thunberg), Oxya hyla intricata (Stal) and Oxya chinesis (Thunberg) can be classified as habitat specialist; Shirakiacris shirakii (I. Bol.) can be identified as habitat specialist edge exploiter, Oedaleus infernalis Saussure Chang as well Celes skalozubovi Adelung can be regarded as habitat specialist edge avoider; Patanga japonica (I. Bol.) can be considered as habitat generalist. Such individual species responses are masked by analysis at the order level. Therefore, it is necessary to identify organisms to species or subspecies level so as to determine whether edge effect exists or not . Among all transects, only 45.44 per cent (less than 50 per cent ) correlation coefficients between the abundance of grasshopper and the distance from edges are statistically negatively significant (P < 0.05), the rest are negatively medium correlation.The existence of negative correlation indicates that the number of individuals of grasshoppers decrease with the increase of distances from edges. But the... |
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