Responses Of Plant Population And Community To Resdue Aqueous Extract To Main Species Of Eastern Gansu Province

This research regarded the residue aqueous extract of three main species in typical rangeland on Loess Plateau: Stipa bungeana Trin., Lespedeza davurica, Artemisi Capillaris. According to the multi-year measured value of litter under different grazing intensities and the local multi-year average precipitation and deviation of extraction, the concentration of residue is classified into 4 classes: 0, 2.5%, 5.0% and 10.0%. Through field potted experiment, population experiment and community experiment, this research studied the effect that the residue aqueous extract had on the seedlings growth of Stipa bungeana Trin, Lespedeza davurica, Artemisia. Capillaris ,on the height, tiller, density, seedling number of main species and on the height, tiller, coverage, seedling number and litter biomass. Main achievements are as follows:1.The effect on the seedlings growthAqueous extract of bunge needlegrass restrained the height of dahurian bushclover. (P<0.05), promoted the height of alfalfa and wheat(P<0.05). It also promoted the alfalfa shoot and entire seeding dry weight when it was under 2.5% and 10.0% concentration(P <0.05). It had no obvious effects on the seedling emergence of dahurian and alfalfa, and on the seedling emergence and height of wheat(P>0.05).Aqueous extract of Dahurian bushclover promoted the seedling emergence and restrained the height of itself (P<0.05), promoted the seedling emergence of alfalfa(P<0.05). It promoted the height of alfalfa at the concentration of 2.5% and 5.0%, and restrained the height of alfalfa at 10.0%, which showed as a convex parabolic on concentration gradient. It had no obvious effects on the dry weight of alfalfa(P<0.05), on the seedling emergence, height, dry weight of itself at 5.0% and 10.0%.Aqueous extract of Artemisia. Capillaris showed positive effect at the concentration of 2.5% and inhibitory effect at 5.0% and 10.0% on the seedling emergence and height of alfalfa; the aqueous extract at different concentration reduced the seedlings height(P<0.05). It decreased the shoot dry height of dahurian bushclover (P<0.05) at 5.0%, promoted the shoot dry height and restrained the root dry weight of alfalfa at 2.5% and restrained the shoot dry weight at 5%. It promoted the growth of wheat root at the low concentration of 5.0%, however, it had no obvious effects on the seedlings height of wheat, the seedling emergence and height of dahurian bushclover and the seedling emergence of wheat.2.The effect on the plant populationResults showed that aqueous extract of bunge needlegrass restrained the height (P<0.05) of itself without obvious alterations between different concentrations, had no obvious effect on the height of Dahurian bushclover and Artemisia. Capillaris (P>0.05). The effect on the tiller of itself decreased. The promoting effect on the tiller of dahurian bushclover increased as the concentration of aqueous extract increased (P<0.05) until aqueous extract is at the certain concentration. The tiller of Artemisia. Capillaris increased at first and decreased later at the concentration gradient, which showed as a convex parabolic(P>0.05). The plant density of itself and Dahurian bushclover increased at first and decreased later at the concentration gradient, which also showed as a convex parabolic(P>0.05). The plant density of Artemisia. Capillaris increased(P<0.05)until the concentration is at more than 5.0%.Aqueous extrac of dahurian bushclover showed negative effect on the height of bunge needlegrass(P<0.05) and had no obvious promoting effect on the height of itself and inhibitory effect on the height of Artemisia.Capillaris(P>0.05). It had inhibitory effect on the tiller of Artemisia. Capillaris, which increased as the concentration of aqueous extract increased(P<0.05), It had no obvious effect on the tiller of itself and bunge needlegrass(P>0.05). The aqueous extract showed promoting effect on the density of three plants(P<0.05). The effect on bunge needlegrass didn't alter at different concentrations; the density of itself strengthened as the concentration increased. However, the density of Artemisia. Capillaris increased at first and decreased later at the concentration gradient, which showed as a convex parabolic (P>0.05).Aqueous extract from capillary wornlwood restrained the height of bunge needlegrass(P<0.05), promoted the height of dahurian bushclover, which weakened as the concentration decreased. The aqueous extract had no obvious effect on the tiller on the dahurian bushclover (P>0.05) and restrained the tiller on the itself (P<0.05)with weakening effect as the concentration increased. The aqueous extract showed the promoting effect on the plant density of three plants(P<0.05). The promoting effect on the itself and bunge needlegrass showed as a convex parabolic (P<0.05) on the density of itself and dahurian bushclover, and the promoting effect on the density of dahurian bushclover strengthened as the concentration increased.3.The effect on the Plant communityIn communities, the aqueous extract of Bunge needlegrass showed the promoting effect on the height of Bifurcate ginquefoil (P<0.05), which strengthened as the concentration increased. The aqueous extract at the concentration of 10.0% had promoting effect on the height of Amblytropis (P<0.05), had no obvious effect on the height of capillary wornlwood (P>0.05). However, the inhibitory effect strengthened as the concentration increased. The tiller of dahurian bushclover and capillary wornlwood increased at first and decreased later at concentration gradient, showing as a convex parabolic (P<0.05). The aqueous extract restrained the tiller of the Artemisia frigid and Bunge needlegrass (P<0.05), which had no obvious effect on the coverage of dahurian bushclover and capillary wornlwood, decreased the coverage of Potentilla bifurca and promoted the coverage of the Artemisia frigid with the increasing effect as the concentration increased. The aggregative index showed that, the most sensitive plant to the aqueous extract of Bunge needlegrass is Potentilla bifurca, the order of sensitive index is coverage>height>tiller, and the most sensitive concentration is 10.0%.Aqueous extract of dahurian bushclover restrained the height of itself (P<0.05) and the effect strengthened as the concentration increased. It had no obvious effect on the height of the capillary wornlwood and Agriophyllum arenarium (P>0.05) and had inhibitory effect on the Bifurcate ginquefoil (P<0.05) without obvious alteration between concentrations. The aqueous extract restrained (P<0.05) the tiller of the capillary wornlwood and Thermopsis lanceolate with increasing effect as the concentration increased. It had no obvious effect on the tiller of the Bunge needlegrass and Potentilla bifurca (P>0.05) and decreased the coverage of itself and Artemisia frigida (P<0.05). The inhibitory effect on the coverage of itself strengthened until the concentration was up to the certain one. The most incentive plant to the aqueous extract from dahurian bushclover was Artemisia frigid, and the most sensitive concentration is 5.0%.Under the condition of aqueous extract from capillary wornlwood, the effect on the height of dahurian bushclover and Potentilla bifurca increased at first and decrease later (.P<0.05), showing as a convex parabolic. The aqueous extract showed promting effect on the height of Agriophyllum squarrosum (P<0.05) and no obvious effect on the height of Thermopsis lanceolate (P>0.05). It promoted the tiller of itself (P<0.05)without obvious alteration between concentrations and had no obvious effect on the tiller of Thermopsis lanceolate, Potentilla bifurca and Agriophyllum squarrosum (P>0.05). The effect on the coverage of Artemisia frigid and dahurian bushclover showed as a convex parabolic on the concentration gradient (P<0.05) but there was no obvious effect on the coverage of capillary wornlwood and Potentilla bifurca (P<0.05). The sensitive plant order for aqueous extract of capillary wornlwood is Potentilla bifurca> dahurian bushclover and capillary wornlwood, the order of incentive index is coverage>height>tiller, the most incentive concentration is 10.0%.Up to all three Aqueous extracts, the sensitive plant order was Bifurcate ginquefoil> dahurian bushclover >capillary wornlwood. The order of effect was the aqueous extract of dahurian bushclover> the one of capillary wornlwood> the one of Bunge needlegrass. The index was coverage and the order for the effective concentration is 5.0%>10.0%>2.5%.The aqueous extract of Bunge needlegrass restrained the richness of species which strengthened as the concentration increased and had no obvious effect on the diversity; Aqueous extract of dahurian bushclover promoted at first, restrained later the richness of species showing as a convex parabolic. It restrained the diversity of species, and the effect strengthened as the concentration increased; Aqueous extract of capillary wornlwood had no obvious effect on the richness and diversity of species.These three aqueous extracts would decrease the Richness, Diversity, and Pielou index of the seed bank of sheep-rotation pasture, the restraining effect was bunge needlegrass>capillary wornlwood>dahurian bushclover. Under the condition that aqueous extract is from bunge needlegrass or capillary wornlwood, the similarity indext between mediate grassing intensity and high grassing intensity was alike. When the aqueous extract was from dahurian bushclover, similarity index of no grazing and heavy grazing intensity was alike.