Responses Of Plant Growth To Residue Aqueous Extract Of Dominant Species On Rangeland Of Loess Plateau In Eastern Gansu

Standing dead and litter(residue)is the midst form between matter and energy,and have significance influence on individual growth,population renewal and community succession.The grassland residue's form and disappear process are difference from forest system and crop system,it is one of the most sensitive index to grazing,fenced,fire,assart et al.Anciently,the research almost focus on the biomass and itself,haven't pay more attention to its ecology function.The grassland account for 1/3 area of Loess Plateau,it is the key parts of crop/grassland -livestock production system,to the agriculture system's succession, perfect the structure and improve the function play a key role in this area.This research from laboratory to field,from individual to system,do a research on the effect of Loess Plateau dominants species' aqueous extract on the crop/grassland -livestock production system plants' germination,seedling growth,population and community,make a analysis on residue answer to the grazing also with its ecology effect.1.The effect of plants' aqueous extract on seed germinationUse germination rate and germination speed as index.Bunge needle grass's residue aqueous extract have significant difference to the receptors,and at the concentration of 2.50%and 5.0%,it shows the promote effect to bifurcate ginquefoil,the equation shows that at the concentration of 1.94%,Bifurcate ginquefoil's germination rate can achieve 16.7%.Dahurian bushclover's aqueous extract have significant difference to receptors except wheat,and also shows the promote effect at 2.5%to itself,when at the concentratio0n of 1.98%,whose germination can achieve to 27.96%.The effect also shows with capillary wornlwood.Different residue aqueous extract have different response:bunge needle grass's residue aqueous extract made the receptors germination inhibited except the dahurian bushclover and alfalfa,but these two plants' germination speed were delayed significantly, and the germination speed is a more sensitivity index to judge this function,dahurian bushclover and capillary wornlwood's aqueous extract shows the germination inhibition effect on receptors except wheat.As a whole,the intensity of aqueous extract concentration is 10.0%＞5.0%＞2.50%;the intensity of donor plants is:capillary wornlwood＞dahurian bushclover＞bunge needle grass.Among the receptors,the most sensitive plant is capillary wornlwood,and the weakest plant is wheat.2.The influence of residue aqueous on seedling growth.Use the seedling height,dry weight of seedling,root length,and dry weight of root as index.At the same concentration the intensity of donor residue aqueous extract to seedling height is:capillary wornlwood＞bunge needle grass＞dahurian bushclover.And the intensity to dry weight of seedling is:capillary wornlwood＞bunge needle grass＞ dahurian bushclover.The aqueous have no sequence to root length,the effect on dry weight of root is:capillary wornlwood＞bunge needle grass＞dahurian bushclover.See from the receptors,the trend is as the increasing of concentration,the seedling height inhibited.And for the different receptors,the inhibition intensity of dey weight of seedling is:alflfa＞dahurian bushclover＞wheat.To the seedling height:dahurian bushclover＞wheat＞bifurcate ginquefoil＞alfalfa,to the dry weight of root,wheat＞dahurian bushclover＞alfalfa,to the root length,wheat＞alfalfa＞dahurian bushclover.3 The effect of residue aqueous to populationUnder the residue aqueous extract of bunge needle grass,only the receptors'height and growth point of dahurian bushclover and itself were declined when compared with control significantly(p＜0.05);under the solution of capillary wornlwood,dahurian bushclover's height were declined significantly and the growth point of bunge needlegrass were declined at 10.0%.The solution of capillary wornlwood has more strong effect to receptors.Also with under the solution of dahurian bushclover,capillary wornlwood's height were reduced significantly(p＜0.05),to itself only at the concentration of high level were inhibited;bunge needlegrass's growth point were inhibited at high concentration; analysis from relative height and growth point,at the concentration of 2.50%,the height of receptor populations show the trends of promotion,and if the concentration＞5.0%,all were inhibited.Among the population,dahurian bushclover is the most sensitive one,and bunge needlegrass is the weakest one.4 The effect of residue aqueous to communityThese three dominants have no significance effect on companion species' height and growth point,and among these dominant plants,the residue aqueous extract of capillary wornlwood shows the strongest function to other plants,this result correspond with germination and seedling experiments,and the influence of bundge needle grass on other dominant plants not seriously,but the common ground is have the trend of inhibiting the plant height and growth point.Anaylsis the Shannon-Wiener diversity index,under the bunge needlegrass aqueous extract,the diversity index was declined as the increase of concentration,and under the aqueous of capillary wornlwood and dahurian bushclover, when the concentration below 10.0%,the diversity index shows the same trend.5 The effect of grazing on residueThe results shows:as the increasing of grazing intensity,the quantity of residue declined.The residue biomass of 2007 in grow season or ungrown season are higher than 2006 significantly,and each grazing intensity(2.67,5.33,8.67 sheep/ha)reduced 12.9%, 16.7%,21.6%when compared with control respectively in grow season.Through the investigation,found that the three dominant plants' coverage(80%)accounts for the main proportion in the grazing land,and the bunge needle grass account for 30.7%.At the grazing intensity of 2.67sheep/ha,bunge needle grass,dahurian bushclover,capillary wornlwood's coverage were increased,that may be correlated with grazing moderately can promote regrowth of plant。When the biomass of residue at 22.1g/m~2 and 22.0g/m~2,the height of bunge needlegrass and capillary wornlwood also with the growth points of bunge needlegrass can reach the max respectively,that means if the residue can be limited in a threshold,it is befinit for the growth of plants.According to the residue's coverage, constitute and its effect on dorminate plants,we confer that the grazing intensity of 5.33sheep/ha may be is the moderate intensity in this research.The research result can understanding the grassland degeneration and restoration mechanism,develop the thchnical about grassland management,evaluating the process about "return plantation to forest/grass project",and serve scientific thereunder to control weed.