| Aiming at the current important problems in herbaceous plant for slope protection,for example,the variety is unitary,the ecological adaptability is bad and so on,this research took exploitation of abundant wild plants resources in our country as the starting point,took wild Pennisetum alopecuroides[Pennisetum alopecuroides(L.) Spreng],which is widespread in Hunan province and has strong adaptability,as the object of study,and took Cynodon dactylon[Cynodon dactylon(L.) Pers],which is usually used in slope protection,as the contrast.Wild Pennisetum alopecuroides was systemly researched for the first time on the hydrological and ecological effect of stems and leaves,the mechanical effect of roots system and the drought resistance.In order to provide scientific theory basis for making use of this wild plant in ecological engineering practices,such as slope protection,vegetation recovering and so on.The main research results are as follows:1.The hydrological and ecological effect of stems and leaves of wild Pennisetum alopecuroides was overally better than Cynodon dactylon's.The Formation time was 49d,the max.grass height was 117.14cm;after growth for more than 4 months,the fresh weight of stems and leaves was 112.93t/hm2,the dry weight was 32.99t/hm2,the max.interception rate and amount of stems and leaves were 45.35%and 5.12mm;wild Pennisetum alopecuroides was evidently better than Cynodon dactylon in these aspects.After growth for more than 4 months,the effective retaining-water rate of litter layer was 304.88%and less than Cynodon dactylon,but both of the effective retaining-water amounts were very low.Stems and leaves of wild Pennisetum alopecuroides can reduce ground temperature and maintain soil water more evidently and effectivly than Cynodon dactylon's.2.The mechanical effect of roots system of wild Pennisetum alopecuroides was evidently stronger than Cynodon dactylon's.After growth for 5 months,the deepest root was more than 49.42cm,the average roots diameter was 1.05mm,the roots weight was 7.72g/100cm2 in 0～50cm soil,the average roots max.tensile stress was 23.0N,the average roots tensile strength was 40.18MPa,the effective roots density was 54/100cm2,the soil Anti-scouribility coefficient was 159.76L·s/g,the roots effect on reducing sand was 0.83,wild Pennisetum alopecuroides was evidently more than Cynodon dactylon in these aspects.The roots max. tensile stress and tensile strength of wild Pennisetum alopecuroides were greater than Cynodon dactylon's with the same diameter;the relation between roots max.tensile stress and roots diameter was linear and positive,the formula was Fr=26.56D-1.5225(R2=0.9805); the relation between roots tensile strength and roots diameter was linear and negative,the formula was Tr=31.657D-0.9227(R2=0.9672).Roots of two grasses evidently increased the max.shear stress and the max.shear displacement of soil,the soil shear strength of wild Pennisetum alopecuroides was evidently greater than Cynodon dactylon's under the same vertical stress;the soil shear strength and the roots strengthening value of wild Pennisetum alopecuroides,which were far more than Cynodon dactylon's,were 82.152kPa and 56.758kPa in natural conditions(the vertical stress was 10kPa);the Coulomb formula for soil shear strength of wild Pennisetum alopecuroides wasτf=σ·tan26.27°+77.216,φ=26.27°,c =77.216kPa;Roots of two grasses strengthened soil shear strength mainly because they increased the soil cohesion.3.The drought resistance of wild Pennisetum alopecuroides was stronger than Cynodon dactylon's.Compared with Cynodon dactylon,the leaves relative conductivity of wild Pennisetum alopecuroides was increased less,the plasma membrane was stabler;the leaves MDA content was accumulated less,the peroxidation resistance of membrane and fat was stronger;the Chlorophyl content was decreased less,the Chlorophyl dissolution resistance was stronger;the leaves Pro content was accumulated more slowly,the peak value of leaves Pro content,which appeared later,was higher,the leaves soluble sugar content was higher, and increasing range was greater,the osmotic adjustment of Pro and soluble sugar in wild Pennisetum alopecuroides was more lasting and effective. |
