Effects Of Slope Aspect On Community Characteristics In The Process Of Degradation Of Cold-season Slope Protective Turf

In order to solve the practical problems of slope direction leading to the slope lawn degenerating and life expectancy shortening in the transitional climatic zones,In the paper,the man-made slope lawn,built on the mountain road of three slopes was a research object.Three slope directions were A slope EN 40 °,B slope WS 33 ° and C Slope WN 29.°,respectively.After two years of completion,height,density,coverage and biomass of dominant species,species and diversity of community were determinated.The determination time includes autumn(December 2015,October,November),winter(December 2015,January 2016,February 2016),spring(March2016,April,May)and summer(2016,July,August).After three year of completion(November 2016),lawn quality and slope protection effect were evaluated.The effects of slope direction on quantitative characteristics of Arthraxon hispidus and tall fescue,characteristics of lawn community,quality of slope protection lawn and effect of slope protection were analyzed,and the response mechanism of dominant species and community to slope direction also was studied.The purpose was provides a theoretical reference for species selection and conservation management of slope protection lawn.The main findings are as follows:(1)Effects of slope orientation on quantitative characteristics of A.hispidus and tall fescueThe slope direction had significant effects on height of A.hispidus in four seasons(p<0.05).In autumn,height of A.hispidus on the A slope was significantly higher than that of C slope.In winter,spring and summer,height of A.hispidus on the A slope and B slope were significantly higher than that of C slope.Height of A.hispidus on the same slope existed a significant difference on in different seasons(p<0.05).The slope direction had significant effects on density of A.hispidus in winter,spring and summer(p<0.05).In two seasons of winter and spring,the density of A.hispidus in the order for slope direction was B slope> A slope> C slope.The slope direction had significant effects on coverage of A.hispidus in four seasons(p> 0.05).In four seasons,coverage of A.hispidus on the B slope was significant larger than that of A slope,and A slope wassignificant larger than that of C slope.The slope direction also had significant effects on biomass of A.hispidus in four seasons(p> 0.05).In each season,biomass of A.hispidus on the B slope all got the maximum and the minimum on the C slope.Slope direction had no significant influences on height,density and biomass of tall fescue in four seasons,expect for coverage of tall fescue in winter(p>0.05).Height and biomass of tall fescue on the same slope also didn't existed significant difference in four seasons(p>0.05).Plant height got the maximum on the B slope in four seasons.Density,coverage and biomass of tall fescue on three slopes all decreased with the time prolonging.In winter,the coverage of tall fescue on the B slope was significantly larger than that on the A and C slope..(2)Effects of slope orientation on characteristics of plant community.In four seasons,the community on the slope was dominated by Gramineae,Compositae and Leguminosae.There were 15 species on the A slope,belonging to 5families,including 5 species of Gramineae,5 species of Compositae,3 species of legume,1 speices of Umbelliferae and 1 species of Verbenaceae.There are 16 species on the B slope,belonging to 9 families,including 5 species of Gramineae,3 species of Compositae,2 species of Leguminosae,each one species for Garciniaceae,Verbenaceae,Rosaceae,Umbelliferae,Kidney Branch and Grape.In addition,13 species on the B slope were found,belonging to 6 families,including 5 species of Gramineae,4 species of Compositae,each one species for Umbelliferae,Grape,Leguminosae and Rosaceae.The plants on three slopes were mostly Gramineae.Two years after planting,the lawn community evolved into A.hispidus as the dominant species and tall fescue was a new community of eugenic species.The important values of A.hispidus on three slopes in winter were lower than those in autumn,and increased gradually in spring and summer.In summe,the important values of A.hispidus on the three slopes all achieved the maximum,with the values of 34.50,37.26 and 21.65 for A slope,B slope and C slope,respectively.With the time prolonging,the important values of tall fescue on the A slope gradually increased,and that on two slopes of B and C first increased and then decreased.in which the overall trend was decreased.The important value of A and B slope was less than of thatC slope in threeseasons..(3)Effects of slope orientation on diversityIn autumn,the slope orientation had significant influences on shimpson dominance index(D)(p<0.0),but no significant effects on Shannon-wiener diversity index(H)Pielou evenness index(J),and abundance index(DM)(p> 0.05).For the D value,the B slope was significant bigger than the A and C slope,and A slope was slightly larger than C slope.For the J value,A slope significantly greater than B slope,and the order of slope direction was B slope > C slope > A slope.In the following autumn,the slope only had a larger effect on the dominance of community,but a small influence on evenness,abundance and diversity.In winter,the slope orientation had significant effects on the Pielou evenness index(J)and Shannon-wiener diversity index(H)(p <0.01),and no significant effects on the abundance index(DM)and shimpson dominance index(D)(p> 0.05).The H value on the B slope was significantly lower than others.The J value existed significant difference among three slopes,and the order was C slope > A slope > B slope.With the time prolonging,the impact of slope direction on development of community gradually enchanced.In spring,the slope orientation had significant effects on shimpson dominance index(D)(p<0.05),but no significant effect on Shannon-wiener diversity index(H),Pielou evenness index(J)and abundance index(DM)(p>0.05).For the D value,A and B slope were significantly bigger than C slope.For the H value,C slope was significantly bigger than B slope.The Dm and J value was the smallest on the B slope.But they all didn't exist significantly difference among three slopes.In summer,the slope orientation had no significant effect on abundance index(DM)and Shannon-wiener diversity index(H)(p > 0.05),but a significant effect on Shimpson dominance index(D)(p<0.05)and a highly significant effect on Pielou evenness index(J)(P <0.01).For the D value,A and B slope were significantly bigger than C slope.For the J value,C slope was significantly bigger than B slope,and B slope was significant bigger than A slope.The Dm and H value both was the smallest on the A slope.But they all didn't exist significantly difference among three slopes.(4)Effects of slope orientation on the quality of slope lawnIn this study,lawn quality for the good level was only A5 and B3,for middle level was only A4 and C1,and the rest were poor or inferior.The quality of lawns varied greatly,and the quality of lawns in different aspect was also different.Lawn quality score on the A slope was the highest,with the values of 15.8,in which lawn quality rating was middle level.Lawn quality score on the B slope and C slope were 12.4 and12,respectively,and lawn quality rating was poor.Thus,lawn quality on three slopes was overall not good,and the quality order was as follows: A slope > B slope > C slope.(5)Effects of slope orientation on protection effectThe slope direction only had significant effects on the number of small groove and soil loss(p <0.05),and no significant effects on the length,width and depth of small groove on the slope(p> 0.05).The small groove number and soil loss on the C slope were significant higher than the others,with the value of 10.6 and 17.9kg.And the two measures on the A slope significant lower than the others.The effect order of slope orientation to small groove was: amount of soil loss > number of small grooves> width of small groove> length of small groove> depth of small groove.3 years after slope lawn being construced,plant species on the A slope,B slope and C slope plants all were dominated by A.hispidus and tall fescue,in which total community coverage were84.3%,71.6% and 68.1% respectively.The order of protection effect was A slope > B slope > C slope.