| This study was carried on the exclosed typical steppe of the eastern Gansu,Loess Plateau,in order to identify litter decomposition and soil respiration under different terrain,quantify the impact intensity of terrain,litter quality to litter decomposition,and the role of litter decomposition in the recovery of degraded glassland.1Litter biomass decompositionThe annual decomposition of litter in exclosed typical steppe was45-sunny slope>15-top slope>30-top slope>30-shady slope>30-sunny slope>15-sunny slope>45-top slope>15-shady slope>45-shady slope;respectively,the daily average decomposition rate were0.177%,0.134%,0.132%,0.131%,0.130%,0.129%,0.126%,0.118%,0.115%;respectively,the annual return of litter fall were28.01g/m2,25.91g/m2,17.56g/m2,12.11g/m2,16.38g/m2,21.80g/m2,17.91g/m2,30.49g/m2,19.45g/m2.The impact intensity of various factors on litter decomposition:direct influence was soil temperature (-0.402)>initial concentration of N (-0.305)>soil moisture (0.213)> initial concentration of C (-0.175)> initial concentration of P (-0.134);indirect influence was season (-0.597)> slope gradient (0.115)>aspect (0.087)2Decomposition of litter CThe annual decomposition of litte C in typical grassland was45-sunny slope>30-top slope>30-shady slope>15-suuny slope>15-top slope>30-sunny slope>45-top slope>15-shady slope>45-shady slope;respectively,the daily average decomposition rate of litter C were0.174%,0.145%,0.141%,0.139%,0.134%,0.132%,0.122%,0.113%,0.105%;respectively,the annual decomposition amount of litter C were20.90g/m2,15.60g/m2,10.65g/m2,18.32g/m2,19.71g/m2,13.30g/m2,13.05g/m2,22.48g/m2,12.99g/m2.The impact intensity of various factors on decomposition of litter C:direct influence was soil moisture (0.876)> initial concentration of C (0.121)>soil temperature (0.101);indirect influence was season (-0.716)> slope gradient (0.130)> aspect (0.040)3Decomposition of litter NThe annual decomposition of litte N in grassland was45-sunny slope>30-sunny slope>30-top slope>15-sunny slope>15-top slope>30-shady slope>45-top slope>45-shady slope>15-shady slope;respectively,the daily average decomposition rate of litter N were0.195%,0.175%,0.168%,0.165%,0.164%,0.161%,0.159%,0.151%,0.147%;respectively,the annual decomposition amount of litter N were0.21g/m2,0.17g/m2,0.16g/m2,0.25g/m2,0.28g/m2,0.12g/m2,0.18g/m2,0.22g/m2,0.33g/m2.The impact intensity of various factors on decomposition of litter N:direct influence was soil temperature (0.889)>soil moisture (0.019)>initial concentration of N (0.015);indirect influence was season (0.863)>aspect (0.091)>slope gradient (-0.024)4Return of litter PThe annual return of litte P in exclosed steppe was45-sunny slope>45-top slope>45-shady slope>30-sunny slope>30-top slope>30-shady slope>15-top slope>15-sunny slope>15-shady slope;respectively,the daily average return rate of litter P were0.208%,0.205%,0.181%,0.178%,0.140%,0.0806%,0.0299%,0.0135%,0.0108%;respectively,the annual return amount of litter P were19.05mg/m2,24.78mg/m2,27.42mg/m2,15.73mg/m2,9.06mg/m2,2.87mg/m2,1.61mg/m2,0.55mg/m2,0.96mg/m2.The impact intensity of various factors on return of litter P:direct influence was initial concentration of P (0.625)>soil temperature (-0.126)>soil moisture (0.018);indirect influence was slope gradient (0.440)>aspect (-0.163)>season (-0.141)5StoichiometryC/N ratio increased first,and then decreased later with litter decomposition;N/P ratio decreased first,then increased later;C/P ratio increased first then decreased later on30-sunny slope and45-sunny slope,increased consistently on45-shady slope and45-top slope,and decreased first then increased later in other plots with litter decomposition.6Soil respirationSoil respiration rate was Sept.>Apr.>Dec.;soil respiration rate among plots under different terrain had very significant difference (P<0.01).The impact intensity of various factors on soil respiration:direct effect was soil temperature (1.168)>soil moisture (0.598);indirect effect was season (-0.380)>aspect (0.125)>slope gradient (0.070).There was a significant negtive correlation between litter decomposition rate and soil respiration (P<0.05)The faster decomposition,the poorer surface cover;the slower decomposition,the slower speed of material cycle and energy flow.Reasonable litter fall and decomposition rate need to be concerned in the management of exclosed steppe. |
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