不同护坡草本植物的根系特征及对土壤渗透性的影响

为明确三峡库区植被边坡植物物种根系特征与土壤渗透性之间的关系,以裸地为对照,应用WinRHIZO(Pro.2004c)根系分析系统对香根草(Vetiveria zizanioides(Lin.) Nash)、百喜草(Paspalum notatum Flugge)、狗牙根(Cynodon dactylon (L) Pers.)和紫花苜蓿(Medicago sativa L.)等4种护坡草本的根系特征进行定量分析.结果表明:(1)紫花苜蓿和香根草的根长密度和根表面积密度显著大于狗牙根和百喜草；(2)不同草本类型和同一草本不同土层之间土壤渗透性存在较大差异,且各草本土壤渗透性随土层深度的增加而降低；相对于裸地而言,4种草本均能显著增强土壤渗透性,其土壤渗透性优劣表现为:香根草＞紫花苜蓿＞百喜草＞狗牙根；(3)土壤的初始入渗率、稳渗率、平均渗透率和渗透总量等各参数均随根长密度和根表面积密度增大而增强,且与直径介于0.5-5 mm不同径级的根系特征之间存在明显的相关性,故根系对土壤渗透性的增强作用主要归功于0.5-5 mm径级的根长密度和根表面积密度；(4)根长密度、根表面积密度对考斯加科夫入渗模型参数K和a有较大影响,随着根长密度和根表面积密度的增加,表征土壤初始入渗率的K值逐渐增大,而表征入渗能力衰减的参数a逐渐减小.

Root features of typical herb plants for hillslope protection and their effects on soil infiltration

Plant root system plays important role in soil erosion protection and affects hillslope hydrological process through infiltration. To quantitatively investigate root features of typical herb plants for hillslope protection in the Three Gorges Reservoir Region and their influence on soil infiltration, soil initial infiltration, average infiltration, stable infiltration and accumulative infiltration were measured on 4 typical hillslope protection herb plants,Vetiveria zizanioides(Lin.) Nash,Paspalum notatum Flugge,Cynodon dactylon(L) Pers. and Medicago sativa L., ith bare land as a control. Soil samplers were used to take soil samples from the test area for laboratory experiments. Double-rings method was applied to make on-site measurement of soil infiltration. Root analysis system, WinRHIZOPro.2004c was used to characterize the root systems. The results indicated that: (1) Vetiveria zizanioides(Lin.) Nash and Medicago sativa L. had considerable higher root length density and root surface area density, as compared with paspalum notatum Flugge,Cynodon dactylon(L) Pers. (2) The soil infiltration rates were significantly amongst the different herb plants and at different soil layers under the same herb plants. The soil infiltration rates of soil under herb plants were significantly higher that of bare soil and declined with the increase in soil depth. The soil infiltration rates from high to low were in the order of Vetiveria zizanioides(Lin.) Nash, Medicago sativa L., Paspalum notatum Flugge, Cynodon dactylon(L) Pers.(3) The initial, average and steady infiltration rates were 2.42, 1.65 and 1.38 mm/min for Cynodon dactylon(L) Pers., 3.87, 2.42 and 2.11 mm/min for Medicago sativa L., 4.84, 3.37 and 3.00 mm/min for Vetiveria zizanioides(Lin.) Nash and 2.93, 1.79 and 1.39 mm/min for Paspalum notatum Flugge and 1.31, 0.86 and 0.71 mm/min for bare land respectively. (4) The soil initial, steady and average infiltration rates as well as cumulative infiltration were increased with increases in root length density and root surface area density, which were evidently correlated with root diameter from 0.50 to 5.00 mm.(5)Root length density and root surface density had significant impacts on Kostiakov''s model parameters, K and a. The K value, representing initial infiltration rate increased with increase in root length density and root surfer area density and the a value, representing the decrease rate of infiltration decreased with them. The K value from high to low were in the order of Vetiveria zizanioides(Lin.) Nash, Medicago sativa L., Paspalum notatum Flugge, Cynodon dactylon(L) Pers., Bare land. The K value and a value were 1.382 and 0.473 for Bare land, 4.275 and 0.307 for Vetiveria zizanioides(Lin.) Nash, 3.814 and 0.312 for Medicago sativa L,3.325 and 0.452 for Paspalum notatum Flugge and 2.742 and 0.404 for Cynodon dactylon(L) Pers. respectively. The results will be useful for hillslope vegetation protection and soil erosion control.