不同类型生物结皮对坡面产流特征的影响

生物结皮是黄土高原地区坡面水土流失不可忽略的影响因素,目前生物结皮对坡面产流特征的影响仍不明确.在陕北神木县六道沟小流域通过径流小区放水试验,以裸地为对照,研究了浅色藻结皮、深色藻结皮、混合结皮(藻+藓)以及藓结皮4 种类型生物结皮对坡面产流特征的影响.结果表明:① 浅色藻结皮、深色藻结皮和混合结皮较裸地显著降低了初始产流时间,三者的初始产流时间较裸地分别减少89.0%、96.2%和96.0%;而藓结皮则较裸地显著增加了初始产流时间.② 浅色藻结皮和混合结皮较裸地显著延长了退水持续时间,其退水持续时间分别是裸地小区的2.28和2.13倍;而深色藻结皮的退水持续时间与裸地差异不显著.③ 深色藻结皮和藓结皮的径流流速较裸地分别降低了29.1%和67.3%;藓结皮的径流流速显著低于其他生物结皮小区;各生物结皮小区的径流深与裸地均无显著差异;浅色藻结皮的径流深显著高于深色藻结皮.④ 不同类型的生物结皮较裸地明显改变了坡面产流过程和径流量;浅色藻结皮小区的径流系数显著高于裸地,深色藻结皮和混合结皮小区的径流系数较裸地差异不显著;浅色藻结皮小区的径流系数是深色藻结皮小区的2.44 倍,差异显著;放水时段内,藓结皮小区没有径流流出.以上结果表明,生物结皮是坡面产流特征的重要影响因素,影响程度与生物结皮的发育阶段和生物组成有关.

Impact of Different Types of Biological Soil Crusts on Slope Runoff Generation

Biological soil crusts (biocrusts) are non- ignorable influence factors of soil and water loss in the Loess Plateau region of China, however the impact of biocrusts on slope runoff generating is poorly understood so far. In Liudaogou small catchment that locates in Shenmu County, north of Shaanxi Province, the impact of four types of biocrusts and bare soil (no biocrusts) on runoff generating were studied in the runoff plots through simulated overland flow experiment. The four types of biocrusts were light cyanobacterial crust, dark cyanobacterial crust, cyanobacterial with moss crust (mixed crust hereafter) and moss dominated crust, which represent four different succession stages of biocrusts in the region. The results showed that: 1) compared with bare land, both light, dark cyanobacterial crusts and mixed crusts significantly reduced the time of runoff initiation by 89.0%, 96.2% and 96.0%; While the moss dominated crust markedly increased the time of runoff initiation. 2) The duration of runoff recession on light cyanobacterial crust and mixed crust were respectively 2.28 and 2.13 times higher than that on bare land; while that on dark cyanobacterial crust had no significant difference with that on bare land plot. 3) The runoff velocity was reduced by 29.1% by the dark cyanobacterial crust and 67.3% by the moss dominated crust compared with that on bare land; The runoff velocity on moss dominated crust was markedly slower than that on the other biocrust land. The runoff depth in biocrust plots did not show significant difference with that in bare land plot; The runoff depth on light cyanobacterial crust was significantly deeper than that on dark cyanobacterial crust. 4) The process and the amount of runoff in plots with different types of biocrusts showed obvious differences with that in bare land plots; The runoff coefficient in light cyanobacterial crust plot was significantly higher than that in bare land plots, while the runoff coefficient in dark cyanobacterial crust plots and mixed crust plots had no significant difference with thatin bare land plot. The runoff coefficient in light cyanobacterial crust plot was 2.44 times higher than that in dark cyanobacterial crust plots; No runoff generated on moss dominated crust during the runoff period. The results suggested that biocrusts are important influence factors on runoff generation, and the extend of influence was related to the succession stages and the composition of the biocrusts.