土壤结皮对西南横断山区土壤坡面产流产沙及养分流失的影响

采用人工降雨方法,模拟在无结皮和有结皮不同发育程度下,研究结皮对横断山区土壤坡面产流形成、侵蚀过程及养分流失过程的影响.结果表明,结皮促使坡面产流提前发生,但对坡面产流量的影响不甚明显;对坡面产沙量却有明显的作用;5°坡面有结皮处理的坡面产沙量较无结皮减少54％,而10°坡面有结皮处理的坡面产沙量则增加16％,表明土壤结皮对坡面侵蚀的影响与地面坡度有密切关系.坡面土壤磷钾流失过程均呈幂函数衰减趋势,无结皮坡面衰减速率较快,随着结皮不断发育,钾素流失形式以浸提态为主,逐步被溶解态所取代,磷素始终以泥沙浸提态流失占优势;与无结皮相比较,结皮坡面K+流失总量降低62.39％,径流样溶解态磷(DP)、泥沙浸提态磷(SEP)和泥沙浸提态钾(SEK)的流失总量分别降低33.33％ 、37.10％和78.36％.土壤结皮具有减少土壤养分流失和延缓坡面土壤质量退化的作用.

Effects of soil crust on runoff, sediment yield and nutrient loss on slope of southweast Hengduan Mountains

Simulated rainfall experiments were conducted to investigate the effects of soil crust on hillsloperunoff, sediment yield and nutrient loss process of Hengduan Mountains. The experimental design included two kindsof soil surface (crust and non-crust), one rainfall intensity (60 mm/h) and two gradients (5and 10). Results showedthat the runoff of crust slope occurred earlier than that of non-crust, but runoff yield was similar. Compared withnon-crust slope, sediment yield of 5slope with crust decreased by 54%, while the sediment yield of 1slope withcrust increased by 16%. These results suggested that crust had less effect on runoff yield; however, it had great effecton sediment yield. The declining process of phosphorus and potassium losses with runoff and sediment was a powerequation, and the losing velocity of phosphorus and potassium was the fastest for no crust land. With the differentdevelopment status of soil crust from no crust to heavy crust, the dominant position of sediment extractable potassium(SEK) loss was replaced gradually by the dissolved potassium loss, but the sediment extractable phosphorus(SEP) losswas dominant all the time. Compared with no crust hillslope, the total amount of K+, DP, SEP and SEK lossdecreased by 62.39%, 33.33%, 37.10% and 78.36%, respectively. It implies that soil crust may make soil nutrientloss decreased and control soil quality degeneration tendency.