喀斯特坡地侵蚀泥沙养分流失与粒径分布的关系

Relationship Between Nutrient Loss and Particle Size Distribution in Eroded Sediment of Karst Slope

在丹江口库区喀斯特地区,研究分析自然降雨条件下5种不同植被覆盖类型(疏林地(C1)、乔木林地(C2)、坡耕地(C3)、荒草地(C4)、灌草地(C5))坡面侵蚀泥沙的氮、磷、钾养分流失及泥沙粒径分布特征,探讨泥沙养分流失与粒径分布的关系。结果表明:(1)侵蚀泥沙以粉粒(2~50 μm)、砂粒(50~2 000 μm)为主,0~20 μm颗粒含量随降雨强度的增加而减少。0~2 μm颗粒富集度集中在3.08~6.62,2~20 μm颗粒富集度集中在2.48~3.58,20~2 000 μm颗粒富集度集中在1左右。C4的0~2 μm颗粒含量及其富集度明显高于其他植被覆盖类型。(2)速效钾的流失量远高于速效氮、磷流失量。氮素富集度集中在1左右,TP富集度集中在1.41~1.96,AP富集度集中在5.00~8.77,AK富集度集中在1.79~3.05,泥沙对磷、钾养分有明显富集作用,而对氮素富集作用很小。不同植被覆盖类型中,C4的TP、AK含量显著高于C1、C2、C3、C5(P<0.05),C4有增加TP、AK养分含量的作用,且C2、C4的氮、磷富集度相对较大。C3的养分流失总量最大,C1、C2、C4、C5有明显减小养分流失的作用,其中C2控制养分流失的效果最明显。(3)侵蚀泥沙的TN、TP、AP、AK含量与0~2,2~20,20~50 μm含量呈正相关关系,且与0~2 μm的相关性显著(P<0.05),侵蚀泥沙的养分含量会随着0~50 μm颗粒含量的增加而增多。

In the karst area of the Danjiangkou reservoir area, the nitrogen (N), phosphorus (P) and potassium (K) nutrient loss and the sediment particle size distribution characteristics of slope erosion in five vegetation cover types (arbor forest land (C1), sparse forest land (C2), farmland (C3), grassland (C4), shrub grassland (C5)) under natural rainfall conditions were observed to discuss the relationship between sediment nutrient loss and particle size distribution. The results showed that: (1) The sediment of erosion was dominated by silt (2~50 μm) and sand (50~2 000 μm). There were significant differences in the sorting of clay (0~2 μm) particles between different vegetation cover types (P<0.05). The contents of fine particles (0~20 μm) in the eroded sediment decreased with the increase of rainfall intensities. The 0~2 μm particle concentrations were concentrated in 3.08~6.62. The 2~20 μm particle concentrations were concentrated in 2.48~3.58. The 20~50 μm particle concentrations were concentrated in 1.04~1.62. The 50~100 μm particle concentrations were concentrated in 0.61~0.88. The 100~2 000 μm particle concentrations were concentrated in 0.43~1.15. The 0~20 μm particle enrichment of C4 was the largest, and the 0~20 μm particle enrichment of C3 was relatively small. (2) Among the available nutrients, the loss of available K (AK) was much higher than those of available N (AN) and P (AP). The concentrations of total P (TP) and AK of C4 were significantly higher than those of C1, C2, C3 and C5 (P<0.05). The total nutrients loss in C3 was the largest, and C1, C2, C4 and C5 had the significant effect on reducing nutrient loss. The effect of C2 on controlling nutrient loss was the most obvious. The total N (TN) concentrations were concentrated at 0.56~1.25, the NH4+—N at 1.08~1.17, the NO3-—N at 0.94~1.50, and the TP at 1.41~1.96, the AP at 5.00~8.77, the AK at 1.79~3.05. The N and P enrichment were relatively low in C3, and relatively large in C2 and C4. (3) The contents of TN, TP, AP and AK in erosion sediment were positively correlated with the contents of 0~2, 2~20 and 20~50 μm, and the correlation with 0~2 μm was significant (P<0.05). The nutrient concentrations increased as the fine particle content increased.