红壤丘陵区不同盖度生物结皮对水分入渗的影响

为探究不同盖度生物结皮对入渗特征的影响,在红壤丘陵区咸宁选取第四纪黏土发育土壤(S型)和泥质页岩发育土壤(N型)上的生物结皮,设计6个盖度水平(裸地,1%~20%,20%~40%,40%~60%,60%~80%,80%~100%),使用微型圆盘入渗仪(mini disk)测定土壤入渗过程,探究入渗过程的影响因素,同时采用3种常见的入渗模型对入渗过程进行拟合,并评价模型适用性。结果表明:(1)相对于裸地,生物结皮发育提高土壤有机质和黏粒含量,增加结皮厚度和生物量,降低砂粒含量。(2)第四纪黏土发育土壤水分入渗特征随生物结皮盖度的增加而逐渐降低,初始入渗速率、稳定入渗速率、平均入渗速率、非饱和导水率的变化范围分别为0.25~1.55,0.13~0.91,0.17~1.11,2.04~8.48 mm/min。泥质页岩发育土壤除40%~60%盖度砾石含量较高,土壤水分入渗也随盖度的增加而逐渐减小,80%~100%盖度的初始、平均和稳定入渗率较裸地分别降低91.14%,87.64%和91.30%,生物结皮的存在阻碍土壤水分入渗。冗余分析表明,对于第四纪黏土发育土壤,生物量(54.30%)对其入渗特征的解释度最高,泥质页岩发育土壤则为盖度(39.30%)和砾石含量(34.00%)。(3)Horton模型、Kostiakov模型、Philip模型3种主流入渗模型中Horton模型拟合效果最优。研究结果可为揭示湿润区生物结皮水分运移规律提供科学参考。

Effects of Biocrust with Different Coverage on Water Infiltration in Red Soil Hilly Region

In order to explore the influence of biocrust with different coverage on infiltration process, biocrust from quaternary clay developed red soil (S type) and argillaceous shale developed soil (N type) were selected in the red soil hilly area of Xianning. And six coverage levels (bare land, 1%~20%, 20%~40%, 40%~60%, 60%~80% and 80%~100%) were set. The Mini disk infiltration instrument was used to determine the soil infiltration process and explore the factors affected the infiltration process, meanwhile three common models were used to simulate the infiltration process and the suitability of the model were compared. The results showed that:(1) Compared with bare soil, the development of two types of biocrust increased soil organic carbon, clay content, crust thickness and biomass, while decreased sand content. (2) The water infiltration characteristics of S-type soil decreased gradually with the increasing of biocrust coverage. The initial infiltration rate, stable infiltration rate, average infiltration rate and unsaturated water conductivity varied from 0.25 to 1.55, 0.13 to 0.91, 0.17 to 1.11 and 2.04 to 8.48 mm/min, respectively. In N-type soil, the soil water infiltration decreased with the increasing of coverage except for 40% to 60% (high gravel content). The initial infiltration rate, average infiltration rate and stable infiltration rate of 80% to 100% coverage decreased by 91.14%, 87.64% and 91.30%, respectively, compared with the bare soil. The presence of biocrust impeded the soil water infiltration. The RDA analysis showed that for S-type soil, biomass (54.30%) had the highest interpretation for its infiltration characteristics, while for N-type soil, they were coverage (39.30%) and gravel content (34.00%). (3) Among the three mainstream infiltration models, Horton model, Kostiakov model and Philip model, Horton model had the best fitting effect. The results could provide a useful reference for the study of water transport law of biological crusts in humid areas.