水保所知识产出(1956---)知识库

钙质结核是黄土高原成土过程、土壤侵蚀和人类活动的产物，尤其是在侵蚀严重
的黄土高原水蚀风蚀交错带，钙质结核常常在表土聚集。钙质结核因尺寸和水力性质
不同于土壤颗粒，能影响土壤蒸发、入渗、坡面产流产沙，加之其本身能吸收一定的
水分，还会影响对土壤储水量的估算。本研究以黄土高原水蚀风蚀交错带六道沟小流
域表土钙质结核为研究对象，通过野外调查的方法来分析六道沟小流域坡面表土钙质
结核的空间分布特征和影响因素，在室内开展模拟实验来量化钙质结核含量对土壤剖
面水分分布和土壤储水量的影响，结合定位观测试验来研究砾石-植被覆盖条件下土
壤水分和地温的变化特征，取得以下主要结果：
（1）钙质结核质量分数可以用来指示坡面的土壤侵蚀状况。土壤黏粒体积分数沿坡
面呈逐渐降低趋势; 钙质结核质量分数沿坡面呈单峰曲线分布，在坡面 1/4 - 1/3 的
位置（距离坡顶 20 - 30 m）处，达到峰值（10% - 15%）。钙质结核质量分数与坡度
呈线性正相关，与植被地上生物量( 盖度) 呈单峰曲线关系，峰值即为植被影响钙质
结核质量分数的临界点，临界点处的植被盖度在 11% - 16%之间。影响坡面钙质结核
分布的最主要因素为坡度和植被; 小尺寸的钙质结核在坡面分布范围最广、数量最多，
起决定作用的钙质结核尺寸在 5 - 15 mm 之间。
（2）定位观测研究发现，钙质结核能影响土壤温度和水分。植被＋钙质结核覆盖下
日平均地温最低，低于仅有钙质结核覆盖和对照（裸地）。不同覆盖类型（裸地，植
被覆盖，钙质结核覆盖，植被＋钙质结核覆盖）的土壤温度在不同时间尺度上（7 和
9 月份）存在显著差异（P < 0.05）。通过对土壤温度变异分析发现，随着土层深度增
加，变异系数呈减小趋势；9 月份 0-5cm 土层温度存在中等变异（15% 其余土层土壤温度均为弱变异（C V  < 15%）。在 0-50cm 土层，不同覆盖条件下土壤水
分变化不同，裸地土壤水分变化幅度最小。通过对不同覆盖类型下土壤水分变异分析，
发现土壤中有钙质结核出现的土层（土层深度为 60cm 处，或 80cm 处）土壤水分存
在大的变异，属于中等变异甚至强变异（C V >35%）。
（3）钙质结核能影响土柱中土壤水分分布。土柱剖面中钙质结核含水量与土壤含量分布模式相反，且土壤含水量明显高于钙质结核含水量。在高钙质结核含量下（0.2，
0.3 和 0.4 kg·kg -1 ），表层与底层的土壤储水量无显著差异（P>0.05）；在低钙质结核含
量下（0 和 0.1 kg·kg -1 ），表层与底层的土壤储水量存在显著差异（P<0.05）。钙质结
核储水量与有效储水量随钙质结核含量增加而增大。钙质结核有效储水量可占到其自
身储水量的 50%左右，如在不考虑土壤钙质结核中储存的水分情况下，在四种钙质结
核含量（0.1，0.2，0.3 和 0.4 kg·kg -1 ）下的土壤储水量分别被低估了 3.02%，7.96%，
10.49%和 16.88%。
关键词：土壤侵蚀；钙质结核；钙质结核储水量；土壤储水量；黄土高原水蚀风蚀交
错带

Caliche nodule is a product from soil genesis process, soil erosion and human activities
especially in the wind-water erosion crisscross region of the Loess Plateau the caliche
nodules often gather in surface soil. Due to the size and hydraulic properties of caliche
nodule different from soil particle, it can affect soil evaporation, infiltration and surface
runoff and sediment yield. As being a medium with high water absorption, caliche nodule
can also affect the estimation of soil water storage. In this study, we took the caliche
nodule presenting in Liudaogou small catchment in the wind-water erosion crisscross
region of the Loess Plateau as an object and investigated spatial distribution of caliche
nodule and its influencing factors through field sampling, effects of caliche nodule content
on soil water distribution in soil column profile and soil water storage, and the variation
characteristics of soil temperature and soil water in the plots with caliche nodules mulching
by field in-situ observation. We draw following conclusions:
(1) Caliche nodule content in topsoil indicated intensity of soil erosion on hillslopes. Soil
clay particle decreased gradually along the hillslopes. Caliche nodule content showed a
distribution pattern of single peak along the hillslopes and it achieved peak value (10 -
15 %) at the position of 1/4 - 1/3 hillslopes (about 20 - 30 m distance from the top of the
hillslopes). Caliche nodule content was positively correlated with slope gradient. It had a
single peak curve relationship between caliche nodule content and vegetation
above-ground biomass. This peak value was the threshold point of vegetation affecting
caliche nodule content and the vegetation coverage at the threshold point was among 11 -
16 %. Slope gradient and vegetation were two most important factors to control caliche
nodule distribution on the hillslopes. Small size caliche nodules spread more widely on the
hillslopes and meanwhile their numbers were the most. The dominant size of caliche
nodule was 5 - 15 mm.
(2) Field in-situ observation showed that caliche nodule affected soil temperature and soil  water. The average soil temperature in bare soil land was the highest and in the land with
vegetation and caliche nodule mulching was the lowest. The difference in soil temperature
for different months was significant (P < 0.05) under four land uses: bare soil, vegetation
cover, caliche nodule cover and both vegetation and caliche nodule cover. In addition, the
variability coefficient of soil temperature in 0-5 cm soil layer were moderate in September.
The variability coefficient increased with increasing soil depth. In top 50 cm soil layer, the
changes of soil water content under different vegetation-caliche nodule coverage
conditions were different. Variation range of soil water in bare soil land was the smallest.
Caliche nodule affected measurement result of soil water, especially in the positions of 60
cm and 80 cm soil layers.
(3) Caliche nodule can affect soil water distribution in soil column. The distribution pattern
of caliche nodule water content (CWC) along the profile for different treatments were
different from that of soil water content (SWC). Soil water storage (SWS) between top soil
layer and bottom soil layer had no significant difference when soil contained relatively
high caliche nodule content (CNC= 0.2, 0.3 and 0.4) (P > 0.05). When CNC ≤ 0.1, the
difference in SWS for top soil layer and bottom soil layer were significant (P < 0.05). Both
caliche nodule water storage and its available water storage increased with increasing
caliche nodule content. The SWS could be underestimated by 3.02%, 7.96%, 10.49% and
16.88%, respectively for the soils with CNCs of 0.1, 0.2, 0.3 and 0.4, respectively.
Available water storage in caliche nodules accounted for almost half of total caliche nodule
water storage.
Keywords: Soil erosion, Caliche nodule, Caliche nodule water storage, Soil water storage,
The wind-water erosion crisscross zone of the Loess Plateau