工程堆积体产流产沙及水沙效益对植被近地表特征的响应

针对陡坡工程堆积体水土流失严重的问题，通过野外模拟降雨试验开展植被不同近地表特征对堆积体产流产沙和蓄水减沙效益特征影响的定量研究。选择土石混合堆积体（10%砾石质量分数，坡度30°）作为工程侵蚀下垫面的典型代表，并以裸坡（bare slope, BS）为对照，定量分析了植被在3种近地表特征条件下（完整植株（intact grass，IG），不含叶（not leaf，NL），只含根系（only root，OR））对堆积体产流产沙特征和蓄水减沙效益影响。结果表明：1）植被在IG条件下延缓坡面径流发生使其较BS滞后，效益达50.74%～188.98%，但不完整植被（NL、OR）会加速径流发生使其较BS提前2.19%～70.12%；2）植被在NL和OR下的瞬时径流率比IG增大0.20%～185.58%，在降雨强度1.8 mm/min的瞬时径流率甚至比BS高1.20%～169.10%；植被在IG和NL条件下瞬时侵蚀速率比BS减少0.91%～98.71%，但在降雨强度达到1.8 mm/min时OR条件下甚至增大侵蚀使其比BS高6.76%～75.63%；3）随降雨强度增大，植被在NL和OR条件下的减沙效益由95.18%和68.31%分别递减至46.58%和-68.13%，但对IG下的减沙效益影响小（效益差异＜2%），平均蓄水效益随降雨强度增大而减小。不同堆积体水沙呈显著线性相关（R²在0.40～0.88），且径流率达到4 L/min会显著改变植被对堆积体坡面防护效益。提出开展堆积体生态修复时选择冠层丰富的植被，同时要避免外部因素对植被造成损害。研究结果对于揭示植被防护扰动边坡侵蚀机制具有重要意义，可为堆积体植被修复提供实践指导。

Response of runoff and sediment production and sediment and water benefits of engineering spoil heaps to vegetation characteristics

Engineering spoil heaps as a severely eroded geomorphic unit in production and construction projects have generated widespread attention to soil erosion. Vegetation was the most direct and effective means for ecological restoration of engineering disturbed underlying surfaces. Conducting quantitative research on the effects of different near-surface characteristics of vegetation on the runoff and sediment production and water storage and sediment reduction benefits of spoil heaps under field simulated rainfall experiments was of great significance for deeply revealing the internal mechanism of vegetation protection disturbance slope erosion. This study selected mixed soil and rock spoil heaps (10% gravel mass fraction, slope 30°) as a typical representative of engineering erosion underlying surface, and used bare slope (BS) as a control. Four sets of eight engineering accumulation models were established in the field, with dimensions of 3.46 m×2.00 m×0.60 m (length), and the projected slope length was 3 m. Quantitative analysis was conducted on the characteristics of runoff and sediment production and the benefits of water storage and sediment reduction of the spoil heaps under three types of near-surface characteristics of vegetation (intact plant IG, no leaf NL, only root OR) through field rainfall experiments (set rainfall intensity as 0.8, 1.2 and 1.8 mm/min). The Cynodon dactylon (CD) as a grass species for vegetation restoration in the study area was a typical type of grass species with strong growth ability and belongs to the perennial grass species, which was also widely used in engineering construction. Further, it reveals the internal mechanism of vegetation regulation of spoil heaps erosion from the perspective of its impact on water and sediment relationships. The results showed the following: 1) The occurrence of runoff begin time on the gentle slope surface of intact plants (IG) resulted in a delayed benefit of 50.74%-188.98%, as compared to BS, while the lack of vegetation canopy (NL, OR) accelerated the occurrence of runoff begin time, causing it to occur 2.19%-70.12% earlier than BS. 2) The instantaneous runoff rate of vegetation under NL and OR treatments was 0.20%-185.58% higher than that under IG treatment, while the instantaneous runoff rate of OR and NL treatments under heavy rainfall conditions (1.8 mm/min) was 1.20%-169.10% higher than that of BS. The instantaneous soil loss rate of vegetation under IG and NL conditions decreased by 0.91%-98.71% compared to BS. They even increased erosion under OR conditions when the rainfall intensity reached 1.8 mm/min, making it 6.76%-75.63% higher than BS. 3) As the rainfall intensity increased, the sediment reduction benefits of vegetation under NL and OR treatments decreased from 95.18% and 68.31% to 46.58% and -68.13%, respectively. However, the impact on sediment reduction benefits under IG treatment was small (benefit difference<2%), and the average water storage benefits decreased with increasing rainfall intensity. There is a significant linear correlation between water and sediment in both BS and vegetated spoil heaps (R² ranging from 0.40 to 0.88), and a runoff rate of 4 L/min significantly changed the protective effect of vegetation on the slope surface of the spoil heaps. The vegetation and its near-surface characteristics had significant impacts on the average runoff and sediment yield and per unit runoff sediment yielding (P<0.05). It is proposed to choose vegetation with a rich canopy when carrying out ecological restoration of spoil heaps, while avoiding external factors that may cause damage to vegetation. The research results are of great significance for revealing the erosion mechanism of vegetation protection disturbance slopes, and can provide practical guidance for the restoration of accumulated vegetation.