Long-term effect of soil and water conservation measures on runoff, sediment and their relationship in an orchard on sloping red soil of southern China

Abstract

The effect of soil and water conservation measures (SWCMs) is usually dependent on time. Thus the trend in reducing runoff and sediment over time is a very important theoretical problem for evaluating the effectiveness of SWCMs. Moreover, there is still a lack of comprehensive assessment of water erosion dynamics following implementing SWCMs despite their ecological significance. Therefore, the long-term impact of SWCMs on runoff and sediment and their relationships was assessed for an orchard on sloping red soil in southern China. Overland flow and erosion sediment were continuously observed for 15 years on citrus experimental plots under one of four treatments: grass strips, strip intercropping, level terrace and clean-tillage. By means of Mann–Kendall trend tests and double cumulative curves, the time series of runoff and sediment under the different treatments were analyzed. Furthermore, we linked the effect of soil conservation and the relationship between runoff and sediment variation to determine the mechanism of conservation measures on sediment reduction. The results showed that the first 4 years was the key period to prevent soil erosion for this orchard, and then the intensity of soil erosion decreased below 500 t·km–2·a–1. Considering economic costs and ecological effect, grass strips were the best protective measure for this test situation. The fitted curves of the effect of SWCMs on sediment reduction over time showed an ‘L’ form, but on runoff there was an approximately horizontal line. The SWCMs did not change the rainfall–runoff relationship, but did change the runoff–sediment erosion relationship. The erosion reduction mechanism of SWCMs in the early phase was a joint function of reducing runoff and changing the runoff–sediment relationship, and in the post-stable phase it worked mainly by reducing runoff. The results provide the basis for rational allocation of SWCMs considering location and time.

Effectiveness of Chinese pine (Pinus tabulaeformis) plantation at reducing runoff and erosion rates in Anjiagou Watershed in Semi-arid Region of Gansu, China

“…Compared with the relatively less compacted, sloping farming soil layer of wheat plots, the forest floor surface of the aging Chinese pine forest, remained un-disturbed for a much longer time. Topsoil compaction was enhanced, which may produce dry soil crusts there by reducing the water infiltration capacity of soil and causing an increase in runoff for some heavy rainfall as reported in previous studies [38,49]. Meanwhile, the forest canopy had a strong inception of rain drops, which potentially reduced the detaching force of rain drips, leading to reduced runoff and erosion rate [47].…”

“…plantation plots and from 1986-1992, 2007-2019 for the wheat (control) plots. The runoff and erosion amounts measured from each plot were standardized as runoff rate (m 3 ha -1 ) and soil erosion rate (t ha -1 ) for the convenience of quantitative analysis and comparison between different plots [7,38].…”

Regions and Their Typical Paradigms for Soil and Water Conservation in China

“…The red soil region in South China covers a total area of 1.2400 × 10 6 km² and comprises nine subregions, i.e., hills and lower-reach plain subregion of the Yangtze River and Huaihe River, hills and plain subregion in the middle reaches of the Yangtze River, mountain and hills subregion in the Dabie Mountains and Tongbai Mountains, Jiangnan mountain and hills subregion, Nanling mountain and hills subregion, mountain and hills subregion in Zhejiang and Fujian, hills and tableland subregion in coastal areas of South China, hills and tableland subregion in Hainan and South China Sea islands, and mountain and hills subregion in Taiwan. The hilly and mountainous subregions cover approximately 60.6% of the land area (Tu at al., 2018). The average annual precipitation ranges from 800 to 3500 mm, approximately 80.0% of which falls between April and September.…”

Assessing the Impact of Engineering Measures and Vegetation Restoration on Soil Erosion: A Case Study in Osmancık, Türkiye

“…Globally, soil erosion is effectively controlled by soil and water conservation measures. Even on steep slopes (25 • ), soil erosion can be reduced by as much as 70% by applying soil conservation measures [33].…”