The relative efficiency of four representative cropland conversions in reducing water erosion: evidence from long‐term plots in the Loess hilly area, China

Abstract

Large areas of traditional slope cropland were recently converted to other land-use types in the semiarid Loess Plateau of China. In this study, we selected four representative conversion options of slope croplands, i.e., pastureland rotated with cropland (cultivated with Medicago sativa L. and rotated with Triticum aestivum L.), shrubland and woodland (afforested with Hippophae rhamnoides L. and Pinus tabulaeformis), and grassland (native herbage Stipa breviflora) to study the effect of landuse conversion by comparing with traditional cropland. Compared with slope cropland, the relative effects of different conversion options on surface runoff and soil erosion were assessed over a 14-year measurement period. Observations showed that distinct features and consequences of vegetation succession were found among the conversion options. Plots of shrubland had the highest vegetation coverage with dense undergrowth; natural herbaceous and subshrub species gradually spread into plots of grassland resulting in higher vegetation cover. Neither bushes nor herbs colonized the plots of Pinus tabulaeformis, which resulted in a higher percentage of bare soil. Significant differences in runoff generation, sediment yield and conservation efficiencies among the selected conversion options were detected through an analyses of variance (ANOVA). Compared with cropland, total runoff and sediment decreased by 65 per cent and 95 per cent in shrubland, 41 per cent and 92Á5 per cent in grassland, 18 per cent and 77 per cent in woodland, and 12 per cent and 58 per cent in pastureland, respectively. The ranking of soil and water conservation efficiencies was shrubland > grassland > woodland > pastureland > cropland. Based on the effectiveness of soil and water conservation, shrubland and grassland are highly recommended as promising options for cropland conversion projects. However, pastureland and woodland are not suggested as potential options for slope-cropland conversion because of low soil and water conservation in the long term.

Ecologically asynchronous agricultural practice erodes sustainability of the Loess Plateau of China

“…Crop fields, with winter wheat accounting for 50-60% of the area, lose at least 5000 MgÁkm À2 Áyr À1 more soil to erosion than natural vegetation. This estimate is consistent with earlier reports that natural vegetation is able to decrease soil loss by 58-98% compared to cropland (Huang et al 2006, Wei et al 2007. A previous study by Kang et al (2001) revealed that plowed winter wheat fields had 2-3 times more soil erosion than corn and no-till cropfields between June and August.…”

“…For example, was the erosion caused by poor cultivating practices or something innate about the particular crops grown? Other recent studies (Kang et al 2001, Huang et al 2006, Wei et al 2007) discussed the causes but did not assess the seasonal (monthly) relationship among vegetation, climate and soil erosion in depth. Such an assessment could enable a landscape-level understanding and ultimately facilitate the development of ecosystemmanagement and regional-planning strategies.…”

Influence de l’hydromorphie sur la variabilité des stocks de carbone à l’échelle de versants dans une hêtraie (forêt de Fougères — Ouest de la France)

“…However, processes of carbon redistribution may also occur at the bottom of the valley in the STE site due to silt deposits and erosion by stream flow. According to the literature, runoff and erosion in forests are generally lower than in denuded and arable areas, and are similar to or greater than in pasture and shrub-land [9,15,40]. These processes are related to rainfall characteristics (volume, intensity, duration and Mean C 130 37 cm frequency), soil parameters, topography and vegetation structure.…”

Rapid revegetation by sowing seed mixtures of shrub and herbaceous species

“…Trees with large canopy are more effective in reducing wind speed, whereas shrubs are more effective in trapping transporting materials (Leenders et al, 2007). Compared to herbaceous species, shrubs have more developed root systems to improve soil structure and conserve water in deep layers, resulting in a better effect on soil and water conservation (Huang et al, 2006;Wei et al, 2009), and its effect is less affected by rain intensity compared to herbs (Zhang et al, 2014). Trees develop slowly (Ji et al, 2011) and have limited effect on soil protection during the early stage of development (Zhang and Shao, 2003), while herbs germinate and grow fast, rapidly covering the ground to prevent splash erosion and decrease runoff (Franklin et al, 2012).…”