Effects of vegetation restoration and slope positions on soil aggregation and soil carbon accumulation on heavily eroded tropical land of Southern China

Abstract

Background aim and scope Soil organic carbon (SOC) accumulation is strongly affected by soil erosion and deposition that differ at slope positions of a watershed. However, studies on the effects of topography on soil aggregation and SOC dynamics, especially after the implementation of vegetation restoration, are rare. Poorly understood mechanisms and a lack of quantification for the suite of ecological benefits brought by the impacts of topography after planting further obstructed our understanding of terrestrial ecosystem carbon (C) sequestration. The purposes of this study are to (1) quantify the impacts of vegetation restoration on size and stability of soil aggregates and the sequestration of C in soil and (2) to address the impacts of various slope locations on aggregates and SOC distribution. Materials and methodsThe experimental sites were set up in 1959 on a highly disturbed barren land in a tropical and coastal area of Guangdong province in South China. One site received human-induced vegetation restoration (the restored site), while the other received no planting and has remained as barren land (the barren site). The soil in the study sites was a latosol developed from granite. Soil samples were taken from 0 to 20 and 20 to 40 cm soil layer at shoulder and toe slope positions at both sites for comparisons. Soils were analyzed for proportion of soil macroaggregates (>0.25 mm), the SOC in soil layers, and the aggregate soil organic carbon (AOC) at different aggregate sizes. Results and discussion Measurements in 2007 showed that fractions of water stable macroaggregates in 0-40 cm at shoulder and toe slope ranged from 28% to 45%, about one third to one half of those of dry macroaggregates (91-95%) at the restored site. Soil macroaggregates were not detected at barren site in 2007. Average SOC storage in 0-40 cm soil layer of shoulder and toe slope positions at the restored site was 56.5±10.9 Mg C ha −1 , about 2.4 times of that (23.4± 4.6 Mg C ha −1 ) at barren site in 2007. Since 1959, the soil aggregation and SOC storage are significantly improved at the restored site; opposite to that, soil physical and chemical quality has remained low on the barren land without planting. SOC storage in 0-40 cm at toe slope was 15.9± 1.8 Mg C ha −1 , which is only half of that (30.9±9 Mg C ha −1 ) at shoulder slope of the barren site; this is opposite to the pattern found at restored site. The ratios of AOC in 0-20 cm to AOC in 20-40 cm at toe slope were lower than those at shoulder slope of the restored site. The comparison of organic carbon sequestered in soils at different slope positions suggest that soil aggregates played a role in sequestering C based upon landscape positions and soil profile depth as a consequence of soil erosion and deposition.

Biotechnical Potential of Paspalum Submitted to Simple Superphosphate Doses and Moisture Content

“…The erosion of fluvial slopes, strongly resulting from anthropic actions, has directly interfered in the survival of species of fauna and flora; the biological communities in aquatic environments; reduction of agricultural areas; as well as to intensify the silting of watercourses, making it difficult to navigate, fish and public water supply (TANG et al, 2010;RIBEIRO et al, 2011).…”

Reforestation and slope-position effects on nitrogen, phosphorus pools, and carbon stability of various soil aggregates in a red soil hilly land of subtropical China

“…In China, forest plantation area increased to 69.33 million ha in 2014, becoming the largest around the world according to the data of the eighth national forest resources inventory (www.xinhuanet.com/zhibo/20140225a/zhibo.htm). Although these numbers are impressive, the quality of forest establishment, rather than just the acreage, is critical to meet growing environmental, social, and economic demands on a finite land base (Tang et al 2010).…”

Influence of terrain attributes and soil properties on soil aggregate stability

“…A decrease of aggregates stability is evident in the exposed parts of the slope, mainly due to the intensive soil organic carbon removal and subsoil exposing. Tang et al (2010) demonstrated a significant difference of the WSA index between the shoulder and toe slope positions, the WSA at the toe slope being significantly higher than that at the shoulder slope. The result was explained by the fact that the small-sized water stable aggregates displaced at the shoulder slope, transported by surface flow, and redeposited at the toe slope accelerated the development of WSA at the toe slope location.…”

“…Most of the studies emphasise the relation between organic carbon, soil erosion, and, the role of the soil aggregation in organic carbon protection in depression areas (Six et al 2004;Berhe et al 2007;Yadav & Malanson 2007). Nevertheless, the studies on the soil aggregate stability spatial distribution and its relationship with topography are rather rare and focused more on the assessment of soil aggregate stability in different parts of the slope system (Rhoton et al 2006;Tang et al 2010) than on their direct relationship with topographic derivatives (Cantón et al 2009). …”