Abstract
Long-term natural vegetation succession plays a substantial role in the accumulation and distribution of plant and soil C:N:P stoichiometry. However, how plant and soil C:N:P relationships or ratios change along with successional stages over a century in the severely eroded areas remain unclear. These were measured over a 100-year natural succession in five successional stages from annual grasses to climax forests. The results show that natural succession had significant effects on carbon (C), nitrogen (N) and phosphorous (P) concentrations in leaf-litter-soil and their ratios in severely eroded areas. Nitrogen concentrations and N:P ratios in leaf and litter increased from annual grasses to the shrub stage and then decreased in the late successional forest stages. Leaf P levels decreased from annual grasses to shrub stages and did not significantly change during late successional stages. Litter P concentration decreased in the early successional stages and increased during late successional stages, with no overall significant change. Soil C and N concentrations and C:N, C:P and N:P ratios increased with successional stages. Soil C and N concentrations decreased with the increasing soil depth. Both were significantly different between any successional stages and controls (cropland) in the upper 10 cm and 10–20 cm soil layers. Leaf N:P ratios may be used to indicate nutrient limitations and this study suggests that plant growth during the grass stages was limited by N, during the shrub stage, by P, and during the forest stages, by both of N and P. In addition, there were close correlations between litter and leaf C:N:P ratios, soil and litter C and N levels, and C:P and N:P ratios. These results show that long-term natural vegetation succession is effective in restoring degraded soil properties and improving soil fertility, and provide insights into C:N:P relationships of leaf, litter and soil influenced by vegetation succession stage.
Highlights
Degradation of the environment seriously affects human survival and the sustainable development of social economies (Roberts et al 2009), and is of concern worldwide
Leaf N:P ratios may be used to indicate nutrient limitations and this study suggests that plant growth during the grass stages was limited by N, during the shrub stage, by P, and during the forest stages, by both of N and P
Leaf C concentrations increased with successional stage, and in the 75-year-old pioneer forest stage, leaf C was significantly higher than in other stages
Summary
Degradation of the environment seriously affects human survival and the sustainable development of social economies (Roberts et al 2009), and is of concern worldwide. Site restoration, including natural successional and afforestation approaches, is an effective measure to control soil erosion, address ecological degradation, improve environmental quality, and achieve sustainability in ecosystems (Garcia et al 2002; Zheng 2006; Frouz et al 2008; Jiao et al 2012; Deng et al 2013; Zhao et al 2015). Zheng stages, which include grass stages, shrub stages and forest stages, enhance plant diversity and community structure (Letcher 2010), alter plant traits in species (Navas et al 2010), improve soil nutrient concentrations (Davidson et al 2007), recover soil caused by erosion (Frouz et al 2008), increase soil carbon storage (Zhang and Shangguan 2016), and maintain soil fertility (Deng et al 2013). Understanding the impacts of natural succession on plant and soil nutrients in severely eroded soils is of considerable importance for improving ecological function and providing guidance for reconstruction and rehabilitation of degraded ecological systems
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