Soil aggregation and intra-aggregate carbon fractions in relation to vegetation succession on the Loess Plateau, China

Abstract. Vegetation restoration was effective way of protecting soil erosion and water conservation on the Loess Plateau. Carbon fractions and enzyme activities were sensitive parameters for assessment of soil remediation through revegetation. Forest, forest steppe and grassland soils were collected at 0–5 cm and 5–20 cm soil layers in Yanhe watershed, Shaanxi Province. Urease, sucrase, alkaline phosphatase, soil organic carbon (SOC), microbial biomass carbon (MBC), easily oxidized organic carbon (EOC) and dissolved organic carbon (DOC) were measured. The results showed that carbon fraction contents and enzyme activities in the same soil layer followed the order that forest was higher than others. Carbon fraction contents and enzyme activities appeared that the 0–5 cm was higher than 5–20 cm soil layer. In addition, correlation analysis showed that urease activity was related to SOC, MBC, EOC and DOC at 0–5 cm layer; it was correlated with SOC, MBC and EOC at 5–20 cm layer. Sucrase activity had significant positive relationship with SOC, MBC and EOC. Alkaline phosphatase activity was related to EOC and DOC at 0–5 cm layer; it was correlated with MBC and EOC at 5–20 cm layer. The CCA reflected the relationship between sucrase activity and SOC. The contributions from the various forms of carbon fractions and enzyme activities as evaluated by the canonical coefficient of CV were on the order of SOC > DOC > MBC > EOC; sucrase > urease > alkaline phosphatase. Vegetation type was an important factor influencing the variation of soil enzyme activities and carbon fractions on the Loess Plateau.

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Identification of the important environmental factors influencing natural vegetation succession following cropland abandonment on the Loess Plateau, China

PeerJ ◽

10.7717/peerj.10349 ◽

2020 ◽

Vol 8 ◽

pp. e10349

Author(s):

Zhenguo Zhang ◽

Mingming Wang ◽

Jikai Liu ◽

Xinwei Li

Keyword(s):

Loess Plateau ◽

Correspondence Analysis ◽

Classification Tree ◽

Detrended Correspondence Analysis ◽

Vegetation Succession ◽

Natural Vegetation ◽

Vegetation Types ◽

The Loess Plateau ◽

Cropland Abandonment

Identification of typical vegetation succession types and their important influencing factors is an important prerequisite to implement differential vegetation and soil management after land abandonment on the Loess Plateau, China. However, there is no reported study specifically on the identification of vegetation types and their important factors as well as the thresholds of the important factors for classification of the vegetation types, based on the medium- to long-term succession of natural vegetation after cropland abandonment. We collected vegetation and soil data on the natural vegetation with the longest 60-year-old forest communities that developed after cropland abandonment and analyzed the data using two-way indicator species analysis, detrended correspondence analysis, direct canonical correspondence analysis and classification tree model. The vegetation communities were classified into five distinct vegetation types, including Artemisia scoparia, Lespedeza davurica and Stipa bungeana, Artemisia giraldii pamp, Sophora viciifolia, Quercus liaotungensis and Biota orientalis. The years after cropland abandonment and soil C/N were further identified as important factors determining the types of vegetation. Likewise, it was observed that most of the investigated soil nutrient variables and soil texture-related variables improved with the vegetation succession while soil water in the surface layers showed a decreasing trend. These findings may provide an ecological basis for site-specific management of vegetation types after cropland abandonment in the medium-long term on the Loess Plateau. Our results encourage further exploration of vegetation succession and their important factors based on longer periods of vegetation succession after cropland abandonment under more soil and climatic conditions on the mountainous areas as the Loess Plateau.

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