Improvement of biochemical and biological properties of eroded red soil by artificial revegetation

Large areas of red soil in southern China are degraded due to improper management in land use change from forest to agricultural crops in 1970s, which has resulted in serious soil erosion. Since 1980s, artificial revegetation has been practiced to restore the productivity and maintain ecological functionality of red soils. Whereas numerous studies have been conducted to evaluate the effects of revegetation on soil physical and chemical properties, little information is available on soil microbial responses. The objective of this work was thus to investigate the influence of plant species and growing period on soil biochemical and biological properties. In March 2005, the field trial was set up using two historical revegetation experiments with different plant species established in 1985 (20-year) and in 1993 (12-year). The trial had six vegetation treatments with three replications. The plant species on the trial site included crenate gugertree, Chinese fir, grapefruit, and annual ryegrass. Soil samples (0-0.2 m) were taken from the trial site and analyzed for the soil total organic C (TOC), microbial biomass C (MBC), microbial biomass nitrogen (MBN), water-soluble organic C (WSOC), and mineralizable C (MC). The specific ability of soil microbiota to consume a range of C substrates was measured using Biolog ECO microplate. Soil TOC, MBC, MBN, WSOC, and MC were significantly (P a parts per thousand currency signaEuro parts per thousand 0.05) enhanced by artificial revegetation treatments. All soil parameters analyzed were improved with the revegetation time when comparing 20-year Chinese fir with 12-year Chinese fir. Soil parameters in 20-year crenate gugertree stand were significantly (P a parts per thousand currency signaEuro parts per thousand 0.05) greater than the 20-year Chinese fir. Concentrations of most C forms and MBN in soils of the 12-year ryegrass treatment were generally higher than those of the 12-year Chinese fir and grapefruit treatments. The activities of microbial communities as average well color development measured with Biolog ECO microtiter plate were in the order of 20-year crenate gugertree and 20-year Chinese fir > 12-year Chinese fir and 12-year ryegrass > 12-year grapefruit and the control. The patterns of C utilization obtained from principal component analysis showed that microbial communities from plots with various revegetation duration (20-year site vs 12-year site) separated along the first component (PC1) and with different species along the second component (PC2). Soil biochemical and biological properties were closely related to the types and amount of C source, which were influenced by plant species and revegetation time. Artificial revegetation can effectively enhance the productivity of degraded red soil caused by erosion in subtropical areas of China. The revegetation time was positively related to improvement of soil biological and biochemical properties. Plant species selection can also significantly influence the outcome of artificial revegetation. Among the species used in our study, crenate gugertree and ryegrass can enhance soil biological properties better than the other species.