Changes in soil organic carbon, nitrogen, pH and bulk density with the development of larch (Larix gmelinii) plantations in China

• Published in: Global change biology Vol. 17; no. 8; pp. 2657 - 2676
• Main Authors: WEN-JIE, WANG, LING, QIU, YUAN-GANG, ZU, DONG-XUE, SU, JING, AN, HONG-YAN, WANG, GUAN-YU, ZHENG, WEI, SUN, XI-QUAN, CHEN
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.08.2011; Wiley-Blackwell
• Subjects: Agriculture; Agronomy. Soil science and plant productions; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomass; biomass production; bulk density; Carbon; carbon sequestration; carbon sinks; chronosequences; constant mass correction; Farms; forest plantations; forest soils; Forests; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; General aspects; Generalities. Agricultural and farming systems. Agricultural development; land use; Larix; Larix gmelinii; Larix gmelinii plantations; long-term permanent plot; net ecosystem exchange; Nitrogen; planting; power analysis; returning farmland to forests; SOC accumulation; soil acidification; soil bulk density; soil fertility; soil nitrogen; soil organic carbon; soil pH; Soils; Asia; China; China, People's Rep; Bulk density; Organic carbon; chronosequences; Organic nitrogen; Forests; Plot; Farmland; constant mass correction; Long term; Accumulation; soil nitrogen; Agroecosystem; power analysis; Mass; Soils; Chronosequence; SOC accumulation; soil bulk density; soil pH; pH; Larix gmelinii plantations; long-term permanent plot; returning farmland to forests
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/j.1365-2486.2011.02447.x

Under the government of China's environmental program known as Returning Farmland To Forests (RFTF), about 28 million hectares of farmland have been converted to tree plantation. This has led to a large accumulation of biomass carbon, but less is known about underground carbon-related processes. One permanent plot (25 years of observation) and four chronosequence plot series comprising 159 plots of larch (Larix gmelinii) plantations in northeastern China were studied. Both methods found significant soil organic carbon (SOC) accumulation (96.4 g C m⁻² yr⁻¹) and bulk density decrease (5.7 mg cm⁻³ yr⁻¹) in the surface soil layer (0-20 cm), but no consistent changes in deeper layers, indicating that larch planting under the RFTF program can increase SOC storage and improve the physical properties of surface soil. Nitrogen depletion (4.1-4.3 g m⁻² yr⁻¹), soil acidification (0.007-0.022 pH units yr⁻¹) and carbon/nitrogen (C/N) ratio increase (0.16-0.46 per year) were observed in lessive soil, whereas no significant changes were found in typical dark-brown forest soil. This SOC accumulation rate (96.4 g m⁻² yr⁻¹) can take 39% of the total carbon sink capacity [net ecosystem exchange (NEE)] of larch forests in this region and the total soil carbon sequestration could be 87 Tg carbon within 20 years of plantation by approximating all larch plantations in northeastern China (4.5 Mha), showing the importance of soil carbon accumulation in the ecosystem carbon balance. By comparison with the rates of these processes in agricultural use, the RFTF program of reversing land use for agriculture will rehabilitate SOC, soil fertility and bulk density slowly (< 69% of the depletion rate in agricultural use), so that a much longer duration is needed to rehabilitate the underground function of soil via the RFTF program. Global forest plantations on abandoned farmland or function to protecting farmland are of steady growth and our findings may be important for understanding their underground carbon processes.