Soil Carbon Storage Characteristics of Alfalfa ( Medicago sativa ) Artificial Grasslands in the Semi-Arid Hilly Gully Re
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oil Carbon Storage Characteristics of Alfalfa (Medicago sativa) Artificial Grasslands in the Semi-Arid Hilly Gully Region of the Loess Plateau, China Bo Jia, b, c, Zhanjun Wangb, c, Zhanbing Panb, c, Hao Xub, c, Xin-sheng Hanb, c, and Yingzhong Xied, * aSchool
of Agriculture Ningxia University, Yin Chuan, 750021 China Institute of Desert Management, Ningxia Agriculture and Forestry Science Academy, Yin Chuan, 750002 China c Key Laboratory of Desertification Control and Soil & Water Conservation of Ningxia, Yinchuan, 750002 China d Ningxia University, Yin Chuan, 750021 China *e-mail: [email protected]
b
Received September 23, 2019; revised December 3, 2019; accepted February 25, 2020
Abstract—Seven artificial alfalfa grasslands (aged 3, 5, 6, 7, 8, 11, 12 a) and an abandoned land plot were selected to examine the changes in soil organic carbon content, active organic carbon content, soil organic carbon storage and active organic carbon storage in the 0–200 cm soil layer and their correlation with soil nutrients, soil water content, soil bulk density, alfalfa cover, density, height and aboveground biomass. The results show that the soil organic carbon content was between 2.02 and 4.54 g kg–1 within depths of 0–200 cm, which was higher than that in the abandoned land. The soil organic carbon storage in the 0–40 cm layers accounted for, on average, 29.50 ± 7.13% of the total storage in the 0–200 cm soil layers in the 7-year-old alfalfa grasslands and the abandoned land, and the 0–40 cm layer was the main layer of soil organic carbon storage. The soil organic carbon storage in 12 a grassland was the highest, and the abandoned land had the smallest reserve, with values of 10.22 and 5.06 kg m–2, respectively. In addition, carbon storage was, on average, 1.84 kg m–2 higher in 7-year alfalfa artificial grassland than in abandoned farmland. The proportion of soil AOC storage to SOC storage ranged from 30.24 to 58.11%; the proportion in 5-year grassland was the lowest, while it was the highest in the abandoned land. SOC storage had significant positive correlations with TN and soil active organic carbon storage, and it had negative correlations with soil bulk density at the 0.01 level (p < 0.01). Keywords: Alfalfa, Soil organic carbon, Active organic carbon, Space-for-time method DOI: 10.1134/S1067413620050045
INTRODUCTION The semi-arid hilly gully region of the Loess Plateau is located in northwestern China and has gullies and a fragmented topography. Because of the influences of the geographic environment, climate and excessive anthropogenic effects for thousands of years, this area has been one of the most vulnerable areas in China for a long time [1, 2]. Therefore, to reduce soil erosion, restore vegetation and improve environmental quality and ecosystem stability, the government has implemented the “returning farmlands to forests or grasslands’’ program in the Loess Plateau [2, 4]. Alfalfa (Medicago sativa L.), as the most popular perennial herb, is widely planted in this region to achieve the government’s environmenta
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