Effects of land‐use changes on soil organic nitrogen fractions in the black soil region of Northeast China

Abstract

Soil organic nitrogen (SON) accounts for more than 90% of the total nitrogen (TN) in black soil and is one of the most important indicators of soil fertility.However, the effect of land-use changes on SON fractions is still unclear in black soil. Hence, natural grassland (uncultivated), farmland (converted from natural grassland), and artificial forestland (grain plots converted into forests) in the black soil region of Northeast China were selected for research. TN, available nitrogen (AN) and SON fractions (ammonia nitrogen (AMN), amino acid nitrogen (AAN), hydrolysable unknown nitrogen (HUN), acid insoluble nitrogen (AIN)) in the topsoil (0-20 cm), and subsoil (20-40 cm) were analysed and compared with elucidate the effects of land-use changes on SON fractions. The results showed that compared with natural grasslands, the contents of TN and

Investigating the Soil Wind Erosion in the Black Soil Region of Northeast China Based on ¹³⁷Cs Tracer Method

“…The mean wind erosion rate in this study area was 8.60 t•hm -2 a -1 by the 137 Cs method, with an overall distribution between 7.17-10.03 t•hm -2 a -1 , which is consistent with the results of Wang et al [73] of wind erosion rates of 6.31-11.55 t•hm -2 a -1 at the tops of two gently sloping hilltops in the black soil region of Northeast China. This result is very close to Wei's measurement of erosion rate ≤8.4t hm -2 a -1 using the 137 Cs method on a flat mountaintop near the study area [74], Due to the fact that the black soil area in Northeast China has always been considered to be dominated by water erosion and freeze-thaw erosion, the 137 Cs method is mainly used to trace erosion at the slope and watershed scales in this area [48,49]. The 137 Cs method is rarely used to directly track wind erosion in mountaintop study areas.…”

“…Amini et al [37] have investigated the amount of sediment of Holocene in Gorgan gulf and southeastern coast of the Caspian Sea. In China, the impact of 137 Cs tracer technology on soil erosion has been studied since the 1980s, and the study area has been extended from the Qinghai-Tibetan Plateau region [38][39][40] to the Yangtze River Basin [41,42], the Southern Red Loam region [43], the Loess Plateau region [44], the Northwestern Sandy Wind region [45,46], the Rocky Desertification region [47,48], and the Northeastern Black Soil region [49,50], and the land use has involved forested land [51], grassland [25], sandy land [52], cropland [20], and many other land use types. It involves many land use types such as forestland [51], grassland [25], sandy land [52], and cropland [20].…”

Trends in Research on Soil Organic Nitrogen over the Past 20 Years

“…Soil nitrogen reserves in ecosystems usually account for more than 90% of the entire ecosystem nitrogen reserves [7], and 92-98% of the nitrogen in soil is in the form of organic nitrogen [13]. Soil organic nitrogen (SON) is transformed into inorganic nitrogen available to plants through microbial mineralization [14], which affects vegetation productivity and is the main limiting source of productivity of many terrestrial ecosystems [6,15]. The turnover change [16], occurrence state, and chemical form of soil organic nitrogen have an important effect on soil nitrogen sequestration [17,18] and play an important role in understanding the nitrogen cycle mechanism of an ecosystem [19] and improving ecosystem stability and productivity [20,21].…”