Analysis study on the change of orchard area in Alar reclamation in the past 30 years

Monitoring the change of orchard area is important for the comprehensive management of regional ecological environment, land resource planning and macro-control of orchard area. Based on a total of 30 scenes of Landsat remote sensing images in Alar (Alaer, Xinjiang) Reclamation Area during 1990-2019, a reasonable classification system was established, and the support vector machine classification method was applied to analyze the change characteristics of orchards in Reclamation Area from 3 aspects: area change, type transformation and spatial dynamic change. The results show that (1) The UA and PA of the reclaimed orchards reach 95.28 and 97.69, respectively, and the overall accuracy reaches 87.97, and the classified results can meet the mapping requirements. (2) From 1990 to 2019, the area of orchards in Alar Reclamation showed a trend of continuous increase. It increased from 417.57 km² (10.17%) in 1990 to 1091.76 km² (26.59%) in 2019, with the largest average annual rate of change of 6.04% in the orchard area from 1990 to 1995. The continuous expansion of orchard areas has intensified water-use conflicts and exacerbated soil salinization, posing a threat to the long-term sustainability of the oasis ecosystem. (3) During the 30-year period, a total of 860.38 km² of orchard area was transferred out, mainly into arable land, and the spatial distribution area was mainly along the Tarim River; a total of 1,534.58 km² of orchard area was transferred in, mainly from unused land, and the spatial distribution area was in the northwest of the reclamation area.