Effects of land use changes on the groundwater table and the decline of Pinus sylvestris var. mongolica plantations in southern Horqin Sandy Land, Northeast China

Abstract Since the Three-North Shelter Forest Program was launched in 1978, more than 3.0 × 10 5  ha of Mongolian pine ( Pinus sylvestris var. mongolica , MP) plantations have been introduced to control erosion in sandy areas. However, MP plantations in the earliest introduction area (Zhanggutai region in Horqin Sandy Land, which dates back to 1954) declined at the beginning of the 1990s. Meanwhile, a linear decrease in the groundwater table was found during the years 1953–2009. This gave rise to concerns regarding the influence of introduced MP plantations on the environment. To clarify the relationships between land use changes, the decrease in the groundwater table, and the decline of MP plantations, land use changes from 1953 to 2009 were explored using remote sensing data, and the levels of water consumption associated with different types of land use were estimated using a modified CROPWAT model. The results showed that during the period 1953–2009, the area of bare sandy land in the study region sharply decreased by 89.7%. Agricultural land and broadleaved forests were the two major consumers of water resources, accounting for more than 40.0 and 20.0% of the total water consumption, respectively. MP plantations, in contrast, accounted for only about 12.0% of the total water consumption. The establishment of MP plantations has played a significant role in controlling the expansion of sandy land. Compared with agricultural land and broadleaved forests, MP plantations contribute less to the decrease in the groundwater table. The decline of the MP plantations may be a result of the decrease in available groundwater, but the MP plantations contributed less than expected to this decrease. To ensure a sustainable water balance, the area of agricultural land and broadleaved forests should be maintained below the maximum that can be supported by the guaranteed water resource.