Long term climatic trends in Chile and effects on soil moisture and temperature regimes

Climate change could potentially affect agricultural and forest production in Chile through changes in soil moisture and temperature regimes. In Soil Taxonomy the Soil Moisture Regime (SMR) is used to classify soils at the Suborder, Great Group and Subgroup levels, whereas Soil Temperature Regime (STR) is mainly used at the Family level. Both SMR and STR can be calculated using climatic data input to the Newhall model. Therefore, the objective of this research was to test the hypothesis that long term climate change has already affected the SMR and STR in different locations of the country. Historical values (1912-2015) of monthly precipitation and temperature were input to the model, with the available soil water set to 180 mm, and the offset of air to soil temperature set to 2 °C. The climatic records indicated a general trend of less precipitation in central and south central Chile whereby the SMR changed in Concepción from Ustic-Udic Tropustic to Ustic-Typic Tropustic; in Puerto Montt from Perudic to Udic-Typic Udic; and in Punta Arenas from Aridic-Typic Aridic to Xeric-Typic Xeric. In general, the recent period had more frequent extreme dry years. There was also a general tendency for slightly cooler temperatures mainly along the coast, and warming in Santiago, but the dominant STRs did not change between periods. Additionally, in south central Chile there was a decrease of annual moist days when the soil temperature is ≥ 5 °C, which suggests that in some areas soil temperature and moisture conditions have become somewhat more limiting over time, and, if continued, will likely result in a southerly expansion of the Xeric SMR, and increased need for supplemental irrigation of crops.