|Other Abstract||The construction of Taklimakan desert highway shelterbelt improves soil texture and nutrient content significantly, at the same time, saline water irrigation and the biological salt accumulation of halophytes lead to some negative effects on soil quality. In this study, soil texture, nutrients and salinity’s spatial distribution characteristics and how they affected by shelterbelt structure were studied in field scale. The characteristics of soil salt and ions’ distribution under different mineralization degrees of saline water drip-irrigation along the road were discussed in detail. Main conclusions were as follows:
(1)Before the shelterbelt was built, soil texture was dominated by sand, the contents of clay and silt were few, the content of soil fertility was low, the salt content was less, pH appeared weakly alkaline. By comparison, after the shelterbelt was built, there were increments in soil particulate matter, nutrient content, salinization processes, the salt crust development and aggravation of soil alkalinity. The effects of the sheltrebelt construction and saline water irrigation on 0~10cm soil layer were the severest.With the increase of soil depth, fine material, nutrient and salt content decreased and stabilized.
(2)Soil properties exhibited different degrees of variability in the space. Coefficient variation of clay, silt, sand, TP, TK and pH were small, their content in the soil were relatively stable, while, coefficient variation of SOM, TN, AP, AK and EC were larger. EC and TN appeared a banded structure in space, other indexes mostly showed a patchy distribution. Affected by topography of the study area, soil texture and nutrient both appeared a second-order trend that in south-north direction.
(3)Soil properties were different at different positions on the shelterbelt system. Soil particulate matter showed a regular that falling-sand belt more than fixation-sand belt and more than that of resistive-sand belt and quicksand; the content of TN, EC and pH in understory were higher than that in forest and quicksand; TK was affected greatly by the mineral composition of the parent material, thus, falling-sand belts
contain more clay and its TK content was the highest; except for TN and TK, the rest of the nutrient content showed fixation-sand belt> falling-sand belt > resistive-sand belt> quicksand.
(4)Irrigation water was the main way of soil salt input, soil salinity increased with increasing irrigation water salinity levels, salt ran into the surface soil intensely, soil crust highly developed; affected by the irrigation water, each ion content had different degrees of increase compared to quicksand, soil salinity composition was dominated from Cl-, Na+, HCO3- to Cl-, Na+ and SO42- after irrigation; different salt ions had different chemical properties, and their abilities to combine with soil colloids were different, so the process of salt ions leaching to subsoil existed heterogeneities, the distribution characteristics of different salt ions in soil profiles were different.|