Enrichment of soil fertility and salinity by tamarisk in saline soils on the northern edge of the Taklamakan Desert

To better understand the influence of Tamarix spp. (tamarisk shrubs) on soil fertility and salinity and the implication for saline soil management in northwestern China, several soil physical and chemical characteristics were measured beneath tamarisk canopies from the upper, middle, and lower regions of the Taklamakan Desert alluvial plain. The measured properties included soil organic matter (SOM), plant-available phosphorus (P), extractable soil potassium (K) soil electric conductivity (EC), sodium (Na+), total potassium (K+), and pH. The enrichment ratios for soil nutrients (i.e., available P, extractable K, and SOM) and salinity (i.e., EC, Na+, K+, and pH) were used to evaluate fertility and salinity islands in tamarisk mounds. SOM, available P, and extractable K were higher within mounds than in open, tamarisk-free land in each of the three sampled locations. The SOM enrichment ratios were highest at the middle region of the alluvial plain and lowest at the lower region of the alluvial plain, a pattern that is consistent with the growth patterns of tamarisk plants. The variation in SOM enrichment ratios in surface soils was mainly affected by the shoot biomass of tamarisk shrubs. The positive effect of tamarisk on soil fertility indicates that tamarisk may be beneficial for vegetation restoration and improving utilization of saline land. Nevertheless, soil salinity and pH increased under tamarisk canopy, especially EC and K+ in surface soil from the middle alluvial plain. The EC enrichment ratio was highest in the middle alluvial plain and, depending on soil depth, lowest in the upper and lower alluvial plain. These results reflect negative effects of tamarisk on soil chemical characteristics.