Does the fertile island effect in tamarisk nebkhas enhance in the northern Tarim Basin in the context of global warming?

With the intensification of global warming, uncertainty regarding ecosystem evolution trends in drylands has increased. The objective of this article was to test whether the desertification process of tamarisk shrubland was intensified by comparing fertile island effects and soil ecological stoichiometry characteristics at different time periods. The tamarisk shrubland in the shrubland and shrub duneland stages in the northern Tarim Basin was selected, and soil samples were collected from the tamarisk nabkhas and from the interspaces between tamarisk nebkhas at the 0- to 30-cm soil layers in 2009 and 2018. Soil carbon (C), nitrogen (N), and phosphorous (P) were analyzed, and the C/N, C/P, and N/P ratios were calculated. In comparison with 2009, fertile island effects were completely collapsed in the shrub duneland stage, with no obvious changes in the shrubland stage in 2018. The average soil C/N ratio decreased from a value greater than 25 in both stages. The average value of soil C/P ratio was below 200 in the shrubland and shrub duneland stages, with almost no marked change after nine years. The soil N/P ratio in our study significantly increased in 2018 than in 2009, but the soil N/P ratio was still much less than 11.9. Significantly positive correlations were observed between the relative interaction index (RII) of soil organic carbon (SOC) and soil total nitrogen (TN) and the soil C/P and N/P ratios in the tamarisk nebkhas. These results suggested that (1) fertile island effects were positive in relation to soil stoichiometry in tamarisk nebkhas in most cases; (2) the desertification process was accelerated in the shrub duneland stage, with no obvious progress during the shrubland stage; and (3) the loss of soil C from the collapsed fertile islands could therefore accelerate global warming.

Automated summary

With the increase of global warming, the uncertainty of ecosystem evolution in drylands has also increased. The objective of this study was to test whether the desertification process of tamarisk shrubland was intensified by comparing fertile island effects and soil ecological stoichiometry characteristics at different time periods. The results showed that the fertile island effects disappeared completely in the shrub duneland stage, and the desertification process accelerated in this stage but showed no obvious progress in the shrubland stage. The loss of soil carbon may contribute to global warming.