Effect of Nitrogen Application on the Sensitivity of Desert Shrub Community Productivity to Precipitation in Central Asia

Abstract

Precipitation variability and nitrogen (N) deposition caused by anthropogenic activities could profoundly impact ecosystem productivity and carbon cycling. In desert ecosystems, vegetation is sensitive to changes in precipitation and N deposition. However, the impacts of large changes in precipitation, especially with a concurrent increase in N content, on plant community remain unclear. In this study, we carried out experiments to monitor the impacts of five precipitation levels and two N levels on the plant community function and composition from the Junggar desert in Central Asia during the period 2018–2019. Our results showed that: (1) Aboveground net primary production (ANPP) significantly increased with increasing precipitation, it followed a positive linear model under normal precipitation range, and nonlinear mode under extreme precipitation events; (2) N application led to an increase in ANPP, but did not significantly improve the sensitivity of ANPP to precipitation change; (3) Changes in N content and precipitation, and their impacts on ANPP were mainly driven by plant density. These results provide a theoretical basis for predict the future dynamics of terrestrial vegetation more accurately under climate change and increasing nitrogen deposition.

Multi-Temporal and Time-Lag Responses of Terrestrial Net Ecosystem Productivity to Extreme Climate from 1981 to 2019 in China

“…Precipitation is an essential factor that impacts the productivity of shrubs, and during the early growth season, there was a positive correlation between shrub NEP and extreme precipitation (Rx1day, Rx5day) (Table 3). The significant correlation occurred because extreme precipitation during this crucial period increases soil moisture, promotes plant growth, enhances species diversity and plant density, and ultimately leads to an increase in NEP [72,73]. Similar results have been observed in the Mediterranean region of southern Spain and the semi-arid shrubs of the southwestern United States, where the increase in species diversity leads to an increase in community productivity.…”

“…During the late growth season (summer and autumn), shrubs in desert areas have restricted plant stomatal conductance and photosynthetic rates due to the lack of necessary nitrogen elements. Extreme precipitation during this period may result in flooding, nutrient loss, and soil erosion, but have no apparent correlation with NEP [13,73]. Studies have shown that grasslands and shrubs have similar distribution areas and only have a significant positive correlation with Rx1day and Rx5day in summer (mid-growth season) in arid and semi-arid regions of China.…”