ObjectiveOur objective here was to rapidly and accurately obtain long-term continuous LAI for Artemisia ordosica communities in the Mu Us Desert of northwestern China, which is of great importance for understanding the relationship between ecosystem processes and environmental changes.

MethodWe measured LAI in a typical A. ordosica community using the LAI-2000 canopy analyzer (LI-COR, USA) from April to October in the growing season of 2013 and 2014, and obtained MODIS NDVI (NDVI_MODIS) data for the same periods. Ground-based NDVI (NDVI_ground) was calculated from incident and reflected solar radiation and photosynthetically active radiation, which were measured by radiation sensors mounted on a tower in the center of the community. LAI measurements were used to examine seasonal changes and construct LAI models. Normalized effective accumulated temperature, NDVI_ground and NDVI_MODIS were used to construct optimal LAI model for the community.

ResultThe seasonal dynamics was consistent with the phenophases of A. ordosica and showed a hump-shaped pattern. LAI increased from April to late August, reached a peak in August (1.09 and 1.33m²/m² in 2013 and 2014, respectively), remained relatively stable from early September to mid-September, and rapidly declined from late September due to the defoliation of A. ordosica. The optimal LAI model was NDVI_ground (R²=0.76, P < 0.01).

ConclusionOur results indicate that long-term continuous LAI estimates for A. ordosica communities in the Mu Us Desert can be easily obtained using NDVI measurements and the model. The model can be used to understand and predict ecological impacts of climate change.