Spatial-Temporal Variation Characteristics of NPP in the Heihe River Basin, Northwestern China, in a Recent 10-Year Period Calculated by CASA Model.

Liu, W.; Feng, Q., and Zhang, F., 2017. Spatial-temporal variation characteristics of NPP in the Heihe River basin, Northwestern China, in a recent 10-year period calculated by CASA model. In: Zhi, Y. and Guido Aldana, P.A. (eds.), Sustainability of Water Resources and the Development of Coastal Environments: Select Proceedings from the 2016 International Conference on Water Resource and Environment (WRE2016). Journal of Coastal Research, Special Issue No. 80, pp. 36-47. Coconut Creek (Florida), ISSN 0749-0208. In this paper, the spatial-temporal variation characteristics of NPP and related factors in the Heihe River basin were analyzed using the meteorological data of the Heihe River basin, SPOT/NDVI data, and other modified mathematical statistical methods. The results show that during the 1999-2010 period the total NPP in the Heihe River basin exhibited a fluctuating increasing trend, reaching 0.3×10¹² gC/a. The multiyear variation value of NPP was 0.19~601.09 gC/m²/a in the whole basin, 3.5 gC/m²/a in the upper reaches, 2.06 gC/m²/a in the middle reaches, and 0.31 g/m²/a in the lower reaches. The NPP of vegetation in the Heihe River basin during January and February tended to slightly decrease, and on average varied between −0.01 and −0.02 gC/m²/a, while in June, July, August, and September greatly increased. The NPP of 10 vegetation types exhibited an increasing trend in 2010 compared to 1999, on average increased by 21.02 gC/m²/a. Among various vegetation types the increase in the NPP value of swamp vegetation was the largest, reaching 46.24 gC/m²/a followed by planted vegetation, steppe types, and meadow types; there values were 39.22 gC/m²/a, 32.49 gC/m²/a, and 27.63 gC/m²/a, respectively. The accumulated NPP in grassland ecosystem in the Heihe River basin was the largest, which is of important significance to the eco-environment of the basin. As viewed for the whole Heihe River basin, the yearly mean cumulative value of NPP of vegetation was negatively related to annual mean temperature and annual total solar radiation but positively related to annual total precipitation, suggesting that water is a limiting factor to the NPP in the Heihe River basin. [ABSTRACT FROM AUTHOR]