Relative contribution of environmental and nutritional variables to net primary production of Cynodon dactylon (Linn.) Pers in the riparian zone of a Three Gorges tributary

Junjie Lin; Shuang Zhou; Dan Liu; Shuai Zhang; Zhiguo Yu; Xiaoxia Yang

doi:10.1002/ece3.6409

Relative contribution of environmental and nutritional variables to net primary production of Cynodon dactylon (Linn.) Pers in the riparian zone of a Three Gorges tributary

Ecol Evol. 2020 May 25;10(14):7073-7081. doi: 10.1002/ece3.6409. eCollection 2020 Jul.

Authors

Junjie Lin¹, Shuang Zhou¹, Dan Liu², Shuai Zhang¹, Zhiguo Yu³, Xiaoxia Yang⁴

Affiliations

¹ Key Laboratory of Water Environment Evolution and Pollution Control in Three Gorges Reservoir Chongqing Three Gorges University Wanzhou China.
² Department of Agricultural and Forestry Science and Technology Chongqing Three Gorges Vocation College Chongqing China.
³ School of Hydrology and Water Resources Nanjing University of Information Science and Technology Nanjing China.
⁴ Institute of Quality Standard and Testing Technology Chongqing Academy of Agricultural Sciences Chongqing China.

Abstract

Our knowledge of fundamental drivers of terrestrial net primary production (NPP) is crucial for improving the predictability of ecosystem stability under global climate change. However, the patterns and determinants of NPP are not fully understood, especially in the riparian zone ecosystem disturbed by periodic drought-rewetting (DRW) cycles. The environmental (flooding time, pH, moisture, and clay content) and nutritional properties (soil organic carbon, total nitrogen, total phosphorus, ammonium (NH₄ ⁺-N), nitrate (NO₃ ^--N), and C:N:P stoichiometry) were investigated in the riparian zone of Pengxi River-a typical tributary of Three Gorges Reservoir (TGR). Structure equation modeling was performed to evaluate the relative importance of environmental and nutritional properties on NPP of Cynodon dactylon (Linn.) Pers (C. dactylon)-a dominating plant in the riparian zone of TGR. Our results indicated that NPP was much lower under much severe flooding stress. All of these variables could predict 46% of the NPP variance. Nutrient use efficiency (NUE) was one of the most critical predictor shaping the change of NPP. Specifically, flooding stress as a major driver had a direct positive effect on soil moisture and soil clay content. The soil clay content positively affects the soil C: N ratio, which further had an indirect negative impact on NPP by mediating NUE. Overall, our study provided a comprehensive analysis of the effects of the combined effect of environmental and nutrient factors on NPP and showed that continuous DRW cycles induced by hydrological regime stimulate the decrease of NPP of C. dactylon by changing NUE strategies. Further research is needed to explore the responses of NPP and NUE under different land use to DRW cycles and to investigate the DRW effects on the combined effect of environmental and nutrient factors by in situ experiments and long-term studies.

Keywords: Three Gorges Reservoir; Yangtze river; hydrological regime; net primary production; nutrient use efficiency; structure equation modeling.