Temporal and spatial variations in the stable carbon isotope composition and carbon and nitrogen contents in current-season twigs of Tamarix chinensis Lour. and their relationships to environmental factors in the Laizhou Bay wetland in China

摘要

Coastal wetlands are highly vulnerable ecosystems exposed to tidal and storm events and soil alkalinization. Tamarix chinensis, highly adapted to flooded and salty conditions, is an important pioneer foundation species of salty riparian habitats, ensuring the ecological stability of wetlands. To better understand the physiological responses to environmental conditions across the T. chinensis community in the Laizhou Bay wetland in China, we analysed delta C-13, C and N in 108 samples of current-season twigs at three different density levels (dense, sparse and fringe) and at three different light intensities (shade, sun and top) from September 2011 to August 2012. The results showed that the delta C-13 and C changed with seasonal variations and the delta C-13, N and the C:N ratio were mainly affected by sunlight. Whereas, density levels did not affect any of the delta C-13, C, N and the C:N ratio by GLM (generalized linear model) analysis. Then the C:N ratio was correlated with C and N and no relationships existed in the delta C-13, C and N. In addition, the delta C-13, C and N contents were influenced by variations of environmental factors. delta C-13 was primarily correlated with soil salinity, air temperature and relative humidity. Air temperature, precipitation and relative humidity were the key contributors to the C content. The C:N ratio were weakly influenced by wind speed. Above all, our results provide valuable information on the eco-physiological responses of the T. chinensis community under environmental stress in wetlands. (C) 2016 Elsevier B.V. All rights reserved.