Traits and economic spectrum of different-aged leaf of Kandelia obovata in Minjiang River estuary, China.

Abstract

To elucidate the adaptive mechanisms and strategies of different-aged leaves of Kandelia obovata in response to resource limitations in the Minjiang River Estuary Wetland Nature Reserve, we measured 21 leaf functional traits from current-year and previous-year leaves, and compared the traits between the two leaf types to construct leaf economic spectrum. The results showed that the fresh and dry weight of K. obovata in the previous-year leaves was 2.3 times of current-year leaves. There was a significant difference in nitrogen (N) content, with values of 20.59 mg·g^-1 for current-year leaves and 15.88 mg·g^-1 for previous-year leaves, as well as in phosphorus (P) content, with values of 1.40 and 1.06 mg·g^-1, respectively. There was a significant positive correlation between N and P content. The net photosynthetic rate differed significantly, with values of 7.53 and 4.68 μmol·m^-2·s^-1 for current-year and previous-year leaves, respectively. There was a significant difference in stomatal conductance (0.16 vs. 0.15 mol·m^-2·s^-1). The economic spectrum indicated that current-year leaves possessed traits such as thin structure, rapid extension, high photosynthetic efficiency, low leaf tissue density, and higher N and P content, reflecting a strategy of rapid investment and return. In contrast, previous-year leaves exhibited thicker structure, slower extension, lower photosynthetic efficiency, higher leaf tissue density, and lower N and P content, adopting a more conservative and slow-investment growth strategy. These findings suggested that K. obovata employed two distinct growth strategies, adjusting leaf structure and physiological properties to enhance its survival in stressed environments.