Tidal creeks mediate micro-climate within artificial mangroves at their northmost boundary in China

Abstract

One of the primary constraints for mangrove restoration is the low temperature in relatively high latitude regions. Yueqing Bay, at a latitude of 28.20°N, is the northmost region for the artificial mangrove forests in China. It is hypothesized that in this region, the micro-climate nearby tidal creeks can benefit the growth of mangroves, as the inundation process can mediate air temperature and soil temperature. To test this hypothesis, field observation was conducted to measure mangrove characteristics, hydrology and air/soil temperature within a channelised mangrove forest and compare variations between a tidal creek and its adjacent platform. LiDAR data and field measurement both indicated a height decrease of mangrove trees (Kandelia obovata) from the tidal creek edge to the platform. This pattern suggested that the presence of tidal creeks was able to promote the growth of mangrove in their northmost boundary and the mediation of microclimatic condition should be further investigated. The temperature profile data revealed that the key zone of temperature affected by tidal inundation was within a range of 5 cm and -15 cm referring to bed levels. Temperature monitoring in the winter revealed that compared with the platform, a mean increase of 0.6 °C in both air temperature and soil temperature were found in the tidal creek. However, spring tides and neap tides showed different effects on temperature mediation by the presence of tidal creeks. The greatest temperature increase was observed to occur in neap tides, reaching maximum of 9 °C in air and 3 °C in soil. Thus, the warming effects of tidal creeks in this region was most important in neap tides. In the northmost boundary of mangrove distribution in China, winter low temperature was considered to be the key restraint for mangrove restoration. Field survey found the growth of mangroves reached a maximal along the tidal creek edge in this region. This pattern was explained by the fact that the presence of tidal creeks increased winter temperature of mangroves and channelisation was found to be a potential technique to promote the growth of artificial mangroves in the relatively high latitude regions.