Freeze-thaw cycles alter the growth sprouting strategy of wetland plants by promoting denitrification

Sprouting and early growth of plants in wetlands can be inhibited by freeze-thaw cycles via denitrification and reduction of soil nitrogen, according to a temperature-controlled experiment in the Momoge wetland in China. Freeze-thaw cycles exert an important abiotic stress on plants at the beginning of winter and spring in mid-to-high latitudes. Here, we investigate whether the effects of freeze-thaw cycles are carried over into the growing season in wetlands. We conduct a temperature-controlled experiment under two freeze-thaw and two flooding conditions on a typical plant (Scirpus planiculmis) and soil from the Momoge wetland (China) and analyze the microbial nitrogen metabolism, based on metagenomic sequencing. We show that freeze-thaw cycles earlier in the year significantly inhibit plant sprouting and early growth. Specifically, they promote denitrification and thus reduce nitrogen levels, which in turn intensifies nitrogen limitation in the wetland soil. We find that plants tend to sprout later but faster after they are exposed to freeze-thaw cycles. Wetland flooding could alleviate these medium-term effects of freeze-thaw cycles. Our results suggest that wetland plants in mid-to-high latitudes have evolved sprouting and growth strategies to adapt to climatic conditions at the beginning of winter and spring.

Automated summary

The sprouting and early growth of wetland plants in China can be inhibited by freeze-thaw cycles, which reduce soil nitrogen through denitrification. Experimental results suggest that these cycles are an important abiotic stress on plants in mid-to-high latitudes during the beginning of winter and spring. Flooding in wetlands can alleviate the medium-term effects of freeze-thaw cycles.