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Nitrogen fixation is a key factor in supporting plant growth, and new research shows that this process is greatly enhanced at high temperatures, explaining nitrogen shortages in cold climates.
Scientists from the US have studied how rising temperatures affect nitrogen fixation, a process in which certain bacteria living in symbiosis with plants absorb nitrogen from the atmosphere and convert it into a form available to plants.
– the authors of the study note. This discovery has important implications for ecology, as it indicates a possible increase in plant bioproductivity in response to global warming.
Experiments were conducted on seedlings red alder (Alnus rubra), wax myrtle (Myrica cerifera), black locust (Robinia pseudoacacia) and the tropical tree Gliricidia sepium. The researchers gradually increased the temperature under controlled conditions and measured the activity of nitrogen-fixing symbiont bacteria. It turned out that in cold climates the efficiency of this process is significantly lower, which may explain the poverty of soils in northern regions in nitrogen. In tropical latitudes, where the temperature is higher, nitrogen fixation, on the contrary, occurs more efficiently, providing a large amount of available nitrogen.
Interestingly, such temperatures were common in the Mesozoic and early Cenozoic, when symbiosis between plants and nitrogen-fixing bacteria likely developed and became established. Subsequent global cooling may have caused some plants to lose their ability to symbiotically fix nitrogen, as the process became less efficient. This finding challenges the assumption that global warming will lead to nitrogen depletion in soils, and instead suggests that its availability to plants will increase as temperatures rise.
In addition, the researchers compared the photosynthetic activity of plants at pre-industrial levels of CO2 (275 parts per million) and modern levels (400 parts per million). They found that with increased CO2, the optimal temperatures for photosynthesis also increase, meaning that plants can more efficiently absorb carbon and increase biomass in today's climate.
Thus, the new work shows that traditional models that predict future nitrogen shortages may be inaccurate. On the contrary, rising temperatures may stimulate nitrogen fixation, contributing to biomass growth even in tropical regions. This discovery could change approaches to predicting environmental changes in the context of global warming and strategies for using nitrogen fertilizers in agriculture.
