A Critical Analysis of the Function of Soil Nitrogen for the Boreal Forest Conifers

Abstract

The most crucial component for plant development and sustenance is thought to be nitrogen. Its availability and function for conifers in boreal forests are still up for discussion, though. Boreal conifers have changed their tactics to deal with the decreased amount of nitrogen available. Boreal conifer roots are linked to ECM fungi, which promote soil exploration and N nutrition, particularly in areas with a high proportion of organic N. While estimates of nitrate uptake are often lower, conifers typically absorb ammonium at amounts similar to simple organic N, which likely becomes more significant as organic matter builds up with stand age. Conifers may depend on internal N cycling to support the growth of new tissues in the spring, particularly slow-growing species. N promotes growth and wood development by increasing photosynthesis and leaf area, which mostly results in greater earlywood production and broader radial rings. The growth of boreal forests may be impacted by N-depositions and disturbances (such as fire and harvest) that change the soil N-cycle. The expansion of boreal forests over the past century is thought to have been caused by N depositions. High N-depositions and intensive harvesting may cause N to become less abundant than other elements (e.g. P, K, and B). Through a variety of intricate processes, such as altered fire return intervals, direct impacts of warmer soils on N mineralization, and the stimulation of plant growth, climate change should alter the balance between N stored in soils and in living and dead (such as wood) biomass. Future studies should aim to deepen our knowledge of the potential effects of shifting disturbance regimes, N-depositions, and climate. These studies should focus on the role of mosses in fixing nitrogen, canopy N uptake, and conifers' reactions to shifting microbial (symbiotic and non-symbiotic) communities.