Soil NH4 +/NO3 − nitrogen characteristics in primary forests and the adaptability of some coniferous species

Abstract

In terrestrial ecosystems, soil nutrient regimes at a plant's living site generally represent the plant's "nutrition habitat". Plant species frequently well adapt to their original "nutrition habitat" during a long process of evolution, and the apparent preference for ammonium or nitrate nitrogen source (NH 4 + or NO 3 -) might be an important aspect of the adaptation. Plants typically favor the nitrogen form most abundant in their natural habitats. Nitrate has been recognized as the dominant mineral nitrogen form in most agricultural soils and the main nitrogen source for crops, but it is not usually the case in forest ecosystems. A large number of studies show that the "nutrition habitats" associated with primary forest soils are typically dominated by NH 4 + rather than NO 3 -, generally with NO 3 -content much lower than NH 4 + . Low levels of NO 3 -in these forest soils generally correspond to low net rates of nitrification. The probable reasons for this phenomenon include: 1) nitrification limitations and/or inhibitions caused by lower pH, lower NH 4 + availability (autotrophic nitrifiers cannot successfully compete for NH 4 + with heterotrophic organisms and plants), or allelopathic inhibitors (tannins or higher-molecular-weight proanthocyanidins) in the soil; or 2) substantial microbial acquisition of nitrate in the soils, which makes net nitrification rates substantially less than gross nitrification rates even though the latter are relatively high.Many coniferous species (especially such late successional tree species as Tsuga heterophylla, Pinus banksiana, Picea glauca, Pseudotsuga meziesii, Picea abies, etc.) fully adapt to their original NH 4 + -dominated "nutrition habitats" so that their capacities of absorbing and using non-reduced forms of nitrogen (e.g., NO 3 -) substantially decrease. These conifers typically show distinct preference to NH 4 + and reduced growth due to nitrogen-metabolism disorder when NO 3 -is the main nitrogen source. The physiological and biochemical mechanisms that account for the adaptation to NH 4 + -dominated systems (or limited ability to use NO 3 -) for the coniferous species include: i) distribution and activity of enzymes for catalyzing nitrogen reduction and assimilation, generally characterized by lower nitrate reductase (NR); ii) greater tolerance to NH 4 + or rapid detoxification of ammonium nitrogen in the roots; iii) lower capacity of absorption to NO 3 -by roots that might be controlled by feedback regulations of certain N-transport compounds, such as glutamine; iv) relations and balance between nitrogen and other elements (such as Ca 2+ , Mg 2+ , and Zn 2+ etc.). Some NH 4 + -preferred conifers might be more adapted (tolerant) to lower base cation conditions; v) NO 3 -nutrition, rather than NH 4 + , that may lead to the loss of considerable quantities of organic and inorganic carbon to the surrounding media and mycorrhizal symbiont and probably contribute to slower growth; and vi) the metabolic cost of reducing NO 3 -to NH 4 + that may make shade-tolerant c...

The effects of nitrogen addition on the growth of two exotic and two native forest understory plants

“…For example, if nitrate (NO 3 -), a highly mobile anion that is present when conditions favor nitrifying bacteria, is relatively more abundant than ammonium (NH 4 ? ), a less mobile cation associated with acidic soils, plant species that preferentially respond to increases or fluctuations in nitrate may be favored (Roper and Ophel-Keller 1997;Davis et al 2000;Green and Galatowitsch 2001;Wardle 2002;Daehler 2003;Cui and Song 2007). A favorable response to one form of nitrogen over another may help to explain the dominance of many invasive plants.…”

“…(Marschner 1986;Claussen and Lenz 1999;Aerts and Chapin 2000;Gilliam 2006;Cui and Song 2007;Miller et al 2007). Some plants have been shown to prefer the uptake of a single form of inorganic nitrogen while others do not differentiate (Kronzucker et al 1995;Kronzucker et al 1997;Miller and Bowman 2002;Fang et al 2007).…”

“…Some plants have been shown to prefer the uptake of a single form of inorganic nitrogen while others do not differentiate (Kronzucker et al 1995;Kronzucker et al 1997;Miller and Bowman 2002;Fang et al 2007). In N-limited systems, differential uptake of nitrogen by co-occurring species depends on the type of nitrogen nutrition available (Claussen and Lenz 1999;Cui and Song 2007). In general, species inhabiting acidic soils where nitrification is reduced, more readily take up ammonium, whereas plants that have adapted to higher pH soils preferentially utilize nitrate (Marschner 1986;Aerts and Chapin 2000;Nordin et al 2005;Cui and Song 2007).…”

“…In N-limited systems, differential uptake of nitrogen by co-occurring species depends on the type of nitrogen nutrition available (Claussen and Lenz 1999;Cui and Song 2007). In general, species inhabiting acidic soils where nitrification is reduced, more readily take up ammonium, whereas plants that have adapted to higher pH soils preferentially utilize nitrate (Marschner 1986;Aerts and Chapin 2000;Nordin et al 2005;Cui and Song 2007). Native understory vegetation that evolved in N-limited systems with primarily ammonium-based nutrition may not be able to utilize nitrate as effectively as species that can either utilize both forms or preferentially uptake nitrate (Marschner 1986;Vitousek and Walker 1989;Bobbink et al 1998;Aerts 1999;Miller and Bowman 2002;Lowe et al 2003;Burns et al 2007).…”

To what extend can soil moisture and soil contamination stresses affect greenhouse gas emissions? An attempt to calibrate a nitrification/denitrification model

“…Also, our modeling approach of N-N2O, N-N2 and N-NOx production in the contaminated context could have been more constrained with measurement of denitrification rate to assess the effect of Cu on proportion of production and consumption of N-NO3 Based on our simulations, the soil Cu contamination wass expected to substantially modify the proportion 425 of available N in soils with the increase in N-NH4 stock at the expense of N-NO3. N-NH4 accumulation and the large expected decrease in N-NO3/N-NH4 ratio in contaminated soils (around 50% for the 60% WHC) may lead to shift in plant community structures with different preferences in N assimilation(Peacock et al 2001;Cui and Song 2007). Therefore, Cu stress could not only have implications in microbial community patterns as a stressor,https://doi.org/10.5194/bg-2021-265 Preprint.…”