Nitrogen Deposition May Benefit to Larix olgensis Root Soils

Abstract

Atmospheric nitrogen deposition affects the health of forest ecosystems by altering soil microbial activity. However, the effects of nitrogen addition levels, morphology and ecosystem type on whether nitrogen addition is beneficial or detrimental to soil health is controver-sial, and most studies have focused on the negative effects on microbial structure. Based on this, this study conducted a four-year experiment of nitrogen (NaNO3) addition at two levels (10 and 20 kg N hm−2·yr−1) in the understory soil of Larix olgensis in northeastern China to study soil microbial properties, soil enzyme activities, and to analyze soil physi-cochemical properties and the correlation between them. The results showed that nitrogen addition reduced soil pH and increased soil NH4+-N and NO3−-N contents, thus promoting the activities of Urease (Ure), Acid phosphatase (ACP) and N-Acetamidoglucosidase (NAG) and inhibiting the activity of Leucine aminopeptidase (LAP) in soil, further improving the diversity and richness of soil microorganisms and increasing the dominant taxa of beneficial microorganisms. This may be due to soil acidification caused by the addition of nitrogen, which increases the effectiveness of nitrogen in the soil, improving soil properties, moving soil health in a beneficial direction, promoting beneficial microbial activity, and making the soil more suitable for the growth of the acid-loving tree species L. olgensis. In general, N addition favored the development of soil bacterial communities and the maintenance of soil nutrient status, and had a positive effect on the soil nutrient status of L. olgensis. The results of this study may provide an important scientific basis for adaptive management of forest ecosystems in the context of global nitrogen deposition.