Effects of Changing Temperature on Gross N Transformation Rates in Acidic Subtropical Forest Soils

Abstract

Soil temperature change caused by global warming could affect microbial-mediated soil nitrogen (N) transformations. Gross N transformation rates can provide process-based information about abiotic–biotic relationships, but most previous studies have focused on net rates. This study aimed to investigate the responses of gross rates of soil N transformation to temperature change in a subtropical acidic coniferous forest soil. A 15N tracing experiment with a temperature gradient was carried out. The results showed that gross mineralization rate of the labile organic N pool significantly increased with increasing temperature from 5 °C to 45 °C, yet the mineralization rate of the recalcitrant organic N pool showed a smaller response. An exponential response function described well the relationship between the gross rates of total N mineralization and temperature. Compared with N mineralization, the functional relationship between gross NH4+ immobilization and temperature was not so distinct, resulting in an overall significant increase in net N mineralization at higher temperatures. Heterotrophic nitrification rates increased from 5 °C to 25 °C but declined at higher temperatures. By contrast, the rate of autotrophic nitrification was very low, responding only slightly to the range of temperature change in the most temperature treatments, except for that at 35 °C to 45 °C, when autotrophic nitrification rates were found to be significantly increased. Higher rates of NO3− immobilization than gross nitrification rates resulted in negative net nitrification rates that decreased with increasing temperature. Our results suggested that, with higher temperature, the availability of soil N produced from N mineralization would significantly increase, potentially promoting plant growth and stimulating microbial activity, and that the increased NO3− retention capacity may reduce the risk of leaching and denitrification losses in this studied subtropical acidic forest.

Effects of Temperature and Humidity on Soil Gross Nitrogen Transformation in a Typical Shrub Ecosystem in Yanshan Mountain and Hilly Region

“…In this study, the results showed that gross ammonification rates increased exponentially as the incubation temperature increased from 5 to 35 °C in SL10 and SL20 soils ( R 2 > 0.99, p < 0.01, Figure 2 a), which was consistent with 15 N tracing studies in subtropical broad-leaved forest and coniferous forest soils [ 12 , 44 , 45 ]. In short, ammonification in soil is composed of two processes: decomposition of labile organic N and decomposition of recalcitrant organic N [ 45 ]. The decomposition of recalcitrant organic N is less temperature-sensitive than that of labile organic N in subtropical forests, so it can only be stimulated at higher temperatures [ 44 ].…”

Deciphering waste bound nitrogen by employing psychrophillic Aporrectodea caliginosa and priming of coprolites by associated heterotrophic nitrifiers under high altitude Himalayas

“…1 ). Earlier research also suggests that ammonification is a temperature sensitive microbial mediated mineralization process 46 – 48 and an increase in temperature upto 25 °C will significantly increase the transformation rate of N 49 . The trend for nitrate (NO 3 − N) concentration varied between 8.37 and 81.88 µg NO 3 – N g –1 DW in coprolites influenced by different treatments.…”

“…Previous research findings suggest that earthworm gut and castings tend to have more active heterotrophic microbes that positively influence the amounts of extractable NO 3 – -N in upper layer of soil 51 – 53 moreover, increased NO 3 − concentration in coprolites is a good indicator of the nitrification process and abundance of nitrifiers 23 , 25 , 54 – 56 . It is also reported that the heterotrophic nitrification has an optimum temperature requirement of 15 °C 57 while, it exceeds over autotrophic nitrification if the temperature is increased to 35 °C 49 . Further, we confirm that the heterotrophic nitrification is an ecosystem dependent process which is directly dependent on substrate type, microbial diversity and abundance.…”

Predicting the Ratio of Nitrification to Immobilization to Reflect the Potential Risk of Nitrogen Loss Worldwide

“…Nitrification increases with MAT (p < 0.001) (Figure 4e) and may outcompete immobilization for soil NH 4 + . 57 Dan et al (2019) 58 and Lan et al (2014) 59 reported that the effect of increasing temperature (5−35 °C) on nitrification was greater than that on immobilization. Therefore, the N/I ratio and potential risk of nitrogen loss in tropical and subtropical regions (with high MAT) are higher than those in other climatic regions.…”