ISSN 00124966, Doklady Biological Sciences, 2014, Vol. 456, pp. 173–176. © Pleiades Publishing, Ltd., 2014. Original Russian Text © O.V. Menyailo, A.I. Matvienko, M.I. Makarov, C.H. Cheng, 2014, published in Doklady Akademii Nauk, 2014, Vol. 456, No. 1, pp. 117–120.
Positive Response of Carbon Mineralization to Nitrogen Addition in Forest Soils of Siberia O. V. Menyailoa, A. I. Matvienkoa, M. I. Makarovb, C.H. Chengc Presented by Academician E.A. Vaganov November 25, 2013 Received December 9, 2013
Human activities and production of nitrogen fertil izers have altered the global nitrogen cycle to a greater extent than the carbon cycle [1, 2]. At the same time, nitrogen inputs into various ecosystems, in the form of either fertilizers or atmospheric depositions, lead to substantial changes not only in nitrogen, but also in carbon cycles [2, 3]. Nitrogen input into an ecosystem usually enhances its biological productivity and often results in increased carbon accumulation in plants. As estimated for temperate and boreal forests, addition of 1 kg of nitrogen leads to accumulation of extra 25 kg of carbon in plant biomass . The fate of the main biosphere carbon reservoir, the soil carbon, is less understood. Addition of nitrogen may lead to either accumulation  or loss of soil car bon . The published data suggest that in most cases, with increasing nitrogen input, carbon accumulation in soil predominates because of the inhibition of the activity of soil heterotrophic microorganisms . However, most published reports are based on the experiments conducted in Central Europe, United States , and, recently, in China , i.e., in highly industrialized countries with a high level of atmo spheric N depositions. At low and average inputs of nitrogen into an ecosystem, the response of carbon transformation processes is assumed to be fundamen tally different . In Siberia, where the atmospheric nitrogen depositions are among the lowest in the world (0.25–1 (kg ha–1 year–1)) , there is no data on the influence of elevated nitrogen depositions on mineral ization of soil carbon. The goal of this study was to assess the influence of nitrogen additions on carbon mineralization activity in soils beneath different tree species and adjacent a
Institute of Forest, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia b Department of Soil Science, Moscow State University, Moscow, 119992 Russia c School of Forestry and Resource Conservation, National Taiwan University in Taipei, Taipei, 106 Taiwan email: [email protected]
grassland. We have demonstrated that the addition of nitrogen stimulates activity of heterotrophic microor ganisms that mineralize soil organic matter. Our data suggest that Siberian ecosystems are not exposed to nitrogen pollution even in the vicinity of industrial centers, such as Krasnoyarsk, and, therefore, the effect of nitrogen added to soil is fundamentally differ ent as compared to the effect of high atmospheric nitrogen depositions on soils of the industrialized countries. Soils were sampled on the experimental plots of the Institute of Forest, Siberian Branch, Russian Acad emy of Science, where six different tree species were planted in 1971 [11, 12]. The samples of the upper mineral horizon A1 (0–10 cm) and of the litter were taken in triplicate beneath six tree species: spruce (Picea abies), pine (Pinus sylvestris), Arolla pine (Pinus sibirica), larch (Larix sibirica), birch (Betula pendula), and aspen (Populus tremula). Soil was also sampled from the adjacent grassland (only the mineral horizon, because the litter was absent). The soil type was forest gray soil. The activity of carbon mineraliza tion was determined in an incubation experiment (70 g of soil or 30 g of litter were incubated in a 500ml flask at constant temperature (25°C) and moisture (60% of the water holding capacity (WHC). Nitrogen was added in the form of NH4NO3 to reach a con centration corresponding to the nitrogen input of 50 kg N ha–1 (the dose was relatively high because of a shortterm experiment). The rate of CO2 formation was measured before and a day after the addition of nitrogen using a LiCor 8100 infrared gas analyzer and a 16channel LiCor 8150 multiplexer. To assess the effect of nitrogen accurately (to reduce the influence of soil sample heterogeneity), the relative activity of carbon mineralization was calculated for each sample as a percentage of the initial activity (before addition of nitrogen). The effects of various factors were esti mated using two and threeway ANOVA and was considered statistically significant at p < 0.05. The results were processed statistically using Statistica 8.0.
MENYAILO et al. Activity of CO2 release in the litter, (µM kg–1 s–1) 40 Litter 35 Soil
Activity of CO2 release in the mineral soil, (µM kg–1 s–1) 10 9 8
30 7 25
3 10 2 5 0 Arolla pine
1 0 Larch
Fig. 1. Activity of carbon mineralization in the organic (litter) and mineral soil horizons beneath the six tree species and in grass land. Here and in Fig. 2, the mean values and standard errors (n = 3) are indicated. Identical Latin letters near the bars of similar color indicate insignificant differences (p > 0.050).
Carbon mineralization activity was three to five times higher in the litter layers than in mineral soils (Fig. 1) because of a the higher carbon contents in lit ter and more intense microbiological degradation in the litters. Except for the soil beneath Arolla pine, the rates of C mineralization in the mineral soil samples were correlated with those in the litters; i.e., tree spe cies with high mineralization rates of the litter were also characterized by a high mineralization rates in the mineral soil. This testifies to correspondence between the above and belowground litter quality (degrad
ability) among the most studied tree species. Overall, the soil sampled beneath different tree species differed 1.5 to 2times in activity of carbon mineralization (p < 0.001, table). The threeway ANOVA demonstrated that the tree species, horizon, and nitrogen addition had a strong effect on the relative rate of carbon mineralization (table). Analysis of the main factor effects was per formed for the litter and mineral soil separately (two way ANOVA). This revealed a positive effect of nitro gen only for the mineral soil, where the rate of carbon
Table 1. The results of two and threeway ANOVA for the rate of carbon mineralization For the rate of carbon mineralization
For the relative rate of carbon mineralization
Factors and their interaction
Horizon (the litter, mineral soil) Woody species N addition Horizon × species Horizon × N addition Species × N addition Horizon × Species × N addition