Response Of The Broadleaved Deciduous Forest Soil Respiration To The Simulated Nitrogen Deposition At The Crown Canopy In Jigong Mountain

Since the industrial revolution, mankind have exerted substantial bearings on the human survival environment. The common occurrence of atmospheric nitrogen deposition will massively impact the human society and terrestrial ecosystem. Forest ecosystem, as the main part of the terrestrial ecosystem, serves as the enormous nitrogen pool. As soil respiration is a vital component of carbon flux in the forest ecosystem, even a slight change in soil respiration could markedly accelerate or slow down the increase in CO2, thus impacting the global or local climate change. Against the backdrop of the increasing nitrogen deposition, it is of prime importance to conduct research on the influence of forest soil respiration on artificially simulated nitrogen deposition. By taking Jigong Mountain Nature Conservation Area, which is located at the north subtropical-warm temperate transition zone, as the research object and capitalizing on field control experimental platform of “canopy simulated nitrogen deposition and rainfall”(CAN-WE), this paper selects two of them for processing so as to compare the two levels, namely,(CK,0kg·hm-2·a) and addition of nitrogen of 25kg·hm-2·a(CN25) at the crown canopy(with 4 repetitions set in each processing). The measurement and analysis of the total soil respiration, soil heterotrophic respiration, soil temperature and soil humidity under the two processing methods generates the following results:1.The soil respiration(total soil respiration and heterotrophic respiration) in the treatment plot(CK) of deciduous broad-leaved forest is possessed of obvious seasonal dynamics(P<0.01). The rate of total soil respiration and soil heterotrophic respiration reaches the lowest value in January(0.77μmol·m-2 s-1, 0.64μmol·m-2 s-1) but the highest level in July and August(6.53μmol·m-2 s-1, 6.73μmol·m-2 s-1).2.The simulated nitrogen application at the crown canopy markedly inhibits the heterotrophic respiration rate of the soil(p<0.05) with insignificant influence on the total soil respiration(P>0.05). In the quadrat of CN25, The rate of total soil respiration and soil heterotrophic respiration are 1.77μmol·m-2 s-1 and 2.06μmol·m-2 s-1 respectively; however, in the contrastive plots, the rate of total soil respiration and soil heterotrophic respiration are 2.42μmol·m-2 s-1 and 2.56μmol·m-2 s-1. The rate of total soil respiration and soil heterotrophic respiration are all manifested as CK>CN25. In the quadrat with nitrogen application at the crown canopy, the total soil respiration and soil heterotrophic respiration are possessed of significant seasonal difference(P<0.01) along with the change of the month.3.In the nitrogen application at the crown canopy and sample plot, the total soil respiration and soil heterotrophic respiration are exponential with soil temperature and display polynomial relations with the soil humidity. In the sample plot where the nitrogen is applied to the croan canopy, the temperature sensibility(Q10) of the total soil respiration and soil heterotrophic respiration is 2.22 and 2.61 respectively. In the contrast sample plot, the temperature sensibility of the total soil respiration and soil heterotrophic respiration(Q10) is 2.3 and 2.76 respectively. The temperature sensibility of the total soil respiration and soil heterotrophic respiration(Q10) all display as CK>CN25. Therefore, the nitrogen application at the crown canopy inhibits the sensibility of total soil respiration and soil heterotrophic respiration to temperature.