Simulated chronic NO3- deposition reduces soil respiration in northern hardwood forests
Simulated chronic NO3- deposition reduces soil respiration in northern hardwood forests
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DOI：
10.1111/j.1365-2486.2004.00737.x
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发表时间：
2004-07-01
影响因子：
11.6
通讯作者：
Zak, DR
中科院分区：
文献类型：
--
作者：
Burton, AJ;Pregitzer, KS;Zak, DR
森林生态系统中长期添加氮可以提高土壤氮的有效性，可能导致根系碳分配减少。这反过来又可以减少土壤CO2排放。我们测量土壤呼吸在第一，第五，第六和第八年的模拟大气NO3-沉积（3克N米（-2）年（-1）），以4糖枫树为主的北方阔叶林在密歇根州，以评估这些可能性。在第一年，土壤呼吸速率略有上升，但不显着，在NO3-修正地块。在随后的测量年，土壤呼吸速率从NO3-修正土壤显着抑制。土壤温度和土壤基质势与土壤呼吸同时测定，并用于建立回归关系预测土壤呼吸速率。使用这些关系的生长季节和每年的土壤CO2排放量的估计表明，这些C通量被压低了15%，在第八年的慢性NO3-添加。土壤呼吸的减少是由于减少C分配到根，根呼吸速率，根生物量和根周转没有显着影响氮添加。8年给药期间，地面窝仔也未发生变化。在土壤CO2排放量下降的其余潜在原因中，微生物呼吸作用减少似乎是最有可能的。记录减少微生物生物量和用于凋落物降解的NO3-修正地块的胞外酶的活动与这一解释是一致的。
Chronic N additions to forest ecosystems can enhance soil N availability, potentially leading to reduced C allocation to root systems. This in turn could decrease soil CO2 efflux. We measured soil respiration during the first, fifth, sixth and eighth years of simulated atmospheric NO3- deposition (3 g N m(-2) yr(-1)) to four sugar maple-dominated northern hardwood forests in Michigan to assess these possibilities. During the first year, soil respiration rates were slightly, but not significantly, higher in the NO3--amended plots. In all subsequent measurement years, soil respiration rates from NO3--amended soils were significantly depressed. Soil temperature and soil matric potential were measured concurrently with soil respiration and used to develop regression relationships for predicting soil respiration rates. Estimates of growing season and annual soil CO2 efflux made using these relationships indicate that these C fluxes were depressed by 15% in the eighth year of chronic NO3- additions. The decrease in soil respiration was not due to reduced C allocation to roots, as root respiration rates, root biomass, and root turnover were not significantly affected by N additions. Aboveground litter also was unchanged by the 8 years of treatment. Of the remaining potential causes for the decline in soil CO2 efflux, reduced microbial respiration appears to be the most likely possibility. Documented reductions in microbial biomass and the activities of extracellular enzymes used for litter degradation on the NO3--amended plots are consistent with this explanation.