No fertilization effects on soil respiration and root respiration in northern hardwoods of New Hampshire.

Soil respiration has received a great deal of attention recently because it is a major pathway of flux in the terrestrial ecosystem carbon cycle. The soil respiration can be affected by soil resource availability owing to changes in forest productivity. In our previous study which quantified pre-fertilized conditions in northern hardwood stands in Bartlett and Hubbard Brook Experimental Forests and Jeffers Brook, White Mountain National Forest, soil respiration was low in high N availability sites in northern hardwood stands of different ages in New Hampshire. To understand which mechanisms of soil respiration are affected by soil nutrient availability, we measured? soil respiration and root respiration in N, P, and N and P fertilized plots of differing ages at each site. After fertilization in 2011 and 2012, soil respiration was unchanged in most stands and root respiration was unchanged regardless of nutrients and forest age. The general lack of evidence of fertilization effects on soil respiration and root respiration supports that carbon flux in soils does not change within a couple of years after nutrient additions. Continuous measurements are needed over a long period.