Effects of temperature and tissue nitrogen on dormant season stem and branch maintenance respiration in a young loblolly pine (Pinus taeda) plantation

Abstract

We measured dormant season (November through February) maintenance respiration rates (R(m)) in stems and branches of 9-year-old loblolly pine (Pinus taeda L.) growing in plots under conditions of controlled nutrient and water supply in an effort to determine the relationships between R(m) and tissue size (surface area, sapwood volume, sapwood dry weight), tissue nitrogen content and temperature. Dormant season R(m) per unit size (i.e., surface area, &mgr;mol m(-2) s(-1); sapwood volume, &mgr;mol m(-3) s(-1); or sapwood dry weight, nmol g(-1) s(-1)) varied with tissue size, but was constant with respect to tissue nitrogen content (&mgr;mol mol(-1) N s(-1)). Cambium temperature accounted for 61 and 77% of the variation in stem and branch respiration, respectively. The basal respiration rate (respiration at 0 degrees C) increased with tissue nitrogen content, however, the Q(10) did not. Improved nutrition more than doubled stem basal respiration rate and increased branch basal respiration by 38%. Exponential equations were developed to model stem and branch respiration as a function of cambium temperature and tissue nitrogen content. We conclude that failure to account for tissue nitrogen effects on respiration rates will result in serious errors when estimating annual maintenance costs.

Spatial and seasonal variations in stem respiration of beech trees (Fagus sylvatica)

“…In accordance to previous studies [28,32,40,41,49], stem respiration varied strongly within a tree in Hesse. The factor of variation for respiration was higher when calculated on a volume base than on a surface-area base.…”

“…[2,41]: growth respiration, which provides the energy needed to synthesise new tissues, is a function of wood growth; and maintenance respiration, which maintains existing living cells, is usually a function of biomass [36], sapwood volume [19], surface area [46] or nitrogen content [28]. This separation in two components is necessary to understand how stand development, climate and management affect forest carbon cycling.…”

“…Thus estimates of the growth respiration coefficient (r G ) and biomass increments, of standing biomass and maintenance respiration rate (r M ), are required to estimate stem respiration at stand level. Usually, r G and r M are derived from measurements at breast height (1.3 m), but some studies have shown that respiration varies with stem and branch diameter or height [4,5,8,18,32,40,41,49], or with the woody organ (stem or branch) considered [5,28,32,41,49].…”

“…Because of the smaller diameter of the organs, the stem tissues also warm faster at the top than at the base of the stem. Indeed, Q 10 , the factor expressing respiration increase for a temperature increase of 10 o C, can vary with height along the stem [8] or with the organ in question, stem or branch [28].…”

“…More information is also needed to be able to choose the best unit to scale up stem or branch respiration to stand level, because this unit can have a large impact on the final results. Hitherto, the most common units have been surface area [18,46] or sapwood volume [36], but sapwood fresh mass [49] or sapwood dry mass and nitrogen content [28,[37][38][39][40] have also been used to express maintenance respiration. Sprugel et al [43] suggested that sapwood volume was a better calculation base, because respiration rates per unit volume are rather constant within coniferous species.…”