Ecosystem carbon stocks in Pinus palustris forests

Abstract

Longleaf pine (Pinus palustris Mill.) restoration in the southeastern United States offers opportunities for carbon (C) sequestration. Ecosystem C stocks are not well understood in longleaf pine forests, which are typically of low density and maintained by prescribed fire. The objectives of this research were to develop allometric equations for above-and below-ground biomass and quantify ecosystem C stocks in five longleaf pine forests ranging in age from 5 to 87 years and in basal area from 0.4 to 22.6 m 2 ·ha −1 . Live aboveground C (woody plant + ground cover) and live root C (longleaf pine below stump + plot level coarse roots + plot level fine roots) ranged from 1.4 and 2.9 Mg C·ha −1 , respectively, in the 5-year-old stand to 78.4 and 19.2 Mg C·ha −1 , respectively, in the 87-year-old stand. Total ecosystem C (live plant + dead organic matter + mineral soil) values were 71.6, 110.1, 124.6, 141.4, and 185.4 Mg C·ha −1 in the 5-, 12-, 21-, 64-, and 87-year-old stands, respectively, and dominated by tree C and soil C. In the 5-year-old stand, ground cover C and residual taproot C were significant C stocks. This unique, in-depth assessment of aboveand below-ground C across a series of longleaf pine stands will improve estimates of C in longleaf pine ecosystems and contribute to development of general biomass models that account for variation in climate, site, and management history in an important but understudied ecosystem.Résumé : La restauration du pin des marais (Pinus palustris Mill.) dans le sud-est des États-Unis offre une opportunité de stocker du carbone (C). Les stocks de C de l'écosystème ne sont pas bien connus dans les forêts de pin des marais qui ont typiquement une faible densité et se maintiennent grâce au brûlage dirigée. Les objectifs de ces travaux de recherche consistaient à élaborer des équations allométriques pour la biomasse aérienne et souterraine et à quantifier les stocks de C de l'écosystème dans cinq forêts de pin des marais dont l'âge allait de 5 à 87 ans et dont la surface terrière variait de 0,4 à 22,6 m 2 ·ha -1 . Le C aérien vert (plantes ligneuses + couverture végétale) et le C des racines vivantes (souches de pin des marais + grosses racines et racines fines présentes dans les placettes) variaient respectivement de 1,4 et 2,9 Mg C·ha -1 dans le peuplement âgé de 5 ans à 78,4 et 19,2 Mg C·ha -1 dans le peuplement âgé de 87 ans. Le C total de l'écosystème (plantes vivantes + matière organique morte + sol minéral) atteignait respectivement 71,6, 110,1, 124,6, 141,4 et 185,4 Mg C·ha -1 dans les peuplements âgés de 5, 12, 21, 64 et 87 ans et était dominé par le C des arbres et du sol. Dans le peuplement âgé de 5 ans, le C contenu dans la couverture végétale et les racines pivotantes résiduelles constituait un stock important de C. Cette évaluation unique et approfondie du C aérien et souterrain dans une série de peuplements de pin des marais améliorera les estimations du C dans les écosystèmes dominés par cette essence et contribuera au développement de modèles généraux de biomass...

Local and General Above-Ground Biomass Functions for Pinus palustris Trees

“…Compared with system I (based on DBH only), system III additionally included tree age which was significant only in the bole biomass equation, but also improved the branch and total biomass predictions. This response may be related to changes in wood density as trees age [9,22] and the interdependence of additive models. When A was included in the models that used DBH and HT (model system IV), it was significant in bole, branch and foliage equations, improving bole, branch and total biomass predictions.…”

“…However, the positive coefficient of DBH and the negative coefficient of HT in branch and foliage components imply that branch and foliage biomass increase with the increase of DBH, but for the same DBH, live branch and foliage biomass decrease with increased tree height. (9) In the DBH and A based system (Equation (9)), DBH is significant in all component equations, but age is significant only for the bole biomass component (Table 5). This implies that with tree DBH information in the equation, the addition of tree age did not improve branch and foliage biomass estimation but did improve bole biomass estimation.…”

“…The data used in this study were compiled from several sources that were previously used to develop site-specific allometric functions [7][8][9][15][16][17][18][19]. Similar to Gonzalez-Benecke et al [10], the observations compiled corresponded to the raw data used for model fitting and not to the published equation estimates.…”

“…Often, local functions used to estimate tree biomass rely on the stem diameter over-bark at 1.37 m height (DBH) [2,7], or DBH and total tree height (HT) as explanatory variables [8,9]. These models are widely used but limited to certain stand characteristics and geographical areas, particularly those from which the data originated.…”

Carbon Dynamics of Pinus palustris Ecosystems Following Drought

“…)-dominated forests within the Southeastern United States (SEUS), to better understand their carbon dynamics [18][19][20]. The longleaf pine forest is an excellent example of how placement of a stand within the landscape has led to variation in structure and function, particularly when influenced by water limitations [21][22][23][24]. Soil water holding capacity has been shown to be the primary variable that controls net primary production (NPP) within the longleaf ecosystem [21], and was linked to plant rooting zones and access to the water table [23,25].…”