Changes in carbon storage and fluxes in a chronosequence of ponderosa pine

Abstract

Forest development following stand‐replacing disturbance influences a variety of ecosystem processes including carbon exchange with the atmosphere. On a series of ponderosa pine (Pinius ponderosa var. Laws.) stands ranging from 9 to> 300 years in central Oregon, USA, we used biological measurements to estimate carbon storage in vegetation and soil pools, net primary productivity (NPP) and net ecosystem productivity (NEP) to examine variation with stand age. Measurements were made on plots representing four age classes with three replications: initiation (I, 9–23 years), young (Y, 56–89 years), mature (M, 95–106 years), and old (O, 190–316 years) stands typical of the forest type in the region. Net ecosystem productivity was lowest in the I stands (−124 g C m−2 yr−1), moderate in Y stands (118 g C m−2 yr−1), highest in M stands (170 g C m−2 yr−1), and low in the O stands (35 g C m−2 yr−1). Net primary productivity followed similar trends, but did not decline as much in the O stands. The ratio of fine root to foliage carbon was highest in the I stands, which is likely necessary for establishment in the semiarid environment, where forests are subject to drought during the growing season (300–800 mm precipitation per year). Carbon storage in live mass was the highest in the O stands (mean 17.6 kg C m−2). Total ecosystem carbon storage and the fraction of ecosystem carbon in aboveground wood mass increased rapidly until 150–200 years, and did not decline in older stands. Forest inventory data on 950 ponderosa pine plots in Oregon show that the greatest proportion of plots exist in stands ∼ 100 years old, indicating that a majority of stands are approaching maximum carbon storage and net carbon uptake. Our data suggests that NEP averages ∼ 70 g C m−2 year−1 for ponderosa pine forests in Oregon. About 85% of the total carbon storage in biomass on the survey plots exists in stands greater than 100 years, which has implications for managing forests for carbon sequestration. To investigate variation in carbon storage and fluxes with disturbance, simulation with process models requires a dynamic parameterization for biomass allocation that depends on stand age, and should include a representation of competition between multiple plant functional types for space, water, and nutrients.

Aboveground biomass and corresponding carbon sequestration ability of four major forest types in south China

“…Figure 3 shows the estimated T ABC increased continuously with forest stand age across all four forest types in the two time periods, 1994-1998 and 1999-2003, respectively. Previous studies had reported T ABC maintained a balance or slight decline in mature and old forest stages [15][16][17], but this study found a significant increase of T ABC between mature and old stages (Figure 3). The differences of T ABC among all age stages were significant (P < 0.01) for the four forest types (Figure 3).…”

“…A number of studies on tree growth indicate plant biomass increases with forest stand age, and reaches an equilibrium or declines slightly in mature and old stages [15][16][17]. However, increasing amounts of soil organic carbon were found in many old-growth forests [3].…”

“…Generally, biomass carbon accumulation rates increase continuously until the forest canopy closes; after that, it tends to decrease. Many studies reported these age-related patterns with logistic regression curves [15,17,22]. Using the data from the national forest inventory from 1994-1998 and 1999-2003, Figure 2 shows the relationship between T ABC and forest stand age over time.…”

Leaf-Level Gas Exchange and Foliar Chemistry of Common Old-Field Species Responding to Warming and Precipitation Treatments

“…The effects of precipitation changes on individual plant performance are complex and depend on a number of factors, such as ambient rainfall conditions, initial soil water status, occurrence and seasonality of extreme heat stress or droughts (De Boeck et al 2011), plant age (Law et al 2003), the ability of the plant to shed wilted leaves (Chaves et al 2009), and the diversity of the surrounding plant community (Kahmen et al 2005). Previous studies have found that the photosynthetic responses of grassland plants to rainfall manipulations simulating drought conditions have ranged from negative to neutral (reviewed in Fay et al 2002).…”

Water availability limits tree productivity, carbon stocks, and carbon residence time in mature forests across the western US

“…Trees invest a larger proportion of NPP into aboveground tissue production as conditions become wetter and competition for light intensifies (Runyon et al, 1994;Law et al, 2003). Our field measurements suggested that the fraction of NPP allocated aboveground increased from ∼ 0.45 in the driest areas to ∼ 0.64 in the wettest areas and, furthermore, that CRT in aboveground tissues averaged twice as long as CRT in belowground tissues.…”