Net Primary Production of a Forest Ecosystem with Experimental CO ₂ Enrichment

Abstract

The concentration of atmospheric carbon dioxide was increased by 200 microliters per liter in a forest plantation, where competition between organisms, resource limitations, and environmental stresses may modulate biotic responses. After 2 years the growth rate of the dominant pine trees increased by about 26 percent relative to trees under ambient conditions. Carbon dioxide enrichment also increased litterfall and fine-root increment. These changes increased the total net primary production by 25 percent. Such an increase in forest net primary production globally would fix about 50 percent of the anthropogenic carbon dioxide projected to be released into the atmosphere in the year 2050. The response of this young, rapidly growing forest to carbon dioxide may represent the upper limit for forest carbon sequestration.

Characterization of an urban-rural CO 2 /temperature gradient and associated changes in initial plant productivity during secondary succession

“…The biomass accumulation values for the urban and suburban locations are considerably higher than those reported for other community-level studies in which [CO 2 ] alone was manipulated (e.g. DeLucia et al 1999;Edwards et al 2001;Morgan et al 2001;Reich et al 2001) and productivity for the urban site was extremely high (Cooper 1970). Both the suburban and urban sites were also differentiated by significant increases in plant height (lambsquarters) relative to the rural location (Table 4).…”

“…While important, these data have unclear implications regarding responses of plant communities or ecosystems since they do not address plant assemblages, nor do they include other climatic variables such as temperature (DeLucia et al 1999;Reich et al 2001). Yet, in typical climate change scenarios, both ambient air temperature and [CO 2 ] increase concomitantly since elevated CO 2 is a primary driver of climate change (Intergovernmental Panel on Climate Change (IPCC) scenarios IS 92e and IS 92 a in Schimel et al 1996).…”

Using experimental manipulation to assess the roles of leaf litter in the functioning of forest ecosystems

“…The quantity of litterfall varies greatly over a range of spatial and temporal scales and is determined mainly by climate, seasonality, topography, soil parent materials, and species distribution. Management practices can cause drastic changes in litter production by modifying species composition and productivity ; climate change may affect litterfall as changes in rainfall patterns and mean annual temperatures can affect tree phenology and tree species distribution (Condit, Hubbell & Foster, 1996) and increases in productivity and litterfall have been observed as a consequence of elevated atmospheric CO 2 levels (DeLucia et al, 1999 ;Allen et al, 2000 ;Finzi et al, 2001 ;Schlesinger & Lichter, 2001;Zak et al, 2003). Experiments involving litter removal and litter addition treatments amplify these changes in litter quantity, thus invoking stronger effects over shorter time periods, which are more easily detectable than the effects of natural variation.…”

Depolarizing the GM debate

“…Though single-investigator research remains strong, the solution to many global ecological questions also requires large-scale collective research efforts. The effect of elevated CO 2 or variation in species composition on the biogeochemical cycling of carbon and nitrogen, for example, is being addressed in expansive, highly collaborative experiments (DeLucia et al , 1999;Smith et al , 2000). And, policy-driven question about the capacity of ecosystems to store atmospheric carbon have spawned international research programs using coordinated methodologies and analytical tools (e.g.…”

“…Large collaborative research projects provide another way to approach important questions such as how ecosystems will respond to rapid global change. In North Carolina, circular plots in a 17-yr-old loblolly pine forest are exposed to ambient or ambient plus 200 µl l −1 CO 2 , simulating the atmospheric composition expected in the year 2050 (DeLucia et al, 1999). A similar experimental treatment is applied in Nevada to a Mohave Desert scrub community, dominated by Larrea tridentata and Ambrosia dumosa (Smith et al, 2000).…”