The Short-term Effects of Fertilization on Total Soil CO2 Efflux, Heterotrophic, and Autotrophic Respiration of Loblolly Pine (Pinus taeda L.)
MetadataShow full item record
Fertilization is a common, cost effective treatment for increasing forest productivity within managed forests of the southeastern United States. However, little is known about how fertilization affects the below-ground processes that drive soil CO2 efflux in loblolly pine (Pinus taeda L.). A thorough understanding of below-ground carbon dynamics is necessary for the estimation of net ecosystem productivity and the carbon storage potential of these managed systems.
In April 2004, we began monitoring total soil CO2 efflux (EC), heterotrophic (RH), and root respiration (RR) in response to fertilization with diammonium phosphate (DAP). Respiratory components were measured prior to fertilization, weekly following fertilization, and bi-weekly after respiratory components stabilized using a dynamic closed chamber and an infrared gas analyzer. We found that EC differed significantly (P<0.0001) between fertilized and unfertilized plots, but the direction was dependent on date. In the early period of the study, fertilized plot values were lower than control plots. However, by the latter periods fertilized plot values returned to control levels except for one sampling date in March 2005 when fertilized plot values were greater then control plots. Heterotrophic respiration was consistently and significantly (P=0.0002) lower in fertilized plots. Root respiration was significantly (P=0.0597) increased in fertilized plots when analyzed over the study and showed a 20% increase due to fertilization. We concluded that an increase in RR and possibly root biomass was enough to balance the decrease in RH leading to no difference in EC later in the growing season.
We performed a pair of greenhouse studies to observe the effects of fertilization in the form of diammonium phosphate (DAP) on RR. The objectives were to determine how nutrient additions initially affect RR in one-year-old loblolly pine seedlings. Secondly, we wanted to determine if Captan [N-(trichloromethylthio) cyclohex-4-ene-1, 2-dicarboximide], a mild fungicide, could be used to reduce or eliminate ecto-mycorrhizae upon visual inspection. Both studies showed that initially, at a high rate (100 ppm N and 49 ppm P) of fertilization, RR was significantly (P<0.10) increased relative to seedlings that did not receive fertilization. This increase was only temporary with rates returning to, or decreasing below, control levels by the end of the study. No consistent trend was found between low (25 ppm N and 13 ppm P) and moderate (50 ppm N and 25 ppm P) rates of fertilization. Captan was shown to generally have no affect on RR. Captan and fertilization both showed (visual inspection) a decrease in fine-roots and mycorrhizae, which could explain the reduction in respiration rates observed in these treatments by the end of the studies.
- Masters Theses 
Showing items related by title, author, creator and subject.
Soil Carbon Dioxide Efflux Across Four Age Classes Of Plantation Loblolly Pine (Pinus taeda L.)On The Virginia Piedmont Wiseman, Phillip Eric (Virginia Tech, 2001-09-18)Soil carbon dioxide efflux resulting from microbial and root respiration is a major component of the forest carbon cycle. We undertook this investigation to better understand the nature of soil carbon dioxide efflux of ...
Soil Co2 Efflux and Soil Carbon Content as Influenced by Thinning in Loblolly Pine Plantations on the Piedmont of Virginia Selig, Marcus Franklin (Virginia Tech, 2003-07-01)The thinning of loblolly pine plantations has a great potential to influence the fluxes and storage of carbon within managed stands. This study looked at the effects of thinning on aboveground carbon and mineral soil ...
SOIL CARBON DIOXIDE EFFLUX IN RESPONSE TO FERTILIZATION AND MULCHING TREATMENTS IN A TWO-YEAR-OLD LOBLOLLY PINE (Pinus taeda L.) PLANTATION IN THE VIRGINIA PIEDMONT Pangle, Robert E. (Virginia Tech, 2000-12-08)Due to concern over the increasing concentration of carbon dioxide in the atmosphere, forest researchers and managers are currently studying the effects of varying silvicultural and harvesting practices on the carbon ...