Short-term changes in loblolly pine water conductance and photosynthetic capacity from fertilizer source and straw harvesting
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Organic matter removal associated with intensive straw harvesting in loblolly pine (Pinus taeda L.) plantations has the potential to alter tree water regimes and photosynthetic capacity. Fertilization done to remedy nutrient removals from straw harvesting, as well as the type of fertilizer, likewise has potential to change water regimes and photosynthetic capacity of these plantations. In 2008 and 2009, conductance, light-saturated photosynthesis, and intrinsic water use efficiency were measured seasonally in a loblolly pine plantation in north central Louisiana in response to: (1) a non-raked, non-fertilized control treatment, (2) annual straw raking for seven years, (3) annual straw raking for seven years and five years of inorganic fertilizer application, and (4) annual straw raking for seven years and five years of organic fertilizer (poultry litter) application. Precipitation was comparable to or exceeded regional averages throughout the study period. Conductance in spring was greater in response to poultry litter application than to all other treatments. Both fertilization treatments were associated with lower photosynthetic capacity in summer relative to the control treatment. No differences in intrinsic water use efficiency were observed in response to treatments.