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• 1. [Article] Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine

  Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity ...

  Citation × Citation Citation Abstract Copy Title: Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine Author: Lucash, Melissa S., Joslin, J. Devereux, Yanai, Ruth D. Year: 2005 Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity of K, NH+ 4, NO 3 −, Mg and Ca across a range of solution concentrations by roots of mature loblolly pine at Calhoun Experimental Forest in October 2001, July 2001, and April 2002. Uptake capacity was generally lowest in July; rates in October were similar to those in April. Across a range of concentrations, antecedent nutrient solution concentrations affected the temporal patterns in uptake in July but not in October or April. In July, uptake of NH+ 4, Mg and Ca was positively correlated with concentration when roots were exposed to successively lower concentrations, but negatively correlated with concentration when exposed to successively higher concentrations. In contrast, uptake in October was constant across the range of concentrations, while uptake increased with concentration in April. As in studies of other species, we found greater uptake of NH+ 4 than NO 3 −. Temporal patterns of uptake capacity are difficult to predict, and our results indicate that experimental conditions, such as experiment duration, antecedent root conditions and nutrient solution concentration, affect measured rates of nutrient uptake. Title: Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine Author: Lucash, Melissa S., Joslin, J. Devereux, Yanai, Ruth D. Year: 2005 Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity of K, NH+ 4, NO 3 −, Mg and Ca across a range of solution concentrations by roots of mature loblolly pine at Calhoun Experimental Forest in October 2001, July 2001, and April 2002. Uptake capacity was generally lowest in July; rates in October were similar to those in April. Across a range of concentrations, antecedent nutrient solution concentrations affected the temporal patterns in uptake in July but not in October or April. In July, uptake of NH+ 4, Mg and Ca was positively correlated with concentration when roots were exposed to successively lower concentrations, but negatively correlated with concentration when exposed to successively higher concentrations. In contrast, uptake in October was constant across the range of concentrations, while uptake increased with concentration in April. As in studies of other species, we found greater uptake of NH+ 4 than NO 3 −. Temporal patterns of uptake capacity are difficult to predict, and our results indicate that experimental conditions, such as experiment duration, antecedent root conditions and nutrient solution concentration, affect measured rates of nutrient uptake. Close

• 2. [Article] Estimating Nutrient Uptake by Mature Tree Roots Under Field Conditions: Challenges and Opportunities

  Nutrient uptake by roots of mature trees is difficult to measure accurately under field conditions using existing methods. In this review, we discuss current techniques for measuring uptake at the root ...

  Citation × Citation Citation Abstract Copy Title: Estimating Nutrient Uptake by Mature Tree Roots Under Field Conditions: Challenges and Opportunities Author: Lucash, Melissa S., Eissenstat, Dave M., Joslin, J. Devereux, McFarlane, Karis J., Yanai, Ruth D. Year: 2007 Nutrient uptake by roots of mature trees is difficult to measure accurately under field conditions using existing methods. In this review, we discuss current techniques for measuring uptake at the root surface including excised roots, isotopic tracers, autoradiography, depletion, and lysimeters. Although these methods have provided many insights, each has drawbacks. Estimates of uptake are affected by the sampling scheme, experimental conditions, whether roots are excised or not, concentrations of ions, and the rate of efflux of ions. Microbes and mycorrhizas can also affect estimates of uptake. A greater focus on methods development is critical to advancing our understanding of nutrient uptake of mature trees under conditions representative of those in the field. Title: Estimating Nutrient Uptake by Mature Tree Roots Under Field Conditions: Challenges and Opportunities Author: Lucash, Melissa S., Eissenstat, Dave M., Joslin, J. Devereux, McFarlane, Karis J., Yanai, Ruth D. Year: 2007 Nutrient uptake by roots of mature trees is difficult to measure accurately under field conditions using existing methods. In this review, we discuss current techniques for measuring uptake at the root surface including excised roots, isotopic tracers, autoradiography, depletion, and lysimeters. Although these methods have provided many insights, each has drawbacks. Estimates of uptake are affected by the sampling scheme, experimental conditions, whether roots are excised or not, concentrations of ions, and the rate of efflux of ions. Microbes and mycorrhizas can also affect estimates of uptake. A greater focus on methods development is critical to advancing our understanding of nutrient uptake of mature trees under conditions representative of those in the field. Close

• 3. [Article] Nutrient Uptake by Intact and Disturbed Roots of Loblolly Pine Seedlings

  Most measurements of nutrient uptake use either hydroponic systems or soil-grown roots that have been disturbed by excavation. The first objective of this study was to test how root excavation affects ...

  Citation × Citation Citation Abstract Copy Title: Nutrient Uptake by Intact and Disturbed Roots of Loblolly Pine Seedlings Author: Lucash, Melissa S., Yanai, Ruth D., Joslin, J. Devereux Year: 2008 Most measurements of nutrient uptake use either hydroponic systems or soil-grown roots that have been disturbed by excavation. The first objective of this study was to test how root excavation affects nitrate uptake. Rates of NO3− uptake by mycorrhizal loblolly pine (Pinus taeda L.) seedlings were measured in intact sand-filled columns, hydroponics, and disturbed sand-filled columns. Total nitrate uptake in intact sand-filled columns was higher than in disturbed columns, indicating that disturbance lowers uptake. Transferring plants from the sand-filled columns to hydroponics had little effect on NO3− uptake beyond delaying uptake for an hour. The second objective of this study was to determine whether NH4+, Ca2+, Mg2+ and K+ uptake could be studied using sand-filled columns, since previous studies had tested this method only for nitrate uptake. Uptake rates of NH4+ and K+ were positive, while Ca2+ and Mg2+ uptake rates were negative in intact sand-filled columns, indicating that net efflux may occur even without physical disturbance to the root system. The sand-filled column approach has some limitations, but holds promise for conducting nutrient uptake studies with minimal disturbance to the root system. Title: Nutrient Uptake by Intact and Disturbed Roots of Loblolly Pine Seedlings Author: Lucash, Melissa S., Yanai, Ruth D., Joslin, J. Devereux Year: 2008 Most measurements of nutrient uptake use either hydroponic systems or soil-grown roots that have been disturbed by excavation. The first objective of this study was to test how root excavation affects nitrate uptake. Rates of NO3− uptake by mycorrhizal loblolly pine (Pinus taeda L.) seedlings were measured in intact sand-filled columns, hydroponics, and disturbed sand-filled columns. Total nitrate uptake in intact sand-filled columns was higher than in disturbed columns, indicating that disturbance lowers uptake. Transferring plants from the sand-filled columns to hydroponics had little effect on NO3− uptake beyond delaying uptake for an hour. The second objective of this study was to determine whether NH4+, Ca2+, Mg2+ and K+ uptake could be studied using sand-filled columns, since previous studies had tested this method only for nitrate uptake. Uptake rates of NH4+ and K+ were positive, while Ca2+ and Mg2+ uptake rates were negative in intact sand-filled columns, indicating that net efflux may occur even without physical disturbance to the root system. The sand-filled column approach has some limitations, but holds promise for conducting nutrient uptake studies with minimal disturbance to the root system. Close