Hardwood Seedling Root and Nutrient Parameters for a Model of Nutrient Uptake

Abstract

Use of mechanistic models is an increasingly accepted way to evaluate complex processes. The Barber-Cushman model provides a means to simulate nutrient uptake once information on root system characteristics, nutrient uptake, and soil nutrient supply are developed. Objectives of this study were to determine during a growing season: (i) root growth for 1-yr-old black cherry (Prunus serotina Ehrh.), northern red oak (Quercus rubra L.), and red maple (Acer rubrum L.) seedlings; (ii) net plant increase in N, P, K, Ca, and Mg; (iii) soil solution and solid phase nutrient concentrations; and (iv) the influence of root growth and soil nutrient supply changes on nutrient uptake using the Barber-Cushman model. Seedlings were grown in pots containing A horizon soil from two forest sites. Measurements were made on five occasions during the growing season. Root growth averaged 41.5 cm d-1 for red maple compared with 28.0 and 16.7 cm d-1 for cherry and oak, respectively. Seventy-five percent of root growth occurred at the end of the growing season. Total plant N showed the greatest change (25-58%) due to soil source. Model simulations underestimated observed uptake by 31 to 99%. A clear relationship between soil solution nutrient concentration and plant uptake, an important assumption of the model, was not observed. Results indicate care will need to be exercised in the development and use of root growth and nutrient supply values in mechanistic models.

Supply pre‐emption, not concentration reduction, is the mechanism of competition for nutrients

“…For the traits of our base species, we set root N concentration to 10 mg N g −1 biomass, root tissue density to 2 × 10 −4 g mm −3 and median longevity to 0.5 yr. Consequently, equilibrium below‐ground productivity was equivalent to 250 g m −2 yr −1 to 10 cm depth and equilibrium biomass was 180 g m −2 , which is the equivalent of 90 roots per 100 × 100 grid. Measurements of nitrate uptake kinetics of grasses are rare and we used values measured on Acer rubrum (Kelly et al ., 2000, 2001). I max , K m and C min were set to 100 × 10 −12 mmol mm −2 s −1 , 1.0 × 10 −6 mmol mm −3 and 2.0 × 10 −9 mmol mm −3 , respectively.…”

Acquisition of phosphorus and other poorly mobile nutrients by roots. Where do plant nutrition models fail?

“…In perennial plant species, in spite of the evidence for changes in root physiological properties (Escamilla and Comerford 2000; Kelly et al 2001), most studies used similar models as those developed for annual plants to simulate nutrient acquisition (Cropper and Comerford 2005;Gregory 2006;Kabba et al 2009;Kelly et al 1992;Lin and Kelly 2010). To satisfy the hypothesis of stability of plant physiological properties, most of these works on perennial plant species were conducted in controlled conditions, i.e.…”

“…mesocosm, for short time periods ranging from several weeks to months. Under these conditions, adequate simulations of nutrient uptake for several perennial species such as loblolly pine (Pinus taeda, Kelly et al 2001), maritime pine (Pinus pinaster, Jonard et al 2010) or poplar (Populus tremula, Kelly and Ericsson 2003) were performed when soil nutrient availability was high. However, such results obtained over short time periods can hardly be used to estimate nutrient acquisition over longer study periods.…”

“…However, such results obtained over short time periods can hardly be used to estimate nutrient acquisition over longer study periods. Kelly et al (2001) clearly demonstrated for red maple (Acer rubrum) and red oak (Quercus rubra) that plant nutrition models successfully predict Ca acquisition at two months of age, but consistently overestimate, in average by 99%, Ca acquisition at 18 months of age. These authors suggested that such discrepancy between measured and simulated values of Ca acquisition was caused by the inability of plant nutrition models to account for the decrease in Ca uptake capacity of older roots, which is due to the suberisation of the endodermis.…”

Phosphorus availability in boreal forest soils: A geochemical and nutrient uptake modeling approach

“…Mechanistic nutrient uptake modeling has been shown to successfully estimate availability of plant nutrients from soils (Barber, 1995;Tinker and Nye, 2000). The Cushman-Barber simulation model (Barber, 1995) has been used to predict P uptake in both agronomic crop species (Chen and Barber, 1990;Lu and Miller, 1994) and woody plant species (Kelly et al, 1992(Kelly et al, , 2001. The Cushman-Barber model uses three parameters to describe the soil nutrient supply process: initial concentration, buffering capacity, and diffusion coefficient.…”