Morphology, gas exchange, and chlorophyll content of longleaf pine seedlings in response to rooting volume, copper root pruning, and nitrogen supply in a container nursery

Abstract

Few pine species develop a seedling grass stage; this growth phase, characterized by strong, carrot-like taproots and a stem-less nature, poses unique challenges during nursery production. Fertilization levels beyond optimum could result in excessive diameter growth that reduces seedling quality as measured by the root bound index (RBI). We grew longleaf pine (Pinus palustris), a grass stage species, in containers of four different volumes (60-336 ml) either coated with copper oxychloride or left untreated and fertilized at low, medium, or high levels of nitrogen (N). In general, N concentration of tissues rose as N rate increased, with larger changes in concentration occurring between low and medium levels than between medium and high levels. N rate influenced root tissue N concentration less than it did stems and needles. Subtle needle color differences caused by N rate were significant, suggesting its potential utility during nursery production. As expected, seedlings grew larger as container volume increased and as N rate increased. Copper treatment, which we posited could influence the RBI, tended to increase root-collar diameter and tap root biomass and decrease total root volume. Chlorophyll abundance was affected more by N rate than by container volume or copper treatment, but photosynthesis was affected more by copper treatment than N rate or container size. Although RBI was 25 % greater for seedlings grown in small containers with high N rates than those grown in large containers with low N rates, RBI ranged only from 11 to 15 %, well below the critical 27 % threshold.

The role of stored carbohydrates and nitrogen in the growth and stress tolerance of planted forest trees

“…While researchers have emphasized dormancy and cold hardiness responses, evidence suggests that this practice may result in an increase or essentially no effect on N or NSC concentration (Grossnickle et al 1991;Tan 2007;Landhäusser et al 2012b). Cultivation density (bareroot and container) or container volume also influence reserves, with generally an increase or no effect on N concentration and content as density decreases or container volume increases (van den Driessche 1984; Robbins and Pharr 1988;Aphalo and Rikala 2003;DominguezLerena et al 2006;Oliet et al 2012;Dumroese et al 2013); effects on NSC are less well documented, though a general trend of increasing seedling dry mass as density decreases or as container volume increases suggests that NSC reserves would increase concomitantly. Winter storage conditions may also affect N or NSC reserves.…”

Functional response of Quercus robur L. to taproot pruning: a 5-year case study

“…The ability of a plant to compensate for lost roots, however, largely depends on plant species (Peter and Lehmann 2000;Tsakaldimi and Ganatsas 2006). Other factors, such as planting density, can also affect seedling root systems (Moreno and Cubera 2008), and therefore, may also modify the effect of root pruning on water and nutrient uptake (Dong et al 2016;Dumroese et al 2013;Poni et al 1992). A high stand density can contribute to the tree decline in Quercus spp.…”

The Persistence of Container Nursery Treatments on the Field Performance and Root System Morphology of Longleaf Pine Seedlings

“…The container longleaf pine seedlings we studied were cultured in a greenhouse at the United States (U.S.) Department of Agriculture Forest Service, Rocky Mountain Research Station in Moscow, ID, USA (46.7 • N, 117.0 • W) [24]. The treatments were 24 factorial combinations of four container cavity volumes, three N fertilization rates, and two copper root pruning treatments.…”

“…This treatment reduced the incidence of leaning in lodgepole pine three years after outplanting [22]. Longleaf pine seedlings cultured in Cu-coated cavities grew more higher-order roots than those in non-Cu cavities [11,20,23] and favored biomass allocation to the taproot and secondary lateral roots [20,23,24]. One year after outplanting, longleaf pine seedlings cultured in Cu-coated cavities had a larger fraction of primary lateral roots emerging from the top 5 cm of the root plug than seedlings cultured without Cu [20].…”

“…We hypothesized that the seedling quality attributes, as influenced by nursery treatments, would have persistent relationships with early and long-term seedling field performance. This study is a long-term field evaluation of the crop of longleaf pine seedlings cultured in four cavity volumes with or without Cu root pruning and with one of three N fertilization rates during production [24].…”