Fine root morphology and growth in response to nitrogen addition through drip fertigation in a Populus × euramericana “Guariento” plantation over multiple years

Abstract

& Key message Nitrogen addition through drip fertigation to a poplar plantation (Populus × euramericana BGuariento^) promoted fine root growth only in the early period. The relationship between root growth and soil N content was positive in the first 2 years, but became negative in the third year when the soil N availability had substantially increased. & Context Nitrogen (N) deficiency is common in forest soils, and N addition is sometimes applied in the case of intensive plantations. There is a need to better document the impact of N addition through the high-efficiency fertilization technique on fine root morphology and growth, given their importance for the uptake of nutrients and for tree growth. & Aims We aimed to quantitatively investigate the responses of fine roots in morphology and growth to N addition through surface drip fertigation over multiple years in a Populus × euramericana BGuariento^plantation. & Methods A field experiment that included four drip fertigation treatments with N addition levels (0, 60, 120, and 180 kg N ha −1 year −1 ) was conducted for three successive years. A coring method was used to sample soils and quantify the root morphological traits and soil N content along 0-60-cm profiles. & Results The root biomass density, length, surface area, specific length, and tissue density were significantly higher in the N addition treatments than those in the control after the first year, but the positive effect decreased in the second year. In the third year, root biomass in the N addition treatments was even lower by 11-39% than that in the control. The relationship between root growth and soil N content was also positive in the first 2 years and negative in the third year. & Conclusion N addition promoted fine root growth mainly in the shallow soil and in the early period of experiment. The relationship between root growth and soil N content became negative in the third year when the soil N availability had substantially increased. It is suggested that fine roots adjust their growth and morphology in response to N availability varying along the soil profile and with the fertilization duration.

Nitrogen addition increases root biomass allocation and changes functional traits of two dominant tree species in North China

“…These results suggested that soil N availability and root N uptake played important roles in the root growth of P. tabuliformis, which made roots absorb more resources and directly changed the plant biomass allocation pattern (Davis et al 2000). Despite directly inhibiting the R/S ratio, N addition could indirectly increase it through increasing SNC and RNC, same as other studies (Yan et al 2019). As for F. chinensis, on the one hand, N could indirectly increase R/S ratio through its positive effects on RNC and SNC, similar to P. tabuliformis.…”

The morphological and chemical properties of fine roots respond to nitrogen addition in a temperate Schrenk’s spruce (Picea schrenkiana) forest

“…However, the deeper soil layers contain leached nutrients (Fig. 1), which suppress the growth of fine roots 30 . Furthermore, surface soil layers are affected first when N is added, the foraging response of fine roots then leads to a change the fine roots in surface layer, which mediates the vertical fine root distribution 40 .…”

“…Some studies have found that the effects of N deposition are greater on lower order roots than on higher order roots 9,29 . Other studies have shown that the biomass of fine roots in the upper soil layers is significantly higher than that in other soil layers 15 and that N addition significantly increases the SRL and SRA of fine roots in the upper soil layer (0-30 cm) 30 . However, Yan et al 31 demonstrated that N addition reduced the SRA of fine roots.…”

Bioenergy Underground: Challenges and opportunities for phenotyping roots and the microbiome for sustainable bioenergy crop production

“…In drought studies, root development was dependent on soil saturation (Carthy et al, 2018), and lateral root growth was inhibited by PEG exposure, which may be controlled by the PtabZIP1-like (Dash et al, 2017) and PtaJAZ3 and PtaRAP2.6 (Dash et al, 2017(Dash et al, , 2018 genes. Root biomass density, length, surface area, and SRL were also stimulated by N fertilization (Yan et al, 2019), and SRL and fine:coarse root ratio were strongly influenced by the form of N used (Domenicano et al, 2011;Yan et al, 2019), reflecting the plasticity of root architectural traits in Populus. Understanding the genes and networks underlying root architectural change to the environment will allow for future selection for stress resistance.…”