Genotypic effects of fertilization on seedling sweetgum biomass allocation, N uptake, and N use efficiency.

Scott X Chang,Daniel J Robison

doi:10.1100/tsw.2001.275

Abstract

Screening and selecting tree genotypes that are responsive to N additions and that have high nutrient use efficiencies can provide better genetic material for short-rotation plantation establishment. A pot experiment was conducted to test the hypotheses that (1) sweetgum (Liquidambar styraciflua L.) families have different patterns in biomass production and allocation, N uptake, and N use efficiency (NUE), because of their differences in growth strategies, and (2) sweetgum families that are more responsive to N additions will also have greater nutrient use efficiencies. Seedlings from two half-sib families (F10022 and F10023) that were known to have contrasting responses to fertility and other stress treatments were used for an experiment with two levels of N (0 vs. 100 kg N/ha equivalent) and two levels of P (0 vs. 50 kg P/ha equivalent) in a split-plot design. Sweetgum seedlings responded to N and P treatments rapidly, with increases in both size and biomass production, and those responses were greater with F10023 than with F10022. Growth response to N application was particularly strong. N and P application increased the proportional allocation of biomass to leaves. Under increased N supply, P application increased foliar N concentration and content, as well as total N uptake by the seedlings. However, NUE was decreased by N addition and was higher in F10023 than in F10022 when P was not limiting. A better understanding of genotype by fertility interactions is important in selecting genotypes for specific site conditions and for optimizing nutrient use in forestry production.

Highlights

Intensive forest management and short-rotation tree crop production will increasingly rely on genetic improvement to capture site resources and on developing genotypes that are suited to specific sites[1]
Proportional stem biomass production was greater in F10022 than in F10023 (p < 0.05); %stem biomass was not affected by the N or P treatment
In a pot experiment studied over one growing season, fertilization with N and P increased sweetgum total seedling biomass production and its allocation into foliage and, to a lesser extent, branches, while less was allocated into roots

Summary

Introduction

Intensive forest management and short-rotation tree crop production will increasingly rely on genetic improvement to capture site resources and on developing genotypes that are suited to specific sites[1]. In agronomic crop production systems, genotypes are increasingly being selected for specific traits; for example, (1) genotype has been found to have a strong influence on wheat quality and good quality lines are recommended for specific environments[2], (2) genotype × N interaction in wheat was significant for grain yield, aboveground dry matter, and number of kernels per spike[3], and (3) tomato genotypes showed strong differences in utilization and assimilation of foliar NO3 and tomato yields[4] Approaches similar to those used in agronomic crops have been explored in forestry to improve forest site productivity and to efficiently capture site resources[5,6,7,8]. Potential negative environmental problems may be avoided or minimized if intensive management is practiced

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