Linkages Between Nutrient Resorption and Ecological Stoichiometry and Homeostasis Along a Chronosequence of Mongolian Pine Plantations.

Kai Wang,Lining Song,Yihang Li,G Geoff Wang,Tao Yan,Risheng Zhang

doi:10.3389/fpls.2021.692683

Abstract

Nutrient resorption is an important strategy for nutrient conservation, particularly under conditions of nutrient limitation. However, changes in nutrient resorption efficiency with stand development and the associated correlations with ecological stoichiometry and homeostasis are poorly understood. In the study, the authors measured carbon (C), nitrogen (N), and phosphorus (P) concentrations in soil and in green and senesced needles along a chronosequence of Mongolian pine (Pinus sylvestris var. mongolica) plantations (12-, 22-, 31-, 42-, 52-, and 59-year-old) in Horqin Sandy Land of China, calculated N and P resorption efficiency (NRE and PRE, respectively), and homeostasis coefficient. The authors found that soil organic C and total N concentrations increased, but soil total P and available P concentrations decreased with stand age. Green needle N concentrations and N:P ratios as well as senesced needle C:N ratios, NRE, and PRE exhibited patterns of initial increase and subsequent decline with stand age, whereas green needle C:N ratios and senesced needle N concentrations, and N:P ratios exhibited the opposite pattern. NRE was positively correlated with N concentration and N:P ratio, but negatively correlated with C:N ratio in green needles, whereas the opposite pattern was observed in senesced needles. PRE was negatively correlated with senesced needle P concentration, soil-available N concentration, and available N:P ratio. The homeostatic coefficient of N:P was greater when including all stand ages than when including only those younger than 42 years. These findings indicate that tree growth may change from tending to be N limited to tending to be P limited along the Mongolian pine plantation chronosequence. Nutrient resorption was coupled strongly to tree growth and development, whereas it played a lesser role in maintaining stoichiometric homeostasis across the plantation chronosequence. Therefore, adaptive fertilization management strategies should be applied for the sustainable development of Mongolian pine plantations.

Highlights

Nitrogen (N) and phosphorus (P) play important roles in plant growth and metabolism, and deficiencies thereof have been shown to strongly limit forest growth and productivity (Vitousek et al, 2010; See et al, 2015)
We found that soil organic C and total N concentrations in topsoil increased along a chronosequence of Mongolian pine plantations (Table 2), which is in agreement with Li et al (2012), who reported that Mongolian pine plantations enhanced soil C and N concentrations in the Horqin Sandy Land
The opposite patterns of change were found by Peng et al (2016), who reported that Amaranthus mangostanus displayed contrasting nutrient homeostasis and resorption responses to environmental nutrient availability across growth stages. These findings indicate that nutrient resorption may play a lesser role in maintaining stoichiometric homeostasis across the chronosequence of Mongolian pine plantations

Summary

Introduction

Nitrogen (N) and phosphorus (P) play important roles in plant growth and metabolism, and deficiencies thereof have been shown to strongly limit forest growth and productivity (Vitousek et al, 2010; See et al, 2015). During forest stand development, plant photosynthetic characteristics, nutrition requirements, and soil nutrient supply often remain changed (Zhang et al, 2018) These variations in soil and plant nutrient status may cause a transition in the type of nutrient limitation; N limitation often occurs in young forests, whereas P limitation tends to progressively occur in aging forests, in areas with nutrient deficiencies (Yan et al, 2018; Deng et al, 2019). Such changes in nutrient limitation status across a forest chronosequence would have substantial effects on plant survival and growth. Stoichiometric homeostasis may have different limits in response to changing environments (Meunier et al, 2014), while the degree of homeostasis varies during different growth stages in plants (Peng et al, 2016)

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