Linking above- and belowground phenology of hybrid walnut growing along a climatic gradient in temperate agroforestry systems
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Background and aims
Plant phenology is a sensitive indicator of plant response to climate change. Observations of phenological events belowground for most ecosystems are difficult to obtain and very little is known about the relationship between tree shoot and root phenology. We examined the influence of environmental factors on fine root production and mortality in relation with shoot phenology in hybrid walnut trees (Juglans sp.) growing in three different climates (oceanic, continental and Mediterranean) along a latitudinal gradient in France.
Eight rhizotrons were installed at each site for 21 months to monitor tree root dynamics. Root elongation rate (RER), root initiation quantity (RIQ) and root mortality quantity (RMQ) were recorded frequently using a scanner and time-lapse camera. Leaf phenology and stem radial growth were also measured. Fine roots were classified by topological order and 0–1 mm, 1–2 mm and 2–5 mm diameter classes and fine root longevity and risk of mortality were calculated during different periods over the year.
Root growth was not synchronous with leaf phenology in any climate or either year, but was synchronous with stem growth during the late growing season. A distinct bimodal pattern of root growth was observed during the aerial growing season. Mean RER was driven by soil temperature measured in the month preceding root growth in the oceanic climate site only. However, mean RER was significantly correlated with mean soil water potential measured in the month preceding root growth at both Mediterranean (positive relationship) and oceanic (negative relationship) sites. Mean RIQ was significantly higher at both continental and Mediterranean sites compared to the oceanic site. Soil temperature was a driver of mean RIQ during the late growing season at continental and Mediterranean sites only. Mean RMQ increased significantly with decreasing soil water potential during the late aerial growing season at the continental site only. Mean root longevity at the continental site was significantly greater than for roots at the oceanic and Mediterranean sites. Roots in the 0–1 mm and 1–2 mm diameter classes lived for significantly shorter periods compared to those in the 2–5 mm diameter class. First order roots (i.e. the primary or parents roots) lived longer than lateral branch roots at the Mediterranean site only and first order roots in the 0–1 mm diameter class had 44.5% less risk of mortality than that of lateral roots for the same class of diameter.
We conclude that factors driving root RER were not the same between climates. Soil temperature was the best predictor of root initiation at continental and Mediterranean sites only, but drivers of root mortality remained largely undetermined.
KeywordsAgroforestry Rhizotron Root elongation Initiation Mortality Longevity
Soil water potential
Early growing season
Late growing season
Root elongation rate
Root initiation quantity
Root mortality quantity
Thanks are due to Jérôme Nespoulous, Luis Merino Martin and Merlin Ramel (INRA) for technical assistance, to Camille Béral (Agroof, France) for help finding field sites and to the farmers M. Queuille and M. Becue for letting us work in their agroforests.
Compliance with ethical standards
The authors declare that they have no competing interests.
Availability of data and materials
The datasets about root survivorship generated and/or analyzed during the current study are available in the [Zenodo] repository, “https://zenodo.org/record/842737#.WbrdOrJJaCj” . The other datasets generated and/or analyzed during the current study are available from the corresponding author on request.
- Broschat TK (1998) Root and shoot growth patterns in four palm species and their relationships with air and soil temperatures. Hortscience 33:995–998Google Scholar
- Comas LH, Anderson L, Dunst R, Lakso A, Eissenstat D (2005) Canopy and environmental control of root dynamics in a long‐term study of Concord grape. New Phytol 167:829–40Google Scholar
- Gaudinski JB, Torn MS, Riley W, Swanston C, Trumbore SE, et al (2009) Use of stored carbon reserves in growth of temperate tree roots and leaf buds: analyses using radiocarbon measurements and modeling. Glob Chang Biol 15:992–1014Google Scholar
- Harris JR, Bassuk NL, Zobel RW, Whitlow TH (1995) Root and shoot growth periodicity of green ash, scarlet oak, turkish hazelnut, and tree lilac. J Am Soc Hortic Sci 120:211–216Google Scholar
- Hooker JE, Black KE, Perry RL, Atkinson D (1995) Arbuscular mycorrhizal fungi induced alteration to root longevity in poplar. Plant Soil 172:327–329Google Scholar
- Huck MG, Taylor HM (1982) The rhizotron as a tool for root research. In: Brady NC (ed) Advances in agronomy. Academic Press, Cambridge, pp 1–35Google Scholar
- Huck M, Hoogenboom G, Peterson CM (1987) Soybean root senescence under drought stress. In: Taylor HM (ed) Minirhizotron observation tubes: Methods and applications for measuring rhizosphere dynamics. ASA Special Publication No. 50. ASA, CSSA, SSSA, Madison, pp 109–121Google Scholar
- Kuhns MR, Garrett HE, Teskey RO, Hinckley TM (1985) Root-growth of black walnut trees related to soil-temperature, soil-water potential, and leaf water potential. For Sci 31:617–629Google Scholar
- Mapelli S, Lombardi L, Brambilla I, Iulini A, Bertani A. (1995–1996) III International Walnut Congress 4421995:129–36Google Scholar
- M’bou AT, Jourdan C, Deleporte P, Nouvellon Y, Saint-André L, et al (2008) Root elongation in tropical Eucalyptus plantations: effect of soil water content. Ann For Sci 65:609–09Google Scholar
- Najar A, Landhäusser SM, Whitehill JG, Bonello P, Erbilgin N (2014) Reserves accumulated in nonphotosynthetic organs during the previous growing season drive plant defenses and growth in aspen in the subsequent growing season. J Chem Ecol 40:21–30Google Scholar
- Niu YF, Chai RS, Jin GL, Wang H, Tang CX, Zhang YS (2013) Responses of root architecture development to low phosphorus availability: a review. Ann Bot 112:391–408Google Scholar
- Norby RJ, Jackson RB (2000) Root dynamics and global change: seeking an ecosystem perspective. New Phytol 147:3–12Google Scholar
- Olesinski J, Lavigne MB, Krasowski MJ (2011) Effects of soil moisture manipulations on fine root dynamics in a mature balsam fir (Abies balsamea L. Mill.) forest. Tree Physiol 31:339–48Google Scholar
- Psarras G, Merwin IA, Lakso AN, Ray JA (2000) Root growth phenology, root longevity, and Rhizosphere respiration of field grown Mutsu' apple trees on Malling rootstock. J Am Soc Hortic Sci 125:596–602Google Scholar
- R Development Core Team (2013) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Reich P, Teskey R, Johnson P, Hinckley T (1980) Periodic root and shoot growth in oak. For Sci 26:590–598Google Scholar
- Strand AE, Pritchard SG, McCormack ML, Davis MA, Oren R (2008) Irreconcilable differences: fineroot life spans and soil carbon persistence. Science 319Google Scholar
- Tanner SC, Reighard GL, Wells CE (2006) Soil treatments differentially affect peach tree root development and demography in a replant site. In: Infante R (ed) Proceedings of the VIth international peach symposium, Acta, pp 381–387Google Scholar
- Vogt KA, Vogt DJ, Bloomfield J (1998) Analysis of some direct and indirect methods for estimating root biomass and production of forests at an ecosystem level. In: Box J Jr (ed) Root demographics and their efficiencies in sustainable agriculture, grasslands and forest ecosystems. Springer Netherlands, Berlin, pp 687–720CrossRefGoogle Scholar