MARKED DIFFERENCES IN SURVIVORSHIP AMONG APPLE ROOTS OF DIFFERENT DIAMETERS

Fine roots are responsible for a substantial fraction of terrestrial net primary productivity, and a better understanding of fine root production and turnover is crucial to improving global carbon and nutrient cycling models. In most studies, roots less than 1 or 2 mm in diameter (“fine roots”) have been treated as structurally and physiologically identical individuals. We used minirhizotron data from 16-yr-old apple (Malus domestica) trees to investigate differences in life span and life history among fine roots whose diameters differed by tenths of a millimeter. We also introduced the use of Cox proportional hazards regression models to assess the effects of multiple covariates on root mortality. Overwinter survivorship differed markedly among diameter classes in both years: 3–12% for roots 0.5 mm in diameter and brown, and these roots gave rise to new white laterals during the spring root flush. Based on the considerable differences in morphology and life history within the class of roots <1 mm in diameter, we advocate the use of a functional definition for the fine root whenever possible.

[1]  D. Cox.  Regression Models and Life-Tables , 1972 .

[2]  Gordon A. Fox,et al.  Failure Time Analysis: Emergence, Flowering, Survivorship, and Other Waiting Times , 1993 .

[3]  K. Pregitzer,et al.  Relationships among root branch order, carbon, and nitrogen in four temperate species , 1997, Oecologia.

[4]  P. B. Tinker,et al.  Solute Movement in the Soil-Root System. , 1978 .

[5]  J. Aber,et al.  Decomposition dynamics of fine roots in forested ecosystems , 1984 .

[6]  G. T. Nightingale.  Effects of Temperature on Growth, Anatomy, and Metabolism of Apple and Peach Roots , 1935, Botanical Gazette.

[7]  P. Kramer.  ABSORPTION OF WATER THROUGH SUBERIZED ROOTS OF TREES. , 1946, Plant physiology.

[8]  D. Atkinson,et al.  THE ROOT-SOIL INTERFACE AND ITS SIGNIFICANCE FOR FRUIT TREE ROOTS OF DIFFERENT AGES , 1979 .

[9]  D. Pyke,et al.  Statistical Analysis of Survival and Removal Rate Experiments , 1986 .

[10]  K. Vogt,et al.  Biomass distribution and above- and below-ground production in young and mature Abiesamabilis zone ecosystems of the Washington Cascades , 1981 .

[11]  G. Head.  7 – Shedding of Roots , 1973 .

[12]  F. O. Lanphear,et al.  Refinement of the triphenyl tetrazolium chloride method of determining cold injury. , 1967, Plant physiology.

[13]  B. Berg.  Decomposition of root litter and some factors regulating the process: long-term root litter decomposition in a scots pine forest , 1984 .

[14]  J. Tromp,et al.  Spring Mobilization of Protein Nitrogen in Apple Bark , 1973 .

[15]  P. Millard,et al.  The Effect of the Autumn Senescence of Leaves on the Internal Cycling of Nitrogen for the Spring Growth of Apple Trees , 1989 .

[16]  A. Fitter,et al.  The ecological significance of root system architecture: an economic approach. , 1991 .

[17]  P. Allison.  Survival analysis using the SAS system : a practical guide , 1995 .

[18]  C. Peterson,et al.  Root browning in Pinus banksiana Lamb. and Eucalyptus pilularis Sm. 1: Anatomy and permeability of the white and tannin zones , 1995 .

[19]  J. Palta,et al.  Influences of Water Status, Temperature, and Root Age on Daily Patterns of Root Respiration for Two Cactus Species , 1989 .

[20]  R. Mitchell,et al.  Accuracy of Visible and Ultraviolet Light for Estimating Live Root Proportions with Minirhizotrons , 1995 .

[21]  J. Grace,et al.  Estimating fine-root production and turnover from biomass and decomposition data: a compartment–flow model , 1987 .

[22]  W. S. Rogers.  Amount of Cortical and Epidermal Tissue Shed From Roots of Apple , 1968 .

[23]  Jeffrey S. Reid,et al.  Root demography in kiwifruit (Actinidia deliciosa) , 1993 .

[24]  A. Cantor,et al.  Extending SAS Survival Analysis Techniques for Medical Research , 1997 .

[25]  K. Vogt,et al.  Production, Turnover, and Nutrient Dynamics of Above- and Belowground Detritus of World Forests , 1986 .

[26]  D. Atkinson.  Spatial and temporal aspects of root distribution as indicated by the use of a root observation laboratory , 1985 .

[27]  W. S. Rogers.  Root Studies VIII. Apple Root Growth in Relation to Rootstock, Soil, Seasonal and Climatic Factors , 1940 .

[28]  S. Kandiah.  Turnover of Carbohydrates in Relation to Growth in Apple Trees. II. Distribution of 14C Assimilates Labelled in Autumn, Spring and Summer , 1979 .

[29]  R. Yanai,et al.  The Ecology of Root Lifespan , 1997 .

[30]  G. Head.  Estimating Seasonal Changes in The Quantity of White Unsuberized Root on Fruit Trees , 1966 .

[31]  Kurt S. Pregitzer,et al.  THE DEMOGRAPHY OF FINE ROOTS IN A NORTHERN HARDWOOD FOREST , 1992 .

[32]  G. Henderson,et al.  Organic Matter and Nutrients Associated with Fine Root Turnover in a White Oak Stand , 1987, Forest Science.

[33]  E. Parker,et al.  WEEKLY ABSORPTION OF NITRATE BY YOUNG, BEARING ORANGE TREES GROWING OUT OF DOORS IN SOLUTION CULTURES. , 1942, Plant physiology.

[34]  J. Marshall,et al.  Predicting fine root production and turnover by monitoring root starch and soil temperature , 1985 .

[35]  K. Pregitzer,et al.  The demography of fine roots in response to patches of water and nitrogen. , 1993, The New phytologist.

[36]  K. Pregitzer,et al.  Patterns of fine root mortality in two sugar maple forests , 1993, Nature.

[37]  V. Brown,et al.  Insect herbivory below ground. , 1990 .

[38]  Veronica C. Lessard,et al.  Variation in sugar maple root respiration with root diameter and soil depth. , 1998, Tree physiology.

[39]  T. Fahey,et al.  Efficiency of Nutrient Acquisition by Fine Roots and Mycorrhizae , 1995 .

[40]  P. M. Cortes,et al.  Root cortex death and subsequent initiation and growth of lateral roots from bare steles of chickpeas , 1995 .

[41]  F. J. Crider.  SELECTIVE ABSORPTION OF IONS NOT CONFINED TO YOUNG ROOTLETS. , 1933, Science.

[42]  J. Aber,et al.  Assessing the role of fine roots in carbon and nutrient cycling. , 1993, Trends in ecology & evolution.

[43]  J. Devereux Joslin,et al.  Disturbances During Minirhizotron Installation Can Affect Root Observation Data , 1999 .

[44]  O. Andrén,et al.  Fine-root production and mortality in degraded vegetation in horqin sandy rangeland in Inner Mongolia, China , 1995 .

[45]  J. Bryant,et al.  REGULATION OF FINE ROOT DYNAMICS BY MAMMALIAN BROWSERS IN EARLY SUCCESSIONAL ALASKAN TAIGA FORESTS , 1998 .

[46]  R. B. Jackson,et al.  A global budget for fine root biomass, surface area, and nutrient contents. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[47]  T. Kätterer,et al.  Fine-root dynamics, soil moisture and soil carbon content in a Eucalyptus globulus plantation under different irrigation and fertilisation regimes , 1995 .

[48]  J. Considine,et al.  Suberization and browning of grapevine roots , 1981 .