Spectral reflectance and photosynthetic properties of Betula papyrifera (Betulaceae) leaves along an elevational gradient on Mt. Mansfield, Vermont, USA.

We studied relationships between spectral reflectance and photosynthesis of mountain paper birch, Betula papyrifera var. cordifolia (Regel) Fern., leaves from three different elevations on Mt. Mansfield (summit elevation 1339 m above sea level) in the Green Mountains of Vermont, USA. The different reflectance indices we used all suggested progressively increasing stress with increasing elevation. The photochemical reflectance index (PRI) indicated lower photosynthetic radiation use efficiency at higher elevations, the red edge position (λRE) indicated lower chlorophyll concentrations at higher elevations, and the structure-independent pigment index (SIPI) indicated a higher carotenoid : chlorophyll a ratio at higher elevations. The rate of change in these indices with changes in elevation was much higher than we have observed in our studies of red spruce and balsam fir reflectance along a similar elevational gradient; we take this to be an indicator of the greater susceptibility of paper birch to elevation-related stressors compared to the very stress-tolerant conifers. At all light levels, photosynthesis decreased with increasing elevation; this pattern was most noticeable in the light-saturated rate of photosynthesis (A(sat)), which was nearly twice as high in low-elevation leaves (17.0 ± 1.0 μmol·m(-2)·s(-1)) than in high-elevation leaves. The quantum yield of photosynthesis (Φ) exhibited a similar trend. Furthermore, the highest elevation leaves showed a much sharper transition from the light-limited to the light-saturated part of the light response curve than did the lowest elevation leaves. The photochemical reflectance index was highly correlated with A(sat) (r(2) = 0.99) and Φ (r(2) = 0.96). In addition to contributing to our knowledge of the ecophysiology of paper birch along a steep environmental gradient, these results are further evidence of the usefulness of reflectance measures for the rapid and noninvasive detection of plant stress, especially when used in conjunction with direct measurements of photosynthesis.

[1]  A. Richardson,et al.  Spectral reflectance of Picea rubens (Pinaceae) and Abies balsamea (Pinaceae) needles along an elevational gradient, Mt. Moosilauke, New Hampshire, USA. , 2001, American journal of botany.

[2]  J. Dungan,et al.  Exploring the relationship between reflectance red edge and chlorophyll content in slash pine. , 1990, Tree physiology.

[3]  J. Peñuelas,et al.  Assessment of photosynthetic radiation‐use efficiency with spectral reflectance , 1995 .

[4]  G. Berlyn,et al.  Polyploids and their structural and physiological characteristics relative to water deficit in Betula papyrifera (Betulaceae) , 1996 .

[5]  L. W. Jackson.  Effect of Shade on Leaf Structure of Deciduous Tree Species , 1967 .

[6]  R. Jackson.  Remote sensing of biotic and abiotic plant stress , 1986 .

[7]  John A. Gamon,et al.  Assessing leaf pigment content and activity with a reflectometer , 1999 .

[8]  A. Gitelson,et al.  Spectral reflectance changes associated with autumn senescence of Aesculus hippocastanum L. and Acer platanoides L. leaves. Spectral features and relation to chlorophyll estimation , 1994 .

[9]  Josep Peñuelas,et al.  Altitudinal differences in UV absorbance, UV reflectance and related morphological traits of Quercus ilex and Rhododendron ferrugineum in the Mediterranean region , 1999, Plant Ecology.

[10]  C. Field,et al.  A narrow-waveband spectral index that tracks diurnal changes in photosynthetic efficiency , 1992 .

[11]  J. Gamon,et al.  The photochemical reflectance index: an optical indicator of photosynthetic radiation use efficiency across species, functional types, and nutrient levels , 1997, Oecologia.

[12]  J. Fryer,et al.  Microevolution of the photosynthetic temperature optimum in relation to the elevational complex gradient , 1972 .

[13]  A. Gitelson,et al.  Detection of Red Edge Position and Chlorophyll Content by Reflectance Measurements Near 700 nm , 1996 .

[14]  Mary E. Martin,et al.  HIGH SPECTRAL RESOLUTION REMOTE SENSING OF FOREST CANOPY LIGNIN, NITROGEN, AND ECOSYSTEM PROCESSES , 1997 .

[15]  B. Demmig‐Adams,et al.  The role of xanthophyll cycle carotenoids in the protection of photosynthesis , 1996 .

[16]  T. Siccama.  Vegetation, Soil, and Climate on the Green Mountains of Vermont , 1974 .

[17]  P. D. Körner.  Alpine Plant Life , 1999, Springer Berlin Heidelberg.

[18]  Josep Peñuelas,et al.  Visible and near-infrared reflectance techniques for diagnosing plant physiological status , 1998 .

[19]  Mark G. Tjoelker,et al.  Growth and physiology of Picea abies populations from elevational transects: common garden evidence for altitudinal ecotypes and cold adaptation , 1998 .

[20]  J. Peñuelas,et al.  Relationship between photosynthetic radiation-use efficiency of barley canopies and the photochemical reflectance index (PRI) , 1996 .

[21]  Gregory A. Carter,et al.  Responses of leaf spectral reflectance to plant stress. , 1993 .

[22]  D. Hollinger,et al.  Temperature and Evapotranspiration Gradients of the White Mountains, New Hampshire, U.S.A. , 1984 .

[23]  L. Olander,et al.  Changes in leaf structure in relation to crown position and tree size of Betula papyrifera within fire-origin stands of interior cedar-hemlock , 1998 .