Richardson Andrew D, Berlyn Graeme P, Duigan Shane P
School of Forestry and Environmental Studies, Yale University, 370 Prospect Street, New Haven, CT 06511, USA.
Tree Physiol. 2003 Jun;23(8):537-44. doi: 10.1093/treephys/23.8.537.
Leaf reflectance at visible and near-infrared wavelengths (400-1000 nm) is related primarily to pigmentation, leaf structure and water content, and is an important tool for studying stress physiology and relationships between plants and their growth environment. We studied reflectance of two co-occurring Alaskan conifers, black spruce (Picea mariana (Mill.) BSP) and white spruce (Picea glauca (Moench) Voss), at elevations from 60 to 930 m a.s.l. along a latitudinal gradient from 61 degrees to 68 degrees N. Black spruce samples were collected from 24 sites and white spruce from 30 sites. Overall, reflectance spectra of the two species were similar, but from 400 to 700 nm, needle reflectance was consistently higher in black spruce than in white spruce (all P <or= 0.05). This difference is probably related to differences in epicuticular wax morphology or amount, and may represent a photoprotective mechanism in black spruce. Reflectance at visible wavelengths generally increased with elevation and latitude in both species, consistent with a general stress response. However, in a multiple regression, latitude and elevation explained only 25-45% of the total variation in the indices studied. Reflectance indices suggested that needle yellowness increased, whereas chlorophyll content and photochemical efficiency decreased with both elevation and latitude. These trends were consistent between species, but white spruce generally showed a much smaller (and insignificant) reflectance response to latitude compared with black spruce. Differences between species could be related to black spruce's ability to colonize more stressful sites and white spruce's greater competitiveness on less stressful sites, coupled with the effects of drainage and microtopography (which may vary less predictably with latitude than elevation) on species distribution. The black spruce results suggest that a 1000-m increase in elevation is roughly comparable with a 6 degrees increase in latitude.
叶片在可见光和近红外波长（400 - 1000纳米）下的反射率主要与色素沉着、叶片结构和含水量有关，是研究胁迫生理学以及植物与其生长环境之间关系的重要工具。我们研究了阿拉斯加两种共生针叶树，黑云杉（Picea mariana (Mill.) BSP）和白云杉（Picea glauca (Moench) Voss），在海拔60至930米（平均海平面）、北纬61度至68度的纬度梯度上的反射率。从24个地点采集了黑云杉样本，从30个地点采集了白云杉样本。总体而言，两个物种的反射光谱相似，但在400至700纳米范围内，黑云杉针叶的反射率始终高于白云杉（所有P≤0.05）。这种差异可能与表皮蜡质形态或数量的差异有关，可能代表了黑云杉的一种光保护机制。两个物种在可见光波长下的反射率通常都随海拔和纬度升高而增加，这与一般的胁迫反应一致。然而，在多元回归分析中，纬度和海拔仅解释了所研究指标总变异的25 - 45%。反射率指标表明，随着海拔和纬度升高，针叶黄度增加，而叶绿素含量和光化学效率降低。这些趋势在两个物种之间是一致的，但与黑云杉相比，白云杉对纬度的反射率响应通常要小得多（且不显著）。物种之间的差异可能与黑云杉在压力更大的地点定植的能力以及白云杉在压力较小的地点更强的竞争力有关，再加上排水和微地形（其随纬度的变化可能比海拔更难以预测）对物种分布的影响。黑云杉的研究结果表明，海拔升高1000米大致相当于纬度升高6度。
