Carey Eileen V, Callaway Ragan M, DeLucia Evan H
Department of Plant Biology, University of Illinois, 265 Morrill Hall, 505 S. Goodwin Ave., Urbana, IL 61801, USA e-mail:
Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA, , , , , , US.
Oecologia. 1997 Jun;111(1):19-25. doi: 10.1007/s004420050203.
We examined the effects of climate and allocation patterns on stem respiration in ponderosa pine (Pinus ponderosa) growing on identical substrate in the cool, moist Sierra Nevada mountains and the warm, dry, Great Basin Desert. These environments are representative of current climatic conditions and those predicted to accompany a doubling of atmospheric CO, respectively, throughout the range of many western north American conifers. A previous study found that trees growing in the desert allocate proportionally more biomass to sapwood and less to leaf area than montane trees. We tested the hypothesis that respiration rates of sapwood are lower in desert trees than in montane trees due to reduced stem maintenance respiration (physiological acclimation) or reduced construction cost of stem tissue (structural acclimation). Maintenance respiration per unit sapwood volume at 15°C did not differ between populations (desert: 6.39 ± 1.14 SE μmol m s, montane: 6.54 ± 1.13 SE μmol m s, P = 0.71) and declined with increasing stem diameter (P = 0.001). The temperature coefficient of respiration (Q ) varied seasonally within both environments (P = 0.05). Construction cost of stem sapwood was the same in both environments (desert: 1.46 ± 0.009 SE g glucose g sapwood, montane: 1.48 ± 0.009 SE glucose g sapwood, P = 0.14). Annual construction respiration calculated from construction cost, percent carbon and relative growth rate was greater in montane populations due to higher growth rates. These data provide no evidence of respiratory acclimation by desert trees. Estimated yearly stem maintenance respiration was greater in large desert trees than in large montane trees because of higher temperatures in the desert and because of increased allocation of biomass to sapwood. By analogy, these data suggest that under predicted increases in temperature and aridity, potential increases in aboveground carbon gain due to enhanced photosynthetic rates may be partially offset by increases in maintenance respiration in large trees growing in CO-enriched atmospheres.
我们研究了气候和分配模式对生长在内华达山脉凉爽、湿润地区以及大盆地沙漠温暖、干燥地区相同基质上的黄松（Pinus ponderosa）树干呼吸的影响。这些环境分别代表了当前的气候条件以及预计在北美西部许多针叶树分布范围内大气二氧化碳浓度翻倍时伴随的气候条件。先前的一项研究发现，与山地树木相比，生长在沙漠中的树木将更多比例的生物量分配给边材，而分配给叶面积的生物量较少。我们检验了这样一个假设：由于树干维持呼吸减少（生理适应）或树干组织构建成本降低（结构适应），沙漠树木边材的呼吸速率低于山地树木。在15°C时，单位边材体积的维持呼吸在不同种群间没有差异（沙漠：6.39±1.14标准误微摩尔·米⁻²·秒⁻¹，山地：6.54±1.13标准误微摩尔·米⁻²·秒⁻¹，P = 0.71），并且随着树干直径的增加而下降（P = 0.001）。呼吸作用的温度系数（Q）在两种环境中均随季节变化（P = 0.05）。两种环境中树干边材的构建成本相同（沙漠：1.46±0.009标准误克葡萄糖·克边材，山地：1.48±0.009标准误克葡萄糖·克边材，P = 0.14）。由于生长速率较高，根据构建成本、碳百分比和相对生长速率计算得出的山地种群的年构建呼吸量更大。这些数据没有提供沙漠树木呼吸适应的证据。由于沙漠温度较高以及生物量向边材的分配增加，估计大型沙漠树木的年树干维持呼吸量大于大型山地树木。由此类推，这些数据表明，在预计的温度升高和干旱加剧的情况下，在二氧化碳浓度升高的大气中生长的大型树木，由于光合速率提高而导致的地上碳增益的潜在增加可能会被维持呼吸的增加部分抵消。
