Canham Charles D, Kobe Richard K, Latty Erika F, Chazdon Robin L
Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545, USA e-mail:
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA, , , , , , US.
Oecologia. 1999 Oct;121(1):1-11. doi: 10.1007/s004420050900.
We examined interspecific and intraspecific variation in tree seedling survival as a function of allocation to carbohydrate reserves and structural root biomass. We predicted that allocation to carbohydrate reserves would vary as a function of the phenology of shoot growth, because of a hypothesized tradeoff between aboveground growth and carbohydrate storage. Intraspecific variation in levels of carbohydrate reserves was induced through experimental defoliation of naturally occurring, 2-year-old seedlings of four northeastern tree species -Acer rubrum, A. saccharum, Quercus rubra, and Prunus serotina- with shoot growth strategies that ranged from highly determinate to indeterminate. Allocation to root structural biomass varied among species and as a function of light, but did not respond to the defoliation treatments. Allocation to carbohydrate reserves varied among species, and the two species with the most determinate shoot growth patterns had the highest total mass of carbohydrate reserves, but not the highest concentrations. Both the total mass and concentrations of carbohydrate reserves were significantly reduced by defoliation. Seedling survival during the year following the defoliation treatments did not vary among species, but did vary dramatically in response to defoliation. In general, there was an approximately linear relationship between carbohydrate reserves and subsequent survival, but no clear relationship between allocation to root structural biomass and subsequent survival. Because of the disproportionate amounts of reserves stored in roots, we would have erroneously concluded that allocation to roots was significantly and positively related to seedling survival if we had failed to distinguish between reserves and structural biomass in roots.
我们研究了树木幼苗存活的种间和种内变异，将其作为分配到碳水化合物储备和根系结构生物量的函数。我们预测，由于假设地上生长与碳水化合物储存之间存在权衡，分配到碳水化合物储备的量会随着地上部分生长物候的变化而变化。通过对四种东北树种（红枫、糖枫、红栎和黑樱桃）自然生长的2年生幼苗进行实验性去叶处理，诱导了碳水化合物储备水平的种内变异，这些树种的地上部分生长策略从高度确定性到不确定性不等。分配到根系结构生物量的量因物种而异，并随光照而变化，但对去叶处理没有反应。分配到碳水化合物储备的量因物种而异，地上部分生长模式最具确定性的两个物种的碳水化合物储备总量最高，但浓度不是最高。去叶处理显著降低了碳水化合物储备的总量和浓度。去叶处理后的一年中，幼苗存活率在物种间没有差异，但对去叶处理的反应差异很大。一般来说，碳水化合物储备与随后的存活率之间存在近似线性关系，但分配到根系结构生物量与随后的存活率之间没有明确关系。由于根系中储存的储备量不成比例，如果我们未能区分根系中的储备和结构生物量，我们就会错误地得出结论，认为分配到根系的量与幼苗存活率显著正相关。
