Cardon Zoe G, Czaja Andrew D, Funk Jennifer L, Vitt Pati L
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, 75 N. Eagleville Road, U-43.
Department of Earth and Space Sciences, University of California, Los Angeles, CA, 90095, USA.
Oecologia. 2002 Oct;133(2):215-223. doi: 10.1007/s00442-002-1045-y. Epub 2002 Oct 1.
Patterns of root/shoot carbon allocation within plants have been studied at length. The extent, however, to which patterns of carbon allocation from shoots to roots affect the timing and quantity of organic carbon release from roots to soil is not known. We employed a novel approach to study how natural short-term variation in the allocation of carbon to roots may affect rhizosphere soil biology. Taking advantage of the semi-determinate phenology of young northern red oak (Quercus rubra L.), we examined how pulsed delivery of carbon from shoots to roots affected dynamics of soil respiration as well as microbial biomass and net nitrogen mineralization in the rhizosphere. Young Q. rubra exhibit (1) clear switches in the amount of carbon allocated below-ground that are non-destructively detected simply by observing pulsed shoot growth above-ground, and (2) multiple switches in internal carbon allocation during a single growing season, ensuring our ability to detect short-term effects of plant carbon allocation on rhizosphere biology separate from longer-term seasonal effects. In both potted oaks and oaks rooted in soil, soil respiration varied inversely with shoot flush stage through several oak shoot flushes. In addition, upon destructive harvest of potted oaks, microbial biomass in the rhizosphere of saplings with actively flushing shoots was lower than microbial biomass in the rhizosphere of saplings with shoots that were not flushing. Given that plants have evolved with their roots in contact with soil microbes, known species-specific carbon allocation patterns within plants may provide insight into interactions among roots, symbionts, and free-living microbes in the dynamic soil arena.
植物体内根/茎碳分配模式已得到充分研究。然而，茎向根的碳分配模式对根向土壤释放有机碳的时间和数量的影响程度尚不清楚。我们采用了一种新方法来研究碳向根分配的自然短期变化如何影响根际土壤生物学。利用北方红栎幼树（Quercus rubra L.）的半确定性物候特征，我们研究了茎向根的脉冲式碳输送如何影响土壤呼吸动态以及根际微生物生物量和净氮矿化。幼龄红栎表现出：（1）通过观察地上部脉冲式枝条生长就能无损检测到地下碳分配量的明显变化；（2）在单个生长季节内内部碳分配有多次变化，这确保了我们能够检测到植物碳分配对根际生物学的短期影响，而不受长期季节影响。在盆栽栎树和种植在土壤中的栎树中，通过几个栎树新梢生长期，土壤呼吸与新梢生长阶段呈负相关。此外，对盆栽栎树进行破坏性收获时，新梢活跃生长的幼树根际微生物生物量低于新梢未生长的幼树根际微生物生物量。鉴于植物在其根系与土壤微生物接触的环境中进化，植物体内已知的物种特异性碳分配模式可能有助于深入了解动态土壤环境中根、共生体和自由生活微生物之间的相互作用。
