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综合新闻 |
| 鄂尔多斯生态站人员在降水对植物N和C库影响方面的研究被Biogeosciences接收 |
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时间: 2015-01-30 点击率: 80362 |
Ye et al., 2015. Divergence of above and belowground C and N pool within predominant plant species along two precipitation gradients in North China. Biogeosciences, 12, 457-465.
生态系统C、N循环的耦合是生物地球化学循环的组成部分，驱动着生态系统食物网的结构。然而，因为植物地上下部分元素含量和生物量的变化，沿着降水梯度，可能存在植物C和N库的偏移现象。有证据表明，随着干旱的增加，植物根系生物量和叶N浓度均会增加。如果这种变化的程度相等的话，叶N浓度增加的效应会抵消生物量减少的效应，植物的地上地下N总量的比值会保持不变。本研究比较了中国内蒙古2条降水梯度样带上3种优势植物种地上和地下N和C库的变化趋势，发现其中2个植物种（大针茅和油蒿）N和C库的地上下比值均保持不变，而本氏针茅叶N浓度的增加远比生物量减少的程度要低，从而导致了干旱区地上C库比例不变而地上N库的比例明显减少。这意味着在种群水平上，降水使得植物C和N库发生的解耦合，二者的变化趋势不一致。而降水的这种解耦合作用具有种间特异性。
The coupling of carbon cycle and nitrogen cycle drives food web structure and biogeochemistry of an ecosystem. However, across precipitation gradients, there may be a shift in C pool and N pool from above- to below-ground because of shifting plant stoichiometry and allocation. Based on previous evidence, biomass allocation to roots should increase with aridity, while leaf [N] should increase. If their effect sizes are equal, they should cancel each other out, and the above- and below-ground proportions of the N would remain constant. Here, we present the first study to explicitly compare above- and below-ground pool sizes of N and C within predominant plant species along precipitation gradients. Biomass and nutrient concentrations of leaves, stems and roots of three predominant species were measured along two major precipitation gradients in Inner Mongolia, China. Along the two gradients, the effect sizes of the biomass shifts were remarkably consistent among three predominant species. However, the size of the shift in aboveground [N] was not, leading to a species-specific pattern in above- and below-ground pool size. In two species (Stipa grandis and Artemisia ordosica) the effect sizes of biomass allocation and [N] were equal and the proportion of N of above- and below-ground did not change with aridity, but in S. bungeana the increase in leaf [N] with aridity was much weaker than the biomass shift, leading to a decrease in the proportion of N aboveground at dry sites. We have found examples of consistent N pool sizes above- and belowground and a shift to a greater proportion of belowground N in drier sites depending on the species. We suggest that precipitation gradients do potentially decouple the C and N pool, but the exact nature of the decoupling depends on the dominant species’ capacity for intraspecific variation.
http://www.biogeosciences.net/12/457/2015/bg-12-457-2015.html |
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