Decomposition of the finest root branching orders: linking belowground dynamics to fine-root function and structure
Decomposition of the finest root branching orders: linking belowground dynamics to fine-root function and structure
复制标题
DOI：
10.1890/09-2390.1
复制
发表时间：
2011-02-01
影响因子：
6.1
通讯作者：
Eissenstat, David M.
中科院分区：
文献类型：
--
作者：
Goebel, Marc;Hobbie, Sarah E.;Eissenstat, David M.
根周转最快的是根系中最细的根（第一根级）。此外，即使是最细的根目之间，以及白色根和较老的有色根之间，组织化学也各不相同。然而，色素和顺序对根分解的影响很少被研究。我们分为三类：白色的第一和第二阶根;着色的第一和第二阶根;和着色的第三和第四阶根的前四个根订单（所有，1毫米）的四个温带树种。根被封闭在垃圾袋和埋在自己的下，并在一个34岁的共同花园在波兰的共同物种的树冠。当比较36个月内不同根序的分解时，具有较高C：N比的着色的第三和第四阶根分解得更快，损失了20-40%的质量，而着色的第一和第二阶根损失不超过20%。当比较14个月内相同根序内不同色素沉着水平的根的分解时，色素沉着（较老）的第一和第二阶根损失了10%的质量，而白色（较年轻）的第一和第二阶根损失了30%。与根系质量损失相反，一级和二级根系的含氮量下降速度比三级和四级根系快。在高阶根，N增加，在第一个10个月，从110%到近150%的初始N含量，这取决于物种，到研究结束时，N含量已恢复到初始水平。这些研究结果表明，在植物群落中，根死亡率主要是有色的第一和第二阶根，微生物分解可能会慢于估计来自散装细根垃圾袋实验，其中通常包含至少四个根订单。因此，一个更机械的理解根分解及其对生态系统碳和养分动态的贡献，需要一个根本性的转变，在实验方法，分层根样品分解沿着更功能为基础的标准，如根顺序和色素沉着，平行这些不同的根类的显着不同的longevities。
Root turnover is fastest in the finest roots of the root system (first root order). Additionally, tissue chemistry varies among even the finest root orders and between white roots and older, pigmented roots. Yet the effects of pigmentation and order on root decomposition have rarely been examined. We separated the first four root orders (all,1 mm) of four temperate tree species into three classes: white first- and second-order roots; pigmented first- and second-order roots; and pigmented third-and fourth-order roots. Roots were enclosed in litterbags and buried under their own and under a common species canopy in a 34-year-old common garden in Poland. When comparing decomposition of different root orders over 36 months, pigmented third-and fourth-order roots with a higher C:N ratio decomposed more rapidly, losing 20-40% of their mass, than pigmented first- and second-order roots, which lost no more than 20%. When comparing decomposition of roots of different levels of pigmentation within the same root order over 14 months, pigmented (older) first- and second-order roots lost; 10% of their mass, while white (younger) first- and second-order roots lost; 30%. In contrast to root mass loss, root N content declined more rapidly in the first- and second-order roots than in third-and fourth-order roots. In higher-order roots, N increased in the first 10 months from; 110% to nearly 150% of initial N content, depending on species; by the end of the study N content had returned to initial levels. These findings suggest that, in plant communities where root mortality is primarily of pigmented first- and second-order roots, microbial decomposition may be slower than estimates derived from bulk fine-root litterbag experiments, which typically contain at least four root orders. Thus, a more mechanistic understanding of root decomposition and its contribution to ecosystem carbon and nutrient dynamics requires a fundamental shift in experimental methods that stratifies root samples for decomposition along more functionally based criteria such as root order and pigmentation, which parallel the markedly different longevities of these different root classes.