Partitioning of nitrate uptake between trees and understory in oak forests
Partitioning of nitrate uptake between trees and understory in oak forests
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橡树林中树木和林下的硝酸盐吸收分配
DOI：
10.1016/s0378-1127(02)00544-3
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发表时间：
2003
影响因子：
3.7
通讯作者：
U. Falkengren‐Grerup
中科院分区：
文献类型：
--
作者：
M. O. Olsson;U. Falkengren‐Grerup
在乔木层以栎类为主的3种落叶林中，测定了春季、初夏和夏末3个季节的硝酸还原酶活性（NRA）。林下植物地上和地下生物量以及乔木层叶和根的硝态氮同化能力分别以单位生物量和单位面积硝态氮同化能力计算。林下植物地上部分单位生物量的NRA值在0.56 ~ 13.6μmol NO2−g−1dwh− 1之间，春季最高。每单位地下生物量的NRA范围为0.12至0.94μmol NO2−g−1dwh−1。对于叶，每单位生物量的NRA在0.27和3.51μmol NO2−g−1dwh−1之间变化，对于根，在0.14和0.91μmol NO2−g−1dwh−1之间变化。春季，当硝化作用较高时，超过90%的硝酸盐总吸收量（以NRA m-2测量）是由林下植物吸收的，但未释放的树木几乎没有表现出活动。在其他时期比春天的测量是罕见的文献，但这里报道的结果表明，在夏季的林下植被的重要性，因为每单位生物量的林下植被层的NRA是相当高的。NRA m-2总量的15%~ 50%分布在林下植被中。林下植被和乔木层改变硝酸盐还原酶与硝酸盐有效性，从而防止硝酸盐淋溶的能力进行了进一步讨论。
The nitrate reductase activity (NRA) was measured during spring, early summer and late summer in three deciduous forests, where the tree layer was dominated by oak. The nitrate assimilation capacities of the compartments of the above-ground and below-ground biomass of the understory and of the leaves and roots of the tree layer were calculated as NRA per unit biomass and NRA per unit area. The NRA per unit biomass in the above-ground parts of the understory ranged from 0.56 to 13.6μmol NO2−g−1dwh−1and was highest in the spring at all sites. The NRA per unit below-ground biomass ranged from 0.12 to 0.94μmol NO2−g−1dwh−1. For leaves, the NRA per unit biomass varied between 0.27 and 3.51μmol NO2−g−1dwh−1, and for the roots between 0.14 and 0.91μmol NO2−g−1dwh−1. Over 90% of the total nitrate uptake (measured as NRA m−2) was performed by the understory in the spring, when the nitrification is high, but the unleafed trees showed little activity. Measurements during other periods than spring are scarce in the literature, but results reported here demonstrate the importance of the understory also during the summer, as the NRA per unit biomass of the understory layer was quite high. Fifteen to 50% of the total NRA m−2was found in the understory. The capability of the understory and the tree layer to change NRA with nitrate availability and thereby prevent nitrate leaching is further discussed.