Oak loss increases foliar nitrogen, δ15N and growth rates of Betula lenta in a northern temperate deciduous forest
Oak loss increases foliar nitrogen, δ15N and growth rates of Betula lenta in a northern temperate deciduous forest
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DOI：
10.1093/treephys/tps068
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发表时间：
2012-09-01
期刊：
影响因子：
4
通讯作者：
Griffin, Kevin L.
中科院分区：
文献类型：
--
作者：
Falxa-Raymond, Nancy;Patterson, Angelica E.;Griffin, Kevin L.
橡树林主导了美国东部的大部分地区，但由于一些威胁和橡树更新的普遍失败，它们的未来还不确定。突然失去的橡树(Quercus spp.)可能伴随着森林氮(N)循环的重大变化，对植物养分吸收和树种组成产生重要影响。在本研究中，我们测定了黑桦树(Betula lenta L.)氮素利用和生长速率的变化。在美国纽约东南部的黑岩森林里的橡树环带。数据来自9个试验区，由3个处理组成：100%橡树环剥(OG)、50%橡树环剥(O50)和对照(C)。与对照相比，橡树环带小区的叶片N浓度和N-15丰度显著增加，表明栎树的丧失显著改变了N的循环动态。随着橡树损失后矿化和硝化速率的增加，黑桦树增加了对N的吸收，这表明叶N含量更高，生长速度更快。与对照相比，O50和OG处理的叶片N浓度分别增加了15.5%和30.6%，而O50和OG处理的N-15含量分别增加了1.08‰和3.33‰(P<；0.0001)。黑桦在OG小区的生长率增加了641%，这表明该物种能够对额外的氮素供应和/或增加的光照供应做出反应。橡树的丧失和随后黑桦树生产力的增加可能会对生态系统的形式和功能产生持久的影响。
Oak forests dominate much of the eastern USA, but their future is uncertain due to a number of threats and widespread failure of oak regeneration. A sudden loss of oaks (Quercus spp.) could be accompanied by major changes in forest nitrogen (N) cycles with important implications for plant nutrient uptake and tree species composition. In this study, we measured the changes in N use and growth rates of black birch trees (Betula lenta L.) following oak girdling at the Black Rock Forest in southeastern New York, USA. Data were collected from nine experimental plots composed of three treatments: 100% oaks girdled (OG), 50% oaks girdled (O50) and control (C). Foliar N concentration and foliar N-15 abundance increased significantly in the oak-girdled plots relative to the control, indicating that the loss of oaks significantly altered N cycling dynamics. As mineralization and nitrification rates increase following oak loss, black birch trees increase N absorption as indicated by higher foliar N content and increased growth rates. Foliar N concentration increased by 15.5% in the O50 and 30.6% in the OG plots relative to the control, while O50 and OG plots were enriched in N-15 by 1.08 parts per thousand and 3.33 parts per thousand, respectively (P < 0.0001). A 641% increase in black birch growth rates in OG plots suggests that this species is able to respond to additional N availability and/or increased light availability. The loss of oaks and subsequent increase in black birch productivity may have a lasting impact on ecosystem form and function.