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Effects of carbon and nitrogen interactions on terrestrial ecosystems

碳氮相互作用对陆地生态系统的影响

基本信息

批准号：
09640745
负责人：
TATENO Masaki
金额：
$ 2.3万
依托单位：
University of Tokyo (1998-2001)Gunma University (1997)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 2000
项目状态：
已结题

项目摘要

We developed a growth model of plants and a ecosystem model with special reference to carbon and nitrogen interactions. Then we tried to test the predictions of the models.1. Optimal matter partitioning of plants depends on soul fertility, plant shape, and life history. Leaf nitrogen contents (i.e. photosynthetic capacity) predicted by the model are similar to those measured in the fields.2. Nitrogen-fixing alder does not resorb nitrogen form senescing leaves in autumn. As a result, the alder has growth period extension in autumn. The amount of energy assimilated by the alder in the extended growth period was about six times that required for compensating the nitrogen loss. This surplus energy balance provides an advantage over the non-nitrogen-resorbing trait of nitrogen-fixing deciduous trees.3. Our nitrogen competition model predicted that natural vegetation in the cool temperate zone must be mixed forest of deciduous trees and evergreen conifers. However, deciduous forests without the conifers are widely distributed in the zone. We measured the elongation growth of understory conifers in the deciduous forests. We showed that the saplings of conifers attain the forest canopy of the deciduous forests within 100 years from their germination. This support the model prediction. Probably, the deciduous forests in the cool temperate zone are secondary forests caused by continual fellings. About 40 year ago, Japanese people changed their energy source from trees to petroleum. Accordingly, the secondary deciduous forests are returning to natural mixed forest.

我们开发了植物生长模型和生态系统模型，特别参考了碳和氮的相互作用。然后我们试着测试模型的预测。植物的最佳物质分配取决于灵魂肥力、植物形状和生活史。模型预测的叶片含氮量(即光合作用能力)与田间实测值基本一致。秋天，固定氮素的赤杨不会从衰老的树叶中吸收氮素。因此，赤杨的生长期在秋季有所延长。在延长的生长期内，杉木吸收的能量大约是补偿氮素损失所需的6倍。这种过剩的能量平衡提供了比固氮落叶树的非氮素吸收特性更好的优势。我们的氮竞争模型预测，寒温带的自然植被一定是落叶乔木和常绿针叶混交林。然而，没有针叶林的落叶林在该地区分布广泛。我们测量了落叶林中林下针叶的伸长生长。我们发现，针叶树苗在萌发后100年内达到落叶林的林冠。这支持了模型的预测。寒温带落叶林可能是连续采伐形成的次生林。大约40年前，日本人将能源从树木改为石油。相应地，次生落叶林正在回归天然混交林。