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Response of plant communities to elevated CO_2

植物群落对 CO_2 升高的反应

基本信息

批准号：
07044176
负责人：
HIROSE Tadaki
金额：
$ 1.6万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1995
资助国家：
日本
起止时间：
1995 至无数据
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07044176/
关键词：
Abutilon theophrashi Ambrosia artemisiifolia Canopy photosynthesis CO_2 elevation Leaf area index Nitrogen use efficiency Plant community Stand structure

项目摘要

Elevated CO_2 may increase dry mass production of canopies directly through increasing net assimilation rate of leaves and also indirectly through increasing leaf area index (LAI). We studied the effects of CO_2 elevation on canopy productivity and development in mono-specific and mixed(1 : 1) stands of two co-occurring C_3 annual species, Abutilon theophrasti and Ambrosia artemisiifolia. The stands were established in the glasshouse with two CO_2 levels (360 and 700ml/l)under natural light conditions. The planting density was 100 per m2 and LAI increased up to 2.6 in 53-day growth. Root competition was excluded growing each plant in an individual pot. However, interference was apparent in the amount of photons absorbed by the plants and in photon absorption per unit leaf area. Greater photon absorption by Abutilon in the mixed stand was due to different canopy structures : Abutilon distributed leaves in the upper layrs in the canopy while Ambrosia distributed leaves more to the lower layrs. CO_2 elevation did not affect the relative performance and light interception of the two species in mixed stands. Total aboveground dry mass was significantly increased with CO_2 elevation, while no significant effects on leaf area development were observed. CO_2 elevation increased dry mass production by 30-50%, which was mediated by 35-38% increase in the net assimilation rate (NAR) and 37-60% increase in the nitrogen use efficiency (NUE,=net assimilation rate per unit leaf nitrogen). Since there was a strong overall correlation between LAI and aboveground nitrogen and no significant difference was found in the regression of LAI against aboveground nitrogen between the two CO_2 levels, we hypothesized that leaf area development was controlled by the amount of nitrogen taken up from the soil. This hypothesis suggests that the increased LAI with CO_2 elevation observed by several authors might be due to increased uptake of nitrogen with increased root growth.

升高的CO_2可以通过增加叶片的净同化率直接增加冠层的干产量，也可以通过增加叶面积指数间接增加冠层的干产量。本文研究了CO_2升高对两种C_3共生植物锦鸡（Abutilon theophrasti）和蒿（Ambrosia artemisiifolia）单株林分和混合林分（1:1）林分生产力和生长发育的影响。在自然光照条件下，在co2浓度为360和700ml/l的温室中建立林分。种植密度为100 / m2，生长53 d LAI增加至2.6。在单个盆栽中种植的每株植物不存在根系竞争。然而，植物吸收的光子量和单位叶面积的光子吸收受到明显干扰。Abutilon对混合林分的光子吸收更大是由于冠层结构不同，Abutilon在冠层上层分布叶片，而Ambrosia则在冠层下层分布叶片。CO_2升高对混交林中两种树种的相对生长性能和截光量没有影响。地上总干质量随CO_2升高而显著增加，但对叶面积发育无显著影响。CO_2升高可使干物质产量提高30-50%，其机制是净同化率（NAR）提高35-38%，氮利用效率（NUE）提高37-60%。由于叶面积指数与地上氮的整体相关性较强，且叶面积指数与地上氮的回归在两个CO_2水平间无显著差异，因此我们假设叶面积的发育受土壤吸氮量的控制。这一假设表明，几位作者观察到的随CO_2升高而增加的LAI可能是由于根系生长增加而增加的氮吸收。