Physiological Interactions Along Resource Gradients in a Tallgrass Prairie
Physiological Interactions Along Resource Gradients in a Tallgrass Prairie
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DOI：
10.2307/2937207
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发表时间：
1991-04
期刊：
影响因子：
4.8
通讯作者：
D. Schimel;T. Kittel;A. Knapp;T. Seastedt;W. Parton;V. B. Brown
中科院分区：
文献类型：
--
作者：
D. Schimel;T. Kittel;A. Knapp;T. Seastedt;W. Parton;V. B. Brown
限制光合作用的资源（水和氮）的可用性的空间变化导致大气-生物圈交换速率的变化。氮素含量和分配是冠层的特性，它与生态系统、生理和生物物理过程相联系，并在与大气-生物圈相互作用相关的空间尺度上发生变化。我们研究了这些和相关的冠层特性在堪萨斯高草草原（美国）的小尺度变化。高秆草生态系统是适合这项调查，因为在草原的初级生产力是由N的可用性。这项工作的目的是帮助解释和空间外推的气体交换测量使用空气动力学技术的FIFE（第一ISLSCP现场实验），NASA支持的研究的一部分。收集了生物量、叶面积指数（LAI）、冠层氮质量、氮浓度（N）和气体交换沿着地形和管理梯度的空间分布数据。我们还测量了高度分布的N，光截获，和气体交换的冠层内的位置在景观中的功能。生物量，叶面积指数，氮积累和氮分配发生了很大的变化，随着时间的推移，地形，并作为以前的燃烧的结果。冠层内氮素垂直梯度和光合能力与生物量和冠层光截获量在空间和时间上存在相关性。在高生物量的网站比在低生物量的网站梯度陡峭。此外，随着生物量的增加，上层的比例N分配增加（6月12%，8月32%）。随着养分吸收的高草景观内增加，生物量增加，在较低的冠层光限制诱导。随着生物量的增加，或随着死亡植被的积累，这种光限制增加，分配到上层冠层的N增加。光合能力的高度分布与冠层内氮素分配和光截获有关。由于景观中的资源比例（光、水和氮）不同，气体交换速率也不同。这项工作表明，消光，N分配，光合作用之间的相互作用，已提出的单种立场适用于多物种，但结构简单，冠层的高草草原。基于进化论的植物性能模型可以为从地点到景观和更大区域的大气-生态系统交换率的空间外推提供强有力的基础。
Spatial variability in availability of resources that limit photosynthesis (water and N) leads to variation in rates of atmosphere-biosphere exchange. N content and allocation are canopy properties that link ecosystem, physiological, and biophysical pro- cesses and that vary in space at scales relevant to atmosphere-biosphere interaction. We studied landscape-scale variation in these and related canopy properties in Kansas Tallgrass Prairie (USA). The tallgrass ecosystem was suited to this investigation because primary production in the prairie is constrained by N availability. This work was designed to aid in interpretation and spatial extrapolation of gas exchange measurements made using aerodynamic techniques as part of FIFE (First ISLSCP Field Experiment), a NASA-sup- ported study. We collected data on spatial distribution of biomass, leaf area index (LAI), canopy N mass, N concentration ((N)), and gas exchange along topographic and manage- ment gradients. We also measured height distribution of N, light interception, and gas exchange within canopies as a function of position in the landscape. Substantial variation in biomass, LAI, N accumulation, and N allocation occurred over time, with topography, and as a result of previous burning. The vertical gradient of (N) and photosynthetic capacity within canopies were correlated, in space and time, with biomass and canopy light inter- ception. The gradients were steeper in high biomass sites than in low biomass sites. In addition, proportional N allocation to the upper layer increased with time (12% in June, 32% in August) as biomass increased. As nutrient uptake increased within the tallgrass landscape, biomass increased and light limitation in the lower canopy was induced. As this light limitation increased with increasing biomass, or with accumulation of dead vegetation, allocation of N to the upper canopy increased. Height distribution of photosynthetic ca- pacity paralleled within-canopy N allocation and light interception. As resource ratios (light, water, and nitrogen) varied in the landscape, so did rates of gas exchange. This work suggests that interactions between light extinction, N allocation, and photosynthesis that have been proposed for monospecific stands apply to the multispecies, but structurally simple, canopy of the tallgrass prairie. Models of plant performance based on evolutionary arguments may provide a powerful basis for spatial extrapolation of atmosphere-ecosystem exchange rates from sites to landscapes and larger regions.