Limitations to winter and spring photosynthesis of a Rocky Mountain subalpine forest
Limitations to winter and spring photosynthesis of a Rocky Mountain subalpine forest
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DOI：
10.1016/j.agrformet.2018.01.025
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发表时间：
2018-04-15
影响因子：
6.2
通讯作者：
Eiriksson, David P.
中科院分区：
文献类型：
--
作者：
Bowling, David R.;Logan, Barry A.;Eiriksson, David P.
温带和北方针叶林在寒冷的季节会休眠好几个月。气候变化正在改变冬季环境，气温升高，降水量改变，许多地方的融雪提前。如果足够显著，这些变化可能会改变常绿植物的休眠和活动模式。在这里，我们研究了限制光合活性的高海拔亚高山森林，近几十年来经历了大幅变暖的因素。我们测试了这样一个假设，即这种变暖已经足够显著，可以在冬季阳光明媚的温暖日子进行光合作用。利用热成像，我们发现，在冬季的树叶有时接近光合作用的最佳温度，但没有净碳增益发生的大部分寒冷的季节。水分运输是有限的堵塞树液运输冻结树干，但不是由冻土。叶类胡萝卜素含量在冬季高得多，主要是由增加池的光保护叶黄素循环的大小。叶绿素和叶黄素含量没有季节性变化。净碳吸收开始只有树干解冻，树种之间的时间没有差异，春季增加冠层光合能力发生在汁液运输检测。所有物种的毛初级生产力（GPP）的季节性与叶黄素循环脱环氧化状态的季节性密切相关。GPP的季节性可通过两种冠层颜色指标--绿色色度坐标和绿红植被指数（新提出的基于MODIS的叶绿素/类胡萝卜素指数或CCI的代理）来检测。两项指标均与GPP显著相关。总之，这些结果表明，潜在的空气或近地表遥感叶色作为衡量在万年青森林的光合作用活性，并监测与冬季休眠的进展和出相关的生理变化。
Temperate and boreal conifer forests are dormant for many months during the cold season. Climate change is altering the winter environment, with increased temperature, altered precipitation, and earlier snowmelt in many locations. If significant enough, these changes may alter patterns of dormancy and activity of evergreens. Here we studied the factors limiting photosynthetic activity of a high-elevation subalpine forest that has undergone substantial warming in recent decades. We tested the hypothesis that this warming has been significant enough to allow photosynthesis during sunny warm days in winter. Using thermal imagery, we found that foliage in winter was sometimes near the temperature optimum for photosynthesis, but no net carbon gain occurred for most of the cold season. Water transport was limited by blockage of sap transport by frozen boles, but not by frozen soils. Foliar carotenoid content was much higher during winter, driven largely by increases in the pool size of the photoprotective xanthophyll cycle. There was no seasonal change in chlorophyll or lutein content. Net carbon uptake began only as boles thawed, with no difference in timing among tree species, and the spring increase in canopy-level photosynthetic capacity occurred before sap transport was detected. The seasonality of gross primary productivity (GPP) was strongly linked to seasonality of xanthophyll cycle deepoxidation state in all species. Seasonality of GPP was detectable with two metrics of canopy color - the Green Chromatic Coordinate and Green-Red Vegetation Index (a proxy for the newly proposed MODIS-based chlorophyll/carotenoid index or CCI). Both indices were significantly correlated with GPP. Together these results indicate the potential for airborne or near-surface remote sensing of leaf color to serve as a metric of photosynthetic activity in evergreen forests, and to monitor physiological changes associated with the progression in and out of winter dormancy.