Journal of Plant Ecology ›› 2023, Vol. 16 ›› Issue (3): 0-rtac106.DOI: 10.1093/jpe/rtac106

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  • 收稿日期:2022-02-16 修回日期:2022-06-12 接受日期:2022-11-25 出版日期:2023-06-01 发布日期:2022-12-15

Asian tropical forests assimilating carbon under dry conditions: water stress or light benefits?

Lian-Yan Yang1,8, Rui Yu1, Jin Wu2, Yongjiang Zhang3, Yoshiko Kosugi4, Natalia Restrepo-Coupe5, Afredo Huete5, Jie Zhang1, Yu-Hai Liu1, Xiang Zhang1, Wen-Jie Liu1, Jun-Fu Zhao1, Jiye Zeng6, Qing-Hai Song7, Ya-Jun Chen7, Liang Song7, Zheng-Hong Tan8,*   

  1. 1Ecology Program, Department of Ecology, School of Ecology and Environmental Science, Hainan University, Haikou 570228, China;
    2School of Biological Sciences, Faculty of Science, The University of Hong Kong, Pokfulam, Hong Kong, China;
    3School of Biology and Ecology, The University of Maine, Orono, ME 04469, USA;
    4Forest Hydrology Lab, Graduate School of Agriculture, Kyoto University, Kyoto, Japan;
    5School of Life Sciences, University of Technology Sydney, New South Wales, Australia;
    6National Institute for Environmental Studies, Tsukuba, Japan;
    7Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Yunan 666303, China;
    8School of Ecology and Environmental Studies, Yunnan University, Kunming 650091, China
  • Received:2022-02-16 Revised:2022-06-12 Accepted:2022-11-25 Online:2023-06-01 Published:2022-12-15
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摘要: 热带森林因其生物量巨大、结构复杂和生物多样而著称。然而,关于这些森林光合作用的季节动态及其少水期间的生态适应仍知之甚少。本文利用中南半岛上跨20个纬度(2°-22° N)的自然梯度带,探讨了季节性水分条件变化对中南半岛热带森林光合作用季节动态的影响及其机理。研究结果表明,对于气候季节性明显的热带森林,不论其为常绿、落叶还是半落叶,其雨季的森林冠层光合作用(或称总初级生产总值,GPP)明显高于旱季。缺乏气候季节性的常湿热带雨林,GPP呈现“双峰”季节格局;而且,这种季节格局与太阳辐射之间有较好的对应关系。旱季或者是短干旱期内,冠层导度(Gs)有明显下降,显示出水分对气孔开度的抑制作用。然而,这种气孔开度的降低,并未导致近赤道的常湿低地雨林GPP的下降。也就是说,常湿低地雨林GPP在季节尺度上,表现为光限制而非水分限制。气候季节性明显的3个站点,不论Gs还是GPP在旱季明显低于雨季,则表现出明显的水分限制。

关键词: 涡度相关法, 叶面积指数, 适应对策, 生态系统生理, 总初级生产力, 潜热通量, 水分利用效率

Abstract: Tropical forests are characterized by vast biomass, complex structures and mega-biodiversity. However, the adaptation processes of these forests to seasonal water availability are less understood, especially those located in the monsoonal and mountainous regions of tropical Southeast Asia. This study used four representative tropical forests spanning from 2° N to 22° N in continental Southeast Asia to address dry-condition photosynthesis at the seasonal scale. We first provided novel and reliable estimations of ecosystem photosynthesis (gross primary production; GPP) seasonality at all four sites. As expected, both evergreen and deciduous seasonal forests exhibited higher GPPs during the rainy season than during the dry season. A bimodal pattern corresponding to solar radiation occurred in the GPP of the perhumid forest. The surface conductance (Gs) was consistently lower both in the dry season and during dry spells (DSPs) than during the wet season and non-dry spells. However, this did not prevent GPP from increasing alongside increasing irradiance in the perhumid forest, suggesting that other ecosystem physiological properties, for example, the light-saturated photosynthetic rate, must have increased, thus surpassing the effect of Gs reduction. Thus, perhumid forests could be defined as light-demanding ecosystems with regard to their seasonal dynamics. Seasonal forests are water-stressed ecosystems in the dry season, as shown by the reductions in GPP, Gs and related ecosystem physiological properties. At all four forest sites, we observed a lack of consistent adaptive strategy to fit the water seasonality due to the diversity in leaf phenology, soil nutrient availability, root depth and other potential factors.

Key words: Eddy covariance, leaf area index, adaptive strategy, ecosystem physiology, gross primary production, latent heat flux, water use efficiency