Yang Yan, Halbritter Aud H, Klanderud Kari, Telford Richard J, Wang Genxu, Vandvik Vigdis
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, China.
Department of Biological Sciences, University of Bergen, Bergen, Norway.
Front Plant Sci. 2018 Nov 2;9:1574. doi: 10.3389/fpls.2018.01574. eCollection 2018.
Long-term monitoring, space-for-time substitutions along gradients, and temperature manipulations are common approaches to understand effects of climate change on alpine and arctic plant communities. Although general patterns emerge from studies using different approaches, there are also some inconsistencies. To provide better estimates of plant community responses to future warming across a range of environments, there have been repeated calls for integrating different approaches within single studies. Thus, to examine how different methods in climate change effect studies may ask different questions, we combined three climate warming approaches in a single study in the Hengduan Mountains of southwestern China. We monitored plant communities along an elevation gradient using the space-for-time approach, and conducted warming experiments using open top chambers (OTCs) and plant community transplantation toward warmer climates along the same gradient. Plant species richness and abundances were monitored over 5 years addressing two questions: (1) how do plant communities respond to the different climate warming approaches? (2) how can the combined approaches improve predictions of plant community responses to climate change? The general trend across all three approaches was decreased species richness with climate warming at low elevations. This suggests increased competition from immigrating lowland species, and/or from the species already growing inside the plots, as indicated by increased biomass, vegetation height or proportion of graminoids. At the coldest sites, species richness decreased in OTCs and along the gradient, but increased in the transplants, suggesting that plant communities in colder climates are more open to invasion from lowland species, with slow species loss. This was only detected in the transplants, showing that different approaches, may yield different results. Whereas OTCs may constrain immigration of new species, transplanted communities are rapidly exposed to new neighbors that can easily colonize the small plots. Thus, different approaches ask slightly different questions, in particular regarding indirect climate change effects, such as biotic interactions. To better understand both direct and indirect effects of climate change on plant communities, we need to combine approaches in future studies, and if novel interactions are of particular interest, transplants may be a better approach than OTCs.
长期监测、沿梯度进行空间换时间替代以及温度操控是了解气候变化对高山和北极植物群落影响的常用方法。尽管使用不同方法的研究呈现出一些总体模式，但也存在一些不一致之处。为了更准确地估计植物群落在一系列环境中对未来变暖的响应，人们多次呼吁在单个研究中整合不同方法。因此，为了研究气候变化影响研究中的不同方法可能如何提出不同问题，我们在中国西南部横断山脉的一项单一研究中结合了三种气候变暖方法。我们使用空间换时间方法沿着海拔梯度监测植物群落，并使用开顶式生长室（OTC）和沿着相同梯度向温暖气候区进行植物群落移植的方式开展变暖实验。对植物物种丰富度和丰度进行了为期5年的监测，以解决两个问题：（1）植物群落如何响应不同的气候变暖方法？（2）综合方法如何改进对植物群落对气候变化响应的预测？所有三种方法的总体趋势是，低海拔地区随着气候变暖物种丰富度下降。这表明来自迁入的低地物种和/或已经在样地内生长的物种的竞争加剧，生物量增加、植被高度增加或禾本科植物比例增加表明了这一点。在最冷的地点，OTC处理区域和沿着梯度方向物种丰富度下降，但移植区域物种丰富度增加，这表明气候较冷地区的植物群落更容易受到低地物种的入侵，物种损失缓慢。这仅在移植区域中检测到，表明不同方法可能产生不同结果（OTC可能会限制新物种的迁入，而移植群落会迅速接触到能够轻松定殖于小样地的新邻居）。因此，不同方法提出的问题略有不同，特别是在涉及间接气候变化影响（如生物相互作用）方面。为了更好地理解气候变化对植物群落的直接和间接影响，我们需要在未来的研究中结合多种方法，如果对新的相互作用特别感兴趣，移植可能是比OTC更好的方法。
