Data from: Herbivory prevents positive responses of lowland plants to warmer and more fertile conditions at high altitudes

1. Warm-adapted low-elevation plants are expected to exhibit considerable range shifts to higher altitudes and latitudes as a result of climate warming and increased nutrient loads. However, empirical studies show that the magnitude and direction of plant responses are highly species- and site-specific, suggesting that several additional drivers interact with warmer climate. 2. We experimentally tested the interactive effects of climate warming, herbivory and soil fertility on low elevation plants. Seedlings of three warm-adapted lowland forbs (Epilobium angustifolium, Silene dioica and Solidago virgaurea) were transplanted to an open tundra site with native mountain tundra vegetation, and the effects of full-factorial combinations of herbivore exclosures, warming and fertilization on transplant survival, growth and flowering were studied for two growing seasons. We also investigated the response of native vegetation biomass to the same treatments, and compared it to the responses of transplanted lowland forbs. 3. Effects of both warming and fertilization on the transplanted lowland forbs strongly hinged on herbivore exclusion, resulting in ca 10 fold increase of biomass in warmed and fertilized plots without herbivores. While warm-adapted transplants benefited from warming, the native tundra plant community biomass did not respond to warming treatment. 4. Our results show that grazing limits the growth of transplants under warmer and more productive conditions, indicating that the expansion of lowland plant species to higher altitudes with warming may be hampered by mammalian herbivory. Furthermore, our results also suggest that migration of warm-adapted species into lightly-grazed high altitude tundra ecosystems might transform these communities to be more responsive to warmer climate and nutrient loads. Studies that do not consider species’ upward shifts from lower altitudes might thus have underestimated vegetation responses to global warming, as well as the potential of herbivory to influence these responses.

1. 受气候变暖与养分负荷增加的影响，适应温暖环境的低海拔植物预计会发生显著的分布范围迁移，向更高海拔与纬度区域扩张。但现有实证研究表明，植物响应的强度与方向具有极强的物种特异性与生境特异性，这意味着存在多种额外驱动因子与变暖气候产生交互作用。
2. 本研究通过实验探究了气候变暖、植食作用与土壤肥力对低海拔植物的交互影响。我们将3种适应温暖环境的低地杂类草（Epilobium angustifolium、Silene dioica及Solidago virgaurea）的幼苗移栽至原生山地苔原植被覆盖的开阔苔原生境，并设置植食动物排除、增温与施肥的全因子组合处理，在两个生长季内监测了移栽植株的存活、生长与开花情况。此外，本研究还探究了原生植被生物量对上述处理的响应，并将其与移栽低地杂类草的响应进行了对比。
3. 增温与施肥对移栽低地杂类草的影响均强烈依赖于植食动物排除处理：在无植食动物的增温施肥样地中，植株生物量提升了约10倍。尽管适应温暖环境的移栽植株可从增温处理中获益，但原生苔原植物群落的生物量并未对增温产生响应。
4. 本研究结果表明，在变暖且养分更充足的生境中，草食作用会抑制移栽植株的生长，这意味着气候变暖背景下低地植物向高海拔区域的扩张可能会受到哺乳动物植食作用的阻碍。此外，研究结果还提示，适应温暖环境的物种向轻度草食化的高海拔苔原生态系统的迁移，可能会使这些群落对气候变暖和养分负荷的响应更为敏感。若未考虑物种从低海拔向高海拔的迁移过程，相关研究可能会低估植被对全球变暖的响应强度，以及植食作用对这类响应的调控潜力。