Plant respiration can acclimate to changing environmental conditions and vary between species as well as biome types, although belowground respiration responses to ongoing climate warming are not well understood. Understanding the thermal acclimation capacity of root respiration (R_root) in relation to increasing temperatures is therefore critical in elucidating a key uncertainty in plant function in response to warming. However, the degree of temperature acclimation of R_root in rainforest trees and how root chemical and morphological traits are related to acclimation is unknown. Here we investigated the extent to which respiration of fine roots (≤2 mm) of four tropical and four warm-temperate rainforest tree seedlings differed in response to warmer growth temperatures (control and +6 °C), including temperature sensitivity (Q₁₀) and the degree of acclimation of R_root. Regardless of biome type, we found no consistent pattern in the short-term temperature responses of R_root to elevated growth temperature: a significant reduction in the temperature response of R_root to +6 °C treatment was only observed for a tropical species, Cryptocarya mackinnoniana, whereas the other seven species had either some stimulation or no alteration. Across species, R_root was positively correlated with root tissue nitrogen concentration (mg g⁻¹), while Q₁₀ was positively correlated with root tissue density (g cm⁻³). Warming increased root tissue density by 20.8% but did not alter root nitrogen across species. We conclude that thermal acclimation capacity of R_root to warming is species-specific and suggest that root tissue density is a useful predictor of R_root and its thermal responses in rainforest tree seedlings.

中文翻译：

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澳大利亚雨林树苗的根部呼吸是否适应实验性变暖？

植物呼吸作用可以适应不断变化的环境条件，并且在物种和生物群落类型之间会有所不同，尽管人们对地下呼吸对持续的气候变暖的反应知之甚少。因此，了解根系呼吸（R _root）与温度升高有关的热适应能力对于阐明植物功能响应变暖的关键不确定性至关重要。但是，R_根的温度适应程度在雨林树木中，根系化学和形态性状与驯化如何相关尚不清楚。在这里，我们调查了四种热带和四种温带雨林树苗的细根呼吸作用（≤2mm）在响应较高的生长温度（控制温度和+6°C）时的差异程度，包括温度敏感性（Q ₁₀）和R_根的驯化度。不论生物群落类型如何，我们都没有发现R_根对生长温度升高的短期温度响应具有一致的模式：仅对热带物种而言，R_根对+6°C处理的温度响应显着降低，隐叶番荔枝（Cryptocarya mackinnoniana），而其他七个物种则有所刺激或没有变化。在整个物种中，R_根与根组织氮浓度（mg g ^-1）呈正相关，而Q ₁₀与根组织密度（g cm ^-3）呈正相关。变暖使根组织密度增加了20.8％，但没有改变整个物种的根氮。我们得出结论，R_根对气候变暖的热适应能力是特定于物种的，并表明根组织密度是R_根及其在雨林树苗中的热响应的有用预测指标。