短期夜间增温对亚高山针叶林云杉幼苗根系分泌物速率和化学成分的影响

Effects of night-time warming on the rates and main chemical components of root exudates produced by Picea asperata seedlings in subalpine coniferous forests

以连续7a红外辐射增温处理下的云杉幼苗为对象,定量分析了增温对植物根系碳(C)、氮(N)分泌速率以及主要挥发性化学成分的影响。结果表明:(1)增温显著增加了云杉幼苗根系C分泌速率,而对N分泌速率无显著影响,并伴随着根系分泌物C∶N化学计量比显著增加;(2)不同化学组分输入含量变化对增温的响应具有明显差异,其响应幅度和方向与化学组分种类有关。其中糖类、氨基酸和酚类化合物的含量在增温处理下均显著增加,而酯类、醚类相对含量显著降低;(3)进一步分析表明,同组分中不同化合物成分含量对增温的响应也有所差异。例如,增温仅导致酚类化合物中2,6-二叔丁基-4-甲基苯酚和4-叔丁基杯[4]芳烃含量显著增加(分别比对照增加了88.9%和375.7%),而对其余酚类化合物成分含量无显著影响。结果表明增温可导致植物根系分泌物各组分相对含量发生深刻地变化,这对于进一步认识不同环境变化下根系分泌物输入及其所诱导的特异性土壤微生物养分过程具有重要的理论意义。

While it is well recognized that root exudates play a crucial role in driving belowground biogeochemical processes,few studies have attempted to examine the effects of elevated temperature on the rates and chemical components of root exudation in forests. In this study,we conducted a night-time warming experiment by using an infrared heating device to explore the ecological consequences of warming on the rates and chemical components of root exudation by Picea asperataseedlings. Root exudates were collected from intact fine roots of plants growing in the warmed plots and the control plots using a modified culture-based cuvette system,developed especially for collecting field-based exudates. The concentrations of total organic carbon（ TOC） and total nitrogen（ TN） in the root exudates were quantitatively investigated,and expressed as the C and N exudation rates for P. asperata seedlings. Furthermore,the main chemical components of root exudates were quantified using the gas chromatography and mass spectrometry（ GC-MS） method. The results showed the following：（ 1） Experimental warming considerably increased the root C exudation rates（ μg C g-1 root biomass h-1）. In contrast,no significant effects were observed on the root N exudation rates（ μg N g-1 root biomass h-1）,which led to a significant increase in the C ∶ N ratio of the root exudates.（ 2） Experimental warming had significant effects on the relative contents of chemical compounds,and the response magnitude and direction to experimental warming were closely related to the components of the chemical compounds. Specifically,the relative contents of sugars,amino acids,and phenolics were significantly increased by warming,while the relative contents of esters and ethers markedly decreased.（ 3） Experimental warming had significant effects on the contents of different chemical components in root exudates. For example,the relative contents of two phenolics,2,6-Di-tert-butyl-4-methylphenol and 4-Tert-butylcalix [4] arene,increased by 88. 9% and 375.7%,respectively,compared to the control plots,but no significant differences were observed for the other components.Collectively,our results suggested that experimental warming can lead to profound influences on the exudation rates and the relative contents of the specific exudate components,which provides a theoretical foundation that can improve understanding of the soil C-nutrient cycling process mediated by root exudation inputs in subalpine coniferous forests when P. asperata is subjected to environmental changes.