温带4种针叶树种春、秋季节树干维持呼吸的日动态

Diurnal dynamics in stem maintenance respiration in spring and autumn for four temperate coniferous tree species in northeastern China

揭示树干维持呼吸(RM)的时间变化特征及其调控因子有助于理解树木碳代谢过程及其对环境变化的响应和构建森林碳循环机理模型。采用红外气体分析法原位测定东北东部山区4个针叶树种(红松、红皮云杉、樟子松和兴安落叶松)的春、秋季节RM日动态及其影响因子。结果表明:秋季和春季4个树种RM日变化多随树干温度(TW)而变化,但RM峰值大小和出现时间以及日变化幅度因树种和季节而异。TW解释了RM(除春季樟子松外)变异性的50%以上,但RM对TW响应滞后1.5 h(春季樟子松为3 h)。将RM标准化到TW为10℃(R10)时发现,秋季R10波动在0.54μmol CO2m-2s-1(兴安落叶松)—0.78μmol CO2m-2s-1(红皮云杉)之间,而春季R10则波动在0.87μmol CO2m-2s-1(红松)—1.10μmol CO2m-2s-1(樟子松)之间,前者平均低于后者约40%。然而,各树种秋季和春季RM的Q10值差异不显著(P>0.05),波动在1.52(樟子松)—1.82(红皮云杉)之间。秋季和春季所有树种的R10与树木胸径(DBH)之间均呈显著的正相关关系(P<0.05),而Q10与DBH则多呈负相关关系(P<0.05),表明DBH可作为估测这些针叶树种RM的参数之一。

Exploring diurnal variations and controlling factors of stem maintenance respiration （RM ） is important for understanding tree carbon metabolism and its response to environmental changes and developing forest carbon cycling models. In this study, we used an infrared gas analyzer （LI-6400 IRGA） to in situ measure the diurnal dynamics in RM for four temperate coniferous tree species in northeastern China. The tree species included three evergreen （ i.e., Korean pine （Pinus koraiensis） , Korean spruce （Picea koraiensis） , and Mongolian pine （Pinus sylvestris var. mongolica）） and one deciduous （ Dahurian larch （Larix gmelinii） ） species. Twelve replicate trees with various diameters at breast height （DBH） were randomly sampled for each tree species. The RM for each sampled tree was measured every 1.5 h around the clock before the growth started in spring （late April-early May） and after the growth ceased in autumn （October-November）. A polyvinyl chloride （PVC） collar was installed at breast height of the stem on the northern direction of each sampled tree for measuring the RM. Stem temperature at the 1 cm depth beneath the bark （ Tw） was simultaneously measured 3 cm above the collar with a digital thermometer. The results showed that the diurnal variation in RM largely followed the change in Tw for all the tree species in both autumn and spring with a ＂unimodal＂ or ＂bimodal＂ pattern, but the daily maximum value, occurring time and amplitude of RM varied with tree species and seasons. Tw explained more than 50% variations in RM for the species except for Mongolian pine in spring, which suggested that Tw be a key environmental factor regulating the RM. However, RM lagged behind Tw by 1.5 h （3 h for Mongolian pine in spring）. Normalized RMat 10 ℃ （R10） was significantly lower in autumn than that in spring for each species, ranging from 0.54 μmol CO2 m^-2 s^-1 for Dahurian larch to 0.78 Ixmol CO2 m-2 s^-1 for Korean spruce in autumn and from 0.87 μmol CO2 m^-2 s^-1 for Korean pine to 1.10 μmol CO2 m^-2 s^-1for Mongolian pine in spring, respectively. The mean R10 was about 40% lower in autumn than in spring. There was no significant difference in Q10 value of RM between autumn and spring for each species （P 〉 0.05）, ranging between 1.52 for Mongolian pine and 1.82 for Korean spruce. The R10 was significantly positively correlated with DBH for all the species in both seasons, while the Q10 was negatively with DBH （all P 〈 0.05）. This suggested that DBH can be used as a proxy for predicting the RM for these temperate tree species.