树干/枝呼吸作用对环境变化的响应

Responses of stem/branch respiration to environmental change:A review

树干/枝呼吸是调控森林碳平衡的关键生理过程之一,其对环境变化的响应在很大程度上决定了森林生产力及其固碳增汇能力。本文主要综述了近10年来林木树干/枝呼吸对大气CO2浓度升高、温度升高、干旱胁迫和人为管理的响应及其生理生态学调控机制,结果表明:大气CO2浓度升高和升温一般促进树干/枝的呼吸,其表观温度敏感性(Q10值)受树种、测定方法、温度范围、季节、林龄和径阶的影响,但变幅小于根系呼吸Q10值的变幅;干旱胁迫时,树干/枝呼吸速率减缓,随后进行浇水则会引发树干/枝呼吸的剧增,其生理学机制仍不清楚;不同的管理措施(如火烧、施肥、灌溉、修枝、环割等)对树干/枝呼吸的影响不尽相同。综述以往研究,提出今后值得深入探讨的4个方向:(1)明确树干/枝呼吸释放CO2的来源和去向以及建立相应的测定标准;(2)了解树干/枝呼吸对环境变化响应的生物学机制;(3)探讨树干/枝呼吸对环境变化的适应性;(4)树干液流、同位素示踪和CO2微电极技术的综合应用。

Stem/branch respiration contributes about 8% of the total ecosystem respiration,being one of the most important components of forest carbon budget.In recent 10 years studies,specific respiration chamber with complex system was applied to measure the stem/branch respiration.However,it＇s still difficult to precisely estimate the stem/branch respiration at cell,tissue,individual,and stand scales.It is becoming a major trend to estimate the CO2 flux from the internal and external stem/branch,using the combination of CO2 microelectrode technology and infrared gas analyzer（IRGA） method.Generally,the stem/branch respiration rate increases with elevated atmospheric CO2 concentration and temperature,but it＇s still unclear whether the stem/branch respiration acclimates to the elevated CO2 concentration and temperature.The Q10 value of stem/branch respiration,ranged from 1.0 to 4.3,could be affected by measurement method,season,tree age,and stem diameter.In addition,the stem/branch respiration rate decreased with increasing drought stress,and increased abruptly with the following rewetting process.The management practices,including fire,fertilization,irrigation,pruning,and girdling,could also affect the stem/branch respiration rate.Therefore,four research priorities were proposed,i.e.,1） sources and fate of the CO2 release from stem/branch respiration and its measurement standard,2） biological mechanisms of the responses of stem/branch respiration to environmental change,3） acclimation of stem/branch respiration to environmental changes,and 4） integrated application of stem sap flow measurement,isotopic tracing,and CO2 microelectrode technology in measuring stem/branch respiration.