Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.
Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China.
Glob Chang Biol. 2019 Sep;25(9):3056-3069. doi: 10.1111/gcb.14674. Epub 2019 May 28.
Long-term trends in ecosystem resource use efficiencies (RUEs) and their controlling factors are key pieces of information for understanding how an ecosystem responds to climate change. We used continuous eddy covariance and microclimate data over the period 1999-2017 from a 120-year-old black spruce stand in central Saskatchewan, Canada, to assess interannual variability, long-term trends, and key controlling factors of gross ecosystem production (GEP) and the RUEs of carbon (CUE = net primary production [NPP]/GEP), light (LUE = GEP/absorbed photosynthetic radiation [APAR]), and water (WUE = GEP/evapotranspiration [E]). At this site, annual GEP has shown an increasing trend over the 19 years (p < 0.01), which may be attributed to rising atmospheric CO concentration. Interannual variability in GEP, aside from its increasing trend, was most strongly related to spring temperatures. Associated with the significant increase in annual GEP were relatively small changes in NPP, APAR, and E, so that annual CUE showed a decreasing trend and annual LUE and WUE showed increasing trends over the 19 years. The long-term trends in the RUEs were related to the increasing CO concentration. Further analysis of detrended RUEs showed that their interannual variation was impacted most strongly by air temperature. Two-factor linear models combining CO concentration and air temperature performed well (R ~0.60) in simulating annual RUEs. LUE and WUE were positively correlated both annually and seasonally, while LUE and CUE were mostly negatively correlated. Our results showed divergent long-term trends among CUE, LUE, and WUE and highlighted the need to account for the combined effects of climatic controls and the 'CO fertilization effect' on long-term variations in RUEs. Since most RUE-based models rely primarily on one resource limitation, the observed patterns of relative change among the three RUEs may have important implications for RUE-based modeling of C fluxes.
长期以来，生态系统资源利用效率（RUE）及其控制因素的趋势一直是理解生态系统如何应对气候变化的关键信息。我们利用加拿大萨斯喀彻温省中部一个 120 年历史的黑云杉林在 1999-2017 年期间的连续涡度协方差和小气候数据，评估了总生态系统生产力（GEP）和碳（CUE=净初级生产力[NPP]/GEP）、光（LUE=GEP/吸收光合辐射[APAR]）和水（WUE=GEP/蒸散[E]）的 RUE 的年际变异性、长期趋势和关键控制因素。在这个地点，19 年来，年 GEP 呈上升趋势（p<0.01），这可能归因于大气 CO 浓度的上升。除了上升趋势外，GEP 的年际变化与春季温度的关系最为密切。与年 GEP 的显著增加相对应的是，NPP、APAR 和 E 的变化相对较小，因此，年 CUE 呈下降趋势，而年 LUE 和 WUE 呈上升趋势在 19 年。RUE 的长期趋势与 CO 浓度的增加有关。对去趋势 RUE 的进一步分析表明，它们的年际变化受空气温度的影响最大。结合 CO 浓度和空气温度的双因素线性模型在模拟年 RUE 方面表现良好（R~0.60）。LUE 和 WUE 无论是在年度还是季节性都呈正相关，而 LUE 和 CUE 大多呈负相关。我们的结果表明，CUE、LUE 和 WUE 之间存在不同的长期趋势，并强调需要考虑气候控制和“CO 施肥效应”对 RUE 长期变化的综合影响。由于大多数基于 RUE 的模型主要依赖于一种资源限制，因此这三种 RUE 之间相对变化的观察模式可能对基于 RUE 的 C 通量模型具有重要意义。
