Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia.
Centre for Environmental Risk Management of Bushfires, University of Wollongong, Wollongong, NSW, Australia.
Glob Chang Biol. 2018 Jun;24(6):2366-2376. doi: 10.1111/gcb.14038. Epub 2018 Feb 14.
Rising atmospheric [CO ] and associated climate change are expected to modify primary productivity across a range of ecosystems globally. Increasing aridity is predicted to reduce grassland productivity, although rising [CO ] and associated increases in plant water use efficiency may partially offset the effect of drying on growth. Difficulties arise in predicting the direction and magnitude of future changes in ecosystem productivity, due to limited field experimentation investigating climate and CO interactions. We use repeat near-surface digital photography to quantify the effects of water availability and experimentally manipulated elevated [CO ] (eCO ) on understorey live foliage cover and biomass over three growing seasons in a temperate grassy woodland in south-eastern Australia. We hypothesised that (i) understorey herbaceous productivity is dependent upon soil water availability, and (ii) that eCO will increase productivity, with greatest stimulation occurring under conditions of low water availability. Soil volumetric water content (VWC) determined foliage cover and growth rates over the length of the growing season (August to March), with low VWC (<0.1 m m ) reducing productivity. However, eCO did not increase herbaceous cover and biomass over the duration of the experiment, or mitigate the effects of low water availability on understorey growth rates and cover. Our findings suggest that projected increases in aridity in temperate woodlands are likely to lead to reduced understorey productivity, with little scope for eCO to offset these changes.
大气中[CO2]的增加以及相关的气候变化预计将在全球范围内改变一系列生态系统的初级生产力。预计干旱的增加将降低草原生产力，但[CO2]的增加和植物水分利用效率的提高可能会部分抵消干旱对生长的影响。由于对调查气候和 CO 相互作用的现场实验有限，因此在预测未来生态系统生产力变化的方向和幅度方面存在困难。我们使用重复的近地表数字摄影来量化水分供应和实验性升高[CO2]（eCO2）对澳大利亚东南部温带草地林地下层活叶盖度和生物量的影响在三个生长季节。我们假设（i）林下草本生产力取决于土壤水分供应，以及（ii）eCO2 将增加生产力，在低水分供应条件下刺激作用最大。土壤体积含水量（VWC）确定了整个生长季节（8 月至 3 月）的叶盖度和生长速度，低 VWC（<0.1 m m）降低了生产力。然而，在实验期间，eCO2 并没有增加草本植物的盖度和生物量，也没有减轻低水分供应对林下生长速度和盖度的影响。我们的研究结果表明，预计温带林地的干旱程度增加可能导致林下生产力降低，而 eCO2 几乎没有缓解这些变化的空间。
