Griffith School of Environment and Science and the Australian Rivers Institute, Griffith University, Nathan, Queensland, Australia.
Department of Agriculture and Fisheries and University of the Sunshine Coast, Sippy Downs, Queensland, Australia.
Ecology. 2019 Jul;100(7):e02732. doi: 10.1002/ecy.2732. Epub 2019 May 9.
Decadal-scale increases in fire frequency have the potential to deplete ecosystems of essential nutrients and consequently impede nutrient-limited biological processes via stoichiometric imbalance. Decomposition, a fundamental ecosystem function and strong driver of future fire occurrence, is highly sensitive to nutrient availability and is, therefore, particularly important in this context. Here we show that 40 yr of quadrennial (4yB) and biennial (2yB) prescribed burning result in severely P- and N-depleted litter stoichiometry, respectively, relative to fire exclusion. These effects exacerbated the nutrient limitation of microbial activities, constraining litter decomposition by 42.1% (4yB) and 23.6% (2yB) relative to unburned areas. However, invertebrate-driven decomposition largely compensated for the diminished capacity of micro-organisms under 4yB, suggesting that invertebrates could have an important stabilizing influence in fire-affected ecosystems. This effect was strongly positively coupled with the strength of microbial P-limitation and was not obviously or directly driven by fire regime-induced changes in invertebrate community assemblage. Together, our results reveal that high-frequency fire regimes promote nutrient-poor, carbon-rich ecosystem stoichiometry and, in doing so, disrupt ecosystem processes and modify the relative functionality of micro-organisms and invertebrates.
十年尺度的火灾频率增加有可能耗尽生态系统中的必需养分，并通过化学计量失衡来阻碍养分限制的生物过程。分解作用是生态系统的基本功能，也是未来火灾发生的主要驱动力，它对养分的有效性高度敏感，因此在这种情况下尤为重要。在这里，我们发现，与火灾隔离相比，40 年来每四年（4yB）和每两年（2yB）进行一次的计划烧除分别导致落叶层化学计量比严重缺乏磷和氮。这些影响加剧了微生物活性的养分限制，使落叶分解分别减少了 42.1%（4yB）和 23.6%（2yB）。然而，无脊椎动物驱动的分解在很大程度上弥补了微生物在 4yB 下的能力下降，这表明无脊椎动物可能对受火灾影响的生态系统具有重要的稳定作用。这种效应与微生物磷限制的强度呈强烈正相关，而不是由火灾制度引起的无脊椎动物群落组合变化直接驱动的。总之，我们的研究结果表明，高频率的火灾制度促进了养分贫瘠、富含碳的生态系统化学计量比，并由此破坏了生态系统过程，改变了微生物和无脊椎动物的相对功能。
