Landcare Research, Private Bag 11052, Palmerston North 4442, New Zealand.
School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand.
Sci Total Environ. 2017 Jan 15;577:61-72. doi: 10.1016/j.scitotenv.2016.10.055. Epub 2016 Oct 15.
A possible agricultural climate change mitigation option is to increase the amount of soil organic carbon (SOC). Conversely, some factors might lead to inadvertent losses of SOC. Here, we explore the effect of various management options and environmental changes on SOC storage and milk production of dairy pastures in New Zealand. We used CenW 4.1, a process-based ecophysiological model, to run a range of scenarios to assess the effects of changes in management options, plant properties and environmental factors on SOC and milk production. We tested the model by using 2years of observations of the exchanges of water and CO measured with an eddy covariance system on a dairy farm in New Zealand's Waikato region. We obtained excellent agreement between the model and observations, especially for evapotranspiration and net photosynthesis. For the scenario analysis, we found that SOC could be increased through supplying supplemental feed, increasing fertiliser application, or increasing water availability through irrigation on very dry sites, but SOC decreased again for larger increases in water availability. Soil warming strongly reduced SOC. For other changes in key properties, such as changes in soil water-holding capacity and plant root:shoot ratios, SOC changes were often negatively correlated with changes in milk production. The work showed that changes in SOC were determined by the complex interplay between (1) changes in net primary production; (2) the carbon fraction taken off-site through grazing; (3) carbon allocation within the system between labile and stabilised SOC; and (4) changes in SOC decomposition rates. There is a particularly important trade-off between carbon either being removed by grazing or remaining on site and available for SOC formation. Changes in SOC cannot be fully understood unless all four factors are considered together in an overall assessment.
增加土壤有机碳（SOC）的数量是农业缓解气候变化的一种可能选择。相反，一些因素可能导致 SOC 的无意损失。在这里，我们探讨了各种管理选项和环境变化对新西兰奶牛牧场 SOC 储存和牛奶产量的影响。我们使用 CenW 4.1，一种基于过程的生理生态模型，运行了一系列情景来评估管理选项、植物特性和环境因素变化对 SOC 和牛奶产量的影响。我们通过使用在新西兰怀卡托地区的一个奶牛场的涡度协方差系统测量的水和 CO 的交换量的 2 年观测来测试该模型。我们发现模型与观测结果非常吻合，尤其是对于蒸散和净光合速率。对于情景分析，我们发现通过提供补充饲料、增加施肥或在非常干燥的地点增加灌溉来增加水的可用性可以增加 SOC，但水的可用性增加较大时 SOC 又会再次减少。土壤变暖强烈降低了 SOC。对于关键特性的其他变化，如土壤持水能力和植物根冠比的变化，SOC 的变化通常与牛奶产量的变化呈负相关。这项工作表明，SOC 的变化取决于（1）净初级生产力的变化；（2）通过放牧从现场带走的碳部分；（3）系统内易变和稳定 SOC 之间的碳分配；以及（4）SOC 分解速率的变化。在碳通过放牧被去除或留在现场并可用于 SOC 形成之间存在着特别重要的权衡。除非在总体评估中同时考虑所有四个因素，否则无法完全理解 SOC 的变化。
