Net primary productivity of soybean using different data sources and estimation methods

ABSTRACT Net primary productivity (NPP) can be used to quantify the relative role of climate and human activities in vegetation dynamics. Given its importance, many NPP estimation models have been developed, but some of the required data is still limited. Therefore, this study aimed to estimate the potential and actual NPP by testing different approaches regarding the data source and estimation methods and evaluate the human appropriation of NPP (HANPP) in a soybean field cultivated in southern Brazil. For this, data were obtained from field-measured NPP in soybean cultivation in Carazinho, Rio Grande do Sul, Brazil, and compared to the potential and actual NPP estimations using the CASA model and data from ERA-Interim. Subsequently, land use changes due to agricultural activities were evaluated from the potential and actual NPP through HANPP. No significant difference was observed associated with the used data sources, showing that the ERA-Interim reanalysis weather data can be employed for this purpose. The actual NPP estimations by the CASA model were consistent with a high association with the data measured in the field. HANPP, through only one annual soybean cultivation, represented 29% of the potential NPP in the region. It indicates the potential to increase intensification with annual crops in the region.

摘要
净初级生产力（Net Primary Productivity, NPP）可用于量化气候与人类活动在植被动态中的相对作用。鉴于其重要性，现有研究已开发出诸多NPP估算模型，但部分所需数据仍存在匮乏问题。为此，本研究旨在通过测试不同数据源与估算方法方案，估算潜在与实际净初级生产力，并评估巴西南部一处大豆种植农田的人类占用净初级生产力（Human Appropriation of Net Primary Productivity, HANPP）。
本研究从巴西南里奥格兰德州卡拉齐纽（Carazinho）的大豆种植田块获取田间实测NPP数据，并将其与采用CASA模型及ERA-Interim数据得到的潜在、实际NPP估算结果进行对比。随后，基于人类占用净初级生产力（HANPP），结合潜在与实际NPP评估农业活动引发的土地利用变化。
研究未观测到所用数据源间存在显著差异，表明ERA-Interim再分析气象数据可适用于该类研究场景。通过CASA模型得到的实际NPP估算结果与田间实测数据具有高度相关性，二者一致性良好。该区域仅开展一年一季大豆种植所产生的人类占用净初级生产力，占区域潜在净初级生产力的29%。这表明该区域具备通过一年生作物提升种植集约化程度的潜力。