Agro-ecosystem energy profiles reveal energy flows into, within, and out of US Great Plains farm communities across 140 years. This study evaluates external energy inputs such as human labor, machinery, fuel, and fertilizers. It tracks the energy content of land produce, including crops, grazed pasture, and firewood, and also accounts unharvested energy that remains available for wildlife. It estimates energy redirected through livestock feed into draft power, meat, and milk, and estimates the energy content of final produce available for local consumption or market sale. The article presents energy profiles for three case studies in Kansas in 1880, 1930, 1954, and 1997. Two energy transformations occurred during that time. The first, agricultural colonization, saw farm communities remake the landscape, turning native grassland into a mosaic of cropland and pasture, a process that reduced overall landscape energy productivity. A second energy transition occurred in the mid-twentieth century, characterized by fossil fuel energy imports. That outside energy raised harvested and unharvested energy flows, reused biomass energy, and also final produce. This socio-ecological transition increased landscape energy productivity by 33 to 45% above presettlement conditions in grain-growing regions. These energy developments were not uniform across the plains. Variations in rainfall and soil quality constrained or favored energy productivity in different places. The case studies reveal the spatial variation of energy profiles in Great Plains agro-ecosystems, while the longitudinal approach tracks temporal change.

中文翻译：

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农业前沿的能源概况：美国大平原，1860-2000年。

农业生态系统的能源状况揭示了140年间美国大平原农场社区内外的能源流入。这项研究评估了外部能源输入，例如人力，机械，燃料和肥料。它可以追踪包括农作物，牧场和柴火在内的土地产品的能量含量，还可以算出野生生物仍然可以利用的未收获能量。它估计了通过牲畜饲料转化为生吃力，肉和牛奶的能量，并估计了可用于本地消费或市场销售的最终产品的能量含量。本文介绍了在1880年，1930年，1954年和1997年在堪萨斯州进行的三个案例研究的能量分布。在此期间发生了两次能量转换。一，农业殖民化看到农场社区进行了景观改造，将原生草地变成了农田和牧场的马赛克，这一过程降低了整体景观能源生产率。第二个能源转型发生在二十世纪中叶，其特征是进口化石燃料能源。外部能量增加了收获和未收获的能量流，可再利用的生物质能以及最终产品。这种社会生态转变将谷物种植区的景观能源生产率提高了33％至45％，超过了预定的条件。这些能源发展在整个平原上并不统一。降雨和土壤质量的变化在不同地方限制或有利于能源生产率。案例研究揭示了大平原农业生态系统中能量分布的空间变化，而纵向方法则跟踪了时间变化。