In the Brigalow Belt bioregion of Australia, clearing of brigalow (Acacia harpophylla) scrub vegetation for agriculture has altered nutrient cycling over millions of hectares. In order to quantify the effect of this vegetation clearing and land use change on soil fertility, the Brigalow Catchment Study commenced in 1965. Initial clearing and burning of brigalow scrub resulted in a temporary increase of mineral nitrogen, total and available phosphorus, total and exchangeable potassium and total sulfur in the surface soil (0–0.1 m) as a result of soil heating and the ash bed effect. Soil pH also increased, but did not peak immediately after burning. Soil fertility declined significantly over the subsequent 32 years. Under cropping, organic carbon declined by 46%, total nitrogen by 55%, total phosphorus by 29%, bicarbonate-extractable phosphorus by 54%, acid-extractable phosphorus by 59%, total sulfur by 49%, total potassium by 9% and exchangeable potassium by 63% from post-burn, pre-cropping concentrations. Fertility also declined under grazing but in a different pattern to that observed under cropping. Organic carbon showed clear fluctuation but it was not until the natural variation in soil fertility over time was separated from the anthropogenic effects of land use change that a significant decline was observed. Total nitrogen declined by 22%. Total phosphorus declined by 14%, equating to only half of the decline under cropping. Bicarbonate-extractable phosphorus declined by 64% and acid-extractable phosphorus by 66%; both greater than the decline observed under cropping. Total sulfur declined by 23%; less than half of the decline under cropping. A similar decline in total potassium was observed under both land uses, with a 10% decline under grazing. Exchangeable potassium declined by 59%. The primary mechanism of nutrient loss depended on the specific land use and nutrient in question.

中文翻译：

---

Brigalow 流域研究：V*。澳大利亚昆士兰州的清除和燃烧 brigalow (Acacia harpophylla) 在作物或放牧条件下养分下降之前暂时增加了表层土壤肥力

在澳大利亚的 Brigalow Belt 生物区，清除 brigalow (Acacia harpophylla) 灌木植被用于农业改变了数百万公顷的养分循环。为了量化这种植被清除和土地利用变化对土壤肥力的影响，1965 年开始了 Brigalow 集水区研究。 Brigalow 灌木丛的初始清除和燃烧导致矿物氮、总磷和可用磷、总磷和可交换磷的暂时增加由于土壤加热和灰床效应，表层土壤（0-0.1 m）中的钾和总硫。土壤 pH 值也增加，但燃烧后不会立即达到峰值。在随后的 32 年中，土壤肥力显着下降。种植期间，有机碳下降了 46%，总氮下降了 55%，总磷下降了 29%，碳酸氢盐可提取的磷为 54%，酸可提取的磷为 59%，总硫为 49%，总钾为 9%，可交换钾为 63%，来自燃烧后、种植前的浓度。放牧时生育率也下降，但与种植时观察到的模式不同。有机碳显示出明显的波动，但直到土壤肥力随时间的自然变化与土地利用变化的人为影响分离后，才观察到显着下降。总氮下降了 22%。总磷下降了 14%，仅相当于种植期间下降的一半。碳酸氢盐可提取的磷下降了 64%，酸提取的磷下降了 66%；两者都大于在种植条件下观察到的下降。总硫量下降了 23%；不到种植减少的一半。在两种土地利用下观察到的总钾含量类似下降，放牧下降 10%。可交换钾下降了 59%。养分流失的主要机制取决于具体的土地利用和养分问题。