英文文献：Native Grassland Conversion: the Roles of Risk Intervention and Switching Costs-原生草地转换:风险干预与转换成本的作用
英文文献作者：Miao, Ruiqing,Hennessy, David A.,FENG, HONGLI
英文文献摘要：
We develop a real option model of the irreversible native grassland conversion decision. Upon plowing, native grassland can be followed by either a permanent cropping system or a system in which land is put under cropping (respectively, grazing) whenever crop prices are high (respectively, low). Switching costs are incurred upon alternating between cropping and grazing. The effects of risk intervention in the form of crop insurance subsidies are studied, as are the effects of cropping innovations that reduce switching costs. We calibrate the model by using cropping return data for South Central North Dakota over 1989-2012. Simulations show that a risk intervention that offsets 20% of a cropping return shortfall increases the sod-busting cost threshold, below which native sod will be busted, by 41% (or $43.7/acre). Omitting cropping return risk across time underestimates this sod-busting cost threshold by 23% (or $24.35/acre) and hence underestimates the native sod conversion caused by crop production.

建立了一个不可逆的天然草地转化率决策的实物期权模型。在耕地之后，原生草地可以是永久种植制度，也可以是在作物价格高(分别低)时进行种植(分别放牧)的制度。在放牧和放牧之间的交替中产生转换成本。研究了以作物保险补贴形式进行的风险干预的效果，以及降低转换成本的种植创新的效果。我们使用1989-2012年北达科他州中南部的种植回报数据来校准模型。模拟结果显示，如果风险干预能够弥补20%的作物回报缺口，那么破草成本阈值就会增加41%(约合43.7美元/英亩)。如果不考虑随时间变化的种植回报风险，就低估了这个除草成本阈值23%(或24.35美元/英亩)，从而低估了由作物生产引起的天然sod转化。