基于植被初级生产力的农用地理论和可实现产能核算研究

为解决传统基于农用地分等成果计算农用地理论产能和可实现产能时遇到的问题,本文将植被初级生产力(NPP)测算应用于农用地产能核算。以湖北省武汉市为研究区,运用CASA模型测算研究区农用地NPP,通过样点调查分别建立NPP与农用地理论单产和可实现单产的线性回归模型,在此基础上进行农用地理论产能和可实现产能核算。通过核算得到研究区75个乡镇的农用地理论产能及单产和可实现产能及单产,理论和可实现产能较大的乡镇主要分布在研究区北部及东南部地区,理论和可实现单产较大的乡镇则主要分布在研究区西部和东北地区,而靠近主城区周边乡镇的理论和可实现产能及单产均较低。将核算结果与传统方法计算得到的农用地产能核算成果进行对比分析,发现两种方法的核算成果在乡镇理论和可实现产能分布上非常接近,具有较高一致性;但在乡镇理论单产和可实现单产分布上并不完全一致。研究结果表明基于NPP测算的农用地产能核算方法是可行的,该方法避免了传统核算方法资料收集繁琐,主观性强等不足,且不以农用地分等定级成果为基础,可实现农用地产能快速核算。

Using vegetation net primary productivity to determine theoretical and achievable farmland productivity

Food security is one of the main problems facing China and researches on establishing farmland productivity are of vital significance for food productivity and safety. Traditional calculations of farmland productivity have been based on farmland grading to establish functional relations among the natural quality of farmland, grade index, theoretical yield and achievable yield using sample surveys. The deficiencies that associated with this calculation method have included tedious data collection and strong subjectivity. In the attempt to avoid these deficiencies, this paper used vegetation net primary productivity (NPP) method to determine farmland productivity in Wuhan, Hubei Province. The paper used NDVI and EVI data, monthly average precipitation, monthly average temperature, monthly total solar radiation and other meteorological data to run the CASA model. The model then was used to calcu-late NPP of farmlands in the region and establish functional relations among theoretical and achievable yields, NPP of farmlands using sample survey data. The unit productivity (UP) was obtained by substituting NPP data into the established relation functions. Then productivities of different towns were aggregations of UP multipling its corresponding area, while the yields of towns were quotients of productivity divided by total farmland area of the towns. Theoretical and achievable productivities and yields in 75 townships in the study area were calculated using the NPP method. While townships with larger theoretical and achievable productivities were mainly in the northern and southeast regions, townships with larger theoretical and achievable yields were in the western and northeast regions of the study area. Also both theoretical and achievable productivities and yields were lower in peripheral townships in close proximity with main cities. By contrast, comparison of the NPP and traditional method showed that the calculated results by the two methods were highly consistent in terms of theoretical and achievable productivities, but not entirely consistent in terms of theoretical and achievable yields. The results therefore showed that it was feasible to apply NPP method on estimating the productivity of farmlands. The NPP method was advantageous over the traditional method because it not only avoided deficiencies inherent in the traditional method, but was also a quick way of calculating farmland productivity without need for farmland grading and rating.