摘要
Eleven soil types, which can be identified and delineated using conventional soil survey procedures, were characterized for loblolly pine （Pinus taeda L.） productivity. Four 4-hectare study sites, each containing four measurement plots, were established for every soil type studied. In a stepwise multiple regression, both soil parent material （i.e. a combination of subsoil texture and geology） （p〈0.001）, and drainage class （p=0.006） were significant predictors of site index （tree age 25）, and the overall linear regression model had an R2 value of 0.55. The extremes of soil parent material differed by 3.9 m site index （loamy subsoil on the Wicomico-Penholoway surfaces versus clayey subsoil on the Pamlico-Princess Anne surfaces）. Each increment of drainage class differed by 0.7 m site index. For example, a poorly drained soil had 0.7 m lower site index than a somewhat poorly drained soil. For seven of the eleven soil types studied, there is greater than 80% probability that estimated mean site index is within ±0.8 m of the actual soil type mean site index. The other four soil types （labeled G, I, C and K） need to be either redefined or sampled more intensively. Two of these need to be subdivided in order to adequately characterize site quality, one based on geology （Soil type G） and one based on soil drainage class （Soil type I）. Variation in soil drainage class and varying amounts of topsoil displaced into windrows were both factors influencing site quality variation of a third soil type （Soil type C）. The wide variation in site index data for a fourth soil type （Soil type K） appeared to be due, in part, to sampling study locations and individual measurement plots with less than optimum bedding and/or artificial drainage. Soil parent material （subsoil texture and geology） along with drainage class were found to be important factors influencing site quality on the South Carolina Lower Coastal Plain.
利用常规土壤调查方法辨认和描述了11种土壤类型,以便分析火炬松(Pinus taeda L.)的生产力。每个土壤类型建立4个4公顷的研究地点(每个研究地点包含4个测量样地)上。利用逐步多元回归分析土壤母质层(结合下层土壤质地和地质学)和排灌级别,它们是立地指标(树龄25年)重要的预测值,整个线性回归模型的相关系数(R2)为0.55。在Wicomico-Penholoway地区的肥沃下层土与Pamlico-Princess Anne地区的黏土的土壤母质层立地指标最大相差3.9m。排灌级别的立地指标最大相差0.7m。例如,排灌差的土壤的立地指标比稍差的低0.7m。11个土壤类型中的7个土壤类型,80%以上估计的平均立地指标与实际的土壤类型平均立地指标相差±0.8m。其它4个土壤类型(标号:G,I,C和K)需要重新定义或更多地集中采样。为了精确的定性立地质量,需要对其中两个土壤类型(基于地质学的土壤类型G和基于土壤排灌级别土壤类型I)进行重新划分。土壤排灌级别的变化和上层土壤被转化为干草列的变化数量是两个影响土壤类型(C)立地质量的影响因子。第4个土壤类型K立地指标数据有很大的变化,部分原因是由于采样地点和个别测量样地的优良垫层和人工排灌设施较少。具有不同排灌级别的土壤母质层(结合下层土壤质地和地质学)是重要的卡罗莱纳州南部海岸地区的立地质量的影响因子。
