香榧主产区林地土壤养分空间异质性及其肥力评价

选取浙江省香榧(Torreya grandis cv.Merrillii)主产区为研究对象,系统采集表层土壤(0—20 cm)样品121个,基于地统计学及Moran′s I等空间分析方法揭示土壤养分的空间异质性,估算了香榧林地土壤综合肥力并分析其影响因素。结果表明:研究区土壤pH较低,有机质、碱解氮、有效磷和速效钾含量较高,平均含量分别为4.91、30.60 g/kg、136.77 mg/kg、15.02 mg/kg、153.42 mg/kg;基于半方差函数分析得出,土壤pH和养分要素属于中等空间相关性,其中pH的变程最小为3.29 km,有机质、碱解氮、有效磷和速效钾的变程分别为8.52、5.84、8.82、6.49 km;克里格空间插值和局部Moran′s I指数结果揭示土壤pH、有机质、碱解氮、有效磷和速效钾均存在明显的空间分布格局和局部空间聚集现象,土壤有机质、碱解氮、有效磷和速效钾低值区主要分布在诸暨市和东阳市,高值区主要分布在柯桥区和嵊州市,而pH的空间分布格局与之相反;诸暨市和东阳市部分地区土壤综合肥力指数较低,而其他区域的土壤肥力水平较高。总体上,浙江省香榧主产区土壤酸化以及养分失衡现象较为严重,尤其是速效钾含量过高。从相关性分析结果来看,环境变量对香榧林地土壤养分的影响较小,而林龄对土壤pH和养分的影响较大。可见,研究区土壤养分受人为活动影响明显。因此,需根据实际情况,改善林农的施肥管理方式,调整施肥数量和结构并开展土壤酸性改良,因地制宜制定区域施肥规划。

Spatial variation of soil nutrients and evaluation of integrated soil fertility in Torreya grandis cv. Merrillii region

A total of 121 topsoil samples (0-20 cm) were systematically collected from typical producing areas of Torreya grandis cv. Merrillii in Zhejiang Province. Geostatistics and Moran''s I were utilized to reveal the spatial heterogeneity of soil nutrients. Integrated soil fertility index (IFI) of Torreya grandis cv. Merrillii plantations were estimated and its driving factors were analyzed. The results indicated that soil pH was lower and the concentrations of organic matter (OM), available nitrogen (AN), available phosphorus (AP) and available potassium (AK) were higher, with average concentrations of 4.91 g/kg, 30.60 g/kg, 136.77 mg/kg, 15.02 mg/kg, and 153.42 mg/kg, respectively. Soil pH and nutrient elements had moderately spatial correlation. The minimum range value of pH was 3.29 km, and the ranges of OM, AN, AP and AK were 8.52 km, 5.84 km, 8.82 km and 6.49 km, respectively. The results of Kriging and the local Moran''s I showed that soil properties had the obviously spatial distribution patterns and locally spatial aggregation in the study area. The low pH values were located in the city of Keqiao and Shengzhou and high values in the city of Zhuji and Dongyang. The spatial distribution patterns of OM, AN, AP, AK were opposite. The low values were mainly in the city of Zhuji and Dongyang and high values were found in the city of Keqiao and Shengzhou. Soil pH and nutrients had moderately spatial auto-correlation. The scales of spatial variability were basically similar. The results of the integrated soil fertility evaluation indicated that the soil fertility level was higher in most areas, and the IFI was lower in Zhuji and Dongyang. In general, the soil acidification and nutrient imbalances in the producing areas of Torreya grandis cv. Merrillii in Zhejiang Province were serious, especially the excessively high AN concentration. The correlation analysis showed that the environmental variables had little effect on soil nutrients of Torreya grandis cv. Merrillii, while forest ages had the great effect on soil pH and nutrients. It can be observed that the soil nutrients in the study area were obviously affected by anthropogenic activities. Therefore, it is urgent to improve the fertilization management mode, to carry out soil acid improvement, and to make regional fertilization planning according to regional conditions.