Abstract The effects of cover crops and fertilization on the soil properties of apple orchards have been studied widely, but our knowledge of the variations in the soil enzyme activity and stoichiometry remains limited, particularly the tree-scale spatial responses. In this study, field experiments were conducted in two main plots comprising cover crop (CC) and no cover crop (NC) treatments with four sub-plots comprising no fertilization, manure (M), N, P, and K fertilizer (NPK), and NPK fertilizer combined with manure (NPKM). We determined the activities of C, N, and P acquisition enzymes comprising β-1,4-glucosidase, (BG), β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and alkaline phosphatase (PHOS), the soil nutrient contents, and microbial biomass. Cover crop and fertilization significantly affected the soil nutrient contents, microbial biomass, and enzyme activities. Cover crop growth decreased the BG:NAG + LAP and BG:PHOS enzyme activity ratios (before mowing and mulching the cover crop). Fertilization also influenced the BG:NAG + LAP, BG:PHOS, and NAG + LAP:PHOS ratios. The soil enzyme activities were affected by the soil nutrient contents and microbial biomass, especially at distances 90 and 120 cm from the trees, as well as by the manure application treatments (M and NPKM). The soil enzyme ratios and microbial biomass ratio were influenced by the soil properties, especially at distances of 90 and 120 cm form the trees. The relationships among the soil properties, microbial biomass ratio, and soil enzyme ratios were affected by the growth of the cover crop and apple trees. The chemical fertilizer treatments (NPK and NPKM) significantly increased the negative relationships between the soil nutrient ratios and enzyme ratios. Our findings demonstrate that the C:N:P stoichiometry of the soil microbes and enzyme activities were affected by the cover crop and fertilization, and the spatial effects were detected at the tree-scale in an apple orchard.

中文翻译：

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苹果园细胞外酶活性和化学计量对不同类型施肥和覆盖作物的树尺度空间响应

摘要 覆盖作物和施肥对苹果园土壤性质的影响已被广泛研究，但我们对土壤酶活性和化学计量变化的了解仍然有限，特别是树木尺度的空间响应。在这项研究中，田间试验在包括覆盖作物 (CC) 和无覆盖作物 (NC) 处理的两个主要地块中进行，四个子地块包括不施肥、肥料 (M)、N、P 和 K 肥料 (NPK) , 和 NPK 肥料结合粪肥 (NPKM)。我们测定了 C、N 和 P 获取酶的活性，包括 β-1,4-葡萄糖苷酶 (BG)、β-1,4-N-乙酰氨基葡萄糖苷酶 (NAG)、亮氨酸氨基肽酶 (LAP) 和碱性磷酸酶 (PHOS) )、土壤养分含量和微生物生物量。覆盖作物和施肥显着影响土壤养分含量、微生物生物量和酶活性。覆盖作物生长降低了 BG:NAG + LAP 和 BG:PHOS 酶活性比率（在修剪和覆盖覆盖作物之前）。施肥还影响 BG:NAG + LAP、BG:PHOS 和 NAG + LAP:PHOS 比率。土壤酶活性受土壤养分含量和微生物生物量的影响，尤其是在距离树木 90 和 120 厘米处，以及施肥处理（M 和 NPKM）。土壤酶比和微生物生物量比受土壤性质的影响，尤其是在距离树木 90 和 120 厘米处。土壤性质、微生物生物量比和土壤酶比之间的关系受覆盖作物和苹果树生长的影响。化肥处理（NPK 和 NPKM）显着增加了土壤养分比和酶比之间的负相关关系。我们的研究结果表明，土壤微生物的 C:N:P 化学计量和酶活性受覆盖作物和施肥的影响，并且在苹果园的树尺度上检测到空间效应。