Abstract Semi-arid shrublands in southern California are exposed to high levels of atmospheric dry nitrogen (N) deposition, which can alter soil microbial activity, and thus, ecosystem carbon (C) and N cycling and storage. We used archived soil samples to assess the relative effects of experimental N enrichment on the potential activity of key C, N, and phosphorus (P) cycling enzymes in chaparral and coastal sage scrub (CSS) shrublands over a 14 year period. Chaparral plots exposed to N exhibited a significant decline in β-glucosidase and phosphatase activity and an increase in peroxidase activity over time, while N exposure had no consistent effect on N-acetylglucosaminidase (NAGase) activity. In contrast, N exposure did not significantly affect the activity of any of the measured enzymes in CSS. However, ANCOVA results revealed that the potential response of some enzymes to cumulative N input was affected by annual rainfall, because significantly more N accumulated in the soil during times of low rainfall. These results indicate that chronic dry season N inputs to semi-arid shrublands can fundamentally alter potential enzyme activity, but the impact depends on climate and vegetation type.

中文翻译：

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半干旱灌木林中长期实验性氮沉降改变了潜在的土壤细胞外酶活性

摘要 加利福尼亚南部的半干旱灌木地暴露于高水平的大气干氮 (N) 沉积，这会改变土壤微生物活动，从而改变生态系统碳 (C) 和氮的循环和储存。我们使用存档的土壤样本来评估实验性富氮对丛林和沿海鼠尾草灌木丛 (CSS) 灌木丛中关键 C、N 和磷 (P) 循环酶在 14 年期间的潜在活性的相对影响。暴露于 N 的灌木丛地块表现出 β-葡萄糖苷酶和磷酸酶活性显着下降，而过氧化物酶活性随时间增加，而 N 暴露对 N-乙酰氨基葡萄糖苷酶 (NAGase) 活性没有一致的影响。相比之下，N 暴露不会显着影响 CSS 中任何测量酶的活性。然而，ANCOVA 结果表明，一些酶对累积 N 输入的潜在反应受年降雨量的影响，因为在低降雨量期间，土壤中积累的 N 明显更多。这些结果表明，对半干旱灌木地的慢性旱季氮输入可以从根本上改变潜在的酶活性，但影响取决于气候和植被类型。