Elevated CO2 (eCO2) can stimulate plant productivity and increase carbon (C) input to soils, but nutrient limitation restricts productivity. Despite phosphorus (P)-limited ecosystems increasing globally, it is unknown how nutrient cycling, particularly soil microbial extra cellular enzyme activity (EEA), will respond to eCO2 in such ecosystems. Long-term nutrient manipulation plots from adjacent P-limited acidic and limestone grasslands were exposed to eCO2 (600 ppm) provided by a mini-Free Air CO2 Enrichment system. P-limitation was alleviated (35 kg-P ha−1 y−1 (P35)), exacerbated (35 kg-N ha−1 y−1 (N35), 140 kg-N ha−1 y−1 (N140)), or maintained (control (P0N0)) for > 20 years. We measured EEAs of C-, N- and P-cycling enzymes (1,4-β-glucosidase, cellobiohydrolase, N-acetyl β-D-glucosaminidase, leucine aminopeptidase, and acid phosphatase) and compared C:N:P cycling enzyme ratios using a vector analysis. Potential acid phosphatase activity doubled under N additions relative to P0N0 and P35 treatments. Vector analysis revealed reduced C-cycling investment and increased P-cycling investment under eCO2. Vector angle significantly increased with P-limitation (P35 < P0N0 < N35 < N140) indicating relatively greater investment in P-cycling enzymes. The limestone grassland was more C limited than the acidic grassland, characterised by increased vector length, C:N and C:P enzyme ratios. The absence of interactions between grassland type and eCO2 or nutrient treatment for all enzyme indicators signaled consistent responses to changing P-limitation and eCO2 in both grasslands. Our findings suggest that eCO2 reduces C limitation, allowing increased investment in P- and N-cycle enzymes with implications for rates of nutrient cycling, potentially alleviating nutrient limitation of ecosystem productivity under eCO2.

中文翻译：

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土壤 C、N 和 P 循环酶对高 CO2 养分限制的反应

升高的二氧化碳 (eCO2) 可以刺激植物生产力并增加土壤的碳 (C) 输入，但养分限制会限制生产力。尽管全球范围内受磷 (P) 限制的生态系统不断增加，但尚不清楚养分循环，尤其是土壤微生物细胞外酶活性 (EEA)，将如何响应此类生态系统中的 eCO2。来自相邻的限磷酸性和石灰岩草地的长期养分控制地块暴露于由微型游离空气 CO2 富集系统提供的 eCO2 (600 ppm)。P-限制减轻（35 kg-P ha-1 y-1 (P35)），加剧（35 kg-N ha-1 y-1 (N35)，140 kg-N ha-1 y-1 (N140)） )，或维持（对照 (P0N0)）> 20 年。我们测量了 C-、N- 和 P-循环酶（1,4-β-葡萄糖苷酶、纤维二糖水解酶、N-乙酰 β-D-氨基葡萄糖苷酶、亮氨酸氨基肽酶、和酸性磷酸酶）并使用载体分析比较 C:N:P 循环酶的比例。相对于 P0N0 和 P35 处理，在 N 添加下潜在的酸性磷酸酶活性加倍。矢量分析显示，在 eCO2 下，C 循环投资减少，P 循环投资增加。矢量角随 P 限制显着增加（P35 < P0N0 < N35 < N140），表明对 P 循环酶的投资相对较大。石灰岩草地比酸性草地更受 C 限制，其特征是载体长度、C:N 和 C:P 酶比增加。草地类型与 eCO2 或所有酶指标的营养处理之间没有相互作用，这表明两个草地对 P 限制和 eCO2 变化的反应一致。我们的研究结果表明，eCO2 减少了 C 限制，