Long-term ecosystem development is characterized by a switch from nitrogen (N) to phosphorus (P) limitation of plant communities as soils age, which leads to changes in plant biomass, diversity, and foliar nutrient concentrations. Similar effects occur belowground, although the extent to which nutrient availability is the primary driver of long-term changes in soil microbial communities remains uncertain. To investigate this, we assessed proxies for soil microbial nutrient limitation along the Jurien Bay dune chronosequence in Western Australia, where a long-term decline in P availability is reflected in strong variation in plant and microbial community composition over 2 million years of soil development. We quantified carbon (C), N, and P in the soil microbial biomass, assayed soil enzymes involved in the acquisition of those nutrients from soil organic matter, and used microbial stoichiometric ratios and vector analysis of enzyme activities to assess whether long-term changes in soil nutrient availability are reflected in nutrient demand by soil microbes. Concentrations of microbial nutrients peaked in Holocene soils (1–6.5 ky), although differences in microbial P were not significant. There were no significant differences in microbial nutrient ratios (C:N, C:P, and N:P) along the chronosequence. Acid phosphatase activity increased continually throughout the chronosequence, while the activities of leucine aminopeptidase and β-glucosidase were greatest in Holocene soils and declined with increasing soil age. Corresponding vector lengths indicated greater investment in C-degrading enzymes in Holocene soils (≤6.5 ky), while vector angles indicated greater investment in the acquisition of P compared with N in Pleistocene soils (≥120 ky). Overall, these findings show that changes in nutrient availability during long-term pedogenesis at Jurien Bay are reflected in microbial investment in nutrient acquisition, but that the soil microbial biomass exhibits a remarkable degree of homeostasis despite major shifts in nutrient availability and community composition over 2 million years of ecosystem development.

中文翻译：

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沿 200 万年沙丘时间顺序的微生物营养限制

长期生态系统发展的特点是，随着土壤老化，植物群落的限制从氮 (N) 转变为磷 (P)，从而导致植物生物量、多样性和叶面养分浓度的变化。类似的影响也发生在地下，尽管养分有效性在多大程度上是土壤微生物群落长期变化的主要驱动因素仍不确定。为了调查这一点，我们评估了西澳大利亚朱里恩湾沙丘年代土壤微生物养分限制的代理，其中磷有效性的长期下降反映在200万年土壤发育过程中植物和微生物群落组成的强烈变化。我们量化了土壤微生物生物量中的碳 (C)、N 和 P，分析了从土壤有机质中获取这些养分所涉及的土壤酶，并使用微生物化学计量比和酶活性矢量分析来评估是否存在长期变化土壤养分有效性反映在土壤微生物的养分需求中。微生物养分浓度在全新世土壤中达到峰值（1-6.5 ky），尽管微生物磷的差异并不显着。微生物营养比（C:N、C:P 和 N:P）沿时间顺序没有显着差异。酸性磷酸酶活性在整个时间序列中持续增加，而亮氨酸氨肽酶和β-葡萄糖苷酶活性在全新世土壤中最大，并随着土壤年龄的增加而下降。相应的矢量长度表明全新世土壤（≤6.5 ky）中对碳降解酶的投入更大，而矢量角度表明更新世土壤（≥120 ky）中对磷的获取比氮的投入更大。总体而言，这些发现表明，朱里恩湾长期成土过程中养分有效性的变化反映在养分获取的微生物投资中，但尽管养分有效性和群落组成发生了超过 2 年的重大变化，但土壤微生物生物量表现出显着程度的稳态。亿年的生态系统发展。