Data from: Plant attributes interact with fungal pathogens and nitrogen addition to drive soil enzymatic activities and their temporal variation

Nitrogen enrichment can alter soil communities and their functioning
directly, via changes in nutrient availability and stoichiometry, or
indirectly, by changing plant communities or the abundance of consumers.
However, most studies have only focused on one of these potential drivers
and we know little about the relative importance of the different
mechanisms (changes in nutrient availability, in plant diversity or
functional composition, or in consumer abundance) by which nitrogen
enrichment affects soil functioning. In addition, soil functions could
vary dramatically between seasons, however, they are typically measured
only once during the peak growing season. We therefore know little about
the drivers of intra-annual stability in soil functioning. In this study,
we measured activities of β-glucosidase and acid phosphatase, two
extracellular enzymes that indicate soil functioning. We did so in a large
grassland experiment which tested the effects, and relative importance, of
nitrogen enrichment, plant functional composition and diversity, and
foliar pathogen presence (controlled by fungicide) on soil functioning. We
measured the activity of the two enzymes across seasons and years to
assess the stability and temporal dynamics of soil functioning. Overall
β-glucosidase activity was slightly increased by nitrogen enrichment over
time but did not respond to the other experimental treatments. Conversely,
plant functional diversity, and interactions between plant attributes and
fungicide application, were important drivers of mean acid phosphatase
activity. The temporal stability of both soil enzymes was differently
affected by two facets of plant diversity: species richness increased
temporal stability and functional diversity decreased it; however, these
effects were dampened when nitrogen and fungicide were added. Synthesis:
The fungicide effects on soil enzyme activities suggest that foliar
pathogens can also affect belowground processes and the interacting effect
of fungicide and plant diversity suggests that these plant enemies can
modulate the relationship between plant diversity and ecosystem
functioning. The contrasting effects of our treatments on the mean versus
stability of soil enzyme activities clearly show the need to consider
temporal dynamics in belowground processes, to better understand the
responses of soil microbes to environmental changes such as nutrient
enrichment.

氮富集可通过改变养分有效性与化学计量比直接改变土壤群落及其功能，或通过改变植物群落或消费者丰度间接产生此类影响。然而，绝大多数现有研究仅聚焦于上述潜在驱动因素之一，我们对氮富集影响土壤功能的不同机制（养分有效性变化、植物多样性或功能组成变化、消费者丰度变化）的相对重要性知之甚少。

此外，土壤功能在不同季节间可能存在显著差异，但相关测量通常仅在生长旺盛季开展一次。因此，我们对土壤功能的年内稳定性驱动机制仍缺乏认知。

本研究针对两项指示土壤功能的胞外酶——β-葡萄糖苷酶（β-glucosidase）与酸性磷酸酶（acid phosphatase）的活性开展了测定。实验依托一项大型草地野外控制实验，旨在探究氮富集、植物功能组成与多样性，以及由杀菌剂调控的叶部病原菌存在情况对土壤功能的影响及其相对重要性。我们在多个季节与年份间测定了这两种酶的活性，以评估土壤功能的稳定性与时间动态。

总体而言，随时间推移，氮富集可小幅提升β-葡萄糖苷酶活性，但对其余实验处理无响应。与之相反，植物功能多样性，以及植物属性与杀菌剂施用的交互作用，是影响酸性磷酸酶平均活性的关键驱动因素。两种土壤酶的时间稳定性分别受到植物多样性两个维度的差异化影响：物种丰富度可提升时间稳定性，而功能多样性则会降低稳定性；不过，当施加氮素与杀菌剂时，此类效应会被削弱。

综合来看：杀菌剂对土壤酶活性的影响表明，叶部病原菌同样可调控地下生态过程；杀菌剂与植物多样性的交互效应则提示，这类植物天敌可调节植物多样性与生态系统功能之间的关联。本研究中不同处理对土壤酶活性均值与稳定性的差异化影响，清晰表明需在地下生态过程研究中纳入时间动态维度，以更好地理解土壤微生物对养分富集等环境变化的响应。