The availability of nitrogen (N) and phosphorus (P) controls the flow of carbon (C) among plants, soils, and the atmosphere, thereby shaping terrestrial ecosystem responses to global change. Soil C, N, and P cycles are linked by drivers operating at multiple spatial and temporal scales: landscape-level variation in macroclimate and soil geochemistry, stand-scale heterogeneity in forest composition, and microbial community dynamics at the soil pore scale. Yet in many biomes, we do not know at which scales most of the biogeochemical variation emerges, nor which processes drive cross-scale feedbacks. Here, we examined the drivers and spatial/temporal scales of variation in soil biogeochemistry across four tropical dry forests spanning steep environmental gradients. To do so, we quantified soil C, N, and P pools, extracellular enzyme activities, and microbial community structure across wet and dry seasons in 16 plots located in Colombia, Costa Rica, Mexico, and Puerto Rico. Soil biogeochemistry exhibited marked heterogeneity across the 16 plots, with total organic C, N, and P pools varying fourfold, and inorganic nutrient pools by an order of magnitude. Most soil characteristics changed more across space (i.e., among sites and plots) than over time (between dry and wet season samplings). We observed stoichiometric decoupling among C, N, and P cycles, which may reflect their divergent biogeochemical drivers. Organic C and N pool sizes were positively correlated with the relative abundance of ectomycorrhizal trees and legumes. By contrast, the distribution of soil P pools was driven by soil geochemistry, with larger inorganic P pools in soils with P-rich parent material. Most earth system models assume that soils within a texture class operate similarly, and ignore subgrid cell variation in soil properties. Here we reveal that soil nutrient pools and fluxes exhibit as much variation among four Neotropical dry forests as is observed across terrestrial ecosystems at the global scale. Soil biogeochemical patterns are driven not only by regional differences in soil parent material and climate, but also by local-scale variation in plant and microbial communities. Thus, the biogeochemical patterns we observed across the Neotropical dry forest biome challenge representation of soil processes in ecosystem models.

中文翻译：

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中南美洲热带干旱森林的土壤生物地球化学

氮 (N) 和磷 (P) 的可用性控制着植物、土壤和大气之间的碳 (C) 流动，从而塑造陆地生态系统对全球变化的响应。土壤 C、N 和 P 循环由在多个时空尺度上运行的驱动因素联系起来：大气候和土壤地球化学的景观水平变化、森林组成的林分尺度异质性以及土壤孔隙尺度的微生物群落动态。然而，在许多生物群落中，我们不知道大部分生物地球化学变化出现在哪个尺度，也不知道哪个过程会驱动跨尺度反馈。在这里，我们研究了跨越陡峭环境梯度的四个热带干旱森林土壤生物地球化学变化的驱动因素和空间/时间尺度。为此，我们量化了土壤 C、N 和 P 库、细胞外酶活性、以及位于哥伦比亚、哥斯达黎加、墨西哥和波多黎各的 16 个地块的旱季和旱季的微生物群落结构。土壤生物地球化学在 16 个地块中表现出明显的异质性，总有机 C、N 和 P 库变化四倍，无机养分库变化一个数量级。大多数土壤特性在空间上（即，地点和地块之间）的变化比随时间（旱季和雨季采样之间）的变化更大。我们观察到 C、N 和 P 循环之间的化学计量解耦，这可能反映了它们不同的生物地球化学驱动因素。有机碳和氮池大小与外生菌根树和豆科植物的相对丰度呈正相关。相比之下，土壤 P 库的分布是由土壤地球化学驱动的，在富含 P 母质的土壤中无机 P 库更大。大多数地球系统模型假设质地类中的土壤运行相似，并忽略土壤特性中的子网格单元变化。在这里，我们揭示了土壤养分库和通量在四个新热带干旱森林中表现出的变化与在全球范围内的陆地生态系统中观察到的一样多。土壤生物地球化学模式不仅受土壤母质和气候的区域差异驱动，还受植物和微生物群落的局部变化影响。因此，我们在新热带干旱森林生物群落中观察到的生物地球化学模式挑战了生态系统模型中土壤过程的表征。在这里，我们揭示了土壤养分库和通量在四个新热带干旱森林中表现出的变化与在全球范围内的陆地生态系统中观察到的一样多。土壤生物地球化学模式不仅受土壤母质和气候的区域差异驱动，还受植物和微生物群落的局部变化影响。因此，我们在新热带干旱森林生物群落中观察到的生物地球化学模式挑战了生态系统模型中土壤过程的表征。在这里，我们揭示了土壤养分库和通量在四个新热带干旱森林中表现出的变化与在全球范围内的陆地生态系统中观察到的一样多。土壤生物地球化学模式不仅受土壤母质和气候的区域差异驱动，还受植物和微生物群落的局部变化影响。因此，我们在新热带干旱森林生物群落中观察到的生物地球化学模式挑战了生态系统模型中土壤过程的表征。