Background and aims

Peat-accumulating wetlands have undulating surfaces of raised areas (hummocks) and depressions (hollows). Hummock-hollow microtopography in relation to the water table influences the distribution of plant species, root density, and microbial community composition, which could in turn alter carbon (C) and nitrogen (N) cycling within peatlands. We used paired hummock and hollow cores from a boreal, forested peatland to assess how microtopography influences peatland microbial function and, in turn, ecosystem C and N cycling.

Methods

The peat was analyzed for microbial biomass and potential enzyme activity in 10 cm depth increments relative to the water table, resulting in two increments for hollows and three for hummocks, which has a raised increment above the water table.

Results

Across hummocks and hollows, microbial C and N and fungal biomass generally decreased with depth from the peat surface. In contrast, potential enzyme activity often increased with depth, but this varied within enzyme functional groups according to topography, depth, or both. The potential enzyme activity of C-N degrading peptidases, for example, differed across the five topography × depth increments with the lowest rate in the aerated hummocks. Hummocks compose approximately 66% of the land area at our study site and would therefore underestimate C turnover by an average of 25% if solely used to extrapolate patterns across a forested bog.

Conclusion

Our results suggest that asynchrony in C and N cycling across the undulating surface of forested peatlands impacts our ability to accurately predict biogeochemical cycling across this important ecosystem.

中文翻译：

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深度和微地形影响森林泥炭地的微生物生物地球化学过程

 背景和目标

泥炭堆积的湿地具有起伏的凸起区域（小丘）和凹陷（凹陷）表面。与地下水位相关的丘状空心微地形影响植物物种的分布、根系密度和微生物群落组成，进而改变泥炭地内的碳（C）和氮（N）循环。我们使用来自北方森林泥炭地的成对的山丘和空心来评估微地形如何影响泥炭地微生物功能，进而影响生态系统的碳和氮循环。

 方法

对泥炭的微生物量和潜在酶活性进行了分析，以相对于地下水位 10 厘米深度的增量进行分析，导致空心增量为 2 个，丘丘增量为 3 个（在地下水位以上有一个升高的增量）。

 结果

在小丘和洼地中，微生物碳和氮以及真菌生物量通常随着距泥炭表面的深度而减少。相反，潜在的酶活性通常随着深度而增加，但这在酶功能组内根据地形、深度或两者而变化。例如，CN 降解肽酶的潜在酶活性在五个地形 × 深度增量中有所不同，其中在通气小丘中活性最低。丘丘约占我们研究地点土地面积的 66%，因此，如果仅用于推断森林沼泽的模式，则会平均低估 25% 的碳周转率。

 结论

我们的结果表明，森林泥炭地起伏表面的碳和氮循环的异步性影响了我们准确预测整个重要生态系统生物地球化学循环的能力。