Welpelo Carla, Dubbert Maren, Tiemeyer Bärbel, Knohl Alexander, Piayda Arndt
Thünen Institute of Climate-Smart Agriculture Braunschweig Germany.
Leibniz Centre for Agricultural Landscape Research (ZALF) Müncheberg Germany.
Ecol Evol. 2024 Dec 18;14(12):e70745. doi: 10.1002/ece3.70745. eCollection 2024 Dec.
Rewetted bogs with high water levels (WL) and mire-specific vegetation are crucial carbon (C) sinks, but their function might be threatened by tree encroachment, a phenomenon widespread in the northern hemisphere that often coincides with low WL. This might impact C cycling both at the ecosystem and microform scale in multiple ways, but so far, data are lacking. We established two sites in the same former peat extraction area, one showing permanently high WL and mire-specific vegetation (open site, OS), while the other one has more fluctuating WL and a dense birch ( Ehrh.) population (tree site, TS). We measured the carbon dioxide (CO) exchange at ecosystem (eddy covariance) and plot scale (chamber measurements) for 1 year to clarify the differences between the sites and the impact of birch encroachment on the contribution of the different bog-specific microforms and the trees to the ecosystem's CO balance. Overall, the OS had a CO balance of -262.4 ± 7.8 g CO-C m year indicating CO uptake, while the TS was close to neutral (-28 ± 5.1 g CO-C m year). The smaller uptake at the TS was caused by higher (151%) ecosystem respiration, while gross primary production was 14% higher. However, the microform contributions to C uptake strongly differed: At the OS, both hummocks and hollows showed net uptake, while at the TS, most C (52%) was assimilated by the birches and the understory was a net CO source. This indicates a loss of peat C from the TS, while the successfully rewetted site was accumulating new peat. Accounting for plot-scale CH fluxes, both sites were a weak source of greenhouse gases, but a distinctly stronger C sink occurred at the OS. Our data show the possibility of increasing C removal from the atmosphere by full rewetting and the establishment of mire-specific vegetation.
水位较高且有特定泥炭地植被的重新湿润的沼泽是重要的碳汇，但它们的功能可能受到树木入侵的威胁，这一现象在北半球广泛存在，且常与低水位同时出现。这可能会以多种方式影响生态系统和微地形尺度上的碳循环，但目前尚缺乏相关数据。我们在同一个 former peat extraction area 建立了两个站点，一个站点水位常年较高且有特定泥炭地植被（开阔站点，OS），另一个站点水位波动较大且有密集的桦树种群（树木站点，TS）。我们测量了一年中生态系统（涡度相关法）和样地尺度（箱式测量）的二氧化碳（CO₂）交换，以阐明站点之间的差异以及桦树入侵对不同泥炭地特定微地形和树木对生态系统 CO₂平衡贡献的影响。总体而言，OS 的 CO₂平衡为 -262.4 ± 7.8 g CO₂-C m⁻² year⁻¹，表明有 CO₂吸收，而 TS 接近中性（-28 ± 5.1 g CO₂-C m⁻² year⁻¹）。TS 处吸收量较小是由于生态系统呼吸作用较高（高 151%），而总初级生产力高 14%。然而，微地形对碳吸收的贡献差异很大：在 OS，丘和洼地都显示出净吸收，而在 TS，大部分碳（52%）被桦树同化，林下植被是净 CO₂源。这表明 TS 处泥炭碳流失，而成功重新湿润的站点正在积累新的泥炭。考虑样地尺度的 CH₄通量，两个站点都是温室气体的弱源，但 OS 处是明显更强的碳汇。我们的数据表明，通过完全重新湿润和建立特定泥炭地植被来增加从大气中去除碳的可能性。
