Myrstener Maria, Greenberg Larry A, Lidberg William, Kuglerová Lenka
Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
Department of Environmental and Life Sciences, Karlstad University, Karlstad, Sweden.
J Environ Manage. 2025 Apr;379:124740. doi: 10.1016/j.jenvman.2025.124740. Epub 2025 Mar 5.
Clear-cutting of forests with little or no regard for riparian buffers alters the local abiotic habitat of streams within and downstream of clear-cuts by increasing temperature, incident light, suspended sediments and resource inputs such as carbon and inorganic nutrients. It is also well documented that streams with narrow or non-existent riparian buffers affect local stream ecosystem processes. Here, we ask whether ecosystem processes can also be affected downstream of clear-cuts. We tested this in nine headwater streams that run through recently harvested clear-cuts (1-6 years ago) with varying buffer widths (<10 and ≥ 15 m) in northern Sweden. We compared biofilm (periphytic algal and bacterial mats) and whole stream metabolic rates in stream reaches situated upstream of the clear-cuts, in the clear-cuts and downstream of the clear-cuts. We found that biofilm gross primary productivity (GPP) in streams with thin buffers (<10 m) increased, on average, by 54 % downstream of clear-cuts in July, but that the net effect on the whole ecosystem was still a decrease in ecosystem productivity due to high respiration rates. In September, the situation was different as there was a 50 % decrease in biofilm GPP downstream of clear-cuts, and the net effect was again a decrease in ecosystem productivity. Wide buffer zones (>15 m) could mitigate these longitudinal changes for both biofilm and whole stream metabolism, except in one stream that was dominated by fine sediments. Importantly, the magnitude of downstream propagation in biofilm GPP was related to the magnitude of responses in the clear-cut, which in turn was driven by nutrient concentrations. To upscale the potential magnitude of clear-cutting in Sweden, we estimated that nearly 6 % (or 57,400 km) of the total forested stream length is situated within and 100 m downstream of clear-cuts that were harvested 1-6 years ago. Based on this study, we conclude that clear-cut effects on stream ecosystem processes are not only local, but can also be propagated to downstream recipient waters if riparian buffer width in the clear-cut is less than 15 m.
对森林进行皆伐时很少或根本不考虑河岸缓冲带，这会通过升高温度、增加入射光、增加悬浮沉积物以及增加碳和无机养分等资源输入，改变皆伐区域内及下游溪流的局部非生物栖息地。有充分记录表明，河岸缓冲带狭窄或不存在的溪流会影响当地溪流生态系统过程。在此，我们要问皆伐区域下游的生态系统过程是否也会受到影响。我们在瑞典北部九条流经最近（1至6年前）进行过皆伐且缓冲带宽度各异（<10米和≥15米）的源头溪流中对此进行了测试。我们比较了皆伐区域上游、皆伐区域内以及皆伐区域下游的河段中生物膜（附生藻类和细菌垫）和整个溪流的代谢率。我们发现，7月时，缓冲带较窄（<10米）的溪流中生物膜的总初级生产力（GPP）在皆伐区域下游平均增加了54%，但由于呼吸速率较高，对整个生态系统的净影响仍是生态系统生产力下降。9月时情况有所不同，皆伐区域下游生物膜GPP下降了50%，净影响同样是生态系统生产力下降。除了一条以细颗粒沉积物为主的溪流外，宽缓冲带（>15米）可以减轻生物膜和整个溪流代谢的这些纵向变化。重要的是，生物膜GPP下游传播的幅度与皆伐区域内响应的幅度相关，而皆伐区域内的响应幅度又受养分浓度驱动。为了估算瑞典皆伐的潜在规模，我们估计，在1至6年前进行皆伐的区域内及下游100米范围内，森林溪流总长度的近6%（或57,400千米）受到了影响。基于这项研究，我们得出结论，皆伐对溪流生态系统过程的影响不仅局限于局部，如果皆伐区域内的河岸缓冲带宽度小于15米，还会传播至下游的受纳水体。
