Gross primary productivity (GPP), the CO₂ uptake by means of photosynthesis, cannot be measured directly on the ecosystem scale but has to be inferred from proxies or models. One newly emerged proxy is the trace gas carbonyl sulfide (COS). COS diffuses into plant leaves in a fashion very similar to CO₂ but is generally not emitted by plants. Laboratory studies on leaf level gas exchange have shown promising correlations between the leaf relative uptake (LRU) of COS to CO₂ under controlled conditions. However, in situ measurements including daily to seasonal environmental changes are required to test the applicability of COS as a tracer for GPP at larger temporal scales. To this end, we conducted concurrent ecosystem-scale CO₂ and COS flux measurements above an agriculturally managed temperate mountain grassland. We also determined the magnitude and variability of the soil COS exchange, which can affect the LRU on an ecosystem level. The cutting and removal of the grass at the site had a major influence on the soil flux as well as the total exchange of COS. The grassland acted as a major sink for CO₂ and COS during periods of high leaf area. The sink strength decreased after the cuts, and the grassland turned into a net source for CO₂ and COS on an ecosystem level. The soil acted as a small sink for COS when the canopy was undisturbed but also turned into a source after the cuts, which we linked to higher incident radiation hitting the soil surface. However, the soil contribution was not large enough to explain the COS emission on an ecosystem level, hinting at an unknown COS source possibly related to dead plant matter degradation. Over the course of the season, we observed a concurrent decrease in CO₂ and COS uptake on an ecosystem level. With the exception of the short periods after the cuts, the LRU under high-light conditions was rather stable and indicated a high correlation between the COS flux and GPP across the growing season.

中文翻译：

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温带草地的COS和CO ₂交换的季节动态

总初级生产力（GPP），即通过光合作用吸收的CO ₂，不能直接在生态系统规模上进行测量，而必须从代理或模型中推断出来。一种新出现的替代物是痕量碳羰基硫（COS）。COS以与CO ₂非常相似的方式扩散到植物的叶子中，但通常不会被植物释放。叶片水平气体交换的实验室研究表明，COS的叶片相对吸收量（LRU）与CO ₂之间存在有希望的相关性在受控条件下。但是，需要进行包括每日到季节性环境变化在内的现场测量，以在更大的时间尺度上测试COS作为GPP示踪剂的适用性。为此，我们在农业管理的温带山区草原上同时进行了生态系统规模的CO ₂和COS通量测量。我们还确定了土壤COS交换的大小和变异性，这可以在生态系统水平上影响LRU。现场的割草和除草对土壤通量和COS的总交换有重要影响，草地是CO ₂的主要汇。叶面积高时的COS和COS。砍伐后汇聚强度下降，在生态系统水平上，草地变成了CO ₂和COS的净来源。当树冠不受干扰时，土壤充当了COS的小水池，但在割开后也变成了源，我们将其与入射到土壤表面的较高入射辐射联系起来。但是，土壤的贡献还不足以解释生态系统水平上的COS排放，暗示了未知的COS来源可能与死植物物质的降解有关。在整个季节中，我们观察到CO ₂同时减少和COS在生态系统水平上的吸收。除采伐后的短暂时间外，高光照条件下的LRU相当稳定，表明整个生长季节COS通量与GPP之间具有高度相关性。