Clasen Lina Avila, Alvarenga Danillo Oliveira, Wang Yinliu, Andersen Rune Fromm, Rousk Kathrin
Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark.
Center for Volatile Interactions, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark.
Biogeochemistry. 2025;168(1):12. doi: 10.1007/s10533-024-01195-3. Epub 2025 Jan 4.
Nitrogen (N) fixation in association with mosses could be a key source of new N in tropical montane cloud forests since these forests maintain high humidity levels and stable temperatures, both of which are important to N fixation. Here, nutrient availability could be a prominent control of N fixation processes. However, the mechanisms and extent of these controls, particularly in forests at different successional stages, remains unknown to date. To address this knowledge gap, we investigated the impact of N, phosphorus (P) and molybdenum (Mo) additions on moss-associated N fixation in tropical montane cloud forests of two successional stages, an old-growth forest and an early-successional natural regrowth forest. We hypothesized that if N is available, N fixation rates would be rapidly reduced, while P and Mo would promote nitrogenase activity. Our results show that Mo additions did not affect N fixation rates, whereas N and P additions, in different doses and combinations, immediately reduced N fixation in both forests. Nonetheless, rates recovered within 1 year of nutrient additions. Nitrogen fixation rates associated with ground-covering mosses were similar in both forests. Interestingly, one year after the nutrient additions, N fixation rates across all the treatments were higher in the natural regrowth forests than the mature forests, suggesting more nutrient limitation in these regrowing forests, likely as a result of higher demand for growth. Our study highlights how moss-associated N fixation responds to changes in nutrient availability across distinct successional stages, deepening our understanding of processes that contributes to tropical montane cloud forests.
The online version contains supplementary material available at 10.1007/s10533-024-01195-3.
与苔藓相关的固氮作用可能是热带山地云雾森林新氮的关键来源，因为这些森林保持着高湿度水平和稳定的温度，这两者对固氮作用都很重要。在这里，养分有效性可能是固氮过程的一个重要控制因素。然而，这些控制的机制和程度，特别是在不同演替阶段的森林中，迄今为止仍然未知。为了填补这一知识空白，我们研究了添加氮（N）、磷（P）和钼（Mo）对两个演替阶段的热带山地云雾森林中与苔藓相关的固氮作用的影响，这两个阶段分别是老龄森林和早期演替的自然再生林。我们假设，如果有氮可用，固氮率将迅速降低，而磷和钼将促进固氮酶活性。我们的结果表明，添加钼不会影响固氮率，而不同剂量和组合的氮和磷添加会立即降低两个森林中的固氮作用。尽管如此，在添加养分后的1年内，固氮率恢复了。两个森林中与地被苔藓相关的固氮率相似。有趣的是，在添加养分一年后，自然再生林中所有处理的固氮率都高于成熟林，这表明这些再生林中养分限制更大，可能是由于生长需求更高。我们的研究突出了与苔藓相关的固氮作用如何响应不同演替阶段养分有效性的变化，加深了我们对热带山地云雾森林形成过程的理解。
在线版本包含可在10.1007/s10533-024-01195-3获取的补充材料。
