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Microbial hydrogenation of cholesterol to coprostanol by anaerobic bacteria: evidence from Antarctic lacustrine sediment 厌氧细菌将胆固醇加氢转化为共烷醇的微生物作用:南极湖沼沉积物的证据
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-07-12 DOI: 10.1007/s10533-024-01121-7
Xin Chen, Jianjun Wang, Jing Jin, Yaguang Nie, Zhangqin Zheng, Yulu Xue, Weidong Kong, Wenhan Cheng, Jifeng Zhang, Lewen Liang, Yi Yang, Steven D. Emslie, Xiaodong Liu

Fecal sterols are traditionally ascribed as important biomarkers for animal excrement, and have been widely used to identify the source of organic matter and to reconstruct paleoecological changes in Antarctic terrestrial, aquatic, and marine ecosystems. However, the in situ microbial hydrogenation of cholesterol to coprostanol could have significance as a proxy to infer paleoenvironmental studies in Antarctica, particularly in anoxic sediment. Here, we report that abundant coprostanol, which was traditionally deemed as a biomarker for human sewage contamination, was found in three anoxic sediment profiles (AC2, BI, and CH1), which were strongly influenced by animal excrement at North Victoria Land, western Ross Sea, Antarctica. Our results suggest that the high concentrations of coprostanol in these three sediment profiles were not due to animal excrement, since coprostanol is not present in penguin guano and is a minor component in seal excrement. Coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) ratios suggest that coprostanol in the sediment cores of AC2 and BI was primarily derived from bacterial hydrogenation of cholesterol introduced by penguin guano. Coprostanol in CH1 sediments is related to human sewage due to intensive research activities from 1968 to 2006 in this region. However, the low abundance of coprostanol and the ratios of coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) in a relatively oxidizing sediment core (IIL1) infer that coprostanol was likely contributed by seal settlement. Together with high-throughput sequencing of the 16S rRNA gene, the conversion of cholesterol to coprostanol by anaerobic bacteria (e.g., Eubacterium coprostanoligenes) could occur in anoxic aquatic systems. Our results suggest that the presence of coprostanol in Antarctic lacustrine sediment with anoxic conditions does not necessarily indicate seal activity and human waste as the microbial hydrogenation of cholesterol to coprostanol should also be considered.

粪便固醇历来被认为是动物排泄物的重要生物标志物,并被广泛用于确定有机物质的来源和重建南极陆地、水生和海洋生态系统的古生态变化。然而,将胆固醇原位微生物氢化成共烷醇可能是推断南极古环境研究的重要替代物,尤其是在缺氧沉积物中。在这里,我们报告了在南极洲罗斯海西部北维多利亚陆地的三个缺氧沉积物剖面(AC2、BI 和 CH1)中发现的大量 coprostanol(传统上被认为是人类污水污染的生物标志物),这些剖面受到动物排泄物的强烈影响。我们的研究结果表明,这三个沉积物剖面中的高浓度 coprostanol 并不是动物排泄物造成的,因为 coprostanol 不存在于企鹅鸟粪中,在海豹排泄物中也是次要成分。谷甾醇/胆固醇和谷甾醇/(谷甾醇+胆甾醇)比率表明,AC2 和 BI 沉积物岩心中的谷甾醇主要来自细菌对企鹅粪便中胆固醇的氢化作用。由于 1968 年至 2006 年在该地区开展了大量研究活动,CH1 沉积物中的 coprostanol 与人类污水有关。然而,在一个相对氧化的沉积物岩心(IIL1)中,共聚谷固醇的丰度较低,而且共聚谷固醇/胆固醇和共聚谷固醇/(共聚谷固醇+胆甾醇)的比率也较低,因此推断共聚谷固醇很可能是海豹沉降造成的。结合 16S rRNA 基因的高通量测序,厌氧细菌(如 coprostanoligenes Eubacterium)将胆固醇转化为 coprostanol 的过程可能发生在缺氧的水生系统中。我们的研究结果表明,在缺氧条件下的南极湖沼沉积物中出现 coprostanol 并不一定表明存在海豹活动和人类排泄物,因为还应该考虑到微生物将胆固醇氢化为 coprostanol 的情况。
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引用次数: 0
Estimating the global root exudate carbon flux 估算全球根外渗碳通量
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-07-09 DOI: 10.1007/s10533-024-01161-z
Nikhil R. Chari, Shersingh Joseph Tumber-Dávila, Richard P. Phillips, Taryn L. Bauerle, Melanie Brunn, Benjamin D. Hafner, Tamir Klein, Sophie Obersteiner, Michaela K. Reay, Sami Ullah, Benton N. Taylor

Root exudation, the export of low-molecular weight organic carbon (C) from living plant roots to soil, influences microbial activity, nutrient availability, and ecosystem feedbacks to climate change, but the magnitude of this C flux at ecosystem and global scales is largely unknown. Here, we synthesize in situ measurements of root exudation rates and couple those to estimates of fine root biomass to estimate global and biome-level root exudate C fluxes. We estimate a global root exudate flux of 13.4 (10.1–20.2) Pg C y−1, or about 9% (7–14%) of global annual gross primary productivity. We did not find differences in root mass-specific exudation rates among biomes, though total exudate fluxes are estimated to be greatest in grasslands owing to their high density of absorptive root biomass. Our synthesis highlights the global importance of root exudates in the terrestrial C cycle and identifies regions where more in situ measurements are needed to improve future estimates of root exudate C fluxes.

根系渗出是低分子量有机碳(C)从活体植物根系向土壤的输出,它影响着微生物活动、养分供应和生态系统对气候变化的反馈,但这种碳通量在生态系统和全球尺度上的大小在很大程度上是未知的。在这里,我们综合了对根系渗出率的现场测量结果,并将其与细根生物量的估计值结合起来,以估算全球和生物组水平的根系渗出碳通量。我们估计全球根外渗通量为 13.4 (10.1-20.2) Pg C y-1,约占全球年总初级生产力的 9% (7-14%)。我们没有发现不同生物群落的根系特定渗出率存在差异,但由于草地吸收性根系生物量密度高,估计草地的总渗出通量最大。我们的综述强调了根系渗出物在陆地碳循环中的全球重要性,并确定了需要进行更多现场测量的区域,以改进未来对根系渗出物碳通量的估计。
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引用次数: 0
Dissolved organic matter released from beach wrack is source-specific and molecularly highly diverse 海滩滩涂释放的溶解有机物具有来源特异性和分子高度多样性
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-07-09 DOI: 10.1007/s10533-024-01159-7
Hannelore Waska, Hanne M. Banko-Kubis

Beach wrack is an important supplier of nutrients and organic matter to sandy beach ecosystems and underlying subterranean estuaries (STEs), producing metabolic hotspots in these otherwise organic carbon- and nutrient-poor environments. To assess the impact of beach wrack type (e.g., marine, terrestrial, plant, animal) and environmental settings (e.g., tidal inundation, precipitation, and solar irradiation) on nutrient and dissolved organic matter (DOM) release, a series of leaching experiments was conducted. Quantities of leached nutrients and dissolved organic carbon (DOC) were determined, and DOM molecular composition was investigated using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Millimolar—to molar amounts of DOC and dissolved nitrogen were released from the beach cast per kg dry weight, with type of wrack and leaching medium (fresh- vs. saltwater) exerting the biggest influences. Exemplary for animal cast, jellyfish leached up to two 100-fold more, mostly organic, nitrogen compared to all other beach wrack types. FT-ICR-MS data of solid-phase extracted DOM indicated that beach wrack releases compounds with putative mono- and oligosaccharide-, amino acid- and vitamin-type molecular formulae, which likely serve as valuable substrate for heterotrophic microorganisms. DOM from the brown seaweed Fucus sp. was more aromatic than seawater DOM and even beach wrack of terrestrial origin, probably from structural components and secondary metabolites such as phlorotannins. We conclude that DOM and nutrient release from beach wrack strongly depends on wrack type and leaching medium, may obscure molecular provenance proxies (e.g., terrestrial indices), and adds a nutritional boost to infiltrating sea- and rainwater which likely impact microbial respiration rates in the STE.

海滩裹挟物是沙滩生态系统和地下河口(STEs)的重要营养物质和有机物质供应者,在这些原本缺乏有机碳和营养物质的环境中产生新陈代谢热点。为了评估海滩褶皱类型(如海洋、陆地、植物、动物)和环境背景(如潮汐淹没、降水和太阳辐射)对养分和溶解有机物(DOM)释放的影响,进行了一系列浸出实验。测定了浸出养分和溶解有机碳(DOC)的数量,并使用傅立叶变换离子回旋共振质谱法(FT-ICR-MS)研究了 DOM 的分子组成。每千克干重的海滩弃置物释放出的 DOC 和溶解氮的摩尔至摩尔量,对其影响最大的是栅栏类型和沥滤介质(淡水和海水)。与其他所有类型的海滩缠绕物相比,水母沥滤的动物粪便中的氮含量(主要是有机氮)要高出两倍到 100 倍。固相萃取 DOM 的 FT-ICR-MS 数据表明,海滩鞭痕释放出的化合物具有假定的单糖和寡糖、氨基酸和维生素类分子式,这些化合物可能是异养微生物的宝贵底物。褐藻 Fucus sp.产生的 DOM 比海水 DOM 甚至是陆源海滩栅栏产生的 DOM 更芳香,这可能是结构成分和次生代谢物(如绿单宁)的作用。我们的结论是,海滩栅栏释放的 DOM 和营养物质在很大程度上取决于栅栏类型和沥滤介质,可能会掩盖分子来源代用指标(如陆地指数),并为渗入的海水和雨水增加营养,这可能会影响 STE 中的微生物呼吸速率。
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引用次数: 0
Correction to: Simulated plant-mediated oxygen input has strong impacts on fine-scale porewater biogeochemistry and weak impacts on integrated methane fluxes in coastal wetlands 更正:模拟植物介导的氧气输入对沿岸湿地细尺度孔隙水生物地球化学的影响很大,而对综合甲烷通量的影响较小
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-06-28 DOI: 10.1007/s10533-024-01155-x
Yongli Zhou, Teri O’Meara, Zoe G. Cardon, Jiaze Wang, Benjamin N. Sulman, Anne E. Giblin, Inke Forbrich
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引用次数: 0
Groundwater seeps are hot spots of denitrification and N2O emissions in a restored wetland 地下水渗漏是恢复湿地中反硝化和一氧化二氮排放的热点
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-06-27 DOI: 10.1007/s10533-024-01156-w
Sarah M. Klionsky, Christopher Neill, Ashley M. Helton, Beth Lawrence

Restorations of former cranberry farms (“bogs”) aim to re-establish native wetland vegetation, promote cold water habitat, and attenuate nitrogen (N) delivery to coastal waters. It is unclear, though, how elements of restoration design such as microtopography, groundwater interception, and plant communities affect N removal via denitrification. In a recently restored riparian cranberry bog with created microtopography, we compared denitrification potential, nitrous oxide (N2O) yield of denitrification (ratio of N2O:N2O + N2 gases), in situ N2O fluxes, soil chemistry, and plant communities at the highest and lowest elevations within 20 plots and at four side-channel groundwater seeps. Denitrification potential was > 2 × greater at low elevations, which had plant communities distinct from high elevations, and was positively correlated with plant species richness (Spearman’s rho = 0.43). Despite detecting high N2O yield (0.86 ± 0.16) from low elevation soils, we observed small N2O emissions in situ, suggesting minimal incomplete denitrification even in saturated depressions. Groundwater seeps had an order of magnitude higher denitrification potentials and 100–300 × greater soil NO3− concentrations than the typically saturated low elevation soils. Groundwater seeps also had high N2O yield (1.05 ± 0.15) and higher, but spatially variable, in situ N2O emissions. Our results indicate that N removal is concentrated where soils interact with NO3–rich groundwater, but other factors such as low soil carbon (C) also limit denitrification. Designing restoration features to increase groundwater residence time, particularly in low lying, species rich areas, may promote more N attenuation in restored cranberry bogs and other herbaceous riparian wetlands.

对前蔓越莓农场("沼泽")进行修复的目的是重建原生湿地植被,促进冷水生境,并减少向沿岸水域输送氮(N)。不过,目前还不清楚微地形、地下水截流和植物群落等恢复设计要素如何通过反硝化作用影响氮的去除。在最近修复的河岸蔓越莓沼泽中,我们比较了 20 个地块中最高和最低海拔处以及四个侧通道地下水渗漏处的反硝化潜力、反硝化产生的一氧化二氮(N2O)(N2O:N2O + N2 气体的比率)、原位 N2O 通量、土壤化学和植物群落。低海拔地区的反硝化潜力是高海拔地区的 2 倍,其植物群落与高海拔地区不同,并且与植物物种丰富度呈正相关(Spearman's rho = 0.43)。尽管在低海拔土壤中检测到了较高的一氧化二氮产量(0.86 ± 0.16),但我们观察到的原位一氧化二氮排放量很小,这表明即使在饱和洼地中,不完全反硝化作用也很小。与典型的饱和低海拔土壤相比,地下水渗流的反硝化潜力高出一个数量级,土壤中的 NO3- 浓度也高出 100-300 倍。地下水渗流的氧化亚氮产量也很高(1.05 ± 0.15),原地氧化亚氮排放量也较高,但在空间上存在差异。我们的研究结果表明,脱氮作用主要集中在土壤与富含 NO3 的地下水相互作用的地方,但其他因素(如土壤碳(C)含量低)也限制了脱氮作用。设计恢复特征以增加地下水的停留时间,尤其是在低洼、物种丰富的区域,可能会促进恢复后的蔓越莓沼泽和其他草本河岸湿地中更多的氮衰减。
{"title":"Groundwater seeps are hot spots of denitrification and N2O emissions in a restored wetland","authors":"Sarah M. Klionsky,&nbsp;Christopher Neill,&nbsp;Ashley M. Helton,&nbsp;Beth Lawrence","doi":"10.1007/s10533-024-01156-w","DOIUrl":"10.1007/s10533-024-01156-w","url":null,"abstract":"<div><p>Restorations of former cranberry farms (“bogs”) aim to re-establish native wetland vegetation, promote cold water habitat, and attenuate nitrogen (N) delivery to coastal waters. It is unclear, though, how elements of restoration design such as microtopography, groundwater interception, and plant communities affect N removal via denitrification. In a recently restored riparian cranberry bog with created microtopography, we compared denitrification potential, nitrous oxide (N<sub>2</sub>O) yield of denitrification (ratio of N<sub>2</sub>O:N<sub>2</sub>O + N<sub>2</sub> gases), in situ N<sub>2</sub>O fluxes, soil chemistry, and plant communities at the highest and lowest elevations within 20 plots and at four side-channel groundwater seeps. Denitrification potential was &gt; 2 × greater at low elevations, which had plant communities distinct from high elevations, and was positively correlated with plant species richness (Spearman’s rho = 0.43). Despite detecting high N<sub>2</sub>O yield (0.86 ± 0.16) from low elevation soils, we observed small N<sub>2</sub>O emissions in situ, suggesting minimal incomplete denitrification even in saturated depressions. Groundwater seeps had an order of magnitude higher denitrification potentials and 100–300 × greater soil NO<sub>3</sub>− concentrations than the typically saturated low elevation soils. Groundwater seeps also had high N<sub>2</sub>O yield (1.05 ± 0.15) and higher, but spatially variable, in situ N<sub>2</sub>O emissions. Our results indicate that N removal is concentrated where soils interact with NO<sub>3</sub>–rich groundwater, but other factors such as low soil carbon (C) also limit denitrification. Designing restoration features to increase groundwater residence time, particularly in low lying, species rich areas, may promote more N attenuation in restored cranberry bogs and other herbaceous riparian wetlands.</p></div>","PeriodicalId":8901,"journal":{"name":"Biogeochemistry","volume":"167 8","pages":"1041 - 1056"},"PeriodicalIF":3.9,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10533-024-01156-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141461987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Stemflow dissolved organic matter in mixed temperate forests: temporal and interspecific variation of optical indices and development of a stemflow-specific PARAFAC model 温带混交林中茎流溶解的有机物:光学指数的时间和种间变化以及针对茎流的 PARAFAC 模型的开发
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-06-21 DOI: 10.1007/s10533-024-01158-8
Robyn C. O’Halloran, Jennifer J. Guerard, Delphis F. Levia

Stemflow is a conduit for the transport of canopy-derived dissolved organic matter (DOM) to the forest floor. This study examined the character of stemflow DOM for four tree species over four phenophases (leafless, emergence, leafed, and senescence for deciduous species and leafed-winter, emergence, leafed- spring/summer, and senescence for coniferous species) occurring in temperate forests; namely, Betula lenta L. (sweet birch), Fagus grandifolia Ehrh. (American beech), Liriodendron tulipifera L. (yellow poplar), and Pinus rigida Mill. (pitch pine). American beech exhibited the lowest average specific UV absorbance at 254 nm (SUVA254) values, while yellow poplar displayed the highest values. SUVA254 values were largest in senescence and smallest in emergence. The spectral slope ratio was lower for pitch pine than the deciduous tree species. Humification index (HIX) values decreased across all species during the emergence phenophase. The developed and validated stemflow-specific four-component parallel factor analysis (PARAFAC) model demonstrated the combined influence of interspecific and temporal fluctuations on the composition of humic and protein-like substances within stemflow. By separating and examining stemflow DOM independent of throughfall, our study provides fresh insights into the spatiotemporal dynamics of stemflow inputs to near-trunk soils that may inform hot spots and hot moments theories.

茎流是将树冠衍生的溶解有机物(DOM)输送到林地的通道。本研究考察了温带森林中四种树种在四个物候期(落叶树种的无叶期、萌芽期、落叶期和衰老期,针叶树种的冬季落叶期、萌芽期、春夏落叶期和衰老期)茎流溶解有机物的特征,这四种树种是甜桦树(Betula lenta L.)、美洲山毛榉(Fagus grandifolia Ehrh.(美国山毛榉)、Liriodendron tulipifera L.(黄杨)和 Pinus rigida Mill.(沥青松)。美国山毛榉在 254 纳米波长下的平均紫外线吸收比值(SUVA254)最低,而黄杨的吸收比值最高。衰老期的 SUVA254 值最大,萌发期最小。沥青松的光谱斜率比落叶树种低。在萌发阶段,所有树种的湿度指数(HIX)值都有所下降。开发和验证的茎流特定四成分平行因子分析(PARAFAC)模型表明,茎流中腐殖质和类蛋白物质的组成受到了种间波动和时间波动的综合影响。通过分离和检验独立于直流降水的茎流DOM,我们的研究为茎流输入近树干土壤的时空动态提供了新的见解,为热点和热点时刻理论提供了参考。
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引用次数: 0
Subtropical stormwater ponds are more frequently net nitrogen fixing compared to natural ponds 与自然池塘相比,亚热带雨水池塘更经常地净固氮
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-06-13 DOI: 10.1007/s10533-024-01153-z
Audrey H. Goeckner, Ashley R. Smyth, Meredith A. Holgerson, Alexander J. Reisinger

Urban stormwater ponds (SWPs) are engineered ecosystems designed to prevent flooding and protect downstream ecosystems by retaining nutrients associated with stormwater runoff, including nitrogen (N). Despite these expectations, multiple studies have found that SWPs have low N removal efficiencies and can be sources of N to downstream ecosystems. To understand mechanisms controlling the fate of N in SWPs, we quantified dinitrogen (N2) gas saturation to characterize net N2 exchange as either net denitrification or net N-fixation. We assessed temporal and spatial patterns of N2 dynamics in fifteen SWPs and six naturally occurring ponds in undisturbed watersheds (Florida, USA) by sampling in two seasons (dry and wet) and from multiple depths of the water column. Samples from SWPs were equally likely to exhibit N2 supersaturation (net denitrification; 50%) or undersaturation (net N-fixation; 50%). In contrast, the majority (82%) of samples from natural ponds were supersaturated with N2, indicating net denitrification. The mean SWP air–water N2 flux was − 1.7 μg N2-N m−2 h−1 (range − 500 to 433 μg N2-N m−2 h−1), which was lower than clear (40 μg N2-N m−2 h−1; range − 68 to 74 μg N2-N m−2 h−1) and humic (202 μg N2-N m−2 h−1; range 41 to 407 μg N2-N m−2 h−1) natural ponds despite considerably higher variation in SWPs. These results indicate that SWPs may have low N removal efficiencies in part due to N-fixation adding new N to the system. Overall, this study shows that SWPs are less effective than natural ponds at removing reactive N from the environment, potentially impacting downstream water quality.

城市雨水池塘(SWPs)是一种工程生态系统,旨在通过截留与雨水径流相关的营养物质(包括氮)来防止洪水并保护下游生态系统。尽管人们有这样的期望,但多项研究发现,蓄水池对氮的去除效率很低,可能成为下游生态系统的氮源。为了了解控制降水自动处理系统中氮的归宿的机制,我们对二氮(N2)气体饱和度进行了量化,以确定净 N2 交换的特征是净反硝化还是净固氮。我们在两个季节(旱季和雨季)并从水体的多个深度取样,评估了未受干扰流域(美国佛罗里达州)中 15 个 SWPs 和 6 个天然池塘的 N2 动态时空模式。来自 SWP 的样本同样有可能出现 N2 过饱和(净反硝化;50%)或欠饱和(净固氮;50%)现象。相比之下,来自天然池塘的大多数样本(82%)都出现了 N2 过饱和状态,表明出现了净反硝化作用。平均 SWP 空气-水 N2 通量为 - 1.7 μg N2-N m-2 h-1(范围 - 500 至 433 μg N2-N m-2 h-1),低于清澈池塘(40 μg N2-N m-2 h-1;范围 - 68 至 74 μg N2-N m-2 h-1)和腐殖质池塘(202 μg N2-N m-2 h-1;范围 41 至 407 μg N2-N m-2 h-1),尽管 SWP 的变化要大得多。这些结果表明,部分由于固氮作用给系统增加了新的氮,全合成池的氮去除效率可能较低。总之,这项研究表明,在从环境中去除活性氮方面,全合成池的效率低于天然池塘,可能会影响下游水质。
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引用次数: 0
Persistent and lagged effects of fire on stream solutes linked to intermittent precipitation in arid lands 火灾对与干旱地区间歇性降水有关的溪流溶质的持续和滞后影响
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-06-07 DOI: 10.1007/s10533-024-01154-y
Heili Lowman, Joanna Blaszczak, Ashley Cale, Xiaoli Dong, Stevan Earl, Julia Grabow, Nancy B. Grimm, Tamara K. Harms, John Melack, Ann Marie Reinhold, Betsy Summers, Alex J. Webster

Increased occurrence, size, and intensity of fire result in significant but variable changes to hydrology and material retention in watersheds with concomitant effects on stream biogeochemistry. In arid regions, seasonal and episodic precipitation results in intermittency in flows connecting watersheds to recipient streams that can delay the effects of fire on stream chemistry. We investigated how the spatial extent of fire within watersheds interacts with variability in amount and timing of precipitation to influence stream chemistry of three forested, montane watersheds in a monsoonal climate and four coastal, chaparral watersheds in a Mediterranean climate. We applied state-space models to estimate effects of precipitation, fire, and their interaction on stream chemistry up to five years following fire using 15 + years of monthly observations. Precipitation alone diluted specific conductance and flushed nitrate and phosphate to Mediterranean streams. Fire had positive and negative effects on specific conductance in both climates, whereas ammonium and nitrate concentrations increased following fire in Mediterranean streams. Fire and precipitation had positive interactive effects on specific conductance in monsoonal streams and on ammonium in Mediterranean streams. In most cases, the effects of fire and its interaction with precipitation persisted or were lagged 2–5 years. These results suggest that precipitation influences the timing and intensity of the effects of fire on stream solute dynamics in aridland watersheds, but these responses vary by climate, solute, and watershed characteristics. Time series models were applied to data from long-term monitoring that included observations before and after fire, yielding estimated effects of fire on aridland stream chemistry. This statistical approach captured effects of local-scale temporal variation, including delayed responses to fire, and may be used to reduce uncertainty in predicted responses of water quality under changing fire and precipitation regimes of arid lands.

火灾发生率、规模和强度的增加会导致流域的水文和物质滞留发生重大但多变的变化,同时对溪流的生物地球化学产生影响。在干旱地区,季节性和偶发性降水会导致连接流域和受水区溪流的水流时断时续,从而延迟火灾对溪流化学的影响。我们研究了流域内火灾的空间范围如何与降水量和降水时间的变化相互作用,从而影响季风气候下三个山地森林流域和地中海气候下四个沿海荒漠流域的溪流化学。我们利用状态空间模型,通过 15 年以上的月度观测,估算了降水、火灾及其相互作用对火灾后五年内溪流化学的影响。降水本身稀释了比电导率,并将硝酸盐和磷酸盐冲入地中海溪流。在两种气候条件下,火灾对比电导率都有积极和消极的影响,而在地中海溪流中,火灾后铵盐和硝酸盐的浓度都有所增加。火灾和降水对季风溪流的比电导率和地中海溪流的铵有积极的交互影响。在大多数情况下,火灾及其与降水的交互作用会持续或滞后 2-5 年。这些结果表明,降水会影响火灾对干旱地区流域溪流溶质动态影响的时间和强度,但这些反应因气候、溶质和流域特征而异。时间序列模型被应用于包括火灾前后观测数据在内的长期监测数据,从而估算出火灾对干旱地区溪流化学的影响。这种统计方法捕捉到了地方尺度时间变化的影响,包括对火灾的延迟反应,可用于减少在干旱地区火灾和降水变化情况下预测水质反应的不确定性。
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引用次数: 0
Rewetting effects on nitrogen cycling and nutrient export from coastal peatlands to the Baltic Sea 复湿对沿岸泥炭地向波罗的海的氮循环和养分输出的影响
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-06-05 DOI: 10.1007/s10533-024-01149-9
Anne Breznikar, Daniel L. Pönisch, Marvin Lorenz, Gerald Jurasinski, Gregor Rehder, Maren Voss

Coastal nutrient loads from point sources such as rivers are mostly well-monitored. This is not the case for diffuse nutrient inputs from coastal catchments unconnected to rivers, despite the potential for high inputs due to intensive land use. The German Baltic Sea coastline consists of numerous peatlands that have been diked and drained. However, some of the dikes have been removed in order to re-establish the hydrological connection to the Baltic Sea, restore local biodiversity, and promote natural CO2 uptake. Since these peatlands were used for agriculture, their rewetting may release accumulated nutrients, leading to nutrient export into the Baltic Sea and intensified coastal eutrophication. Data on these potential nutrient exports are mostly lacking. Therefore, this study investigated nutrient exports from two former agricultural, coastal peatlands: Drammendorfer Wiesen, rewetted in 2019, and Karrendorfer Wiesen, rewetted in 1993. Nutrients (NO3, NO2, NH4+, PO43–), nitrous oxide (N2O), particulate organic matter (POM, comprising POC and PON; δ13C-POC), chlorophyll-a, and nitrification rates were analyzed in surface water and porewater sampled weekly to monthly in 2019 and 2020 to compare the effects of different time scales after rewetting on nutrient cycling and potential exports. NH4+, NO2, and PO43− concentrations were higher in the porewater than in the overlying water at both sites, while nutrient concentrations were generally higher at the recently rewetted Drammendorfer Wiesen than at the Karrendorfer Wiesen. NO3 concentrations in porewater, however, were lower than in the overlying water, indicating NO3 retention within the peat, likely due to denitrification. Nitrification rates and N2O concentrations were generally low, except for a high N2O peak immediately after rewetting. These results suggest that denitrification was the dominant process of N2O production at the study sites. Both peatlands exported nutrients to their adjacent bays of the Baltic Sea; however, N exports were 75% lower in the longer-rewetted peatland. Compared to major Baltic Sea rivers, both sites exported larger area-normalized nutrient loads. Our study highlights the need to monitor the impact of rewetting measures over time to obtain accurate estimates of nutrient exports, better assess negative effects on coastal waters, and to improve peatland management.

来自河流等点源的沿岸营养盐负荷大多得到了很好的监测。但来自与河流不相连的沿海集水区的扩散营养盐输入却不是这样,尽管集约化的土地利用可能会导致大量的营养盐输入。德国波罗的海沿岸有许多泥炭地,这些泥炭地已被围堤和排水。不过,为了重建与波罗的海的水文联系、恢复当地的生物多样性并促进二氧化碳的自然吸收,部分堤坝已被拆除。由于这些泥炭地曾被用于农业,它们的复湿可能会释放出累积的营养物质,导致营养物质向波罗的海输出并加剧沿岸富营养化。有关这些潜在养分输出的数据大多缺乏。因此,本研究调查了两个前农用沿海泥炭地的养分输出情况:Drammendorfer Wiesen 于 2019 年复湿,Karrendorfer Wiesen 于 1993 年复湿。分析了2019年和2020年每周至每月采样的地表水和孔隙水中的养分(NO3-、NO2-、NH4+、PO43-)、一氧化二氮(N2O)、颗粒有机物(POM,包括POC和PON;δ13C-POC)、叶绿素-a和硝化率,以比较复湿后不同时间尺度对养分循环和潜在输出的影响。在这两个地点,孔隙水中的 NH4+、NO2- 和 PO43- 浓度均高于上层水,而最近复湿的 Drammendorfer Wiesen 的养分浓度普遍高于 Karrendorfer Wiesen。不过,孔隙水中的 NO3- 浓度低于上覆水中的 NO3-浓度,这表明泥炭中 NO3- 的保留可能是由于反硝化作用造成的。硝化率和一氧化二氮浓度普遍较低,只是在复湿后立即出现了一个较高的一氧化二氮峰值。这些结果表明,反硝化作用是研究地点产生 N2O 的主要过程。两块泥炭地都向波罗的海的邻近海湾输出营养物质;但是,复湿时间较长的泥炭地的氮输出量要低 75%。与波罗的海的主要河流相比,这两个地点输出的面积归一化营养负荷更大。我们的研究突出表明,有必要对复湿措施的影响进行长期监测,以获得营养物质输出的准确估计值,更好地评估对沿岸水域的负面影响,并改善泥炭地管理。
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引用次数: 0
Simulated plant-mediated oxygen input has strong impacts on fine-scale porewater biogeochemistry and weak impacts on integrated methane fluxes in coastal wetlands 模拟植物介导的氧气输入对沿海湿地细尺度孔隙水生物地球化学的影响很大,而对综合甲烷通量的影响较小
IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Pub Date : 2024-05-23 DOI: 10.1007/s10533-024-01145-z
Yongli Zhou, Teri O’Meara, Zoe G. Cardon, Jiaze Wang, Benjamin N. Sulman, Anne E. Giblin, Inke Forbrich

Methane (CH4) emissions from wetland ecosystems are controlled by redox conditions in the soil, which are currently underrepresented in Earth system models. Plant-mediated radial oxygen loss (ROL) can increase soil O2 availability, affect local redox conditions, and cause heterogeneous distribution of redox-sensitive chemical species at the root scale, which would affect CH4 emissions integrated over larger scales. In this study, we used a subsurface geochemical simulator (PFLOTRAN) to quantify the effects of incorporating either spatially homogeneous ROL or more complex heterogeneous ROL on model predictions of porewater solute concentration depth profiles (dissolved organic carbon, methane, sulfate, sulfide) and column integrated CH4 fluxes for a tidal coastal wetland. From the heterogeneous ROL simulation, we obtained 18% higher column averaged CH4 concentration at the rooting zone but 5% lower total CH4 flux compared to simulations of the homogeneous ROL or without ROL. This difference is because lower CH4 concentrations occurred in the same rhizosphere volume that was directly connected with plant-mediated transport of CH4 from the rooting zone to the atmosphere. Sensitivity analysis indicated that the impacts of heterogeneous ROL on model predictions of porewater oxygen and sulfide concentrations will be more important under conditions of higher ROL fluxes or more heterogeneous root distribution (lower root densities). Despite the small impact on predicted CH4 emissions, the simulated ROL drastically reduced porewater concentrations of sulfide, an effective phytotoxin, indicating that incorporating ROL combined with sulfur cycling into ecosystem models could potentially improve predictions of plant productivity in coastal wetland ecosystems.

湿地生态系统的甲烷(CH4)排放受土壤氧化还原条件的控制,而目前地球系统模型中对氧化还原条件的反映不足。植物介导的径向氧损失(ROL)可增加土壤中氧气的可用性,影响局部氧化还原条件,并导致对氧化还原敏感的化学物种在根系尺度上的异质分布,这将影响更大尺度上的综合 CH4 排放。在这项研究中,我们使用了一种地下地球化学模拟器(PFLOTRAN),以量化加入空间均质 ROL 或更复杂的异质 ROL 对潮汐沿岸湿地的孔隙水溶质浓度深度剖面(溶解有机碳、甲烷、硫酸盐、硫化物)和柱状综合 CH4 通量模型预测的影响。与同质 ROL 模拟或无 ROL 模拟相比,通过异质 ROL 模拟,根区的柱平均甲烷浓度提高了 18%,但甲烷总通量却降低了 5%。出现这种差异的原因是,在与植物介导的从生根区到大气的甲烷迁移直接相关的同一根圈体积中,甲烷浓度较低。敏感性分析表明,在 ROL 通量较高或根系分布较不均匀(根系密度较低)的条件下,异质性 ROL 对模型预测的孔隙水氧气和硫化物浓度的影响会更大。尽管对预测的甲烷排放量影响较小,但模拟的 ROL 却大大降低了硫化物(一种有效的植物毒素)在孔隙水中的浓度,这表明将 ROL 与硫循环结合到生态系统模型中,有可能改善对沿岸湿地生态系统中植物生产力的预测。
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引用次数: 0
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Biogeochemistry
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