IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2026-01-02 DOI: 10.1016/j.catena.2025.109775

Wenjing Fang , Xinrui Wang , Bingzhu Chen , Yuting Liu , Qin Huang , Zhiyan Peng , Rujing Yang , Qiong Cai , Suhui Ma , Zhiming Zhang , Jingyun Fang

Forest line is one of the hot spots in ecological research. It is well documented that the dynamics of forest line under climatic warming, yet how soil microbial community composition shifts across forest line ecotone remains unclear. This study investigated the change in microbial communities of rhizosphere and bulk soils at locations above, at, and below the forest line within an alpine forest-shrubland ecotone in the Hengduan Mountains, China. The results showed that the relative abundances of dominant phyla in surface rhizosphere soil changed more significantly along the forest line ecotone, with Proteobacteria and Basidiomycota decreasing but Chloroflexi and Mortierellomycota increasing, compared to bulk soil. Both the network complexity and key nodes of soil microbial communities changed significantly along the forest line ecotone. Specifically, bacterial network complexity between rhizosphere and bulk soils depended on soil depth, whereas fungal network complexity between rhizosphere and bulk soils varied with forest line. Microbial community compositions were co-regulated by both environmental and vegetation factors. Furthermore, microbial community changes were primarily driven by the cover and height of shrub and herb layers, highlighting the importance of shrubs and herbs in shaping soil microbial community composition. Our findings reveal the distribution patterns and underlying shift mechanisms of microbial communities along the forest line ecotone. These insights are crucial for mountain biodiversity conservation and for improving predictions of forest responses to climate change.

森林线是生态学研究的热点之一。气候变暖条件下森林线的动态变化已经得到了充分的研究，但土壤微生物群落组成如何在森林线交错带上发生变化仍不清楚。研究了横断山高寒森林-灌丛交错带林线以上、林线以下根际土壤和块状土壤微生物群落的变化。结果表明：根际表层土壤优势门相对丰度沿林线交错带变化显著，变形菌门和担子菌门相对减少，绿菌门和Mortierellomycota相对增加；沿林线交错带，土壤微生物群落的网络复杂性和关键节点都发生了显著变化。其中，根际土壤与土体之间的细菌网络复杂性与土壤深度有关，而根际土壤与土体之间的真菌网络复杂性随林线变化而变化。微生物群落组成受环境因子和植被因子共同调控。土壤微生物群落的变化主要受灌草层盖度和高度的影响，说明灌草层在土壤微生物群落组成中的重要作用。我们的发现揭示了沿森林线交错带微生物群落的分布模式和潜在的转移机制。这些见解对于保护山地生物多样性和改进森林对气候变化的反应预测至关重要。

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引用次数: 0

Synergistic effects of drip irrigation and vegetation on the stability of biochar-stabilized expansive soil slopes 滴灌与植被对生物炭稳定膨胀土边坡稳定性的协同效应

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2026-01-02 DOI: 10.1016/j.catena.2025.109761

Mingjie Jiang , Chongzhan Lu , Ming Wang , Guoxiong Mei , Ankit Garg

Existing studies have demonstrated that cracking is a fundamental cause of soil slope instability, while uneven water evaporation is the primary factor contributing to crack development. Appropriate moisture management measures can effectively reduce cracking risks. Therefore, investigating the mechanisms by which drip irrigation technology and vegetation influence expansive soil slopes holds significant theoretical and engineering importance. This study established four slope models: Biochar-Amended Expansive Soil Slope (BAES), Drip-Irrigated Biochar-Amended Expansive Soil Slope (DI-BAES), Vegetated Biochar-Amended Expansive Soil Slope (V-BAES), and Drip-Irrigated Vegetated Biochar-Amended Expansive Soil Slope (DI-V-BAES). An outdoor slope model box test was conducted over an entire summer season (100 days) to examine the effects of drip irrigation and vegetation on shallow stability of biochar-amended expansive soil slopes. Results show that drip irrigation and vegetation significantly impact the shallow stability. The drip irrigation system effectively maintains slope soil moisture through continuous water supply, thereby reducing soil drying and crack formation. Vegetation substantially improves soil shear strength, reduces soil scouring, and enhances erosion resistance through root reinforcement and canopy coverage. The combination of both measures further optimizes slope stability, with the DI-V-BAES model demonstrating the best performance in maintaining temperature stability, moisture content stability, reducing fissure rates, and improving scour resistance. This approach significantly enhances the overall stability and erosion resistance of expansive soil slopes, representing an effective measure for long-term slope stability. Additionally, drip irrigation promotes vegetation growth, increasing root density and slope-holding capacity, while vegetation improves soil cohesion and internal friction angle through root system development. In conclusion, the synergistic management model of drip irrigation and vegetation provides theoretical foundations and practical guidance for expansive soil slope protection.

已有研究表明，裂缝是土质边坡失稳的根本原因，而水分蒸发不均匀是导致裂缝发展的主要因素。适当的水分管理措施可有效降低开裂风险。因此，研究滴灌技术和植被对膨胀土边坡的影响机制具有重要的理论和工程意义。建立了四种边坡模型：生物炭修正膨胀土边坡（BAES）、滴灌生物炭修正膨胀土边坡（DI-BAES）、植被生物炭修正膨胀土边坡（V-BAES）和滴灌植被生物炭修正膨胀土边坡（DI-V-BAES）。通过整个夏季（100天）的室外斜坡模型箱试验，研究了滴灌和植被对生物炭改性膨胀土斜坡浅稳定性的影响。结果表明，滴灌和植被对浅层稳定性影响显著。滴灌系统通过连续供水有效地保持坡面土壤水分，从而减少土壤干燥和裂缝的形成。植被通过根系加固和冠层覆盖，显著提高土壤抗剪强度，减少土壤冲刷，增强土壤抗侵蚀能力。这两种措施的结合进一步优化了边坡的稳定性，其中DI-V-BAES模型在保持温度稳定性、含水率稳定性、减少裂缝率和提高抗冲刷性方面表现最佳。该方法显著提高了膨胀土边坡的整体稳定性和抗侵蚀能力，是边坡长期稳定的有效措施。滴灌促进植被生长，增加根系密度和持坡能力，植被通过根系发育提高土壤黏聚力和内摩擦角。综上所述，滴灌与植被协同管理模式为膨胀土护坡提供了理论基础和实践指导。

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引用次数: 0

Species identity outweighs richness in shaping soil microbial resource limitation in subtropical mixed Pinus massoniana-broadleaved plantations 亚热带马尾松阔叶混交林土壤微生物资源限制的物种特性大于丰富度

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2026-01-02 DOI: 10.1016/j.catena.2025.109744

Yi Li , Xi Fang , Wenhua Xiang , Pifeng Lei , Liang Chen , Shuai Ouyang , Xiangwen Deng , Yanting Hu , Huili Wu

This study investigates the effects of tree species richness and identity on soil microbial metabolic limitations in Pinus massoniana conifer-broadleaved mixed plantations, using the Vector-Threshold element ratio model. We found that microbial metabolism was predominantly constrained by phosphorus rather than carbon. Tree species richness did not significantly influence microbial carbon demand but exhibited a unimodal relationship with phosphorus limitation, initially alleviating it in species-poor mixtures before intensifying it in the highest richness stands. Instead, tree species identity was a far more decisive factor. The presence of Schima superba was most effective at alleviating microbial phosphorus limitation, while Elaeocarpus decipiens significantly increased carbon demand. These effects were diminished or reversed when broadleaved species co-occurred, highlighting complex non-additive mixing effects. Path analysis elucidated two distinct mechanistic pathways: (1) a richness-driven pathway, whereby higher richness improved litter quality, increasing soil pH and suppressing microbial carbon use efficiency (CUE), thereby elevating carbon demand while alleviating phosphorus limitation; and (2) an identity-driven pathway, whereby the coexistence of S. superba and E. decipiens strongly reduced litter layer biomass, which decreased soil carbon content and the carbon/nitrogen ratio to increase CUE and reduce carbon demand, while concurrently increasing soil water content to intensify phosphorus limitation. Our findings underscore that optimizing species combinations based on functional traits, rather than merely maximizing richness, is paramount for regulating microbial processes. We recommend mixed plantations of P. massoniana and S. superba to foster a more balanced microbial metabolism, thereby supporting soil carbon stabilization and nutrient cycling in subtropical ecosystems.

采用向量-阈值元素比模型，研究了树种丰富度和树种特性对马尾松针叶阔叶混交林土壤微生物代谢限制的影响。我们发现微生物代谢主要受磷而不是碳的限制。树种丰富度对微生物碳需求的影响不显著，但与磷限制呈单峰关系，在物种贫乏的混合林中，微生物碳需求最初减轻，然后在丰富度最高的林分中加剧。相反，树种的特性是一个更为决定性的因素。木荷的存在最有效地缓解了微生物磷限制，而松柏显著增加了碳需求。当阔叶物种共存时，这些效应减弱或逆转，突出了复杂的非加性混合效应。通径分析揭示了两种不同的机制途径：(1)丰度驱动途径，丰富度提高凋落物质量，提高土壤pH值，抑制微生物碳利用效率（CUE），从而提高碳需求，缓解磷限制；(2)认同驱动路径，即长叶沙棘和脱叶沙棘的共存显著降低凋落物层生物量，降低土壤碳含量和碳氮比，从而增加CUE和减少碳需求，同时增加土壤含水量，强化磷限制。我们的研究结果强调，基于功能特征优化物种组合，而不仅仅是最大化丰富度，对于调节微生物过程至关重要。我们建议马尾松和马尾松混合种植可以促进微生物代谢的平衡，从而支持亚热带生态系统土壤碳稳定和养分循环。

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引用次数: 0

Transformations of alpine tundra ecosystems over the last millennium in the Changbai Mountains of Northeast China 中国东北长白山地区近千年高寒冻土带生态系统的变化

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2026-01-02 DOI: 10.1016/j.catena.2025.109776

Shuai Zhang , Yuwen Fu , Zicheng Yu

Alpine tundra and treeline vegetation are highly sensitive to climate change, and paleo-records are essential for documenting and understanding past ecological response. Here, we use multiple proxies derived from peat soil cores—including AMS¹⁴C dating, plant macrofossils, pollen, and Sphagnum cellulose δ¹³C and δ¹⁸O—to investigate how small peat-accumulating patches and treeline vegetation at 2090 m elevation responded to climate change over the last millennium at a site located only 2.6 km from the volcano crater on the northern slope of the Changbai Mountains. The initial peat that contains abundant rootlets was dated at ∼1430 CE at the onset of the Little Ice Age (LIA; 1400–1950 CE), about 400 years after the major Millennium eruption, suggesting that reduced decomposition of herbaceous roots under cold conditions facilitate peat accumulation. After the extremely-low accumulation phase of the basal few centimeters of peat, a marked acceleration in carbon accumulation from ∼1 to >100 g C m⁻² yr⁻¹ after 1950 CE reflects enhanced vegetation productivity induced by climate warming. Sphagnum dominates the entire peat profiles, but the abundance of different species varies in response to moisture conditions. Since 2000 CE, a decline in δ¹³C from −21 ‰ to −24 ‰ indicates a drying trend, while an increase in δ¹⁸O from 13.8 ‰ to 15.7 ‰ reflects permafrost thaw and reduced snowmelt water supply, resulting in the dominance of a drought-tolerant species Sphagnum teres in nutrient-poor peat patches. Pollen records from this treeline location sensitively reflect the altitudinal vegetation dynamics, in particular the upslope migration of treeline and the decrease of Rhododendron shrubs in tundra zone. Accelerated warming and permafrost thaw since 2000 CE have driven treeline species (Betula ermanii) to rapidly migrate upslope. These transformative shifts in both alpine wetland and forest-tundra ecosystems highlight their sensitivity to climate change and underscore the importance to understand climate-hydrology-vegetation‑carbon feedbacks.

高寒苔原和林木线植被对气候变化高度敏感，古记录对于记录和理解过去的生态响应至关重要。在这里，我们使用来自泥炭土壤岩心的多种代用指标——包括AMS14C测年、植物宏观化石、花粉和Sphagnum cellulose δ13C和δ 18o——来研究在距离长白山北坡火山口仅2.6 km的地点，海拔2090 m的小泥炭堆积斑块和树线植被如何响应过去一千年的气候变化。最初的泥炭含有大量的小根，可追溯到公元1430年小冰期开始（LIA; 1400-1950 CE），大约在千年大喷发后400年，这表明在寒冷条件下草本根的分解减少有助于泥炭的积累。在基底数厘米泥炭极低的积累阶段之后，碳积累在1950年以后从1 ~ 100 g C m−2 yr−1显著加速，反映了气候变暖导致的植被生产力增强。泥炭属植物在整个泥炭剖面中占主导地位，但不同物种的丰度因湿度条件而异。2000年以来，δ13C从- 21‰下降到- 24‰，反映了干旱化趋势，δ18O从13.8‰上升到15.7‰，反映了多年冻土融化和融水供应减少，导致在营养贫瘠的泥炭斑块中以耐旱物种Sphagnum teres占优势。该林木线位置的花粉记录敏感地反映了植被的纵向动态，特别是苔原地带林木线的上坡迁移和杜鹃花灌木的减少。自公元2000年以来，气候变暖的加速和永久冻土的融化推动了林线物种（桦）的快速上坡迁移。高寒湿地和森林-冻土带生态系统的这些变革性变化突出了它们对气候变化的敏感性，并强调了了解气候-水文-植被-碳反馈的重要性。

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引用次数: 0

Historical influences of climate, vegetation and soil erosion on primary productivity of Huguangyan Maar Lake, southern China, documented by sedimentary phosphorus fractions for the past 1400 years 1400年来气候、植被和土壤侵蚀对湖光岩麻尔湖初级生产力的影响——基于沉积物磷组分的记录

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2026-01-01 DOI: 10.1016/j.catena.2025.109779

Hongpan Xue , Yiyan Chen , Xin Zhou , Luyao Tu , Li Ma , Shiwei Jiang , Ming Ji , Chao Huang , Deming Kong , Yanan Shen

Understanding long-term phosphorus (P) fraction dynamics in lake sediments and their responses to changes in soil erosion are critical for aquatic environmental management. However, the interactions between climate, vegetation, and soil erosion in regulating lacustrine P fractions and primary productivity remain poorly constrained. Here, we provide a comprehensive analysis of P fractions in Huguangyan Maar Lake (HML) sediments, integrated with soil erosion records, pollen assemblages, paleoclimate data, and productivity proxies derived from previous HML studies. Our results reveal the following order of P fraction abundance in HML sediments: aluminum-bound P (NaOH-P_i) > residual P (Res.-P) > iron and manganese (hydroxide)-bound P (NaBD-P_i) > calcium-bound P (HCl-P_i). According to variations of the different P fractions over the past 1400 years, four main stages were divided. During periods with weak soil erosion (before ∼830 CE and since 1880 CE), high tree cover increased total organic P (TP_o), NaOH-P_i and Res.-P in the weathering products of surrounding rocks, resulting in an increase of these P fractions in the sediments. Lower contents of TP_o, NaOH-P_i, and Res.-P were observed for the periods 830–1390 CE (the Medieval Climate Anomaly and its transition to the Little Ice Age) and 1390–1880 CE (the Little Ice Age, high-erosion intervals), which could be attributed to less trees with dominance of herbs and shrubs. Regional precipitation changes may indirectly affect NaBD-P_i and HCl-P_i by influencing duration and degree of lake water stratification and the carbonate ion levels in the water body, respectively. The synergistic effects of erosion, vegetation, and climate ultimately controlled the primary productivity of HML. These findings enhance our understanding of how environmental factors affect lake sediment P fractions and lacustrine productivity, offering insights for long-term lake conservation strategies.

了解湖泊沉积物中磷组分的长期动态及其对土壤侵蚀变化的响应对水生环境管理具有重要意义。然而，气候、植被和土壤侵蚀在调节湖泊磷组分和初级生产力方面的相互作用仍然知之甚少。本文结合土壤侵蚀记录、花粉组合、古气候数据和前人研究成果，对湖光岩麻尔湖沉积物中磷组分进行了综合分析。我们的研究结果显示，HML沉积物中P组分丰度的顺序如下：铝结合P (NaOH-Pi) >；残余P (res . P) >；铁和锰（氢氧化物）结合P (NaBD-Pi) >；钙结合P （HCl-Pi）。根据1400年来不同磷组分的变化，将其分为四个主要阶段。在土壤侵蚀较弱时期（~ 830 CE以前和1880 CE以后），高树木覆盖增加了周围岩石风化产物中的总有机P （TPo）、NaOH-Pi和res . P，导致沉积物中这些P组分增加。在830 ~ 1390 CE（中世纪气候异常及其向小冰期的过渡）和1390 ~ 1880 CE（小冰期高侵蚀期），TPo、NaOH-Pi和res . p含量较低，这可能是由于树木较少，草本和灌木为主。区域降水变化可能通过影响湖水分层持续时间和程度以及水体中碳酸盐离子水平间接影响NaBD-Pi和HCl-Pi。侵蚀、植被和气候的协同作用最终控制了HML的初级生产力。这些发现增强了我们对环境因素如何影响湖泊沉积物P组分和湖泊生产力的理解，为长期湖泊保护策略提供了见解。

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引用次数: 0

Linking microbial life history strategy to carbon use efficiency under changing substrate and nutrient conditions 在变化的基质和营养条件下，将微生物生活史策略与碳利用效率联系起来

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2025-12-31 DOI: 10.1016/j.catena.2025.109777

Gang Huang , Yan-feng Cao , Meng-hui Dong , Mo Bahram , Yan-gui Su

Microbial carbon use efficiency (CUE)—the allocation of carbon (C) between growth and respiration—is a key regulator of soil carbon turnover and microbial feedbacks to climate change. Yet, the microbial traits and environmental drivers shaping CUE in forest soils remain insufficiently understood. Here, we combined ¹⁸O-labeled DNA quantification of microbial growth with measurements of respiration, extracellular enzyme activities, and community composition across a 3842 km forest transect to assess how microbial ecological strategies influence CUE under contrasting resource conditions. Microbial CUE was estimated as the ratio of ¹⁸O-derived growth to total C uptake during controlled incubations. Microbial traits were characterized by extracellular enzymes involved in C, N, and P acquisition, as well as life-history strategies indicated by bacterial rRNA gene copy number and copiotrophic vs. oligotrophic taxa of microorganisms. We found that higher carbon availability stimulated C-acquiring enzyme production and microbial growth in high-latitude forests, resulting in elevated CUE. In contrast, N- and P-acquiring enzymes were associated with increased respiration in low-latitude forests, reflecting greater energy investment in nutrient acquisition at the expense of biomass production. Moreover, communities dominated by oligotrophic taxa exhibited reduced growth and enhanced respiration, consistent with lower CUE under low-resource conditions. Together, these findings indicate that shifts in microbial life-history strategies mediate resource-dependent trade-offs in carbon allocation, with important implications for soil carbon cycling across environmental gradients.

微生物碳利用效率（CUE）是指生长和呼吸之间的碳分配，是土壤碳周转和微生物对气候变化反馈的关键调节因子。然而，对森林土壤中形成CUE的微生物特征和环境驱动因素的了解仍然不够充分。在这里，我们将180o标记的微生物生长DNA量化与呼吸、细胞外酶活性和群落组成的测量相结合，跨越3842公里的森林样带，评估微生物生态策略在不同资源条件下如何影响CUE。微生物CUE被估计为在受控孵育期间180衍生的生长与总碳吸收的比率。微生物性状的特征包括参与C、N和P获取的胞外酶，以及细菌rRNA基因拷贝数和微生物的多养与少养分类群所指示的生活史策略。研究发现，高纬度森林中较高的碳有效性刺激了c获取酶的产生和微生物的生长，导致CUE升高。相比之下，在低纬度森林中，氮和磷获取酶与呼吸增加有关，反映出以牺牲生物量生产为代价，在养分获取上投入了更多的能量。此外，在低资源条件下，以少营养类群为主的群落表现出生长减少和呼吸增强，这与较低的CUE一致。总之，这些发现表明，微生物生活史策略的变化介导了碳分配中资源依赖的权衡，对土壤碳在环境梯度中的循环具有重要意义。

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引用次数: 0

Soil respiration rate as a spatial feature of the forest-steppe biome 森林草原生物群系土壤呼吸速率的空间特征

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2025-12-31 DOI: 10.1016/j.catena.2025.109774

Olga Sukhoveeva , Dmitry Karelin , Tatiana Lebedeva , Alexander Pochikalov , Nikolay Sobolev , Alipiy Zolotukhin

The study focuses on evaluating the influence of categorical variables on soil respiration (SR): region within a biome, year and ecosystem type, as well as crop species for arable soils. The research sites were located in four regions (Chuvash Republic, Ryazan, Tula, and Kursk regions) in the European part of the forest-steppe biome, which is poorly represented in global SR databases. Seven types of ecosystems were considered in each region: croplands, pastures, hayfields, grasslands, forests, stockyards, and compost piles. Measurements were carried out using the closed chamber method over a five-year period (2020–2024). We proposed the “spatial screenshot” method, which involves taking synchronous SR measurements in different ecosystems over a short period of time under similar environmental conditions. The hypothesis of the study was that the geographical location of points did not significantly affect SR if they were located within the same biome and that this could serve as a spatial feature of the biome. This hypothesis was confirmed, showing that geographical location does not affect the formation of soil CO₂ efflux, whereas ecosystem type and current environmental conditions are the key factors. SR was found to be similar in perennial plant communities (pastures, hayfields, grasslands, forests), lower on croplands, and an order of magnitude higher on livestock facilities than in other ecosystems. Overall, the average SR rate varies little in space and can therefore be considered a sustainable characteristic of the biome. This research enables the development of SR measurement schemes required at various levels: farm, region, and biome.

研究的重点是评价分类变量对土壤呼吸（SR）的影响：生物群系内区域、年份和生态系统类型，以及作物种类对耕地土壤的影响。研究地点位于森林草原生物群系欧洲部分的四个地区（楚瓦什共和国、梁赞、图拉和库尔斯克地区），这些地区在全球SR数据库中代表性较差。每个地区都考虑了七种类型的生态系统：农田、牧场、干草、草原、森林、畜牧场和堆肥堆。在5年（2020-2024年）的时间里，使用封闭腔法进行了测量。我们提出了“空间截图”方法，即在相似的环境条件下，在短时间内同步测量不同生态系统的SR。本研究的假设是，如果点位于同一生物群系内，其地理位置对SR的影响不显著，这可以作为生物群系的空间特征。这一假设得到了证实，表明地理位置不影响土壤CO2外排的形成，生态系统类型和当前环境条件是关键因素。多年生植物群落（牧场、干地、草原、森林）的SR与其他生态系统相似，农田的SR较低，而牲畜设施的SR比其他生态系统高一个数量级。总体而言，平均SR率在空间上变化不大，因此可以被认为是生物群系的可持续特征。这项研究使得在农场、区域和生物群系等不同层次上所需的SR测量方案得以发展。

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引用次数: 0

Tracing fertilizer transformation and leaching in karst soils via soil column experiments and nitrogen isotopes 利用土壤柱试验和氮同位素追踪喀斯特土壤的肥料转化和淋溶

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2025-12-30 DOI: 10.1016/j.catena.2025.109771

Ping Zhang , Yi-Meng Ren , Xiao-Dan Wang , Fu-Jun Yue

Excessive application of nitrogen fertilizer is the dominant driver behind the persistently increasing nitrogen concentrations in water bodies within karst areas. However, the variations of δ¹⁵N during the process of nitrogen fertilizer application to soil and subsequent NO₃⁻ leaching in these karst areas remain uncertain, hindering the effective tracing and quantification of nitrogen sources. In this study, soil column experiments were conducted to investigate the key nitrogen transformation and leaching processes, along with the associated changes in δ¹⁵N, in karst soil following nitrogen addition. The results showed that in the control soil column without added urea fertilizer (CK-column), δ¹⁵N variations (ranging from 0.9 to 8.8 ‰) were primarily driven by nitrification, ammonia volatilization, and denitrification. In contrast, the soil column amended with urea fertilizer (UF-column) exhibited pronounced δ¹⁵N fluctuations (from −35.8 to 13.8 ‰), which were predominantly governed by nitrification and ammonia volatilization. The unique soil properties (e.g., thin soil layer, higher permeability, and weak alkalinity) coupled with abundant precipitation, collectively shorten NO₃⁻ travel time through the soils. Moreover, a relatively high nitrification rate (mean: 6.5 mg N kg⁻¹d⁻¹) coupled with relatively lower ambient temperatures (mean: 13.2 °C) resulted in significant nitrogen isotope fractionation (ε_p/s: −26.2 ‰) in the topsoil. Furthermore, in the CK-column system, offsets in δ¹⁵N-NO₃⁻ values between soil and leachate were mainly observed in the deep soil layer (60 to 90 cm). In the UF-column system, the isotopic difference (Δ¹⁵N_L/U) between δ¹⁵N-NO₃⁻ in leachate and δ¹⁵N of urea fertilizer became increasingly positive with decreasing soil depth (D_S), following the relationship: Δ¹⁵N_L/U = −0.11D_S + 10.7. This study enhances our understanding of nitrogen migration and transformation in karst soils and facilitates the tracking of nitrogen sources in water bodies within karst area.

过量施用氮肥是喀斯特地区水体氮浓度持续升高的主要驱动因素。然而，喀斯特地区土壤氮肥施用及NO3−淋溶过程中δ15N的变化仍不确定，阻碍了氮源的有效追踪和量化。本研究通过土壤柱试验研究了氮素添加后喀斯特土壤中关键的氮转化和淋溶过程，以及相关的δ15N变化。结果表明，在未添加尿素的对照土柱（ck柱）中，δ15N的变化（范围在0.9 ~ 8.8‰）主要由硝化作用、氨挥发作用和反硝化作用驱动。尿素处理的土壤柱（uf柱）δ15N波动明显（−35.8 ~ 13.8‰），主要受硝化作用和氨挥发的影响。独特的土壤特性（如薄土层、高渗透性和弱碱性）加上丰富的降水，共同缩短了NO3−在土壤中的传播时间。此外，较高的硝化速率（平均6.5 mg N kg−1d−1）和较低的环境温度（平均13.2°C）导致表层土壤氮同位素分异显著（εp/s:−26.2‰）。此外，在ck柱系统中，土壤和渗滤液之间的δ15N-NO3−值偏移主要发生在深层土壤（60 ~ 90 cm）。在uf柱体系中，渗滤液中δ15N- no3−与尿素肥δ15N的同位素差异（Δ15NL/U）随着土壤深度（DS）的减小而增大，其关系为Δ15NL/U = - 0.11DS + 10.7。本研究增强了我们对喀斯特土壤氮素迁移转化的认识，为喀斯特地区水体氮素源的追踪提供了便利。

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引用次数: 0

Hydrologic connectivity as a predictor of degradation thresholds across semiarid sites with different vegetation patterns 水文连通性作为不同植被模式半干旱区退化阈值的预测因子

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2025-12-30 DOI: 10.1016/j.catena.2025.109754

Samira Azadi , Patricia M. Saco , Mariano Moreno-de las Heras , Jose F. Rodriguez

Dryland landscapes typically display a two-phase mosaic consisting of densely vegetated patches interspersed with low-cover or bare soil areas. The extent and spatial patterns of these patches have a direct effect on ecosystem function and disturbances, such as over grazing, can disrupt the original structure of vegetation and lead to degradation. This work investigates changes in the hydrologic connectivity (i.e., the degree to which areas of the landscape connect to each other) of Mulga landscapes induced by land degradation. Mulga is a keystone ecosystem of the Australian drylands and is characterised by a patchy vegetation cover, which can vary considerably from site to site. We analyse 31 plots with different degrees of degradation (or vegetation cover) in four Mulga sites with different precipitation, slope and vegetation and we quantify hydrologic connectivity combining high-resolution binary vegetation maps and DEMs. Results indicate that connectivity increases as vegetation cover decreases, but this relation is significantly non-linear with a clear threshold at 38 % vegetation cover below which connectivity (and loss of resources due to runoff out of the system) increases dramatically leading to degradation. A site with a pattern of vegetation strands concentrated along drainage lines showed consistently higher connectivity (due to longer connected paths) compared to the other sites where vegetation was more uniformly scattered or presented banded pattern perpendicular to drainage lines. Outputs from a vegetation thinning algorithm on patch edges consistent with grazing effects confirm the existence of the observed threshold in vegetation cover and the influence of vegetation patterns on connectivity. Our results indicate that connectivity is a strong indicator to detect degradation thresholds over a variety of vegetation arrangements typical of dryland systems.

旱地景观通常呈现出两阶段的马赛克，由密集的植被斑块点缀着低覆盖或裸露的土壤区域组成。这些斑块的范围和空间格局对生态系统功能有直接影响，而过度放牧等干扰会破坏植被的原始结构并导致退化。这项工作调查了由土地退化引起的Mulga景观的水文连通性（即景观区域相互连接的程度）的变化。Mulga是澳大利亚旱地的重要生态系统，其特点是植被覆盖斑驳，不同地点的植被差异很大。我们分析了四个不同降水、坡度和植被的Mulga站点的31个不同退化程度（或植被覆盖）的样地，并结合高分辨率二元植被图和dem量化了水文连通性。结果表明，连通性随着植被覆盖度的减少而增加，但这种关系明显是非线性的，在植被覆盖度为38%时，连通性（以及径流导致的资源损失）会急剧增加，从而导致退化。与植被更均匀分散或呈现垂直于排水线带状格局的其他地点相比，植被沿排水线集中的地点具有更高的连通性（由于连接路径更长）。在与放牧效应一致的斑块边缘上的植被减薄算法的输出证实了观测到的植被覆盖阈值的存在以及植被模式对连通性的影响。我们的研究结果表明，连通性是检测各种典型旱地系统植被安排的退化阈值的有力指标。

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引用次数: 0

Hillslope-induced environmental gradients regulate potential soil respiration in temperate peatlands 在温带泥炭地，坡地诱发的环境梯度调节着潜在的土壤呼吸

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena

Pub Date : 2025-12-30 DOI: 10.1016/j.catena.2025.109769

Yanfei Li , Pengzhi Zhao , Maud Henrion , Patrick Gerin , Matthieu Leclercq , Angus Moore , Eléonore du bois d'Aische , Sébastien Lambot , Sophie Opfergelt , Veerle Vanacker , François Jonard , Kristof Van Oost

Along peatland catenas, micro- to meso-scale topographic variation shapes microclimate and biogeochemical properties, creating distinct environmental regimes. Yet, how such heterogeneity regulates soil respiration in peatlands has been much less studied. To this end, we sampled five slope positions along a peatland hillslope and combined microclimate monitoring with laboratory incubations and geochemical analyses. Specifically, we asked: (1) How do hillslope-induced environmental gradients influence spatial patterns of potential soil respiration (PSR) in temperate peatlands? and (2) How does PSR respond to increasing temperature? Results showed that soil biogeochemistry (i.e., soil pH, C/N ratio, soil organic matter (SOM) functional groups), PSR rates, and apparent temperature sensitivity (i.e., activation energy, Ea) varied substantially across hillslope positions and soil depths. We found that topographical and thermal-hydrological conditions are associated to soil biogeochemistry patterns across the landscape. The spatial heterogeneity in PSR and Ea was primarily explained by the functional group composition of SOM (45–68 % and 34 % in total, respectively), with cellulose and carboxylic acids accounting for 27 %–31 % of the variation in PSR rates, while aliphatic and lignin functional groups explained 13 % of the variation in Ea. In addition, the C/N ratio and pH together accounted for 13 %–26 % of PSR rate variation and 18 % of variation in Ea. This study demonstrates that hillslope topography-driven variations in soil biogeochemical properties strongly regulate potential peat soil respiration and its temperature sensitivity, providing mechanistic insights into peatland carbon–climate feedback and informing peatland management strategies.

沿着泥炭地链，微到中尺度的地形变化塑造了小气候和生物地球化学特征，创造了不同的环境制度。然而，这种异质性如何调节泥炭地土壤呼吸的研究却少得多。为此，我们沿着泥炭地山坡取样了五个斜坡位置，并将小气候监测与实验室孵化和地球化学分析相结合。具体而言，我们提出了以下问题：(1)山坡环境梯度如何影响温带泥炭地潜在土壤呼吸（PSR）的空间格局？(2) PSR对温度升高有何反应？结果表明，土壤生物地球化学（即土壤pH、C/N比、土壤有机质（SOM）官能团）、PSR率和表观温度敏感性（即活化能，Ea）在不同坡位和土壤深度之间存在显著差异。我们发现地形和热水文条件与整个景观的土壤生物地球化学模式有关。PSR和Ea的空间异质性主要由SOM的官能团组成来解释（分别占45 - 68%和34%），其中纤维素和羧酸占PSR率变异的27% - 31%，而脂肪和木质素官能团占Ea变异的13%。C/N和pH分别占PSR速率变化的13% - 26%和Ea变化的18%。该研究表明，坡地地形驱动的土壤生物地球化学特性变化强烈地调节了潜在的泥炭土壤呼吸及其温度敏感性，为泥炭地碳-气候反馈提供了机制见解，并为泥炭地管理策略提供了信息。

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引用次数: 0

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