Xuying Hai , Jianping Li , Qing Qu , Junwen Yang , Zhouping Shangguan , Lei Deng
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Under higher early-growing-season precipitation, NP addition enhanced intrinsic WUE (iWUE) while reducing impacts on evapotranspiration (ET) and ecosystem WUE (W<sub>G</sub>). Conversely, under drier conditions, NP addition weakened iWUE gains but amplified ET and W<sub>G</sub> responses. At the carbon flux level, net ecosystem CO₂ exchange (NEE) was more strongly controlled by gross ecosystem production (GEP) than by ecosystem respiration (ER), indicating photosynthetic activity as the primary driver of net carbon sequestration. Single N addition increased the GEP, ER but reduced NEE. In contrast, the N effect under the condition of NP co-addition suppressed GEP, ER, and NEE. Single P addition increased GEP, ER, and NEE, whereas the P effect under the condition of NP co-addition promoted ER but inhibited both GEP and NEE. This study elucidates threshold effects in nutrient-driven carbon-water coupling, where stoichiometric interactions between N and P regulate carbon cycling and plant hydraulic strategies. The observed precipitation-dependent synergism/antagonism highlights the nonlinear responses of arid ecosystems to future nutrient deposition scenarios. The present study improves our understanding of the coupled mechanisms of future global C, N, P, and water dynamics, and provides insights for adaptive grassland and water resource management under climate change.</div></div>","PeriodicalId":7634,"journal":{"name":"Agricultural Water Management","volume":"320 ","pages":"Article 109858"},"PeriodicalIF":6.5000,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Nitrogen and phosphorus enrichment synergistically alter carbon-water exchange in desert steppe ecosystems\",\"authors\":\"Xuying Hai , Jianping Li , Qing Qu , Junwen Yang , Zhouping Shangguan , Lei Deng\",\"doi\":\"10.1016/j.agwat.2025.109858\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Semi-arid grasslands are simultaneously limited by nitrogen (N) and phosphorus (P), yet the effects of their additions on carbon–water coupling remain poorly understood. This knowledge gap hampers predictions of ecosystem responses to nutrient deposition under global climate change. We hypothesized that N and P inputs would alter ecosystem carbon sequestration and water-use efficiency (WUE), and that these effects would be strongly modulated by precipitation. To test this, we conducted a randomized block design experiment in 2020–2022 with N (10 g N m⁻² yr⁻¹) and P (8 g P m⁻² yr⁻¹) additions in a <em>Stipa breviflora</em>-dominated desert steppe in Yanchi County, China. Our results showed that precipitation emerged as a dominant regulator of nutrient effects. Under higher early-growing-season precipitation, NP addition enhanced intrinsic WUE (iWUE) while reducing impacts on evapotranspiration (ET) and ecosystem WUE (W<sub>G</sub>). Conversely, under drier conditions, NP addition weakened iWUE gains but amplified ET and W<sub>G</sub> responses. At the carbon flux level, net ecosystem CO₂ exchange (NEE) was more strongly controlled by gross ecosystem production (GEP) than by ecosystem respiration (ER), indicating photosynthetic activity as the primary driver of net carbon sequestration. Single N addition increased the GEP, ER but reduced NEE. In contrast, the N effect under the condition of NP co-addition suppressed GEP, ER, and NEE. Single P addition increased GEP, ER, and NEE, whereas the P effect under the condition of NP co-addition promoted ER but inhibited both GEP and NEE. This study elucidates threshold effects in nutrient-driven carbon-water coupling, where stoichiometric interactions between N and P regulate carbon cycling and plant hydraulic strategies. The observed precipitation-dependent synergism/antagonism highlights the nonlinear responses of arid ecosystems to future nutrient deposition scenarios. 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引用次数: 0
摘要
半干旱草原同时受到氮(N)和磷(P)的限制,但它们的添加对碳-水耦合的影响尚不清楚。这种知识差距阻碍了对全球气候变化下生态系统对养分沉积反应的预测。我们假设氮和磷的输入会改变生态系统的碳固存和水利用效率(WUE),而这些影响会受到降水的强烈调节。为了验证这一点,我们在2020-2022年在中国盐池县一个以针茅为主的沙漠草原上进行了一项随机区组设计实验,添加了N(10 g N m⁻²yr⁻¹)和P(8 g P m⁻²yr⁻¹)。我们的研究结果表明,降水是养分效应的主要调节因子。在生长季前期降水量较高的条件下,NP的添加提高了内在水分利用效率(iWUE),降低了对蒸散发(ET)和生态系统水分利用效率(WG)的影响。相反,在干燥条件下,添加NP会削弱iWUE的增益,但会放大ET和WG的响应。在碳通量水平上,生态系统净CO₂交换(NEE)受生态系统总生产量(GEP)的控制强于生态系统呼吸(ER),表明光合作用是净碳固存的主要驱动力。单次N添加增加了GEP和ER,但降低了NEE。相反,NP共加条件下的N效应抑制了GEP、ER和NEE。单一磷添加增加了GEP、ER和NEE,而NP共添加条件下的P效应促进了ER,抑制了GEP和NEE。本研究阐明了养分驱动的碳-水耦合的阈值效应,其中氮和磷之间的化学计量相互作用调节了碳循环和植物的水力策略。观测到的降水依赖的协同/拮抗作用突出了干旱生态系统对未来养分沉积情景的非线性响应。本研究有助于进一步认识未来全球碳、氮、磷和水动态的耦合机制,为气候变化下草地和水资源的适应性管理提供参考。
Nitrogen and phosphorus enrichment synergistically alter carbon-water exchange in desert steppe ecosystems
Semi-arid grasslands are simultaneously limited by nitrogen (N) and phosphorus (P), yet the effects of their additions on carbon–water coupling remain poorly understood. This knowledge gap hampers predictions of ecosystem responses to nutrient deposition under global climate change. We hypothesized that N and P inputs would alter ecosystem carbon sequestration and water-use efficiency (WUE), and that these effects would be strongly modulated by precipitation. To test this, we conducted a randomized block design experiment in 2020–2022 with N (10 g N m⁻² yr⁻¹) and P (8 g P m⁻² yr⁻¹) additions in a Stipa breviflora-dominated desert steppe in Yanchi County, China. Our results showed that precipitation emerged as a dominant regulator of nutrient effects. Under higher early-growing-season precipitation, NP addition enhanced intrinsic WUE (iWUE) while reducing impacts on evapotranspiration (ET) and ecosystem WUE (WG). Conversely, under drier conditions, NP addition weakened iWUE gains but amplified ET and WG responses. At the carbon flux level, net ecosystem CO₂ exchange (NEE) was more strongly controlled by gross ecosystem production (GEP) than by ecosystem respiration (ER), indicating photosynthetic activity as the primary driver of net carbon sequestration. Single N addition increased the GEP, ER but reduced NEE. In contrast, the N effect under the condition of NP co-addition suppressed GEP, ER, and NEE. Single P addition increased GEP, ER, and NEE, whereas the P effect under the condition of NP co-addition promoted ER but inhibited both GEP and NEE. This study elucidates threshold effects in nutrient-driven carbon-water coupling, where stoichiometric interactions between N and P regulate carbon cycling and plant hydraulic strategies. The observed precipitation-dependent synergism/antagonism highlights the nonlinear responses of arid ecosystems to future nutrient deposition scenarios. The present study improves our understanding of the coupled mechanisms of future global C, N, P, and water dynamics, and provides insights for adaptive grassland and water resource management under climate change.
期刊介绍:
Agricultural Water Management publishes papers of international significance relating to the science, economics, and policy of agricultural water management. In all cases, manuscripts must address implications and provide insight regarding agricultural water management.