Soil disturbance and invasion magnify CO2 effects on grassland productivity, reducing diversity

Climate change, disturbance, and plant invasion threaten grassland ecosystems, but their combined and interactive effects are poorly understood. Here, we examine how the combination of disturbance and plant invasion influences the sensitivity of mixedgrass prairie to elevated carbon dioxide (eCO2) and warming. We established subplots of intact prairie and disturbed/invaded prairie within a free-air CO2 enrichment (to 600 ppmv) by infrared warming (+1.5 °C day, 3 °C night) experiment and followed plant and soil responses for five years. Elevated CO2 initially led to moderate increases in biomass and plant diversity in both intact and disturbed/invaded prairie, but these effects shifted due to strong eCO2 responses of the invasive forb Centaurea diffusa. In the final three years, biomass responses to eCO2 in disturbed/invaded prairie were 10 times as large as those in intact prairie (+186% vs. +18%), resulting in reduced rather than increased plant diversity (-17% vs. +10%). At the same t...气候变化、干扰与植物入侵正严重威胁草原生态系统，但目前学界对三者的联合作用与交互效应仍缺乏深入认知。本研究旨在探讨干扰与植物入侵的共同作用，如何影响混生草本草原（mixedgrass prairie）对二氧化碳富集（elevated carbon dioxide, eCO2）与增温的敏感性。我们在设置二氧化碳浓度至600ppmv的自由大气二氧化碳富集（free-air CO2 enrichment）配合红外增温（日间增温1.5℃、夜间增温3℃）的实验样地中，设置了原生草原与受干扰/已入侵草原两类亚样地，并连续五年监测植物与土壤的响应特征。二氧化碳富集初期，原生草原与受干扰/已入侵草原的生物量与植物多样性均出现小幅提升，但由于入侵性非禾本科草本植物（forb）扩散矢车菊（Centaurea diffusa）对二氧化碳富集的强烈响应，上述效应发生了显著转变。在实验的最后三年，受干扰/已入侵草原对eCO2的生物量响应幅度是原生草原的10倍（分别为+186%与+18%），导致其植物多样性非但未提升反而下降（降幅达17%，而原生草原的多样性增幅为10%）。与此同时，