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Due to anthropogenic pressures, only 3% of the historic extent of the biodiverse longleaf pine ecosystem remains, much of which is degraded. Fire is necessary for maintaining longleaf pine savanna structure, function, and biodiversity; however, it also creates resource constraints, as nutrients are volatilized, especially in the already nutrient‐depleted soils of many longleaf pine savannas. Nutrient limitation and subsequent competition between plants can lead to changes in species diversity and productivity. Using a multiyear, chronic nutrient addition experiment, we explore how resource limitation influences restoration outcomes in longleaf pine savannas by affecting (1) productivity, (2) biodiversity metrics, and (3) community composition. In the field, we established a factorial N and P nutrient addition (10 g m−1 year−1) experiment. Nutrient additions were administered for 4 years, and plant composition and biomass were collected yearly. We measured biomass each year by functional group and calculated diversity metrics and community composition changes. Understory productivity typically increased with N and P additions, with N × P together having no additive effect. There were several significant interacting effects of nutrient addition treatments with year on our biodiversity metrics; however, the main nutrient addition effects were not significant for any biodiversity metric. Finally, community composition was significantly different in nutrient addition plots compared to control. Our results show that xeric Sandhill longleaf pine savannas exhibit distinct responses to fertilization, as fertilization led to increased productivity of the groundcover without reducing biodiversity. Low‐level, chronic nutrient inputs could influence understory structure in ways that help meet numerous management objectives, such as promoting fire spread or increasing forage availability. However, this may also present challenges, such as encouraging woody encroachment or threatening rare species. Our findings highlight the need for context‐specific approaches to longleaf pine savanna management and a careful evaluation of how nutrient dynamics interact with long‐term conservation and restoration goals. Due to anthropogenic pressures, only 3% of the historic extent of the biodiverse longleaf pine ecosystem remains, much of which is degraded. Fire is necessary for maintaining longleaf pine savanna structure, function, and biodiversity; however, it also creates resource constraints, as nutrients are volatilized, especially in the already nutrient‐depleted soils of many longleaf pine savannas. Nutrient limitation and subsequent competition between plants can lead to changes in species diversity and productivity. Using a multiyear, chronic nutrient addition experiment, we explore how resource limitation influences restoration outcomes in longleaf pine savannas by affecting (1) productivity, (2) biodiversity metrics, and (3) community composition. In the field, we established a factorial N and P nutrient addition (10 g m−1 year−1) experiment. Nutrient additions were administered for 4 years, and plant composition and biomass were collected yearly. We measured biomass each year by functional group and calculated diversity metrics and community composition changes. Understory productivity typically increased with N and P additions, with N × P together having no additive effect. There were several significant interacting effects of nutrient addition treatments with year on our biodiversity metrics; however, the main nutrient addition effects were not significant for any biodiversity metric. Finally, community composition was significantly different in nutrient addition plots compared to control. Our results show that xeric Sandhill longleaf pine savannas exhibit distinct responses to fertilization compared to other grasslands and savannas globally, as fertilization led to increased productivity of the groundcover without reducing biodiversity. Low‐level, chronic nutrient inputs could influence understory structure in ways that help meet numerous management objectives, such as promoting fire spread or increasing forage availability. However, this may also present challenges, such as encouraging woody encroachment or threatening rare species. Our findings highlight the need for context‐specific approaches to longleaf pine savanna management and a careful evaluation of how nutrient dynamics interact with long‐term conservation and restoration goals.

The frequency and intensity of extreme climatic events such as heatwaves are predicted to increase under continued climate change and rising atmospheric CO2. Degraded and fragmented ecosystems are at particular risk of being greatly impacted by such extreme events. The longleaf pine (LLP) savanna ecosystem, once the dominant ecosystem throughout the Southeast Coastal Plains of the United States, has been reduced to a small percentage of its pre‐colonization range. While the effect of heatwaves on grassland systems has been well explored, less focus has been given to the legacy effects of previous climatic events. Through a greenhouse experiment using Schizachyrium scoparium (little bluestem), a dominant understory grass species in LLP savanna ecosystems, we aimed to study the legacy effects of heatwaves (i.e., higher temperatures and lower precipitation and humidity) across multiple plant performance metrics and stress responses. S. scoparium had a negative response to an early heatwave, showing increased mortality, smaller maximum leaf length, fewer leaves, decreased specific leaf area (SLA), decreased leaf thickness, and reduced belowground net primary productivity (NPP) when compared to plants that did not experience a heatwave. S. scoparium individuals exposed to a late heatwave had fewer leaves, reduced SLA, and thinner leaves when compared to plants that did not experience a heatwave. While plants exposed to both an early and late heatwave experienced an increase in some stress responses as observed by increased catalase activity and plant mortality, they exhibited no change in other stress responses studied (e.g., maximum leaf length, relative growth rate, productivity, leaf thickness, peroxidase levels, or fuel load). Overall, our study revealed that S. scoparium may show neutral‐to‐positive legacy effects in response to multiple heatwaves. This indicates that LLP savanna ecosystems dominated by S. scoparium may display resistance to the predicted increased frequency of heatwaves in the southeastern United States, an important outcome for the heavily degraded and endangered ecosystem.