New Zealand Seed Ecology in the Pyrocene: Testing Seed Responses to High Temperatures Under Laboratory Conditions

Fire has been an historically rare disturbance in New Zealand ecosystems that is becoming increasingly frequent. Most native plants lack fire‐related adaptations, contrasting with exotic species that evolved with frequent fire disturbance. We investigated seed responses to short‐duration heat exposure in five native and four exotic species to assess the potential responses of these species to soil heating. Seeds were exposed to no heat or to 60, 80 or 100 °C for 10 min, with physically dormant species subjected to both scarified and non‐scarified treatments in a factorial design. For the species without physical dormancy, the native Cordyline australis and Melicytus ramiflorus were sensitive to heating, with no germination above 60 °C, whereas the exotic Pinus radiata and Pseudotsuga menziesii tolerated higher temperatures. Among physically dormant species, responses differed among taxa. Heating broke physical dormancy in the native Carmichaelia australis and the exotic Ulex europaeus, whereas only physical scarification broke dormancy in Cytisus scoparius , Discaria toumatou and Sophora microphylla. Carmichaelia australis , Cytisus scoparius and Sophora microphylla tolerated heating to 80 °C, and Ulex europaeus to 100 °C, while Discaria toumatou viability was lost above 60 °C. Our results demonstrate that while most native species show limited seed‐based fire resilience, Carmichaelia australis exhibits heat‐stimulated germination suggestive of ancestral or exaptive fire‐related traits. These findings improve understanding of regeneration potential under emerging fire regimes and highlight species‐specific seed traits that shape post‐fire vegetation dynamics in New Zealand.