Forest phenology and a warmer climate – growing season extension in relation to climatic provenance

Abstract

Predicting forest responses to warming climates relies on assumptions about niche and temperature sensitivity that remain largely untested. Observational studies have related current and historical temperatures to phenological shifts, but experimental evidence is sparse, particularly for autumn responses. A 4 year field experiment exposed four deciduous forest species from contrasting climates (Liquidambar styraciflua, Quercus rubra, Populus grandidentata, and Betula alleghaniensis) to air temperatures 2 and 4 °C above ambient controls, using temperature‐controlled open top chambers. Impacts of year‐round warming on bud burst (BB), senescence, and abscission were evaluated in relation to thermal provenance. Leaves emerged earlier in all species by an average of 4–9 days at +2 °C and 6–14 days at +4 °C. Magnitude of advance varied with species and year, but was larger for the first 2 °C increment than for the second. Effect of warming increased with early BB, favoring Liquidambar, but even BB of northern species advanced, despite temperatures exceeding those of the realized niche. Treatment differences in BB were inadequately explained by temperature sums alone. In autumn, chlorophyll was retained an average of 4 and 7 days longer in +2 and +4 °C treatments, respectively, and abscission delayed by 8 and 13 days. Growing seasons in the warmer atmospheres averaged 5–18 days (E2) and 6–28 days (E4) longer, according to species, with the least impact in Quercus. Results are compared with a 16 years record of canopy onset and offset in a nearby upland deciduous forest, where BB showed similar responsiveness to spring temperatures (2–4 days °C−1). Offset dates in the stand tracked August–September temperatures, except when late summer drought caused premature senescence. The common garden‐like experiment provides evidence that warming alone extends the growing season, at both ends, even if stand‐level impacts may be complicated by variation in other environmental factors.

Spring and Autumn Phenological Variability across Environmental Gradients of Great Smoky Mountains National Park, USA

“…In general, autumn warmth delays senescence, while drought advances the onset of autumn [6,37]. While late-season hydrologic stress and productivity may not be consistently measured by autumn NDVI, here we find no strong support for summer or autumn drought-induced senescence ( Figures 6F and 8B).…”

Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: effects on nutrient proficiency

“…The timing of leaf senescence was positively correlated with previous flushing dates in the long-term European phenological records of both species, indicating that even though recent environmental cues dominated the variability in the phenology of leaf senescence, they could not fully account for it, which led to the hypothesis that leaf senescence could be triggered by the sink limitation that indicates the accumulation of non-structural carbohydrates in the leaves. Some long-term records indicate a negative correlation between the dates of leaf senescence or leaf fall in the autumn and temperatures in May and June Gordo & Sanz, 2010;Gunderson et al, 2012;Archetti et al, 2013), indicating that conditions experienced by the leaves long before leaf senescence may impact the timing of senescence. Efforts are needed to determine the relevance of this possibility for evaluating its inclusion in models and for discarding possible relationships with water stress.…”

“…Similarly, the dates for offset of season usually tracked August and September temperatures in a 16-year period in deciduous forests, except when late summer drought caused premature leaf senescence (Gunderson et al, 2012). Accordingly, the interference of water stress prevented the patterns of leaf senescence from following the temperature gradient across an altitudinal gradient (Hwang et al, 2014).…”

Seed Germination and Seedling Survival Rate of Pinus densiflora and Abies holophylla in Open-field Experimental Warming Using the Infrared Lamp

“…또한 발아 후 유묘 단계에서는 뿌리와 줄기 발달 이 미약하기 때문에 온도 상승에 따른 변화가 민감하게 나타나서 (Houle, 1994), 온도 상승에 따른 지구 온난화 영 향 예측이 성묘보다 용이하다 (Lloret et al, 2009) (Gunderson et al, 2012;Hillier et al, 1994;Ineson et al, 1998;Morin et al, 2010;Nakamura et al, 2010), 적 외선등을 이용한 실외 온난화 실험은 자연 생태계와 가 장 유사하게 환경 조건에서 온난화 시스템 조절이 가능 한 장점이 있는 것으로 알려져 있다 (Kimball et al, 2008). (Bonner et al, 2008).…”