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Abstract Climate change is creating phenological mismatches between herbivores and their plant resources throughout the Arctic. While advancing growing seasons and changing arrival times of migratory herbivores can have consequences for herbivores and forage quality, developing mismatches could also influence other traits of plants, such as above‐ and below‐ground biomass and the type of reproduction, that are often not investigated.In coastal western Alaska, we conducted a 3‐year factorial experiment that simulated scenarios of phenological mismatch by manipulating the start of the growing season (3 weeks early and ambient) and grazing times (3 weeks early, typical, 3 weeks late, or no‐grazing) of Pacific black brant (Branta bernicla nigricans), to examine how the timing of these events influence a primary goose forage species,Carex subspathacea.After 3 years, an advanced growing season compared to a typical growing season increased stem heights, standing dead biomass, and the number of inflorescences. Early season grazing compared to typical season grazing reduced above‐ and below‐ground biomass, stem height, and the number of tillers; while late season grazing increased the number of inflorescences and standing dead biomass. Therefore, an advanced growing season and late grazing had similar directional effects on most plant traits, but a 3‐week delay in grazing had an impact on traits 3–5 times greater than a similarly timed shift in the advancement of spring. In addition, changes in response to treatments for some variables, such as the number of inflorescences, were not measurable until the second year of the experiment, while other variables, such as root productivity and number of tillers, changed the direction of their responses to treatments over time.Synthesis. Factors affecting the timing of migration have a larger influence than earlier springs on an important forage species in the breeding and rearing habitats of Pacific black brant. The phenological mismatch prediction for this site of earlier springs and later goose arrival will likely increase above‐ and below‐ground biomass and sexual reproduction of the often‐clonally reproducingC. subspathacea. Finally, the implications of mismatch may be difficult to predict because some variables required successive years of mismatch to respond.
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Contrasting responses to climate change at Himalayan treelines revealed by population demographics of two dominant species
Abstract Alpine treelines are expected to shift upward due to recent climate change. However, interpretation of changes in montane systems has been problematic because effects of climate change are frequently confounded with those of land use changes. The eastern Himalaya, particularly Langtang National Park, Central Nepal, has been relatively undisturbed for centuries and thus presents an opportunity for studying climate change impacts on alpine treeline uncontaminated by potential confounding factors.We studied two dominant species,Abies spectabilis (AS)andRhododendron campanulatum (RC), above and below the treeline on two mountains. We constructed 13 transects, each spanning up to 400 m in elevation, in which we recorded height and state (dead or alive) of all trees, as well as slope, aspect, canopy density, and measures of anthropogenic and animal disturbance.All size classes ofRCplants had lower mortality above treeline than below it, and youngRCplants (<2 m tall) were at higher density above treeline than below.ASshows little evidence of a position change from the historic treeline, with a sudden extreme drop in density above treeline compared to below. Recruitment, as measured by size–class distribution, was greater above treeline than below for both species butASis confined to ~25 m above treeline whereasRCis luxuriantly growing up to 200 m above treeline.Synthesis. Evidence suggests that the elevational limits ofRChave shifted upward both because (a) young plants above treeline benefited from facilitation of recruitment by surrounding vegetation, allowing upward expansion of recruitment, and (b) temperature amelioration to mature plants increased adult survival. We predict that the current pure stand ofRCgrowing above treeline will be colonized byASthat will, in turn, outshade and eventually relegateRCto be a minor component of the community, as is the current situation below the treeline.
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- Award ID(s):
- 1915347
- PAR ID:
- 10449401
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 10
- Issue:
- 3
- ISSN:
- 2045-7758
- Page Range / eLocation ID:
- p. 1209-1222
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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