More than 70% of the world’s forests are less than one kilometer from a forest edge. As edge habitat increases due to fragmentation, edge effects – such as the unique microclimate at edges – also become more prevalent.
Forest edges tend to be warmer and drier than forest interiors, which can have consequences for species that are sensitive to temperature or moisture. As climate change is predicted to increase temperatures and drought, these edge conditions could be exacerbated by climate change.
You, W., Xian, Z., Zhou, G., Agathokleous, E., and Yu, Z. 2023. Sensitivity of forest phenology in China varies with proximity to forest edges. Forest Ecosystems 10: 1000144.
One indicator of climate effects is plant phenology, which is the timing of life-cycle events such as flowering time or leaf fall. Many species, like pollinators or primary consumers, rely on the timing of these plant life cycles for resources. Plant phenology is heavily determined by climate patterns, so changes in phenology events can indicate changes in climate. While past studies have looked at how climate shifts phenology, few have looked at the role of landscape structure.
Recent research looked at how forest edges interact with temperature and precipitation to shift forest phenology. Researchers used remote sensing data from over 3,000 sampling points across China to measure tree phenology in natural deciduous forests and monoculture planted forests. They focused on three phenological events: green-up date (trees producing first leaves), dormancy date (trees losing leaves), and forest productivity (how much the forest grows).
The study found that forest edges in deciduous forests had a longer growing season than interior forests, with earlier green-up dates and later dormancy dates. However, despite this longer growing season, forest edges were not more productive than forest interiors, indicating that forest edges have lower photosynthesis activity.
Looking at climate conditions, forest productivity was more sensitive to temperature and precipitation near forest edges. This means that increases in temperature mattered more for tree phenology at forest edges, suggesting that forest edges may be less resilient to climate change than interior forests.
Climate also impacted edges in different ways than interior forest – at edges, more precipitation caused earlier green-up dates, but in interior forest, more precipitation caused later green-up dates. Because forest edges are more vulnerable to drought stress, this increased precipitation advanced green-up dates for edges but delayed green-up dates in interior forest. Climate is important for mediating phenology events, but climate can have different effects at forest edges.
This research highlights the impact of habitat edges on plant life-cycle events. Given that plant phenology is important for biogeochemical cycles, pollination, and carbon cycling, shifts in plant phenology could have large consequences for forest ecosystems. Understanding how forest edges respond to climate conditions is critical for predicting the stability of future forest dynamics.
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