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Biotic Multipliers of Climate Change
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A focus on species interactions may improve predictions of the effects of climate change
on ecosystems.
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Climate Science Documents
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A general integrative model for scaling plant growth, carbon flux, and functional trait spectra
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Linking functional traits to plant growth is critical for scaling attributes of organisms to the dynamics of ecosystems (1,2) and for understanding how selection shapes integrated botanical phenotypes (3). However, a general mechanistic theory showing how traits specifically influence carbon and biomass flux within and across plants is needed. Building on foundational work on relative growth rate (4–6), recent work on functional trait spectra (7–9), and metabolic scaling theory (10,11), here we derive a generalized trait-based model of plant growth. In agreement with a wide variety of empirical data, our model uniquely predicts how key functional traits interact to regulate variation in relative growth rate, the allometric growth normalizations for both angiosperms and gymnosperms, and the quantitative form of several functional trait spectra relationships. The model also provides a general quantitative framework to incorporate additional leaf-level trait scaling relationships (7,8) and hence to unite functional trait spectra with theories of relative growth rate, and metabolic scaling. We apply the model to calculate carbon use efficiency. This often ignored trait, which may influence variation in relative growth rate, appears to vary directionally across geographic gradients. Together, our results show how both quantitative plant traits and the geometry of vascular transport networks can be merged into a common scaling theory. Our model provides a framework for predicting not only how traits covary within an integrated allometric phenotype but also how trait variation mechanistically influences plant growth and carbon flux within and across diverse ecosystems.
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Climate Science Documents
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Drought, disease, defoliation and death: forest pathogens as agents of past vegetation change
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The temperate and boreal forests of Europe and North America have been subject to repeated pathogen (fungal disease and phytophagus insect) outbreaks over the last 100 years. Palaeoecology can, potentially, offer a long-term perspective on such disturbance episodes, providing information on their triggers, frequency and impact. Mid-Holocene declines in Tsuga and Ulmus pollen dominate the Quaternary literature on forest pathogens, yet the role of pathogens, and even the presence of pathogenic fungal diseases, during these events has yet to be established. Pathogen-focused research strategies, informed by the sequence of events documented in modern outbreaks, and undertaken at high temporal resolution using a multi-proxy approach, are required. It is argued that forest pathogens are likely to have been significant agents of past vegetation change, even in cases where climate change was the primary stress factor.
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Climate Science Documents
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BOTANY AND A CHANGING WORLD: INTRODUCTION TO THE SPECIAL ISSUE ON GLOBAL BIOLOGICAL CHANGE
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The impacts of global change have heightened the need to understand how organisms respond to and influence these changes. Can we forecast how change at the global scale may lead to biological change? Can we identify systems, processes, and organisms that are most vulnerable to global changes? Can we use this understanding to enhance resilience to global changes? This special issue on global biological change emphasizes the integration of botanical information at different biological levels to gain perspective on the direct and indirect effects of global change. Contributions span a range of spatial scales and include both ecological and evolutionary timescales and highlight work across levels of organization, including cellular and physiological processes, individuals, populations, and ecosystems. Integrative botanical approaches to global change are critical for the eco- logical and evolutionary insights they provide and for the implications these studies have for species conservation and ecosys- tem management.
Key words: community dynamics; flowering phenology; functional traits; global biological change; invasive species; land-use patterns; plant–microbial interactions; species interactions.
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Climate Science Documents
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Divergent phenological response to hydroclimate variability in forested mountain watersheds
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Mountain watersheds are primary sources of freshwater, carbon sequestration, and other ecosystem services. There is significant interest in the effects of climate change and variability on these processes over short to long time scales. Much of the impact of hydroclimate variability in forest ecosystems is manifested in vegetation dynamics in space and time. In steep terrain, leaf phenology responds to topoclimate in complex ways, and can produce specific and measurable shifts in landscape forest patterns. The onset of spring is usually delayed at a specific rate with increasing elevation (often called Hopkins’ Law; Hopkins, 1918), reflecting the dominant controls of temperature on greenup timing. Contrary with greenup, leaf senescence shows inconsistent trends along elevation gradients. Here, we present mechanisms and an explanation for this variability and its significance for ecosystem patterns and services in response to climate. We use moderate-resolution imaging spectro-radiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data to derive landscape-induced phenological patterns over topoclimate gradients in a humid temperate broadleaf forest in southern Appalachians. These phenological patterns are validated with different sets of field observations. Our data demonstrate that divergent behavior of leaf senescence with elevation is closely related to late growing season hydroclimate variability in temperature and water balance patterns. Specifically, a drier late growing season is associated with earlier leaf senescence at low elevation than at middle elevation. The effect of drought stress on vegetation senescence timing also leads to tighter coupling between growing season length and ecosystem water use estimated from observed precipitation and runoff generation. This study indicates increased late growing season drought may be leading to divergent ecosystem response between high and low elevation forests. Landscape-induced phenological patterns are easily observed over wide areas and may be used as a unique diagnos- tic for sources of ecosystem vulnerability and sensitivity to hydroclimate change.
Keywords: drought deciduousness, hydroclimate variability, landscape phenology, MODIS NDVI, topoclimate gradient
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Climate Science Documents
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Agenda - March 11, 2015 Workshop
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Urban Woodlands Conservation and Management Workshop. Organized and facilitated by the National Park Service to identify and create opportunities for greater collaboration among urban woodland researchers and managers working to restore and manage urban woodland ecosystems.
To view the goals and objectives of the workshop, please open the workshop agenda.
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Cultural Resources
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Urban Conservation
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Urban Woodlands Conservation and Restoration
