Time lags: insights from the U.S. Long Term Ecological Research Network

Ecosystems across the United States are changing in complex ways that are difficult to predict. Coordinated long-term research and analysis are required to assess how these changes will affect a diverse array of ecosystem services. This paper is part of a series that is a product of a synthesis effort of the U.S. National Science Foundation’s Long Term Ecological Research (LTER) network. This effort revealed that each LTER site had at least one compelling scientific case study about “what their site would look like” in 50 or 100 yr. As the site results were prepared, themes emerged, and the case studies were grouped into separate papers along five themes: state change, connectivity, resilience, time lags, and cascading effects and compiled into this special issue. This paper addresses the time lags theme with five examples from diverse biomes including tundra (Arctic), coastal upwelling (California Current Ecosystem), montane forests (Coweeta), and Everglades freshwater and coastal wetlands (Florida Coastal Everglades) LTER sites. Its objective is to demonstrate the importance of different types of time lags, in different kinds of ecosystems, as drivers of ecosystem structure and function and how these can effectively be addressed with long-term studies. The concept that slow, interactive, compounded changes can have dramatic effects on ecosystem structure, function, services, and future scenarios is apparent in many systems, but they are difficult to quantify and predict. The case studies presented here illustrate the expanding scope of thinking about time lags within the LTER network and beyond. Specifically, they examine what variables are best indicators of lagged changes in arctic tundra, how progressive ocean warming can have profound effects on zooplankton and phytoplankton in waters off the California coast, how a series of species changes over many decades can affect Eastern deciduous forests, and how infrequent, extreme cold spells and storms can have enduring effects on fish populations and wetland vegetation along the Southeast coast and the Gulf of Mexico. The case studies highlight the need for a diverse set of LTER (and other research networks) sites to sort out the multiple components of time lag effects in ecosystems

Long-term demography and stem productivity of Everglades mangrove forests (Florida, USA): Resistance to hurricane disturbance.

Mangrove wetlands along coastal regions in neotropical northern latitudes are exposed to frequent hurricanes and therefore depend on resistant and resilient attributes to persist after these extreme events. However, few long-term studies have documented mangrove forest dynamics following hurricane disturbance to determine how species-specific phenotypic plasticity, species range shifts, and environmental stress interact to determine recovery trajectories. We present here a comprehensive analysis of Hurricane Wilma’s (hereafter, “Wilma”) impact (category 3, October 2005) on mangrove forest demography and aboveground net productivity in the Everglades, Florida (USA). We determined spatiotemporal patterns over a 15-year period (5 pre- and 10 post-Wilma) in three impacted sites on a productivity gradient along the Shark River Estuary. Hurricane resistance was evident in the low cumulative tree mortality and long-term recovery from defoliation (∼10 years). Aboveground standing carbon stocks were not significantly reduced, as mortality ranged only from 3 to 10%. A negative linear relationship between Leaf Net Primary Productivity (NPPL) and foliar residence time along the estuary shows that an increase in foliar production results in shorter residence time, which is defined by the interannual variation in NPPL rates and recovery periods across sites. We propose this relationship as a proxy of canopy recovery in latitudinal comparative studies across mangrove ecotypes and coastal settings. This work advances ecological disturbance theory and ecological modeling of mangrove forests; specifically, we provide quantitative relationships among structural properties and dynamic processes to validate agent-based demographic and biogeochemical models to forecast the impact of natural and human disturbances on mangrove wetlands under climate change

Assessment of Everglades mangrove forest resilience: Implications for above-ground net primary productivity and carbon dynamics

We evaluated mangrove forest resilience in the Florida Coastal Everglades (FCE) by analyzing long-term (2001–2014) spatial and temporal patterns of litterfall net primary productivity (NPPL), including the impact and recovery from two natural disturbance events: Hurricane Wilma (October-2005) and a cold snap (January-2010). Specifically, we tested whether the disturbance driven recovery trajectory of mangrove forests (i.e. recovery duration and rate) depends on the disturbance impact magnitude and initial forest structure in three study sites. Hurricane Wilma caused canopy defoliation at all sites and was a function of the wind-field strength such that higher wind speeds at the SRS-6 site (30–40 m s−1) induced greatest defoliation (4.7 Mg C ha−1 yr−1). Disturbance magnitude (decrease in NPPL from 2005 to 2006) was higher in SRS-6 (7.8 Mg C ha−1 yr−1), followed by SRS-4 (5.7 Mg C ha−1 yr−1) and SRS-5 (5.5 Mg C ha−1 yr−1). We observed differential NPPL recovery times among sites and species, where sites SRS-5 and SRS-6 returned to pre-Wilma NPPL rates by 2010 while SRS-4 has not yet fully recovered. In contrast, the cold snap had significant disturbance impact, yet recovery occurred within one month across all sites. We conclude that differential resilience to Hurricane Wilma was a result of a synergy of local changes in hydrology, salinity and storm impact. The long-term ability of subtropical mangroves to recover to pre-disturbance production rates within a short period (\u3c5 years) demonstrates their resilience capacity in cases where massive defoliation occurs as result of natural disturbances

Time lags: insights from the U.S. Long Term Ecological Research Network

Abstract Ecosystems across the United States are changing in complex ways that are difficult to predict. Coordinated long‐term research and analysis are required to assess how these changes will affect a diverse array of ecosystem services. This paper is part of a series that is a product of a synthesis effort of the U.S. National Science Foundation’s Long Term Ecological Research (LTER) network. This effort revealed that each LTER site had at least one compelling scientific case study about “what their site would look like” in 50 or 100 yr. As the site results were prepared, themes emerged, and the case studies were grouped into separate papers along five themes: state change, connectivity, resilience, time lags, and cascading effects and compiled into this special issue. This paper addresses the time lags theme with five examples from diverse biomes including tundra (Arctic), coastal upwelling (California Current Ecosystem), montane forests (Coweeta), and Everglades freshwater and coastal wetlands (Florida Coastal Everglades) LTER sites. Its objective is to demonstrate the importance of different types of time lags, in different kinds of ecosystems, as drivers of ecosystem structure and function and how these can effectively be addressed with long‐term studies. The concept that slow, interactive, compounded changes can have dramatic effects on ecosystem structure, function, services, and future scenarios is apparent in many systems, but they are difficult to quantify and predict. The case studies presented here illustrate the expanding scope of thinking about time lags within the LTER network and beyond. Specifically, they examine what variables are best indicators of lagged changes in arctic tundra, how progressive ocean warming can have profound effects on zooplankton and phytoplankton in waters off the California coast, how a series of species changes over many decades can affect Eastern deciduous forests, and how infrequent, extreme cold spells and storms can have enduring effects on fish populations and wetland vegetation along the Southeast coast and the Gulf of Mexico. The case studies highlight the need for a diverse set of LTER (and other research networks) sites to sort out the multiple components of time lag effects in ecosystems

Time lags: insights from the U.S. Long Term Ecological Research Network

Abstract Ecosystems across the United States are changing in complex ways that are difficult to predict. Coordinated long‐term research and analysis are required to assess how these changes will affect a diverse array of ecosystem services. This paper is part of a series that is a product of a synthesis effort of the U.S. National Science Foundation’s Long Term Ecological Research (LTER) network. This effort revealed that each LTER site had at least one compelling scientific case study about “what their site would look like” in 50 or 100 yr. As the site results were prepared, themes emerged, and the case studies were grouped into separate papers along five themes: state change, connectivity, resilience, time lags, and cascading effects and compiled into this special issue. This paper addresses the time lags theme with five examples from diverse biomes including tundra (Arctic), coastal upwelling (California Current Ecosystem), montane forests (Coweeta), and Everglades freshwater and coastal wetlands (Florida Coastal Everglades) LTER sites. Its objective is to demonstrate the importance of different types of time lags, in different kinds of ecosystems, as drivers of ecosystem structure and function and how these can effectively be addressed with long‐term studies. The concept that slow, interactive, compounded changes can have dramatic effects on ecosystem structure, function, services, and future scenarios is apparent in many systems, but they are difficult to quantify and predict. The case studies presented here illustrate the expanding scope of thinking about time lags within the LTER network and beyond. Specifically, they examine what variables are best indicators of lagged changes in arctic tundra, how progressive ocean warming can have profound effects on zooplankton and phytoplankton in waters off the California coast, how a series of species changes over many decades can affect Eastern deciduous forests, and how infrequent, extreme cold spells and storms can have enduring effects on fish populations and wetland vegetation along the Southeast coast and the Gulf of Mexico. The case studies highlight the need for a diverse set of LTER (and other research networks) sites to sort out the multiple components of time lag effects in ecosystems