Ant-mediated seed dispersal in a warmed world

Climate change affects communities both directly and indirectly via changes in interspecific interactions. One such interaction that may be altered under climate change is the ant-plant seed dispersal mutualism common in deciduous forests of eastern North America. As climatic warming alters the abundance and activity levels of ants, the potential exists for shifts in rates of ant-mediated seed dispersal. We used an experimental temperature manipulation at two sites in the eastern US (Harvard Forest in Massachusetts and Duke Forest in North Carolina) to examine the potential impacts of climatic warming on overall rates of seed dispersal (using Asarum canadense seeds) as well as species-specific rates of seed dispersal at the Duke Forest site. We also examined the relationship between ant critical thermal maxima (CTmax) and the mean seed removal temperature for each ant species. We found that seed removal rates did not change as a result of experimental warming at either study site, nor were there any changes in species-specific rates of seed dispersal. There was, however, a positive relationship between CTmax and mean seed removal temperature, whereby species with higher CTmax removed more seeds at hotter temperatures. The temperature at which seeds were removed was influenced by experimental warming as well as diurnal and day-to-day fluctuations in temperature. Taken together, our results suggest that while temperature may play a role in regulating seed removal by ants, ant plant seed-dispersal mutualisms may be more robust to climate change than currently assumed

The handbook for standardized field and laboratory measurements in terrestrial climate change experiments and observational studies (ClimEx)

1. Climate change is a world‐wide threat to biodiversity and ecosystem structure, functioning and services. To understand the underlying drivers and mechanisms, and to predict the consequences for nature and people, we urgently need better understanding of the direction and magnitude of climate change impacts across the soil–plant–atmosphere continuum. An increasing number of climate change studies are creating new opportunities for meaningful and high‐quality generalizations and improved process understanding. However, significant challenges exist related to data availability and/or compatibility across studies, compromising opportunities for data re‐use, synthesis and upscaling. Many of these challenges relate to a lack of an established ‘best practice’ for measuring key impacts and responses. This restrains our current understanding of complex processes and mechanisms in terrestrial ecosystems related to climate change. 2. To overcome these challenges, we collected best‐practice methods emerging from major ecological research networks and experiments, as synthesized by 115 experts from across a wide range of scientific disciplines. Our handbook contains guidance on the selection of response variables for different purposes, protocols for standardized measurements of 66 such response variables and advice on data management. Specifically, we recommend a minimum subset of variables that should be collected in all climate change studies to allow data re‐use and synthesis, and give guidance on additional variables critical for different types of synthesis and upscaling. The goal of this community effort is to facilitate awareness of the importance and broader application of standardized methods to promote data re‐use, availability, compatibility and transparency. We envision improved research practices that will increase returns on investments in individual research projects, facilitate second‐order research outputs and create opportunities for collaboration across scientific communities. Ultimately, this should significantly improve the quality and impact of the science, which is required to fulfil society's needs in a changing world

Evaluating the Influence of Disturbance and Climate on Red Spruce (Picea rubens Sarg.) Community Dynamics at its Southern Range Margin

Picea rubens(red spruce) populations experienced a synchronous rangewide decline in growth and vigor starting in the 1960’s, which was likely caused by climate change or environmental disturbances (e.g., acid deposition); However, it is yet unknown if populations continue to decline or have recovered. In the context of global warming, red spruce is a species of concern because it is at its southern continuous range margin in Massachusetts. This study uses tree-ring data coupled with population data from permanent plots to quantify the status of red spruce in Massachusetts. Tree cores were extracted from red spruce and used to examine radial growth rates, determine a growth-climate relationship, and document disturbance events. Red spruce at these plots ranged from 90 to 184 years old, and comprised 15 to 29 m2/ha-1 basal area. Over the past 50 years, red spruce has decreased in density, basal area, and relative importance while red maple, yellow birch, and American beech have increased. Red spruce saplings persisted in some plots, but the sapling layer was comprised mostly of American beech or red maple. However, red spruce seedlings were common at red spruce dominant plots indicating that if favorable conditions occur, it could return to its more dominant position in the canopy. Dendroclimatological analyses show that red spruce is sensitive to both temperature and precipitation. Most sites are correlated with temperature, while only twoforests were correlated to precipitation. The general temperature response of the red spruce studied was positively correlated with winter temperatures while the general precipitation response was negatively correlated with precipitation. Temporal analysis of the climate-growth response indicates that red spruce here have not had a temporally-stable, climate-growth relationship. Prior to 1960, radial growth was positively correlated with temperatures from November of the previous growing season to January of the current year. After 1960, all sites showed a shift in growth responses consistent with increased summer temperature stress; narrowed tree rings were formed during warm temperatures in July and August. Precipitation remained relatively constant over the past century, while temperatures have increased up to 2˚C across the study area. Of the two precipitation-sensitive forests, one forest shifted from being positively correlated with current January precipitation to negatively correlated with previous October precipitation while the second forest showed a strong positive relationship with August precipitation. Because the radial growth of red spruce here are mostly constrained by temperatures, there has been negative growth response to regional warming and precipitation has been stable, I suggest the change in climate response is potentially due to warming and a physiological threshold response to increasing temperatures. Interestingly, disturbance frequency and intensity have increased over the same time period, which could be either a trigger or a response to the shift in the growth-climate relationship

No Mow May Lawns Have Higher Pollinator Richness and Abundances: An Engaged Community Provides Floral Resources for Pollinators

No Mow May is a community science initiative popularized in recent years that encourages property owners to limit their lawn mowing practices during the month of May. The goal of No Mow May is to provide early season foraging resources for pollinators that emerge in the spring, especially in urban landscapes when few floral resources are available. We worked with the city council of Appleton, Wisconsin, USA. to allow No Mow May to take place in May 2020. Four hundred and thirty-five property owners registered for No Mow May in Appleton. We measured floral and bee richness and abundance in the yards of a subset of homes (N = 20) located near regularly mowed urban parks (N = 15) at the end of the month. We found that homes that participated in No Mow May had more diverse and abundant flora than regularly mowed green spaces throughout the city. No Mow May homes had three times higher bee richness and five times higher bee abundances than frequently mowed greenspaces. Using generalized linear models, we found that the best predictor of bee richness was the size of the designated unmowed area, and the best predictors of bee abundances were the size of the unmowed area as well as floral richness. While our findings cannot conclusively attribute increases in bee abundances and richness to the No Mow May efforts, our data does show that bee pollinators make use of no mow spaces as key floral resources during early spring in the upper midwestern United States. A post-No Mow May survey revealed that the participants were keen to increase native floral resources in their yards, increase native bee nesting habitat, reduce mowing intensities, and limit herbicide, pesticide, and fertilizer applications to their lawns. The No Mow May initiative educated an engaged community on best practices to improve the conservation of urban pollinators in future years

Ant-mediated ecosystem functions on a warmer planet: effects on soil movement, decomposition and nutrient cycling

1.Direct and indirect consequences of global warming on ecosystem functions and processes mediated by invertebrates remain understudied but are likely to have major impacts on ecosystems in the future. Among animals, invertebrates are taxonomically diverse, responsive to temperature changes, and play major ecological roles which also respond to temperature changes. 2.We used a mesocosm experiment to evaluate impacts of two warming treatments (+3.5 and + 5 °C, set points) and the presence and absence of the ant Formica subsericea (a major mediator of processes in north-temperate ecosystems) on decomposition rate, soil movement, soil respiration, and nitrogen availability. 3.Replicate 19-Litre mesocosms were placed outdoors in lathe houses and continuously warmed for 30 days in 2011 and 85 days in 2012. Warming treatments mimicked expected temperature increases for future climates in eastern North America. 4.In both years, the amount of soil displaced and soil respiration increased in the warming and ant presence treatments (soil movement: 73 – 119%; soil respiration: 37 – 48% relative to the control treatments without ants). 5.Decomposition rate and nitrogen availability tended to decrease in the warmest treatments (decomposition rate: -26 – -30%; nitrate availability: -11 – -42%). 6.Path analyses indicated that ants had significant short term direct and indirect effects on the studied ecosystem processes. These results suggest that ants may be moving more soil and building deeper nests to escape increasing temperatures, but warming may also influence their direct and indirect effects on soil ecosystem processes.Organismic and Evolutionary Biolog

Data from: Burning for biodiversity: highly resilient ant communities respond only to strongly contrasting fire regimes in Australia’s seasonal tropics

1. According to the pyrodiversity paradigm, a wide range of fire regimes is required to maintain biodiversity in fire-prone landscapes. However, the requisite level of pyrodiversity has seldom been tested and may actually be very low. 2. Here, we examine the sensitivity of tropical savanna ants to variation in fire regimes using results from a long-term fire experiment near Darwin, Australia. Six experimental fire regimes, with varying fire frequency and seasonality, have been applied to 18 one-ha plots in three replicated blocks since 2004, with ants sampled prior to experimental burning and then annually after up to 2009. Our primary focus is on the extent to which different patterns of ant richness and composition are associated with each of the six treatment regimes, or whether there is such high overlap that differences only become apparent when experimental treatments are grouped to provide strongly contrasting fire regimes. 3. When treating each of the six fire treatments separately, we were unable to detect a significant influence of fire on any ant community response variable. We were only able to detect significant ant responses when we grouped the experimental treatments into two contrasting fire frequency classes, low (burnt at most once over the 5 years) vs. high (burnt every 1 or 2 years). Even then, these responses were only evident after 3 years of fire treatment. 4. Our findings demonstrate that ant communities have very high resilience in relation to fire, with differences evident only between strongly contrasting regimes. Such resilience appears to be characteristic of savanna ants throughout the world. 5. Synthesis and applications. A large range of finely tuned fire regimes is unlikely to promote regional ant diversity. Rather, only very limited pyrodiversity (a combination of frequently and infrequently burnt areas) would appear to be sufficient for maintaining diversity at a landscape scale. It is important that fire management for biodiversity conservation focuses on the demonstrated requirements of target species, rather than be based on an assumption that ‘pyrodiversity begets biodiversity’

Andersen archived data

Abundance of each ant species at each of the 18 experimental fire plots at the Territory Wildlife Park for each sampling period (2003-2009). Data for each sampling period are provided on separate pages

Supplement 1. R code, extended statistical output, and additional graphics.

<h2>File List</h2><div> <p><a href="Ants_and_Ecosystem_Functions.html">Ants_and_Ecosystem_Functions.html</a> (MD5: 4c3a02abbc6344156498e959dab14044) </p> </div><h2>Description</h2><div> <p>Commented and executed R code, statistical output, and additional and diagnostic graphics for all analyses in this publication. HTML file was generated within RStudio using the knitr function.</p> <p>The original R code and all raw data files called for these analyses also are available from the Harvard Forest Data Archive (<a href="http://harvardforest.fas.harvard.edu/data-archive/">http://harvardforest.fas.harvard.edu/data-archive/</a>), dataset HF160-07.</p> </div