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1. Herbivory damage but not plant disease under experimental warming is dependent on weather for three subalpine grass species

   https://doi.org/10.1111/1365-2745.14050  

   Lynn, Joshua S; Abo‐Sido, Nisreen; McCowen, Ian W; Villanueva, Shermila B; Harte, John; Rudgers, Jennifer A (March 2023, Journal of Ecology)

   Abstract Both theory and prior studies predict that climate warming should increase attack rates by herbivores and pathogens on plants. However, past work has often assumed that variation in abiotic conditions other than temperature (e.g. precipitation) do not alter warming responses of plant damage by natural enemies. Studies over short time periods span low variation in weather, and studies over long time‐scales often neglect to account for fine‐scale weather conditions.Here, we used a 20+ year warming experiment to investigate if warming affects on herbivory and pathogen disease are dependent on variation in ambient weather observed over 3 years. We studied three common grass species in a subalpine meadow in the Colorado Rocky Mountains, USA. We visually estimated herbivory and disease every 2 weeks during the growing season and evaluated weather conditions during the previous 2‐ or 4‐week time interval (2‐week average air temperature, 2‐ and 4‐week cumulative precipitation) as predictors of the probability and amount of damage.Herbivore attack was 13% more likely and damage amount was 29% greater in warmed plots than controls across the focal species but warming treatment had little affect on plant disease. Herbivory presence and damage increased the most with experimental warming when preceded by wetter, rather than drier, fine‐scale weather, but preceding ambient temperature did not strongly interact with elevated warming to influence herbivory.Disease presence and amount increased, on average, with warmer weather and more precipitation regardless of warming.Synthesis. The effect of warming over reference climate on herbivore damage is dependent on and amplified by fine‐scale weather variation, suggesting more boom‐and‐bust damage dynamics with increasing climate variability. However, the mean effect of regional climate change is likely reduced monsoon rainfall, for which we predict a reduction in insect herbivore damage. Plant disease was generally unresponsive to warming, which may be a consequence of our coarse disease estimates that did not track specific pathogen species or guilds. The results point towards temperature as an important but not sufficient determinant and regulator of species interactions, where precipitation and other constraints may determine the affect of warming. 

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2. Precipitation anomalies may affect productivity resilience by shifting plant community properties

   https://doi.org/10.1111/1365-2745.14471  

   Perez, Sierra; Hammond, Mark; Lau, Jennifer (March 2025, Journal of Ecology)

   Abstract Climate change is causing marked shifts to historic environmental regimes, including increases in precipitation events (droughts and highly wet periods). Relative to droughts, the impacts of wet events have received less attention, despite heavy rainfall events increasing over the past century. Further, impacts of wet and dry events are often evaluated independently; yet, to persist and maintain their ecosystem functions, plant communities must be resilient to both precipitation events. This is particularly critical because while community properties can modulate the resilience (resistance, recovery, and invariability) of ecosystem functions to precipitation events, community properties can also respond to precipitation events. As a result, community responses to wet and dry years may impact the community's resilience to future events.Using two decades (2000–2020) of annual net primary productivity data from early successional grassland communities, we evaluated the plant community properties regulating primary productivity resistance and recovery to contrasting precipitation events and invariability (i.e. long‐term stability). We then explored how resilience‐modulating community properties responded to precipitation.We found that community properties—specifically, evenness, dominant species (Solidago altissima) relative abundance, and species richness—strongly regulate productivity resistance to drought and predict productivity invariability and tended to promote resistance to wet years. These community properties also responded to both wet and dry precipitation extremes and exhibited lagged responses that lasted into the next growing season. We infer that these connections between precipitation events, community properties, and resilience may lead to feedbacks impacting a plant community's resilience to subsequent precipitation events.Synthesis. By exploring the impacts of both drought and wet extremes, our work uncovers how precipitation events, which may not necessarily impact productivity directly, could still cryptically influence resilience via shifts in resilience‐promoting properties of the plant community. We conclude that these precipitation event‐driven community shifts may feedback to impact long‐term productivity resilience under climate change. 

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3. Mycorrhizal fungi as critical biotic filters for tree seedling establishment during species range expansions

   https://doi.org/10.1002/ecm.1634  

   Tourville, Jordon C; Horton, Thomas R; Dovciak, Martin (November 2024, Ecological Monographs)

   Abstract Global warming has been shifting climatic envelopes of many tree species to higher latitudes and elevations across the globe; however, unsuitable soil biota may inhibit tree migrations into these areas of suitable climate. Specifically, the role of mycorrhizal fungi in facilitating tree seedling establishment beyond natural species range limits has not been fully explored within forest ecosystems. We used three experiments to isolate and quantify the effects of mycorrhizal colonization and common mycorrhizal networks (CMN) on tree seedling survival and growth across (within and beyond) the elevational ranges of two dominant tree species in northeastern North America, which were associated with either arbuscular mycorrhiza (AMF,Acer saccharum) or ectomycorrhiza (EMF,Fagus grandifolia). In order to quantify the influence of mycorrhiza on seedling establishment independent of soil chemistry and climate, we grew seedlings in soils from within and beyond our study species ranges in a greenhouse experiment (GE) as well as in the field using a soil translocation experiment (STE) and another field experiment manipulating seedling connections to potential CMNs (CMNE). Root length colonized, seedling survival and growth, foliar nutrients, and the presence of potential root pathogens were examined as metrics influencing plant performance across species' ranges. Mycorrhizal inoculum from within species ranges, but not from outside, increased seedling survival and growth in a greenhouse setting; however, only seedling survival, and not growth, was significantly improved in field studies. Sustained potential connectivity to AMF networks increased seedling survival across the entire elevational range ofA. saccharum. Although seedlings disconnected from a potential CMN did not suffer decreased foliar nutrient levels compared with connected seedlings, disconnected AM seedlings, but not EM seedlings, had significantly higher aluminum concentrations and more potential pathogens present. Our results indicate that mycorrhizal fungi may facilitate tree seedling establishment beyond species range boundaries in this forested ecosystem and that the magnitude of this effect is modulated by the dominant mycorrhizal type present (i.e., AM vs. EM). Thus, despite changing climate conditions beyond species ranges, a lack of suitable mutualists can still limit successful seedling establishment and stall adaptive climate‐induced shifts in tree species distributions. 

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4. Effects of seedling conspecific density and heterospecific frequency on insect herbivory in a tropical dry forest

   https://doi.org/10.1111/afe.12574  

   Abdala‐Roberts, Luis; Berny‐Mier_y_Terán, Jorge Carlos; Vázquez‐González, Carla; Cohuo, Ariel; León, Jorge; Valle, Limbenr; Mooney, Kailen A; Reyes‐Novelo, Enrique; Moreira, Xoaquín (November 2023, Agricultural and Forest Entomology)

   Abstract Conspecific plant density and heterospecific frequency are key drivers of herbivore damage. However, most studies have investigated their effects separately and for single (rather than multiple) focal plant species.We conducted an experiment involving three tree species, namely:Cordia dodecandra(Boraginaceae),Manilkara zapota(Zapotaceae), andPiscidia piscipula(Fabaceae). We manipulated understory densities ofM. zapotaandC. dodecandra(focal species) and their frequency relative toP. piscipula.Three months after planting, we surveyed insect leaf chewer and sucking damage on the former two. Because these species are attacked by different herbivores, we predicted a negative effect of heterospecific frequency on herbivory.Density and frequency varied in the direction and function of their effects on herbivory depending on the plant species and attacking herbivore. As expected,Piscidia piscipulafrequency had a negative linear effect onM. zapotaleaf‐chewer damage, whereas conspecific density did not affect chewer damage on this species. In contrast, density and frequency had non‐linear effects onC. dodecandrachewer damage, namely positive (hump‐shaped) and negative (U‐shaped) relationships, respectively. In addition, density and frequency had positive linear effects onC. dondecandradamage by leafhoppers.These findings call for more work jointly assessing plant inter‐specific variation in density‐ and frequency‐dependent variation in herbivory and its underlying drivers. 

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5. Facilitating Reforestation Through the Plant Microbiome: Perspectives from the Phyllosphere

   https://doi.org/10.1146/annurev-phyto-021320-010717  

   Busby, Posy E.; Newcombe, George; Neat, Abigail S.; Averill, Colin (August 2022, Annual Review of Phytopathology)

   Tree planting and natural regeneration contribute to the ongoing effort to restore Earth's forests. Our review addresses how the plant microbiome can enhance the survival of planted and naturally regenerating seedlings and serve in long-term forest carbon capture and the conservation of biodiversity. We focus on fungal leaf endophytes, ubiquitous defensive symbionts that protect against pathogens. We first show that fungal and oomycetous pathogen richness varies greatly for tree species native to the United States ( n = 0–876 known pathogens per US tree species), with nearly half of tree species either without pathogens in these major groups or with unknown pathogens. Endophytes are insurance against the poorly known and changing threat of tree pathogens. Next, we review studies of plant phyllosphere feedback, but knowledge gaps prevent us from evaluating whether adding conspecific leaf litter to planted seedlings promotes defensive symbiosis, analogous to adding soil to promote positive feedback. Finally, we discuss research priorities for integrating the plant microbiome into efforts to expand Earth's forests. 

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