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1. Variation of root resource acquisition and conservation strategies in a temperate forest is linked with plant growth forms

   https://doi.org/10.1093/treephys/tpaf027  

   Wang, Siyuan; Comas, Louise H; Reich, Peter B; McCormack, M Luke; Phillips, Richard P; Gu, Jiacun; Sun, Tao (March 2025, Tree Physiology)

   Wang, Han (Ed.)

   Abstract Exploring why species of different plant growth forms can coexist in the same forest is critical for understanding the long-term community stability, but is poorly studied from root ecological strategies. The aim of this study was to explore the variation of root functional traits among different growth forms and their distribution patterns in root economics space to clarify how plant growth forms affect the root resource acquisition strategies of co-occurring species in a forest community. We sampled 115 co-occurring species with five growth forms (i.e., trees, shrubs, lianas, herbs and ferns) from a mega-plot (>50 ha) in temperate forest and measured seven root functional traits, including root morphological, anatomical and chemical traits, that are closely associated with root resource foraging and conservation strategies. We found that root specific length (SRL) and tissue density (RTD) showed wider variations than other traits among the five growth forms. Moreover, compared with clade and mycorrhizal type, variations of SRL and RTD were largely attributed to growth forms. Importantly, 115 co-occurring species were separately aggregated by growth forms along the trade-off dimension of SRL and RTD in root economics space, suggesting the diversity in root resource acquisition strategies at a local forest community is linked to plant growth forms. In particular, herbs were concentrated towards the side of high SRL and RN, by contrast, trees, shrubs and ferns were positioned at the side of high RTD and carbon/nitrogen, and lianas were located towards the middle. Diverse root resource acquisition strategies in plant growth forms allow them to occupy specific belowground ecological niches, thereby relieving the competition for the common resource. These findings advance our understanding of the mechanism for maintaining community species coexistence from a below-ground perspective. 

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2. Revisiting Diagrams of Ice Growth Environments

   https://doi.org/10.1175/BAMS-D-21-0271.1  

   Hueholt, Daniel M.; Yuter, Sandra E.; Miller, Matthew A. (November 2022, Bulletin of the American Meteorological Society)

   Abstract Ice habit diagrams published prior to 2009—and many since—do not accurately describe in situ observations of ice shapes as a function of temperature and moisture. Laboratory studies and analysis of field observations by Bailey and Hallett in a series of papers in 2002, 2004, and 2009 corrected several errors from earlier studies, but their work has not been widely disseminated. We present a new, simplified diagram based on Bailey and Hallett’s work that focuses on several ice growth forms arising from the underlying surface processes by which mass is added to a crystal: tabular, columnar, branched, side branched, two types of polycrystalline forms, and a multiple growth regime at low ice supersaturations. To aid interpretation for a variety of applications, versions of the ice growth diagram are presented in terms of relative humidity with respect to water as well as the traditional formats of relative humidity with respect to ice and vapor density excess. These diagrams are intended to be understandable and useful in classroom settings at the sophomore undergraduate level and above. The myriad shapes of pristine snow crystals can be described as the result of either a single growth form or a sequence of growth forms. Overlays of data from upper-air soundings on the ice growth diagrams aid interpretation of expected physical properties and processes in conditions of ice growth. 

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3. Alternate Growth Forms Can Protect Climate-Threatened Trees from Freezing Stressors

   https://doi.org/10.1093/forsci/fxac038  

   Buma, Brian (October 2022, Forest Science)

   Abstract Climate change creates a variety of novel stressors for species, such as a decline in snowpack. Loss of snow has many impacts, including the loss of thermal insulation of soils. Winter/spring freezing of soils has been tied to forest mass mortality in multiple locations around the world. Many species, however, can take alternative growth forms, such as tall tree forms and short shrub-like forms. Shrub-forms may provide a unique protection from the snow loss phenomenon by providing a similar thermal insulation as snowpack. That hypothesis is tested here using yellow-cedar, a species undergoing mass mortality due to snow loss. Temperature loggers were placed under both tree- and shrub-form cedars, including areas where the species was experimentally removed. The number of soil freezing days was high in open areas, areas of tree mortality, and where the shrub-form was removed, but was almost zero in areas where the shrub-form was left intact. This suggests that growth-form temperature moderation is possible and may provide an important resistance to the mortality mechanism. In other areas around the world where snow loss is resulting in soil freezing and mortality, growth forms should be investigated as a potential moderating mechanism for this particular climate change stress. 

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4. Moss phyllid morphology varies systematically with substrate slope

   https://doi.org/10.5091/plecevo.2021.1839  

   Turberville, Caleb M.; Fuentes-González, Jesualdo A.; Rogers, Sydney; Pienaar, Jason (November 2021, Plant Ecology and Evolution)

   Background and aims – Tracheophyte leaf morphology is well studied but it is unclear if the findings generalize to poikilohydric plants. We tested combinations of hypotheses to determine if microhabitat characteristics, including light exposure, moisture availability, and substrate slope, controlled for morphological differences between upright and prostrate growth forms, affect phyllid surface area and costa length of mosses.Material and methods – We quantified mean phyllid surface-area and costa lengths for four replicates of 38 moss species from Alabama. Phylogenetic comparative methods that model adaptation were used to evaluate the relative evidence for each hypothesis using information criteria. To further explore mechanistic explanations involving substrate slope, we tested whether mosses on vertical substrates differed from those on horizontal substrates in the average amount of water-retaining, nutrient-rich litter they accumulated.Key results – Substrate slope and growth form combined were the best predictors of phyllid surface area. Mosses growing on vertical substrates exhibited smaller phyllid surface area for both growth forms. Although growth form and phyllid length best explained costa length variation, a more complex model including substrate slope performed nearly as well. Within the prostrate growth forms, species growing on vertical substrates exhibit longer relative costa than those on horizontal substrates. We also estimated rapid rates of adaptation for both traits.Conclusion – The smaller phyllid surface area of both upright and prostrate growth forms is possibly an adaptive response to reduced habitat moisture-retention or nutrient quality that vertical substrates offer. The longer costa lengths of prostrate mosses growing on vertical surfaces relative to prostrate mosses on horizontal surfaces, possibly make up for the decreased ability of smaller phyllids to rapidly reabsorb water when it is available. Further work is required to determine if it is truly substrate slope itself that matters or other variables associated with the differences in slope, and to determine how general this phenomenon is. 

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5. Divergent resource‐use strategies of encroaching shrubs: Can traits predict encroachment success in tallgrass prairie?

   https://doi.org/10.1111/1365-2745.14456  

   Wedel, Emily_R; Ratajczak, Zak; Tooley, E_Greg; Nippert, Jesse_B (December 2024, Journal of Ecology)

   Abstract Changes in climate and land management over the last half‐century have favoured woody plants native to grasslands and led to the rapid expansion of woody species. Despite this being a global phenomenon, it is unclear why some woody species have rapidly expanded while others have not. We assessed whether the most abundant woody encroaching species in tallgrass prairie have common growth forms and physiology or unique traits that differentiate their resource‐use strategies.We characterized the abundance, above‐ground carbon allocation, and leaf‐level physiological and structural traits of seven woody encroaching species in tallgrass prairie that span an order of magnitude in abundance. To identify species‐specific increases in abundance, we used a 34‐year species composition dataset at Konza Prairie Biological Station (Central Great Plains, USA). We then compared biomass allocation and leaf‐level traits to determine differences in carbon and water use strategies among species.While all focal species increased in abundance over time, encroachment in this system is primarily driven by three species:Cornus drummondii,Prunus americanaandRhus glabra. The most dominant species,Cornus drummondii, had the most extreme values for several traits, including the lowest leaf:stem mass ratios, lowest photosynthetic capacity and highest turgor loss point.Two of the most abundant species,Cornus drummondiiandRhus glabra, had opposing growth forms and resource‐use strategies. These species had significantly different above‐ground carbon allocation, leaf‐level drought tolerance and photosynthetic capacity. There were surprisingly few interspecific differences in specific leaf area and leaf dry matter content, suggesting these traits were poor predictors of species‐level encroachment.Synthesis. Woody encroaching species in tallgrass prairie encompass a spectrum of growth forms and leaf physiology. Two of the most abundant woody species fell at opposite ends of this spectrum. Our results suggest niche differences among a community of woody species facilitate the rapid encroachment by a few species. This study shows that woody encroaching species do not conform to a ‘one‐size‐fits‐all’ strategy, and a diversity of growth forms and physiological strategies may make it more challenging to reach management goals that aim to conserve or restore grassland communities. 

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