Biology subjects

Bakker, J. D.

Publications and source records attributed to Bakker, J. D..

4 recordsLinked to original sources

bioRxiv2024

Salicaceae endophyte inoculation alters stomatal patterning and improves the intrinsic water-use efficiency of Populus trichocarpa after a water-deficit.

Microorganisms may enhance plant resilience to water stress by influencing their hosts physiology and anatomy at the leaf-level. Bacterial and yeast endophytes, isolated from wild poplar and willow, can improve the intrinsic water-use efficiency (iWUE) of cultivated poplar (Populus) under water-deficits by lowering stomatal conductance (gsw). However, the relevance of stomatal anatomy underlying this reduction remains unclear. We hypothesized endophyte inoculation could change host stomatal anatomy, and this would relate to decreases in gsw. We subjected Salicaceae endophyte-inoculated and uninoculated Populus trichocarpa to well-watered and water-deficit treatments in greenhouse studies. We examined the changes of individual stomatal traits and related the composition of these parameters, termed stomatal patterning, to leaf gas-exchange under light saturation. After a water-deficit, inoculation improved iWUE at light saturation from preserving carbon assimilation (Anet) and lowering gsw, but these changes were independent of soil-moisture status. Drops in gsw corresponded to underlying shifts in stomatal patterning. Inoculated plants had smaller, more compact stomata and greater anatomical maximum stomatal conductance (gsmax) relative to the control. Salicaceae endophytes may alter stomatal density and size, lowering gsw and increasing iWUE. Future efforts may quantify endophyte colonization of the host to draw direct relationships between microbes and stomatal traits. HIGHLIGHTPoplars inoculated with specific bacteria had leaves containing many, tiny pores relative to the trees without the microbes; these plants with the small, dense pores related to greater intrinsic water-use efficiency.

plant biology↗

bioRxiv2024

Nutrient addition in grasslands worldwide reveals proportional plant diversity decline across spatial scales but little change in beta diversity

Nutrient enrichment typically causes local plant diversity declines. A common but untested expectation is that nutrient enrichment also reduces variation in nutrient conditions among localities and selects for a smaller pool of species, causing greater diversity declines at larger than local scales and thus biotic homogenization. Here we apply a framework that links changes in species richness across scales to changes in the numbers of spatially restricted and widespread species for a standardized nutrient addition experiment across 72 grasslands on six continents. Overall, we find proportionally similar species loss at local and larger scales, suggesting similar declines of spatially restricted and widespread species, and no biotic homogenization after 4 years and up to 14 years of treatment. These patterns of diversity changes are generally consistent across species groups. Thus, nutrient enrichment poses threats to plant diversity, including for widespread species that are often critical for ecosystem functions.

ecology↗

bioRxiv2023

Multidimensional responses of ecological stability to eutrophication in grasslands

Eutrophication usually impacts biodiversity, species composition, and functioning of grassland communities. Whether such effects propagate to influence the stability of these community aspects is unknown. Using standardized experiments across 55 global grasslands, we quantified the effects of nutrient addition on five stability facets (i.e., temporal invariability and resistance during and recovery after dry and wet growing seasons) for three community aspects (i.e., aboveground biomass, community composition, and species richness). Nutrient addition reduced the temporal invariability and resistance of species richness and community composition, but not biomass, during dry and wet growing seasons. Temporal invariability and resistance during, but not recovery after, dry and wet growing seasons were strongly positively correlated in both ambient and eutrophic conditions. This indicates that maintaining and restoring the stability of plant communities requires increasing resistance rather than recovery. Harnessing the complexity of ecological stability provides new insights for grassland ecosystem sustainability in a changing world.

ecology↗

bioRxiv2022

Nutrient addition increases grassland resistance during dry and wet climate extremes despite functional diversity loss

O_LINutrient enrichment impacts grassland plant diversity such as species richness, functional trait composition and diversity, but whether and how these changes affect ecosystem stability in the face of increasing climate extremes remains largely unknown. C_LIO_LIWe quantified the direct and diversity-mediated effects of nutrient addition (by nitrogen, phosphorus, and potassium) on the stability of aboveground biomass production in 10 long-term grassland experimental sites. We measured five facets of stability as the temporal invariability, resistance during and recovery after extreme dry and wet growing seasons. C_LIO_LILeaf traits (leaf carbon, nitrogen, phosphorus, potassium, and specific leaf area) were measured under ambient and nutrient addition conditions in the field and were used to construct the leaf economic spectrum (LES). We calculated functional trait composition and diversity of LES and of single leaf traits. We quantified the contribution of intraspecific trait shifts and species replacement to change in functional trait composition as responses to nutrient addition and its implications for ecosystem stability. C_LIO_LINutrient addition decreased functional trait diversity and drove grassland communities to the faster end of the LES primarily through intraspecific trait shifts, suggesting that intraspecific trait shifts should be included for accurately predicting ecosystem stability. Moreover, the change in functional trait diversity of the LES in turn influenced different facets of stability. That said, these diversity-mediated effects were overall weak and/or overwhelmed by the direct effects of nutrient addition on stability. As a result, nutrient addition did not strongly impact any of the stability facets. These results were generally consistent using individual leaf traits but the dominant pathways differed. Importantly, major influencing pathways differed using average trait values extracted from global trait databases (e.g. TRY). C_LIO_LISynthesis. Investigating changes in multiple facets of plant diversity and their impacts on multidimensional stability under global changes such as nutrient enrichment can improve our understanding of the processes and mechanisms maintaining ecosystem stability. C_LI

ecology↗