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EEOB Publications August 1 - August 31

August 8, 2022

EEOB Publications August 1 - August 31

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River phosphorus cycling during high flow may constrain Lake Erie cyanobacteria blooms

Whitney M.King, Susan E.Curless, James M.Hood. Water Research, Volume 222, 15 August 2022, 118845. https://doi.org/10.1016/j.watres.2022.118845

Abstract

Cyanobacterial harmful blooms have been increasing worldwide, due in part to excessive phosphorus (P) losses from agriculture-dominated watersheds. Unfortunately, cyanobacteria bloom management is often complicated by uncertainty associated with river P cycling. River P cycling mediates P exports during low flow but has been assumed to be unimportant during high flows. Thus, we examined interactions between dissolved reactive phosphorus (DRP) and suspended sediment P during high flows in the Maumee River network, focusing on March–June Maumee River DRP exports, which fuel recurring cyanobacteria blooms in Lake Erie. We estimate that during 2003–2019 March to June high flow events, P sorption reduced DRP exports by an average of 13–27%, depending upon the colloidal-P:DRP ratio, decreasing the bioavailability of P exports, and potentially constraining cyanobacteria blooms by 13–40%. Phosphorus sorption was likely lower during 2003–2019 than 1975–2002 due to reductions in suspended sediment loads, associated with soil-erosion-minimizing agricultural practices. This unintended outcome of erosion management has likely decreased P sorption, increased DRP exports to Lake Erie, and subsequent cyanobacteria blooms. In other watersheds, DRP–sediment P interactions during high flow could have a positive or negative effect on DRP exports; therefore, P management should consider riverine P cycles, particularly during high flow events, to avoid undermining expensive P mitigation efforts.


Assessing the Synergistic Effects of Land Use and Climate Change on Terrestrial Biodiversity: Are Generalists Always the Winners?

Colin P. Sweeney & Marta A. Jarzyna. Curr Landscape Ecol Rep (2022). https://doi.org/10.1007/s40823-022-00073-8

Abstract

Purpose of Review

There is increasing evidence that land use and land cover (LULC) change interacts with climate change to shape biodiversity dynamics. The prevailing hypothesis suggests that generalist species have an advantage in novel climatic and land cover conditions, while specialists are expected to be more sensitive to both stressors (generalization hypothesis). Some posit, however, that specialization is key to success in the face of combined climate and LULC change (specialization hypothesis). The goal of this review is to examine recent evidence for the generalization and specialization hypotheses.

Recent Findings

Recent findings at population, species, and community levels provide initial support for the generalization hypothesis—i.e., that wide niche breadths are advantageous in the face of the combined threats of climate and LULC change. Evidence for the specialization hypothesis, however, also exists. Variation among studies in terms of their geographic context, spatial and temporal extent, environmental conditions, taxonomic scope, and metrics used to quantify niche breadth is a likely factor underlying the contradictory evidence for the generalization and specialization hypotheses.

Summary

Recent research suggests that generalist species are likely able to withstand greater changes brought about by climate and LULC change than specialist species because they persist in environmental conditions that are typically further away from their thermal or resource limits. However, to fully understand factors driving species’ vulnerability to interaction of climate and LULC change, future work should adopt standardized descriptions of niche breadth, retain consistent taxonomic scope whenever possible, and provide increased replication across different geographic contexts.


Rock Climbing Disturbance Severity and Abiotic Gradients Interact to Determine Cryptogam Diversity and Community Structure

Jordan M. Reding, G. Matt Davies, Robert A. Klips. 2022. Applied Vegetation Science. https://doi.org/10.1111/avsc.12680

Abstract

Questions

Plant communities are shaped by interactions between natural and anthropogenic disturbances and underlying environmental conditions. We asked how disturbance by rock climbing alters patterns of cryptogam species diversity and composition along elevational abiotic gradients.

Location

Red River Gorge, Kentucky, United States of America

Methods

Surveying was completed within 19 climbing routes on sandstone “slabs”. Quadrats were placed at three different vertical positions (elevations) and three different horizontal positions (center of the route, route margin, off-route). The former provides a gradient of light and moisture availability while the latter corresponds to climbing impact. Cryptogam species cover was visually assessed in all quadrats. Quadrat microtopography was quantified as well as route-level Heat Load Index and Climbing Use Intensity. We assessed differences in species richness and Shannon diversity (H) among quadrat positions and evaluated differences in species and cryptogam morphological type abundance and composition.

Results

Significant differences existed in richness H, and total cryptogam abundance between quadrat vertical and horizontal positions with a significant interaction between these two factors. Cryptogram abundance was greatest in off-route quadrats and increased with elevation in such settings. Abundance was consistently lower in on-route quadrats and, here, did not change with elevation. Richness and H were greatest in off-route quadrats and declined with increasing elevation in on-route quadrats. Significant differences in community composition existed as a function of vertical and horizontal position. On-route quadrats were associated with crustose and granulose species, while foliose and squamulose lichens, and bryophytes were associated with off-route quadrats.

Conclusions

Cryptogam composition and abundance were associated with varying intra-route environmental conditions, and off-to-on route disturbance gradients. There is potential for substantive impacts on the ecology of cliff face ecosystems from climbing. Impacts could be reduced by spacing routes widely and avoiding impacts on upper elevations where diversity and abundance are greatest.


Decadal forest soil respiration following stem girdling. 

Elizabeth A. Clippard, Samuel I. Haruna, Peter S. Curtis, Cameron Clay, Ben Bond-Lamberty, Kayla Mathes, Christoph S. Vogel & Christopher M. Gough. Trees (2022). https://doi.org/10.1007/s00468-022-02340-x

Abstract

Soil respiration (Rs) represents the largest flux of carbon (C) from forests to the atmosphere, but the long-term influence of phloem-disrupting disturbance on Rs is poorly understood, limiting robust forecasts of ecosystem C balance. Using a decade of observations from the Forest accelerated succession experiment (FASET), we examined relationships among Rs, soil temperature, soil moisture, and leaf area index (LAI) following the stem girdling-induced mortality of 40% of all canopy trees within a 39-ha area. Mean annual Rs declined by about 20% relative to the control two years after disturbance, but recovered to near pre-disturbance values within five years; this reduction correlated with LAI losses and lower Rs temperature sensitivity (i.e., Q10), with the latter counteracting soil warming caused by partial canopy defoliation. These observations are consistent with progressive reductions in belowground labile C causing reductions in Rs. We conclude that the effects of stem girdling on Rs (1) were not immediate, occurring two years after the treatment, (2) were primarily influenced by biotic rather than soil microclimate changes, and (3) persisted for nearly a decade but were temporally dynamic, underscoring the value of long-term experiments.