Mycorrhizae in the Alaska Landscape

This publication explains how mycorrhiza, an important relationship between plant roots and certain types of fungi, can improve the plant's growth and provide protection from certain root diseases.For more information, contact your local Cooperative Extension Service office or Jeff Smeenk, Extension Horticulture Specialist, Agriculture and Horticulture, at 907-746-9470 or [email protected]. Reviewed by Stephen Brown and Robert Gorman, Extension Faculty, Agriculture and Horticulture, and Jodie Anderson, Instructor, School of Natural Resources and Agricultural Science

Perturbation dynamics of a planktonic ecosystem

Planktonic ecosystems provide a key mechanism for the transfer of carbon from the atmosphere to the deep ocean via the so-called biological pump. Mathematical models of these ecosystems have been used to predict CO2 uptake in surface waters at particular locations, and more recently have been embedded in global climate models. While the equilibrium properties of these models are well studied, less attention has been paid to their response to external perturbations, despite the fact that as a result of the variability of environmental forcing such ecosystems are rarely, if ever, in equilibrium. In this study, linear theory is used to determine the structure of perturbations to state variables of an ecosystem model describing summertime conditions at Ocean Station P (50°N 145°W) that maximize either instantaneous or integrated export flux. As a result of the presence of both direct and indirect pathways to export in this model, these perturbations involve the dynamics of the entire ecosystem. For all optimal perturbations considered, it is found that the flux to higher trophic levels is the primary contributor to export flux, followed by sinking detritus. In contrast, the contribution of aggregation is negligible. In addition, small phytoplankton contribute significantly (comparable to large phytoplankton) to the export flux through indirect pathways, primarily through the microzooplankton, even following a bloom in only large phytoplankton. While the details of these results may be specific to the particular model under consideration, the optimal perturbation framework is general and can be used to probe the dynamics of any mechanistic ecosystem model

A data science approach to understanding physical drivers of coastal primary productivity and effects on carbonate chemistry

How do ocean mixing regimes influence primary productivity and carbon dynamics? Primary productivity is a key quantity in the quality of habitat for higher trophic levels including larval salmon. Here, we analyze the physical oceanographic and primary productivity dynamics of the Salish Sea using the output of SalishSeaCast, a newly-developed biophysical model based on the NEMO framework (Olson et al, in preparation). The biophysical model estimates three classes of primary producers - diatoms, small flagellates and Mesodynium rubrum. Here, we consider daily depth-integrated biomass signals for all three organismal classes extracted from the model domain over the course of two years, as well as daily signals of halocline depth, river input, wind energy, and tidal mixing. These signals are then analyzed using a normalized hierarchical clustering approach. The analysis shows large biomass variance (~2 orders of magnitude) throughout the model domain, and clear spatial patterns in biomass correspond to regions dominated by different mixing and stratification regimes. The signal clusters demonstrate a clear boundary between the biomass patterns in the Northern and Southern Strait of Georgia, and offer a physical explanation for the difference. We then compare this output to carbonate chemistry data and the developing carbonate chemistry numerical model, to gain insight into biophysical drivers of carbonate chemistry distribution in different regions of the Strait. The study represents the first attempt at a large-scale statistical analysis of the newly-developed model, and demonstrates the unique utility of this approach in identifying discrete regions governed by various primary productivity regimes, and provides a framework for considering their effects on carbonate chemistry. In the future, such an analysis may be used to understand the impact of shifting stratification and mixing regimes on the interaction of primary productivity and carbonate chemistry under anthropogenic climate change

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

Ocean acidification threatens to reduce pH and aragonite saturation state (ΩA) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and ΩA in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and ΩA to river TA and DIC using a coupled biogeochemical model of the Strait of Georgia on the Canadian Pacific coast and place the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA observations from this river plume and pH from the river mouth, we find that the Fraser is moderately alkaline (TA 500–1000 µmol kg−1) but relatively DIC-rich. Model results show that estuarine pH and ΩA are sensitive to freshwater DIC and TA, but do not vary in synchrony except at high DIC : TA. The asynchrony occurs because increased freshwater TA is associated with increased DIC, which contributes to an increased estuarine DIC : TA and reduces pH, while the resulting higher carbonate ion concentration causes an increase in estuarine ΩA. When freshwater DIC : TA increases (beyond  ∼  1.1), the shifting chemistry causes a paucity of the carbonate ion that overwhelms the simple dilution/enhancement effect. At this high DIC : TA ratio, estuarine sensitivity to river chemistry increases overall. Furthermore, this increased sensitivity extends to reduced flow regimes that are expected in future. Modulating these negative impacts is the seasonal productivity in the estuary which draws down DIC and reduces the sensitivity of estuarine pH to increasing DIC during the summer season

Evaluation of Particular Mulches as Plant Growth Media and Erosion Inhibitors

Introduction: Increasing public awareness of the desireability of protecting the environment from soil erosion caused by wind and water has centered attention on large construction projects such as highways and housing subdivisions, as well as on individual building sites and parking lots. If unattended, sediment produced from these areas pollutes surface water, restricts drainage, fills reservoirs, damages adjacent land, and upsets the natual ecology of lakes and streams. The search continues for products and practices that will prevent or lessen the amount of sediment leaving construction sites. Products currently in use include chemical as well as organic materials, and they are applied with varying degrees of success. Many designed to stabilize the unprotected soil for a long enough period of time for vegetation to become established are in wide use and are quite effective (Clyde et al. 1978). Moreover, applying organic material to the soil surface around shallow-rooted crops has been a cultural practice for many years (Russell 1961). Janick (1963) summarized the effects of mulching as conservation of soil moisture, reduction of surface runoff and erosion, reduction of evaporation, and possible control of weeds. Others (Borst and Woodburn 1942; Duley 1939) have indicated the value of mulches in reducing runoff and erosion. Mulching has been reported as superior to other treatments for reducing soil and water losses and stabilizing bare slopes before grass is established (Swanson et al. 1965). Gilbert and Davis (1967) and Blaser (1962), in studies of highway slopes stabilization, found mulches improved seed germination and seedling growth by conserving moisture and protecting highway slopes against erosion. Many materials have been evaluated for use as a mulch, including bark, wood wastes, soybean residues, wheat straw, and seawee (Bollen and Glennie 1961; Kidder at al, 1943; Latimer and Percival 1947). McKee et al. (1964) found wheat straw to be one of the best mulches, particularly when used to aid vegetation establishment on steep cut slopes of highways. Osborne and Gilbert (1978) also demonstrated that shredded hardwood bark mulch provided adequate erosion control on highway slopes. CONWED Corporation produces and markets wood fiber mulches that are intended to foster plant growth and inhibit erosion. The objective of this study was to evaluate, using simulated rainfall and sunlight, the effectiveness of various fiber mulches for controlling erosion to facilitate the establishment and growth of barley on a 2:1 (50 percent) slope

Concentrations and cycling of DMS, DMSP, and DMSO in coastal and offshore waters of the Subarctic Pacific during summer, 2010-2011

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 3269–3286, doi:10.1002/2016JC012465.Concentrations of dimethylsulfide (DMS), measured in the Subarctic Pacific during summer 2010 and 2011, ranged from ∼1 to 40 nM, while dissolved dimethylsulfoxide (DMSO) concentrations (range 13-23 nM) exceeded those of dissolved dimethyl sulfoniopropionate (DMSP) (range 1.3–8.8 nM). Particulate DMSP dominated the reduced sulfur pool, reaching maximum concentrations of 100 nM. Coastal and off shore waters exhibited similar overall DMS concentration ranges, but sea-air DMS fluxes were lower in the oceanic waters due to lower wind speeds. Surface DMS concentrations showed statistically significant correlations with various hydrographic variables including the upwelling intensity (r2 = 0.52, p < 0.001) and the Chlorophyll a/mixed layer depth ratio (r2 = 0.52, p < 0.001), but these relationships provided little predictive power at small scales. Stable isotope tracer experiments indicated that the DMSP cleavage pathway always exceeded the DMSO reduction pathway as a DMS source, leading to at least 85% more DMS production in each experiment. Gross DMS production rates were positively correlated with the upwelling intensity, while net rates of DMS production were significantly correlated to surface water DMS concentrations. This latter result suggests that our measurements captured dominant processes driving surface DMS accumulation across a coastal-oceanic gradient.Natural Sciences and Engineering Research Council of Canada, from the Peter Wall Institute for Advanced Studies2017-10-2

Estimating marine carbon uptake in the northeast Pacific using a neural network approach

The global ocean takes up nearly a quarter of anthropogenic CO2 emissions annually, but the variability in this uptake at regional scales remains poorly understood. Here we use a neural network approach to interpolate sparse observations, creating a monthly gridded seawater partial pressure of CO2 (pCO2) data product from January 1998 to December 2019, at 1/12∘ × 1/12∘ spatial resolution, in the northeast Pacific open ocean, a net sink region. The data product (ANN-NEP; NCEI Accession 0277836) was created from pCO2 observations within the 2021 version of the Surface Ocean CO2 Atlas (SOCAT) and a range of predictor variables acting as proxies for processes affecting pCO2 to create nonlinear relationships to interpolate observations at a spatial resolution 4 times greater than leading global products and with better overall performance. In moving to a higher resolution, we show that the internal division of training data is the most important parameter for reducing overfitting. Using our pCO2 product, wind speed, and atmospheric CO2, we evaluate air–sea CO2 flux variability. On sub-decadal to decadal timescales, we find that the upwelling strength of the subpolar Alaskan Gyre, driven by large-scale atmospheric forcing, acts as the primary control on air–sea CO2 flux variability (r2=0.93, p&lt;0.01). In the northern part of our study region, divergence from atmospheric CO2 is enhanced by increased local wind stress curl, enhancing upwelling and entrainment of naturally CO2-rich subsurface waters, leading to decade-long intervals of strong winter outgassing. During recent Pacific marine heat waves from 2013 on, we find enhanced atmospheric CO2 uptake (by as much as 45 %) due to limited wintertime entrainment. Our product estimates long-term surface ocean pCO2 increase at a rate below the atmospheric trend (1.4 ± 0.1 µatm yr−1) with the slowest increase in the center of the subpolar gyre where there is strong interaction with subsurface waters. This mismatch suggests the northeast Pacific Ocean sink for atmospheric CO2 may be increasing.</p