The effect of sudden aspen decline on understory microclimate and vegetation in southwestern Colorado

2014 ◽  
Vol 44 (8) ◽  
pp. 914-921 ◽  
Author(s):  
J.E. Korb ◽  
S. Bombaci ◽  
R. Siegel
Keyword(s):  
Soil Moisture ◽  
Populus Tremuloides ◽  
Tree Mortality ◽  
Arbuscular Mycorrhizal ◽  
Bare Soil ◽  
Understory Vegetation ◽  
Individual Species ◽  
Sudden Aspen Decline ◽  
The Individual ◽  
Branch Dieback

Sudden aspen decline (SAD), present in many parts of North America, is the sudden dieback of branches, crown loss, and rapid mortality of aspen (Populus tremuloides Michx.). We surveyed 21 plots in southwestern Colorado and categorized each plot by the mean percentage of recent crown loss (RCL) into three SAD levels: low SAD (0%–25% RCL), moderate SAD (25.1%–50% RCL), and high SAD (50.1%–100% RCL). Our research quantified the effects of SAD on microclimate and understory vegetation at the individual species and community level. Mean day surface, day subsurface, and night subsurface temperatures were warmer in high SAD stands than in low ones. High SAD stands had lower soil moisture, lower litter and duff depth, higher bare soil cover, higher photosynthetically active radiation, higher arbuscular mycorrhizal propagule densities, and higher grass biomass. Indicator plant species were uniquely associated with low and high SAD. Our study illustrates that SAD has multiple ecological effects on aspen understories, including a potential positive feedback in which warmer temperatures and decreased soil moisture, consequences of SAD, may lead to increased branch dieback and tree mortality, which would alter microclimate-making conditions more favorable to SAD and escalate the effects of SAD on understory vegetation.

Secondary insects and diseases contribute to sudden aspen decline in southwestern Colorado, USA

2011 ◽  
Vol 41 (12) ◽  
pp. 2315-2325 ◽  
Author(s):  
Suzanne Bethers Marchetti ◽  
James J. Worrall ◽  
Thomas Eager
Keyword(s):  
Populus Tremuloides ◽  
Bark Beetles ◽  
Host Susceptibility ◽  
Quaking Aspen ◽  
Contributing Factors ◽  
Invasive Ability ◽  
Attack Trees ◽  
Sudden Aspen Decline ◽  
Branch Dieback ◽  
Cytospora Canker

Reports of drought-associated forest mortality have increased around the world, but the mechanisms of mortality are rarely direct in nature. Biotic agents may kill trees that could otherwise recover and can perpetuate and expand mortality after the stress is relieved. Sudden aspen decline (SAD) has caused rapid, widespread branch dieback and mortality of quaking aspen ( Populus tremuloides Michx.). We compared insects and diseases in 162 damaged and neighboring healthy plots to determine contributing factors and their ecological roles. Cytospora canker, bronze poplar borer, and aspen bark beetles were the most common agents in damaged plots and correlated with crown loss and other factors related to SAD. This was the first documented outbreak of Trypophloeus populi , an aspen bark beetle. As bark beetles and bronze poplar borer increased in damaged stands, they tended to attack trees with healthier crowns. Environmental stress may have directly affected the success of these agents by increasing host susceptibility followed by a density-dependent increase in the insects’ invasive ability. In contrast, Cytospora canker had an identical relationship to crown loss in healthy versus damaged plots, suggesting that it was not limited by inoculum but responded to host susceptibility. Most other pathogens and insects contributed little to SAD and appear to be primary or weakening agents. The biotic agents of mortality in a decline differ greatly from primary agents and play complex and varied roles in healthy versus declining stands.

scholarly journals Gene Sequencing and Phylogenetic Analysis: Powerful Tools for an Improved Diagnosis of Fish Mycobacteriosis Caused by Mycobacterium fortuitum Group Members

2021 ◽  
Vol 9 (4) ◽  
pp. 797
Author(s):  
Davide Mugetti ◽  
Mattia Tomasoni ◽  
Paolo Pastorino ◽  
Giuseppe Esposito ◽  
Vasco Menconi ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Gene Sequencing ◽  
Diagnostic Techniques ◽  
Individual Species ◽  
Identification System ◽  
Mycobacterium Fortuitum ◽  
Biochemical Tests ◽  
Species Determination ◽  
Gene Encoding ◽  
The Individual

The Mycobacterium fortuitum group (MFG) consists of about 15 species of fast-growing nontuberculous mycobacteria (NTM). These globally distributed microorganisms can cause diseases in humans and animals, especially fish. The increase in the number of species belonging to MFG and the diagnostic techniques panel do not allow to clarify their real clinical significance. In this study, biomolecular techniques were adopted for species determination of 130 isolates derived from fish initially identified through biochemical tests as NTM belonging to MFG. Specifically, gene sequencing and phylogenetic analysis were used based on a fragment of the gene encoding the 65 KDa heat shock protein (hsp65). The analyzes made it possible to confirm that all the isolates belong to MFG, allowing to identify the strains at species level. Phylogenetic analysis substantially confirmed what was obtained by gene sequencing, except for six strains; this is probably due to the sequences present in NCBI database. Although the methodology used cannot represent a univocal identification system, this study has allowed us to evaluate its effectiveness as regards the species of MFG. Future studies will be necessary to apply these methods with other gene fragments and to clarify the real pathogenic significance of the individual species of this group of microorganisms.

scholarly journals Sensitivity Analysis of Bistatic Scattering for Soil Moisture Retrieval

2021 ◽  
Vol 13 (2) ◽  
pp. 188
Author(s):  
Tingting Li ◽  
Irena Hajnsek ◽  
Kun-Shan Chen
Keyword(s):  
Sensitivity Analysis ◽  
Soil Moisture ◽  
Quality Index ◽  
High Sensitivity ◽  
Bare Soil ◽  
Sensitivity Index ◽  
Scattering Coefficients ◽  
Observation Systems ◽  
Bistatic Scattering ◽  
Scattering Response

Soil moisture is one of the vital environmental variables in the land–atmosphere cycle. A study of the sensitivity analysis of bistatic scattering coefficients from bare soil at the Ku-band is presented, with the aim of deepening our understanding of the bistatic scattering features and exploring its potential in soil moisture retrieval. First, a well-established advanced integral method was adopted for simulating the bistatic scattering response of bare soil. Secondly, a sensitivity index and a normalized weight quality index were proposed to evaluate the effect of soil moisture on the bistatic scattering coefficient in terms of polarization and angular diversity, and the combinations thereof. The results of single-polarized VV data show that the regions with the maximum sensitivity and high quality index, simultaneously, to soil moisture are in the forward off-specular direction. However, due to the effect of surface roughness and surface autocorrelation function (ACF), the single-polarized data have some limitations for soil moisture inversion. By contrast, the results of two different polarization combinations, as well as a dual-angular simulation of one transmitter and two receivers, show significant estimation benefits. It can be seen that they all provide better ACF suppression capabilities, larger high-sensitivity area, and higher quality indices compared to single-polarized estimation. In addition, dual polarization or dual angular combined measurement provides the possibility of retrieving soil moisture in backward regions. These results are expected to contribute to the design of future bistatic observation systems.

scholarly journals Coupled stochastic dynamics of water table and soil moisture in bare soil conditions

2008 ◽  
Vol 44 (1) ◽  
Author(s):  
L. Ridolfi ◽  
P. D'Odorico ◽  
F. Laio ◽  
S. Tamea ◽  
I. Rodriguez-Iturbe
Keyword(s):  
Soil Moisture ◽  
Water Table ◽  
Stochastic Dynamics ◽  
Bare Soil ◽  
Soil Conditions

Residual Large Trees Influence Short-term Succession Following a Volcanic Eruption in a Valdivian Temperate Rainforest

2021 ◽  
Author(s):  
Lisa Hintz ◽  
Dylan Fischer ◽  
Nina Ferrari ◽  
Charlie M.S. Crisafulli
Keyword(s):  
Soil Surface ◽  
Bare Soil ◽  
Understory Vegetation ◽  
Percent Cover ◽  
Vegetative Cover ◽  
Vegetation Response ◽  
Temperate Rainforest ◽  
Large Trees ◽  
Close Proximity ◽  
Disturbed Forest

Abstract Airborne volcanic ejecta (tephra) can strongly influence forest ecosystems through initial disturbance processes and subsequent ecological response. Within a tephra-disturbed forest, large trees may promote plant growth and create favorable sites for colonization. Three primary ways trees can influence post-eruption vegetation response include: 1) amelioration of volcanic substrates, 2) as source propagules from the tree or from associated epiphytes, and 3) by sheltering understory vegetation, thereby increasing rate of recovery near tree bases. Here, we evaluate Valdivian temperate rainforest understory vegetation response and soil characteristics in close proximity to large trees that survived the 2015 eruption of Calbuco Volcano. Understory vegetative cover was higher near the base of trees for mosses, many epiphytes, and some herbaceous, shrub, and trees species. However, significant interactions with year of measurement, and individualistic responses by many species made generalizations more difficult. Small shrubs and trees in particular demonstrated patterns of recovery that were frequently independent of distance. In some cases, percent cover of colonizing vegetation actually increased far from trees by 2019. The soil surface was similarly variable where bare soil cover was associated with locations proximal to tree bases, but material shed from living and dead standing vegetation increased wood and litter abundances on the soil surface away from the base of trees. Soils near trees had lower pH, elevated organic matter, and higher nitrogen and carbon. Our results support the assertion that in this temperate rainforest ecosystem, large trees can modify edaphic conditions and provide important early refugia for vegetative regrowth following a tephra fall event. Nevertheless, complex interactions through time with species and growth form, suggest the influence of large trees on plant establishment and growth with close proximity tree boles is more complex than a simple facilitative model might suggest.

Taxonomic application of macro and micro morphological characters of seeds in Astragalus L. (Galegeae, Fabaceae) in India

Phytotaxa ◽  
2021 ◽  
Vol 502 (2) ◽  
pp. 191-207
Author(s):  
SHIVANI KASHYAP ◽  
CHANDAN KUMAR SAHU ◽  
ROHIT KUMAR VERMA ◽  
LAL BABU CHAUDHARY
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Seed Coat ◽  
Morphological Plasticity ◽  
Morphological Characters ◽  
Individual Species ◽  
Large Size ◽  
The Individual ◽  
Scanning Electron

Due to large size and enormous morphological plasticity, the taxonomy of the genus Astragalus is very complex and challenging. The identification and grouping of species chiefly based on macromorphological characters become sometimes difficult in the genus. In the present study, the micromorphology of the seeds of 30 species belonging to 14 sections of Astragalus from India has been examined applying scanning electron microscopy (SEM) along with light microscopy (LM) to evaluate their role in identification and classification. Attention was paid to colour, shape, size and surface of seeds. The overall size of the seeds ranges from 1.5–3.2 × 0.8–2.2 mm. The shape of the seeds is cordiform, deltoid, mitiform, orbicular, ovoid and reniform. The colour of seeds varies from brown to blackish-brown to black. Papillose, reticulate, ribbed, rugulate and stellate patterns were observed on the seed coat surface (spermoderm) among different species. The study reveals that the seed coat ornamentations have evolved differently among species and do not support the subgeneric and sectional divisions of the genus. However, they add an additional feature to the individual species, which may help in identification in combination with other macro-morphological features.

Larval and post-larval stages of fishes recorded from the plankton of Galway Bay, 1972–73

1976 ◽  
Vol 56 (1) ◽  
pp. 197-211 ◽  
Author(s):  
Julie M. Fives ◽  
F. I. O'Brien
Keyword(s):  
Copepod Species ◽  
Individual Species ◽  
Larval Stages ◽  
Percentage Occurrence ◽  
Bay Area ◽  
The Individual ◽  
Recorded Occurrence

The Galway Bay area was sampled quantitatively for plankton during 1972–3. The larvae and/or post-larvae of 67 species of fish were identified from the plankton. The recorded occurrence per m3 and the percentage occurrence of the individual species is presented and discussed, and reference is made to the concurrent occurrence of various chaetognath species and copepod species. The results of previous investigations of the plankton of the Galway Bay area are mentioned.

scholarly journals Species interactions in three Lemnaceae species growing along a gradient of zinc pollution

2021 ◽  
Author(s):  
Lorena Lanthemann ◽  
Sofia van Moorsel
Keyword(s):  
Growth Rates ◽  
Species Interactions ◽  
Metal Removal ◽  
Lemna Minor ◽  
Polluted Water ◽  
Future Research ◽  
Individual Species ◽  
High Tolerance ◽  
Species Mixture ◽  
The Individual

Duckweeds (Lemnaceae) are increasingly studied for their potential for phytoremediation of heavy-metal polluted water bodies. A prerequisite for metal removal, however, is the tolerance of the organism to the pollutant, e.g., the metal zinc (Zn). Duckweeds have been shown to differ in their tolerances to Zn, however, despite them most commonly co-occurring with other species, there is a lack of research concerning the effect of species interactions on Zn tolerance. Here we tested whether the presence of a second species influenced the growth rate of the three duckweed species Lemna minor, Lemna gibba, and Lemna turionifera. We used four different Zn concentrations in a replicated microcosm experiment under sterile conditions, either growing the species in isolation or in a 2-species mixture. The response to Zn differed between species, but all three species showed a high tolerance to Zn, with low levels of Zn even increasing the growth rates. The growth rates of the individual species were influenced by the identity of the competing species, but this was independent of the Zn concentration. Our results suggest that species interactions should be considered in future research with duckweeds and that several duckweed species have high tolerance to metal pollution, making them candidates for phytoremediation efforts.

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