A review of reindeer lichen (Cladonia subgenus Cladina) linear growth rates

Cladonia subgenus Cladina (the reindeer lichens) can be a dominant part of terrestrial ecosystems worldwide. They are particularly abundant in arctic-alpine and boreal regions, where they are a primary food source for woodland caribou/reindeer in winter months. Determining the growth rates of reindeer lichen is important for understanding and managing lichen regeneration following disturbances such as timber harvesting, mining, grazing, and wildfire. Regeneration and rehabilitation rates can be calculated with greater accuracy when growth rates are well understood. We provide a summary of 17 studies from 6 countries that determined the linear growth rates of three reindeer lichen groups, Cladonia arbuscula/mitis (mean = 4.7 mm/yr.), C. rangiferina/ C. stygia (mean = 5.1 mm/yr.), and C. stellaris (mean = 4.8 mm/yr.). We use linear growth rates as a proxy for over-all growth and biomass. Variables found to influence lichen growth rates are also discussed, which include light, moisture, temperature, air pollution, acid rain, precipitation, snow accumulation, substrate, age of individuals, and type of disturbance. These results can assist land managers in developing more accurate strategies for restoring lichens in disturbed areas.

Influence of Substrate Age and Interspecific Colonization on Oviposition Behavior of a Generalist Feeder, Black Soldier Fly (Diptera: Stratiomyidae), on Carrion

Variation in resource utilization plays a significant role in determining the success or failure of a species. Generalist species across numerous taxa have exhibited success in feeding strategies for a variety of reasons. This study investigated the colonization and oviposition habits of a generalist carrion-feeder, Hermetia illucens L. (Diptera: Stratiomyidae), to varying conditions of carrion decay and colonization. Oviposition treatments consisted of combinations of variably aged decaying rats, both uncolonized and colonized with a heterospecific carrion-feeder. The black soldier fly exhibited a greater preference for oviposition on aged carrion, regardless of carcass colonization status. However, when presented with the option to colonize a plant-based diet, there was a significantly greater (40.4%) oviposition response to this diet. Results of this study highlight the ability of the black soldier fly to colonize fresh or aged carrion with or without a primary colonizer present, further supporting the recognition of this species as a generalist. These data demonstrate potential inaccuracies in the utility of H. illucens as time of colonization indicator species for legal investigations, and, in some regard, can be considered an exploitative niche-specialist (i.e., relying on plant–carrion interface for immature development) when found in association with carrion.

Influence of Substrate Age on Oviposition Behavior of a Specialist Carrion Colonizer, Cochliomyia macellaria (Diptera: Calliphoridae)

The location and consumption of carrion by arthropods is a process that can be potentially distinguished temporally based on the makeup of the associated community. In fact, succession on carrion is a continuum of different generalist and specialist arthropods entering and leaving the system. Blow flies commonly associated with vertebrate remains are considered specialists due to their reliance on carrion as a source of food for offspring and protein for females. However, this specialization may come at a price; increased competition for resources and greater risk of local extinction. The present study examined the effects of the presence or absence of intraspecific colonization, carcass age, and exposure time on the colonization and oviposition responses of the specialist, primary colonizer, the secondary screw worm, Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae). Carcass age, exposure time, and colonization status significantly influenced the ovipositional response of C. macellaria. This species exhibited an oviposition preference for aged carcasses, with a tendency for higher oviposition after 8-h exposure time, but no preference between previously colonized or uncolonized carcasses. Mean egg hatch rate was also shown to be influenced by the aforementioned factors, with mean hatch rates varying between 81.26 and 90.97% across various treatments. These results provide insight into mechanisms driving succession on carrion, as well as highlight the variation observed in successional studies for the targeted species. Investigators relying on arthropod succession to indicate a time of colonization should proceed with caution in relying solely on the assumption primary colonizers only arrive and colonize fresh carrion.

Influence of Pine Bark Substrate Age on Performance and Leaching of Nursery Preemergence Herbicides

The objective of these experiments was to determine if preemergence herbicides perform similarly across pine bark that was aged for varying lengths of time including 0, 4, 8, and 12 months after bark removal from harvested trees. Three preemergence herbicides were evaluated for three separate weed species, including 1) Cardamine flexuosa With. (bittercress) with isoxaben, 2) Digitaria sanguinalis (L.) Scop. (large crabgrass) with prodiamine, and 3) Oxalis stricta L. (woodsorrel) with dimethenamid-P. Leaching of herbicides through substrates was evaluated for prodiamine. Weed growth in the various substrates was variable, but few differences were detected in weed growth among the pine bark substrates evaluated. For isoxaben and prodiamine, weed control was similar among the pine bark substrates in most cases when label rates were applied. Although some differences were detected in prodiamine performance across different pine bark ages, a high level of control was achieved in all cases at rates well below manufacturer recommendations. Prodiamine leaching was minimal in all substrates. It would be recommended that growers test substrates for physical properties before use so that irrigation and other production inputs could be modified if needed. In most cases, growers should expect similar performance of preemergence herbicides regardless of pine bark substrate age.

Effect of Substrate Age and Adhesive Composition on Dentin Bonding

SUMMARY Purpose To study the effect of dentin age and adhesive composition on the microtensile dentin bond strengths (μTBS) of five dentin adhesives. Materials and Methods Sixty extracted caries-free human teeth were assigned to the appropriate age group: less than 21 years of age (<21), 21–40 years of age (21–40), and greater than 40 years of age (>40). For each age group, specimens were randomly divided into five dentin adhesives: (1) Adper Easy Bond (EB, 3M ESPE), a one-step self-etch adhesive; (2) Experimental Adper Easy Bond without the Vitrebond Co-polymer (CP) (EBnoCP, 3M ESPE); (3) Adper Single Bond Plus (SB, 3M ESPE), a two-step etch&rinse adhesive; (4) Experimental Adper Single Bond Plus without CP (SBnoCP, 3M ESPE); and (5) Adper Scotchbond Multi-Purpose (MP, 3M ESPE), a three-step etch&rinse adhesive, as the control group. Specimens were sectioned in X and Y directions and the resulting beams were tested to failure in tension mode at a crosshead speed of 1 mm/min. Statistical analysis was computed using t-test and two-way analysis of variance followed by Fisher least significant difference multiple comparison post hoc test at p < 0.05. Results The highest mean μTBS values were obtained in the control group (MP) for all age groups. EB resulted in statistically similar mean μTBS compared to EBnoCP for all age groups: p = 0.538 for (<21); p = 0.974 for (21–40); and p = 0.909 for (>40). SB resulted in statistically higher mean μTBS than SBnoCP for all age groups [p<0.009 for (<21); p<0.028 for (21–40); and p<0.041 for (>40)]. MP, the control group, resulted in statistically lower mean μTBS when applied to the oldest age group (>40) compared to the youngest age group (<21), at p < 0.04. When means were pooled for the variable ‘age group,' SB resulted in significantly higher mean μTBS than SBnoCP at p < 0.009, while EB resulted in statistically similar mean μTBS compared to EBnoCP (p=0.9). MP resulted in statistically higher mean μTBS than all other adhesives—SB (p<0.0001), SBnoCP (p<0.0001), EBnoCP (p<0.022), and EB (p<0.046). Conclusions The substrate age influenced the bonding ability of the three-step etch&rinse adhesive. The presence of a carboxylic-based polymer (CP) enhanced the bonding ability of the two-step etch&rinse adhesive.