Search

Background Recent studies showed a connection between pyrodiversity and biodiversity in the western US, but few examined bird response to fire severity in eastern hardwood forests. We measured forest structure and conducted avian point counts for five years (2016–2021; Y1-Y5) in three burned and three unburned watersheds following mixed-severity wildfires to compare breeding bird communities across a fire-severity gradient (no burn (NB), low (L), low-moderate (LM), moderate (M), moderate-high (MH), and high (H)) in the southern Appalachian region. Results The percentage of wildfire-killed trees increased with fire-severity category (FSC) and over time; by Y5, 74% (48% BA) were dead in H compared to 11% (3% BA) in L. Post-wildfire shrub recovery was rapid, especially in H and MH where cover exceeded all other FSCs by Y5. Total bird abundance and species richness increased with increasing fire severity (no change in NB and L) and exceeded all other FSCs in H and MH by Y5. Most (12 of 18 tested) species were unaffected by wildfire severity. Disturbance-dependent chestnut-sided warbler (Setophaga pensylvanica), indigo bunting (Passerina cyanea), and eastern towhee (Pipilo erythrophthalmus) increased in H within 3–4 years; white-breasted nuthatch (Sitta carolinensis), hooded warbler (Setophaga citrina), and blue-headed vireo (Vireo solitarius) increased in some burned FSCs and years. Shrub-nesters were more abundant in H than all other FSCs except MH and increased over time in H, MH and LM. Cavity-nesters were more abundant in H, MH and M than L or NB, but primary cavity-nesters (woodpeckers) alone were not. Conclusions Our results highlight the interrelated roles of fire severity and time in driving breeding bird response in central hardwood forests, illustrated by sharp contrasts in bird responses between L (no effects) and higher-severity (H and MH) burns that promoted disturbance-dependent species, but also a more gradual increase in total bird abundance and species richness in LM and M corresponding with delayed tree mortality and shrub recovery. We suggest that high-severity burns are more important than pyrodiversity per se in promoting bird diversity, as disturbance-dependent species were mainly associated with high-severity burns whereas no species was limited to unburned forests or lower-severity burns (L-M).

In this study, we have looked for an optimum media glucose concentration and compared glucose consumption in three vascular cell types, endothelial cells (ECs), vascular smooth muscle cells (VSMCs), and adventitial fibroblasts (AFs) with or without angiotensin II (AngII) stimulation. In a subconfluent 6-well experiment in 1 mL DMEM with a standard low (100 mg/dL), a standard high (450 mg/dL), or a mixed middle (275 mg/dL) glucose concentration, steady and significant glucose consumption was observed in all cell types. After 48-h incubation, media that contained low glucose was reduced to almost 0 mg/dL, media that contained high glucose remained significantly higher at ∼275 mg/dL, and media that contained middle glucose remained closer to physiological range. AngII treatment enhanced glucose consumption in AFs and VSMCs but not in ECs. Enhanced extracellular acidification rate by AngII was also observed in AFs. In AFs, AngII induction of target proteins at 48 h varied depending on the glucose concentration used. In low glucose media, induction of glucose regulatory protein 78 or hexokinase II was highest, whereas induction of VCAM-1 was lowest. Utilization of specific inhibitors further suggests essential roles of angiotensin II type-1 receptor and glycolysis in AngII-induced fibroblast activation. Overall, this study demonstrates a high risk of hypo- or hyperglycemic conditions when standard low or high glucose media is used with vascular cells. Moreover, these conditions may significantly alter experimental outcomes. Media glucose concentration should be monitored during any culture experiments and utilization of middle glucose media is recommended for all vascular cell types.