Abstract:The O horizon, or detrital layer, of forest soils is linked to long-term forest productivity and health. Fuel reduction techniques, such as prescribed fire, can alter the thickness and composition of this essential ecosystem component. Developing an understanding of the changes in the chemical composition of forest detritus due to prescribed fire is essential for forest managers and stakeholders seeking sustainable, resilient, and productive ecosystems. In this study, we evaluated fuel quantity, fuel structure… Show more
“…Additional studies at other long-term, unburned locations in this region would undoubtedly improve interpretations and expand the scope of inferences. However, these data do support the findings of Coates et al [58], which concluded that the frequent, prescribed, low-intensity, low-severity, surface fires at Yawkey did not significantly alter the chemical composition of forest floor materials. The chemical functional groups, including selected polycyclic aromatic hydrocarbons (PAHs), of both burned and unburned litter and duff, showed little to no alteration as a result of prescribed fire.…”
Recent studies suggest increased fire frequency may impair soil chemistry, but few studies have examined long-term effects of repeated, frequent prescribed fires on forest soil properties in the southeastern Coastal Plain, USA. In this study, forest soil chemistry at the 0–10 and 10–20 cm mineral soil depths of sandy surface horizons (Entisols and Spodosols) were compared among units burned 0, 4, 6, and 8 times between 2004 and 2015 and 0 and 20 times between 1978 and 2015 in a longleaf (Pinus palustris Mill.)–loblolly (Pinus taeda L.) pine savanna at the Tom Yawkey Wildlife Center (Georgetown, SC, USA). At the 0–10 cm soil depth, soil pH (p = 0.00), sulfur (p = 0.01), calcium (p = 0.01), iron (p < 0.01), manganese (p < 0.01), and aluminum (p = 0.02) treatment means differed (2004–2015). Calcium and manganese displayed positive, significant relationships and sulfur displayed a negative, significant relationship with increasing fire frequency (p < 0.05). However, correlation of these relationships was low (r2 ≤ 0.23). Using linear contrasts to compare the mean of all fire treatments (20 fires from 1978 to 2015) to the mean of the unburned compartment, sulfur (p = 0.01) and iron (p < 0.01) were less in soils from the burned compartments. At the 10–20 cm soil depth, soil pH (p = 0.01), manganese (p = 0.04), phosphorus (p = 0.01), potassium (p = 0.02), and iron (p < 0.01) treatment means differed (2004–2015). Potassium displayed a negative, significant relationship and soil pH displayed a positive, significant relationship with increasing fire frequency (p < 0.05). Correlation of these relationships was low (r2 ≤ 0.16), however. Using linear contrasts to compare the mean of all fire treatments (20 fires from 1978 to 2015) to the unburned compartment, potassium (p = 0.00) and iron (p < 0.01) were less in soils from burned compartments. These results are inconsistent with studies suggesting that forest soil chemistry is substantially altered by increased fire frequency and support other studies from this region that have documented minimal or temporary soil chemical changes associated with frequent prescribed fires.
“…Additional studies at other long-term, unburned locations in this region would undoubtedly improve interpretations and expand the scope of inferences. However, these data do support the findings of Coates et al [58], which concluded that the frequent, prescribed, low-intensity, low-severity, surface fires at Yawkey did not significantly alter the chemical composition of forest floor materials. The chemical functional groups, including selected polycyclic aromatic hydrocarbons (PAHs), of both burned and unburned litter and duff, showed little to no alteration as a result of prescribed fire.…”
Recent studies suggest increased fire frequency may impair soil chemistry, but few studies have examined long-term effects of repeated, frequent prescribed fires on forest soil properties in the southeastern Coastal Plain, USA. In this study, forest soil chemistry at the 0–10 and 10–20 cm mineral soil depths of sandy surface horizons (Entisols and Spodosols) were compared among units burned 0, 4, 6, and 8 times between 2004 and 2015 and 0 and 20 times between 1978 and 2015 in a longleaf (Pinus palustris Mill.)–loblolly (Pinus taeda L.) pine savanna at the Tom Yawkey Wildlife Center (Georgetown, SC, USA). At the 0–10 cm soil depth, soil pH (p = 0.00), sulfur (p = 0.01), calcium (p = 0.01), iron (p < 0.01), manganese (p < 0.01), and aluminum (p = 0.02) treatment means differed (2004–2015). Calcium and manganese displayed positive, significant relationships and sulfur displayed a negative, significant relationship with increasing fire frequency (p < 0.05). However, correlation of these relationships was low (r2 ≤ 0.23). Using linear contrasts to compare the mean of all fire treatments (20 fires from 1978 to 2015) to the mean of the unburned compartment, sulfur (p = 0.01) and iron (p < 0.01) were less in soils from the burned compartments. At the 10–20 cm soil depth, soil pH (p = 0.01), manganese (p = 0.04), phosphorus (p = 0.01), potassium (p = 0.02), and iron (p < 0.01) treatment means differed (2004–2015). Potassium displayed a negative, significant relationship and soil pH displayed a positive, significant relationship with increasing fire frequency (p < 0.05). Correlation of these relationships was low (r2 ≤ 0.16), however. Using linear contrasts to compare the mean of all fire treatments (20 fires from 1978 to 2015) to the unburned compartment, potassium (p = 0.00) and iron (p < 0.01) were less in soils from burned compartments. These results are inconsistent with studies suggesting that forest soil chemistry is substantially altered by increased fire frequency and support other studies from this region that have documented minimal or temporary soil chemical changes associated with frequent prescribed fires.
“…(C6), 124·98 (C4), 121·85 (C1), 111·46 (C3) and 108·89 (C2). In accordance with published studies (Coates et al ), compound 2 was identified as 1H‐Pyrrole‐2‐carboxamide . …”
Aims
To extract and identify the metabolites of strain A217 as well as its antifungal spectrum and control effect on various plant pathogens.
Methods and Results
Strain A217 was identified as a Streptomyces sp. which was most similar to Streptomyces lienomycini. An antimicrobial spectrum test indicated that strain A217 inhibited several plant pathogenic fungi and strong antibacterial effect such as Phytophthora capsici, Botrytis cinerea, Sclerotinia sclerotiorum, Fusarium oxysporum, Pseudomonas syringae and Xanthomonas campestris. An in vivo tissue test demonstrated that the fermentation broth of strain A217 exerted therapeutic and protective effects of 49·47 and 61·60% respectively, on S. sclerotiorum. Additionally, the fermentation broth of A217 exerted control effects on walnut black spot disease in walnut leaves and branches amounting to 79·33 and 81·52% respectively. In a pot experiment, the fermentation broth exhibited a stronger protective and control effect (68·29%), as well as better bacteriostatic and disease control effects on Phytophthora blight of pepper, compared with Metalaxyl. Compounds possessing antifungal and antibacterial activities were obtained from the fermentation broth of strain A217, using column chromatography and HPLC. Chemical and structural analyses conducted using MS and nuclear magnetic resonance confirmed that these compounds were 1H‐pyrrole‐2‐carboxylic acid and 1H‐pyrrole‐2‐carboxamide. The EC50 values of compound 1H‐pyrrole‐2‐carboxylic acid1 for S. sclerotiorum and P. capsici were 20·13 and 50·36 μg ml−1 respectively. Compound 1H‐pyrrole‐2‐carboxamide2 showed significant antibacterial activity against different plant pathogenic bacteria. The MIC values of P. syringae, X. campestris and X. campestris pv. jugiandis were 7·5, 30 and 15·0 μg ml−1 respectively.
Conclusions
Actinomyces A217 fermentation products have a broad spectrum of bacteriostasis, and have good bacteriostasis activity to many plant pathogenic fungi and bacteria.
Significance and Impact of the Study
The present study revealed a new antimicrobial producing strain of Streptomyces and its potential application as a biological control agent for plant diseases.
“…The laboratory extraction study confirmed this hypothesis as well; aromaticity of the DOM leaching from vegetation was not significant between the two watersheds (Table 2). This agrees with previous studies suggesting that low-intensity prescribed fire may not significantly change DOM composition and only high-intensity fire results in increased DOM aromaticity (Wang et al 2015;Coates et al 2017;Hahn et al 2019).…”
Watershed management practices such as prescribed fire, harvesting and understory mastication can alter the chemical composition and thickness of forest detritus, thus affecting the quantity and quality of riverine dissolved organic matter (DOM). Long-term effects of watershed management on DOM composition were examined through parallel field and extraction-based laboratory studies. The laboratory study was conducted using detritus samples collected from a pair of managed and unmanaged watersheds in South Carolina, USA. Results showed that dissolved organic carbon (DOC), total dissolved nitrogen (TDN) and ammonium (NH4+-N) concentrations were higher in water extracts from the unmanaged watershed than from the managed watershed (P<0.01). Pyrolysis gas chromatography–mass spectrometry analysis showed that water extracts from the unmanaged watershed contained more aromatic compounds than extracts from the managed watershed. For the field study, monthly water samples were collected for 1 year (2015) from the paired watersheds. DOC and TDN concentrations, as well as DOM aromaticity, were significantly higher in the unmanaged watershed than in the managed watershed for most of the year (P<0.05) and were linked to detrital thickness, precipitation and flow patterns. The formation potential of two regulated disinfection by-products was lower in the unmanaged watershed for most of 2015 (P<0.05). From this study, it appears that long-term watershed management practices may alter detrital mass and chemistry in ways that improve water quality.
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