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Effects of forest fire and drought on acidity of a base-poor boreal forest stream: similarities between climatic warming and acidic precipitation (1992)

Bayley, S. E. ; Schindler, D. W. ; Parker, B. R. ; [et al.]

Springer

Biodegradation 17 (1992), S. 191-204

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ISSN: 1572-9729

Keywords: fire ; climate change ; boreal forest ; stream ; sulfate ; acidity ; watershed

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract In a boreal forest catchment in the Experimental Lakes Area in northwestern Ontario, wildfire caused an increase in the concentrations of strong acid anions and base cations of the stream. In the naturally base-poor Northwest (NW) Subbasin, a 1980 wildfire caused exports of strong acid anions to increase more than export of base cations, causing a 2.5 fold increase in the acidity of the stream. Mean annual stream pH declined from 5.15 prior to fire to 4.76 two years after fire. Acid-neutralizing capacity (ANC), calculated as the difference between total base cations and strong acid anions, decreased to 20% of pre-fire values. Sulfate and chloride were the strong acid anions responsible for the decline in ANC, increasing four-fold. While nitrate increased eleven-fold, concentrations were too low to significantly affect ANC. There was a significant correlation between weekly sulfate concentration and base cation concentration (r 2 = 0.83) in the two years after fire. Recovery of ANC was caused by the more rapid decline in concentration of sulfate than by changes in base cations. Drought produced a similar but weaker response than fire, with increased sulfate concentrations and decreased stream pH. Climatic warming that increases drought and fire frequency would have effects that mimic the impacts of acidic precipitation (i.e. higher sulfate concentrations and acidic stream waters). Areas which have higher concentrations of stored S from past acid precipitation or have large areas of peatlands in the watershed may have aggravated losses of S and H+ after drought and fire.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00004041

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Parasitoids in low-level populations ofLymantria dispar [Lep.: Lymantriidae] in different forest physiographic zones (1993)

Skinner, Margaret ; Parker, B. L. ; Wallner, W. E. ; [et al.]

Springer

BioControl 38 (1993), S. 15-29

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ISSN: 1573-8248

Keywords: Insecta ; gypsy moth ; parasitism ; low-level host populations ; Compsilura concinnata

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Description / Table of Contents: Résumé Une étude a été menée pendant 2 ans sur la distribution des parasitoïdes deLymantria dispar (L.) dans une forêt du Vermont, dans la zone mésique, dans la zone de transition adjacente d'altitude plus élevée et dans la zone xérique. Dans chaque habitat, le parasitisme varie de 12 à 18% au cours des 2 années. Quand l'analyse est faite en fonction du stade de développement auquel l'hôte est récolté, les taux de parasitisme de plus de 40% sont observés sur les stades les plus âgés.Parasetigena silvestris (Robineau-Desvoidy) etPhobocampe disparis (Viereck) sont obtenus plus fréquemment dans l'habitat mésique alors queCotesia melanoscelus (Ratzeburg) etBlepharipa pratensis (= Sturmia scutellata) (Meigen) sont mieux représentés dans les récoltes provenant des zones xériques. Le parasitisme parCompsilura concinnata (Meigen) atteint des niveaux similaires dans les 3 habitats, cette espèce étant responsable des plus forts taux de parasitisme, qui s'élevait jusqu'à 40% dans les derniers stades en 1985. Le taux de parasitisme dû àC. concinnata a augmenté 3 à 4 fois de 1984 à 1985, alors que le parasitisme par les autres espèces diminuait.

Notes: Abstract A 2-year study was conducted on the distribution of parasitoids of gypsy moth,Lymantria dispar (L.) (Lep.: Lymantriidae), in mesic and adjacent higher elevation transition and xeric forest habitats in Vermont (U.S.A.). In both years, overall parasitism ranged from 12–18% in each habitat. When analyzed according to the life stage at which the host was collected, parasitism rates of greater than 40% were obtained among the late instars.Parasetigena silvestris (Robineau-Desvoidy) andPhobocampe disparis (Viereck) were recovered most commonly from the mesic habitat, andCotesia melanoscelus (Ratzeburg) andBlepharipa pratensis (= Sturmia scutellata) (Meigen) were most common in collections from the xeric area. Parasitism byCompsilura concinnata (Meigen) occurred at similar levels in all three habitats, and this species was responsible for the highest parasitism rates on the site, reaching 40% among the late instars in 1985. Percent parasitism byC. concinnata increased three-four-fold from 1984 to 1985, while parasitism by other species declined.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02373135

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