Boulanger2010

Référence

Boulanger, Y. (2010) Colonisation initiale des coléoptères saproxyliques et décomposition des débris ligneux grossiers d'épinette noire après feu en milieu boréal. Thèse de doctorat, Université du Québec à Rimouski. (URL )

Résumé

In this thesis, l explored i) the initial colonization of post-tire black spruce (Picea mariana [Mill.] B.S .P) coarse woody debris (CWD) by saproxylic beetles and ii) the factors responsible of the decomposition rates of this woody substrate in the northern boreal forest of Québec. Up to date, this study is the tirst to concurrently study both of these processes in a post-tire context. It takes advantage of a unique sampling design where in sect traps were put as soon as seven days after tire. This sampling design along with the one used to study the decomposition of CWD were established over large territories which al\owed us to coyer a great range of variability in post-tire conditions as weIl as to consider several spatial scales. This study outlined the importance of tire severity to shape the colonization pattern of saproxylic beetles. Moreover, these spatial patterns suppose that early post-tire saproxylic species have great dispersal abilities. In addition to colonization patterns, fire seve rit y greatly affected the decomposition ofCWD. Burned habitat characteristics greatly affected the colonization pattern of saproxylic species. Among aIl predictors, tire severity had the greatest impact which was significant at several spatial scales for both adults and neonates. Overall, adult predators and xylophages were more abundant in severely burned stands and landscapes whereas tires severity had the opposite effect on mycophages. The importance of fire severity in this process must be directly related to the nutritional and reproductive quality of the substrate. In that sense, a higher abundance of xylophagous adults in severely burned landscape is a counterintuitive result. In fact, xylophagous neonates were most abundant in lightly burned trees, presumably as a result of higher moisture content in the subcortical tissus. Such result suggests a nonoptimal colonization strategy for several xylophagous species. Even if speculative, this may the result of an evolutionary pressure that mostly pu shed species to detect and use a more temporarily and spatially stable substrate, i.e. fresh CWD produced in unburned forests. When converging towards the burned patches, species may have used to same volatiles than those emitted by dead trees in green forests; consequently, adults immigrate mostly in severely burned landscapes where the se volatiles should be more abundant. Despite this non-optimal strategy, we suggested that the use of burns represents a reproductive opportunity, rather than the panacea, for xylophagous species considering the great amount of available substrate. Furthermore, the immigration towards severely burned landscape implies the perception of environmental characteristics at a large spatial scale. Nonetheless, burned habitat characteristics measured at the plot level were also very important to shape the colonization pattern. This multi-scale pattern was caused by dispersal from distant source habitats towards the burned substrate used for reproductive or feeding purpose. On the other hand, distance to potential source habitats had very little or no negative effect on the ability of a saproxylic species to reach the habitat to colonize. The abundance of only few mycophagous species decreased as a function of distance to recent burns. The absence of such negative effect of distance to source habitats may be caused by the presumably great dispersal ability of most early saproxylic species. In addition to colonization patterns, tire severity had a considerable impact on the decomposition rate of the woddy substrate. OveralI, these rates (k = 0.013) were relatively low wh en compared to those observed for similar taxa in similar ecosystems. Fire severity had a strong negative effect on decomposition rates mostly by speeding bark shedding and moisture loss as weIl as by slowing the fragmentation of snags. Low decomposition rates in severely burned trees may also resulted from a reduced comminutive activity ofxylophagous species.

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@PHDTHESIS { Boulanger2010,
    AUTHOR = { Boulanger, Y. },
    TITLE = { Colonisation initiale des coléoptères saproxyliques et décomposition des débris ligneux grossiers d'épinette noire après feu en milieu boréal },
    SCHOOL = { Université du Québec à Rimouski },
    YEAR = { 2010 },
    NOTE = { CEFTMS, Sirois, L. and Nozais, C. },
    ABSTRACT = { In this thesis, l explored i) the initial colonization of post-tire black spruce (Picea mariana [Mill.] B.S .P) coarse woody debris (CWD) by saproxylic beetles and ii) the factors responsible of the decomposition rates of this woody substrate in the northern boreal forest of Québec. Up to date, this study is the tirst to concurrently study both of these processes in a post-tire context. It takes advantage of a unique sampling design where in sect traps were put as soon as seven days after tire. This sampling design along with the one used to study the decomposition of CWD were established over large territories which al\owed us to coyer a great range of variability in post-tire conditions as weIl as to consider several spatial scales. This study outlined the importance of tire severity to shape the colonization pattern of saproxylic beetles. Moreover, these spatial patterns suppose that early post-tire saproxylic species have great dispersal abilities. In addition to colonization patterns, fire seve rit y greatly affected the decomposition ofCWD. Burned habitat characteristics greatly affected the colonization pattern of saproxylic species. Among aIl predictors, tire severity had the greatest impact which was significant at several spatial scales for both adults and neonates. Overall, adult predators and xylophages were more abundant in severely burned stands and landscapes whereas tires severity had the opposite effect on mycophages. The importance of fire severity in this process must be directly related to the nutritional and reproductive quality of the substrate. In that sense, a higher abundance of xylophagous adults in severely burned landscape is a counterintuitive result. In fact, xylophagous neonates were most abundant in lightly burned trees, presumably as a result of higher moisture content in the subcortical tissus. Such result suggests a nonoptimal colonization strategy for several xylophagous species. Even if speculative, this may the result of an evolutionary pressure that mostly pu shed species to detect and use a more temporarily and spatially stable substrate, i.e. fresh CWD produced in unburned forests. When converging towards the burned patches, species may have used to same volatiles than those emitted by dead trees in green forests; consequently, adults immigrate mostly in severely burned landscapes where the se volatiles should be more abundant. Despite this non-optimal strategy, we suggested that the use of burns represents a reproductive opportunity, rather than the panacea, for xylophagous species considering the great amount of available substrate. Furthermore, the immigration towards severely burned landscape implies the perception of environmental characteristics at a large spatial scale. Nonetheless, burned habitat characteristics measured at the plot level were also very important to shape the colonization pattern. This multi-scale pattern was caused by dispersal from distant source habitats towards the burned substrate used for reproductive or feeding purpose. On the other hand, distance to potential source habitats had very little or no negative effect on the ability of a saproxylic species to reach the habitat to colonize. The abundance of only few mycophagous species decreased as a function of distance to recent burns. The absence of such negative effect of distance to source habitats may be caused by the presumably great dispersal ability of most early saproxylic species. In addition to colonization patterns, tire severity had a considerable impact on the decomposition rate of the woddy substrate. OveralI, these rates (k = 0.013) were relatively low wh en compared to those observed for similar taxa in similar ecosystems. Fire severity had a strong negative effect on decomposition rates mostly by speeding bark shedding and moisture loss as weIl as by slowing the fragmentation of snags. Low decomposition rates in severely burned trees may also resulted from a reduced comminutive activity ofxylophagous species. },
    OWNER = { amriv2 },
    TIMESTAMP = { 2012.04.04 },
    URL = { http://semaphore.uqar.ca/525/ },
}

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