Abstract
BackgroundEdge effects can influence species composition and community structure as a result of changes in microenvironment and edaphic variables. We investigated effects of habitat edges on vegetation structure, abundance and body mass of one vulnerable Microcebus species in northwestern Madagascar. We trapped mouse lemurs along four 1000-m transects (total of 2424 trap nights) that ran perpendicular to the forest edge. We installed 16 pairs of 20 m2 vegetation plots along each transect and measured nine vegetation parameters. To determine the responses of the vegetation and animals to an increasing distance to the edge, we tested the fit of four alternative mathematical functions (linear, power, logistic and unimodal) to the data and derived the depth of edge influence (DEI) for all parameters.ResultsLogistic and unimodal functions best explained edge responses of vegetation parameters, and the logistic function performed best for abundance and body mass of M. ravelobensis. The DEI varied between 50 m (no. of seedlings, no. of liana, dbh of large trees [dbh ≥ 10 cm]) and 460 m (tree height of large trees) for the vegetation parameters, whereas it was 340 m for M. ravelobensis abundance and 390 m for body mass, corresponding best to the DEI of small tree [dbh < 10 cm] density (360 m). Small trees were significantly taller and the density of seedlings was higher in the interior than in the edge habitat. However, there was no significant difference in M. ravelobensis abundance and body mass between interior and edge habitats, suggesting that M. ravelobensis did not show a strong edge response in the study region. Finally, regression analyses revealed three negative (species abundance and three vegetation parameters) and two positive relationships (body mass and two vegetation parameters), suggesting an impact of vegetation structure on M. ravelobensis which may be partly independent of edge effects.ConclusionsA comparison of our results with previous findings reveals that edge effects are variable in space in a small nocturnal primate from Madagascar. Such an ecological plasticity could be extremely relevant for mitigating species responses to habitat loss and anthropogenic disturbances.
Highlights
Forest loss leading to fragmentation is the main consequence of human activities in forest ecosystems
There are three different types of ecological edge responses: (1) “positive” edge responses, (2) “neutral” edge responses, and (3) “negative” edge responses [4]
Our study focused on the vulnerable M. ravelobensis which has a limited geographic distribution in the dry deciduous forests of northwestern Madagascar [34, 35]
Summary
Forest loss leading to fragmentation is the main consequence of human activities in forest ecosystems. A variety of vegetation changes have been reported as responses to proximity to forest edges. Similar results were reported in Brazilian fragmented landscapes, with the basal area of trees being lower in proximity to the edge [6]. A study from the Thiaki Creek Nature Reserve, Australia, reported that the probability of survival of seedlings and trees was higher closer to intact forest than at the edge [8, 9], and that seedling survival was correlated to edaphic and microenvironment variables [10]. Edge effects can influence species composition and community structure as a result of changes in microenvironment and edaphic variables. To determine the responses of the vegetation and animals to an increasing distance to the edge, we tested the fit of four alternative mathemati‐ cal functions (linear, power, logistic and unimodal) to the data and derived the depth of edge influence (DEI) for all parameters
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