The effects of habitat age in the surrounding landscape on spider communities in Eucalyptus plantations in the Northern Negev, Israel

Background/Question/Methods

Plantation forests are an important part of the forest estate in many countries. This applies particularly to Israel where foresters planted almost 100,000 ha of former open land with often non-native tree species. Eucalyptus camaldulensis is one of the most common and oldest tree species used as forest stands and groves. Due to the different ages of the plantations, animal assemblages may vary strongly between planted forest patches, whereas older patches may serve as source habitats for adjacent younger forests. Spiders are amongst the most abundant predacious arthropods in these arid and semi-arid environments. The conducted study aimed to examine changes in spider diversity depending on local and adjacent habitat ages.  Thereby, we hypothesized that spider diversity and abundance increases with 1. the age of the plantation 2. the age of the adjacent forest patch due to immigration 3. the mean age and amount of forest in the surrounding landscape. To investigate these hypotheses, we performed a GIS-based pre-selection of study sites that kept study site age and age of forest patches in the surrounding landscape as independent as possible. The selected sites varied in age from 13 to 49 years and adjacent patches from 17 to 60 years.

Results/Conclusions

Spider assemblages showed strong responses to the age of local habitats as well as to the age of habitats surrounding the focal plantations. Thereby, spiders varied in strength of their reaction according to their habitat specialization. Spider species with woody habitat preferences showed strong reactions to habitat age, whereas generalist or open land spiders showed minor or no reaction to habitat age. Astonishingly, local age and age of adjacent woody habitats showed equally strong effects on spider communities. The results of this study show, that not only connectivity and size of habitat patches are important factors for studies on a landscape scale, but also the age of habitat patches should be considered. The results of this study can be widely implemented in forest management schemes and conservational decisions.