This study was designed to quantify the degree of herbivore damage on saplings of different tree and shrub species in the 27 Comparative Study Plots. In June/July 2008, we selected 1,818 saplings (20-100 cm height) of 23 species and visually assessed herbivore damage using a percentage class system. We intend to relate leaf consumption to tree diversity and the density of conspecifics in the tree layer of the CSPs. Both have often been suggested to influence herbivory. Especially data on the relationship between herbivory and plant diversity in highly diverse forest systems is scarce and the CSPs in the Gutianshan National Nature Reserve offer an excellent opportunity to tackle this issue. In cooperation with other subprojects, differences in succeptibility to herbivory between species can be studied using data on leaf chemistry and range sizes of the species.

Twenty-three evergreen tree and shrub species were selected to study folivory on saplings in the 27 CSPs: Ardisia crenata, Camellia fraterna, Castanopsis carlesii, Castanopsis eyrei, Castanopsis fargesii, Castanopsis tibetana, Cinnamomum subavenium, Cyclobalanopsis glauca, Cyclobalanopsis myrsinaefolia, Daphniphyllum oldhamii, Eurya muricata, Eurya rubiginosa, Itea chinensis, Lespedeza formosa, Lithocarpus glaber, Loropetalum chinense, Machilus thunbergii, Meliosma oldhamii, Myrica rubra, Neolitsea aurata, Quercus serrata, Schima superba and Symplocos stellaris. In each plot, a maximum of ten saplings of each species (with a height between 20 and 100 cm) was randomly sampled by crossing the whole plot along parallel transects from one side to the opposite side. The degree of foliar damage, defined as the removal of photosynthetic tissue due to leaf-chewing, mining and galling (and, if visible, sucking) insects, was assessed for all leaves of the saplings. To account for age specific differences in leaf herbivory, we differentiated between young (expanded in the current growing season) and old leaves (expanded in previous growing seasons). Senescent or fungally heavily damaged leaves were excluded. Sampling was conducted once on each plot at the end of the rainy season in June/July 2008. Thus, we recorded standing levels of herbivory instead of consumption rates over a specified period of time. Herbivore damage was visually estimated using percentage classes of leaf tissue removal (0%; <1%; 1-5%; >5-15%; >15-35%; >35%). These classes were defined beforehand by analyzing random collections of leaves. The leaves were digitally scanned and the degree of herbivory was determined using pixel ratios of the removed and the estimated total leaf tissue of each leaf, extracted with the histogram function in Adobe Photoshop CS3. Herbivore damage in the field was assessed by only one person (A.S.) to prevent variability in estimation accuracy. Mean percentage of herbivory from the sampled leaves (0%; 0.5%; 3%; 9%; 23%; 55%) for each percentage class was calculated for further analyses.

Gutianshan National Nature Reserve: Assessment of leaf herbivory on 1,818 saplings of 23 tree and shrub species in the 27 CSPs (June/July 2008)

June July 2008

Ardisia crenata, Camellia fraterna, Castanopsis carlesii, Castanopsis eyrei, Castanopsis fargesii, Castanopsis tibetana, Cinnamomum subavenium, Cyclobalanopsis glauca, Cyclobalanopsis myrsinaefolia, Daphniphyllum oldhamii, Eurya muricata, Eurya rubiginosa, Itea chinensis, Lespedeza formosa, Lithocarpus glaber, Loropetalum chinense, Machilus thunbergii, Meliosma oldhamii, Myrica rubra, Neolitsea aurata, Quercus serrata, Schima superba and Symplocos stellaris

Used to calculate herbivory pressure on tree saplings in the CSPs