Spatial Heterogeneity, Not Visitation Bias, Dominates Variation in Herbivory: Comment
نویسنده
چکیده
Making scientific measurements can alter the subject of the measurement (Heisenberg 1927), limiting one’s ability to understand how systems operate when they are not being studied. The idea that such effects occur during ecological research is not new (e.g., Singer and Wedlake 1981, Major 1990, Duncan et al. 2002), but our recent studies have renewed awareness (Cahill et al. 2001, 2002, Hik et al. 2003). Visitation by researchers to focal plants can alter herbivory and plant growth (Cahill et al. 2001, 2002) due to both effects of handling focal plants and trampling neighbors (Cahill et al. 2002). ‘‘Visitation effects’’ occur in a variety of communities, appear widespread among species, and are generally of low intensity (Hik et al. 2003). Presumably because these prior results have such important implications for the interpretation of ecological studies, other groups have tested the generality of our findings by replicating aspects of our initial experiment (Cahill et al. 2001) in other systems. In Cedar Creek, Minnesota, USA, Schnitzer et al. (2002) found that weekly visitation increased pathogen damage on some plants but had no effect on herbivory. Bradley et al. (2003) similarly conclude there is little evidence that weekly visitation alters herbivory or plant growth in three U.S. locations (Cedar Creek, Savannah River [South Carolina], and Reller Ranch/Madigan Prairie [Nebraska]). Here we show that the experimental design and statistical analysis used by Bradley et al. (2003) do not adequately control for Type II experimental error (ac-
منابع مشابه
Spatial Heterogeneity, Not Visitation Bias, Dominates Variation in Herbivory: Comment & Reply
متن کامل
New method for estimation of the scale of fluctuation of geotechnical properties in natural deposits
One of the main distinctions between geomaterials and other engineering materials is the spatial variation of their properties in different directions. This characteristic of geomaterials -so called heterogeneity- is studied herewith. Several spatial distributions are introduced to describe probabilistic variation of geotechnical properties of soils. Among all, the absolute normal distribution ...
متن کاملLeaf herbivory imposes fitness costs mediated by hummingbird and insect pollinators
Plant responses induced by herbivore damage can provide fitness benefits, but can also have important costs due to altered interactions with mutualist pollinators. We examined the effects of plant responses to herbivory in a hummingbird-pollinated distylous shrub, Palicourea angustifolia. Through a series of field experiments we investigated whether damage from foliar herbivores leads to a redu...
متن کاملElevational and seasonal variation in the foliar quality and arthropod community of Acer pensylvanicum.
Elevational gradients provide natural experiments for examining how variation in abiotic forces such as nutrient mineralization rates, risk of photodamge, temperature, and precipitation influence plant-insect interactions. At the Coweeta LTER site in the Southern Appalachian Mountains, we examined spatial and temporal variation in striped maple, Acer pensylvanicum, foliar quality and associated...
متن کاملSpatial heterogeneity across five rangelands managed with pyric-herbivory
article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. 2 24 Summary 25 1. Many rangelands evolved under an interactive disturbance regime in which grazers 26 respond to the spatial pattern of fire and create a patchy, heterogeneous landscape. 27 Spatially heterogeneous fire and grazing create heterogeneity in vegetation structure at 28 ...
متن کامل