Wednesday, January 7, 2009

Mini-proposal for master's thesis

Over the past decade, increases in industrial agriculture have caused rapid declines in insect biodiversity because of the simplification of the landscape through the enlargement of crop field sizes and reduction of non-crop habitat (Bianchi et al. 2006). Non-crop habitat is necessary for a wide diversity of insects, especially for pollinators and natural predators for crop pests (e.g., Kremen et al. 2002, Tscharntke et al. 2007, Ricketts et al 2008). Natural habitat is beneficial for pollinators by supplying a diversity of nectar sources and nesting habitat (Kremen et al. 2004, Winfree et al. 2008) and is also beneficial for natural predators by supplying alternative hosts and overwintering sites (Bianchi et al. 2006, Vollhardt et al. 2008). Landscape management in an agroecosystem is needed to keep insect biodiversity in these natural habitats.

Connectivity between natural habitat in a landscape (i.e., an agroecosystem) enhances both diversity of natural predators and pollinators because high proportions of non-crop habitats have a greater diversity of natural predators and pollinators (Bianchi et al. 2006, Holzscheh et al. 2007). The economic value of these natural habitats to crop production is poorly understood. Theorectically, if land management practices are influenced by positive feedback through market forces then agroecosystems will become presumably more heterogeneous (Kremen et al. 2007).

Agricultural practices that increase insect biodiversity through increasing landscape complexity (Vollhardt et al. 2008, Tscharnke et al. 2007) and reducing or elimating pesticide input, would also increase the numbers of pollinators and natural predators within an argoecosystems (e.g., Holzschuh et al. 2007, Kremen et al. 2007, Winfree et al. 2008). Total diversity (gamma) on the landscape level is the combination of both the diversity within (alpha) and between (beta) habitats or patches (Clough et al 2007, Tscharntke et al. 2007). Tscharntke et al. (2007) hypothesized that as landscapes became more complex (i.e., more heterogeneous), then gamma diversity would increase. Beta diversity contributes significantly to total diversity because high beta diversity carries benefits for biological control through promoting predator-prey or parasite host systems at larger spatial scales. Higher beta diversity allows exploitation of heterogeneous pest populations because different natural enemies species have different microhabitat preferences (Tscharntke et al. 2007).

Conservation of biological control and pollinators is dependant on heterogeneous landscapes because intensely used homogenous landscapes with low species pools is unable to recover after a disturbance. The more complex a landscape becomes the quicker and more likely it will recover (Tschantke et al. 2007). Populations from adjacent habitats provide spatiotemporal complexity that allows for populations of natural enemies and pollinators to build up (Bianchi et al. 2006). This insurance (Yachi and Loreau 1999) buffers against fluctuations in ecosystem functioning by supporting higher species richness in a landscape.

To provide for a diversity of pollinators, nesting materials and nectar sources are needed. Determining how pollinators’ foraging range is affected by limited resources in nesting sites and/or floral resources are important area to look at. Changes in landscape alter the searching behavior of pollinators and their natural enemies. Top-down vs. bottom-up forces on pollinator’s relative abundance is another important area that needs to be identified (Kremen et al. 2007).

It is important to look at conservation biology in the agroecosystem on the landscape level because most arthropods are affected by spatial scales larger than their plot level. In the surrounding landscape, the species pools are important for the conservation of natural enemies and pollinators during the recovery period of species after a disturbance, especially for poorly-dispersing insects and specialized enemies (e.g., Kremen et al. 2002, Bianchi et al. 2006, Tscharntke et al. 2007, Ricketts et al 2008). I will test two hypotheses in my thesis. The first is, as complexity of landscape increases, the total diversity (gamma) increases is affected by beta (between) habitat or patch diversity than alpha (within) habitat or patch diversity, leading to higher pest control and pollinator relative abundances. Second I will to test the hypothesis that because of the loss of non-crop habitat, bottom-up forces have a greater effect to the biodiversity of natural enemies and relative abundances of pollinators as natural habitat decreases. I predict that as the landscape becomes more homogenous, the diversity of natural enemies and relative abundances of pollinators decline because of shrinking of the natural habitat that is required for there survival.

Within Butler and Preble counties in Ohio, I will be doing my study on Conservation Reserve Program (CRP) and Three-Valley Trust lands. CRP lands are part of the Natural Resources Conservation Services (NRCS) branch of the United Stated Department of Agriculture (USDA). The CRP provides assistance to farmers to address soil, water, and other related natural resources on their lands that will provide an environmental benefit to the lands in a cost-effective manner (Kremen et al. 2002). I will use a variety of techniques for collecting data, including a grid of combination pan/flight intercept traps, sweep sampling along transects within the interior and along edges of habitat patches, and patrolling fixed plots in a serpentine manner to estimate populations of butterflies, another common pollinator.

I will be using a number of tools to quantify biodiversity and abundances. Firstly, I will be using Geographical Information Systems (GIS) to explain connectivity and variation in a landscape. I will take waypoints in the field using a Geographic Positioning System (GPS) and used land cover to explain the variation inside a landscape. Secondly, I will also be focusing on specific species of a pollinator, a herbivore and a natural predator and use different matrices to explain alpha-, beta-, and gamma-diversity.

I expect to show that with lesser landscape heterogeneity, that the biodiversity of natural predators and abundances of pollinators will decrease with less natural habitat. I would expect that this is an effect from the bottom up because lack of resources required for these species to persist (e.g., Kremen et al. 2002, Tscharntke et al. 2007, Ricketts et al 2008). I also expect to see that as habitat heterogeneity decreases that species turn-over of both natural predators and pollinators to decrease because of the decreasing effect of beta-diversity on the total diversity (Clough et al 2007, Tscharntke et al. 2007).

Bianchi, F. J. J. A, Booij, C. J. H., and Tscharntke, T. 2006. Sustainable pest regulation in agricultural landscapes: a review on landscape composition, biodiversity and natural pest control. Proc. of the R. Soc. 273, 1715-1727

Clough, Y, Holzschuh, A., Gabriel, D., Purtauf, T., Kleijn, D., Kruess, A., Steffan-Dewenter, I., Tscharntke, T. 2007. Alpha and beta diversity of anthropods and plants in organically and conventional managed wheat fields. J. of Appl. Ecol. 44, 804-812

Holzschuh, A., Steffan-Dewenter, I., Kleijn, D., and Tscharntke, T. 2007. Diversity of flower-visiting bees in cereal fields: effects of farming system, landscape composition and regional context. J of Appl. Ecol. 44, 41-49

Kremen, C. Williams, N. M., and Thorp, R. W. 2002. Crop pollination from native bees at risk from agricultural intensification. Proc. Nat. Aced. Sci. USA 99, 16812-16816

Kremen, C., Williams, N. M., Bugg, R. L., Fay, J. P., and Thorp, R. W. 2004. The area requirement of an ecosystem service: crop pollination by native bee communities in California. Ecol. Lett. 7, 1109-1119

Kremen, C., Williams, M.N., Aizen, M.A., Gemmill-Herren, B., LeBuhn, G., Minckley, R., Packer, L., Potts, S.G., Roulston, T., Steffan-Dewenter, I., Vázquez, D. P., Winfree, R., Adams, L., Greenleaf, S. S., Keitt, T. H., Klein, A., Regtz, J., and Ricketts, T. H. 2007. Pollination and other ecosystem services produced by mobile organism: a conceptual framework for the effects of land-use change. Ecol. Lett. 10, 299-314

Ricketts, T. H., Regetz, J., Steffan-Dewenter, I., Cunningham, S. A., Kremen, C., Bogdanski, A., Gennill-Herren, B., Greenfield, S. S., Klien A. M., Mayfield, M. M., Morandin, L. A., Ochieng, A., Viana, B. 2008. Landscape effects on crop pollination services: are these general patterns? Ecol. Lett. 11, 499-515

Tscharntke, T., Bommarco, R., Clough, Y., Crist, T. O., Kleijn, D., Rand, T. a., Tylianakis, J. M., van Nouhuys, S., and Vidal, S. 2007. Conservation biological control and enemy diversity on a landscape scale. Biol. Cont. 43, 294-309

Vollhardt, I. M. G., Tschartke, T., Wäckers, F. L., Bianchi, F. J. J. A., Theis, C. 2008. Diversity of cereal aphid parasitiod in simple and complex landscapes. Agri., Ecos., and Envi. 126, 289-292

Winfree, R., Williams N. M., Gaines, H., Ascher, J. S., and Kremen, C. 2008. Wild bee pollinators provide the majority of crop visitation across land-use gradients in New Jersey and Pennsylvania, USA. J. of Appl. Ecol. 45, 793-802

Yanchi, S. and Loreau M. 1999. Biodiversity an ecosystem productivity on a fluctuating environment: the insurance hypothesis. Proc. Nat. Aced. Sci. USA 96, 1463-1498

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