If you could digitize the vineyards and forest edge into ArcGIS, You can use several useful tools to measure the distance between the two features (Spatial analyst, distance to line or distance to point), that following is possible transform in matrices and so analize with some statistical software (R, SPSS, Statistica, ecc).

Anyway, also if you work only with Google earth, I can suggest to measure also minimum distance and maximum distance between the two interested features (vineyards and forest edge) in addition to an average the perpendicular distances between the three or more measured points ...Furthermore, also the edge contour could be important for your study and for the edge effect.

I think it is very important to calculate fractals - or fractal metrics of land use for this kind of study. The shape, and fragments of different types of land use in the landscape are also very important. See attached article.

I suggest you don’t get too hung up over the ‘right’ way to measure proximity to a forest as a simple distance. I think you need to take several parameters into account that will better reflect the probability of successful movement. The distance we measure (metres to kilometres) doesn’t necessarily reflect the effort required for a moth to migrate, the triggers for migration or the likelihood of the species being present in the woodland. The effort required should include the terrain, local climate (strength and direction of prevailing wind for instance), the habitat matrix that separates the vineyard from the forest and relative location (e.g. above or below). The triggers should include factors such as visibility (visual and through smell), absolute location (such as direction, in case the sun or magnetic north are involved in movement) and landmarks. The matrix would include possible transient refuges and distance/time spent crossing different habitats each with their challenges and risks (including predators). Finally, the presence of the species in the forest will be determined at least in part by the physical and ecological characteristics of the woodland (species of tree, age, management, spacing, etc. for ecology and size, shape spatial complexity for physical character).

How many vineyards are in your study? You could collect a suite of simple measures (e.g. shortest distance, compass direction, woodland forest size, habitat types/complexity in matrix, woodland type, etc.). Where you feel it would be time consuming to collect measures (e.g. woodland patch size) you could use a classification system (e.g. a few trees, copse, woodlot, small woodland, medium size woodland, large forest, etc.) using categories you clearly and explicitly define. As your analysis progresses you can be selective of the variables and improve the precision with which you collect them, but always try and relate the measures back to the organisms involved.

Thank you very much David! Your opinion is certainly very helpful. I still have a plan to survey the presence of wild grapes in nearby wooded areas. Also, I can categorize the habitat based on the categories that you mentioned. I have 50 different vineyard blocks (i.e. different varieties, rootstocks etc.) of 20 vineyards. Do you have literature that actually defined habitat categories ie. woodlot, copse, small woodland etc. Also, I am looking for standard procedure to find out whether wild grape species occurs on the target area or not? If you have any references, that would be appreciated. Other factors that I am considering are: soil related factors (since the insect that I am targeting is root borer), horticultural and management related factors.

Dear Jhalendra,

Here are some articles of relevance. The methods used to quantify the woody vegetation in the surrounding landscape may be more complicated than you are planning however they are still worth a read. They focus on predators and parasitoids not leps, but some of the issues around movement will be similar. I would also check if there are any alternate host plants that your moth can use that may be present in the adjacent woodland area or the margins of the vineyard (besides the wild grapes).

cheers,

Sarina

Thomson, L.J. & Hoffmann, A.A. (2013) Spatial scale of benefits from adjacent woody vegetation on natural enemies within vineyards. Biological Control, 64, 57-65.

Thomson, L.J. & Hoffmann, A.A. (2009) Vegetation increases the abundance of natural enemies in vineyards. Biological Control, 49, 259-269.

Thomson, L.J. & Hoffmann, A.A. (2010) Natural enemy response and pest control:importance of local vegetation. Biological Control, 52, 160-166.

Thomson, L.J., McKenzie, J., Sharley, D.J., Nash, M.A., Tsitsilas, A. & Hoffmann, A.A. (2010) Effect of woody vegetation at the landscape scale on the abundance of natural enemies in Australian vineyards. Biological Control, 54, 248-254.

Hi Jhalendra, for habitat categories I think you need to be pragmatic and operate within the constraints of the data available to you and your sample size; you want to have categories you are confident you can distinguish, that are generally well represented within your data – you don’t want more categories than observations! As examples of forest/woodland size categories, in bird studies (in Britain) Shelley Hinsley, when studying great tits, used two categories (large and small, splitting at 1.1 ha) while in a study of fragmentation used three categories (5 ha). Pete Robertson, looking at game birds collected a variety of parameters that he then analysed using stepwise regression to create a model of pheasant density. I’m not sure any of these studies are suitable as ‘off the shelf’ solutions, but they do give ideas of the types of information you could collect.

Bellamy, P. E., Rothery, P., Hinsley, S. A. & Newton, I. (2000) Variation in the relationship between numbers of breeding pairs and woodland area for passerines in fragmented habitat. Ecography, 23, 130-138.

Hinsley, S. A., Rothery, P., Ferns, P. N., Bellamy, P. E. & Dawson, A. (2003) Wood size and timing of moult in birds: potential consequences for plumage quality and bird survival. Ibis, 145, 337-340.

Robertson, P. A., Woodburn, M. I. A. & Hill, D. A. (1993) Factors affecting winter pheasant density in British woodlands. Journal of Applied Ecology, 30, 459-464.

Thank you all specially David and Sarina for your excellent thoughts and providing relevant literature.