Vegetation density

Miller, M. W. 1999. Relative effects of plumage coloration and vegetation density on nest success. Condor 101 255-261. 

Figure 1. The May 1971 Vegetation Density Map of the 169 sections (each 122 m x 122 m) that constituted the 2.5 km area that received more than 69,300 kg 2,4-D and 2,4,5-T between June 1964 and December 1969, Test Area C-52A, Eglln AFB, Florida.

Webster and Shaw (1996) showed the importance of vegetative density on effectiveness of the filter strip. In the first years of strip establishment, total herbicide losses from no-till doublecrop soybeans were similar with and without filter strips, while metolachlor and metribuzin losses were reduced as much as 90% with the more established, denser filter strips in the third year. Both fresh and thatch switchgrass residue in vegetative filter strips can intercept and sorb herbicides (Mersie et al., 2006). 

Figure 8. Average air temperature profiles in a 27 m Douglas fir forest. Shaded area represents vertical vegetation density.

Indirect effects.—Indirect effects are those that do not require a direct interaction between the herbicide and an organism. As an example, herbicides, because they directly influence plant cover, result in modification of animal habitat (food, cover, microclimate) which, in turn, influences carrying capacity for specific wildlife species. As a result of the interrelations within food chains, direct effects on relatively minor species can be transferred indirectly to organisms at higher trophic levels. Other examples of indirect effects are those that result from the alteration of vegetation density and species composition. For instance, severe and prolonged... 

Leistra M, Zweers AJ, Warinton JS, Crum SJH, Hand LH, Beltman WHJ, Maund SJ. 2003. Fate of the insecticide lambda-cyhalothrin in ditch enclosures differing in vegetation density. Pest Manag Sci 60 75-84. 

Reflectance peak sensitive to leaf area, vegetation density, biomass Species identification and assessment of vegetation vigour... 

Poggi, D., Porporato, A., Ridolfi, L., Albertson, J., and Katul, G. (2004) The effect of vegetation density on canopy sub-layer turbulence, Boundary-Layer Meteor 111, 565-587. 

Infrared sensor Looks for differences in surface radiation caused by objects or disturbances in the soil. Affected by ambient temperatures, high levels of soli moisture, and vegetation density. Only effective against UXO at or near the surface and against UXO that has not been in the ground too long. 

The content of the organic compounds is lowest in the relatively clean aquatic system because the pollution extent is insignificant, as well as the vegetation density. 

The bed roughness boundary layer thickness is subjected to the characteristics of vegetation and dimensional analysis propose the relation between OJh and XDh. By considering 0 may decrease with the vegetation density and tends to the flow depth with sufficiently disperse density, the following relation is proposed as a favorable formula to estimate the bed roughness boundary layer thickness (see Fig. 3). 

Loose and hydraulically applied mulch Lowest cost well accepted high installation rate moderate sediment yield moderate vegetative density Very temporary (less than a few weeks/months) no concentrated flows dusty requires anchoring (crimping, tackifier) may require noxious weed certification... 

Fiber roving systems Low to moderate cost high subgrade conformance very low sediment yield very good vegetative density Temporary (1—2 years) low to moderate flows only special equipment required... 

Open-weave mesh Low to moderate cost moderate sediment yields moderate vegetative density moderate moisture absorption Temporary (1—2 years) low flows only not complete ground cover moderate moisture absorption... 

Other hard armor systems Long-term (indefinite) moderate to very high flows low to moderate waves low to moderate sediment yields range of fill materials durable and low maintenance High to very high costs no to delayed vegetation estabhshment no to low vegetation density may prevent infiltrahon special deploymenl/equipment requirements... 

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