Shrubland

One consequence of the shift from grassland to shrubland is the potential for significant increases in volatile hydrocarbons added to the atmosphere. The leaves of creosotebush, Larrea tridentata, yielded 0.1 to 0.2 percent of a complex mixture of volatile compounds. That mixture contains several hundred compounds of which 100 accounted for more than 90% of the total volatiles (23). The volatiles that were identified included four monoterpene hydrocarbons, four oxygenated monoterpenes, six sesquiterpene hydrocarbons, eight aromatics like benzyl acetate and ethyl benzoate, plus... 

There are no data on the flux rates of leaf volatiles into the atmosphere. In the L. tridentata shrublands of North America and in areas in Australia where unpalatable, woody shrubs have replaced grasses, the presence of volatile hydrocarbons in the air is detectable by the human nose. The distinct odors of these hydrocarbons is especially noticeable after a rain. It has been suggested that these compounds may undergo atmospheric reactions that produce ozone and other oxidizing substances (8). However, there are no data on these atmospheric reactions. 

Sardans J, Penuelas J, Estiarte M (2008) Warming and drought change trace element bioaccumulation patterns in a Mediterranean shrubland. Chemosphere 70 874—885... 

Temperature Mediterranean shrubland, Spain, +1°C over 6 years... 

Experimental Forest in New Hampshire, USA, removal of snow cover to promote soil freezing Water Mediterranean shrubland, Spain, 20.6% decrease in... 

Figure 15 Alternating paleoenvironments of desert CAM shrublands and C3 grasslands represented by a sequence of Quaternary paleosols (0-100 ka) in the Palouse loess near Kahlotus, Washington, USA showing (left to right), field section with thermoluminescence dates and paleosol identification (Moll, is Mollisol, Arid, is Aridisol), paleosol position and development (represented by black boxes), paleosol calcareousness (scale based on acid reaction), Munsell hue (measured dry in field), sand-silt-clay proportion, of pedogenic carbonate, of opal phytoliths, abundance of earthworm pellets, and abundance of cicada burrows (source Retallack, 2001c).

Grover, H. D. and Musick, H. B. (1990). Shrubland encroachment in southern New Mexico, USA an analysis of desertification processes in the American southwest. Clinuitic Cluinge 17, 305-330. 

Holmes, P. M. and Cowling, R. M. (1997). The effects of invasion by Acacia saligna on the guild structure and regeneration capabilities of South African fynbos shrublands. /. Appl. Ecol. 34, 317-332. 

O Connor, T. G. and Roux, P. W. (1995). Vegetation changes (1949-71) in a semi-arid, grassy dwarf shrubland in the Karoo, South Africa influence of rainftill variability and grazing by sheep./. Appl. Ecol. 32, 612-626. 

Yorks, T. P., West, N. E., and Capels, K. M. (1992). Vegetation differences in desert shrublands of western Utah s Pine Valley between 1933 and 1989. J. Range Manage. 45,569-578. 

Armstrong, R.D. and Helyar, K.R. (1993) Utilization of labelled mineral and organic phosphorus sources by grasses common to semi-arid mulga shrublands. Australian Journal of Soil Research 31, 2 71-283. 

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