whether desert or forest, such terms as biomass accumulation and standing crop ought to 

 be defined as including all matter not fragmented beyond recognition; i.e., everything 

 short of humus. It seems that there is no more distinct point in the turnover process 

 at which to place the boundary. 



No value of aboveground productivity reported for North America is near our low 

 value of 28 g./m.2. In Chew and Chew's (1965) warm desert, the aboveground productivity 

 value was 131 g./m.^; on Pearson's (1965) steppe, it was 123 g./m.^. In a community 

 similar to Pearson's, Blaisdell (1958) determined average aboveground productivity 

 over a 13-year period to be 92 g./m.^. Ovington and others (1963) reported a net 

 productivity of 93 g./m.^ for the aerial part of a ^1innesota prairie. Rodin and 

 Basilevich (1967) list six Asian desert communities where annual turnover of aerial 

 parts ranges from 15 to 44 g./m.^. 



Our value of about 260 g./m.^ for total annual productivity above and below the 

 ground is in the same order of magnitude as Pearson's 240 g./m.^, and the Eurasian 

 values, which were 122 for a dwarf semishrub desert, 250 for a subtropical desert, and 

 420 for dry steppes (Rodin and Basilevich 1968). 



The minimum for total organic matter accumulation in the herbaceous prairie of 

 Ovington and others (1963) occurred in early May, and was 616 g./m.^; 211 g. of it, 

 nearly all dead material, was aboveground. This figure is much lower than our minimum 

 for the woody desert. Our estimate was 1,770 g./m.^, of which 205 g. was dead and 35 g. 

 alive aboveground, and a total of 1,530 g. dead and alive below the ground. Other 

 studies either fail to include dead material in biomass values, or report only an 

 annual value for litter fall. 



The following features of organic niatter occurrence and disposition on this desert 

 of woody perennial plant cover are significant: (1) The low productivity of aboveground 

 biomass; (2) the high proportion of aboveground dead matter, a result of slow litter 

 breakdown; (3) low ratios for both productivity and matter accumulation of aerial to 

 subterranean portions of the respective totals; (4) the movement of top-derived litter 

 into the soil before it loses its identity; and (5) the uneven horizontal distribution 

 of underground organic matter in the upper layers of the rhizosphere. 



14 



