348 REICHLE, DINGER, EDWARDS, HARRIS, AND SOLLINS 



variation among taxa. Therefore a carbon content of 49.6% was used in all 

 calculations of standing crop of woody carbon and annual accumulation. 



From the data in Table 2, the distribution of carbon in the aboveground 

 portion of the autotroph component as of 1970 is estimated to be 8.32 kg/m . 

 This estimate includes leaf carbon of 186 g/m with the pool of 310 g/m , 

 consisting of standing dead branch and bole material. The fraction of carbon in 

 stump (1.02 kg/m 2 ) includes the central stump and large support roots within a 

 radius of 0.6 m. Weight analysis of stumps suggests a stump-to-bole ratio of 0.20, 

 which was used to estimate the weight of this component. Less than 10% of the 

 total aboveground carbon was incorporated in the understory stratum and only 

 0.17% in the herbaceous (low shrub) stratum. 



Autotroph Belowground Standing Crop 



Underground organic-matter pools and associated physiological processes are 

 the least accurately measured and least understood ecosystem component, but 

 root processes are of at least equal importance to ecosystem function as the 

 process of photosynthesis itself. Our analysis separates underground biomass 

 into two components: stumps (discussed previously) and lateral roots beyond 

 the stump radius. Soil cores and pits were used to estimate lateral-root biomass. 

 Rooting-zone depth does not exceed 60 cm in the Liriodendron forest study 

 area even though depth to bedrock is many meters. Therefore all unit-area 

 root-carbon estimates are based on a depth of 60 cm. 



Figure 1 summarizes the seasonal dynamics of the lateral root component. 

 Averaging across sampling dates yields a mean annual lateral root standing pool 

 of carbon of 650 g/m . Accumulation of carbon begins in the lateral root pool 

 by July and continues into the late summer— early autumn. Considerable root 

 dieback of organic material occurs in the fall— winter period. Explanation of the 

 high value of lateral root organic matter in April 1971 awaits completion of 

 confirmatory measurements in 1972 (Fig. 1). Annual fluctuation in climate of 

 the preceding dormant season could be expected to influence pool size. 



Olson (1968) reported a value (0 to 10 cm) of 890 g/m 2 organic matter 

 (approximately 350 g C/m 2 ) for small and medium-sized roots (less than 10 cm 

 diameter). Our analysis to a depth of 60 cm indicates that 30% of the 

 lateral root organic matter is located in the upper 10 cm of soil. With this 

 assumption, 1.17 kg C/m 2 was estimated from Olson's data for 1962 as a peak 

 (early fall) standing crop of lateral root material, compared to 0.85 kg C/m 2 

 based on 1970 data. 



Standing Crop of Detritus 



Litter standing crop collected monthly at 25 randomly selected plots 

 averaged 557 g/m 2 , with the O, and 2 litter accounting for 271 and 286 g, 

 respectively (Table 3). Carbon content of Oj litter was higher (46.5%) than that 



