CARBON FLOW IN THE RHIZOSPHERE OF PONDEROSA PINE-SEEDLINGS

被引:78
作者
NORTON, JM
SMITH, JL
FIRESTONE, MK
机构
[1] Department of Soil Science, University of California, Berkeley
基金
美国国家科学基金会;
关键词
D O I
10.1016/0038-0717(90)90177-2
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
The flow of photosynthetically-fixed carbon was followed in microcosms containing ponderosa pine seedlings using a 14CO2 pulse labeling technique. Plant and soil samples were harvested at the end of labeling and after a 1 week chase period to examine the movement of 14C from different root types into adjacent soil. The total and specific activity (SA) of C was determined in above-ground and below-ground plant fractions and in soil 0-2 mm. 2-5 mm and > 5 mm from coarse, fine or young roots. The SA of mycorrhizal tips and hyphal strands was also assessed. Microbial biomass C and 14C content was determined by the chloroform fumigation incubation technique in the non-rhizosphere soil. The highest SA in the plant was found in the young root tip region demonstrating that this was a strong sink for recent photosynthate. The fine roots with their associated short laterals and mycorrhizae contained > 25% of the 14C recovered in all plant fractions. The highest SA in the soil was found within 2 mm of the young root surface. Fine roots had the highest rate of C loss to the soil per unit C assimilated in the root segment. The large differences in C flow to the rhizosphere from roots of different morphology demonstrates the importance of differentiating root types in studies of C flux. The important role of mycorrhizal hyphae in redistribution of recently-fixed C in soil was illustrated by their high SA and the large percentage ( > 30%) of 14C recovered in non-rhizosphcre soil. The SA of the microbial biomass C in the non-rhizosphere soil decreased by over 50% during 1 week indicating a rapid turnover rate in this active fraction. The loss of recently-fixed C from pine roots by rhizodeposition and hyphal transport was an important energy source for the soil microbial community even in soil not directly adjacent to the root surface. © 1990.
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收藏
页码:449 / 455
页数:7
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