Shearer G, Kohl D H, Virginia R A, Bryan B A, Skeeters J L, Nilsen E T, Sharifi M R, Rundel P W
Department of Biology, Washington University, 63130, St. Louis, MO, USA.
Department of Soil and Environmental Sciences, University of California, 92521, Riverside, CA, USA.
Oecologia. 1983 Feb;56(2-3):365-373. doi: 10.1007/BF00379714.
The N abundance of tissues of five Prosopis specimens at our primary study site (a Prosopis woodland at Harper's Well in the Sonoran desert of Southern California) was determined over two growing seasons 1980 and 1981. The N abundance of soil and of tissues of presumed non-N-fixing (control) plants was also measured. Prosopis tissues were significantly lower in N than either soil N or corresponding tissues of presumed non-N-fixing plants which derive their N entirely from soil. Soil N was also significantly higher in N than atmospheric N. We conclude that it is feasible to use variations in the natural abundance of N as an index of N-fixation in this kind of ecosystem, and that N-fixation is of considerable importance to Prosopis growing at this site.We also determined the N abundance of leaf tissue of presumed N-fixing and control plants growing at the same site at six additional sites (five in the Sonoran desert of southern California and one in Baja California, Mexico near the town of Catavina). Four of these additional sites were dominated by Prosopis and two were mixed communities. There were statistically significant differences between the N abundances of the pooled legume population and control plants at all sites, although not every legume specimen exhibited this difference. From N abundance data we estimated the fractional contribution of biologically fixed N to the N economy of desert legumes. We concluded that N-fixation is very important to Prosopis at six of seven sites in the Sonoran Desert. At the site where Prosopis did not appear to be fixing N, N-fixation was important only for legumes of the sub-family Papilionoideae, Lupinus, Dalea, Astragalus and Lotus.
在我们的主要研究地点（南加州索诺兰沙漠哈珀斯韦尔的一个牧豆树林地），于1980年和1981年两个生长季节测定了5个牧豆树样本组织中的氮含量。还测量了土壤以及假定不固氮（对照）植物组织中的氮含量。牧豆树组织中的氮含量显著低于土壤氮或假定完全从土壤中获取氮的不固氮植物的相应组织。土壤氮含量也显著高于大气氮。我们得出结论，在这种生态系统中，利用氮的自然丰度变化作为固氮指标是可行的，并且固氮对该地点生长的牧豆树具有相当重要的意义。我们还测定了在另外六个地点（南加州索诺兰沙漠的五个地点和墨西哥下加利福尼亚州卡塔维纳镇附近的一个地点）同一地点生长的假定固氮植物和对照植物叶片组织中的氮含量。这些额外地点中有四个以牧豆树为主，两个是混合群落。在所有地点，合并的豆科植物种群和对照植物的氮含量之间存在统计学上的显著差异，尽管并非每个豆科植物样本都表现出这种差异。根据氮含量数据，我们估计了生物固氮对沙漠豆科植物氮素经济的贡献率。我们得出结论，在索诺兰沙漠七个地点中的六个地点，固氮对牧豆树非常重要。在牧豆树似乎不固氮的地点，固氮仅对蝶形花亚科的豆科植物、羽扇豆属、代尔亚属、黄芪属和百脉根属植物很重要。
