Leadley P W, Niklaus P A, Stocker R, Körner C
Botanisches Institut der Universität Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland, , , , , , CH.
Oecologia. 1999 Jan;118(1):39-49. doi: 10.1007/s004420050701.
The effects of elevated CO(2) on plant biomass and community structure have been studied for four seasons in a calcareous grassland in northwest Switzerland. This highly diverse, semi-natural plant community is dominated by the perennial grass Bromus erectus and is mown twice a year to maintain species composition. Plots of 1.3 m(2) were exposed to ambient or elevated CO(2) concentrations (n = 8) using a novel CO(2) exposure technique, screen-aided CO(2) control (SACC) starting in March 1994. In the 1st year of treatment, the annual harvested biomass (sum of aboveground biomass from mowings in June and October) was not significantly affected by elevated CO(2). However, biomass increased significantly at elevated CO(2) in the 2nd (+20%, P = 0.05), 3rd (+21%, P = 0.02) and 4th years (+29%, P = 0.02). There were no detectable differences in root biomass in the top 8 cm of soil between CO(2) treatments on eight out of nine sampling dates. There were significant differences in CO(2) responsiveness between functional groups (legumes, non-leguminous forbs, graminoids) in the 2nd (P = 0.07) and 3rd (P < 0.001) years of the study. The order of CO(2) responsiveness among functional groups changed substantially from the 2nd to the 3rd year; for example, non-leguminous forbs had the smallest relative response in the 2nd year and the largest in the 3rd year. By the 3rd year of CO(2) exposure, large species-specific differences in CO(2) response had developed. For five important species or genera the order of responsiveness was Lotus corniculatus (+271%), Carex flacca (+249%), Bromus erectus (+33%), Sanguisorba minor (no significant CO(2) effect), and six Trifolium species (a negative response that was not significant). The positive CO(2) responses in Bromus and Carex were most closely related to increases in tiller number. Species richness was not affected by CO(2) treatment, but species evenness increased under elevated CO(2) (modified Hill ratio; P = 0.03) in June of the 3rd year, resulting in a marginally significant increase in species diversity (Simpson's index; P = 0.09). This and other experiments with calcareous grassland plants show that elevated atmospheric CO(2) concentrations can substantially alter the structure of calcareous grassland communities and may increase plant community biomass.
在瑞士西北部的一个钙质草原，对高浓度二氧化碳对植物生物量和群落结构的影响进行了为期四个季节的研究。这个高度多样化的半自然植物群落以多年生草本植物直立雀麦为主导，并且每年刈割两次以维持物种组成。从1994年3月开始，使用一种新型的二氧化碳暴露技术——筛网辅助二氧化碳控制（SACC），将1.3平方米的样地暴露于环境或高浓度二氧化碳浓度下（n = 8）。在处理的第一年，年收获生物量（6月和10月刈割的地上生物量总和）不受高浓度二氧化碳的显著影响。然而，在第二年（增加20%，P = 0.05）、第三年（增加21%，P = 0.02）和第四年（增加29%，P = 0.02），高浓度二氧化碳下生物量显著增加。在九个采样日期中的八个日期，二氧化碳处理之间土壤表层8厘米内的根系生物量没有可检测到的差异。在研究的第二年（P = 0.07）和第三年（P < 0.001），功能组（豆科植物、非豆科草本植物、禾本科植物）之间的二氧化碳响应存在显著差异。功能组之间的二氧化碳响应顺序从第二年到第三年发生了很大变化；例如，非豆科草本植物在第二年的相对响应最小，在第三年最大。到二氧化碳暴露的第三年，已经出现了很大的物种特异性二氧化碳响应差异。对于五个重要的物种或属，响应顺序为百脉根（增加271%）、灰岩苔草（增加249%）、直立雀麦（增加33%）、小地榆（无显著二氧化碳效应）和六种三叶草属植物（负响应但不显著）。雀麦和苔草的正二氧化碳响应与分蘖数的增加关系最为密切。物种丰富度不受二氧化碳处理的影响，但在第三年6月，高浓度二氧化碳下物种均匀度增加（修正的希尔比率；P = 0.03），导致物种多样性略有显著增加（辛普森指数；P = 0.09）。这项以及其他关于钙质草原植物的实验表明，大气中高浓度二氧化碳可以显著改变钙质草原群落的结构，并可能增加植物群落生物量。
