刈割对滇西北退化高寒草甸植物化学计量特征的影响

Effects of mowing on plant stoichiometry in a degraded alpine meadow in Northwest Yunnan

关键词:  高寒草甸, 植物群落, 退化程度, 刈割年限, C:N:P, N-P幂函数关系

Key words:  alpine meadow, plant community, degradation level, mowing duration, C:N:P, N-P power function relationship

摘要:

为探究环境干扰对退化高寒草甸植物化学计量特征的影响,该研究于2018—2020年对香格里拉市3个退化程度[轻度退化(LD)、中度退化(MD)、重度退化(SD)]的高寒草甸开展刈割试验,进而分析退化高寒草甸植物C、N、P含量、C:N:P和 N-P幂函数关系在不同刈割年限(0、1、2 a)之间的差异。结果表明:(1)除莎草科P含量外,草甸植物群落、禾本科和杂类草的C、N、P含量在退化程度间无显著差异(P>0.05)。随着刈割年限的增加,退化草甸植物C、N、P含量呈先增后降的趋势(P<0.05)。(2)草甸植物C:N和C:P在退化程度间无差异(P>0.05)。从LD到SD,植物群落、莎草科和杂类草的N:P比先小幅下降再显著上升(P<0.05),禾本科的N:P未发生显著变化(P>0.05)。(3)随刈割年限增加,草甸植物的C:N和C:P呈先降后增、N:P呈先增后降的趋势。刈割0 a时,莎草科的C:P和N:P显著高于杂类草(P<0.05),与植物群落和禾本科无差异(P>0.05); 刈割1 a和2 a时,莎草科的C:P和N:P高于植物群落和其他功能群(P<0.05); 在各刈割年限,植物群落和各功能群植物间的C:N无差异(P>0.05)。(4)随刈割年限增加,退化草甸植物的N-P幂函数关系由弱变强、幂指数趋于稳定。莎草科的N-P幂指数(小于0.1)与植物群落、禾本科和杂类草的幂指数(稳定在0.19～0.22之间)明显不同。该研究发现,刈割干扰下退化高寒草甸植物生态化学计量特征在退化程度间差异不大,但其随刈割年限增加发生显著变化,这说明滇西北不同退化程度高寒草甸对刈割干扰可能具有相似的响应过程。

Abstract:

This study aimed to investigate the effects of environmental disturbances on the stoichiometry characteristics of plants in degraded alpine meadows. To achieve this, a mowing experiment was conducted on an alpine meadow with three degradation levels [light degradation(LD), moderate degradation(MD), and severe degradation(SD)] in Shangri-La from 2018 to 2020. Subsequently, differences in plant carbon(C)content, nitrogen(N)content, phosphorous(P)content, C:N:P ratio, and N-P power function relationship among different mowing durations(0, 1, 2 a, respectively)were analysed. The results were as follows:(1)Except for the P content of Cyperaceae, plant C, N and P contents of the entire plant community, Gramineae and forbs did not vary among degradation levels(P > 0.05)during the mowing experiment. Plant C, N and P contents tended increase and then decrease with increasing mowing years, i.e., these indices were the highest after 1 a of mowing(P < 0.05).(2)At the plant community and functional group levels, there was no significant difference in plant C:N ratio and C:P ratio among degradation levels(P>0.05). From LD to SD, the N:P ratio of the plant community, Cyperaceae and forbs tended to decrease slightly first and then increased(P < 0.05), while the N:P ratio of Gramineae did not change significantly(P > 0.05).(3)The N:P ratio and C:P ratio showed a parabolic trend, while the C:N ratio showed an inverse trend with the increasing of mowing duration. Before mowing(i.e., mowing 0 a), the C:P ratio and N:P ratio of Cyperaceae were higher than those of forbs(P<0.05)but did not vary from those of the plant community and Gramineae(P > 0.05). After mowing(i.e., mowing 1 a or 2 a), the C:P ratio and N:P ratio of Cyperaceae were higher than those of the whole plant community, Gramineae, and forbs(P < 0.05). At each mowing duration, the C:N ratio of plants did not vary among plant communities and functional groups(P > 0.05).(4)Mowing caused a stronger N-P power function relationship and a stable power exponent both at the plant community and functional group levels. And the N-P power exponent of Cyperaceae was less than 0.1, while those of the plant community, Gramineae and forbs remained stable at 0.19-0.22. In conclusion, this study found that plant stoichiometry remained stable across degradation levels but changed significantly with the prolongation of the mowing duration, which implies that different degraded alpine meadows in Northwest Yunnan may share common response mechanisms to mowing disturbance.