Nurse effect in the clonal establishment of Sedum oxypetalum in disturbed environments

Background/Question/Methods

This study evaluates the production of shoots, leaves, adventitious roots and the establishment of ramets of Sedum oxypetalum (Crasulaceae) under the canopy of Buddleia cordata and Opuntia spp as potential nurse plants. It also assesses the effects of the season and orientation in which they were placed. 

The study was conducted in the lava fields of the Ecological Park of Mexico City (PECM for its Spanish abbreviation), in the South of Mexico City. Sedum oxypetalum cuttings were placed in two seasons of 2011, January and June. They were laid horizontally in three disturbed areas. We identified 30 individuals from Buddleia cordata and 30 from Opuntia spp as nurse plants. Under its canopy 3 branches were placed at each cardinal point. Furthermore, 30 control cuttings were placed in total. Structure production and establishment were monitored monthly. The data analysis was performed using  StatSoft, v.8. We applied multivariate generalized linear models to assess the effect of independent variables on the dependent variables. Post-hoc Tukey tests were performed to identify factors that had significant effect on the response variables.

Results/Conclusions

The MANOVA conducted with data from January to October 2011 showed that the planting season (p = 0.00000) and the protector plant (p =0.0078) had significant effects on all response variables.  The one-way ANOVA showed that time is significant for all variables except for  establishment (p = 0.32). The presence of the protective plant was crucial for the production of shoots (p = 0.001), leaves (p= 0.003) and roots (p = 0.022). The protective plant species and orientation had a significant effect only on the number of leaves that the branches presented (p= 0.03).

Settlement was more stable in stakes placed in January, even when June stakes have higher values ​​for the other variables. External cuttings (controls) showed little or no production of the study variables (shoots, leaves, roots and establishment).

For restoration purposes through clonal reintroduction of cuttings from Sedum oxypetalum in the Middle Ajusco of Mexico City, we conclude that the best strategy is to place the stakes in January, facing West, and with Opuntia spp as a protective plant.