AOBPreview originally published online on September 30, 2005
Annals of Botany 2005 96(7):1215-1223; doi:10.1093/aob/mci271
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The Relative Importance of Pre- and Post-germination Determinants for Recruitment of an Annual Plant Community on Moving Sandy Land
1 Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, 260 Donggang West Road, Lanzhou 730000, China and 2 NSW Department of Primary Industries, Wagga Wagga Agricultural Institute PMB, Wagga Wagga, NSW 2650, Australia
* For correspondence. E-mail lfengrui{at}vip.163.com
Received: 24 June 2005 Returned for revision: 18 July 2005 Accepted: 8 August 2005 Published electronically: 30 September 2005
• Background and Aims The relative importance of pre- and post-germination determinants for recruitment of natural plant communities is rarely explored. An annual plant community on moving sandy land was chosen for a case study. Answers to the following questions were sought: (a) Does recruitment of new individuals within the community of annual plants differ in time and space? (b) Is there spatial concordance between seed deposition, seedling emergence, survival and recruitment? (c) What are the direct and indirect effects of pre- and post-germination determinants on plant recruitment.
• Methods An integrative approach combining investigation of natural recruitment processes with regression, correlation and path analyses was adopted. Data on seed deposition and seedling recruitment were collected by monitoring the number of seeds deposited in the top 5 cm of the soil and the numbers of seedlings emerged and recruited from all annual plants at sites to a range of distances from the existing shrub Artemisia halodendron (Asteraceae) in eight compass directions for two consecutive growing seasons.
• Key Results Community-level recruitment was strongly affected by inter-annual rainfall variation and was highly site- and density-dependent. Low recruitment rate in this system was due to low emergence rate and low post-emergence survival rate. Of the pre- and post-germination determinants studied, it was the number of seedlings which emerged and the post-emergence survival rate that had the greatest direct effects on recruitment, with a combination of both variables explaining the majority of the variance (97 %) in recruitment.
• Conclusions This study suggests that post-germination determinants (emergence and survival) rather than pre-germination determinants (seed deposition) substantially determined the final pattern of recruitment. Although the density of seeds deposited did not have a significant direct effect on recruitment, it contributed to observed variation in recruitment indirectly through density-dependent emergence of seedlings.
Key words: Annual plants, community level, Horqin Sandy Land, path analysis, recruitment dynamics, recruitment success, spatial variation, seed deposition, seedling emergence, seedling survival