The conservation of native fagaceae using mycorrhizal techniques

Abstract

Fagaceae (oaks) is one of the most important plant families in the temperate and subtropical regions. It was widespread in the original forests in Hong Kong and the South China. Owing to the long history of deforestation, problems on seed dispersal and predation, only small and fragmentary colonies of Fagaceae left nowadays. The establishment of conservation programmes for this threatened plant family is an essence for biodiversity conservation. As suggested by the World Conservation Union, the conservation strategy of Fagaceae should be focused on the increment of its population size. Ex situ conservation, including the propagation and planting of the seedlings to the wild is recommended to prevent the Fagaceae becoming extinct with the further habitat loss. The propagation of Fagaceae seedlings thus became an important subject for study. Plenty of evidence showed that the ectomycorrhiza (EM) can improve the growth and survival of Fagaceae seedlings. However, there is a lack of study on the application of EM on the Fagaceae seeding production in Hong Kong. The aim of this study is to address this gap and to investigate the effects of using mycorrhizal techniques on the propagation and conservation of native Fagaceae species in Hong Kong. This study was carried out with experiments: 1. to study the effects of Field Soil Inoculum (FSI) on the growth of Cyclobalanopsis edithiae seedlings under controlled environmental conditions; 2. to study the effects of three different EM inoculums on the growth of C. edithiae and Castanopsis fabri seedlings under nursery conditions; 3. to study the effects of EM inoculation on the growth of a regionally rare Fagaceae species, Castanopsis concinna and the effects of 3 common nursery treatments (the application of chemical fertilizer, fungicide and pesticide) on the EM formation. The results showed that all 3 Fagaceae species could form EM with the 4 different fungal species (CeSSHl from FSI, Pisolithus tinctorius, Rhizopogon piceus and Scleroderma verrucisum) under nursery conditions. Similar to many pervious studies, the inoculation of EM improved the growth of the three Fagaceae species significantly. It was once again demonstrated that the importance of using mycorrhizal techniques on the growth of Fagaceae seedlings. The inoculated fungal species showed various levels of growth effects on different Fagaceae species. However, there was a trend that all of the artificial inoculated fungal species were gradually replaced by a contaminated fungal species Scleroderma verrucisum (Sv) in the late stage of the experiment. Probably Sv has higher adaptability of the harsh nursery environment than the inoculated fungal species. The results suggested nursery adaptability should be considered during fungal species screening. Common nursery practices, including the application of chemical fertilizer, pesticide, fungicide and the use of plastic tube container, showed various effects on the EM formation and the growth of the C. concinna seedlings. The use of plastic tube container caused waterlogging and root bound in the late experimental period (6 months) thus inhibited the EM development obviously. The application of fertilizer improved the early seedlings growth but inhabited the formation of mycorrhiza thus slowed down the growth rate afterward. The application of fungicide and pesticide had no significant effect on the EM colonization. The use of suitable type of containers (i.e. root-trainer) and optimized amount of fertilizers are necessary for ectomycorrhizal seedling production. In conclusion, it is no doubt that the use of mycorrhizal techniques can improve the growth of Fagaceae seedlings. To provide reproducible and consistent results, certain criteria should be fulfilled for the production of ectomycorrhizal containerized Fagaceae seedling: 1. conducting fungal-host compatibility screening under nursery environment; 2. selecting fungal species have high adaptability and competitive ability; 3. using suitable container to prevent poor root development and 4. using suitable types and optimal amounts of fertilizer, pesticide and fungicide.