The legacy effects of rubber defoliation period on the refoliation phenology,leaf disease,and latex yield

The leaf phenology of trees has received particular attention for its crucial role in the global water and carbon balances,ecosystem,and species distribution.However,current studies on leaf phenology have mainly focused on temperate trees,while few studies including tropical trees.Little attention has been paid to globally extensive industrial plantations.Rubber plantations are important to both the local and global economies.In this study,we investigated the legacy effects of defoliation phenology on the following year’s leaf flushing,leaf disease,and also latex yield of rubber trees,an economically important tree to local people and the world.Results show that extended duration of defoliation increased the subsequent duration of refoliation and rates of infection by powdery mildew disease,but led to reduced latex yield in March.This legacy effect of rubber defoliation may relate to the carbohydrate reserved in the trees.A longer duration of defoliation would consume more reserved carbohydrates,reducing available reserves for disease defense and latex production.Extended duration of defoliation period was associated with either a lower temperature before the cessation of latex tapping in October-November and/or a higher temperature after the cessation of latex tapping in December-January.Leaf falling signals the end of photosynthetic activities in deciduous trees.Thus,the leaf falling phenology will impact ecological processes involving rubber trees.Our findings indicated that the inclusion of defoliation periods in future rubber trees’ research,will be crucial to furthering our understanding of leaf flushing,powdery mildew disease,and latex yield.

Converting tropical rainforest to native rubber plantations alters soil bacterial and fungal communities

Driven by soil biochemistry and plant community composition,soil microbial communities reflect land management and environmental conditions.To evaluate the effects of land-use change on soil microbial diversity,we used denaturing gradient gel electrophoresis(DGGE)combined with sequencing to compare bacterial and fungal community profiles between rubber plantation(RP)and nearby seasonal rainforests(SR).Rainforest soil generally had higher soil total C and microbial biomass C concentration,smaller soil aggregate proportions,and a soil pH below rubber plantation soil.The bacterial and fungal richness and diversity were similar after converting primary forests to rubber plantations.However,the composition of bacterial and fungal communities has significantly changed in rubber plantations.Basidiomycota,the predominant group of fungi,was significantly different between primary forests and rubber plantations.However,Basidiomycota showed higher heterogenetic distribution in the rainforest under rubber plantations.In conclusion,land-use changes mainly affect soil microbial community composition and heterogeneity distribution patterns,especially for saprotrophic fungi,which consist of changes in litter inputs and soil C conditions.