View() is not the correct fucntion to use for displaying the output of ggplot(). You should use print(), either explicitly or implicitly by simply writing the name of the object. Either of these should work.
boxplot1 <- ggplot(biomass,aes(x=Tree_biomass,y=State,fill=Type))+
geom_boxplot(outlier.color="grey") + geom_jitter()
print(boxplot1)
boxplot1 <- ggplot(biomass,aes(x=Tree_biomass,y=State,fill=Type))+
geom_boxplot(outlier.color="grey") + geom_jitter()
boxplot1