*Recap: This year, we’ll be focusing on two main objectives: 1. Determining the effects of floral diversity on bee visitation rates to coffee, and 2. Identifying the effects of coffee management practices on coffee floral traits.*
🙂 I couldn’t think of an exciting title for this post, so please forgive the lame name!
But in all seriousness, the field season is off to a great, but slow start. If you remember my posts last year, I was desperate for flowers to bloom, and when they bloomed, I was in a huge rush to get my pollination manipulation done, since the flowers are only open for 1-2 days. Well…this year, La Nina caused more than normal rains, resulting in a wetter month of December and January. Since the coffee flower bloom is initiated with rain after a short period of dry weather, the flowers have been blooming earlier than normal, this year. Arabica coffee, which should bloom in late February- early March is already blooming in some farms! And Robusta coffee already had its first bloom by the second week of January. That being said, I’m not despairing yet, since I can already see the buds from the next flowers, and I know it’s just a matter of time before they bloom.
So, why am I so concerned about the flowers? Well, essentially, my two main objectives for this year revolve around studying coffee flower traits and coffee flower visitors, so without flowers, I can’t do anything. What are coffee flower traits, you ask? Well, it’s essentially all the things that make a flower look, smell and taste the way they do – these are really important for attracting bees. My co-advisor, Dr. Rebecca Irwin conducted a study with one of her students looking at the effect of fertilizers on floral traits (in the US) and found that different levels of fertilizers affected the floral traits. So, based on that study, and knowing that soil in shade coffee farms differs greatly from soils in sun coffee farms, I thought it’d be interesting to see if the flowers differ too.
- shade coffee farms have a steady amount of leaf litter dropping from the shade trees
- shade coffee farms have higher soil moisture levels due to the leaf litter retaining the moisture
- shade coffee farms have shade trees, which are nitrogen fixing, thus adding some nutrients into the soil in addition to chemical fertilizers
- sun coffee farms have no leaf litter
- sun coffee farms have dry soils that erode easily
- sun coffee farms rely exclusively on chemical fertilizers
To determine if the coffee floral traits differ from shade to sun coffee farms, we’re measuring all of the following.
- floral shape measurements (including size, number of petals, stigma height)
- nectar standing crop – the amount of nectar available in the flower when it first opens
- nectar sugar concentration – measured in Brix, we can tell how sweet the nectar is.
- nectar caffeine content – caffeine isn’t just something for us humans. Caffeine was actually found to affect bees’ memory, increasing their loyalty to flowers with caffeine (i.e. once they drink the caffeinated nectar, they may be more likely to go to coffee flowers than other flowers with no caffeine)
- pollen standing crop – how much pollen is on the flower when it first open
- pollen protein content – pollen is nutritious for bees, so they may opt to go back to flowers that are more nutritious.
This is a lot of data to collect, so I’m super grateful to my technicians for helping me get the work done!
The second main objective this year, is to observe coffee flower visitors and see if they are in fact staying loyal to coffee, or if they’re going from coffee to shade trees, or from coffee to wildflowers. Essentially, we want to test if floral diversity (higher in shade than in sun) is positively, negatively, or not affecting coffee flower visitation. We haven’t gotten started on that part yet, that’s what I created the bee identification field guide for.
More to come, but let’s hope Pacha Mama keeps things as they are, so that my work can continue as smoothly as it has so far!