This is a wonderfully poetic and at the same time quite informative piece of short observation captured by the photographer Dimitar Karanikolov. The video successfully demonstrates a botanical phenomenon known as “crown shyness” by providing a nicely stabilized vertical view of canopy trees swaying by the wind in Tulum Mexico. Tree canopies are some of the most diverse sections in tropical forest.
The exact mechanism of crown shyness is still not resolved but there are quite a few convincing hypotheses. Light appears to be playing a dominant role in these. It may be that mutual shading of plants maybe inducing well-studied shade avoidance responses. Studies on a Malaysian tree species Dryobalanops aromatica and another tropical Southeast Asia tree Shorea resinosa suggested that the growing branch tips were sensitive to light levels and stopped growing when in proximity of others due to shading. Photosynthetic machinery of plants is tightly coupled to sensing direction of light. Phytochromes are plant sensors that can detect levels of red light (R) and far red light (FR) abundant in light coming from our Sun. Leaves can filter R light by absorbing that fraction through its light harvesting complexes. Therefore the unabsorbed sunlight reaching further down the plant canopy shifts toward the FR. A tree can sense this through its phytochrome light receptors and can allocate its resources away from that direction. In crown shyness, trees in a way appear to be optimizing to share the available sunlight by toning down exhaustive competition. Therefore photoreceptor-mediated inhibition of growth could be one of the explanations of crown shyness.
The experimental model plant species Arabidopsis shows different leaf placement strategies when grown among close relatives and unrelated conspecifics. Plants were observed to be shading dissimilar neighbors by adjusting leaf orientation while avoiding close relatives. One curious point to pay attention in this video is that crown shyness is observed not only among trees of different species but also among the branches of the same tree.
The video also shows a nice snapshot of striking tropical tree diversity visible by clearly delineated crowns. It is noticeable even by naked eye each tree species have a distinct green reflectance. Ecologists have long wanted to capture this diversity using remote sensing. This dream is now becoming a reality thanks to high-tech tools such as high-resolution hyperspectral thermal imaging mapped onto 3-D LiDAR scanning. To better understand the forest canopies, an ambitious project called Carnegie Airborne Observatory uses an aircraft fitted with laser scanners to generate digitized 3-D canopy structures. This approach proves to be very useful in many fields such as in estimating carbon storage of forests. There’s a couple of similar campaigns by NASA Goddard’s LiDAR, Hyperspectral and Thermal Airborne Imager (G-LiHT) and National Ecological Observatory Network’s (NEON) Airborne Observation Platform (AOP) flying over temperate forests of North America.
G-LiHT aerial campaign demonstrated the power of LiDAR and hyperspectral imaging by documenting the extent of destruction after Hurricane Maria struck Puerto Rico as a Category 4 storm with winds topping 155 miles per hour in September, 2017. Hurricane Maria hugely changed Puerto Rico’s tropical rainforest landscape. NASA Goddard’s G-LiHT team had surveyed Puerto Rico’s forests six months before and after the storm. G-LiHT scanned the forest with 600,000 laser pulses per second and produced its high resolution 3D structure. Comparison of the data revealed that 40 to 60 percent of the canopy trees either lost large branches, were snapped in half or were uprooted by strong winds.
Empowered by instrumentation providing such unprecedented resolution in measurements it is most certainly an exciting time to be a forest scientist!
3 Comments
It’s too late! 🙁