WRW #8: Riverside Gardens - Spot the Shyness!
The cache, a small camo-taped tablet pot, is hidden in a huge American Sycamore amongst a group of these trees in these delightful gardens which opened in 1953.
***Please ensure it is properly replaced and concealed using the materials provided - thanks!***
To reach the cache location: park on the west side of the New Bridge at or near @ N 53 55.670 W 1 49.411, take the steps heading down to the gardens and head ~150m west along the riverside trail to the cache location.
Alternative parking is usually available in the car park of the riverside pub @ or near N 53 55.717 W 1 49.698.
If you look up towards the sky from GZ you will notice a strange effect in the tree canopy of the nearby sycamores . . . crown shyness!
Also known as canopy disengagement, canopy shyness, or intercrown spacing, this is a phenomenon observed in some tree species, in which the crowns of fully grown trees do not touch each other, forming a canopy with channel-like gaps.
The phenomenon occurs most often in trees of the same species, but also occurs between trees of different species. There are many theories as to why it is an adaptive behaviour, and research suggests that it might inhibit the spread of leaf-eating insect larvae.
Although it has been discussed in scientific literature for almost 100 years, the exact physiological basis of crown shyness is not certain. The variety of hypotheses and experimental results might suggest that there are multiple mechanisms involved across different species, an example of convergent evolution.
Interdigitation (interlocking) of canopy branches leads to 'reciprocal pruning' of adjacent trees. Trees in windy areas suffer physical damage as they collide with each other during strong winds. As the result of abrasions and collisions, there is an induced crown shyness response.
Studies suggest that lateral branch growth is largely uninfluenced by neighbouring trees until disturbed by mechanical abrasion. If the crowns are artificially prevented from colliding in the winds, they gradually fill the canopy gaps. This explains instances of crown shyness between branches of the same organism. Proponents of this idea cite that shyness is particularly seen in conditions conducive to this pruning, including windy forests, stands of flexible trees, and early succession forests where branches are flexible and limited in lateral movement. So, variable flexibility in lateral branches has a large bearing on the degree of crown shyness.
Similarly, some research suggests that constant abrasion at growth nodules disrupts bud tissue such that it is unable to continue with lateral growth. It is thought that trees' growing tips are sensitive to abrasion, resulting in canopy gaps.
A prominent hypothesis is that canopy shyness is related to mutual light sensing by adjacent plants. The photoreceptor-mediated shade avoidance response (impress your friends with this wonderful phrase!) is a well-documented behaviour in a variety of plant species. Neighbour detection is probably a function of several unique photoreceptors. Plants are able to sense the proximity of neighbours by sensing backscattered far-red (FR) light, probably through phytochrome photoreceptor activity.
Many plant species respond to an increase in FR light (and, by extension, encroaching neighbours) by directing growth away from the FR stimulus and by increasing the rate of elongation. Similarly, blue (B) light is used by plants to induce the shade-avoidance response, likely playing a role in the recognition of neighbouring plants.
This suggests that crown shyness is simply the result of mutual shading based on well-understood shade avoidance responses. Growing tips are sensitive to light levels and stop growing when nearing adjacent foliage due to the induced shade.
See here for a short video of the gardens and river including the area near the cache at 1:22