Elder Woodland

Birch and Elder wood

This grove, seen in winter, is dominated by Elder (Sambucus nigra) and Cherry (Prunus) trees. The Cherry trees are the ones with grey-red bark arranged in horizontal strips. The Elder trees (on the right and in the background) have the deeply furrowed brownish bark which retains a lot of moisture and so supports a rich variety of epiphytes, including mosses and lichens.

Elder is usually encountered as a small shrub putting out a number of stems from its base (this additional branching is triggered by cool nights) but by about 20 to 30 years of age this shooting stops and a single stem becomes dominant and the Elder may become a small tree. Elders do not live long by tree standards but have been recorded up to 44 years of age. Birches are also relatively short-lived, rarely exceeding 80 years of age.

Elder prefers the edges of woodlands where the canopy is more open and there is more light, but may persist for some time in darker more mature woods. it occurs in scrub where woodland is regenerating, before larger trees over-shadow it. This grove is quite open, especially in winter and the light reaching the floor supports a luscious carpet of moss, overwintering rosettes of flowering herbs and some grasses.

Moss

The main moss growing across the floor of this grove is a type of Feather Moss. This moss has carpeted the soil and fallen branches and climbed part-way up the bases of the trees. Feather mosses belong to an order of mosses called Hypnales and each plant consists of a a feather-like shoot with a main stem and several branches. The branches may themselves branch again to bear secondary branches. The spore capsule is borne on a relatively long stalk or seta about 2 cm tall.

Moss

A closer examination reveals the species: Kindbergia praelonga, the Common Feather-moss.

Moss

One feature is the rough texture of the reddish seta due to its covering of wart-like protuberances or papillae (the seta is said to be papillose).The capsule is held inclined to the horizontal. Beneath the calyptra (remains of the archegonium from which the seta grew, which can be seen as a cap or hood on the end of the capsule) is the operculum (lid) which is long and beak-like. Both the calyptra and operculum detach when the capsule is ripe and ready to shed its spores. This moss is dioicous, meaning their are separate male and female plants. Only female plants can bear a seta and capsule (which along with the foot of the seta is the diploid sporophyte, the leafy part of the plant being the haploid gametophyte). The leaves on the gametophyte enclosing the foot of the seta are modified and have more pointed tips and form a cup for the seta foot called the perichaetium. The haploid spores (formed by meiosis) give rise to new gametophytes when they germinate.

Moss

With the calyptra removed, the characteristic beaked operculum of Kinderbia praelonga becomes apparent.

Moss

Another distinguishing feature can be found in the leaves (shown here in transmitted light). Although many mosses have larger leaves on the stem than on the branches, in Kindbergia praelonga the leaves are distinctly different shapes. The branch leaves, above, are narrower whilst the stem leaves (below) have much broader bases with distinctive lobes where they wrap around the stem.

Moss

Moss

Elder also occurs wherever the ground has been disturbed, often growing in woods at the location of old rabbit warrens and badger sets. The leaves of elder contain cyanogens which generate poisonous hydrogen cyanide when the leaf is crushed and the crushed leaves release a fetid odor so rabbits tend to avoid eating them, though deer may eat the leaves. As rabbits clear competitors from the area, such as grasses, elder seeds are more likely to germinate and thrive.

Elder Flowers

In summer the flat-topped clusters of white flowers can be found, producing dark red berries. Both the flowers and the berries can be used to make wine, though eating the raw berries in quantity can have toxic effects on some people.

Elder is a useful component of the ecosystem supporting epiphytes and also the Jelly-Ear Fungus (Auricularia auricula-juda) shown below:

Jelly Ear fungus growing on Elder

The Jelly Ear fungus prefers to grow on old and also dead Elders, as here (but sometimes occurs on other broadleaf trees).

Jelly Ear fungus growing on Elder

This jelly fungus is jelly-like when moist but becomes brittle when dry, but springs back into life when rehydrated. In this instance the temperature was about -1 degrees C and the fungi were frozen solid. I expect they will revive once thawed.

Jelly Ear fungus growing on Elder

The Jelly Ear Fungus belongs to a class of fungi called the ascomycetes. These fungi produce sporing-bodies (often called fruiting bodies), the visible part of the fungus, with a 'hymenial surface' (or hymenium) covered with microscopic hairs. Some of these hairs are minute cylinders or flasks filled with a definite number of spores and these spores are fired out under pressure. The hymenial surface is the lower surface of these Jelly Ear Fungi.

Jelly Ear fungus growing on Elder

The Jelly Ear Fungus is more usually known as the Jew's Ear Fungus, apparently after Judas Iscariot, though it has been suggested that the name has darker roots in cultural prejudice. I think Jelly Ear Fungus is a better name.

Jelly Ear fungus growing on Elder

Jelly Ear fungus growing on Elder

The jelly-eared fungi, having thawed have resumed growth.

Elder tree bark is deeply furrowed and retains moisture well, encouraging a variety of epiphytes. The main moss occurring on the trunks of the Elders is Orthotrichum diaphanum (White-tipped Bristle Moss). The Orthotrichum mosses are also known as Bristle Mosses. Several species of Orthotrichum may occur on the same tree, each with its own preferences. For example, the larger Orthotrichum affine prefers branches and stems that are more-or-less horizontal and also nooks and crannies like knot holes.

Elder and Birch

Different species of Orthotrichum can be hard to tell apart, but O. diaphanum has translucent white (hyaline) tips (awns or hair-tips) to its leaves and 16 outer peristome (exostome) teeth on its ripe capsules. The larger O. affine lacks the hyaline tips, has 8 outer peristome teeth and is generally a much larger moss (0.8 to 3.5 cm tall, whereas O. diaphanum is generally less than 1 cm tall). In both, the outer peristome teeth fold backwards when the capsule is open. The ripe capsules turn brown and are furrowed when dry. The peristome teeth cover the end of the capsule beneath the operculum and become visible once the calyptra and operculum have been shed. Their are two rings of peristome teeth in general: inner and outer and these may open and close over the end of the capsule in many moss species, opening when conditions are dry enough for efficient spore dispersal.

Elder and Birch

Notice the differences with the feather moss: Orthotrichum plants are upright, the feather mosses have more horizontal shoots that are branches and feather-like; the Orthotrichum capsule has a shorter beak and in some species, including Orthotrichum diaphanum, the capsule is partially hidden by the surrounding leaves (semi-emergent) due to the much shorter seta.

Orthotrichum diaphanum prefers the bark of Elder and also Ash, Grey Willow and Sycamore trees (and less often on the bark of other broadleaved trees). It, like its Elder host, prefers more light than the deeper parts of the wood. It develops capsules mainly on Elder shoots over about 6 years in age, but is generally replaced by other mosses on older shoots over about 10 years of age.

Elder and Birch

Elder and Birch

Above and below: The taller moss Orthotrichum affine occurs on the more horizontal parts of the branches and in the nooks between forks on the Elder trees. Note the hairs on the calyptra (hood) covering each unripe spore capsule.

Elder and Birch

Elder and Birch

Below: The feathery fronds of Kindbergia praelonga is also growing on older parts of the elder trunks, along with another moss:

Moss

Brachythecium rutabulum (Rough-stalked Feather-moss) one feature of this moss is the light-colored shoot tips. These can be seen towards the center of the above image, with the more feathery Kindbergia praelonga growing below.

Moss

A closer look at the capsule reveals a similar red roughened seta to that found in Kindbergia praelonga, and the two mosses both belong to the order Hypnales (Feather Mosses) and so have certain similarities, but the operculum of Brachythecium rutabulum lacks the distinctive elongated beak of Kindbergia praelonga.

Moss

Above: a capsule of Brachythecium rutabulum. The operculum or lid is not distinctly beaked and will be shed when the capsule is ripe and ready to shed spores. The peristome teeth (see below) can be seen beneath the operculum.

The peristome is the set of 'teeth' at the end of the moss capsule, beneath the operculum. Both Brachythecium rutabulum and Kindbergia praelonga have a perfect peristome, meaning that it consists of two complete sets of teeth: the outer whorl (exostome) of 16 teeth and the inner whorl (endostome) of 16 more delicate teeth. The peristome in both these species is also xerocastique which means that the outer peristome opens in dry conditions, allowing spores to be dispersed, and closes in moist air. This opening and closing is very rapid (taking one to a few seconds) and is easily observed under the microscope.

Moss

Above: a capsule of Brachythecium rutabulum with the exostome open in dry conditions, ready for spore dispersal.

Elder bark

Above and below: the orange alga Trentepohlia is yet another epiphyte found growing on Elder bark in this grove. This alga forms filaments of cells and is a type of chlorophyte or green alga, though the green color of its chlorophyll is masked by the orange carotenoid pigments.

Elder bark

Elder bark

Below: the moss Orthotrichum affine and the alga Trentepohlia growing along with another epiphyte: the lichen Parmelia. Lichens are composite organisms consisting of algal (and/or cyanobacterial) cells growing in symbiosis within the body of a fungus. The fungus is completely dependent on its photosynthetic partner (or photobiont), but sometimes the photobiont can also exist independently. These elder trees truly are extraordinary ecosystems!

Elder bark

Elder and Birch

Young leaves of Elder

Above: Elders are one of the first deciduous trees to put out leaf. Here some buds have expanded partially even though it is only winter in mid-January. The buds of Elder occur in opposite pairs and in a decussate arrangement (with each pair at 90 degrees to the next pair along the twig). The buds are a peculiar 'half-open' type in which the bud scales cover and protect the enclosed leaves only partially, as if every bud is ready to spring into action at a moment's notice, as this one has done. This helps the Elder compete for light with taller trees.

Page created: 11 Jan 2021

Page updated: 16 Jan 2021, 18 Jan 2021, 30 Jan 2021