The fungal succession under Scots pine on a sandy soil in Surrey

I started to study the sheathing (ecto)mycorrhizal fungi of conifers on a sandy heath at Liphook, near Guildford, in 1986.  The trees were 1 year old saplings of Scots pine, Norway and Sitka spruce.  These saplings had been planted as part of an experiment by the late-lamented CEGB to study effects of the pollutatnt gases sulphur dioxide (SO2) and ozone (O3) on tree health.  One of my jobs was to monitor the fungi.  We also did "proper" lab work and issued research contracts to ITE (now CEH), but I can honestly claim to be the only person employed by the CEGB to count toadstools!

The rationale here was that the fungi to be studied were ecto-mycorrhizal, forming a protective sheath around roots and assisting with nutrient uptake.  In return the tree supplies the fungus with sugars.  Damage to these fungi would be a predictor of tree ill health, so the fungi had to be counted!.

In the first year of fruiting only three fungi came up, all well known "nursery" fungi, generalist ectomycorrhizal species which probably make minor sugar demands on their hosts.  These were the deceiver Laccaria proxima, the common roll-rim Paxillus involutus, and the earth fan Thelephora terrestris (Table 1, below).  There was no host-specificity, except for Thelephora which tended to be commonest under Sitka spruce.
 

Table 1: the "Nursery" fungi.
These form ectomycorrhizas with the youngest trees and are common all over the country. They were the only species fruiting in the Liphook plots in 1986 (1 year after planting).
 

Laccaria proxima - the deceiver.  It lived up to its name - for years I called it Laccaria laccata, until Geoff Kibby put me right.


 
Paxillus involutus - the common roll rim.  Note the inrolled edge to the cap.  Although sometimes eaten, this is best regarded as poisonous, causing cumulative haemolysis.

Thelephora terrestris - the earth fan, lining a small soil pit.  This is a ubiquitous fungus on very young trees, and was especially common under Sitka spruce in the early days at Liphook.  You may just make out a toad at the bottom of the pit.

It was impossible to count this diffuse crust in the same way I counted toadstools, so I simply recorded presence.

 

By 1988 a rather more diverse fungal community was established, dominated numerically by Suillus bovinus (below, far right with yellow-brown cap).  This fungus is a bolete, so has spongy foam gills.  It has a shy accompanier: Gomphidius roseus (below, centre) which always fruited with Suillus bovinus, though in much smaller numbers.  Supposedly it needs a hormone secreted by Suillus in order to fruit, but I can't give you a reference to support this story.  (A similar relationship exists between Boletus piperatus and Amanita muscaria: in this case the bolete seems to depend on its gilled partner to initiate fruiting.)
 
 

Table 2: the early successional fungi.
These species first fruited in the Liphook plots in 1987 (2 years after planting).
 

This photo shows 3 early successional species together: from left to right Laccaria proxima, Gomphidius roseus, and Suillus bovinus.  Gomphidius roseus seems to depend on the presence of Suillus bovinus to fruit, although Suillus is well able to fruit on its own.


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Boletus subtomentosus - closely related to B. ferrugineus) .  Curiously, this species first fruited in small numbers in 1987, and has appeared in small numbers most years since with no sign of either increasing or disappearing.

Suillus variegatus.  This species flourished from 1988-1990, then effectively vanished.


 

1988 saw the first appearance of Cortinarius, Lactarius and Inocybe species, typically associated with relatively mature trees.  Still no clear host specificity, though Norway spruce sectors were rather poor in species and numbers - the Norways had never much liked this dry sandy soil and were badly stunted.  (Still are in fact - ideal Xmas trees!)

Table 3: early successional fungi.
These species first fruited in the Liphook plots 1988-89 (3+ years after planting).
 

Cortinarius semisanguineus (left, with orange gills) and C. croceus (right, yellow gills).  Separating these two involves checking the gills as the caps are virtually identical.  To confuse matters further, a third species (C. cinnamomeobadius) appeared in the 1990s, identical except for its browny-yellow gills.


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Inocybe lacera.  A scaly little brown Inocybe, said to be associated with pines on sandy soils.

Lactarius rufus - the rufous milk cap.  Very common under pine trees throughout the country, usually in the top 3 commonest species in any of my pine plots after 1990.  Like all Lactarius species, the cap contains a milky latex whose taste is often of diagnostic value.  This one has a pleasantly hot, spicy taste and has powdered for use as a condiment.  Other species have vastly worse tastes!

 

1991 was a bad year for my Liphook work.  The CEGB (RIP) had been privatised, and my new employer National Power didn't see my toadstool-counting as relating to the core activities in their corporate mission statement...  I intended to go along at weekends, but you know how it is with weekends, and I lost a year's data.  1992 I jumped the sinking ship that was NP research and started with Roehampton, who were happy for me to go back to my pine forests.  I returned to find that two species of Amanita (rubescens and muscaria) had started to fruit.  I still rankle over that missed year.

In the intervening period the site had been stripped of equipment and the path abandoned.  The conifers had closed canopy, and getting around the site was physically very difficult.  I changed my sampling strategy for 1992 to reflect changed times.  Firstly I decided to ignore the Norway and Sitka spruces, for the simple reason that their branches sprawled out at ground level like a very spiky ballgown, making toadstool counting virtually impossible without crawling on all fours.  Their needles were also extremely sharp, spiking contemptuously through trouser material.  By contrast the pines were so tall that their lower branches were dead and could be cleared without harming the trees.  Hence I spent August 1992 clearing walkways in the pine sectors of each plot, producing a network of little paths that I have used ever since.  It did mean that I lost the spruce successions, though in practice I can still see into spruce sectors and don't seem to be missing much (apart from the disgusting-tasting ugly milk cap Lactarius turpis, which seems to be a spruce speciality at this site).
 

Table 4: Later successional Scots pine fungi.
These species first fruited in the Liphook plots in 1990 onwards (5+ years after planting), and included some of the largest and most familiar species.  The species at the bottom of the table came in so recently that I'm not going to graph them until the 1999 data are sorted and entered.
 

Amanita rubescens - the blusher (so called because its flesh reddens on bruising).  Edible after boiling, but anyone who eats Amanitas is braver than me!  Appeared in 1992, but so far always a scarce species.

Amanita muscaria (centre, red) appeared in 1992.  Here shown next to a large Paxillus involutus (centre right, with gills) and some Suillus bovinus (with the foamy pores instead of gills).


Boletus edulis, the cep or penny bun, held by Prof Jack Rutter (Silwood park).  This is one of the best edible species and is a key ingredient of canned mushroom soup. It first appeared in 1990 and now has 2 well-defined fruiting patches (plots 6 and 4).

This difficult grey-brown thing that tried to convince me it was a Hebeloma but actually turned out to be Cortinarius candellaris.		 Cortinarius obtusus.  This pointy little species comes in a variety of sizes and shapes, causing me many ID problems!
Laccaria bicolor.  The cap is similar to Laccaria proxima, but the stem base is a glorious purple.  This species has only ever fruited in one spot, the south end of plot 2, but it has steadily expanded its territory and now occupies about half of this sector.

 
 

By 1996 I had 10 years of data, and the initial rapid changes were settling down.  If anything the succession appeared to be going backwards, with Laccaria proxima re-appearing in spots where Amanita muscaria once fruited.  I thought it very likely that the pine trees were showing the strain of being far too overcrowded - they were now >5m tall but still at 1m spacing, so were tall thin lanky things.  Such striplings might not have enough spare sugars to nourish hungry ectomycorrhizas?   I decided to impose a new treatment at the site by thinning 1 sector out of the 2 in each plot.  This took up a fair part of my sabbatical term, and the 50% thinning imposed created pleasant-feeling glades in the now dense young forest.

The limited data I have so far suggests that the thinning treatment has benefitted Suillus bovinus and Cortinarius semisanguineus in every single plot - except for plot 3, where the opposite trend is clearly apparent (I'm still scratching my head about this one).  I think I'll use DECORANA to give me a successional index for each sector for before and after thinning, then test H0: No change in differences between thinned and unthinned within each plot as a consequence of treatment.

Table 5: 10 years on.
These species first fruited in the Liphook plots in 1995 onwards (10+ years after planting), by which time the community was quite species-rich with some taxonomically awkward species!  Sadly I am still in need of decent photos of most of these species.
 
Scleroderma citrinum.  This earthball is confined to the northern sector of plot 1, where it is the dominant species. Cortinarius cf obtusofuscus.  This one totally floored me, and even Geoff Kibby assures me that it doesn't coincide exactly with "standard" species.
Lactarius hepaticus - a small milk cap with a liver-coloured cap.
Russula aeruginea.  This species only fruits in one area in the north sector of plot 4, and always seems to produce very tatty half-buried specimens. Russula delica.  This white Russula is also confined to the north sector of plot 4.

The result of 5 years of thinning (1997-2002) were published in 2003.  In summary, thinning the pines boosted yields of 3 species (Suillus bovinus and its commensal (?) Gomphidius roseus, also Cortinarius semisanguineus), but overall had very little effect on community structure.  Not wildly exciting, but that is how science advances.   And my overview of the succession?  That each sector is acquiring a dominant fungus, elbowing out the generalists.  South sectors of plots 6 and 4 have Boletus edulis, north sector of plot 4 has Russula spp, north sector of plot 3 and south sector of plot 1 have Amanita muscaria, north sector plot 1 has Scleroderma citrinum, and south sector of plot 2 has Laccaria bicolor. This makes intuitive sense, but does make the multivariate analyses rather suspect, as replication becomes replaced by individual trajectories in species space.

Two disasters have befallen this Liphook dataset.  The first was a simple climatic problem that the autumn of 2003 was very dry (as many mycologists will remember with sadness), and hardly a fruitbody emerged in any of the 7 plots that year.  2004 was much damper and had generous fruiting, but the forestry commission chose to start thinning the site, leaving cut lines and piles of brash over plots 4-7 and making further census work impossible, at least until the brash has been cleared.  Consquently it is most unlikely that further quantitaitive data will emerge from these plots now (although species names can still be garnered).  The main dataset (to be precise a tidied-up version of it) is used as a test-bed for various multivariate analyses in my book 'Multivariate Statistics for the Environmental Sciences'.

Relevant Publications:

Shaw, PJA (2003).  Multivariate Statistics for the Environmental Sciences. Hodder Arnold.

Shaw PJA, Kibby G & Mayes J (2003).  Effects of thinning treatment on an ectomycorrhizal succession under Scots pine.  Mycological Research 107, 317-328.

Shaw, P.J.A. & Lankey, K. (1994)  Studies on the Scots pine mycorrhizal fruitbody succession.  The Mycologist 8, 172-175.

Shaw, P.J.A. (1993).  Studies on the mycorrhizal community infecting trees in the Liphook forest  fumigation experiment.  Agriculture, ecosystems and environment, 47, 185-191.

Shaw, P.J.A., Dighton, J. and Poskitt, J. (1992).  Studies on the effects of SO2 and O3 on the mycorrhizal succession under Scots pine and Norway spruce as observed above and below ground. Mycorrhizas in Ecosystems (Eds. DJ Read, DH Lewis and IJ Alexander), pp. 208-213.

Shaw, P.J.A., Dighton, J., Poskitt, J. and McLeod, A.R.  (1992)  The effects of sulphur dioxide and ozone on the mycorrhizas of Scots pine and Norway spruce in a field fumigation system.  Mycological Research 96 785-791.

last modified 4-4-2005

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