(Arboricultural-styled) 'Fact of the Day'

[sandspider]

Well, I'm looking to plant and manage my own small woodland in the not too distant future, so anything vaguely useful in that direction would be great.

 

Many thanks.

[Kveldssanger]

Got one coming up. It'll be copied over from my notes, so may read slightly note-like.

[Kveldssanger]

29/10/15. Fact #66.

 

It is quite clear that within most derelict land soils the nitrogen supply is far too low to meet minimum plant requirements unless fertilizers or nitrogen fixing species are planted, though as fertiliser requires expenditure over and above the planting of the woodland and as benefits of fertiliser are somewhat contested, loking to plant nitrogen-fixing species is likely to have a more long-term and positive impact upon the soil.

 

One genus that can be of great aid is Alnus spp., which have a close symbiosis with the Frankia genus (actinomycetes) that are found within the nodules of the fine roots. This relationship facilitates the nitrogen fixation process. Such fixation ensures that nitrogen supply can be improved in time, providing progressively improving soil conditions that brings about a more optimal state for more demanding species to then enter and thrive within.

 

For instance, trials in the US have found that Juglans nigra stands have grown at a better rate when planted alongside Alnus glutinosa. Whilst an increase in growth rate varied between sites, at times not assisting with any significance, certain sites saw growth rates increase from 56%-351%.

 

It should be noted however that Alnus-dominated environments tend to be phosphorus-lacking, so caution should perhaps be exercised with regards to a very heavy reliance upon Alnus spp. exclusively; though as the woodland starts to develop and new species establish the soil environment will respond to such development by containing a broader range of mycorrhizal bacteria species, which will on the whole supplement phosphorus uptake of plants. It is however understood that, even when nitrogen-fixing species occupy only a small part of the total woodland biomass, their effects are significantly beneficial.

 

Curiously, Alnus spp. are viewed (by some) as "forest weeds" and are removed in certain instances. It is critical that this doesn't occur unless there is over-riding need to do so, as removal can trigger event chains that may cause imbalance within the entire developing woodland ecosystem.

 

There is even a subtle symbiosis between nitrogen fixation by Alnus spp. and subsequent utilisation by Pinus spp. through commonly-shared ecotmycorrhizal mycelium, which may aid with growth of the latter as a result. This leads on to utilising Pinus sylvestris as a nurse species, particularly for when Quercus spp. are planted alongside.

 

To round-off this post, the planting of species such as scots pine, aspen, and birch as nurse species, which colonise recently disturbed ground and are successional species, may also aid with site improvement. Improving soil condition and biomass accumulation (as well as being shade intolerant [thus being a more 'temporary' woodland feature] and offering dappled shade and shelter for climax species when such climax species are in their infancy), they will rarely succeed into the second generation once more dominant canopy species begin to reach the canopy layer; their selection has thus been shown to improve vitality and growth form of species such as oak and beech.

 

Sources:

 

Arnebrant, K., Ek, H., Finlay, R., & Söderström, B. (1993) Nitrogen translocation between Alnus glutinosa (L.) Gaertn. seedlings inoculated with Frankia sp. and Pinus contorta Doug. ex Loud seedlings connected by a common ectomycorrhizal mycelium. New Phytologist. 124 (2). p231-242.

 

Balandier, P., Sinoquet, H., Frak, E., Giuliani, R., Vandame, M., Descamps, S., Coll, L., Adam, B., Prevosto, B., & Curt, T. (2007) Six-year time course of light-use efficiency, carbon gain and growth of beech saplings (Fagus sylvatica) planted under a Scots pine (Pinus sylvestris) shelterwood. Tree Physiology. 27 (8). p1073-1082.

 

Bardgett, R. & Wardle, D. (2010) Aboveground-Belowground Linkages: Biotic Interactions, Ecosystem Processes, and Global Change. UK: Oxford University Press.

 

Campbell, G. & Dawson, J. (1989) Growth, yield, and value projections for black walnut interplantings with black alder and autumn olive. Northern Journal of Applied Forestry. 6 (3). p129-132.

 

Ekblad, A. & Huss-Danell, K. (1995) Nitrogen fixation by Alnus incana and nitrogen transfer from A. incana to Pinus sylvestris influenced by macronutrients and ectomycorrhiza. New Phytologist. 131 (4). p453-459.

 

Gilman, E. (2004) Effects of amendments, soil additives, and irrigation on tree survival and growth. Journal of Arboriculture. 30 (5). p301-310.

 

Granqvist, E., Sun, J., Op den Camp, R., Pujic, P., Hill, L., Normand, P., Morris, R., Downie, J., Guerts, R., & Oldroyd, G. (2015) Bacterial‐induced calcium oscillations are common to nitrogen‐fixing associations of nodulating legumes and nonlegumes. New Phytologist. 207 (3). p551-558.

 

Mason, W. (2000) Silviculture and stand dynamics in Scots pine forests in Great Britain; implications for biodiversity. Forest Systems. 9 (1). p175-197.

 

Põlme, S., Bahram, M., Kõljalg, U., & Tedersoo, L. (2014) Global biogeography of Alnus‐associated Frankia actinobacteria. New Phytologist. 204 (4). p979-988.

 

Prévosto, B. & Balandier, P. (2007) Influence of nurse birch and Scots pine seedlings on early aerial development of European beech seedlings in an open-field plantation of Central France. Forestry. 80 (3). p253-264.

 

Smalley, T. & Wood, C. (1995) Effect of backfill amendment on growth of red maple. Journal of Arboriculture. 21 (5). p247-247.

 

Smith, S., Jakobsen, I., Grønlund, M., & Smith, F. (2011) Roles of arbuscular mycorrhizas in plant phosphorus nutrition: interactions between pathways of phosphorus uptake in arbuscular mycorrhizal roots have important implications for understanding and manipulating plant phosphorus acquisition. Plant Physiology. 156 (3). p1050-1057.

 

Wheeler, C. (1971) The causation of the diurnal changes in nitrogen fixation in the nodules of Alnus glutinosa. New Phytologist. 70 (3). p487-495.

Edited October 29, 2015 by Kveldssanger

[Gary Prentice]

Chris, Just a quick question on 'mycorrhizal bacteria species'. This is the first time I think I've ever seen the term. Any suggestions on further reading?

[sandspider]

Thank you, that's good stuff.

 

As it happens, alder and birch are already on my desired species list - alder for it's N2 fixing abilities (and decent firewood / charcoal) and birch as I like it as firewood and as it's a good colonising species.

 

Didn't know quite how much difference in growth rates the alder could make though!

[Kveldssanger]

Chris, Just a quick question on 'mycorrhizal bacteria species'. This is the first time I think I've ever seen the term. Any suggestions on further reading?

 

Typo - I meant fungi, or more broadly just mycorrhizal species.

[Gary Prentice]

Thank god for that, I suddenly thought that there may be a huge deficit in my, admittedly sparse, knowledge.

 

At least you know I'm paying attention.

[Kveldssanger]

Thank you, that's good stuff.

 

As it happens, alder and birch are already on my desired species list - alder for it's N2 fixing abilities (and decent firewood / charcoal) and birch as I like it as firewood and as it's a good colonising species.

 

Didn't know quite how much difference in growth rates the alder could make though!

 

[Kveldssanger]

Thank god for that, I suddenly thought that there may be a huge deficit in my, admittedly sparse, knowledge.

 

At least you know I'm paying attention.

 

Hahah. Your knowledge is not sparse!

[daltontrees]

I'm confused. If Alnus can create better plant growth conditions because it can fix Nitrogen (with F. alni), why does it create Phosphorus poor conditions? i.e. if it accumulates both N and P why and how does it make N available to other plants but not P? Sorry, complex question, but I don't have access to Jakobsen et al.