I'm interested to find out if anyone has had success seed-drilling woody species in restoration sites that are dominated by pasture grasses? If so, how have you prepared the site? How have you protected any resulting seedlings from being swamped by regrowth from the pasture grasses?
My first thought is that it is probably impractical given the vigorous growth of pasture grasses, even after spraying. However, I am still interested to find out what experiences researchers or restoration practitioners have had using this technique.
In the soil of abandoned sheep pastures in NW Europe a seed bank of Calluna vulgaris (dwarfshrub) is often present. Removal of the topsoil (usable as garden soil/compost) has been proven to results in (the desired) regeneration of the Calluna heath.
Dear Ross
Generally the success is low. I recomend the following papers:
BONILLA‐MOHENO, M., & HOLL, K. D. 2010. Direct Seeding to Restore Tropical Mature‐Forest Species in Areas of Slash‐and‐Burn Agriculture. Restoration Ecology, 18(s2), 438-445.
CAMARGO, J. L. C., FERRAZ, I. D. K. & IMAKAWA, A. M. 2002. Rehabilitation of degraded areas of Central Amazonia using direct sowing of forest tree seeds. Restoration Ecology v. 10, n. 4, p. 636-644.
ENGEL, V. L., PARROTTA, J. A. 2001. An avaluation of direct seeding for reforestation of degraded lands in central São Paulo state, Brazil. Forest Ecology and Management v. 152, p. 169-181.
Escaio, A. C. ; Corrêa, G. A. P. ; LIMA, J. D. N. ; COELHO, G. C. Emergence and growth of Ateleia glazioveana Baill. seedlings in direct sowing in an early secondary succession stage. Brazilian Journal of Ecology (Impresso), v. 1, p. 34-40, 2012 (avaliable in Research Gate).
GEEVES,G. SEMPLE, B., JOHNSTON, D., JOHNSTON, A., HUGHES, J., KOEN, T., YOUNG, J. 2008. Improving the reliability of direct seeding for revegetation in the Central West of New South Wales. Ecological Management & Restoration v. 9, n. 1, p. 68-71.
HOOPER, E., R. CONDIT, P. LEGENDRE. 2002. Responses of 20 native tree species to reforestation strategies for abandoned farmland in Panama. Ecological Applications, v. 12, n. 6, p. 1626–1641
SIDDIQUE, I., ENGEL, V. L., PARROTTA, J. A., LAMB, D., NARDOTO, G. B., OMETTO, J. P., ... & SCHMIDT, S. 2008. Dominance of legume trees alters nutrient relations in mixed species forest restoration plantings within seven years.Biogeochemistry, 88(1), 89-101.
STEVENSON, B. A., SMALE, M. C. 2005. Seed bed treatment effects on vegetation and seedling establishment in a New Zealand pasture one year after seeding with native woody species. Ecological Management & Restoration vol. 6, n. 2, p. 124-131.
WOODS, K., ELLIOTT, S. 2004. Direct seeding for forest restoration on abandoned agricultural land in northern Thailand. Journal of Tropical Forest Science v. 16, p. 248-259.
Dear Ross
Time ago I used to work in a tropical forest restoration project in Costa Rica (1995), in the Guanacaste Conservation Area. We got around 2000 ha of terrain, with the idea to consolidate a biological corridor among to National Parks (Rincon-Cacao Biological Corridor). All farmers and livestock were taken out of the area. The grass that use to grow in this area was the one called “Star grass” (Cynodon nlemfluensis), which without the influence of livestock, grows incredible, making literally “mattresses” of almost 1.5 m high, making impossible that any seed can reach the soil or grow.
We tested different options, Fire, plowing, plowing+fire. From the results we have learned that plowing+fire was the most effective way, we found seed in the soil after the plowing that probably were there for years, and they react after the fire, and started to grow. We as well noticed that wind and birds were very active as soon the plowing activities (even better in the burned ones) started. We started to notice a lot of herbaceous plants coming to the test areas.
To call the attention of birds, we started to use stakes of trees (Gliricidia sepium and Erithryna sp ), 2 m high, and around 5 cm of diameter collected from live fences in the neighborhoods. The stakes started to sprout and grow, and the birds started to use them as perch, bringing seeds to the tested areas.
Of course plowing was expensive, and not suitable for the full area, and areas with only fire, works for several days, but then the grass came strongest. We started to use seedlings, that we let growing in the nursery for one year, reaching a high around 1.5 m, and took them as “pseudo-stakes” (we called like that), with the roots and pruning some branches, to the field, most of them showed a good response. In this test we used native species, which grew so slow.
Then we move to Gmelina arborea, a tree that can grow 5 m high in less than 6 years, with optimal results. I can share with you some reports from this experience, however are in Spanish. You can check:
http://www.acguanacaste.ac.cr/rothschildia/v2n2/textos/pag17.html
http://investigadoresacg.org/blog/wp-content/uploads/2013/06/Trabajo-Final-Melina.pdf
I will suggest as well to check this references:
Holl, K. 1999. Factors limiting tropical rain forest regeneration in abandoned pasture: seed rain, seed germination, microclimate and soil. Biotropica 31:229-242.
Holl, K. and M. Kappelle 1999. Tropical forest recovery and restoration. TREE 14:378- 379.
I hope it helps
Regards.
David Morales.
The assumption in your question--and please confirm if I am correct or not--is that you are working on the Southern Island of New Zealand, and it is introduced European perennial pasture grasses that are the problem, and the desire is to replant local native New Zealand trees?
If you could give a list of the grasses, that is very important, because on a scale from 1 to 10, to get something established among them can range widely depending on the species.
In general, all grasses produce natural herbicide-like chemicals and unless you eradicate the grass with herbicide first, the natural herbicides from the grasses will battle what you want to do with woody plants, or even other species of grasses, like replacing exotics with local native, like what I am doing at http://www.ecoseeds.com/arastradero.html.
Hi Craig, I would be grateful for a reference on .".all grasses produce.." "..herbicide-like chemicals" (by their roots?). It would bring a new perspective on the wide-spread bush encroachment in Southern African.
Chapter Impact of shrub encroachment on the understory vegetation di...
For references to (the lack of) a seed bank of a temperate tree in abandoned and reforesting pastures see attached.
Article Forecasting the pattern and pace of Fagus forest expansion i...
Hein Van Gils --Thank you for your question. In the Journal of Chemical Ecology in 1993-4 Dr. Liu and team wrote a two-part article in "Biologically active secondary metabolites of barley. II. Phytotoxicity of barley allelochemicals" were the first to devise an experiment to pull out the herbicide-like allelochemicals produced from the roots. In general, all non-riparian plants produce herbicide-like allelochemicals in greater or weaker strengths, from their roots, leaves, stems, branches, bark, etc.
You can produce a computer program, once you know the strength of an individual species, and assign it a number from 1 to 100 based on its herbicide-allelochemical strength, with 1 the weakest, 100 the strongest. and be able to calculate when you put two plant species together, who is going to win the allelochemical battle.
EX SITU ALLELOCHEMICAL TEST. You can see this interaction ex situ, by making teas of the stems or leaves of a suspected allelochemical-producing plant, and soaking some cotton balls with the tea, and then placing 10 viable seeds of other species, and also have one cotton ball with water-only as control, and measure the total seedling stem lengths and root lengths. You might find a natural herbicide better than Roundup?
SOIL NUTRIENTS. However in perennial native grassland situation, like you can see at http://www.ecoseeds.com/desertgrass.html, the grasses if left alone, will beat out the shrubs by using allelochemicals. But when we graze those areas, and never bring back the animal bones, the nutrients are taken out of the soils by the animals, until they no longer have adequate N-P-K and/or organic matter, for the grass seedlings to survive. You can see that at http://www.ecoseeds.com/good.example.html.
EX SITU NUTRIENTS. That "Good Example" web page shows how you can test the soil in ex situ boxes, place the soil and sow local native grass seeds, as we did in the left box in the picture. No nutrients or organic matter was added, the seeds sprouted, grew a cm. tall, and died of starvation.
Left picture, added fertilizer and one cm. organic matter on the surface, seeds sprouted, grew and were healthy.
NUTRIENT THRESHOLDS IN SOILS. Each species in a grassland has a "Soil Nutrient Seediling Survival Threshold". That means an old plant can be growing in barren soil, but if you do not see new seedlings around the plant, the soil may have had its nutrients removed below the threshold level needed by that species, for its seedlings to survive.
"SPATIAL EXTINCTION" That means that plant is entering into what I call "Spatial Extinction" in that without the ability to reproduce, at least until the soil nutrient levels are corrected, that species will go extinct on that particular spot.
Thanks for reference on barley.
On the depletion of soil P in agro-pastoral cereal-grass farming and subsequent shrub encroachment, the attached may be interesting.
Woody species are also known to produce phytotoxic substances (for a reference on beech see article above). Whether grass or wood wins will be a complex issue.
Article Nitrogen and phosphorus limited production of cereals and se...
It is common for woody species to be planted as container stock, even though there is evidence that direct seeding may be more cost-effective (see Elaine Ceccon's paper above and the one below, missed by their meta-analysis).
Even then, direct seeding is more common that drill seeding, at least for most woody species (that tend to have larger seeds).
There is considerable evidence that woody restoration in the tropics can be limited by competition with grasses, which should be controlled if possible before planting.
For exotic agressive grasses, I suggest plantings better than seeding. Choose woody species that grow fast and produce a large canopy so grasses are supressed and natural recruitment may happend below them
check:
de la Peña-Domene, M., Martínez-Garza, C., Palmas-Pérez, S., Rivas-Alonso, E., & Howe, H. F. (2014). Roles of Birds and Bats in Early Tropical-Forest Restoration. Plos One, 9(8), e104656.
Martinez-Garza, C., Bongers, F., & Poorter, L. (2013). Are functional traits good predictors of species performance in restoration plantings in tropical abandoned pastures? Forest Ecology and Management, 303, 35-45.
GRASS HAS TO GO--If it is an exotic grass you are working with, and we still do not know that from the question yet, then you will have to spray out all of that grass before you start any tree planting, and once the grass is dead, remove the dead leaves also, to remove the natural herbicides that will still be in the leaves and stems.
PLANT SEEDLINGS--Also I agree with the other writers that planting seedling trees will be much more successful than planting seeds, but also do an ex situ test in a container with the soil and some tree seedlings, and see if you need to add fertilizers to allow the trees to thrive.
CHECK SOIL NUTRIENTS--Wherever domesticated grazing animals have been, they usually steal nutrients from the soils and carry them away in their bodies, so over time you are doing a one-way nutrient mining process robbing the soils to the point that seedlings of the local native plants cannot survive. I have seen in California levels of the following nutrients stolen below the levels needed for native seedling survival:
Soil organic matter, nitrogen, very common for low phosphorus, potassium, and magnesium. For my farming project in Haiti (http://www.haitiag.org) all of those plus zero calcium, because no fertilizer has been added to that land in over 200 years.
In grazed lands worldwide, especially in the First World, nobody goes out and monitors the soil nutrients, and adds any fertilizer when the grazing animals drop the levels too low.
That might be a good study for some students in the future--can grazing animals drop soil nutrients below the level of the local native seedlings to survive, and what are those soil levels needed?
We did try distributing clay balls impregnated with native tree seeds on the surface of abandoned non-native pasture grass and found a very low success rate. We did various treatments, scarification/herbicide and control. None of the treatments had a significant effect on seedling establishment. We did see a good amount of germination from seeds but the survival was very low due to the vigorous growth rates of many seeded and mat forming grasses. We had a paired plot with planted seedlings in the same non-native grass matrix and found the survival with tree seedlings to be much higher ~75%.
Ideally if you can get rid of grasses you will likely see the greatest result with seeds or seedlings. But if it is cost prohibitive or logistically challenging to eliminate grasses plant quick growing native shrub/tree as seedlings to begin reversing the light-loving grass dominance with some shade.
Ross in NZ and Erica in Hawaii, it is not noted in the question or answers, if the grasses are exotics or local native? If exotics, they must be completely eliminated. If local native grasses, means to blend them into the project must be invented, because they are naturally an important part of the original ecosystems. For NZ and Hawaii are these exotic grasses being discussed?
Hi Ross, Mike Hands, the director of the Inga Foundation might be able to offer some advice. The Ingafoundation works with species of native Inga tree (Ingua Edulis) in Honduras as a means of adding phosphorous back in to degraded soil enabling repeated intercropping. The mulch produced by the tree stops weeds from growing. He mentioned that he had planted Inga directly into in thick, aggressive grass fields and that the trees had done very well and in a short period had suppressed the grass entirely within months.
You can get hold of Mike on: [email protected]
http://www.ingafoundation.org/
Contact Graham Fifield from Greening Australia http://www.greeningaustralia.org.au/news/staff-profile-graham-Fifield
Graham Fifield ([email protected])