Depleted soils| Impact on trees

Eric Frei · 9th April 2008, 09:58 PM

Having witnessed so many grade changes and top soil scrape offs I started to scan around the net. Just today I was on a site where the natural grade was down some 1.2m, compacted clay on top of shale. The excavator needed a rock breaker to go deeper. But this new grade will be ground level to everyone else, they'll have turf and concrete and never know better. When they plant trees they'll realise it's tough ground, and the trees will suffer. There was no top soil left on this site.

On another site they scraped it then spread a 100mm of new topsoil all over and put the turf in and few crappy little plants.

I bumped into this story. And liked it coz the ole euc is a tough customer, will live in absolute crap, however they didn't do too well here either.

Wiley InterScience :: Session Cookies

Quote:

Removal of topsoil, mainly for making bricks, is one of the main causes of soil loss around large urban centres of the Humid Pampa, Argentina. In about 7 per cent of La Plata County, the 20-40 cm thick A-horizon has been removed for that purpose. Most of the affected areas were originally prime farmland; however, with removal of the A-horizon they became unsuitable for agriculture, including grazing, since the exposed Bt-horizon is unsuited for plant growth due to its high clay content (45-65 per cent) and the low nutrient levels. Since trees survive better on poor soils than do agricultural crops, the possibility of afforestating desurfaced soils has been studied. Eucalyptus are one of the major species used in tree planting programmes aimed at reclaiming degraded soils since they are fast growing and can grow to commercial size in a wide range of soils and climatic conditions. The work reported here was done in a desurfaced Vertic Argiudoll and a similar non-desurfaced soil (control). Three Eucalyptus species were tested, i.e. E. camaldulensis, E. viminalis and E. dunnii. Their height and diameter (dbh) growth were 47.9 to 75.8 per cent less and timber volume 86.5 to 98.5 per cent less on the desurfaced soil. E. camaldulensis grew best in all the parameters in the desurfaced soil. Although tree growth was poor, afforestation may be an alternative use for desurfaced soils where agriculture and livestock breeding are not possible.

ronnyb · 11th April 2008, 11:48 PM

Around here, the first thing they do when building a new subdivision or housing project is to strip off all of the topsoil. It's piled up, run through a screener and sold off. After the house is built, maybe 1 to 2 inches of topsoil is layed over the top of the subsoil and turf is replanted. We replace alot of young trees that are maybe 2 years old that didn't survive. When we replant, we dig the hole upto 4-5x the root ball, gradually sloping upwards. The subsoil here is a very thick, alkaline clay, so we do slightly amend the backfill soil with compost. We have the best success rates with smaller diameter trees, the hard part is getting the homeowner to understand why the trees we are putting in are not 15 feet tall, but only 6 to 7 feet tall. The smaller trees acclimate to the site much better, and we find that alot of the trees that were originally planted by the landscape companies are in a hole that is only slightly bigger than the root ball, or don't have any of the wire, string, or burlap removed. Trees in this type of depleted soil are going to need additional care as they mature, we like to use compost tea, or vertical mulching and backfilling with compost made from leaves.

Quantum Leaf · 22nd April 2008, 11:04 PM

I am just wondering how much research they put into the Euc species they used. The 850 Euc. species +, are as different as chalk and cheese regarding the soil, climate requirements root systems and specific characteristics (wood density, durability, etc.). The 3 species used (E.camaldulensis, E. viminalis and E. dunnii) tend to prefer higher rainfall, and deeper, alluvial soils. Other species that would have been more suitable would have been the Euc. mallees and mallets (and the Acacia's), that is pioneering species that have deeper root systems and inherant adaptations to harsher climates and poorer soil types. After such species have become established, only then can larger tree species be employed with greater success.
It dosn,t surprise me that E.camaldulensis was the most successful of the 3 species, after all, it is the most prolific Euc. within mainland Australia. The only place it dosn,t naturally exist, is east of the Great Dividing Range.

11th April 2008, 11:48 PM	#2
ronnyb Semi-mature vigorous tree Join Date: Nov 2007 Location: Wisconsin Posts: 62	Re: Depleted soils\| Impact on trees Around here, the first thing they do when building a new subdivision or housing project is to strip off all of the topsoil. It's piled up, run through a screener and sold off. After the house is built, maybe 1 to 2 inches of topsoil is layed over the top of the subsoil and turf is replanted. We replace alot of young trees that are maybe 2 years old that didn't survive. When we replant, we dig the hole upto 4-5x the root ball, gradually sloping upwards. The subsoil here is a very thick, alkaline clay, so we do slightly amend the backfill soil with compost. We have the best success rates with smaller diameter trees, the hard part is getting the homeowner to understand why the trees we are putting in are not 15 feet tall, but only 6 to 7 feet tall. The smaller trees acclimate to the site much better, and we find that alot of the trees that were originally planted by the landscape companies are in a hole that is only slightly bigger than the root ball, or don't have any of the wire, string, or burlap removed. Trees in this type of depleted soil are going to need additional care as they mature, we like to use compost tea, or vertical mulching and backfilling with compost made from leaves.

22nd April 2008, 11:04 PM	#3
Quantum Leaf Sappling Join Date: Jun 2007 Location: Illawarra, NSW Posts: 13	Re: Depleted soils\| Impact on trees I am just wondering how much research they put into the Euc species they used. The 850 Euc. species +, are as different as chalk and cheese regarding the soil, climate requirements root systems and specific characteristics (wood density, durability, etc.). The 3 species used (E.camaldulensis, E. viminalis and E. dunnii) tend to prefer higher rainfall, and deeper, alluvial soils. Other species that would have been more suitable would have been the Euc. mallees and mallets (and the Acacia's), that is pioneering species that have deeper root systems and inherant adaptations to harsher climates and poorer soil types. After such species have become established, only then can larger tree species be employed with greater success. It dosn,t surprise me that E.camaldulensis was the most successful of the 3 species, after all, it is the most prolific Euc. within mainland Australia. The only place it dosn,t naturally exist, is east of the Great Dividing Range.

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