permaculture

[Nathan Czuba <nathanaczuba@yahoo.com>]

So I was reading through a few ecology papers and found things that you all 
might find interesting/useful.

"Whereas native sassafras-persimmon stands are generally invaded by oaks, 
pines are usually invaded both by old-field species such as sassafras and by 
later successional oaks.  In contrast, planted stands of black locust 
(Robinia pseudoacacia) tend to be invaded by elm (Ulmus americana), black 
cherry (Prunus serotina), box elder (Acer negundo), hackberry (Celtis 
occidentalis) and other mesic forest species (Ashby 1964).

As reported by Carmean et al. (1976), "height growth at 16 years of planted 
black walnut (Julgans nigra), sweetgum (Liquidambar styraciflua) and tulip 
tree was greatest on the part of the field clearcut from a black locust 
plantation, and least on the portion occupied by broomsedge (Andropogon 
virginicus), poverty grass (Danthonia spicata and goldenrod (Solidage spp.) 
at the time of planting.  Heights were intermediate and approximately equal 
on plots clearcut from a shortleaf pine plantation and on a portion of the 
field fully stocked with sassafras, persimmon and elm.  Planted red oak 
(Quercus rubra) grew best on plots clearcut from black locust and shortleaf 
pine, relatively poorly on the formerly fully stocked area, and, like the 
black walnut, did not live past ten years on the non-stocked, herbaceous area 
of the field.  These growth results were related to foliar nitrogen levels, 
noncapillary soil pore volume, bulk density, and organic matter content, and 
to
 mycorrhizal and phosphorus fertilization studies carried out in pots.  
Allelopathic compounds produced by broomsedge and sassafras were as 
considered to have influenced the growth results."

An "interesting process is the tendency of certain species to 'pump' cations, 
or move them from lower soil horizons to the soil surface."  A study by Alban 
(1982) contrasted "the effect of aspen (Populus spp.) and white spruce (Picea 
glauca) with red pine (Pinus resinosa) and jack pine (P. banksiana) on the 
distribution of cations and pH in the soil.  These four species were planted 
simultaneously on two different sites in northern Minnesota.  After about 40 
years of growth, both the spruce and the aspen stands have experienced a 
large removal of cations from the lower soil horizons.  These have been 
incorporated into the forest floor and biomass material.  The effect of this 
has been to create a nearly neutral forest floor at the expense of acidifying 
the lower horizons.  The pines have had the opposite effect: the forest floor 
has been acidified by biological activity, while the lower horizons maintain 
the high initial pH.  If restoration plans called for the
 establishment of species requiring neutral surface soils, the use of cation 
pump species might be a more effect way of achieving and maintaining this 
condition than single or continuous application of lime."

Alban, D. H. 1982, Effects of nutrient accumulation by aspen, spruce and pine 
on soil properties, Soil Science Society of America Journal, 46, 853-861

Ashby, W. C. 1964, Vegetation development on a strip-mined area in southern 
Illinois. Transactions of the Illinois State Academy of Science, 57, 78-83

Carmean, W. H., et al. 1976, Hardwoods Planted in Old Fields Favored by Prior 
Tree Cover. USDA Forest Service Research Paper NC-134

       
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