|dc.description.abstract||This study has two principal aims; firstly to investigate the effect of topography and in particular erosion as a soil-forming factor and secondly to investigate the reasons for the existence of Pinus radiata
showing symptoms of nutrient deficiency in Nelson.
Hans Jenny in his book "Factors of Soil Formation", wrote
"Topography as a soil-forming factor has not received the attention
it deserves. It is true, of course, that a considerable amount of
information on runoff and erosion in relation to slope is at hand,
but it deals primarily with the removal and destruction of soil and
not with soil formation."
This statement, made nearly 30 years ago, is still true. One method
of assessing the importance of topography as a soil-forming factor is the
recognition and investigation of a Toposequence wherein the remaining four
soil-forming factors are kept constant or ineffectively varying. Observed
differences between the soils of the sequence are then considered to be
the result of differences in topography since the initial point of soil
development. One such sequence had been identified in 1964 by Mr.E.J.B.
Cutler of the Soil Science Department, Lincoln College on strongly weathered
granite at Kaiteriteri. In addition, another was postulated within the
Mapua hill soils developed on the seaward end of the Moutere gravels, an
area of very old, very strongly weathered and leached alluvial greywacke
gravels in Nelson. Associated with both these postulated sequences was
Pinus radiata showing nutrient deficiencies and consequent variations in
This study is probably the first to thoroughly investigate
differences in soil development attributable to the down-cutting effects
of erosion exposing fresh parent material for soil development. Each
erosion cycle has provided a new groundsurface for profile formation and,
taken together, the various groundsurfaces identified provide a soil
sequence where the gains, losses, transformations and redistribution of
many organic and inorganic parameters are attributable to the effects of
relief in general and erosion specifically.
The strong weathering and leaching undergone by even the youngest
groundsurface in both sequences means that the stage of soil development
encompassed in this study is considerably more advanced than in most other
sequence studies. These have tended to concentrate on the rate of build-up
of organic matter and associated fractions in relatively young soils. One
exception is the study by P.R. Stevens of a chronosequence of soils near the
Franz Josef glacier in Westland, which covers a range of soil development
from zero time to a strongly podzolised profile. The present study includes
stages of soil development even more advanced than those in Stevens' work.
The second part of the study is part of a widespread research programme
being carried out by members of the New Zealand Forest Research
Institute and Lincoln College into the underlying causes of a possible
decline in productivity on the poorest sites in Nelson, following felling
of the first crop of Pinus radiata. If this fall-off in productivity is
indicative of a future general decline in other areas of low fertility the
implications for the expanding New Zealand forestry industry would be
quite serious. For this reason, considerable effort has been and is being
expended to investigate the problem in Nelson. Recent work by Dr. H.
Holstener-Jorgensen in the area has shown that the postulated productivity decline in the area may be a result of different establishment practices
between the two crops rather than an irreversible decline. Consequently
the present study has tended to concentrate on the causes of the undoubted
growth differences present within the regeneration crop. A combination
of methods was used to investigate this problem as well as the causes of
similar nutrient deficiencies in young planted Pinus radiata growing on
areas of the Kaiteriteri granite soils.
The thesis follows the traditional form with an extensive review of
literature covering previous studies of topo - and catenary sequences with
a section devoted to the influence of relief as a soil-forming factor and the
evolution of landscapes, particularly hillslopes. Field work and analytical
procedures are covered in the section on materials and methods which
is followed by the presentation of results and ensuing discussion.
Literature references, Tables, Figures, Plates and Appendices are bound in
a separate volume.
It is relevant to comment upon the value of such a study. The
identification and study of monofunctional soil sequences is a prerequisite
to the understanding of the processes of soil formation. All sequence
studies suffer from the assumption that it is possible to say definitely
that all other factors of soil formation have remained constant during the
development of the soils concerned. However, this does not diminish the
usefulness of the physical, chemical and mineralogical information which
can be gained from the study of such sequences. The information concerning
these soils and the foliage data obtained should prove valuable in helping
to elucidate the problems of forestry management which have and will
undoubtedly continue to appear in future years in the Nelson province.||en