A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
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Root Symbiosis and Nutrition<br />
in Sabah showed that increasing concentrations <strong>of</strong><br />
fertiliser resulted in increased growth rates but that<br />
growth was reduced when 2000 mg <strong>of</strong> NH 4 NO 3 was<br />
applied (Yap and Moura-Costa, in press). It will be<br />
interesting to see the final outcome <strong>of</strong> this large-scale<br />
field experiment.<br />
Lee and Lim (1989) found that foliar P concentration<br />
in naturally regenerated seedlings <strong>of</strong> Shorea curtisii and<br />
S. leprosula growing in a logged over <strong>for</strong>est site with<br />
low levels <strong>of</strong> available P (5.8 to 7.1 ppm) was significantly<br />
correlated with the extent <strong>of</strong> ectomycorrhizal infection.<br />
Lee and Alexander (1994) working with Hopea helferi<br />
and H. odorata found positive growth responses to<br />
mycorrhizal infection but variable responses to nutrient<br />
treatments. They also reported the first direct<br />
experimental evidence that ectomycorrhizal infection<br />
improved P uptake and growth <strong>of</strong> a dipterocarp species,<br />
H. odorata. Scleroderma dicstyosporum and S.<br />
columnare were reported to increase levels <strong>of</strong> nitrogen,<br />
phosphorus and potassium in seedlings <strong>of</strong> Shorea<br />
mecistopteryx (Supriyanto et al. 1993b) but these results<br />
may have been misinterpreted. Increased plant height<br />
growth, diameter and dry weight as well as uptake <strong>of</strong> Fe,<br />
Mn, Cu, Zn and Al by seedlings <strong>of</strong> Shorea compressa, S.<br />
pinanga, S. stenoptera, H. odorata and Vatica<br />
sumatrana inoculated with chopped fruit bodies <strong>of</strong><br />
Russula sp., Scleroderma sp. and Boletus sp. have been<br />
reported in Indonesia (Santoso 1989, Santoso et al.<br />
1989). However, it is not clear whether ectomycorrhizas<br />
were <strong>for</strong>med by the test fungi or by contaminants.<br />
In a study <strong>of</strong> site characteristics and distribution <strong>of</strong><br />
tree species in mixed dipterocarp <strong>for</strong>ests in Sarawak,<br />
Baillie and co-workers (1987) considered phosphorus<br />
the most critical nutrient while magnesium was thought<br />
to be important because <strong>of</strong> possible effects on the<br />
efficiency <strong>of</strong> the dipterocarp mycorrhizal root systems.<br />
Some species <strong>of</strong> <strong>dipterocarps</strong>, e.g. Shorea parvifolia<br />
were consistently associated with sites <strong>of</strong> high P status<br />
while others like S. quadrinervis were associated with<br />
sites <strong>of</strong> low P status. Amir and Miller (1990) found<br />
potassium to be the primary limiting nutrient in two<br />
separate <strong>for</strong>est reserves in Peninsular Malaysia. Burslem<br />
et al. (1994), however, are <strong>of</strong> the opinion that any <strong>of</strong> the<br />
macronutrients and micronutrients can become<br />
potentially limiting to plant growth when the primary<br />
limitation by P is overcome. From a study <strong>of</strong> soils under<br />
mixed dipterocarp <strong>for</strong>est in Brunei, Takahashi et al.<br />
(1994) stated that logged over <strong>for</strong>ests are suitable <strong>for</strong><br />
106<br />
enrichment planting with <strong>dipterocarps</strong> since loss <strong>of</strong> soil<br />
nutrients and degradation <strong>of</strong> nutrient status would be small<br />
because <strong>of</strong> nutrient accumulation in the deeper horizons.<br />
It is known that different tree species have differing<br />
site requirements reflecting their differing abilities to<br />
take up nutrients from intractable soil sources due to<br />
differences in root system architecture and in the<br />
particular differences in the mycorrhizal relationships<br />
between species (Miller 1991). Yasman (1995) found<br />
that light demanding Shorea leprosula seedlings could<br />
<strong>for</strong>m many more ectomycorrhizal types than shade<br />
tolerant Dipterocarpus confertus seedlings. Mineral<br />
nutrition, plant light requirements and mycorrhizal<br />
infection are very intimately related but it is only recently<br />
that the importance <strong>of</strong> this relationship has begun to<br />
receive recognition. Newton and Pigott (1991a) working<br />
with oak and birch found that application <strong>of</strong> fertilisers<br />
could reduce the number <strong>of</strong> mycorrhizal types and their<br />
relative abundances. Lee and Alexander (1994) found that<br />
full nutrient application prevented ectomycorrhizal<br />
<strong>for</strong>mation in Hopea odorata but not in H. helferi. This<br />
may indirectly affect the drought tolerance <strong>of</strong> the host<br />
plants and consequently have implications on <strong>for</strong>est<br />
management. Burslem et al. (1994) suggested that<br />
mycorrhizas play an important role in enabling<br />
Melastoma to grow on very nutrient poor soils despite<br />
being highly nutrient demanding. They suggested that <strong>for</strong><br />
mycorrhizal plants, limitation by the major cations may<br />
prove more significant than limitation by P. In a more<br />
recent study, Burslem et al. (1995) suggest that shade<br />
tolerant seedlings <strong>of</strong> lowland tropical <strong>for</strong>est which<br />
possess mycorrhizas are not limited by P supply because<br />
the mycorrhizas effectively relieve them <strong>of</strong> P limitation<br />
and/or because such plants have a low demand <strong>for</strong><br />
nutrients <strong>for</strong> growth at low irradiance.<br />
It is clear that there is an urgent need <strong>for</strong> more<br />
integrated studies on dipterocarp mineral nutrient<br />
requirements and that such studies must take into<br />
consideration the role <strong>of</strong> the dipterocarp mycorrhizal<br />
association and the effect <strong>of</strong> different light regimes.<br />
While such studies are more easily conducted in the<br />
nursery with potted plants, there is also a need to test<br />
the conclusions <strong>of</strong> such experiments in the field.<br />
<strong>Research</strong> Priorities<br />
The need <strong>for</strong> more research into the dipterocarp<br />
mycorrhizal association is already well recognised and