Type E: Parashorea malaanonan / Dryobalanops Forest

 

The following is an excerpt of JED Fox's PhD thesis. The article stays fairly true to the original with minor changes. Most measurements are changed to the Metric System.

Quick Jump    Silabukan    Semporna/Tawau    Elsewhere    Words of wisdom

 

Forests in Silabukan FR*

This Type is primarily found on steeper slopes than the others described thus far and may be considered as marginal between lowland and the hill dipterocarp types which follow (i.e. Types F and G). In eastern Sabah, this Type is present in Silabukan  FR on mixed volcanic and sedimentary soils where S. johorensis and Eusideroxylon zwageri  are common associates, and presence of these is one of the main distinctions between Types A and E in this area. A relascope survey in Block 42 near Pangaruwon River in Silabukan FR sampling 70 acres (28 ha)  indicates more large trees than similar surveys in Type A stands in the vicinity.

 

Stocking data (commercial species only) from six 1 ha plots in the area felled in 1969 (RP 245/3) in the Bagahak Range area of Silabukan FR showed that Eusideroxylon was absent in this rather hilly area. Of particular note are absence of Dipterocarpus species other than D. caudiferus, predominance of S. johorensis of the Rubroshorea, absence of Selangan Batu  (though Type F is locally represented by S. laevis within the reserve), and abundance of Richetia mainly S. hopeifolia and S. faguetiana.

 

This area had representation of smaller trees 15 ft girth (1057 cm diameter) of commercial species totaling 19.7/acre (48.6/ha) with 27% Richetia, 22 % S. johorensis, 13% P. malaanonan and 10% Dr. lanceolata. As with other Parashorea forests, the canopy was irregular and distribution of large trees patchy but with sizes well over 16 ft girth (166 cm diameter). Of the non-dipterocarps present, Sympetalandra borneensis was particularly abundant, species of Annonaceae in the understorey.

 

*Note: In the early 1970s, Silabukan FR was to a very large area in the Dent Peninsula. It is similar to the present areas covering the eastern half of Tabin Wildlife Reserve and the area southwards to the Lahad Datu--Tungku main road.

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Forests of the Semporna/Tawau Peninsula

S. johorensis is common in parts of Kalumpang FR north of Type D, on the Kalumpang Formation and is also abundant on remaining basalt in the Quoin area and on andesite, dacite etc. in the Tawau Hills FR with the two type species. Nicholson (in Paton 1959) reported the same form of forest on Kawa soils developed on intrusive doleritic rock. Locally very large trees were found in the Quoin area {e.g. a S. superba SB of 32 ft girth (310 cm diam)} at 5 m from the ground with total height of 76 , but relatively short boles were attributed to the lack of a competing main storey; blanks with climber tangles were frequent throughout the area of basalt soils. Mean values for 11 half-acre plots on basalt soils showed total numbers over 1 ft g (10 cm diam) as 145/acre, with basal area of 170 sq. ft/acre of which 31 were dipterocarps and 3.4/acre over 8 ft g of which 6.5 were dipterocarps.  Dipterocarpus was absent, except as small trees. Recent plots established across Quoin (0.45 ha) and Bald Hills (0.28 ha), both basalt, showed that other dipterocarp species present in these areas but not included in the samples were S. macroptera Ru, S. superba SB, Parashorea smythiesii, Hopea beccariana and Dipterocarpus applanatus, the latter as a small tree only.

 

Tawau Hills FR has long been considered an area of hill protection forest on highly erodable dacite and andesite hills from 170300 m altitude. They contained variable stands in alluvial valleys, on steep slopes and high crests. The latter higher up and outside felling areas were not sampled but contained forests of Type F

 

The P. malaanonan/Dr. lanceolata Type is represented at lower levels in the mountainous Gunong Rara FR Plots placed at Miles 3941 along Luasong/Gunong Rara Road reveal the absence of Eusideroxylon, scarcity of certain Rubroshorea species, e.g. S. leprosula and S. ovalis, scarcity of  Dipterocarpus species, increased frequency of Dr. lanceolata, compared with the Luasong area and high representation of Parashorea. S. pauciflora, in addition to the other 2 Rubroshorea , is comparatively abundant Affinities of the forest in this area clearly lie with Type B to the north in Kuamut FR and to Type C nearer the coast in Kalabakan FR. Limited occurrence of the Type E assemblage of species is known for shale ridges in the higher hills of Gunong Rara, but its full extent is not present known.

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The forests elsewhere

The Type also occurs on the basalt mountains in the Labuk valley area of central where Meijer (1968) noted high incidence of Pinorea longiracemosa and Diospyros species. The same forest probably occurs on the isolated grandiorite peaks northeast of Ranau in the headwaters of the Sugut River near Paginatan. Relic gallery forest containing S. acuminatissima (Ri), E. zwageri and P. malaanonan in the Sook Plains suggests that this type was formerly present in the area on present day grassland areas of non-podsol soils. Further west the forests in Mandalom FR is partly of this type and partly of Type F Selangan Batu Forest. Here Type E is represented by P. malaanonan and S. acuminatissima on the lower slopes petering out at above 600 m altitude.

 

At Pangie on the lower slope of hills in the Gunung Lumaku FR where Tamburong Formation extends into the Crocker Range, RP 15 is representative of the P. malaanonan/Dr. lanceolata Type. In this area it again gives way to Type F on the steeper higher slopes.  

 

Elsewhere in the Crocker Range, this type has been largely eliminated (as with Type D) by shifting cultivation, though it still present inside, and adjacent to Mt. Templar FR. Here Richetia is represented by S. faguetiana and S. kudatensis;  S. leptoclados is uncommon and Rubroshorea is represented by S. ferruginea and S. smithiana; and both the type species are abundant. Small patches remain in the Sir James Brook Range at the northern extremity of the Crocker Range, on the lower slopes of Timbang Batu Hills to the southeast of Marudu Bay, and in Labuan FR near Kudat. Dipterocarpus warburgii is present in this forest Type in both Gunong Lumaku between Tenom and Tomani.

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Words of wisdom

At present the only important area of commercial managed forest of Type E is that in Silabukan FR as the type generally occurs on steeper slopes exploitation is both difficult and potentially more likely to lead to severe erosion than with Types B and C. However the principal species components are important in regeneration considerations where P. malaanonan, S. johorensis or Dr. lanceolata are abundant within the main commercial forests.

 

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