Na Hang Nature Reserve, Tat Ke Sector - Frontier-publications.co.uk

Na Hang Nature Reserve, Tat Ke Sector 1997
Figure 9. The five sites at which pitfall trapping was carried out.
Site Altitude Description
(m asl)
PF1 600 New clearing, bordered by existing maize field and secondary forest.
Some regrowth of herbaceous species, such as grasses and Selaginella sp.
PF2 600 Secondary forest near PF1.
PF3 400 Scrub near base camp.
Vegetation dominated by shrubs (Fabaceae) and grasses.
PF4 500 FT2. Secondary forest, dominated by Streblus tonkinensis.
(see section 5.4, above, for description)
PF5 595 FT3. Primary Forest.
PF6 695 FT1. Primary Forest.
6.3 Results
6.3.1 Sweep-netting
The numbers of species, number of individuals, α diversity and dominance, d, for
each sample are given in Figure 10.
Figure 10. Summary of sweep-net samples for four sites.
Site No. RTUs No. of α
d
Individuals
FT1 55 107 45.86 0.159
FT2 31 45 43.23 0.089
FT3 42 120 22.85 0.392
FT4 75 115 61.11 0.096
Relative abundance of insects varied greatly between the locations; the catch at FT2
was particularly small. None of the samples was large enough to allow detailed
statistical analysis, suggesting that future sweep-net sampling should involve larger
numbers of sweeps (Janzen, 1973a, used 800-sweep samples in his analysis of tropical
vegetation in Central America and the Caribbean). However, a balance must be found
between the statistical requirement for samples as large as possible, and the
difficulties of sorting large samples, especially in the field.
6.3.3 Pitfall trapping
Fisher's α and the dominance measure d were calculated for each sample, and
summary data is given in Figure 11.
Frontier-Vietnam Environment Research Report 9 22