SYNOPSISTree volume and biomass equations developed for Kitulangalo area in Morogoro, Tanzania ignored small branches and small trees. Consequently, this study was carried out to develop new individual tree volume and biomass equations, and assess current regeneration status, biodiversity and yield ofmiombo woodlands of the area. Volume and biomass equations based on stump diameter for the estimation of volume and biomass of felled trees were also developed. A total of 30 trees were measured for stump diameter (StD), diameter at breast height (dbh) and total height and felled for the determination of volume and biomass. Different tree stem, branch and total volume and biomass models were then fitted.For the determination of current regeneration status, biodiversity and yield, data were collected from three strata: (a) Forest Reserve managed by the Central Government, (b) Forest Reserve under Sokoine University of Agriculture (SUA) and (c) General land (free access by the public). In each stratum, temporary concentric circular sample plots were laid out on transects at 150 m intervals for a 1% sampling intensity. Stand variables such as number of stems per ha, basal area, biomass, volume and plant diversity, were computed for each stratum. The study has revealed the presence of average volumes (m 3 ha· 1 ) and basal areas (m 2 ha· 1 ) of: 76.02 ± 9.14 and 9.13 ± 0.78 for the Government forest reserve, 76.03 ± 9.34 and 8.95 ± 0.73 for SUA forest reserve, and 43.9 ± 7.75 and 7.78 ± 1.1 for general land forest. The respective biomass values were 43.56 ± 7.06, 41.40 ± 4.90 and 29.31 ± 6.56 t ha· 1 • Tree species composition and regeneration status revealed that though disturbed, the public land species composition is not different from the other two strata. More studies should be done on the nursing ofthe abundant regeneration in the disturbed general land. The developed volume and biomass models are recommended to be used for the miombo woodlands at Kitulangalo area especially where small trees ( < 8 em dbh) are involved.

Frequent nutrient removals accompanying wood and crop harvests from rotational woodlot systems may contribute to declining site productivity and sustainability because of soil nutrient depletion. However, selecting for nutrient-efficient tree species may well sustain productivity under this system. To test this hypothesis, a randomized complete block experiment was adopted to assess effects of five tree species on soil nutrients status, nutrient use efficiency and wood yield in semi-arid Tanzania. After 5 years rotation, top soils under Gliricidia sepium (Jaqua), Acacia polyacantha Willd. and Acacia mangium Willd. were the most fertile with soil organic carbon and exchangeable cation status raised close to those in natural Miombo systems. Soil inorganic N and extractable P levels reached sufficiency levels for subsequent maize culture. Wood productivity in tree fallows averaged three times higher than that of Miombo woodlands indicating the high potential of the woodlot system to supply fuelwood, and consequently relieve harvesting pressures on the natural forests. Acacia crassicarpa A. Cunn. ex Benth. produced the most wood (51 Mg ha À1 ) at low nutrient ''costs'' presumably due to high nutrient use efficiency. Wood yield of this species was 42 and 120% greater than that of A. polyacantha and A. nilotica, respectively, but contained comparatively less nutrients (42-60% less for P, K, and Ca). Gliricidia sepium and A. polyacantha returned the largest amount of nutrients through slash at harvests. Of all test species, A. crassicarpa exhibited the most promise to sustain wood production under rotational woodlot systems due to relatively high productivity and low nutrient export at harvest.

A drainage and fertilization experiment was established in 1989 in a tamarack (Larixlaricina (Du Roi) K. Koch) and black spruce (Piceamariana (Mill.) B.S.P.) mixed natural stand growing on a minerotrophic peatland. The drained site was ditched in fall 1987. Fertilization treatments of N–P–K at 0:0:0, 0:80:120, 200:80:120, and 400:80:120 kg•ha−1 (N as urea) were applied in late May 1989 Tamarack short-shoot needles and black spruce current-year needles, sampled on 31 August 1989 and 2 September 1990, were analysed for unit needle mass and N, P, and K. Drainage without fertilization increased foliar N, P, and K concentration of tamarack and black spruce, with larger responses occurring in tamarack. However, drainage decreased needle mass of unfertilized black spruce, although net assimilation rate increased, suggesting that an increased proportion of photosynthate was allocated to root development. Needle mass of tamarack was not affected in 1989 but was increased in 1990 by drainage, indicating different acclimation mechanisms to drainage by the two species. Responses in unit needle mass and foliar N and P concentration of both species to P–K alone, and (or) N–P–K fertilization, were higher on the drained than on the undrained site. Increased availability and uptake of N and P with a lowered water table were a likely consequence of increased near-surface soil temperature, improved soil water–soil aeration relations, and accelerated N and P mineralization and uptake rates. Foliar N, P, and K of tamarack were more responsive to fertilization than those of black spruce. N–P–K elevated foliar N concentrations of tamarack and black spruce and resulted in concomitant increases in needle mass, suggesting that N was limiting both species. Addition of P–K alone increased foliar P concentration and foliar mass of tamarack, indicating a P limitation to tamarack growth.

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