The influence of hydrological regimes on sex ratios and spatial segregation of the sexes in two dioecious riparian shrub species in northern Sweden

River management practices have altered the hydrological regimes of many rivers and also altered the availability of regeneration niches for riparian species. We investigated the impact of changed hydrological regimes on the sex ratios and the Spatial Segregation of the Sexes (SSS) in the dioecious species Salix myrsinifolia Salisb.–phylicifolia L. and S. lapponum L. by studying the free-flowing Vindel River and the regulated Ume River in northern Sweden. We surveyed sex ratios of these species in 12 river reaches on the Vindel River and in 17 reaches on the Ume River. In addition, we surveyed the sex and location above mean river stage of 1,002 individuals across both river systems to investigate the SSS of both species. Cuttings were collected from male and female individuals of S. myrsinifolia–phylicifolia from both rivers and subjected to four different water table regimes in a greenhouse experiment to investigate growth response between the sexes. We found an M/F sex ratio in both river systems similar to the regional norm of 0.62 for S. myrsinifolia–phylicifolia and of 0.42 for S. lapponum. We found no evidence of SSS in either the free-flowing Vindel River or the regulated Ume River. In the greenhouse experiment, hydrological regime had a significant effect on shoot and root dry weight and on root length. Significantly higher shoot dry weights were found in females than in males and significantly different shoot and root dry weights were found between cuttings taken from the two rivers. We concluded that changed hydrological regimes are likely to alter dimensions of the regeneration niche and therefore to influence sex ratios and SSS at an early successional stage, making it difficult to find clear spatial patterns once these species reach maturity and can be sexed

Biomass yield and biomass functions for plantation grown Nauclea diderrichii in the humid tropical rainforest zone of South-Western Nigeria

Adequate management of forest plantations requires estimation of biomass yield as well as functions for estimating biomass. This paper presents biomass yield and functions for estimating total above ground biomass (TAGB), stem, branch and foliage biomass for even-aged plantations of Nauclea diderrichii (Opepe) in Nigeria. Data were obtained from 81 trees, harvested from stands of different ages. TAGB of Opepe ranged from 32.5 t ha-1 (5 years) to 287.5 t ha-1 (30 years). While 84.5% of TAGB was allocated to stem, 13.5 and 3% were allocated to branch and foliage respectively. All functions had good fits, with very high adjusted R2 (over 0.97) and very low standard error of estimate. Diameter at breast height (dbh) alone as predictive variable accounted for over 97% of the variation in biomass. Little improvement in the ability of the functions to explain variations in biomass was achieved by including total height variable in the functions. In addition, the plot of residuals showed that the functions with only dbh performed generally better than those that included height variable in their predictions. Consequently, the functions with only dbh as independent variable were recommended for use in estimating biomass of Opepe in Nigeria. Keywords: above-ground-biomass, Nauclea, indigenous species, plantation, predictive functions Ghana Journal of Forestry Vol. 15&16 2004: 30-3

Site index equation for smallholder plantations of Gmelina arborea in Leyte Province, the Philippines

The equation SiteIndex = Height × Log(IndexYear+0.5)/Log(Age+0.5) is suggested as a robust way to classify site index of small private Gmelina arborea plantations in Leyte province in the Philippines. Estimates of site index from this equation correlate well with other indicators of site productivity, including the observed mean annual volume increment and soil depth. An alternative equation based on slope and soil depth offers an indication of potential site productivity on unforested sites where no crop trees are present