Culm characteristics and volume-weight relationship of a forest bamboo(Melocanna baccifera(Roxb.) Kurz) from northeast India

Culm characteristics of Melocanna baccifera, locally ＇muli＇, culms at five different culm ages of 11 girth classes （5-6 to 15-16 cm） were studied from Cachar Dis- trict of southern Assam, northeast India. We recorded internode length, internode diameter, number of internodes per culm, total culm height, total culm green weight and total culm volume of all five culm age classes. Data were gathered on 165 culms, each culm age class containing 33 culms with 3 culms per girth class. Culm height ranged from 3.2 to 15.3 m with highest mean of 9.15 m （in threeyear old culms） and maximum culm height was recorded in four-year old culms. Highest mean and maximum internode length （27.45 and 54.2 cm, respectively）, internode diameter （3.12 and 4.75 cm, respectively） and total culm green weight （5.42 and 12.87 kg/culm, respectively） were recorded in three-year old culms and lowest in current-year culms. Best fitted regression models for all parameters were developed. Significant linear relationships between culm green weight and culm solid volume were documented for all five culm age classes. Their corresponding best-fit regression models were also developed.

Population status and regeneration of a tropical clumping bamboo Schizostachyum dullooa under two management regimes

Schizostachyum dullooa （Gamble） Majumder ＇dolu bamboo＇ is a thin walled sympodial moderate sized to large tufted bamboo, dominant in the successional fallows of northeast India. The impact of resource management on productivity and sustainability of the species was evaluated by investigating the population status and regeneration in Cachar tropical semi evergreen forest under private property resource management （PPRM） and common property resource management （CPRM） regimes. Population status revealed current-year, one-year, two-year and three-year-old culms contribute 54%, 24%, 16% and 6% of the total culms per clump, respectively, under PPRM. Three-year-old culms were absent in CPRM and population status was thus represented by current year （83%）, one-year （16%） and two-year （1%） old culms. Net change, rate of change and % gain in population for different age classes showed the prevalence of management practices under CPRM was unscientific. Efficiency of new culm production per clump used as an index of regeneration was 69.7% in PPRM and 59.88% in CPRM. New culms produced under CPRM were small and thin. We conclude that CPRM is inappropriate for a long term economic and ecological sustainability of the species and alternative management protocols are needed for conservation of the species.

Development and evaluation of robust tree biomass equations for rubber tree (Hevea brasiliensis) plantations in India

Background： In India, rubber（Hevea brasiliensis） plantations cover -0.8 million ha of land, emphasizing its significant role in the Earth＇s carbon dynamics. Therefore, it is important to estimate the biomass stocks of plantations precisely in the context of carbon management. Previous studies in India have focused on development of allometric equations for estimating aboveground biomass（AGB） through harvesting younger trees（up to 14 yr）only or on studies with small sample sizes without assessing model bias. The objective of this study was to develop biomass estimation models for different tree components in rubber plantations and assess model predictive performance at the stand level.Methods： A total of 67 trees were harvested from plantations of different ages（6, 15, 27 and 34 yr） in North East India and their diameter at 200 cm（D）, height and dry weights of different tree components were recorded. The data were used for evaluation of H-D and biomass estimation models at the stand level.Results： The Michaelis-Menten function was found to be the most appropriate model for estimating tree height among 10 commonly used H-D models. For estimation of AGB and coarse root biomass, a model that involves tree volume（i.e. D2 H） was found to provide better prediction than either D or H alone or a model that combines H, D and stand density. The estimated AGB varied from 28 Mg·ha-（-1） in 6 yr. old plantation to 169 Mg·ha-（-1） in 34 yr. old plantations.The coarse root biomass was estimated at 4 Mg·ha-（-1） for 6 yr. old plantation and 12 Mg·ha-（-1） for 34 yr. old stands.Conclusions： It is concluded that models involving tree volume are more appropriate for regional level biomass estimation than simple power-law models for individual stands. We recommend that the power-law model should not be used for estimation of AGB in plantations at different growth stages because power-law parameters can be biased due to data truncation.