Predicting of biomass in Brazilian tropical dry forest: a statistical evaluation of generic equations

ABSTRACT Dry tropical forests are a key component in the global carbon cycle and their biomass estimates depend almost exclusively of fitted equations for multi-species or individual species data. Therefore, a systematic evaluation of statistical models through validation of estimates of aboveground biomass stocks is justifiable. In this study was analyzed the capacity of generic and specific equations obtained from different locations in Mexico and Brazil, to estimate aboveground biomass at multi-species levels and for four different species. Generic equations developed in Mexico and Brazil performed better in estimating tree biomass for multi-species data. For Poincianella bracteosa and Mimosa ophthalmocentra, only the Sampaio and Silva (2005) generic equation was the most recommended. These equations indicate lower tendency and lower bias, and biomass estimates for these equations are similar. For the species Mimosa tenuiflora, Aspidosperma pyrifolium and for the genus Croton the specific regional equations are more recommended, although the generic equation of Sampaio and Silva (2005) is not discarded for biomass estimates. Models considering gender, families, successional groups, climatic variables and wood specific gravity should be adjusted, tested and the resulting equations should be validated at both local and regional levels as well as on the scales of tropics with dry forest dominance

Variations in forest aboveground biomass in Miyun Reservoir of Beijing over the past two decades

Purpose: In recent years, climate change, particularly rising carbon dioxide (CO2) concentration and global warming, has attracted much attention around the world. Forest ecosystems still play a crucial role in global carbon (C) fixation. Quantifying forest aboveground biomass (AGB) and its temporal variations is essential for understanding external impacts (e.g., urbanization, environmental change) as well as assessing the potential of forest ecosystems assimilating the atmospheric CO2. Materials and methods: In this study, we established regression models for AGB estimation in the Miyun Reservoir region, based on relationships between Landsat-derived variables and ground truth AGB values, which were obtained from both plot measurements and estimations using Light Detection and Ranging (LiDAR) dataset. The models were applied to calibrated Landsat images acquired in 1990, 2000, and 2010 to track the forest AGB temporal variations and the corresponding spatial distributions for each period. The AGB estimations using LiDAR showed high consistency with values based on the plot measurements, while the established models presented an acceptable accuracy. Results and discussion: The AGB density in the Miyun Reservoir experienced an overall increase since 1990 and was averaged at 52.20 and 32.12 t ha−1, for stand forest and shrub in 2010, respectively. Total AGB in 2010 was estimated to be 4.5 × 107 t, which increased by 8% when compared with the level in 1990. Our results are in the similar range of AGB density reported by other studies carried out in Northern China. Ecological programs including Three-North Shelter Forest Project and Returning Farming to Forest promoted the forest expansion and development during this period, while local farming activities exerted certain negative effects on the surrounding forest systems. Conclusions: Absolute AGB density values indicated that regions with less external interventions present more consistent biomass accumulation. However, the coarse spatial resolution and 10-year interval of the datasets limited detailed analysis of impacts from urbanization of Beijing City. Future studies incorporating sophisticated ecosystem research methods are expected to uncover the mechanisms and key drivers for the observed variations in the AGB in the Miyun Reservoir region of Beijing, China.Griffith Sciences, School of Natural SciencesNo Full Tex

Beliefs that Condoms Reduce Sexual Pleasure—Gender Differences in Correlates Among Heterosexual HIV-Positive Injection Drug Users (IDUs)

Studies consistently find that negative condom beliefs or attitudes are significantly associated with less condom use in various populations, including HIV-positive injection drug users (IDUs). As part of efforts to reduce sexual risk among HIV-positive IDUs, one of the goals of HIV interventions should be the promotion of positive condom beliefs. In this paper we sought to identify the correlates of negative condom beliefs and examined whether such correlates varied by gender, using a subsample (those with an opposite-sex main partner; n = 348) of baseline data collected as part of a randomized controlled study of HIV-positive IDUs. In multivariate analyses, we found more significant correlates for women than for men. With men, perception that their sex partner is not supportive of condom use (negative partner norm) was the only significant correlate (Beta = −0.30; p < 0.01; R2 = 0.18). Among women, negative partner norm (Beta = −0.18; p < 0.05); having less knowledge about HIV, STD, and hepatitis (Beta = −0.16; p < 0.05); lower self-efficacy for using a condom (Beta = −0.40; p < 0.01); and more episodes of partner violence (Beta = 0.15; p < 0.05) were significantly associated with negative condom beliefs (R2 = 0.36). These findings suggest important gender-specific factors to consider in interventions that seek to promote positive condom beliefs among HIV-positive IDUs