Model performance of tree height-diameter relationships in the central Congo Basin

Key message

Tree heights in the central Congo Basin are overestimated using best-available height-diameter models. These errors are propagated into the estimation of aboveground biomass and canopy height, causing significant bias when used for calibration of remote sensing products in this region.

Context

Tree height-diameter models are important components of estimating aboveground biomass (AGB) and calibrating remote sensing products in tropical forests.

Aims

For a data-poor area of the central Congo Basin, we quantified height-diameter model performance of local, regional and pan-tropical models for their use in estimating AGB and canopy height.

Methods

At three old-growth forest sites, we assessed the bias introduced in height estimation by regional and pan-tropical height-diameter models. We developed an optimal local model with site-level randomizations accounted for by using a mixed-effects modeling approach. We quantified the error propagation of modeled heights for estimating AGB and canopy height.

Results

Regional and pan-tropical height-diameter models produced a significant overestimation in tree height, propagating into significant overestimations of AGB and Lorey’s height. The pan-tropical model accounting for climatic drivers performed better than the regional models. We present a local height-diameter model which produced nonsignificant errors for AGB and canopy height estimations at our study area.

Conclusion

The application of general models at our study area introduced bias in tree height estimations and the derived stand-level variables. Improved delimitation of regions in tropical Africa with similar forest structure is needed to produce models fit for calibrating remote sensing products.

     

Altitude,tree species and soil type are the main factors influencing the severity of <Emphasis Type="Italic">Phaeoramularia</Emphasis> leaf and fruit spot disease of citrus in the humid zones of Cameroon

In Cameroon and most countries of tropical Africa where Phaeoramularia leaf and fruit spot disease of citrus is reported, a total yield loss of 50–100% is common. For effective control of this disease, it is imperative to understand how it originates, and which factors contribute to its development. To this end, the environmental and biological characteristics of each tree from 39 sites located in 13 citrus production basins in the humid zones of Cameroon were collected by means of a survey. Information was collected by interviewing heads of households, and by visual inspection of trees and their environment. The independent variable was severity of the disease while the dependent variables were environmental and biological characteristics. Climatic characteristics varied from one basin to another. The 13 citrus production basins were regrouped in five categories based on disease severity. Altitude, tree species and soil type were the main factors influencing the disease severity. Thus the higher is the altitude, the more important is the disease severity. Also, disease severity increased with increasing number of grape fruit, orange and pummelo trees. However, disease severity was lower on trees growing on volcanic soils as compared with the other soil types. Further analysis of these factors could lead to the development of a risk assessment model for Phaeoramularia leaf and fruit spot of citrus.     

Productive performance and carcass yield of egg type male chickens raised with outdoor access in the tropics

This study aimed to compare growth and slaughter performance of layer-type slow-growing Rhode Island Red male chickens grown with and without access to an area with vegetation in the tropics. Raised until 115 days of age, a total of 156, 1-day-old birds were randomly allocated to two treatments: total confinement (TC) and partial confinement (PC), with 6 replicates of 13 birds each. Birds grown under TC conditions reached a live weight of 2016.68 g while those raised with access to outdoors attained 1981.07 g, without statistical differences. Feed intake and daily feed intake were higher (P < 0.05) in birds farmed with TC management, during the last 17 days of the trial. Treatments did not significantly (P > 0.05) affect bird’s other productive parameters and carcass traits. Results from this study suggested that slow-growing Rhode Island Red males may be raised with access to outdoors without any adverse effect on productive performance and carcass quality in the Mexican Tropic. Based on the results of this study, a rearing period of 84 days of age is recommended for Rhode Island Red male chickens raised in both TC and PC production systems.

     

Relationship between haptoglobin, serum amyloid A, and clinical status in a survey of dairy herds during a 6-month period

BACKGROUND: Haptoglobin and serum amyloid A are major acute phase proteins in cattle. Dairy cattle often develop pathologic conditions in the peripartum period; acute phase proteins may be useful in their diagnosis. OBJECTIVES: The purpose of this study was to compare the accuracy of serum haptoglobin (Hp) and serum amyloid A (SAA) concentrations with clinical health status for diagnosing disease during the peripartum period in dairy cattle. METHODS: Dairy cows from 4 herds were evaluated every 15 days over a 6-month period. Health status was determined by thorough clinical examination. Haptoglobin and SAA concentrations were measured in serum using validated methods and the results were classified as positive or negative based on defined cutoff points. Disease prevalence, sensitivity, and specificity were compared using clinical examination as the gold standard. RESULTS: A total of 1896 samples from 158 cows were analyzed. Significant increases in mean Hp and SAA concentrations were observed in the week following parturition in both primiparous and multiparous cows, although high interindividual variability was observed. Both Hp and SAA had low sensitivity but higher specificity in determining disease status compared with clinical examination. Increased concentrations of Hp and SAA were found in <10% of samples from clinically healthy cows, except in the week after parturition. CONCLUSIONS: Haptoglobin and serum amyloid A should be used with caution as markers of inflammation in the week after calving. Poor sensitivity in other postpartum periods could be related to the higher incidence of chronic (vs acute) inflammation. Haptoglobin may be appropriate for routine screening, but further work needs to be done to assess its value as an indicator of herd health.     

Tip20p prohibits back-fusion of COPII vesicles with the endoplasmic reticulum

Directionality in intracellular trafficking is essential to ensure the correct localization of proteins along the secretory pathway. Here, we found evidence for an active mechanism that prohibited back-fusion of de novo-generated vesicles with their donor compartment. Tip20p is a peripheral membrane protein implicated in consumption of COPI vesicles at the endoplasmic reticulum. However, a specific mutant of TIP20 did not interfere with COPII vesicle generation but allowed these vesicles to fuse back to the endoplasmic reticulum, a process that does not occur normally in the cell.