Research Items (19)
Although it is commonly assumed that biomass allometric models are site specific, evaluations of site-effects are rarely undertaken. In this paper we develop biomass-allometric models to determine site influences. This study is based on data from 240 Norway spruce trees (Picea abies (L.) Karst.), growing in 24 early-growth plantations. A multilevel modelling approach was adopted and intraclass correlation was used to evaluate site effects. Results indicated that biomass allometric models were highly specific to sites and that, depending on the biomass component and the type of predictor adopted, some 33% and 86% of overall model variance could be attributed to forest stand effects. The remaining variance was attributable within stand variability. Stem biomass was the most site-specific biomass component whereas branch biomass was the least influenced by site effects. Diameter at collar height (D) was less site-specific than height (H) in predicting biomass. Using D and H within the same model as distinct predictors, although improving the model fit, increased the model site-specificity. However, when D and H were combined in one predictor expression (i.e. D2H), this reduced model site specificity, despite requiring fewer parameters than other models. This also compensated for undesirable collinearity effects amongst predictor variables. Furthermore, for the sampled diameter range, the site-specificity was mainly driven by biomass allocation pattern (to branches, needles and roots). The considerable between site variability of allometric relationships suggests that consideration of stand effects is essential for the robust prediction of biomass.
In this paper, we report an investigation of how forest stand mixture may affect biomass allometric relationships in Norway spruce (Picea abies (L.) Karst.). Analysis of aboveground biomass data was conducted for 50 trees: 25 sample trees from a pure Norway spruce stand and 25 from a mixed stand of Norway spruce with European beech (Fagus sylvatica L.). ANCOVA results demonstrated that individual-tree biomass allometry of the pure stand significantly differed from that of the mixed stand. Allometric characteristics depended on the biomass component recorded and the type of biomass predictor used. When predicted by diameter at breast height and (or) height, the total aboveground biomass of mixed-stand trees was significantly less than that for pure-stand trees. This “apparent” lower aboveground biomass was attributed to the lower branch and needle biomass proportions of trees growing in mixed stand. The findings indicate that caution should be exercised when applying biomass allometric models developed from pure stands to predict tree biomass in mixed stands (and vice versa), as such data treatment may introduce significant bias.
A mixed-methods approach is evaluated for exploring collaborative behaviour, acceptance and progress surrounding an interactive technology for learning computer programming. A review of literature reveals a compelling case for using mixed-methods approaches when evaluating technology-enhanced-learning environments. Here, ethnographic approaches used for the requirements engineering of computing systems are combined with questionnaire-based feedback and skill tests. These are applied to the 'Ceebot' animated 3D learning environment. Video analysis with workplace observation allowed detailed inspection of problem solving and tacit behaviours. Questionnaires and knowledge tests provided broad sample coverage with insights into subject understanding and overall response to the learning environment. Although relatively low scores in programming tests seemingly contradicted the perception that Ceebot had enhanced understanding of programming, this perception was nevertheless found to be correlated with greater test performance. Video analysis corroborated findings that the learning environment and Ceebot animations were engaging and encouraged constructive collaborative behaviours. Ethnographic observations clearly captured Ceebot's value in providing visual cues for problem-solving discussions and for progress through sharing discoveries. Notably, performance in tests was most highly correlated with greater programming practice (p≤0.01). It was apparent that although students had appropriated technology for collaborative working and benefitted from visual and tacit cues provided by Ceebot, they had not necessarily deeply learned the lessons intended. The key value of the 'mixed-methods' approach was that ethnographic observations captured the authenticity of learning behaviours, and thereby strengthened confidence in the interpretation of questionnaire and test findings.
- Jul 2014
This paper discusses the patterns of network dynamics within a multicultural online collaborative learning environment. It analyses the interaction of participants (both students and facilitators) within a discussion board that was established as part of a 3-month online collaborative course. The study employs longitudinal probabilistic social network analysis (SNA) to identify the patterns and trends within the network. It conjectures and tests a set of hypotheses concerning the tendencies towards homophily/heterophily and preferential attachment. The paper presents identified interaction network patterns in relation to cultural differences. It also evaluates network dynamics by considering participant roles and group work in the course under study. Results of social network analyses are reported along with measures of statistical confidence in findings. The potential for extending exploratory SNA methods and visualisation techniques in educational research are discussed here.
- Aug 2009
- Advances in Web Based Learning - ICWL 2009, 8th International Conference, Aachen, Germany, August 19-21, 2009. Proceedings
The paper summarizes participatory action research that explores student attitudes towards a peer assessment exercise and further reveals a distinctive pattern in student responses. A formative and reciprocal peer assessment exercise was studied to identify possible reasons for low levels of student participation. The target group included students in an undergraduate course in computing. A follow-up questionnaire, undertaken by 36 students, was analyzed and compared against assignment marks. Finally, the access statistics of the virtual learning environment (VLE) were examined. The major results indicate the following: [i] an expectation of more explanatory and supportive tutor intervention; [ii] a student preference towards anonymity; [iii] student interest in accessing peer work; and [iv] that the allocation of marks and in-class activities factors are important in encouraging student involvement.
This paper describes an investigation of web-based peer assessment undertaken by undergraduate students. The study endeavours to offer reasons for low levels of participation and suggest means for improving levels of engagement in peer-review processes. Results are based on formative peer assessments and a follow-up questionnaire completed by 36 computing students. The paper discusses the potential limitations of the teaching methods and technologies used. Results highlight the importance of: (1) formally supporting peer-review activity during in-class sessions; (2) providing a mechanism for anonymous participation; and (3) allocating marks for increasing student participation in the peer-review process.
- Jan 2009
Making information and decision-making processes accessible to disadvantaged and nonliterate people is a challenge for community forestry in Nepal. In studies jointly conducted by the Nepal–UK Community Forestry Project (NUKCFP) and His Majesty's Government (HMG) of Nepal Department of Forest, aerial photographs and participatory photomapping (tracing maps over aerial photographs) were evaluated with a view to supporting participatory processes of community forestry in Parbat District of the Middle Hill Region. Results indicate that, regardless of educational status, most people accurately interpreted forest condition and profiles of community use from photographs. Photographs were appreciated because they presented authentic information, allowed consistency of interpretation between groups, and made it possible to calibrate perceptions of resources. District Forest Officers and Community Forestry Officers valued aerial photographs as robust instruments that naturally directed discussions toward community and resource issues. Results of a pilot study of the use of aerial images for surveys indicated that orthorectified aerial images may substantially reduce time spent by District Forest Office (DFO) staff in chain-and-compass surveys of community forests. Surveys based on aerial images encourage the participation of users, and boundaries drawn over survey photomaps are represented in the context of important reference information contained in the photographic image. The development of a service for low-cost printing of high-resolution and geographically correct photomaps is described.
This paper reports early findings of an ongoing study to determine the use and impact of social educational software at undergraduate level. It summarizes the theoretical background to the educational use of social software and suggests directions for future research. The primary aim of the study was to capture and describe the extent and patterns of use of educational software and Web 2.0 technologies among first year undergraduate technology students taking the Web Development module. Results indicate  great variations in the ways in which students engage with both social and content-centred educational software environments; and  similarities in the ways of using social software within and outside the educational context.
The term "shake" describes the presence of longitudinal separations in the wood of living trees. Predisposition to shake in Quercus robur and Q petraea increases with the cross-sectional areas of earlywood vessels. Investigations suggest that vessel area is under strong genetic control, and is related to provenance and to the timing of leaf emergence in the spring. These results are promising for those concerned with selecting oak varieties less prone to shake or wishing to recognize and remove shake-prone trees early in rotations. Déterminisme génétique du diamètre des vaisseaux du bois chez le chêne (Quercus robur et Q petraea Liebl) : une caractéristique liée à la sensibilité aux fentes internes du tronc. Le terme de «fente» désigne la présence de séparations longitudinales dans le bois des arbres vivants. La prédisposition aux fentes chez Quercus robur et Q petraea augmente avec la surface de la section transversale des vaisseaux du bois initial. Des recherches suggèrent que la surface des vaisseaux est soumise à un contrôle génétique fort (niveau intraspécifique et niveau génétique individuel), ainsi qu'à la période d'apparition des feuilles au printemps. Ces résultats sont prometteurs pour ceux qui s'intéressent à la sélection des variétés de chêne peu sensibles aux fentes du tronc ou qui souhaitent repérer et éliminer précocement les arbres sensibles aux fentes lors d'éclaircies.
- Jan 1990
Previous work by Savill (1986) has shown that oak trees (Quercus robur and Q. petraea) with large earlywood vessels appear to have a much greater predisposition to shake than trees with smaller vessels. The aim of the investigation described here was to determine whether there are any externally visible characteristics correlated with vessel size, so that shake-prone trees can be recognized in the field. It was found that trees that flush latest within a population tend to have the biggest vessels. Possible reasons for this correlation are discussed briefly. The finding has the practical value that oaks which are predisposed to shake can be marked at flushing time and removed in thinning operations.
SUMMARY The main purpose of the work reported is the field-evaluation of large-scale aerial photographs (1:1,250 and 1:2,500 scale) as non-literate aids for supporting participatory work by Forest User Groups (FUGs) and for participatory mapping of community forests in Nepal. Aerial photographs used in conjunction with a Geographical Information System (GIS) were also tested as a possible alternative to current chain-and-compass practices for surveying community forests. Survey maps are required for the preparation of community forest Operational Plans, which constitute legal agreements between Forest User Groups and His Majesty's Government of Nepal.
Thesis (M. Sc.)--University of Wales (U.C.N.W., Bangor: Forestry and Wood Science), 1989.