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York R.A.,University of California at Berkeley | Battles J.J.,University of California at Berkeley | Wenk R.C.,University of California at Berkeley | Saah D.,Spatial Informatics Group LLC
Forestry | Year: 2012

Multi-aged stands in a mixed conifer forest of California were treated to mitigate harvest-related increases in surface fuels and to prepare sites for natural regeneration of Pinus species. The study was designed to (1) assess effectiveness of small gap fuel treatments (piling and burning in 0.04 ha gaps) on surface fuel and modelled fire behaviour; (2) test the effect of substrate quality on germination of Pinus species; (3) measure the influence of gap creation on light availability and stand-level light heterogeneity. While the fuel treatment only covered 10 per cent of stand area, it was effective in avoiding increases in stand-level surface fuel following harvests. Fire behaviour was predicted to be moderate following the treatments. The harvest coupled with the gap surface fuel treatments did not change predicted fire behaviour compared with the pretreatment stands. There was a significant but variable increase in germination of Pinus ponderosa seed when sowed on ash substrates compared with bare soil. No substrate effect was detected for Pinus lambertiana. The 0.04-ha gaps created distinct pockets of light and greatly increased stand-level light heterogeneity. This gap-based approach to regenerating multi-aged stands coupled with small-scale fuel treatments is promising for reducing fire hazard and regenerating shade-intolerant species. © Institute of Chartered Foresters, 2011. All rights reserved. Source

Gunn J.S.,Initiative Capital | Saah D.S.,Spatial Informatics Group LLC | Fernholz K.,Dovetail | Ganz D.J.,Nature Conservancy
Forest Science | Year: 2011

We evaluated the implications of area regulation of harvest on eligible carbon under both the Voluntary Carbon Standard (VCS) and the Chicago Climate Exchange (CCX) for public forest lands in north central Minnesota (89,840 ha total). We used data from the carbon submodel of the US Forest Service Forest Vegetation Simulator (Lake States variant) to evaluate changes in forest carbon stocks under different management scenarios. Baseline harvest intensity was defined by considering the manager's short-range tactical plans and the distribution of harvests by cover type and intensity class then became the "business as usual" (BAU) for use in the calculation of eligible carbon under the VCS and CCX. Under VCS, the most effective way to increase carbon stocks while meeting other management objectives was to shift harvest practices to lower intensity entries and retain higher residual basal areas. The carbon stock change rates for each manager varied significantly under the BAU scenario and resulted in a mean annual net decrease. Because CCX carbon credit eligibility requires a net increase of carbon stocking from the base year, area regulation may create periods of time where there is no eligible carbon volume. An alternate management strategy that uses the area regulation method, reduces harvest intensity, and decreases overall acreage harvested was able to provide higher postharvest carbon stocks versus the BAU scenario under VCS. © 2011 by the Society of American Foresters. Source

Chen Q.,University of Hawaii at Manoa | Vaglio Laurin G.,University of Rome Tor Vergata | Vaglio Laurin G.,CMCC Centro Mediterraneo per i Cambiamenti Climatici | Battles J.J.,University of California at Berkeley | And 2 more authors.
Remote Sensing of Environment | Year: 2012

The relationship between lidar-derived metrics and biomass could vary across different vegetation types. However, in many studies, there are usually a limited number of field plots associated with each vegetation type, making it difficult to fit reliable statistical models for each vegetation type. To address this problem, this study used mixed-effects modeling to integrate airborne lidar data and vegetation types derived from aerial photographs for biomass mapping over a forest site in the Sierra Nevada mountain range in California, USA. It was found that the incorporation of vegetation types via mixed-effects models can improve biomass estimation from sparse samples. Compared to the use of lidar data alone in multiplicative models, the mixed-effects models could increase the R 2 from 0.77 to 0.83 with RMSE (root mean square error) reduced by 10% (from 80.8 to 72.2Mg/ha) when the lidar metrics derived from all returns were used. It was also found that the SAF (Society of American Forest) cover types are as powerful as the NVC (National Vegetation Classification) alliance-level vegetation types in the mixed-effects modeling of biomass, implying that the future mapping of vegetation classes could focus on dominant species. This research can be extended to investigate the synergistic use of high spatial resolution satellite imagery, digital image classification, and airborne lidar data for more automatic mapping of vegetation types, biomass, and carbon. © 2012 Elsevier Inc. Source

Buchholz T.,University of Vermont | Buchholz T.,Spatial Informatics Group LLC | Da Silva I.,Strathmore University | Furtado J.,KTH Royal Institute of Technology
Proceedings of Institution of Civil Engineers: Energy | Year: 2012

Wood gasification systems have the potential to contribute to rural electrification in sub-Saharan Africa. This paper presents an operational and economic analysis of two wood-based gasification systems (250 kW and 10 kW) installed in Uganda in 2007. Both systems proved their potential to compete economically with diesel-generated electricity when operating close to the rated capacity. At an output of 150 kW running for approximately 12 h/day and 8 kW running for approximately 8 h/day, the systems produced electricity at USδ0.18 and 0.34/kWh, respectively. A stable electricity demand close to the rated capacity proved to be a challenge for both systems. Fuelwood costs accounted for approximately USδ0.03 kWh for both systems. Recovery of even a small fraction of the excess heat (22%) already resulted in substantial profitability gains for the 250 kW system. Results indicate that replicating successful wood gasification systems stipulates the integration of sustainable fuelwood supply and viable business models. Source

Alix-Garcia J.,University of Wisconsin - Madison | Bartlett A.,University of San Francisco | Saah D.,University of San Francisco | Saah D.,Spatial Informatics Group LLC
Journal of Economic Geography | Year: 2013

This article examines spatial changes in production in the presence of civil conflict. A simple model predicts land abandonment which increases with proximity to insecurity, and welfare losses to rural land owners. The model also predicts that food aid can buffer the land-use change impacts generated by war. Spatial data on land use, violent events, displaced populations and aid from 2001-2007 corroborate these predictions in Darfur, Sudan. The results suggest large disruptions in short-term production, with abandonment of agriculture far from the cities, and intensification of land use on their periphery. © The Author (2013). Published by Oxford University Press. All rights reserved. Source

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