Browsing by Author "Williams, Jimmy R."
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- Efeitos da aplicação de medidas de sustentabilidade florestal à escala da paisagem em processos hidrológicosPublication . Azevedo, João; Williams, Jimmy R.; Messina, Michael G.; Fisher, Richard F.Neste trabalho analisaram-se através de modelação e simulação os efeitos da aplicação de medidas com expressão ao nível da paisagem do Sustainable Forestry lnitiative (SFI), o programa de sustentabilidade da industria florestal nos EUA, em processos hidrológicos. Um cenário em que foram simuladas medidas como restrição da dimensão máxima de cortes rasos, imposição de regras de adjacência de cortes e ainda estabelecimento e manutenção de buffers arbóreos ao longo de cursos de água foi comparado com outro cenário onde estas medidas não foram aplicadas. Como área de estudo foi utilizada uma paisagem florestal localizada na região Leste do Estado do Texas, EUA, gerida de forma intensiva.
- Effects of the Sustainable Forestry Initiative on Landscape Pattern and ProcessesPublication . Azevedo, João; Wu, X. Ben; Messina, Michael G.; Williams, Jimmy R.; Fisher, Richard F.We used simulation modeling to study the changes in landscape pattern and function resulting from the application of the Sustainable Forestry Initiative (SFI) program in East Texas, USA. Changes in landscape structure were examined by comparing landscapes with different management histories. The effects of pattern on processes were analyzed considering vertebrate habitat quality and configuration and hydrological processes such as water and sediment yield. Landscapes managed according to the SFI program presented increased general fragmentation. The application of measures under SFI increased habitat diversity in the landscape as well as Habitat Suitability Index (HSI) values for most of the species. Habitat for species requiring large patches of mature forest was almost absent. Landscapes managed under the SFI program showed lower sediment yield at the watershed level than those under the non-SFI program due to higher channel erosion related to the absence of buffer strips in the non-SFI scenario.
- Impacts of the sustainable forestry initiative landscape level measures on hydrological processesPublication . Azevedo, João; Williams, Jimmy R.; Messina, Michael G.; Fisher, Richard F.The effects on hydrological processes of the application of the landscape level measures included in the sustainable forestry initiative (SFI) program were analyzed through simulation. A landscape scenario where limitation of harvesting units’ size, imposition of a green-up interval, and establishment of streamside management zones (SMZ) were simulatedwas compared with a reference scenario where no SFI rules were followed. An intensively managed forested landscape located in East Texas, USA, was used as the study area. The HARVEST landscape model was used to simulate landscape pattern and a modified version of the APEX model was used to simulate hydrological processes. Water and sediment yields were generally small within the observation period and most of the runoff and erosion observed occurred during intense storm events. Water and sediment yield at the subarea level and water yield at the watershed level were similar in both scenarios. However, sediment yield at the watershed level was higher in the non-SFI scenario. The differences were due to the reduction in channel erosion resulting from the presence of SMZs. The effect of buffer zones in terms of sediment deposition was not different between scenarios, which can be attributed to the level slopes of the study area. Landscape measures of the SFI program, namely buffer zones, seem important in reducing channel degradation, particularly during major storm events, in intensively managed forest landscapes in East Texas.
- The role of the sustainable forestry Initiative in forest landscape changes in Texas, USAPublication . Azevedo, João; Wu, X. Ben; Messina, Michael G.; Williams, Jimmy R.; Fisher, Richard F.We studied the changes in landscape pattern and function resulting from the application of the Sustainable Forestry Initiative (SFI) in East Texas, USA. Changes in landscape structure were studied by comparing land-scapes with different management histories. A methodology to integrate landscape and stand pattern dynamics with processes was developed based upon modeling and simulation. The effects of pattern on processes were analyzed with this methodology considering the quality, quantity and con-figuration of vertebrate habitat and hydrological processes. Comparisons among landscapes revealed that forest management has a strong influence on landscape structure. The SFI program has increased overall fragmentation with an increase in number of patches, length of edges and shape complexity and a decrease in patch size, and number and size of core areas. Management according to the SFI program resulted generally in higher habitat suitability for many of the species analyzed and higher habitat di-versity in the landscape. The SFI program induced fragmentation of the habitat of pine warbler and the establishment of narrow and elongated habitats in a network structure for most of the remaining species. Land-scapes managed under the SFI program showed lower sediment yield at the watershed level than those under the non-SFI program due to lower channel erosion. The effects of the SFI program at the landscape level are related to the network of buffer strips. In general we conclude that relevant measures at the landscape level improve the sustainability of forested landscapes in East Texas.