Lloret F., Calvo E., Pons X., Díaz-Delgado R. (2002) Wildfires and landscape patterns in the Eastern Iberian Peninsula. Landscape Ecology. 17: 745-759.EnllaçDoi: 10.1023/A:1022966930861
The relations between disturbance regime and landscape patterns have been developed from a theoretical perspective, but few studies have tested these relations when forces promoting opposing heterogeneity patterns are simultaneously operating on a landscape. This work provides quantitative evidence of these relations in areas dominated by human activity, showing that landscape heterogeneity decreases disturbance spread. In turn, disturbance introduces a source of landscape heterogeneity, but it is not enough to counterbalance the homogeneity trend due to agricultural abandonment. Land cover changes and wildfire occurrence (fires larger than 0.3 km2) have been monitored in the Tivissa municipality (208.4 km2) (Catalonia, NE Spain) from 1956 to 1993. Land cover maps were obtained from 1956, 1978 and 1993 and they were overlaid with fire occurrence maps obtained for the 1975-1995 period from 60 m resolution remote sensing images, which allow the identification of burned areas by sudden drops in Normalized Difference Vegetation Index (NDVI). Changes in landscape patterns in relation to fire regime have been analyzed considering several parameters: patch density, mean patch size, mean distance to the nearest neighbour of the same category, edge density, and the Shannon diversity index. In the 1956-1993 period there is a trend to increasing landscape homogenization due to the expansion of shrublands linked to a decrease in forest surface, and to the abandonment of agricultural lands. This trend, however, is not constant along all the period. Fires are more likely to occur in woody, homogenous areas, increasing landscape heterogeneity, as observed in the 1978-1993 period. This increase in heterogeneity does not counterbalance the general trend to landscape homogenization as a consequence of agricultural abandonment and the coalescence of natural vegetation patches.
Díaz-Delgado R., Pons X. (2001) Spatial patterns of forest fires in Catalonia (NE of Spain) along the period 1975-1995 analysis of vegetation recovery after fire. Forest Ecology and Management. 147: 67-74.EnllaçDoi: 10.1016/S0378-1127(00)00434-5
This paper revises the results of applying a semiautomatic methodology for fire scars mapping from a time series of Landsat MSS images over the forest and shrubby surface of Catalonia (1975-1993). Perimeters of fires which occurred in 1994 and 1995 were added enlarging the whole series to 21 years from TM imagery. Results are a map series of fire history during 21 years as well as a map of the fire recurrence level. Omission errors are 23% for burned areas greater than 2 km2 while commission errors are 8% for areas greater than 0.5 km2. Detected fire scars were incorporated into a geographic information system in order to characterise the fire regime of the study area. Fire size distribution and the number of spot fires originated from each fire as well as the maximum distance reached from the main fire are analysed. A first approach to monitor post-burn regeneration through normalised difference vegetation index is also shown. © 2001 Elsevier Science B.V.
Ninyerola M., Pons X., Roure J.M. (2000) A methodological approach of climatological modelling of air temperature and precipitation through GIS techniques. International Journal of Climatology. 20: 1823-1841.EnllaçDoi: 10.1002/1097-0088(20001130)20:14<1823::AID-JOC566>3.0.CO;2-B
This study proposes an empirical methodology for modelling and mapping the air temperature (mean maximum, mean and mean minimum) and total precipitation, all of which are monthly and annual, using geographical information systems (GIS) techniques. The method can be seen as an alternative to classical interpolation techniques when spatial information is available. The geographical area used to develop and apply this model is Catalonia (32000 km2, northeast Spain). We have developed a multiple regression analysis between these meteorological variables as the dependent ones, and some geographical variables (altitude (ALT), latitude (LAT), continentality (CON), solar radiation (RAD) and a cloudiness factor (CLO)) as the independent ones. Data for the dependent variables were obtained from meteorological stations, and data for the independent variables were elaborated from a 180 m resolution digital elevation model (DEM). Multiple regression coefficients (bn) were used to build final maps, using digital layers for each independent variable, and applying basic GIS techniques. The results are very satisfactory in the case of mean air temperature and mean minimum air temperature, with coefficients of determination (R2) between 0.79 and 0.97, depending on the month; in the case of mean maximum air temperature, R2 ranges between 0.70 and 0.89, while in the case of precipitation, it ranges between 0.60 and 0.91. Copyright © 2000 Royal Meteorological Society.
Baulies X., Pons X. (1995) Approach to forestry inventory and mapping by means of multi-spectral Airborne data. International Journal of Remote Sensing. 16: 61-80.EnllaçDoi: 10.1080/01431169508954372
In this study we evaluate the possibilities of the airborne sensor CASI (Compact Airborne Spectrographic Imager) when applied to mapping of variables characteristic of an ecologic and forestry inventory, i.e., wood biomass, leaf biomass, leaf area index (LAI), canopy cover, etc. The use of multiple regression techniques has made possible to obtain correlation values between 0.76 and 0.94 (p
Doblas-Miranda E., Martinez-Vilalta J., Lloret F., Alvarez A., Avila A., Bonet F.J., Brotons L., Castro J., Curiel Yuste J., Diaz M., Ferrandis P., Garcia-Hurtado E., Iriondo J.M., Keenan T.F., Latron J., Llusia J., Loepfe L., Mayol M., More G., Moya D., Penuelas J., Pons X., Poyatos R., Sardans J., Sus O., Vallejo V.R., Vayreda J., Retana J. (0) Reassessing global change research priorities in mediterranean terrestrial ecosystems: How far have we come and where do we go from here?. Global Ecology and Biogeography. 24: 25-43.EnllaçDoi: 10.1111/geb.12224
Aim: Mediterranean terrestrial ecosystems serve as reference laboratories for the investigation of global change because of their transitional climate, the high spatiotemporal variability of their environmental conditions, a rich and unique biodiversity and a wide range of socio-economic conditions. As scientific development and environmental pressures increase, it is increasingly necessary to evaluate recent progress and to challenge research priorities in the face of global change. Location: Mediterranean terrestrial ecosystems. Methods: This article revisits the research priorities proposed in a 1998 assessment. Results: A new set of research priorities is proposed: (1) to establish the role of the landscape mosaic on fire-spread; (2) to further research the combined effect of different drivers on pest expansion; (3) to address the interaction between drivers of global change and recent forest management practices; (4) to obtain more realistic information on the impacts of global change and ecosystem services; (5) to assess forest mortality events associated with climatic extremes; (6) to focus global change research on identifying and managing vulnerable areas; (7) to use the functional traits concept to study resilience after disturbance; (8) to study the relationship between genotypic and phenotypic diversity as a source of forest resilience; (9) to understand the balance between C storage and water resources; (10) to analyse the interplay between landscape-scale processes and biodiversity conservation; (11) to refine models by including interactions between drivers and socio-economic contexts; (12) to understand forest-atmosphere feedbacks; (13) to represent key mechanisms linking plant hydraulics with landscape hydrology. Main conclusions: (1) The interactive nature of different global change drivers remains poorly understood. (2) There is a critical need for the rapid development of regional- and global-scale models that are more tightly connected with large-scale experiments, data networks and management practice. (3) More attention should be directed to drought-related forest decline and the current relevance of historical land use.
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