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Questions Can herbaceous above-ground net primary production ( ANPP) be estimated from remote sensing when woody and herbaceous plants are intermingled? How does herbaceous ANPP change in space and time in an ecosystem dominated by woody species? What are the main controls of herbaceous ANPP to paddock scale? Location Native plant communities and buffelgrass roller chopped pastures of the Arid Chaco, western Argentina (28-32° S, 64-67° W; area: 100 000 km2). Methods We decomposed normalized difference vegetation index ( NDVI) data from MODIS (pixel size: 250 m × 250 m) into woody ( W) and herbaceous ( H) components. We calibrated the relationship between field estimates of herbaceous ANPP and the H component of NDVI using linear regression. The regression model fitted was applied to a 10-yr MODIS database for four paddocks to estimate herbaceous ANPP. We analysed the relationship between herbaceous ANPP and watering point distance and growing season precipitation. Results The annual integral of NDVI × proportion of the herbaceous component [ H/( H + W)] explained 71% and 91% of herbaceous ANPP variation in native plant communities and buffelgrass roller chopped pastures, respectively. The regression model fitted, however, differed (P < 0.05) between the two types of system. The NDVI annual integral explained a higher proportion of herbaceous ANPP variations than the NDVI annual peak or the growing season (December-April) integral. For native plant communities, herbaceous production increased significantly ( P < 0.05) with watering point distance, and marginally significantly ( P < 0.10) with growing season precipitation. For buffelgrass roller chopped pastures, the herbaceous production increased significantly ( P < 0.05) with growing season precipitation. Conclusion Our model was able to estimate herbaceous ANPP from the decomposition of an NDVI time series that included woody components. Thus, the model provides the basis for more accurate monitoring of spatial and temporal variability of herbaceous ANPP in areas where herbaceous and woody plant components co-exist. Applying our models, we detected clear spatial and temporal patterns of herbaceous ANPP. The possibility of describing in a spatially explicit way the past 14 yrs of herbaceous ANPP allows designing livestock management strategies and devise alternatives to control degradation processes in the Arid Chaco. [ABSTRACT FROM AUTHOR]

Question: Is it possible to model the germinative and resprouting behaviour of plant species in Atlantic shrublands and woodlands in relation to fire intensity? Is it possible to recognise different functional regenerative types in these plant species? Location: Galicia, NW Iberian Peninsula. Methods: We explored the patterns of germination and resprouting plant responses in relation to different intensities of fire using data from 37 trees, shrubs and herbaceous species growing in Atlantic shrublands and woodlands. Results: Synthesizing their germinative and resprouting behaviour, we created two graphical models: the Functional Germinative Model (FGM) and the Functional Sprouting Model (FSM). Integrating the germinative and resprouting responses, and taking into account fire intensity, we created the Functional Regenerative Model (FRM), which predicts the post-fire recuperation of the populations of each species. The FRM has been validated with data from four Atlantic communities. We identified four plant functional regenerative types (PFRT) for Atlantic forest vegetation and we propose three intensities of response. Conclusions: The extracted models (FGM, FSM and FRM) and the grouping of species in four PFRTs could be applicable to more Atlantic species, to disturbance ecology in general and to population, community and landscape management. [ABSTRACT FROM AUTHOR]

Question: Plant invasions result from complex interactions between species traits, community characteristics and environmental variations. We examined the effect of these interactions on the invasion potential of two invasive Senecio species, S. inaequidens and S. pterophorus, across three Mediterranean plant communities in a natural park. Location: Catalonia, NE Spain. Methods: We carried out two series of experimental seedling transplantations, in the spring and fall of 2003, in grassland, shrubland and Quercus ilex forest. Competition with neighbouring plants and water availability were manipulated. We evaluated the survival, growth and reproduction with respect to each treatment combination. Results: Any habitat can be colonised if disturbance occurs. In the absence of disturbance, shrubland enhanced the survival of seedlings. Competition with resident vegetation dramatically reduced survival in grassland and forest when establishment occurred in the spring. However, establishment in the fall promoted invasion in grassland and shrubland, even in the undisturbed treatment. Grassland allowed the highest growth and reproductive performance of both species while forest was the most resistant habitat to invasion. S. inaequidens had a higher growth rate and a shorter pre-reproductive period than S. pterophorus. S. pterophorus produced more biomass and was more dependent on water availability than S. inaequidens. Conclusions: In the light of our results, we recommend surveying open shrublands and grasslands after periods of rainfall. Special attention should be paid to S. pterophorus, which is currently spreading. A preliminary assessment of the invasiveness of this plant is given in this study. [ABSTRACT FROM AUTHOR]

Question: What are the main forces driving natural regeneration in burned mature Mediterranean forests in the medium-long term and what are the likely successional trajectories of unmanaged vegetation? Location: Valencia Region, eastern Spain. Methods: A wildfire burned 33 000 ha of Pinus halepensis and P. pinaster forest in 1979, and subsequent smaller wildfires took place between 1984 and 1996. The study was designed to sample the range of environmental and disturbance (fire recurrence and land use) conditions. The territory was classified into 17 different geomorphological and fire-recurrence units. Vegetation cover and floristic composition were measured on a total of 113 plots (1000 m² each) randomly selected within these units. Results: The results show that 23 years after the fire the regenerated vegetation consists of successional shrublands, and that forest ecosystem resilience can be very low. The vegetation presents a strong correlation with most of the environmental variables, but fire (one or two fires), soil type and land use (in that order) are the main drivers of vegetation composition. Quercus coccifera shrublands persist on limestone soils while diverse types of other shrublands (dominated by seeder species) are found on marl soils. Conclusions: The results of this study indicate that disturbance factors strongly coupled to human activities, such as land use and fire, play a critical role in the current state of vegetation. Fire creates vegetation patches in different successional states while land use and soil type define the different types of shrubland in terms of their specific composition. [ABSTRACT FROM AUTHOR]