Forest Resilience, Biodiversity, and Climate Change

Forest Resilience, Biodiversity, and Climate Changewildfires and hurricanes can significantly affect longtermcarbon budgets. Felzer et al. (2005), predictedthat future climate variability, CO 2 fertilization,nitrogen deposition, and ozone pollution wouldenhance plant growth in temperate ecosystems andincrease carbon sequestration. However, other studieshave suggested that increasing extreme climateevents and disturbances are likely to more thanoffset such fertilization effects in the USA (McNulty2002), and actually exert a positive feedback to theclimate (Gruber et al. 2004). Temperate deciduousforests should continue to provide most of thesame goods and services under climate change ascurrently, although the state, especially the speciescomposition, will be altered (e.g., Fischlin et al.2009), suggesting at least ecological resilience.5.3 Tropical forestsTropical forests are found between 25°N and 25°Sand cover an area of about 17.5 million km 2 (Fischlinet al. 2007). Tropical forests are characterized byhigh alpha diversity, with few highly dominantspecies, especially in rainforests (Mooney et al.1996). These forests range from wet to dry andinclude evergreen rainforests, tropical seasonaldrought-deciduous forests (moist savannahs), andtropical dry forests (dry savannahs). Rainforests arecharacterized by an annual mean temperature above24°C and ≥2.5 m/yr regular precipitation duringthe year, while other tropical forests remain above15.5°C throughout the year (Prentice et al. 1992).Precipitation in rainforests is at least twice thepotential evapotranspiration (Fischlin et al. 2007).Nevertheless, not all rainforests receive the sameprecipitation, with African forests being considerablydrier than many parts of the Amazon, for example.Even within the Amazon basin, there exist gradientsin precipitation. Tropical seasonal forests receivemost of their rainfall during a wet season and have aratio of precipitation to potential evapotranspirationbetween 2 and 1. Seasonal forests are found intropical monsoon regions or other seasonal tropicalwet-dry climate zones and are moist deciduous, i.e.,the trees shed their leaves in the dry season. Tropicaldry forests are characterized by a precipitation topotential evapotranspiration ratio