Nutrition of Commercial Pecan nut orchards 1
The role of rainforests in the global carbon cycle is complex and little known. Plants and animals contain a great deal of carbon, which they take up as carbon dioxide (CO2) during growth and photosynthesis, and which they release to the atmosphere during respiration and decomposition. Although rainforests form less than half of the total forest on earth, their leaf systems comprise approximately 70% of the world’s total leaf surface area. Rainforests have ten times more leaf area than temperate forests of comparable size and fifty times more than grasslands. It is not surprising, then, that they account for between 30% and 50% of total primary productivity (photosynthesis) in terrestrial systems, although they cover only 6% of the total land area of the earth. This means that they store more carbon (as sugars and starches) per unit area than any other type of ecosystem. Rainforests are thought to contain between 40% and 50% of the carbon in the terrestrial biomass (Phillips, et al., 1998), which has been estimated as more than 17 kilograms of carbon per square meter. The rainforests of Amazonia contain between 14 and 40 kilograms of carbon per square meter. The soils lying under rainforests also contain substantial amounts of carbon (in roots, microorganisms, soil fungi and plants), which amounts to about 27% of global soil carbon (Lodge, et al., 1996).
Question Bank of Biology Questions and Answers - 3
We present an approach that links time-varying (daily time-step) terrestrial and aquatic ecosystem models at regional scales and apply this model into the future using scenarios of climate and land cover to project changes in ecosystem services. First, we describe an indicator framework that succinctly represents a comprehensive suite of environmental conditions relevant to important ecosystem services. Second, we describe the linkage and validation of the terrestrial and aquatic ecosystem models to simulate aquatic indicators through the 21st century. We integrated the Photosynthetic Evapotranspiration-Carbon and Nitrogen (PnET-CN) forest ecosystem model (Ollinger et al. 2002, 2008, Aber et al. 2005) and the Framework for the Aquatic Modeling of the Earth System (FrAMES) aquatic ecosystem model (Wollheim et al. 2008a, b, Wisser et al. 2010, Stewart et al. 2011, 2013, Mineau et al. 2015; Zuidema, Wollheim, Mineau, et al., unpublished manuscript). These models integrate the dynamics of terrestrial and aquatic processes and linkages at daily time-steps, making them ideal for studying aquatic ecosystem responses in forest-dominated watersheds. In coordination with a separate effort described elsewhere in this special issue (Mavrommati et al. 2017) to assess the value of ecosystem services provided by the Upper Merrimack River watershed (UMRW) of New Hampshire, we contrast two extremes of projected futures in climate and land-cover change. The outcome suggests that climate change influences most indicators of environmental condition in the UMRW more than changes in land cover, although land cover has important interactive capacity to dampen or exacerbate the effects of the changing supply of ecosystem services in the future.
The third way carbon reenters the cycle is through us burning fossil fuels. When we do this, carbon dioxide and water are release into the atmosphere and taken up by plants for use in photosynthesis. Of course, not all of the carbon is immediately taken back up. Some of it remains in the atmosphere, increasing levels of atmosphere carbon dioxide and contributing to the greenhouse effect.