Nutrient and Water Limitations on Carbon Sequestration in Forests

Abstract

In addition to CO2, light, warmth, water, nutrients and growing media are also required for plant growth and net primary production (NPP). Nutrient supply drives C allocation and biomass partitioning into leaves, stems, roots, and in storage and reproductive organs (Ericsson et al. 1996). Thus, C sequestration in forest ecosystems depends on nutrient inputs and their availability (Hessen et al. 2004). Lack of adequate nutrient supply constrains, in particular, the productivity of boreal and temperate forests but nutrient constraints on tropical forest productivity are less well studied (Chapin et al. 2002; Clark 2007). Because the C:nutrient stoichiometry of vegetation and soils differ greatly, C sequestration depends on the distribution of C and nutrients between vegetation and soil (Hessen et al. 2004). Interactions of nutrients affect organic matter (OM) production and decomposition (Melillo et al. 2003). Tree species share the same basic nutrient requirements (Ericsson 1994). However, the quantity of nutrients taken up and returned annually to the forest floor is lower for evergreen compared to other tree species. Important macronutrients are nitrogen (N), phosphorus (P), sulfur (S), potassium (K), calcium (Ca) and magnesium (Mg). Examples of important micronutrients are boron (B), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn) and molybdenum (Mo). In most cases, N is the major limiting nutrient explaining production increases in fertilization experiments (Binkley et al. 1997). In some forests, however, low availability of P, K, Mg, B, Cu, Mn or Zn also limits NPP.