Biotic and Abiotic Interactions in Ecosystems

Biotic and Abiotic Interactions in Ecosystems Plants live in complex environments where many biotic and abiotic factors limit or promote productivity and carbon biosequestration. Temperature and water extremes, nutrient and other resource availabilities, microbeinduced diseases, and insect attacks can limit plant productivity. At the same time, this productivity intimately depends on plant interactions with certain beneficial microorganisms (as described in Chapter 3, Carbon Flows in Ecosys­ tems, p. 27) and access to appropriate temperature, water, and light regimes. Furthermore, these biotic and abiotic factors can influence each other, giving rise to complex environmental conditions to which plants must adapt. This complex­ ity is illustrated by millions of acres of bark-beetle outbreaks triggered by warm­ ing climates that in turn increase winter survival of bark-beetle populations. In the coming decades, such ecological complexities will pose increasing challenges in both agricultural and natural ecosystems (see Chapter 5, Ecosystem Dynam­ ics, p. 71, for a discussion on the impacts of climate change on the frequency and severity of such disturbances).