This post provides some on the ground research and consistent but separate modeling results that demonstrate the importance of stand density in coping with climate change and therefore the importance of sustainable forest management. Hopefully this will change some minds on the importance of strategically managing density.
A) The response of the forest to drought: the role of stand density and species diversity This article is an attempt to quantify previously established science.
1) “Droughts affect wood formation through the reduction in photosynthetic rates due to stomatal closure, reducing the amount of carbohydrates available for building new cells.”
2) “used tree-ring data from long-term forest plots of two pine species, ponderosa pine (Pinus ponderosa) and red pine (Pinus resinosa). The experiments were distributed in different geographical areas in the USA and they covered a large aridity gradient. They quantified growth responses at the population level to express both resistance and resilience to drought in relation to the relative tree population density, finding out that reducing densities would enhance both growth responses to drought. Trees growing in denser populations were more negatively impacted by drought and this has been shown in all three biogeographical areas.”
NOTE from “Climate Change Research Focuses on Great Lakes Forests”: “ASCC is monitoring the growth, health and survival rates of the trees in these forests, and focusing on three key qualities: resistance, resilience and transition. Resistance measures a species’ ability to remain stable and productive in a drought situation, resilience is a tree’s ability to return to normal productivity after experiencing an environmental change and transition refers to circumstances that encourage ecosystems to adapt to changing conditions.”
3) “This study confirms once more that the vulnerability of monospecific coniferous forests to increasing drought can be reduced through thinning interventions, which represent a viable adaptation strategy under climate change.”
4) “investigated the drought response of 16 individual tree species in different regions of Europe and evaluated if this was related to species diversity and stand density. Based on previous findings indicating that combining species with complementary characteristics is more important than simply increasing species diversity to cope with drought, their results indicate that species growing in a mixture are not always less water stressed than those growing in monoculture.”
See also: a) “Species composition determines resistance to drought in dry forests of the Great Lakes – St. Lawrence forest region of central Ontario” b) “SPECIES RICHNESS AND STAND STABILITY IN CONIFER FORESTS OF THE SIERRA NEVADA” c) “Functional diversity enhances silver fir growth resilience to an extreme drought”
5) “Investigating these effects at the level of species identity (i.e., different combinations of species) is more advisable than doing it at the level of species richness (i.e., abundance of species), because different mixtures respond differently depending on the region. If we consider that different provenances of the same species can show different adaptation strategies to cope with drought, the situation may be even more complex.”
B) Ecosystem services, mountain forests and climate change
Note: This modeling effort passes the #1 smell test in that it agrees with already established scientific principles while adding quantitative measures that support the previously known trend but shouldn’t be taken as absolutes.
1) “it is estimated that about half of the global human population depends – directly or indirectly – on services delivered by mountain forests. It is therefore essential to assess whether multiple ecosystem services can be provided to human societies in the future. Given that climate is changing fast, the consideration of climate change in scientific assessments is a must! Let’s not forget that European forests are managed since centuries (check out this nice book about the history of European forests). Thus, changes in management regimes must be considered as well.”
2) “in the Iberian Mountains their simulation results indicate that forest management, rather than climate change, is responsible for a reduction in carbon storage and biodiversity. On the contrary, in Western Alps changes in climatic regimes could induces large alterations in the supply of several ecosystem services, particularly under the most pessimistic future climate scenarios. In other areas (e.g., in the Slovenian Dinaric Mountains) climate change would strongly affect ecosystem services, albeit differently depending on elevation and stand conditions.”
3) “This confirms that management is a strong driver of forest dynamics in European mountains, and it can highly modify the future provision of ecosystem services (i.e., more than the direct effects of climate change!).”