Water limitation can negate the effect of higher temperatures on forest carbon sequestration

Climate change may lead to alterations in tree growth and carbon cycling. Interpreting the response of forest growth to climate change requires an understanding of the temporal and spatial patterns of seasonal climatic influences on the growth of tree species. However, the effects of climate change on pine forest dynamics in tropical region of Thailand remain poorly understood. This study develops three new tree ring-width chronologies of Pinus latteri (Tenasserim pine) in northern and northeastern Thailand and analyzes their climate-growth relationships and temporal stability. Ring-width chronologies of P. latteri at three sites showed significantly positive correlations with precipitation, relative humidity and self-calibrated Palmer Drought Severity Index (scPDSI) during the dry season (previous November to current April) and early rainy season (May–June). Conversely, significantly negative correlations were found between ring-width site chronologies and air temperatures (mean, maximum and minimum) from April to August. Therefore, our results revealed that radial growth of Tenasserim pines from northern and northeastern Thailand was mainly limited by moisture availability during the dry-to-wet transition season from April to June. Moving correlations revealed that Tenasserim pines in the lowland area of northeastern Thailand became more sensitive to moisture availability in recent 30 years (1985–2017) as compared with early period (1951–1984). Accompanying the shifted growth sensitivity to climate change, growth synchrony among trees was increasing and tree growth rates of Tenasserim pines have been declining during recent decades at two more moisture-limited sites in northeastern Thailand. Recent rapid warming and increasing drought during the transition season (April–June) together intensify climatic constrains on tree growth of Tenasserim pines in the lowland area of northeastern Thailand. Considering continued regional climate change, pine forests in tropical lowland areas may encounter intensified drought stresses, and thus, become more vulnerable to future climate change. Our results serve as an early indicator of potential effects of climate change on tropical pine species and raise concerns about sustainable managements of pine forests under a changing climate.

Section: Growth Synchrony and Long-term Trendsmentioning

confidence: 99%

Increased Drought Sensitivity Results in a Declining Tree Growth of Pinus latteri in Northeastern Thailand

Rakthai

Fan

et al. 2020

“…The very positive impacts of climate change on wood production implemented in Heureka (i.e., [56]) are most likely too optimistic. Belyazid and Giuliana [93] indicate that the positive effects of higher temperature on the increment will be counteracted by lower water availability, especially in the part of Sweden where this study is located. By better accounting for the extreme variations in future climate (e.g., drought, frost), Subramanian et al [94] projected a lower increase in growth in RCP8.5 and RCP4.5 for our study region than what currently is implemented in Heureka (e.g., 21% instead of 36% increase by the end of the century in RCP8.5).…”

Section: Uncertainties and Improvementsmentioning

confidence: 86%

Combining Climate Change Mitigation Scenarios with Current Forest Owner Behavior: A Scenario Study from a Region in Southern Sweden

Lodin

Eriksson

Forsell

et al. 2020

This study investigates the need for change of current forest management approaches in a southern Swedish region within the context of future climate change mitigation through empirically derived projections, rather than forest management according to silvicultural guidelines. Scenarios indicate that climate change mitigation will increase global wood demand. This might call for adjustments of well-established management approaches. This study investigates to what extent increasing wood demands in three climate change mitigation scenarios can be satisfied with current forest management approaches of different intensities in a southern Swedish region. Forest management practices in Kronoberg County were mapped through interviews, statistics, and desk research and were translated into five different management strategies with different intensities regulating management at the property level. The consequences of current practices, as well as their intensification, were analyzed with the Heureka Planwise forest planning system in combination with a specially developed forest owner decision simulator. Projections were done over a 100-year period under three climate change mitigation scenarios developed with the Global Biosphere Management Model (GLOBIUM). Current management practices could meet scenario demands during the first 20 years. This was followed by a shortage of wood during two periods in all scenarios unless rotations were reduced. In a longer timeframe, the wood demands were projected to be easily satisfied in the less ambitious climate change mitigation scenarios. In contrast, the demand in the ambitious mitigation scenario could not be met with current management practices, not even if all owners managed their production forests at the intensive extreme of current management approaches. The climate change mitigation scenarios provide very different trajectories with respect to future drivers of forest management. Our results indicate that with less ambitious mitigation efforts, the relatively intensive practices in the study region can be softened while ambitious mitigation might push for further intensification.

“…The results highlight the relevance of the timing of high temperature and lower water availability and the importance of considering these events in conjunction [65][66][67][68]. The joint effects of high temperatures and low water availability are expected to become even more important in the future since high temperatures and water deficiency during the growing season are likely to become more frequent in boreal regions [69]. Hence, there will be a likely increase in the probability that boreal forests will need to cope with more severe combination of heat waves and droughts [15].…”

Section: Role Of Growing Conditions: the Timing Of Precipitatio Affecmentioning

confidence: 87%

Role of Plant Traits in Photosynthesis and Thermal Damage Avoidance under Warmer and Drier Climates in Boreal Forests

Ruiz-Pérez

Launiainen

Vico

2019

In the future, boreal forests will face warmer and in some cases drier conditions, potentially resulting in extreme leaf temperatures and reduced photosynthesis. One potential and still partially unexplored avenue to prepare boreal forest for future climates is the identification of plant traits that may support photosynthetic rates under a changing climate. However, the interplay among plant traits, soil water depletion and the occurrence of heat stress has been seldom explored in boreal forests. Here, a mechanistic model describing energy and mass exchanges among the soil, plant and atmosphere is employed to identify which combinations of growing conditions and plant traits allow trees to simultaneously keep high photosynthetic rates and prevent thermal damage under current and future growing conditions. Our results show that the simultaneous lack of precipitation and warm temperatures is the main trigger of thermal damage and reduction of photosynthesis. Traits that facilitate the coupling of leaves to the atmosphere are key to avoid thermal damage and guarantee the maintenance of assimilation rates in the future. Nevertheless, the same set of traits may not maximize forest productivity over current growing conditions. As such, an effective trait selection needs to explicitly consider the expected changes in the growing conditions, both in terms of averages and extremes.