Long-term thermal sensitivity of Earth’s tropical forests

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (−9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth’s climate

Mucuna pruriens: Improvement of the biotechnological production of the anti-Parkinson drug L-dopa by plant cell selection

Routinely grown cell suspension cultures of Mucuna pruriens L. (Fabaceae) were able to endogenously accumulate the anti-Parkinson drug L-dihydroxyphenylalanine (L-dopa) in the range between 0.2 and 2% on a dry weight (DW) basis. The green colour that developed in light-exposed cultures, appeared to be a suitable marker to select cells with an increased L-dopa biosynthesis and/or phenoloxidase activity. For this purpose, saccharose concentrations from 0 to 4% (w/v), and light intensities of 1,000 and 2,000 lux, were involved in the selection procedure. After 6 months, photomixotrophic callus cultures with a rapid growth and a high L-dopa content of 0.9% (DW) were obtained on 2% saccharose and under 1,000 lux. The cell suspensions, derived from these calli, accumulated up to 6% (DW) L-dopa, which was the highest stable content ever measured in cultures of M. pruriens. An L-dopa yield of approximately 1.2 g/l was calculated after 6 days of growth. In contrast, compared with the standard-grown parent cell line, the phenoloxidase activity, and consequently the bioconversion capacity as measured after entrapment in calcium alginate, of these high-producing cultures was approximately threefold lower

Soil nutrients and soil carbon storage : modulators and mechanisms

It is well recognized that the capacity of soils to sequester carbon (C) is strongly influenced by nitrogen (N) and phosphorus (P) availability because of the strong stoichiometric links between these biogeochemical cycles. Human disturbance (e.g., deposition, fertilization, and mining), has, and continue to have, caused large imbalances between the biogeochemical cycles and changing nutrient availabilities identified as a key uncertainty in predicting future ecosystem C sequestration. Despite this knowledge, key gaps exist in our understanding of the mechanisms that drive the interactions between C and nutrient cycles, which limit our ability to predict the impacts of change on future soil C sequestration. In this chapter, we discuss N, P, and other nutrients as key modulators of soil C storage. We consider two contrasting mechanistic theories—microbial nutrient mining (MNM) theory and basic stoichiometric decomposition theory—driving these modulators, as well as the impact that environment and land-use change is likely to have, and the expected consequences for soil C storage. Overwhelmingly, experimental evidence from the micro- to global-scale support MNM theory as the main mechanism of the impact of nutrients on soil C storage, and suggest that increasing N availability inhibits enzymes responsible for recalcitrant C degradation and thus promotes long-term C storage in soils. A better mechanistic understanding of the interactions between resource and biomass stoichiometry, microbial nutrient use efficiency, and litter chemistry, as well as improved knowledge of P mineralization, sorption, limitation, and stoichiometry is needed to improve parameterization of N- and P cycling into C-cycling models

Data from Sullivan et al. (2020) Long-term thermal sensitivity of Earth’s tropical forests. Science. DOI: 10.1126/science.aaw7578.

ABSTRACT: The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (−9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater rate of decline in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth’s climate