1. The Amazon region may experience increasing moisture limitation over this century. Leaf dark respiration (R) is a key component of the Amazon rain forest carbon (C) cycle, but relatively little is ...known about its sensitivity to drought. 2. Here, we present measurements of R standardized to 25 °C and leaf morphology from different canopy heights over 5 years at a rain forest subject to a large-scale through-fall reduction (TFR) experiment, and nearby, unmodified Control forest, at the Caxiuanã reserve in the eastern Amazon. 3. In all five post-treatment measurement campaigns, mean R at 25 °C was elevated in the TFR forest compared to the Control forest experiencing normal rainfall. After 5 years of the TFR treatment, R per unit leaf area and mass had increased by 65% and 42%, respectively, relative to pre-treatment means. In contrast, leaf area index (L) in the TFR forest was consistently lower than the Control, falling by 23% compared to the pre-treatment mean, largely because of a decline in specific leaf area (S). 4. The consistent and significant effects of the TFR treatment on R, L and S suggest that severe drought events in the Amazon, of the kind that may occur more frequently in future, could cause a substantial increase in canopy carbon dioxide emissions from this ecosystem to the atmosphere.
Incident analysis of traditional burns in Portugal de Oliveira, Emanuel; Lobo-do-Vale, Raquel; Colaço, Maria Conceição
International journal of disaster risk reduction,
September 2023, 2023-09-00, Letnik:
95
Journal Article
Recenzirano
Odprti dostop
In Portugal, each year, the news typically report one or two cases of elderly farmer fatalities or injuries. However, in 2018, a startling 20 incidents were documented. This study aims to analyse the ...various factors that may account for this unusual surge in the numbers.
To gather comprehensive and organized data on the incidents, a meticulous review of both regional and national news sources was conducted from 2008 to 2021. This enabled the collection of various variables, including date, location, gender, age, and other pertinent information. Additionally, meteorological data related to wildfire risk, sociodemographic indices, and the legislative context were also incorporated to provide a more complete understanding of the incidents.
Between 2008 and 2021, a total of 54 incidents were recorded, with fatalities accounting for 78% of cases. The exceptional rise in incidents in 2018 constituted 37% of the total incidents. The majority of incidents involved elderly individuals (82%) and were primarily males (80%). March and October were the months when most incidents occurred. After conducting meteorological, social, and legislative analyses, it was found that the primary driver behind the dramatic increase in incidents in 2018 was most probably the intense pressure to manage the vegetation, due to an impending deadline for fuel reductions, along with stricter inspections and law enforcement that doubled the fines for non-compliance.
•Between 2008 and 2021 there were 54 incidents of fire use, mainly with slash-burns.•The year 2018 concentrates 37% of all the incidents analyzed.•The victims were mostly male and above 65 years old.•Neither meteorology nor sociodemographic indices explain the spiked 2018 number.•Legislation and social pressure for fuel reduction could explain 2018 incidents.
The flux (R(s)) and carbon isotopic composition (delta(13)C (Rs)) of soil respired CO (2) was measured every 2 h over the course of three diel cycles in a Mediterranean oak woodland, together with ...measurements of the delta(13)C composition of leaf, root and soil organic matter (delta(13)C (SOM)) and metabolites. Simulations of R(s) and delta(13)C (Rs) were also made using a numerical model parameterised with the SOM data and assuming short-term production rates were driven mainly by temperature. Average values of delta(13)C (Rs) over the study period were within the range of root metabolite and average delta(13)C (SOM) values, but enriched in (13)C relative to the bulk delta(13)C of leaf, litter, and roots and the upper soil organic layers. There was good agreement between model output and observed CO (2) fluxes and the underlying features of delta(13)C (Rs). Observed diel variations of 0.5 per thousand in delta(13)C (Rs) were predicted by the model in response to temperature-related shifts in production rates along a approximately 3 per thousand gradient observed in the profile of delta(13)C (SOM). However, observed delta(13)C (Rs) varied by over 2 per thousand, indicating that both dynamics in soil respiratory metabolism and physical processes can influence short-term variability of delta(13)C (Rs).
The flux (R
s
) and carbon isotopic composition (δ
13
C
Rs
) of soil respired CO
2
was measured every 2 h over the course of three diel cycles in a Mediterranean oak woodland, together with ...measurements of the δ
13
C composition of leaf, root and soil organic matter (δ
13
C
SOM
) and metabolites. Simulations of R
s
and δ
13
C
Rs
were also made using a numerical model parameterised with the SOM data and assuming short-term production rates were driven mainly by temperature. Average values of δ
13
C
Rs
over the study period were within the range of root metabolite and average δ
13
C
SOM
values, but enriched in
13
C relative to the bulk δ
13
C of leaf, litter, and roots and the upper soil organic layers. There was good agreement between model output and observed CO
2
fluxes and the underlying features of δ
13
C
Rs
. Observed diel variations of 0.5 ‰ in δ
13
C
Rs
were predicted by the model in response to temperature-related shifts in production rates along a ∼3 ‰ gradient observed in the profile of δ
13
C
SOM
. However, observed δ
13
C
Rs
varied by over 2 ‰, indicating that both dynamics in soil respiratory metabolism and physical processes can influence short-term variability of δ
13
C
Rs
.
PDF
