Global synthesis of leaf area index observations: implications for ecological and remote sensing studies

Asner, Gregory P.; Scurlock, J. M. O.; Hicke, Jeffrey A.

doi:10.1046/j.1466-822x.2003.00026.x

Cited by 739 publications

(495 citation statements)

References 53 publications

(75 reference statements)

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“…The comparison pointed to higher than expected concentrations over tropical forest regions, especially in South America. Aerobic CH 4 emission from plants may resolve that discrepancy, and our calculations suggest that aerobic CH 4 emissions are of the same magnitude as total CH 4 emissions reported in a field study from Brazil by do Carmo et al (2006). Other components of the global budget, such as emissions from biomass burning, termites, wetlands, and the CH 4 production / oxidation balance in partly wet soils, as well as oxidation by OH in the atmosphere, however, are all sufficiently uncertain to further account for any remaining discrepancies.…”

Section: The Global Methane Budgetsupporting

confidence: 50%

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A comment on the quantitative significance of aerobic methane release by plants

Kirschbaum

Bruhn

Etheridge

et al. 2006

Functional Plant Biol.

102

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Abstract. A recent study by Keppler et al. (2006; Nature 439, 187-191) demonstrated CH 4 emission from living and dead plant tissues under aerobic conditions. This work included some calculations to extrapolate the findings from the laboratory to the global scale and led various commentators to question the value of planting trees as a greenhouse mitigation option. The experimental work of Keppler et al. (2006) appears to be largely sound, although some concerns remain about the quantification of emission rates. However, whilst accepting their basic findings, we are critical of the method used for extrapolating results to a global scale. Using the same basic information, we present alternative calculations to estimate global aerobic plant CH 4 emissions as 10-60 Mt CH 4 year −1 . This estimate is much smaller than the 62-236 Mt CH 4 year −1 reported in the original study and can be more readily reconciled within the uncertainties in the established sources and sinks in the global CH 4 budget. We also assessed their findings in terms of their possible relevance for planting trees as a greenhouse mitigation option. We conclude that consideration of aerobic CH 4 emissions from plants would reduce the benefit of planting trees by between 0 and 4.4%. Hence, any offset from CH 4 emission is small in comparison to the significant benefit from carbon sequestration. However, much critical information is still lacking about aerobic CH 4 emission from plants. For example, we do not yet know the underlying mechanism for aerobic CH 4 emission, how CH 4 emissions change with light, temperature and the physiological state of leaves, whether emissions change over time under constant conditions, whether they are related to photosynthesis and how they relate to the chemical composition of biomass. Therefore, the present calculations must be seen as a preliminary attempt to assess the global significance from a basis of limited information and are likely to be revised as further information becomes available.

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Section: The Global Methane Budgetsupporting

confidence: 50%

“…although with significant uncertainties still remaining about the exact magnitude of each identified source and sink (Ehhalt et al 2001;Wang et al 2004;Frankenberg et al 2005;do Carmo et al 2006). Keppler et al (2006) recently reported that CH 4 was emitted from dead and living plant material under aerobic conditions.…”

Section: Introductionmentioning

confidence: 99%

A comment on the quantitative significance of aerobic methane release by plants

Kirschbaum

Bruhn

Etheridge

et al. 2006

Functional Plant Biol.

102

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“…Climate change alters wood production by modifying the rates of photosynthesis and respiration rates of trees (Barber et al, 2000;Luo, 2007;Peñuelas and Filella, 2009;Reyer et al, 2014). Changes in forest productivity have been observed in past decades all over the world (Nemani et al, 2003;Boisvenue and Running, 2006;Seddon et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Bontemps et al, 2010;Delpierre et al, 2009;Pan et al, 2013;McMahon et al, 2010) as well as negative ones have been found (e.g. Barber et al, 2000;Jump et al, 2006;Charru et al, 2010). However, it remains unclear why forests react differently to temperature change.…”

Section: Introductionmentioning

confidence: 99%

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Species composition and forest structure explain the temperature sensitivity patterns of productivity in temperate forests

Bohn

Huth

2018

Biogeosciences

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Abstract. Rising temperatures due to climate change influence the wood production of forests. Observations show that some temperate forests increase their productivity, whereas others reduce their productivity. This study focuses on how species composition and forest structure properties influence the temperature sensitivity of aboveground wood production (AWP). It further investigates which forests will increase their productivity the most with rising temperatures. We described forest structure by leaf area index, forest height and tree height heterogeneity. Species composition was described by a functional diversity index (Rao's Q) and a species distribution index ( AWP ). AWP quantified how well species are distributed over the different forest layers with regard to AWP. We analysed 370 170 forest stands generated with a forest gap model. These forest stands covered a wide range of possible forest types. For each stand, we estimated annual aboveground wood production and performed a climate sensitivity analysis based on 320 different climate time series (of 1-year length). The scenarios differed in mean annual temperature and annual temperature amplitude. Temperature sensitivity of wood production was quantified as the relative change in productivity resulting from a 1 • C rise in mean annual temperature or annual temperature amplitude. Increasing AWP positively influenced both temperature sensitivity indices of forest, whereas forest height showed a bell-shaped relationship with both indices. Further, we found forests in each successional stage that are positively affected by temperature rise. For such forests, large AWP values were important. In the case of young forests, low functional diversity and small tree height heterogeneity were associated with a positive effect of temperature on wood production. During later successional stages, higher species diversity and larger tree height heterogeneity were an advantage. To achieve such a development, one could plant below the closed canopy of even-aged, pioneer trees a climax-species-rich understorey that will build the canopy of the mature forest. This study highlights that forest structure and species composition are both relevant for understanding the temperature sensitivity of wood production.

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Root zone salinity and sodicity under seasonal rainfall due to feedback of decreasing hydraulic conductivity

Zee

Shah

Vervoort

2014

Water Resources Research

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Soil sodicity, where the soil cation exchange complex is occupied for a significant fraction by Na 1 , may lead to vulnerability to soil structure deterioration. With a root zone flow and salt transport model, we modeled the feedback effects of salt concentration (C) and exchangeable sodium percentage (ESP) on saturated hydraulic conductivity K s (C, ESP) for different groundwater depths and climates, using the functional approach of McNeal (1968). We assume that a decrease of K s is practically irreversible at a time scale of decades. Representing climate with a Poisson rainfall process, the feedback hardly affects salt and sodium accumulation compared with the case that feedback is ignored. However, if salinity decreases, the much more buffered ESP stays at elevated values, while K s decreases. This situation may develop if rainfall has a seasonal pattern where drought periods with accumulation of salts in the root zone alternate with wet rainfall periods in which salts are leached. Feedback that affects both drainage/leaching and capillary upward flow from groundwater, or only drainage, leads to opposing effects. If both fluxes are affected by sodicityinduced degradation, this leads to reduced salinity (C) and sodicity (ESP), which suggests that the system dynamics and feedback oppose further degradation. Experiences in the field point in the same direction.

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Global synthesis of leaf area index observations: implications for ecological and remote sensing studies

Cited by 739 publications

References 53 publications

A comment on the quantitative significance of aerobic methane release by plants

A comment on the quantitative significance of aerobic methane release by plants

Species composition and forest structure explain the temperature sensitivity patterns of productivity in temperate forests

Root zone salinity and sodicity under seasonal rainfall due to feedback of decreasing hydraulic conductivity

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