Leaf age affects the seasonal pattern of photosynthetic capacityand net ecosystem exchange of carbon in a deciduous forest

2001 ◽  
Vol 24 (6) ◽  
pp. 571-583 ◽  
Author(s):  
K. B. Wilson ◽  
D. D. Baldocchi ◽  
P. J. Hanson
2021 ◽  
Vol 301-302 ◽  
pp. 108351
Author(s):  
Suraj Reddy Rodda ◽  
Kiran Chand Thumaty ◽  
MSS Praveen ◽  
Chandra Shekhar Jha ◽  
Vinay Kumar Dadhwal

2020 ◽  
Author(s):  
Bertold Mariën ◽  
Inge Dox ◽  
Hans J. De Boeck ◽  
Patrick Willems ◽  
Sebastien Leys ◽  
...  

Abstract. Severe droughts are expected to become more frequent and persistent. However, their effect on autumn leaf senescence, a key process for deciduous trees and ecosystem functioning, is currently unclear. We hypothesized that (I) severe drought advances the onset of autumn leaf senescence in temperate deciduous trees and that (II) tree species show different dynamics of autumn leaf senescence under drought. We tested these hypotheses using a manipulative experiment on beech saplings and three years of monitoring mature beech, birch and oak trees in Belgium. The autumn leaf senescence was derived from the seasonal pattern of the chlorophyll content index and the loss of canopy greenness using generalized additive models and piece-wise linear regressions. Drought did not affect the onset of autumn leaf senescence in both saplings and mature trees, even if the saplings showed a high mortality and the mature trees a high leaf mortality (due to accelerated leaf senescence and early leaf abscission). We did not observe major differences among species. Synthesis: The timing of autumn leaf senescence appears conservative across years and species, and even independent on drought stress. Therefore, to study autumn senescence, seasonal chlorophyll dynamics and loss of canopy greenness should be considered separately.


2012 ◽  
Vol 5 (5) ◽  
pp. 1091-1108 ◽  
Author(s):  
M. De Weirdt ◽  
H. Verbeeck ◽  
F. Maignan ◽  
P. Peylin ◽  
B. Poulter ◽  
...  

Abstract. The influence of seasonal phenology on canopy photosynthesis in tropical evergreen forests remains poorly understood, and its representation in global ecosystem models is highly simplified, typically with no seasonal variation of canopy leaf properties taken into account. Including seasonal variation in leaf age and photosynthetic capacity could improve the correspondence of global vegetation model outputs with the wet–dry season CO2 patterns measured at flux tower sites in these forests. We introduced a leaf litterfall dynamics scheme in the global terrestrial ecosystem model ORCHIDEE based on seasonal variations in net primary production (NPP), resulting in higher leaf turnover in periods of high productivity. The modifications in the leaf litterfall scheme induce seasonal variation in leaf age distribution and photosynthetic capacity. We evaluated the results of the modification against seasonal patterns of three long-term in-situ leaf litterfall datasets of evergreen tropical forests in Panama, French Guiana and Brazil. In addition, we evaluated the impact of the model improvements on simulated latent heat (LE) and gross primary productivity (GPP) fluxes for the flux tower sites Guyaflux (French Guiana) and Tapajós (km 67, Brazil). The results show that the introduced seasonal leaf litterfall corresponds well with field inventory leaf litter data and times with its seasonality. Although the simulated litterfall improved substantially by the model modifications, the impact on the modelled fluxes remained limited. The seasonal pattern of GPP improved clearly for the Guyaflux site, but no significant improvement was obtained for the Tapajós site. The seasonal pattern of the modelled latent heat fluxes was hardly changed and remained consistent with the observed fluxes. We conclude that we introduced a realistic and generic litterfall dynamics scheme, but that other processes need to be improved in the model to achieve better simulations of GPP seasonal patterns for tropical evergreen forests.


2021 ◽  
Vol 18 (11) ◽  
pp. 3309-3330
Author(s):  
Bertold Mariën ◽  
Inge Dox ◽  
Hans J. De Boeck ◽  
Patrick Willems ◽  
Sebastien Leys ◽  
...  

Abstract. Severe droughts are expected to become more frequent and persistent. However, their effect on autumn leaf senescence, a key process for deciduous trees and ecosystem functioning, is currently unclear. We hypothesized that (I) severe drought advances the onset of autumn leaf senescence in temperate deciduous trees and (II) tree species show different dynamics of autumn leaf senescence under drought. We tested these hypotheses using a manipulative experiment on beech saplings and 3 years of monitoring mature beech, birch and oak trees in Belgium. The autumn leaf senescence was derived from the seasonal pattern of the chlorophyll content index and the loss of canopy greenness using generalized additive models and piecewise linear regressions. Drought and associated heat stress and increased atmospheric aridity did not affect the onset of autumn leaf senescence in both saplings and mature trees, even if the saplings showed a high mortality and the mature trees an advanced loss of canopy greenness. We did not observe major differences among species. To synthesize, the timing of autumn leaf senescence appears conservative across years and species and even independent of drought, heat and increased atmospheric aridity. Therefore, to study autumn senescence and avoid confusion among studies, seasonal chlorophyll dynamics and loss of canopy greenness should be considered separately.


2022 ◽  
Vol 314 ◽  
pp. 108786
Author(s):  
Dipankar Sarma ◽  
Pramit Kumar Deb Burman ◽  
S. Chakraborty ◽  
Nirmali Gogoi ◽  
Abhijit Bora ◽  
...  

2021 ◽  
Author(s):  
Aparnna Ravi P ◽  
Dhanyalekshmi K Pillai ◽  
Christoph Gerbig ◽  
Julia Marshall ◽  
Chandra Shekhar Jha

<p>Several countries across the world have initiated considerable efforts to curb Greenhouse Gas emissions to limit the increase in global temperature to 2°C. However, planning of proper emission reduction policies and their successful implementation require accurate carbon budgeting. The objective of this study is to accurately quantify various sources and sinks of carbon dioxide over Indian domain using inverse modelling techniques. </p><p>In order to better represent and quantify the atmosphere-biosphere CO<sub>2</sub> exchange fluxes and ecosystem behaviour in the inverse modeling framework, the Vegetation Photosynthesis and Respiration Model (VPRM) is employed over Indian region. VPRM is a satellite based assimilation scheme with very simple model structure, so as to facilitate successive optimization of parameters in the inverse modelling framework. As an initial step, we evaluated the VPRM model with eddy covariance observations over India from two different vegetation types (Betul; Deciduous forest and Sundarbans; Evergreen forest) for the year 2017. The comparison reveals that the model needs further refinement in parametrization even though the VPRM showed better performance than other existing terrestrial biosphere models (e.g ., TRENDY and Carbon Tracker (CT)) over Indian domain. Among the VPRM products (Net ecosystem exchange (NEE), Gross Primary Productivity (GPP), and Ecosystem Respiration (Re)), the ecosystem respiration shows large deviations from observation. The analysis, based on the soil moisture (SM) data from IITM monsoon mission project shows that the SM plays a significant role, which is currently missing in the VPRM respiration calculations. Further, the study attempts to utilize Solar induced Fluorescence (SIF) as a proxy to estimate GPP and to be included in VPRM for the better representation of biospheric fluxes over India. Preliminary results will be presented and discussed.</p>


2020 ◽  
Author(s):  
Zheng-Hong Tan ◽  
Fang-Jun Ding ◽  
Yan-Hui Liu ◽  
Peng Wu ◽  
Wen-Jun Zhao ◽  
...  

Abstract Masson pine (Pinus massoniana) is a tree species widely planted in central and south China. In the present pioneer study, we reported about our two years of carbon flux observations over an even-aged pure Masson pine stand. Light intensity could explain nearly half (47%) of the variance in daytime net ecosystem exchange (NEE). Daytime dark respiration was lower than nighttime NEE, suggesting a possible effect of light inhibition on respiration. The mean annual NEE was -557 g C m-2 yr-1, which indicated that this stand is a medium to large carbon sink. This NEE estimates were defensive because we checked the data with thorough quality controls and in consistency with previous independent estimates. An unexpected seasonal pattern of NEE was observed with a clear reduction around the transitional period between summer and autumn (around July). This NEE reduction is probably a consequence of water stress induced stomatal control, and not of a decrease in light intensity. The updated optimal stomatal theory did not provide the best description of stomatal control in relation to photosynthesis. Whether this is a new emergent property of the ecosystem scale needs further investigation.


Crisis ◽  
2014 ◽  
Vol 35 (1) ◽  
pp. 5-9 ◽  
Author(s):  
Daniel Hideki Bando ◽  
Fernando Madalena Volpe

Background: In light of the few reports from intertropical latitudes and their conflicting results, we aimed to replicate and update the investigation of seasonal patterns of suicide occurrences in the city of São Paulo, Brazil. Methods: Data relating to male and female suicides were extracted from the Mortality Information Enhancement Program (PRO-AIM), the official health statistics of the municipality of São Paulo. Seasonality was assessed by studying distribution of suicides over time using cosinor analyses. Results: There were 6,916 registered suicides (76.7% men), with an average of 39.0 ± 7.0 observed suicides per month. For the total sample and for both sexes, cosinor analysis estimated a significant seasonal pattern. For the total sample and for males suicide peaked in November (late spring) with a trough in May–June (late autumn). For females, the estimated peak occurred in January, and the trough in June–July. Conclusions: A seasonal pattern of suicides was found for both males and females, peaking in spring/summer and dipping in fall/winter. The scarcity of reports from intertropical latitudes warrants promoting more studies in this area.


2017 ◽  
Vol 28 (1-2) ◽  
pp. 28-35 ◽  
Author(s):  
B. A. Baranovski

Nowadays, bioecological characteristics of species are the basis for flora and vegetation studying on the different levels. Bioecological characteristics of species is required in process of flora studying on the different levels such as biotopes or phytocenoses, floras of particular areas (floras of ecologically homogeneous habitats), and floras of certain territories. Ramensky scale is the one of first detailed ecological scales on plant species ordination in relation to various environmental factors; it developed in 1938 (Ramensky, 1971). A little later (1941), Pogrebnyak’s scale of forest stands was proposed. Ellenberg’s system developed in 1950 (Ellenberg, 1979) and Tsyganov’s system (Tsyganov, 1975) are best known as the systems of ecological scales on vascular plant species; these systems represent of habitat detection by ecotopic ecomorphs of plant species (phytoindication). Basically, the system proposed by Alexander Lyutsianovich Belgard was the one of first system of plant species that identiified ectomorphs in relation to environmental factors. As early as 1950, Belgard developed the tabulated system of ecomorphs using the Latin ecomorphs abbreviation; he also used the terminology proposed in the late 19th century by Dekandol (1956) and Warming (1903), as well as terminology of other authors. The article analyzes the features of Belgard’s system of ecomorphs on vascular plants. It has certain significance and advantages over other systems of ecomorphs. The use of abbreviated Latin names of ecomorphs in tabular form enables the use shortened form of ones. In the working scheme of Belgard’s system of ecomorphs relation of species to environmental factors are represented in the abbreviated Latin alphabetic version (Belgard, 1950). Combined into table, the ecomorphic analysis of plant species within association (ecological certification of species), biotope or area site (water area) gives an explicit pattern on ecological structure of flora within surveyed community, biotope or landscape, and on environmental conditions. Development and application by Belgrard the cenomorphs as «species’ adaptation to phytocenosis as a whole» were completely new in the development of systems of ecomorphs and, in this connection, different coenomorphs were distinguished. Like any concept, the system of ecomorphs by Belgard has the possibility and necessity to be developed and added. Long-time researches and analysis of literature sources allow to propose a new coenomorph in the context of Belgard’s system of ecomorphs development: silvomargoant (species of forest margin, from the Latin words margo – edge, boundary (Dvoretsky, 1976), margo – margin, ad margins silvarum – along the deciduous forest margins). As an example of ecomorphic characterization of species according to the system of ecomorphs by Belgard (when the abbreviated Latin ecomorph names are used in tabular form and the proposed cenomorph is used), it was given the part of the table on vascular plants ecomorphs in the National Nature Park «Orelsky» (Baranovsky et al). The Belgard’s system of ecomorphs is particularly convenient and can be successfully applied to data processing in the ecological analysis of the flora on wide areas with significant species richness, and the proposed ecomorph will be another necessary element in the Belgard’s system of ecomorphs. 


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