Response of CO₂ and H₂O fluxes in a mountainous tropical rainforest in equatorial Indonesia to El Niño events

The possible impact of El Niño–Southern Oscillation (ENSO) events on the main components of CO₂ and H₂O fluxes between the tropical rainforest and the atmosphere is investigated. The fluxes were continuously measured in an old-growth mountainous tropical rainforest in Central Sulawesi in Indonesia using the eddy covariance method for the period from January 2004 to June 2008. During this period, two episodes of El Niño and one episode of La Niña were observed. All these ENSO episodes had moderate intensity and were of the central Pacific type. The temporal variability analysis of the main meteorological parameters and components of CO₂ and H₂O exchange showed a high sensitivity of evapotranspiration (ET) and gross primary production (GPP) of the tropical rainforest to meteorological variations caused by both El Niño and La Niña episodes. Incoming solar radiation is the main governing factor that is responsible for ET and GPP variability. Ecosystem respiration (RE) dynamics depend mainly on the air temperature changes and are almost insensitive to ENSO. Changes in precipitation due to moderate ENSO events did not have any notable effect on ET and GPP, mainly because of sufficient soil moisture conditions even in periods of an anomalous reduction in precipitation in the region

Implementing a new rubber plant functional type in the Community Land Model (CLM5) improves accuracy of carbon and water flux estimation

Rubber plantations are an economically viable land-use type that occupies large swathes of land in Southeast Asia that have undergone conversion from native forest to intensive plantation forestry. Such land-use change has a strong impact on carbon, energy, and water fluxes in ecosystems, and uncertainties exist in the modeling of future land-use change impacts on these fluxes due to the scarcity of measured data and poor representation of key biogeochemical processes. In this current modeling effort, we utilized the Community Land Model Version 5 (CLM5) to simulate a rubber plant functional type (PFT) by comparing the baseline parameter values of tropical evergreen PFT and tropical deciduous PFT with a newly developed rubber PFT (focused on the parameterization and modification of phenology and allocation processes) based on site-level observations of a rubber clone in Indonesia. We found that the baseline tropical evergreen and baseline tropical deciduous functions and parameterizations in CLM5 poorly simulate the leaf area index, carbon dynamics, and water fluxes of rubber plantations. The newly developed rubber PFT and parametrizations (CLM-rubber) showed that daylength could be used as a universal trigger for defoliation and refoliation of rubber plantations. CLM-rubber was able to predict seasonal patterns of latex yield reasonably well, despite highly variable tapping periods across Southeast Asia. Further, model comparisons indicated that CLM-rubber can simulate carbon and energy fluxes similar to the existing rubber model simulations available in the literature. Our modeling results indicate that CLM-rubber can be applied in Southeast Asia to examine variations in carbon and water fluxes for rubber plantations and assess how rubber-related land-use changes in the tropics feedback to climate through carbon and water cycling

Northern Eurasia Future Initiative (NEFI): facing the challenges and pathways of global change in the 21st century

During the past several decades, the Earth system has changed significantly, especially across Northern Eurasia. Changes in the socio-economic conditions of the larger countries in the region have also resulted in a variety of regional environmental changes that can have global consequences. The Northern Eurasia Future Initiative (NEFI) has been designed as an essential continuation of the Northern Eurasia Earth Science Partnership Initiative (NEESPI), which was launched in 2004. NEESPI sought to elucidate all aspects of ongoing environmental change, to inform societies and, thus, to better prepare societies for future developments. A key principle of NEFI is that these developments must now be secured through science-based strategies co-designed with regional decision makers to lead their societies to prosperity in the face of environmental and institutional challenges. NEESPI scientific research, data, and models have created a solid knowledge base to support the NEFI program. This paper presents the NEFI research vision consensus based on that knowledge. It provides the reader with samples of recent accomplishments in regional studies and formulates new NEFI science questions. To address these questions, nine research foci are identified and their selections are briefly justified. These foci include: warming of the Arctic; changing frequency, pattern, and intensity of extreme and inclement environmental conditions; retreat of the cryosphere; changes in terrestrial water cycles; changes in the biosphere; pressures on land-use; changes in infrastructure; societal actions in response to environmental change; and quantification of Northern Eurasia's role in the global Earth system. Powerful feedbacks between the Earth and human systems in Northern Eurasia (e.g., mega-fires, droughts, depletion of the cryosphere essential for water supply, retreat of sea ice) result from past and current human activities (e.g., large scale water withdrawals, land use and governance change) and potentially restrict or provide new opportunities for future human activities. Therefore, we propose that Integrated Assessment Models are needed as the final stage of global change assessment. The overarching goal of this NEFI modeling effort will enable evaluation of economic decisions in response to changing environmental conditions and justification of mitigation and adaptation efforts

Growing season variability of net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire in the broad-leaved forest zone of European Russia

The spatial and temporal variability of net ecosystem exchange (NEE) of CO _2 and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest–steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO _2 /H _2 O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO _2 for the atmosphere. NEE reached maximal values in June–July (−6.8 ± 4.2 μmol m ^−2  s ^−1 ). The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO _2 for the atmosphere in June–July only. ET reached maximal values in the well-lighted central parts of the mire in May (0.34 ± 0.20 mm h ^−1 ) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July–August from −1.1 ± 1.1 mgC g ^−1 of dry weight (DW) per hour in the peripheral zone of the mire to −0.6 ± 0.2 mgC g ^−1 DW h ^−1 at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center (0.25 ± 0.10 mm h ^−1 ) and the herbaceous species on the peripheral part of the mire (0.03 ± 0.03 mm h ^−1 )

Contribution of different plant groups and peat to GPP, RE and ET for the <em>Bet–Men–Sph</em> (plot 1) and <em>Rh–Cr–Sph</em> (plot 4) plant communities in the southern peripheral and central parts of the mire

<p><strong>Figure 4.</strong> Contribution of different plant groups and peat to GPP, RE and ET for the <em>Bet–Men–Sph</em> (plot 1) and <em>Rh–Cr–Sph</em> (plot 4) plant communities in the southern peripheral and central parts of the mire. The mean and SD (indicated by vertical whiskers) values were estimated from measurements at three sample points in the <em>Bet–Men–Sph</em> and four sample points in <em>Rh–Cr–Sph</em> plant communities.</p> <p><strong>Abstract</strong></p> <p>The spatial and temporal variability of net ecosystem exchange (NEE) of CO₂ and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest–steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO₂/H₂O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO₂ for the atmosphere. NEE reached maximal values in June–July (−6.8 ± 4.2 μmol m⁻² s⁻¹). The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO₂ for the atmosphere in June–July only. ET reached maximal values in the well-lighted central parts of the mire in May (0.34 ± 0.20 mm h⁻¹) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July–August from −1.1 ± 1.1 mgC g⁻¹ of dry weight (DW) per hour in the peripheral zone of the mire to −0.6 ± 0.2 mgC g⁻¹ DW h⁻¹ at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center (0.25 ± 0.10 mm h⁻¹) and the herbaceous species on the peripheral part of the mire (0.03 ± 0.03 mm h⁻¹).</p

General scheme of plant community pattern within the sphagnum mire 'Glavnoe'

<p><strong>Figure 2.</strong> General scheme of plant community pattern within the sphagnum mire 'Glavnoe'. Legend: 1—<em>Filipendula ulmaria</em>; 2—herbal; 3—<em>Thelypteris palustris</em>—<em>Carex rostrata</em>; 4—<em>Thelypteris palustris</em>; 5—willow—herbal (with <em>Salix cinerea</em>); 6—<em>Betula pubescens</em>—<em>Menyanthes trifoliata</em> – <em>Sphagnum riparium</em>; 7—<em>Betula pubescens</em>—<em>Carex rostrata</em> – <em>Sphagnum fallax</em>; 8—<em>Rhynchospora alba</em> – <em>Carex rostrata</em>—<em>Sphagnum magellanicum</em> + <em>S. angustifolium</em>; 9—measuring plots (P1–P5).</p> <p><strong>Abstract</strong></p> <p>The spatial and temporal variability of net ecosystem exchange (NEE) of CO₂ and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest–steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO₂/H₂O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO₂ for the atmosphere. NEE reached maximal values in June–July (−6.8 ± 4.2 μmol m⁻² s⁻¹). The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO₂ for the atmosphere in June–July only. ET reached maximal values in the well-lighted central parts of the mire in May (0.34 ± 0.20 mm h⁻¹) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July–August from −1.1 ± 1.1 mgC g⁻¹ of dry weight (DW) per hour in the peripheral zone of the mire to −0.6 ± 0.2 mgC g⁻¹ DW h⁻¹ at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center (0.25 ± 0.10 mm h⁻¹) and the herbaceous species on the peripheral part of the mire (0.03 ± 0.03 mm h⁻¹).</p

An Inverse Modeling Approach for Retrieving High-Resolution Surface Fluxes of Greenhouse Gases from Measurements of Their Concentrations in the Atmospheric Boundary Layer

This study explores the potential of using Unmanned Aircraft Vehicles (UAVs) as a measurement platform for estimating greenhouse gas (GHG) fluxes over complex terrain. We proposed and tested an inverse modeling approach for retrieving GHG fluxes based on two-level measurements of GHG concentrations and airflow properties over complex terrain with high spatial resolution. Our approach is based on a three-dimensional hydrodynamic model capable of determining the airflow parameters that affect the spatial distribution of GHG concentrations within the atmospheric boundary layer. The model is primarily designed to solve the forward problem of calculating the steady-state distribution of GHG concentrations and fluxes at different levels over an inhomogeneous land surface within the model domain. The inverse problem deals with determining the unknown surface GHG fluxes by minimizing the difference between measured and modeled GHG concentrations at two selected levels above the land surface. Several numerical experiments were conducted using surrogate data that mimicked UAV observations of varying accuracies and density of GHG concentration measurements to test the robustness of the approach. Our primary modeling target was a 6 km2 forested area in the foothills of the Greater Caucasus Mountains in Russia, characterized by complex topography and mosaic vegetation. The numerical experiments show that the proposed inverse modeling approach can effectively solve the inverse problem, with the resulting flux distribution having the same spatial pattern as the required flux. However, the approach tends to overestimate the mean value of the required flux over the domain, with the maximum errors in flux estimation associated with areas of maximum steepness in the surface topography. The accuracy of flux estimates improves as the number of points and the accuracy of the concentration measurements increase. Therefore, the density of UAV measurements should be adjusted according to the complexity of the terrain to improve the accuracy of the modeling results

Map of vegetation zones in central European Russia and the geographical location of the experimental site (marked by a white square)

<p><strong>Figure 1.</strong> Map of vegetation zones in central European Russia and the geographical location of the experimental site (marked by a white square). Legend: 1—southern taiga, 2—coniferous and broad-leaved forest zone, 3—broad-leaved forest zone, 4—forest–steppe zone, 5—steppe zone.</p> <p><strong>Abstract</strong></p> <p>The spatial and temporal variability of net ecosystem exchange (NEE) of CO₂ and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest–steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO₂/H₂O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO₂ for the atmosphere. NEE reached maximal values in June–July (−6.8 ± 4.2 μmol m⁻² s⁻¹). The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO₂ for the atmosphere in June–July only. ET reached maximal values in the well-lighted central parts of the mire in May (0.34 ± 0.20 mm h⁻¹) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July–August from −1.1 ± 1.1 mgC g⁻¹ of dry weight (DW) per hour in the peripheral zone of the mire to −0.6 ± 0.2 mgC g⁻¹ DW h⁻¹ at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center (0.25 ± 0.10 mm h⁻¹) and the herbaceous species on the peripheral part of the mire (0.03 ± 0.03 mm h⁻¹).</p

Quantification Of Leaf Emissivities Of Forest Species: Effects On Modelled Energy And Matter Fluxes In Forest Ecosystems

Climate  change  has distinct regional and local differences in its impacts on the land sur face. One of the important parameters determining the climate change signal is the emissivity (ε) of the sur face. In forest-climate interactions, the leaf sur face emissivity plays a decisive   role.  The accurate  determination  of leaf emissivities  is crucial for  the appropriate  interpretation  of measured  energy and matter fluxes between the forest and the atmosphere. In this study, we quantified the emissivity of the five broadleaf tree species Acer pseudoplatanus, Fagus sylvatica, Fraxinus excelsior, Populus simonii and Populus candicans. Measurements of leaf sur face temperatures were conducted under laboratory conditions in a controlled-climate chamber within the temperature range of +8 °C and +32°C. Based on these measurements, broadband  leaf emissivities ε (ε for the spectral range of 8-14 µm) were calculated. Average ε8-14 µm was 0.958±0.002 for all species with very little variation among species. In a second step, the soil-vegetation-atmosphere  transfer model ‘MixFor-SVAT ’ was applied to examine the effects of ε changes on radiative, sensible and latent energy  fluxes of the Hainich  forest in Central Germany.  Model experiments  were driven by meteorological data measured at the Hainich  site. The simulations  were  forced with the calculated ε value as well as with minimum and maximum values obtained from the literature.  Significant  effects  of ε changes were detected.  The strongest  effect was identified for the sensible heat flux with a sensitivity of 20.7 % per 1 % ε change. Thus, the variability of ε should be considered in climate change studies