Carbon Storage In Pools Research Articles

Using demographic modeling to develop post‐fire restoration strategies for a native shrub in a sage scrub community

Mediterranean‐climate shrublands are key biodiversity hotspots and carbon storage pools, but are increasingly threatened by climate change, non‐native species, and altered fire regimes. Fires are important to historic shrubland disturbance cycles but can also promote non‐native plants, which may limit post‐fire native shrub recovery. Increasing drought with climate change could also reduce post‐fire shrub regeneration. I developed a stochastic, individual‐based demographic model (IBM) for the native shrub Artemisia californica, parameterized from an experimental removal of non‐native annuals after a 2013 fire in southern California. The IBM simulated A. californica recovery for 7 years after fire under different rainfall conditions (drought or pre‐drought) and non‐native removal strategies (from no years to all 7 years). Drought lowered A. californica canopy volume 7 years after fire by 90% or more. Rainfall in the second year after fire, when most A. californica germination occurred, had particularly strong effects on final canopy cover. Non‐native removal in all 7 years increased canopy volume by three times under drought conditions and 3.5 times under pre‐drought conditions. Targeting non‐native removal in the first 2 years proved nearly as effective, achieving from 88% (drought) to 95% (pre‐drought) the benefits of removal in all 7 years. In sum, low rainfall may be the most important limitation on post‐fire shrub recovery, but removal of non‐natives in years of pulsed shrub recruitment can be an effective restoration strategy even under drought conditions. More generally, this study illustrates how demographic models can help optimize the targeting of scarce management and restoration resources.

Carbon storage and carbon pool characteristics of Larix gmelinii forest in Daxing’anling, Inner Mongolia, China

Carbon storage and carbon pool characteristics of Larix gmelinii forest in Daxing’anling, Inner Mongolia, China

Carbon Storage Potential of Soil in Diverse Terrestrial Ecosystems

Soil is one of the largest carbon reservoirs sequestering more carbon than vegetation and atmosphere. Due to the enormous potential of soil to sequester atmospheric CO2, it becomes a feasible option to alleviate the current and impending effects of changing climate. Soil is a vulnerable resource globally because it is highly susceptible to global environmental problems such as land degradation, biodiversity loss, and climate change. Therefore, protecting and monitoring worldwide soil carbon pools is a complicated challenge. Soil organic carbon (SOC) is a vital factor affecting soil health since it is a major component of SOM and contributes to food production. This review attempts to summarize the information on carbon sequestration, storage, and carbon pools in the major terrestrial ecosystems and underpin soil carbon responses under climate change and mitigation strategies. Topography, pedogenic, and climatic factors mainly affect carbon input and stabilization. Humid conditions and low temperature favor high soil organic carbon content. Whereas warmer and drier regions have low SOC stocks. Tropical peatlands and mangrove ecosystems have the highest SOC stock. The soil of drylands stores 95% of the global Soil Inorganic Carbon (SIC) stock. Grasslands include rangelands, shrublands, pasturelands, and croplands. They hold about 1/5th of the world’s total soil carbon stocks.

Air-sea carbon dioxide equilibrium: Will it be possible to use seaweeds for carbon removal offsets?

To limit global warming below 2°C by 2100, we must drastically reduce greenhouse gas emissions and additionally remove ~100-900 Gt CO2 from the atmosphere (carbon dioxide removal, CDR) to compensate for unavoidable emissions. Seaweeds (marine macroalgae) naturally grow in coastal regions worldwide where they are crucial for primary production and carbon cycling. They are being considered as a biological method for CDR and for use in carbon trading schemes as offsets. To use seaweeds in carbon trading schemes requires verification that seaweed photosynthesis that fixes CO2 into organic carbon results in CDR, along with the safe and secure storage of the carbon removed from the atmosphere for more than 100 years (sequestration). There is much ongoing research into the magnitude of seaweed carbon storage pools (e.g., as living biomass and as particulate and dissolved organic carbon in sediments and the deep ocean), but these pools do not equate to CDR unless the amount of CO2 removed from the atmosphere as a result of seaweed primary production can be quantified and verified. The draw-down of atmospheric CO2 into seawater is via air-sea CO2 equilibrium, which operates on time scales of weeks to years depending upon the ecosystem considered. Here, we explain why quantifying air-sea CO2 equilibrium and linking this process to seaweed carbon storage pools is the critical step needed to verify CDR by discrete seaweed beds and nearshore and open ocean aquaculture systems prior to their use in carbon trading.

Pool dynamics of time-dependent compartmental systems with application to the terrestrial carbon cycle.

Compartmental models play an important role to describe the dynamics of systems that involve mass movements between different types of pools. We develop a theory to analyse the average ages of mass in different pools in a linear compartmental system with time-dependent (i.e. non-autonomous) transfer rates, which involves transit times that characterize the average time a particle has spent in a particular pool. We apply our theoretical results to investigate a nine-dimensional compartmental system with time-dependent fluxes between pools modelling the carbon cycle which is a modification of the Carnegie-Ames-Stanford approach model. Knowledge of transit time and mean age allows calculation of carbon storage in a pool as a function of time. The general result that has important implications for understanding and managing carbon storage is that the change in storage in different pools does not change monotonically through time: as rates change monotonically a pool which initially shows a decrease may then show an increase in storage or vice versa. Thus caution is needed in extrapolating even the direction of future changes in storage in carbon storage in different pools with global change.

Carbon flux variation and associated biomass energy storage economic value implications in the Dinghushan Biosphere Reserve

Subtropical forests are a major carbon (C) storage pool and are therefore rich in biomass energy reservoirs. However, there have been no studies that quantify the C storage economic value, especially in the region of the Dinghushan Biosphere Reserve. This study is the first attempt to apply the eddy covariance technique to measure biomass energy storage and the associated economic value and demonstrates that CO2 flux measurement is a viable method for quantifying the ecosystem biomass energy storage. CO2 flux and micro-meteorological data were collected and analyzed to calculate the daily C sequestration and establish their inter-relationship. In addition, we used the C price estimates of Guangdong Province in China to determine the capital value of the C sequestered. The measured average annual precipitation was 1459.4 mm, the average temperature was 22.9 °C and the highest photosynthetic photon flux density (PPFD) was 334.92 μmol m−2s−1. CO2 flux and biomass energy storage varied seasonally. Photosynthetic photon flux density (PPFD) was highly correlated with gross primary production (GPP) (r2 = 0.99, p < 0.0001). Soil temperature was correlated with net ecosystem exchange (NEE) (r2 = 0.84, p < 0.0001). There was a positive correlation (r2 = 0.49, p < 0.0001) between soil moisture and NEE. The Dinghushan Biosphere Reserve sequestered an average of 5300 tCy−1 equivalent to RMB 3.3 million (USD 530,000). We conclude that economically, the Dinghushan Biosphere Reserve is highly significant to China's Guangdong Province because of its rich biomass energy reserves via C sequestration and our findings will stimulate the formulation of more aggressive conservation policies that will inevitably lead to better management of the reserve.

Influence of Crops and Different Production Systems on Soil Carbon Fractions and Carbon Sequestration in Rainfed Areas of Semiarid Tropics in India

Organic agriculture’s economic benefits and widespread adoption are well documented, but its impact on soil C dynamics in rainfed regions of semiarid tropics is less understood. The use of organic amendments in organic farming not only supply nutrients but also have the potential to contribute to soil carbon sequestration. Carbon storage and various soil organic pools are affected differently by various crops and production systems. A study was conducted with three crops (sunflower, pigeonpea, and greengram) under three production systems (control, organic and integrated) to assess the effect on soil C stocks, carbon sequestration potential, and crop yield. After seven years of experiment, pigeonpea (Cajanus cajan L.) cultivation improved soil bulk density, porosity and water holding capacity compared to greengram [Vigna radiata (L) Wilczek] and sunflower (Helianthus annuus L.). Furthermore, plots under pigeonpea cultivation being on par with greengram had 15.6% higher total C (113.52 Mg C ha−1), 14% higher easily oxidizable organic C (17.5 Mg C ha−1) and C sequestration rate of 1.22 Mg C ha−1 yr−1 compared to sunflower. Among the three production systems, plots under organic management had significantly lower bulk density and higher water holding capacity and porosity at all of the profile depths compared to integrated production system and control. Similarly, organic production system being on par with integrated production system improved the easily oxidizable, oxidizable and weakly oxidizable organic C fractions at different soil depths compared to control. The C sequestration rate ranged from 0.21 to 0.85 Mg C ha−1 yr−1 in organic production systems compared to negligible rate (0.01–0.04 Mg ha−1 yr−1) in the plots under control. On average, integrated production system being on par with organic management recorded significantly higher pigeonpea equivalent seed yield (886 kg ha−1) compared to control (792 kg ha−1). These results suggest the potential of organic production system in improving soil properties, C sequestration, and crop yields in semiarid rainfed areas.

Rubisco regulation in response to altered carbon status in the cyanobacterium Synechococcus elongatus PCC 7942.

Photosynthetic organisms possess a variety of mechanisms to achieve balance between absorbed light (source) and the capacity to metabolically utilize or dissipate this energy (sink). While regulatory processes that detect changes in metabolic status/balance are relatively well studied in plants, analogous pathways remain poorly characterized in photosynthetic microbes. Here, we explored systemic changes that result from alterations in carbon availability in the model cyanobacterium Synechococcus elongatus PCC 7942 by taking advantage of an engineered strain where influx/efflux of a central carbon metabolite, sucrose, can be regulated experimentally. We observed that induction of a high-flux sucrose export pathway leads to depletion of internal carbon storage pools (glycogen) and concurrent increases in estimates of photosynthetic activity. Further, a proteome-wide analysis and fluorescence reporter-based analysis revealed that upregulated factors following the activation of the metabolic sink are concentrated on ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) and auxiliary modules involved in Rubisco maturation. Carboxysome number and Rubisco activity also increased following engagement of sucrose secretion. Conversely, reversing the flux of sucrose by feeding exogenous sucrose through the heterologous transporter resulted in increased glycogen pools, decreased Rubisco abundance, and carboxysome reorganization. Our data suggest that Rubisco activity and organization are key variables connected to regulatory pathways involved in metabolic balancing in cyanobacteria.

Impacts of Climate Change on Mycorrhizal Fungi in Salt Marsh Habitats

Salt marshes are coastal wetlands that cover 2-3% of land surface area.1 These habitats carry out several essential functions such as providing habitats for many species, acting as a buffer between terrestrial land and ocean waters, and most importantly, acting as a major carbon (C) storage pool. Arbuscular mycorrhizal fungal (AMF) symbionts are key organisms in salt marsh habitats and are known to influence the following: plant zonation, plant resource competition, plant productivity, plant genetic diversity, soil C sequestration, soil C:N:P ratios, saprotrophic bacterial population and diversity, soil stability, and litter decomposition. Under rapidly changing conditions caused by climate change it is difficult to predict how AMF communities will respond to these factors, which would ultimately alter those processes. In this review, we will outline the functions and roles that AMF communities play in salt marsh soils. Additionally, we will present current knowledge and predictions of how AMF will respond to rising sea levels, elevated CO₂ levels, and eutrophication. Lastly, we will outline our research design and methods which aims to identify soil fungal diversity and abundance in different grass patches. We will also look at several factors that potentially alter soil fungi such as edge-effects, elevation gradients, patch size, soil conductivity, pH, and soil stoichiometry. Studying soil fungi is essential for understanding how these communities are predicted to react to a changing climate, and consequently alter salt marsh processes.

Impact of Ex-Closure in above and below Ground Carbon Stock Biomass

Globally, there is a serious issue in carbon stock due to high deforestation and the loss of land, limited carbon storage pools in aboveground and underground forests in different regions, and increased carbon emissions to the atmosphere. This review paper highlights the impact of exclosures on above and below ground carbon stocks in biomass as a solution to globally curb carbon emissions. The data has been analyzed dependent on the Intergovernmental Panel on Climate Change (IPCC) guidelines, the Food and Agriculture Organization (FAO) Forest Resource Assessment report (FRA, 2020), and scientific journal publications mostly from the last decade, to show the research results of carbon stock and the impact of exclosures, particularly the challenges of deforestation and erosion of land and opportunities of area exclosures to provide a general outlook for policymakers. Overall, the world’s forest regions are declining, and although the forest loss rate has slowed, it has still not stopped sufficiently because the knowledge and practice of exclosures are limited. The global forest loss and carbon stock have decreased from 7.8 million ha/yr to 4.7 million ha/yr and from 668 gigatons to 662 gigatons respectively due to multiple factors that differ across the regions. However, a move toward natural rehabilitation and exclosures to reduce the emissions of Greenhouse Gas (GHGs) is needed. In the global production of carbon, the exclosure of forests plays an important role, in particular for permanent sinks of carbon.

Characteristics of carbon emissions in cotton fields under mulched drip irrigation

As the second carbon storage pool, soil is easily influenced by human activities. Mulched drip irrigation is a water-saving irrigation technique used widely in arid and semi-arid regions. However, information about the response of CO2 exchange to mulched drip irrigation, such as the wetter and warmer soil, is limited. To identify the carbon emissions effects of mulched drip irrigation, we carried out a field experiment using drip irrigation with and without clear plastic mulching during the cotton growing seasons of 2015 and 2016. We monitored the temporal and spatial variation of soil moisture, soil temperature, cotton growth stage, biomass, lint yield, CO2 emissions, and the relationship between soil respiration rate and soil climate. The results showed that plastic mulching drip irrigation increased soil moisture and soil temperature, especially during the early and middle growth stages of cotton. The soil respiration rate was related positively to the higher soil temperature and moisture conditions promoted by plastic film mulching, although the coefficients of determination were low (R2 were 0.480 and 0.205, corresponding p-value was both 0.000, respectively). The highest value of soil respiration was obtained within the narrow rows under the drip tape, regardless of the practice of mulching or not. The soil respiration rate under plastic mulch in the narrow and wide rows were on average 28.35 % and 22.48 % higher than non-mulched control. Meanwhile, the amount of total CO2 emissions was significantly increased by 25.34 % and 28.90 % in these same rows, respectively (p-values were 0.006 at narrow rows and 0.010 at wide rows in the first year, and 0.000 at same rows in the second year). The differences of CO2 emission in the bare soil was not significant between mulched plots and non-mulched control (p-values were 0.757 and 0.918 in the first and second growing seasons, respectively). In addition, plastic mulching significantly improved the biomass and yield of cotton, by 61.49 % and 12.83 % on average (p-values were 0.034 and 0.039 in 2015, 0.024 and 0.032 in 2016), respectively. The results indicate that the application of drip irrigation under plastic mulch could increase soil water content and temperature, promote cotton growth, and improve lint yield. However, it may also lead to increased CO2 emissions, which can intensify the warming of the climate.

Impacts of Land Cover Changes on Ecosystem Carbon Stocks Over the Transboundary Tumen River Basin in Northeast Asia

Understanding the effects of land cover changes on ecosystem carbon stocks is essential for ecosystem management and environmental protection, particularly in the transboundary region that has undergone marked changes. This study aimed to examine the impacts of land cover changes on ecosystem carbon stocks in the transboundary Tumen River Basin (TTRB). We extracted the spatial information from Landsat Thematic Imager (TM) and Operational Land Imager (OLI) images for the years 1990 and 2015 and obtained convincing estimates of terrestrial biomass and soil carbon stocks with the InVEST model. The results showed that forestland, cropland and built-up land increased by 57.5, 429.7 and 128.9 km2, respectively, while grassland, wetland and barren land declined by 24.9, 548.0 and 43.0 km2, respectively in the TTRB from 1990 to 2015. The total carbon stocks encompassing aboveground, belowground, soil and litter layer carbon storage pools have declined from 831.48 Tg C in 1990 to 831.42 Tg C in 2015 due to land cover changes. In detail, the carbon stocks decreased by 3.13 Tg C and 0.44 Tg C in Democratic People’s Republic of Korea (North Korea) and Russia, respectively, while increased by 3.51 Tg C in China. Furthermore, economic development, and national policy accounted for most land cover changes in the TTRB. Our results imply that effective wetland and forestland protection policies among China, North Korea, and Russia are much needed for protecting the natural resources, promoting local ecosystem services and regional sustainable development in the transnational area.

Do Steviol Glycosides Act Either as a Carbon Storage Pool or in Osmoregulation within Leaves of Stevia rebaudiana?

Steviol glycosides (SG) (with stevioside and rebaudioside A predominating) are present in wild-type Stevia rebaudiana, at approximately 10% of dry weight (dw), prompting a consideration of the autoecological role played by these compounds in terms of energy (C) storage and/or osmoregulation. The leaf starch pool was observed to change diurnally with respect to the light cycle (from 3.29% to 0.73% of leaf dw between dusk and dawn) and also to increase under constant light treatment (from 1.53% to 6.25% of leaf dw), while SG pools were relatively constant (around 6% w/dw). A similar trend was observed during exposure to elevated CO2 (800 ppm), with starch increasing (from 10% to 15% of leaf dw), while SG pool size was constant (around 12% w/dw). For plants subject to increasing water stress over several days, an increase in leaf sap osmolality was observed in the leaves of a severely stressed group (from -1 MPa to -3 MPa, after 2 days of treatment), while stevioside and rebaudioside A leaf concentration was relatively constant (around 16% w/dw). These results are not consistent with a role for SG as either a short-term C store or osmoregulator in S. rebaudiana.

Leaf Amino Acid Supply Affects Photosynthetic and Plant Nitrogen Use Efficiency under Nitrogen Stress.

The coordinated distribution of nitrogen to source leaves and sinks is essential for supporting leaf metabolism while also supplying sufficient nitrogen to seeds for development. This study aimed to understand how regulated amino acid allocation to leaves affects photosynthesis and overall plant nitrogen use efficiency in Arabidopsis (Arabidopsis thaliana) and how soil nitrogen availability influences these processes. Arabidopsis plants with a knockout of AAP2, encoding an amino acid permease involved in xylem-to-phloem transfer of root-derived amino acids, were grown in low-, moderate-, and high-nitrogen environments. We analyzed nitrogen allocation to shoot tissues, photosynthesis, and photosynthetic and plant nitrogen use efficiency in these knockout plants. Our results demonstrate that, independent of nitrogen conditions, aap2 plants allocate more nitrogen to leaves than wild-type plants. Increased leaf nitrogen supply positively affected chlorophyll and Rubisco levels, photosynthetic nitrogen use efficiency, and carbon assimilation and transport to sinks. The aap2 plants outperformed wild-type plants with respect to growth, seed yield and carbon storage pools, and nitrogen use efficiency in both high and deficient nitrogen environments. Overall, this study demonstrates that increasing nitrogen allocation to leaves represents an effective strategy for improving carbon fixation and photosynthetic nitrogen use efficiency. The results indicate that an optimized coordination of nitrogen and carbon partitioning processes is critical for high oilseed production in Arabidopsis, including in plants exposed to limiting nitrogen conditions.

Characteristics of Chromophoric Dissolved Organic Matter (CDOM) in Rivers of Western Sichuan Plateau Based on EEM-PARAFAC Analysis

Alpine meadows and wetlands of western Sichuan plateau are essential organic carbon pools for Tibetan plateau; thus, a thorough understanding of the characteristics of dissolved organic carbon (DOC) and its association with soil carbon storage pool helps to reveal the flux and intensity of DOC export in the area. Surface water samples were collected from three rivers (the upper reaches of Min River, Zagunao River, and Fubian River) in the alpine-gorge region and Bai River in the plateau planation surface distributed among the watersheds in western Sichuan plateau, Southwest China. UV absorbance and EEM fluorescence spectroscopy with parallel factor analysis (PARAFAC) was used to characterize chromophoric dissolved organic matter (CDOM). PARAFAC produced a three-component model:C1(260/480) and C2(310/420) represented terrestrial humic-like fluorophores, and C3(280/370) belonged to tyrosine-like substances. The total fluorescence intensity of CDOM in the alpine-gorge region showed fewer changes along the rivers and was lower than that of the Bai River in the hilly plateau. The Bai River had much higher concentrations of humic-like substances (C1,C2) compared to the other three rivers, indicating its terrestrial sources with high humification degree originated from meadows and watersheds along the river. The calculated fluorescence indices (FI, BIX, HIX, β:α) showed that CDOM in the alpine-gorge region was a mixture with both autochthonous and allochthonous origins with low humification degree, while CDOM in the plateau planation surface had a higher degree of humification and lower extent of degradation. Statistical analysis showed that the C1 and C2 components in four rivers were significantly positively correlated, and C1, C2 and C3 components in Bai River were significantly positively correlated. β:α and BIX were significantly positively correlated in four rivers, but there was no significant correlation between DOC and CDOM[a(355)].

Changes in the accumulation of alkenones and lipids under nitrogen limitation and its relation to other energy storage metabolites in the haptophyte alga Emiliania huxleyi CCMP 2090

Alkenones are long-chain methyl/ethyl ketones (mainly in length of C37-C39) with two to four trans-unsaturated bonds produced by several kinds of marine haptophytes such as Emiliania huxleyi (coccolithophore). The physiological functions and metabolic profile of alkenones are not well known yet. In this study, we focused on elucidating how alkenones contribute to energy storage and cellular carbon partitioning in relation to other cellular components. For the purpose, we analyzed the changes in carbon allocation among various cell components like lipids, alkenones, proteins, and polysaccharides between cells exposed to N-sufficient (+N) and N-limited conditions (−N) in E. huxleyi CCMP 2090. Finally, the alkenones were found to function as main storage lipids and their accumulation was clearly increased by −N, whereas triacylglycerols (TAGs) were barely detected under any N conditions. The mobilization of carbons into alkenones was stimulated by −N from 15% under +N to 27% under −N. However, photosynthetic C allocation into other components was suppressed by −N, showing that percent C allocation into fatty acids, proteins, and polysaccharides was decreased from 9, 46, and 6.8% under +N to 7, 25, and 4.5% under −N, respectively. In addition, fatty acids such as 16:0, 18:0, 18:1, and 18:2 became dominant under −N while 18:5 became dominant under +N conditions, with no significant change in 22:6. This study revealed that alkenones function as primary carbon storage pools especially under −N condition in E. huxleyi CCMP 2090 and that N supply triggers a dynamic change in carbon metabolism by modifying membrane lipid composition and regulating carbon allocation preferences.

Recovery following defoliation involves shifts in allocation that favour storage and reproduction over radial growth in black oak

SummaryCarbon allocation to growth, storage, reproduction and the effects of stress and disturbances on these processes remain poorly understood in trees. Non‐structural carbohydrates (NSC) are an important component of the carbon storage pool and are commonly used to assess whether tree growth under various conditions is carbon limited. Carbon limitation is generally assumed to result in reducedNSClevels and allocation, but changes in allocation priorities that favourNSCstorage could also limit carbon available for growth.We defoliated six mature oak trees in June 2010 and explored how defoliation affects the relationship between radial growth and netNSCstorage, estimated by the seasonal increase inNSCconcentration, for several years. We interpret our results in the context of a conceptual model of allocation – developed here – to help understand how allocation changed following defoliation. We also monitored flower and acorn production in 2011, as changes in reproduction could also affect allocation to growth and storage.Defoliation reduced radial growth for 3 years. Stemwood starch levels and storage were also generally reduced, although not as consistently as growth. In contrast, root collarNSCstorage was significantly greater in defoliated trees, allowing below‐ground stores to recover to control levels by November 2011. Defoliation had mixed effects on reproduction in 2011: production of second‐year acorns (initiated before defoliation) was not significantly affected, but there was complete cessation of flower production. Defoliation also changed the relationship betweenNSCallocation and growth in the 2 years following defoliation, indicating a shift in allocation favouring storage.According to our conceptual model, the positive relationship between growth andNSCallocation indicates that the allocation shifts occurred under carbon‐limiting conditions. We, therefore, propose that growth can be carbon limited by two different means: (i) a decrease in plant carbon availability and (ii) allocation shifts that reduce the priority of growth relative to other processes such as storage. Prioritizing storage over both growth and reproduction may be a strategy to protect against further disturbance or stress following storage depletion.Synthesis. Recovery following defoliation can involve substantial shifts in how trees allocate carbon between different functions, with carbohydrate storage and already initiated reproduction cycles being favoured relative to growth and new reproductive cycles.

Soil CO2 Emissions and Drivers in Rice–Wheat Rotation Fields Subjected to Different Long‐Term Fertilization Practices

Soil CO2 emissions are key components of global carbon cycling. Hence, knowledge of their drivers is important for estimating, and modifying, carbon storage pools. To extend knowledge of these drivers, results of a long‐term (31‐year) experiment in a rice–wheat rotation field in subtropical Central China were analyzed to determine effects on soil CO2 flux (FCO2) of various fertilization practices and related environmental factors including soil organic matter (SOM), microbial biomass carbon (MBC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK) contents; activities of three soil enzymes (acid phosphatase, urease, and catalase); and soil temperature, pH, cation exchange capacity (CEC), bulk density and porosity. The results clearly show that FCO2 was sensitive to changes in soil nutrient conditions under different long‐term fertilization practices. Notably, it was significantly higher in plots receiving organic manure applications than in those receiving only chemical fertilizers (N, NP, and NPK) and unfertilized plots. Correlation analysis showed that FCO2 was significantly correlated with the soil's SOM, TN, TP, and MBC contents, acid phosphatase and urease activities, and several physicochemical soil properties including pH, CEC, bulk density and porosity. However, no significant correlations were observed between FCO2 and either TK content or catalase activity. The findings suggest that at given temperature and soil moisture contents, variations in soil CO2 emissions associated with the fertilization practices are strongly related to SOM, and the nutrient contents, microbial and enzyme activities, and physicochemical properties of the soil.

Enhancing Ecosystem Function through Conservation: Threatened Plants Increase Local Carbon Storage in Tropical Dry Forests

The role of plant diversity, particularly of rare species, in ecosystem functioning ( e.g., carbon storage) has been mostly studied in temperate systems with little practical application to the conservation of tropical forests, where species rarity and species richness tend to be greater and more important for ecosystem functioning. We linked carbon storage pools with functional plant diversity, occurrence of rare species, and environmental (topographic) gradients in a species-rich seasonally dry tropical forest protected as a part of a Biosphere Reserve in northwestern Mexico. We estimated various functional diversity and carbon pool measures from in situ plant community and soil data. Soil and total ecosystem carbon storage decreased with slope steepness but increased with plant height. Above-ground carbon was negatively associated with elevation. Our data suggest that species identity matters to the functioning and productivity of seasonally dry tropical forests. Two long-lived and highly threatened rare plant species contributed considerably (10-20%) to the above-ground carbon storage pool. The functional roles of threatened plant species should be investigated and incorporated into the management plans of Biospheres Reserves and other closely coupled natural-human systems, where conservation plays a significant role in ecosystem functioning and human well-being.

Stomatal conductance and intrinsic water use efficiency in the drought year 2003: a case study of European beech

Beech trees were able to cope with the drought of 2003. Harmful water shortage has been avoided by an effective stomatal closure while use of carbon storage pools may have prevented carbon starvation and growth reduction. We applied hydrodynamic modeling together with a tree ring stable isotope approach to identify the physiological responses of beech trees to changing environmental conditions. The drought conditions of the extreme hot and dry summer in 2003 were hypothesized to significantly influence the radial growth of European beech mainly triggered by the stomatal response towards water scarcity leading, in turn, to a decline in carbon assimilation. The functional–structural single tree modeling approach applied, revealed in fact a strong limitation of water use and carbon gain during drought. However, tree ring width data did not show a clear drought response and no differentiation in radial growth during six subsequent years examined (2002–2007) has been observed. Using integrated results from mechanistic carbon–water balance simulations, tree ring carbon and oxygen isotope analysis and tree ring width measurements we postulate that the suggested drought-induced growth decline has been prevented by the remobilization of stored carbohydrates, an early onset in growth and the relatively late occurrence of the severe drought in 2003. Furthermore, we demonstrate that the stomatal response played a significant role in avoiding harmful water tension that would have caused xylem dysfunction. As a result of the combined investigation with physiological measurements (stable isotope approach) and hydrodynamic modeling of stomatal aperture, we could give insights into the physiological control of mature beech tree functioning under drought. We conclude that beech trees have been operating at their hydraulic limits and that the longer or repeated drought periods would have affected the growth considerably.