Publications
67 results found
Wang X, Chen G, Awange J, et al., 2024, Establishing the global isoscape of leaf carbon in C3 plants through the integrations of remote sensing, carbon, geographic, and physiological information, Remote Sensing of Environment, Vol: 302, ISSN: 0034-4257
The carbon isotope composition (δ13CLeaf) of C3 plant leaves provides valuable information on the carbon-water cycle of vegetation and their responses to climate change within terrestrial ecosystems. However, global applications of δ13CLeaf are hindered by a lack of global long-term spatial maps (isoscapes) that capture vegetation δ13CLeaf variations. The ways in which δ13CLeaf varies over time and across regions are still unknown. In this study, we collected leaf carbon isotope samples across the globe and selected the optimal predictive model from three machine learning algorithms to construct long-term annual global δ13CLeaf isoscapes at a spatial resolution of 0.05° for natural C3 plants between 2001 and 2020. We also assessed the potential of remotely sensed spectral bands, atmospheric CO2 characteristics, geographic, and physiological information to estimate the δ13CLeaf of the global C3 plants. Our results show that the random forest (RF) algorithm can more accurately construct the δ13CLeaf isoscape (R2 = 0.61, Nash Sutcliffe = 0.61, RMSE = 1.21‰, MAE = 0.91‰) than the multilayer perceptron (MLP) and support vector machine (SVM). The inclusion of atmospheric CO2 characteristics, geographical, and physiological information greatly improves prediction compared to relying only on spectral bands. Among the variables, elevation, band 3 spectral reflectance, and solar-induced chlorophyll fluorescence were the three most important variables for constructing the isoscape model, and their relative importance all exceeded 85%. The predicted isoscape revealed strong spatial heterogeneity of δ13CLeaf for C3 plants at a global scale between different continental regions, with enriched values occurring in high-altitude cold and arid regions, and depleted values occurring in warm, humid, or tropical regions. For the first time, we estimated the global depleted rate of δ13CLeaf in C3 plant (−0.0491
Flavio Espinoza-Monje J, Saiz G, Cifuentes G, et al., 2023, Management of invasive shrubs to mitigate wildfire through fuel pellet production in central Chile, Fuel, Vol: 354, ISSN: 0016-2361
The use of pellets as a replacement for firewood has been promoted in Chile to mitigate atmospheric pollution. However, their high demand has generated stock shortages, which has motivated the search for alternative sources of feedstock. Furthermore, invasive shrubs are a highly available biomass source for bioenergy production in central-southern Chile and may be a significant factor contributing to the spread and increasing virulence observed in wildfires across the region. This study aimed to determine the change in wildfire indicators related to the removal of invasive shrubs in selected zones in the Biobío region and to assess the physicochemical properties of the extracted biomass to develop a pellet formulation to produce a material conforming to ISO standards. The biomass management of Teline monspessulana, Ulex europaeus, and Rubus ulmifolius was evaluated using a fire simulation tool in three areas with contrasting physio-climatic conditions. Our simulation results demonstrated the effectiveness of shrub management on three critical wildfire indicators. Namely, significant decreases were observed in fireline intensity (kW/m) 58–75%, flame length (m) 0–40%, and heat per unit area (kW/m2) 86%. Furthermore, a biomass quality index (BQI) was developed based on the physicochemical parameters of the three shrubs assessed. Based on this BQI, T. monspessulana was selected as the most promising shrub biomass and was consequently used in a pilot shrub-pinewood blending to produce pellets. A blending of 20:80%m/m exhibited properties close to the ISO standard. Our results show that the management of invasive shrubs has the potential to minimize the virulence of wildfires, while the physicochemical characteristics and availability of one of the shrubs analyzed (T. monspessulana) make it a viable alternative biomass source for pellet production in the region.
Souza-Alonso P, Saiz G, Garcia RA, et al., 2022, Post-fire ecological restoration in Latin American forest ecosystems: Insights and lessons from the last two decades, FOREST ECOLOGY AND MANAGEMENT, Vol: 509, ISSN: 0378-1127
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- Citations: 8
Adzhar R, Kelley DI, Dong N, et al., 2022, MODIS Vegetation Continuous Fields tree cover needs calibrating in tropical savannas, BIOGEOSCIENCES, Vol: 19, Pages: 1377-1394, ISSN: 1726-4170
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- Citations: 4
Ortiz C, Jose Fernandez-Alonso M, Kitzler B, et al., 2022, Variations in soil aggregation, microbial community structure and soil organic matter cycling associated to long-term afforestation and woody encroachment in a Mediterranean alpine ecotone, GEODERMA, Vol: 405, ISSN: 0016-7061
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- Citations: 14
Blundo C, Carilla J, Grau R, et al., 2021, Taking the pulse of Earth's tropical forests using networks of highly distributed plots, BIOLOGICAL CONSERVATION, Vol: 260, ISSN: 0006-3207
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- Citations: 54
Panzou GJL, Fayolle A, Jucker T, et al., 2021, Pantropical variability in tree crown allometry, GLOBAL ECOLOGY AND BIOGEOGRAPHY, Vol: 30, Pages: 459-475, ISSN: 1466-822X
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- Citations: 21
Djagbletey GD, Addo-Danso SD, Duah-Gyamfi A, et al., 2021, WOODY PLANT COMPOSITION, DIVERSITY AND CONSERVATION STATUS OF A PROTECTED AREA IN THE TRANSITION ZONE OF GHANA, Journal of the Ghana Science Association, Vol: 20, Pages: 6-16
Botanical assessment was conducted in the Boabeng-Fiema Monkey Sanctuary (BFMS), aimed at assessing the woody plant composition, diversity and structure, of vegetation types and conservation importance of the reserve. Ten (20m×50m) plots were established in forest, transition and savanna stands of BFMS. Overall, 66 species representing 55 genera and 26 families were recorded. Floristic attributes showed lower number of species, families, genera and stem density in savanna (24, 14, 21 and 97, respectively) compared to transition (37, 21, 35, 596) and forest (42, 20, 37, 149). The most dominant families were Fabaceae, Moraceae, Rubiaceae and Malvaceae whilst trees were the most predominant growth form accounting for 66% of species recorded. Trees were more diverse in forest (1.32) and savanna (1.10) while shrubs were more diverse in transition (1.14). Non-metric multidimensional scaling ordination showed distribution of distinct tree and shrub species across stands. Anogeisus leiocarpus and Detarium senegalensis were predominant in the savanna vegetation with Importance Value Indices (IVI) of 93.1 and 34.9, respectively, while in the transition zone, A. leiocarpus and the shrub, Uvaria chamae, were the most dominant with IVI of 71.1 and 38.9, respectively. Dominant species in the forest were Bombax buonopozense and Lecaniodiscus cupanioides with IVI of 42.5 and 25.1, respectively. The transition zone had a Genetic Heat Index (GHI) of 254.3, followed by the forest and savanna zones with values of 140.0 and 97.6, respectively. Our results indicated the BFMS harbours several valuable plant species, suggesting its potential as in-situ conservation as well as tourist, research and education site.
Quesada CA, Paz C, Oblitas E, et al., 2020, Variations in soil chemical and physical properties explain basin-wide Amazon forest soil carbon concentrations
<jats:p> &lt;p&gt;We investigate the edaphic, mineralogical and climatic controls of soil organic carbon (SOC) concentration utilising data from 147 primary forest soils (0-30 cm depth) sampled in eight different countries across the Amazon Basin. Sampling across 14 different World Reference Base soil groups our data suggest that stabilisation mechanism varies with pedogenetic level. Specifically, although SOC concentrations in Ferralsols and Acrisols were best explained by simple variations in clay content &amp;#8211; this presumably being due to their relatively uniform kaolinitic mineralogy &amp;#8211; this was not the case for less weathered soils such as Alisols, Cambisols and Plinthosols for which interactions between Al species, soil pH and litter quality are argued to be much more important. Although for more strongly weathered soils the majority of SOC is located within the aggregate fraction, for the less weathered soils most of the SOC is located within the silt and clay fractions. It thus seems that for highly weathered soils SOC storage is mostly influenced by surface area variations arising from clay content, with physical protection inside aggregates rendering an additional level of protection against decomposition. On the other hand, most of SOC in less weathered soils are associated with the precipitation of aluminium-carbon complexes within the fine soil fraction, with this mechanism enhanced by the presence of high levels of aromatic, carboxyl-rich organic matter compounds. Also examined as part of this study were a relatively small number of arenic soils (viz. Arenosols and Podzols) for which there was a small but significant influence of clay and silt content variations on SOM storage and with fractionation studies showing that particulate organic matter may accounting for up to 0.60 of arenic soil SOC. In contrast to what were in all cases strong influences of soil and/or litter quality properties, a
Quesada CA, Paz C, Mendoza EO, et al., 2020, Variations in soil chemical and physical properties explain basin-wide Amazon forest soil carbon concentrations, SOIL, Vol: 6, Pages: 53-88, ISSN: 2199-3971
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- Citations: 26
Fungo B, Chen Z, Butterbach-Bahl K, et al., 2019, Nitrogen turnover and N<sub>2</sub>O/N<sub>2</sub> ratio of three contrasting tropical soils amended with biochar, GEODERMA, Vol: 348, Pages: 12-20, ISSN: 0016-7061
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- Citations: 12
Quesada CA, Paz C, Oblitas Mendoza E, et al., 2019, Variations in soil chemical and physical properties explain basin-wide variations in Amazon forest soil carbon densities
<jats:p>Abstract. We investigate the edaphic, mineralogical and climatic controls of soil organic carbon (SOC) concentration utilising data from 147 pristine forest soils sampled in eight different countries across the Amazon Basin. Sampling across 14 different World Reference Base soil groups our data suggest that stabilisation mechanism varies with pedogenetic level. Specifically, although SOC concentrations in Ferralsols and Acrisols were best explained by simple variations in clay content – this presumably being due to their relatively uniform kaolinitic mineralogy – this was not the case for less weathered soils such as Alisols, Cambisols and Plinthosols for which interactions between Al species, soil pH and litter quality seem to be much more important. SOC fractionation studies further showed that, although for more strongly weathered soils the majority of SOC is located within the aggregate fraction, for the less weathered soils most of the SOC is located within the silt and clay fractions. It thus seems that for highly weathered soils SOC storage is mostly influenced by surface area variations arising from clay content, with physical protection inside aggregates rendering an additional level of protection against decomposition. On the other hand, most of SOC in less weathered soils is associated with the precipitation of aluminium-carbon complexes within the fine soil fraction and with this mechanism enhanced by the presence of high levels of aromatic, carboxyl-rich organic matter compounds. Also examined as part of this study were a relatively small number of arenic soils (viz. Arenosols and Podzols) for which there was a small but significant influence of clay and silt content variations on SOM storage and with fractionation studies showing that particulate organic matter may accounting for up to 0.60 of arenic soil SOC. In contrast to what were in all cases strong influences of soil and/or litter quality properties, after accounting for
Gerschlauer F, Saiz G, Schellenberger Costa D, et al., 2019, Stable carbon and nitrogen isotopic composition of leaves, litter, and soils of various ecosystems along an elevational and land-use gradient at Mount Kilimanjaro, Tanzania, Biogeosciences, Vol: 16, Pages: 409-424, ISSN: 1726-4170
Variations in the stable isotopic composition of carbon (δ13C) and nitrogen (δ15N) of fresh leaves, litter, and topsoils were used to characterize soil organic matter dynamics of 12 tropical ecosystems in the Mount Kilimanjaro region, Tanzania. We studied a total of 60 sites distributed along five individual elevational transects (860- 4550ma.s.l.), which define a strong climatic and land-use gradient encompassing semi-natural and managed ecosystems. The combined effects of contrasting environmental conditions, vegetation, soil, and management practices had a strong impact on the δ13C and δ15N values observed in the different ecosystems. The relative abundance of C3 and C4 plants greatly determined the δ13C of a given ecosystem. In contrast, δ15N values were largely controlled by land-use intensification and climatic conditions. The large δ13C enrichment factors (δ13Clitter -δ13Csoil) and low soil C=N ratios observed in managed and disturbed systems agree well with the notion of altered SOM dynamics. Besides the systematic removal of the plant biomass characteristic of agricultural systems, annual litterfall patterns may also explain the comparatively lower contents of C and N observed in the topsoils of these intensively managed sites. Both δ15N values and calculated δ15N-based enrichment factors (δ15Nlitter -δ15Nsoil/ suggest the tightest nitrogen cycling at high-elevation (>3000ma.s.l.) ecosystems and more open nitrogen cycling both in grass-dominated and intensively managed cropping systems. However, claims about the nature of the N cycle (i.e. open or closed) should not be made solely on the basis of soil δ15N as other processes that barely discriminate against 15N (i.e. soil nitrate leaching) have been shown to be quite significant in Mount Kilimanjaro's forest ecosystems. The negative correlation of δ15N values with soil nitrogen content and the positive correlation w
Gerschlauer F, Saiz G, Schellenberger Costa D, et al., 2018, Supplementary material to &quot;Stable carbon and nitrogen isotopic composition of leaves, litter, and soils of various tropical ecosystems along an elevational and land-use gradient at Mount Kilimanjaro, Tanzania&quot;
Abaker WE, Berninger F, Saiz G, et al., 2018, Linkages between soil carbon, soil fertility and nitrogen fixation in Acacia senegal plantations of varying age in Sudan, PeerJ, Vol: 6, ISSN: 2167-8359
BackgroundOver the last decades sub-Saharan Africa has experienced severe land degradation and food security challenges linked to loss of soil fertility and soil organic matter (SOM), recurrent drought and increasing population. Although primary production in drylands is strictly limited by water availability, nutrient deficiencies, particularly of nitrogen (N) and phosphorus (P), are also considered limiting factors for plant growth. It is known that SOM (often measured as soil organic carbon (SOC)) is a key indicator of soil fertility, therefore, management practices that increase SOM contents, such as increasing tree cover, can be expected to improve soil fertility. The objectives of this study were to investigate the effect of Acacia senegal (Senegalia senegal) trees on soil nitrogen, phosphorus and potassium (K) in relation to SOC, the potential of A. senegal for N2 fixation, and to identify possible N and P ecosystem limitations.MethodsSoil nutrient (total N, P, K and available P and exchangeable K) concentrations and stocks were determined for the 0–10, 10–20,20–30 and 30–50 cm layers of A. senegal plantations of varying age (ranging from 7 to 24-years-old) and adjacent grasslands (reference) at two sites in semi-arid areas of Sudan. At both sites, three plots were established in each grassland and plantation. The potential of A. senegal for N2 fixation in relation to plantations age was assessed using δ15N isotopic abundances and nutrient limitations assessed using C:N:P stoichiometry.ResultsSoil concentrations of all studied nutrients were relatively low but were significantly and directly correlated to SOC concentrations. SOC and nutrient concentrations were the highest in the topsoil (0–10 cm) and increased with plantations age. Acacia foliage δ15N values were >6‰ and varied little with plantations age. Soil C:N and C:P ratios did not differ between grassland and plantations and only 0–10 cm layer
Saiz G, Goodrick I, Wurster C, et al., 2018, Preferential production and transport of grass-derived pyrogenic carbon in NE-Australian savanna ecosystems, Frontiers in Earth Science, Vol: 5, ISSN: 2296-6463
Understanding the main factors driving fire regimes in grasslands and savannas is critical to better manage their biodiversity and functions. Moreover, improving our knowledge on pyrogenic carbon (PyC) dynamics, including formation, transport and deposition, is fundamental to better understand a significant slow-cycling component of the global carbon cycle, particularly as these ecosystems account for a substantial proportion of the area globally burnt. However, a thorough assessment of past fire regimes in grass-dominated ecosystems is problematic due to challenges in interpreting the charcoal record of sediments. It is therefore critical to adopt appropriate sampling and analytical methods to allow the acquisition of reliable data and information on savanna fire dynamics. This study uses hydrogen pyrolysis (HyPy) to quantify PyC abundance and stable isotope composition (δ13C) in recent sediments across 38 micro-catchments covering a wide range of mixed C3/C4 vegetation in north Queensland, Australia. We exploited the contrasting δ13C values of grasses (i.e., C4; δ13C > −15‰) and woody vegetation (i.e., C3; δ13C < −24‰) to assess the preferential production and transport of grass-derived PyC in savanna ecosystems. Analyses were conducted on bulk and size-fractionated samples to determine the fractions into which PyC preferentially accumulates. Our data show that the δ13C value of PyC in the sediments is decoupled from the δ13C value of total organic carbon, which suggests that a significant component of PyC may be derived from incomplete grass combustion, even when the proportion of C4 grass biomass in the catchment was relatively small. Furthermore, we conducted 16 experimental burns that indicate that there is a comminution of PyC produced in-situ to smaller particles, which facilitates the transport of this material, potentially affecting its preservation potential. Savanna fires preferentially
Zhang Y, Liu M, Saiz G, et al., 2017, Enhancement of root systems improves productivity and sustainability in water saving ground cover rice production system, FIELD CROPS RESEARCH, Vol: 213, Pages: 186-193, ISSN: 0378-4290
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- Citations: 19
Tejedor J, Saiz G, Rennenberg H, et al., 2017, Thinning of Beech Forests Stocking on Shallow Calcareous Soil Maintains Soil C and N Stocks in the Long Run, FORESTS, Vol: 8, ISSN: 1999-4907
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- Citations: 7
Hu B, Zhou M, Dannenmann M, et al., 2017, Comparison of nitrogen nutrition and soil carbon status of afforested stands established in degraded soil of the Loess Plateau, China, FOREST ECOLOGY AND MANAGEMENT, Vol: 389, Pages: 46-58, ISSN: 0378-1127
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- Citations: 31
Diaz-Pines E, Molina-Herrera S, Dannenmann M, et al., 2017, Nitrate leaching and soil nitrous oxide emissions diminish with time in a hybrid poplar short-rotation coppice in southern Germany, GLOBAL CHANGE BIOLOGY BIOENERGY, Vol: 9, Pages: 613-626, ISSN: 1757-1693
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- Citations: 20
Pelster D, Rufino M, Rosenstock T, et al., 2017, Smallholder farms in eastern African tropical highlands have low soil greenhouse gas fluxes, BIOGEOSCIENCES, Vol: 14, Pages: 187-202, ISSN: 1726-4170
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- Citations: 38
Saiz G, Wandera FM, Pelster DE, et al., 2016, Long-term assessment of soil and water conservation measures (Fanya-juu terraces) on soil organic matter in South Eastern Kenya, GEODERMA, Vol: 274, Pages: 1-9, ISSN: 0016-7061
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- Citations: 29
Feldpausch TR, Phillips OL, Brienen RJW, et al., 2016, Amazon forest response to repeated droughts, Global Biogeochemical Cycles, Vol: 30, Pages: 964-982, ISSN: 0886-6236
The Amazon Basin has experienced more variable climate over the last decade, with a severe and widespread drought in 2005 causing large basin-wide losses of biomass. A drought of similar climatological magnitude occurred again in 2010; however, there has been no basin-wide ground-based evaluation of effects on vegetation. We examine to what extent the 2010 drought affected forest dynamics using ground-based observations of mortality and growth from an extensive forest plot network. We find that during the 2010 drought interval, forests did not gain biomass (net change: −0.43 Mg ha−1, confidence interval (CI): −1.11, 0.19, n = 97), regardless of whether forests experienced precipitation deficit anomalies. This contrasted with a long-term biomass sink during the baseline pre-2010 drought period (1998 to pre-2010) of 1.33 Mg ha−1 yr−1 (CI: 0.90, 1.74, p < 0.01). The resulting net impact of the 2010 drought (i.e., reversal of the baseline net sink) was −1.95 Mg ha−1 yr−1 (CI:−2.77, −1.18; p < 0.001). This net biomass impact was driven by an increase in biomass mortality (1.45 Mg ha−1 yr−1 CI: 0.66, 2.25, p < 0.001) and a decline in biomass productivity (−0.50 Mg ha−1 yr−1, CI:−0.78, −0.31; p < 0.001). Surprisingly, the magnitude of the losses through tree mortality was unrelated to estimated local precipitation anomalies and was independent of estimated local pre-2010 drought history. Thus, there was no evidence that pre-2010 droughts compounded the effects of the 2010 drought. We detected a systematic basin-wide impact of the 2010 drought on tree growth rates across Amazonia, which was related to the strength of the moisture deficit. This impact differed from the drought event in 2005 which d
Abaker WE, Berninger F, Saiz G, et al., 2016, Contribution of <i>Acacia senegal</i> to biomass and soil carbon in plantations of varying age in Sudan, FOREST ECOLOGY AND MANAGEMENT, Vol: 368, Pages: 71-80, ISSN: 0378-1127
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- Citations: 16
Saiz G, Albrecht A, 2016, Methods for Smallholder Quantification of Soil Carbon Stocks and Stock Changes, METHODS FOR MEASURING GREENHOUSE GAS BALANCES AND EVALUATING MITIGATION OPTIONS IN SMALLHOLDER AGRICULTURE, Editors: Rosenstock, Rufino, ButterbachBahl, Wollenberg, Richards, Publisher: SPRINGER, Pages: 135-162, ISBN: 978-3-319-29792-7
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- Citations: 7
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