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<p>Mauritia flexuosa palm swamp, the prevailing Peruvian Amazon peatland ecosystem, is</p><p>extensively threatened by degradation. The unsustainable practice of cutting whole</p><p>palms for fruit extraction modifies forest's structure and composition and eventually</p><p>alters peat-derived greenhouse gas (GHG) emissions. We evaluated the spatio-temporal</p><p>variability of soil N<sub>2</sub>O and CH<sub>4</sub> fluxes and environmental controls along a palm swamp</p><p>degradation gradient formed by one undegraded site (Intact), one moderately degraded</p><p>site (mDeg) and one heavily degraded site (hDeg). Microscale variability differentiated</p><p>hummocks supporting live or cut palms from surrounding hollows. Macroscale analysis</p><p>considered structural changes in vegetation and soil microtopography as impacted</p><p>by degradation. Variables were monitored monthly over 3 years to evaluate intra- and</p><p>inter-annual variability. Degradation induced microscale changes in N<sub>2</sub>O and CH<sub>4</sub> emission</p><p>trends and controls. Site-scale average annual CH<sub>4</sub> emissions were similar along the</p><p>degradation gradient (225.6 ± 50.7, 160.5 ± 65.9 and 169.4 ± 20.7 kg C ha<sup>−1</sup> year<sup>−1</sup> at</p><p>the Intact, mDeg and hDeg sites, respectively). Site-scale average annual N<sub>2</sub>O emissions</p><p>(kg N ha<sup>−1</sup> year<sup>−1</sup>) were lower at the mDeg site (0.5 ± 0.1) than at the Intact (1.3 ± 0.6) and</p><p>hDeg sites (1.1 ± 0.4), but the difference seemed linked to heterogeneous fluctuations</p><p>in soil water-filled pore space (WFPS) along the forest complex rather than to degradation.</p><p>Monthly and annual emissions were mainly controlled by variations in WFPS, water</p><p>table level (WT) and net nitrification for N<sub>2</sub>O; WT, air temperature and net nitrification</p><p>for CH<sub>4</sub>. Site-scale N<sub>2</sub>O emissions remained steady over years, whereas CH<sub>4</sub> emissions</p><p>rose exponentially with increased precipitation. While the minor impact of degradation</p><p>on palm swamp peatland N<sub>2</sub>O and CH<sub>4</sub> fluxes should be tested elsewhere, the evidenced</p><p>large and variable CH<sub>4</sub> emissions and significant N<sub>2</sub>O emissions call for improved modeling</p><p>of GHG dynamics in tropical peatlands to test their response to climate changes.</p>

AbstractLand use and agricultural practices can result in important contributions to the global source strength of atmospheric nitrous oxide (N2O) and methane (CH4). However, knowledge of gas flux from irrigated agriculture is very limited. From April 2005 to October 2006, a study was conducted in the Aral Sea Basin, Uzbekistan, to quantify and compare emissions of N2O and CH4 in various annual and perennial land‐use systems: irrigated cotton, winter wheat and rice crops, a poplar plantation and a natural Tugai (floodplain) forest. In the annual systems, average N2O emissions ranged from 10 to 150 μg N2O‐N m−2 h−1 with highest N2O emissions in the cotton fields, covering a similar range of previous studies from irrigated cropping systems. Emission factors (uncorrected for background emission), used to determine the fertilizer‐induced N2O emission as a percentage of N fertilizer applied, ranged from 0.2% to 2.6%. Seasonal variations in N2O emissions were principally controlled by fertilization and irrigation management. Pulses of N2O emissions occurred after concomitant N‐fertilizer application and irrigation. The unfertilized poplar plantation showed high N2O emissions over the entire study period (30 μg N2O‐N m−2 h−1), whereas only negligible fluxes of N2O (<2 μg N2O‐N m−2 h−1) occurred in the Tugai. Significant CH4 fluxes only were determined from the flooded rice field: Fluxes were low with mean flux rates of 32 mg CH4 m−2 day−1 and a low seasonal total of 35.2 kg CH4 ha−1. The global warming potential (GWP) of the N2O and CH4 fluxes was highest under rice and cotton, with seasonal changes between 500 and 3000 kg CO2 eq. ha−1. The biennial cotton–wheat–rice crop rotation commonly practiced in the region would average a GWP of 2500 kg CO2 eq. ha−1 yr−1. The analyses point out opportunities for reducing the GWP of these irrigated agricultural systems by (i) optimization of fertilization and irrigation practices and (ii) conversion of annual cropping systems into perennial forest plantations, especially on less profitable, marginal lands.

AbstractA decline in water availability due to rising temperatures and growing water demand presents significant and unique challenges to agricultural producers in Uzbekistan. This study investigates the impact of climate change on farm revenues and water use efficiencies in Western Uzbekistan. A spatially explicit stochastic optimization model is used to analyze crop and water allocation decisions under conditions of uncertainty for irrigation water availability in the area for the first time.Results show farmers’ income could fall by as much as 25% with a 3.2°C temperature increase and a 15% decline in irrigation. Farmers located in the tail end of the irrigation system could lose an even greater share of their revenues. A more conservative increase in temperature could increase farmer income by as much as 46% with a 2.2° temperature increase and only 8% decline in irrigation water since some crops benefit from extended vegetation periods. Under both pessimistic and optimistic scenarios, environmental challenges due to shallow groundwater tables may improve associated with enhanced water use efficiency.

Miombo woodlands are extensive dry forest ecosystems in central and southern Africa covering ≈2.7 million km2. Despite their vast expanse and global importance for carbon storage, the long-term carbon stocks and dynamics have been poorly researched. The objective of this paper was to present and summarize the evidence gathered on aboveground carbon (AGC) and soil organic carbon (SOC) stocks of miombo woodlands from the 1960s to mid-2018 through a literature review. We reviewed the data to find out to what extent aboveground carbon and soil organic carbon stocks are found in miombo woodlands and further investigated if are there differences in carbon stocks based on woodland categories (old-growth, disturbed and re-growth). A review protocol was used to identify 56 publications from which quantitative data on AGC and SOC stocks were extracted. We found that the mean AGC in old-growth miombo (45.8 ± 17.8 Mg C ha−1), disturbed miombo (26.7 ± 15 Mg C ha−1), and regrowth miombo (18.8 ± 16.8 Mg C ha−1) differed significantly. Data on rainfall, stand age, and land-use suggested that the variability in aboveground carbon is site-specific, relating to climatic and geographic conditions as well as land-use history. SOC stocks in both old-growth and re-growth miombo were found to vary widely. It must be noted these soil data are provided only for information; they inconsistently refer to varying soil depths and are thus difficult to interpret. The wide range reported suggests a need for further studies which are much more systematic in method and reporting. Other limitations of the dataset include the lack of systematic sampling and lack of data in some countries, viz. Angola and Democratic Republic of the Congo.

This article describes various opportunities but also constraints to greater crop diversification, and the impact on local sustainability in the Khorezm province of Uzbekistan in the Aral Sea basin. At present, approximately 70% of the area in this study region is sown to irrigated cotton and winter wheat under the so-called state mandate. We present evidence of the benefits of moving away from this approach toward more diversified farming with an increasing area of alternative crops in the selected region. We report on a series of studies that included a) crop suitability screening based on secondary data, b) joint farmer experiments, and c) a mathematical simulation model with the overarching objective to assess potential benefits and constraints for crop diversification. The findings of this long-term, multiyear, and multidisciplinary approach show that greater crop diversity can increase water use efficiency, and secure farm income in dryland areas prone to water scarcity and soil salinity. In additio...

Abstract Although carbon (C) stored deep in soils of tree-dominated land use systems in the tropics represents a large reservoir of organic matter its vulnerability to land use change has been hardly assessed. To fill this gap, we sampled Acrisols down to 3 m under three different land use systems; namely, recent cacao agroforestry ( 50 years), and secondary forest (>50 years) all located in Kapuas Hulu regency, West Kalimantan, Indonesia. We then assessed soil organic carbon (SOC) stocks as well as C accumulated in above- and belowground biomass, litter and dead wood debris at the soil surface. The amount of C stored in soils to a depth of 1 m exceeded the amount stored in living biomass (Σ C stored in roots, understorey and overstorey) strongly in the cacao agroforestry systems (69 Mg SOC vs. 12 Mg biomass-C ha−1), slightly in young rubber gardens (85 Mg SOC vs. 69 Mg C ha−1), but not in old rubber gardens (87 Mg SOC vs. 200 Mg C ha−1) and secondary forests (65 Mg SOC vs. 138 Mg C ha−1). Additionally in the older systems, up to 140 Mg C ha−1 (old rubber gardens) and 116 Mg C ha−1 (secondary forest) were found in soils to a depth of 3 m, thus raising soil C stocks by 60 to 80% relative to C stored in upper soil (0 to 1 m). We conclude that (1) the form of land use and land use change can substantially affect C stocks in living biomass, with aboveground biomass in old rubber gardens comparable to that of secondary forests; and (2) that land use change can reduce SOC in topsoil, but that substantial C stocks found in deep (down to 3 m) subsoil remain stable.

National-scale assessments of post-deforestation land-use are crucial for decreasing deforestation and forest degradation-related emissions. In this research, we assess the potential of different satellite data modalities (single-date, multi-date, multi-resolution, and an ensemble of multi-sensor images) for classifying land-use following deforestation in Ethiopia using the U-Net deep neural network architecture enhanced with attention. We performed the analysis on satellite image data retrieved across Ethiopia from freely available Landsat-8, Sentinel-2 and Planet-NICFI satellite data. The experiments aimed at an analysis of (a) single-date images from individual sensors to account for the differences in spatial resolution between image sensors in detecting land-uses, (b) ensembles of multiple images from different sensors (Planet-NICFI/Sentinel-2/Landsat-8) with different spatial resolutions, (c) the use of multi-date data to account for the contribution of temporal information in detecting land-uses, and, finally, (d) the identification of regional differences in terms of land-use following deforestation in Ethiopia. We hypothesize that choosing the right satellite imagery (sensor) type is crucial for the task. Based on a comprehensive visually interpreted reference dataset of 11 types of post-deforestation land-uses, we find that either detailed spatial patterns (single-date Planet-NICFI) or detailed temporal patterns (multi-date Sentinel-2, Landsat-8) are required for identifying land-use following deforestation, while medium-resolution single-date imagery is not sufficient to achieve high classification accuracy. We also find that adding soft-attention to the standard U-Net improved the classification accuracy, especially for small-scale land-uses. The models and products presented in this work can be used as a powerful data resource for governmental and forest monitoring agencies to design and monitor deforestation mitigation measures and data-driven land-use policy.