Global ecosystem thresholds driven by aridity

Aridity, which is increasing worldwide because of climate change, affects the structure and functioning of dryland ecosystems. Whether aridification leads to gradual (versus abrupt) and systemic (versus specific) ecosystem changes is largely unknown. We investigated how 20 structural and functional ecosystem attributes respond to aridity in global drylands. Aridification led to systemic and abrupt changes in multiple ecosystem attributes. These changes occurred sequentially in three phases characterized by abrupt decays in plant productivity, soil fertility, and plant cover and richness at aridity values of 0.54, 0.7, and 0.8, respectively. More than 20% of the terrestrial surface will cross one or several of these thresholds by 2100, which calls for immediate actions to minimize the negative impacts of aridification on essential ecosystem services for the more than 2 billion people living in drylands.This research was supported by the European Research Council [ERC grant nos. 242658 (BIOCOM) and 647038 (BIODESERT) awarded to F.T.M.]. M.B. acknowledges support from a Juan de la Cierva Formación grant from the Spanish Ministry of Economy and Competitiveness (FJCI-2018-036520-I). F.T.M. acknowledges support from Generalitat Valenciana (CIDEGENT/2018/041), the Alexander von Humboldt Foundation, and the Synthesis Centre for Biodiversity Sciences (sDiv) of the German Centre for Integrative Biodiversity Research (iDiv). M.D.-B. acknowledges support from the Marie Sklodowska-Curie Actions of the Horizon 2020 Framework Program H2020-MSCA-IF-2016 under REA grant no. 702057. S.S. was supported by the Spanish Government under a Ramón y Cajal contract (RYC-2016- 20604). N.G. was supported by the AgreenSkills+ fellowship program, which has received funding from the EU’s Seventh Framework Programme under grant no. FP7-609398 (AgreenSkills+ contract). V.M. was supported by FRQNT-2017-NC-198009 and NSERC Discovery 2016-05716 grants from the government of Canada. H.S. was supported by a Juan de la Cierva Formación grant from the Spanish Ministry of Economy and Competitiveness (FJCI-2015-26782). A.L. and M.C.R. were supported by an ERC Advanced Grant (Gradual Change grant no. 694368) and by the Deutsche Forschungsgesellschaft (grant no. RI 1815/16-1). Y.Z. was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDA19030500)

Sea ice concentration inversion based on ASI algorithm combined with Bootstrap algorithm

Weather filters are frequently used to lessen the interference while using the ARTSIST Sea Ice (ASI) algorithm, which is based on Advanced Microwave Scanning Radiometer for EOS/Advanced Microwave Scanning Radiometer-2 (AMSR-E/AMSR-2) 89 GHz brightness temperature (Tb) data to calculate sea ice concentration (SIC) with high spatial resolution. However, the weather filters may cause low concentration sea ice to be mistaken for sea water, which decreases the accuracy of the SIC inversion. This paper proposed the ASI algorithm combined with the Bootstrap (BT) algorithm for SIC inversion to increase the accuracy of the SIC inversion. First, use the weather filters to screen out an area that has been disrupted by the external factors like clouds and water vapor. Second, the BT algorithm is used in this area to accomplish SIC inversion. Based on the proposed method, the Antarctic SIC results in February 2018 were obtained and compared with the SIC obtained from the ASI algorithm. The results demonstrated that the SIC inversion based on ASI algorithm combined with BT algorithm is practicable. By comparing the SIC results of Landsat-8 data, it was further verified that the SIC inversion based on ASI algorithm combined with BT algorithm has higher accuracy compared to the ASI algorithm. As a result, the accuracy of SIC inversion can be improved to some extent by combining the ASI algorithm and the BT algorithm

Snowmelt detection on the Antarctic ice sheet and ice Shelves based on AMSR2 89 GHz channels

Currently, the spatial resolution of snowmelt detection based on low-frequency brightness temperature data (less than or equal to 36 GHz) from the Advanced Microwave Scanning Radiometer 2 (AMSR2) is low, which inhibits the determination of accurate snowmelt changes. The spatial resolution of the AMSR2 89 GHz data is at least twice that of other microwave channels, but liquid water in clouds seriously affects the propagation of the high-frequency microwave signal. In order to apply microwave radiometer AMSR-2 89 GHz data with high spatial resolution but easily disturbed by clouds and water vapor to Antarctic ice-sheet near-surface snowmelt detection, this paper builds a screening model and correction model for 89 GHz data with large interference based on the high reliability of AMSR-2 36 GHz data and the high spatial resolution of 89 GHz data and the internal relationship between the two data. The method proposed in this paper was compared with the cross-polarised gradient ratio (XPGR) algorithm and six automatic weather stations. The average detection accuracy of the proposed method and the XPGR algorithm is 97% and 95%, respectively. The experimental results show that the snowmelt detection method proposed in this paper can more accurately detect the snowmelt on the Antarctic Ice Sheet and Ice Shelves

Aridity Thresholds Determine the Relationships Between Ecosystem Functioning and Remotely Sensed Indicators Across Patagonia

Emerging evidence suggests that ecosystem responses to increases in atmospheric aridity, a hallmark of climate change, exhibit multiple thresholds across global drylands. However, it is not clear whether aridity thresholds exist in the relationships between ecosystem functions and remotely sensed indicators (RSIs). Assessing this is important because these empirical relationships underpin the statistical models commonly used to estimate ecosystem functioning across large spatial scales, which typically uses data from RSI. We evaluated how the relationships between nutrient cycling index (NCI; a proxy of ecosystem functioning) measured in situ and RSI [albedo and normalized difference vegetation index (NDVI)] change along with a wide aridity (1 - [precipitation/potential evapotranspiration]) gradient in Patagonia (Argentina). For doing so, we used field-based NCI data from 235 ecosystems that were surveyed twice (2008-2013 and 2014-2018). Three aridity thresholds were identified when evaluating the RSI-NCI relationships. The first threshold was found around aridity values ranging from 0.44 to 0.60, while the second and third were concentrated around aridity values of 0.69 and 0.82, respectively. These results indicate that RSI-NCI relationships changed drastically along aridity gradients, and these thresholds should be considered when evaluating ecosystem functions using RSI. In addition, we also found that the relationships between NCI and albedos were not significant around aridity values of 0.82. These results were consistent across sampling dates. Our findings imply that empirical models of the RSI-NCI relationship employing only albedos/reflectance as inputs are not reliable under the most arid conditions and can be used to improve the effectiveness of the use of RSI to monitor and predict changes in ecosystem functioning across large environmental gradients in drylands.This work was supported in part by the Research Foundation of Henan University of Technology under Grant 31401178, in part by the Henan Provincial Science and Technology Research Project under Grant 192102210101, in part by the European Research Council (BIODESERT Project) under ERC Grant Agreement 647038, in part by China Scholarship Council (CSC) under Grant 201909895003, and in part by the PEi040 project of National Institute of Agricultural Technology (INTA) of Argentina and Generalitat Valenciana under Grant CIDEGENT/2018/041

Assessing the adaptive capacity of urban form to climate stress: a case study on an urban heat island

Urban land planning shapes the urban form and is considered to be one of the many tools important for climate adaptation. Yet there is little knowledge about the adaptive capacity of urban forms to climate stress, or of an appropriate assessment method. Through a case study on the urban heat island (UHI) in Xiamen City, China, we propose a novel approach that integrates several aspects to assess the adaptive capacity of urban form to climate stress. These aspects include the calculation of urban form, the determination of climate stress and land use modeling. Our results demonstrate that this approach is applicable for assessing the adaptive capacity of urban form in the historical, current and future multitime scales. Both urban planning aspects (e.g. population density, land use mix, road density and percentage of green open space) and landscape features (e.g. shape complexity, contiguity and compactness) are found to be key urban form drivers affecting UHI. The adaptive capacity of the urban form to UHI in Xiamen City has been declining dramatically, and is expected to continue to decline in the future as long as adaptation continues to not be integrated in urban land use planning. Our analysis suggests that urban managers need to review the past development model of land use and rethink the current approach to urban planning: most urgent is the need to take full account of adaptation in future land use planning and implementation, so as to enhance climate resilience

Remotely-Sensed Identification of a Transition for the Two Ecosystem States Along the Elevation Gradient: A Case Study of Xinjiang Tianshan Bogda World Heritage Site

The alpine treeline, as an ecological transition zone between montane coniferous forests and alpine meadows (two ecosystem states), is a research hotspot of global ecology and climate change. Quantitative identification of its elevation range can efficiently capture the results of the interaction between climate change and vegetation. Digital extraction and extensive analysis in such a critical elevation range crucially depend on the ability of monitoring ecosystem variables and the suitability of the experimental model, which are often restricted by the weak intersection of disciplines and the spatial-temporal continuity of the data. In this study, the existence of two states was confirmed by frequency analysis and the Akaike information criterion (AIC) as well as the Bayesian information criterion (BIC) indices. The elevation range of a transition for the two ecosystem states on the northern slope of the Bogda was identified by the potential analysis. The results showed that the elevation range of co-occurrence for the two ecosystem states was 2690–2744 m. At the elevation of 2714 m, the high land surface temperature (LST) state started to exhibit more attraction than the low LST state. This elevation value was considered as a demarcation where abrupt shifts between the two states occurred with the increase of elevation. The identification results were validated by a field survey and unmanned aerial vehicle data. Progress has been made in the transition identification for the ecosystem states along the elevation gradient in mountainous areas by combining the remotely-sensed index with a potential analysis. This study also provided a reference for obtaining the elevation of the alpine tree line quickly and accurately

Using remote sensing information to enhance the understanding of the coupling of terrestrial ecosystem evapotranspiration and photosynthesis on a global scale

International audienceUnderstanding the coupling of terrestrial ecosystem evapotranspiration (ET) and photosynthesis (gross primary productivity, GPP) is limited by inherent difficulties to provide accurate approximations of transpiration (T) and leaf-to-air vapor pressure difference (D) that is a key variable needed to define the stomata behaviors in generic methods. To address the issues and better characterize the ET-GPP relationship, we developed a novel remote sensing (RS)-driven approach (RCEEP) based on the underlying water use efficiency (uWUE) method (termed uWUE-Model). RCEEP partitions T from ET using the RS-derived fraction (rsFt) of T in ET and then links T and GPP via RS-derived canopy conductance (rsGc) instead of D. RCEEP, the original uWUE-Model, and two other uWUE-based versions (RT or RG) that only incorporate rsFt or rsGc were adjusted using the calibration data, and then inter-compared in terms of their performances (Nash-Sutcliffe efficiency, NSE) in estimating GPP from ET on a daily and monthly scale for both calibration and validation datasets ? two subsets of data from 177 flux sites covering 11 biome types over the globe. Results revealed better performances of RT and RG as compared to uWUE-Model over most biomes, implying remarkable contributions of rsFt and rsGc to a more meaningful relationship between ET and GPP. RCEEP yielded the best performances over all biome types except for evergreen forest with reasonable mean NSE values of 0.67 ? 0.68 (0.75) on a daily (monthly) scale. Further comparisons between RCEEP and two existing approaches concerning estimating GPP from ET revealed consistently better performances of RCEEP and thus, positive implications of introducing rsFt and rsGc in bridging ecosystem ET and GPP. Besides, rsFt should be used combined with rsGc to avoid degraded effectiveness for specific biome types (Savannah and Woody Savannah). These results are promising in view of improving or developing algorithms on coupled estimates of ecosystem ET and GPP and understanding the GPP dynamics concerning ET on a global scale

Enlargement of the Axial Length and Altered Ultrastructural Features of the Sclera in a Mutant Lumican Transgenic Mouse Model.

Lumican (LUM) is a candidate gene for myopia in the MYP3 locus. In this study, a mutant lumican (L199P) transgenic mouse model was established to investigate the axial length changes and ultrastructural features of the sclera. The mouse model was established by pronuclear microinjection. Transgenic mice and wild-type B6 mice were killed at eight weeks of age. Gene expression levels of LUM and collagen type I (COL1) in the sclera were analyzed by quantitative real-time polymerase chain reaction (qPCR), and the protein levels were assessed by Western blot analysis. Ocular axial lengths were measured on the enucleated whole eye under a dissecting microscope. Ultrastructural features of collagen fibrils in the sclera were examined with transmission electron microscopy (TEM). Lumican and collagen type I were both elevated at the transcriptional and protein levels. The mean axial length of eyes in the transgenic mice was significantly longer than that in the wild-type mice (3,231.0 ± 11.2 μm (transgenic group) vs 3,199.7 ± 11.1 μm (controls), p<0.05 =). Some ultrastructural changes were observed in the sclera of the transgenic mice under TEM, such as evident lamellar disorganizations and abnormal inter-fibril spacing. The average collagen fibril diameter was smaller than that in their wild-type counterparts. These results indicate that the ectopic mutant lumican (L199P) may induce enlargement of axial lengths and abnormal structures and distributions of collagen fibrils in mouse sclera. This transgenic mouse model can be used for the mechanistic study of myopia

Rapid generation of gene-targeted EPS-derived mouse models through tetraploid complementation

Abstract One major strategy to generate genetically modified mouse models is gene targeting in mouse embryonic stem (ES) cells, which is used to produce gene-targeted mice for wide applications in biomedicine. However, a major bottleneck in this approach is that the robustness of germline transmission of gene-targeted ES cells can be significantly reduced by their genetic and epigenetic instability after long-term culturing, which impairs the efficiency and robustness of mouse model generation. Recently, we have established a new type of pluripotent cells termed extended pluripotent stem (EPS) cells, which have superior developmental potency and robust germline competence compared to conventional mouse ES cells. In this study, we demonstrate that mouse EPS cells well maintain developmental potency and genetic stability after long-term passage. Based on gene targeting in mouse EPS cells, we established a new approach to directly and rapidly generate gene-targeted mouse models through tetraploid complementation, which could be accomplished in approximately 2 months. Importantly, using this approach, we successfully constructed mouse models in which the human interleukin 3 (IL3) or interleukin 6 (IL6) gene was knocked into its corresponding locus in the mouse genome. Our study demonstrates the feasibility of using mouse EPS cells to rapidly generate mouse models by gene targeting, which have great application potential in biomedical research

Total scleral gene expression levels of <i>LUM</i> and <i>COL1</i>.

<p>The relative gene expression levels were calculated using the ΔΔC_T method. The expression level of <i>LUM</i> was found to be 8.85-fold increased relative to the control level (p = 0.023). The expression level of <i>COL1</i> was 2.01-fold greater in transgenic mice; however, the difference was not statistically significant (p = 0.086). Error bar = 1 SEM. * <i>p</i><0.05.</p