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Tropical forests are among the most threatened ecosystems despite their important role in the global carbon and water cycles. In Mexico, the Yucatan Peninsula (YP) hosts near to 30% of these ecosystems. We established an ecohydrological monitoring site in a relatively pristine tropical dry forest (TDF) within "El Palmar" state reserve at the northwest of the YP, to study the seasonal dynamics of its carbon and water fluxes and to evaluate their main controls as they respond to climatic variability. Spatio‐temporal analyses using Bio‐meteorological data from an Eddy Covariance station (from January 2017 to August 2019) and remotely sensed data (from 2001 to 2019), reveal the inter and intra‐annual dynamics of carbon and water fluxes between this ecosystem and the atmosphere. The TDF's greenness, net exchange of carbon, gross primary production, ecosystem respiration, and evapotranspiration are strongly controlled by the seasonality in precipitation pulses and their legacy from recharged moisture in the shallow aquifer observed through three marked seasons: dry, rainy, and post‐rainy. The study site continuously behaves like a carbon sink with annual rates ranging between −1.09 and −7.06 tonC/ha/yr ${\mathrm{ton}}_{\mathrm{C}}/\mathrm{ha}/\mathrm{yr}$, whose performance responds to a precipitation threshold above which its productivity declines. Differences in the ecosystem productivity among years result from a combination of water and energy availability during the growing season and variable access to groundwater during the post‐rainy and dry seasons. This highlights the ecosystem sensitivity to rainfall modulation of energy and water availability throughout the year and its impact on the ecosystem's functioning and resilience. Plain Language Summary: Tropical dry forests (TDF) located northwest of the Yucatan Peninsula (YP) have been poorly valued and highly threatened by human activities. These ecosystems are capable of storing large amounts of carbon dioxide (CO2) as biomass (ranging between 5.5 and 36 tonC/ha/yr ${\mathrm{ton}}_{\mathrm{C}}/\mathrm{ha}/\mathrm{yr}$ from subtropical deciduous to sub‐deciduous and seasonally dry evergreen forests), with relatively small amounts of water obtained from precipitation and shallow groundwater. Identifying the mechanisms driving their productivity and resilience to seasonal changes in environmental stressors is of the utmost importance for devising management plans to preserve them. For this reason, the main objective of this work is to study the temporal dynamics of carbon and water fluxes and evaluate their main controls and response to the variability of climatic forcings. Field and satellite data analyses, reveal the ecosystem as a highly variable carbon sink (assimilating between −1.09 and −7.06 tonC/ha/yr ${\mathrm{ton}}_{\mathrm{C}}/\mathrm{ha}/\mathrm{yr}$), whose vegetation dynamics are modulated by the seasonal changes of precipitation and groundwater access. These analyses also reveal a decrease in biomass production rate during years with above‐average rainfall amounts, most likely due to a decrease in the amount of radiation available as a result of increased cloudiness. This study is an effort to better understand the dynamics of TDF within the framework of the Mexican flux (MexFlux) community and the high diversity of Mexican ecosystems. Key Points: Vegetation dynamics in near coastal tropical dry forests of the northern Yucatan Peninsula are modulated by seasonal rainfall and its legacy on groundwater rechargeAn average precipitation threshold marks a transition from water limited to energy‐limited conditions on ecosystem productivityThe ecosystem acts as a CO2 sink with an interannual variability responding to groundwater access and CO2 releases at the rainy season onset [ABSTRACT FROM AUTHOR]

Woody plant encroachment is a global phenomenon whereby shrubs or trees replace grasses. The hydrological consequences of this ecological shift are of broad interest in ecohydrology, yet little is known of how plant and intercanopy patch dynamics, distributions, and connectivity influence catchment‐scale responses. To address this gap, we established research catchments in the Sonoran and Chihuahuan Deserts (near Green Valley, Arizona and near Las Cruces, New Mexico, respectively) that represent shrub encroachment in contrasting arid climates. Our main goals in the coordinated observations were to: (a) independently measure the components of the catchment water balance, (b) deploy sensors to quantify the spatial patterns of ecohydrological processes, (c) use novel methods for characterizing catchment properties, and (d) assess shrub encroachment impacts on ecohydrological processes through modelling studies. Datasets on meteorological variables; energy, radiation, and CO2 fluxes; evapotranspiration; soil moisture and temperature; and runoff at various scales now extend to nearly 10 years of observations at each site, including both wet and dry periods. Here, we provide a brief overview of data collection efforts and offer suggestions for how the coordinated datasets can be exploited for ecohydrological inferences and modelling studies. Given the representative nature of the catchments, the available databases can be used to generalize findings to other catchments in desert landscapes. [ABSTRACT FROM AUTHOR]

Abstract: The hydrology and productivity of the ecosystems of the Yucatan Peninsula (YP) are highly constrained by two factors: (a) the lack of surface drainage networks due to the existence of a highly permeable and connected karstic aquifer roughly the size of the peninsula and (b) a climatic gradient that leads to a transition from seasonally dry deciduous and sub‐deciduous tropical forests, in the north‐western and central parts of the Peninsula, to evergreen forests, in the southern and eastern parts. As a result, surface water fluxes of the YP are restricted to evapotranspiration (ET) that are tightly coupled to ecosystems health and gross primary productivity (GPP). The magnitude and seasonal variation of these fluxes are sensitive to climatic variability and perturbations caused by extreme events such as droughts and tropical storms that are frequent in the YP. In this study, we assess the spatio‐temporal dynamics of ET and GPP above average dry and wet conditions through time series analyses of 15 years of remotely sensed data from both Moderate Resolution Imaging Spectroradiometer and Tropical Rainfall Measuring Mission satellite products. Our results show that ET and GPP follow a regional moisture and temperature gradient that highly controls the distribution of ecosystems within the peninsula. We observe that ET and GPP are in phase with the rainy season in the deciduous forests, but for the evergreen forests, only the GPP is in phase. Additionally, and with the exception of droughts on deciduous ecosystems of the northern part of the YP, the productivity of these ecosystems shows a legacy effect, responding more to a defined trajectory (wetting or drying on the previous years), rather than to punctual extreme climatic events. This has implications on the resilience of these ecosystems to natural perturbations of climate. Comparisons between deciduous and evergreen forest indicate that both types of ecosystems have different plant water use strategies in response to hydrologic variability. [ABSTRACT FROM AUTHOR]

Seasonal vegetation changes during the North American monsoon play a major role in modifying water, energy, and momentum fluxes. Nevertheless, most models parameterize plants as a static component or with averaged seasonal variations that ignore interannual differences and their potential impact on evapotranspiration ( ET) and its components. Here vegetation parameters derived from remote sensing data were coupled with a hydrologic model at two eddy covariance (EC) sites with observations spanning multiple summers. Sinaloan thornscrub (ST) and Madrean woodland (MW) sites, arranged at intermediate and high elevations along mountain fronts in northwest Mexico, occupy specific niches related to climate conditions and water availability that are poorly understood. We found that simulations with a dynamic representation of vegetation greening tracked well the seasonal evolution of observed ET and soil moisture ( SM). A switch in the dominant component of ET from soil evaporation ( E) to plant transpiration ( T) was observed for each ecosystem depending on the timing and magnitude of vegetation greening that is directly tied to rainfall characteristics. Differences in vegetation greening at the ST and MW sites lead to a dominance of transpiration at ST ( T/ ET = 57%), but evaporation-dominant conditions at MW ( T/ ET = 19%). Peak transpiration occurred at 5 and 20 days after the full canopy development in the ST and MW sites, respectively. These results indicate that evapotranspiration timing and partitioning varies considerably in the two studied ecosystems in accordance with different modes of vegetation greening. Intermediate-elevation ecosystems follow an intensive water use strategy with a rapid and robust transpiration response to water availability. In contrast, higher elevation sites have delayed and attenuated transpiration, suggesting an extensive water use strategy persisting beyond the North American monsoon. [ABSTRACT FROM AUTHOR]

Abstract: Remote sensing can allow a more efficient irrigation water management by applying the water when crops require it or when symptoms of water stress appear. In this study, the spatial and temporal distribution of the water deficit index (WDI) and crop evapotranspiration (ET) in wheat were determined through analysis of satellite-based remote sensing images in the Yaqui Valley, Sonora, México. We utilize an empirical model based on the canopy temperature–vegetation cover relationship methodology known as the Moran''s trapezoid. We analyze and discuss the spatial and temporal distributions of WDI and ET at the regional and local scales. Results show a linear relationship (R 2 =0.96) between the values of WDI and the number of days elapsed since the last irrigation. The water deficit index could be utilized to estimate the quantity of available water in wheat and to know the degree of stress presented by the crop. Advantages offered by this methodology include obtaining WDI and evapotranspiration values in zones with partial or null vegetation cover and for large irrigation schemes lacking the necessary data for traditional water management. [Copyright &y& Elsevier]

Non-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, and are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely sensed biomass products and are undersampled by in situ monitoring. Current global change threats emphasize the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we developed and deployed a new protocol for photogrammetric height using unoccupied aerial vehicle (UAV) images to test its capability for delivering standardized measurements of biomass across a globally distributed field experiment. We assessed whether canopy height inferred from UAV photogrammetry allows the prediction of aboveground biomass (AGB) across low-stature plant species by conducting 38 photogrammetric surveys over 741 harvested plots to sample 50 species. We found mean canopy height was strongly predictive of AGB across species, with a median adjusted R 2 of 0.87 (ranging from 0.46 to 0.99) and median prediction error from leave-one-out cross-validation of 3.9%. Biomass per-unit-of-height was similar within plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1-10 ha among, plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1-10 ha -1 . Photogrammetric approaches could provide much-needed information required to calibrate and validate the vegetation models and satellite-derived biomass products that are essential to understand vulnerable and understudied non-forested ecosystems around the globe., (© 2021 The Authors. Remote Sensing in Ecology and Conservation published by John Wiley & Sons Ltd on behalf of Zoological Society of London.)