We studied the link between carbon and water fluxes to understand the response of net ecosystem carbon exchange (NEE) to water availability conditions of three different potato water regimes cropping systems [full irrigation (FI), deficit irrigation (DI) and rainfed (RF)]. Through the eddy covariance technique, we measured CO₂ and water vapor exchanges and determined surface resistances, omega factor, and inherent water use efficiency (IWUE). Additionally, continuous plant growth determinations of leaf area index (LAI) and specific leaf area (SLA) were made over the three cropping systems. The RF potato was a net carbon source (NEE = 187.21 ± 3.84 g C m⁻²), while both, FI (NEE= −311.96 ± 12.82 g C m⁻²) and DI (−17.3 ± 4.6 g C m⁻²) were a net carbon sink. Greater sink activity is due to high fluxes of gross primary productivity (GPP) [where the GPP > ecosystem respiration (R_eco)] and evapotranspiration (ET), and the high efficiency in the exchange of carbon and water. Without water limitations, the larger canopy, with greater photosynthetic activity (GPP/R_eco > 2) as well as with low internal resistance offers a greater area for water and carbon exchange, and the highly coupled and synchronized ET – GPP fluxes are primarily controlled by the radiative environment. The lower sink capacity of the DI potato crop and the carbon source activity from the RF, are consequences of a smaller area for water and carbon exchange due to the smaller canopy, and a low IWUE from decoupled and desynchronized carbon and water exchange caused by unbalanced restrictions on ET and GPP fluxes. Specifically, at DI potato, ET remained at a high rate, while GPP was reduced by means of non-stomatal limitations. In the rainfed potato, vapor pressure deficit (VPD) played a significant role increasing midday canopy resistance (Rc) up to 13 times compared to irrigated sites, when VPD was around 0.8 kPa. In consequence, ET and GPP fluxes decreased together, but GPP decreased more than ET because of stomatal and non-stomatal limitations.

The current communication presents the application of a consolidated model combination strategy to analyze the medium-term carbon fluxes in two Mediterranean pine wood ecosystems. The modelling strategy is based on the use of a NDVI-driven parametric model, Modified C-Fix, and of a bio-geochemical model, BIOME-BGC, the outputs of which are combined taking into account the actual development phase of each ecosystem. The two pine ecosystems examined correspond to an old-growth forest and to a secondary succession after clearcuts, which differently respond to the same climatic condition during a ten-year period (2013-2022). Increasing dryness, in fact, exerts a fundamental role in controlling the gross primary and net ecosystem production of the mature stand, while the effect of forest regeneration is prevalent for the uprising of the same variables in the other stand. In particular, the simulated net carbon exchange fluctuates around 200 g C m-2 year-1 in the first stand and rises to over 600 g C m-2 year-1 in the second stand; correspondingly, the accumulation of new biomass is nearly undetectable in the former case while becomes notable in the latter. The study therefore supports the potential of the applied strategy for predicting the forest carbon balances consequent on diversified natural and human-induced factors.

Drought poses a significant environmental risk and can deeply affect the growth of grasslands. However, there is still uncertainty regarding the precise impact of varying levels of drought on grassland growth. To address this gap, we utilized several key indicators, including the Nor-malized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), the Global Or-biting Carbon Observatory-2 based Solar-induced Chlorophyll Fluorescence (GOSIF), and the Gross Primary Productivity (GPP), in conjunction with drought indices (the Standardized Precip-itation Evapotranspiration Index (SPEI) and the soil moisture (SM). Our study aimed to compre-hensively assess the consistency of spatio-temporal patterns in grassland vegetation and its re-sponsiveness to different drought levels in the Inner Mongolia region from 2002 to 2020. Results indicated that NDVI, EVI, GOSIF, and GPP in grassland vegetation across Inner Mongolia exhibited significant increasing trends from 2002 to 2020. Specifically, NDVI, EVI, GOSIF, and GPP all dis-played consistent spatial patterns, with 25.83%, 21.18%, 22.65% and 48.13% of the grassland area showing significant increases, respectively. Drought events, as described by SPEI and SM, in June 2007 to September 2007 and June 2017 to July 2017, were selected to evaluated the response of grassland vegetation to drought. The drought events of 2007 and 2017 resulted in reductions in NDVI, EVI, GOSIF, and GPP relative to multi-year average (2002-2020). GOSIF exhibited a more intense response to drought, suggesting that GOSIF may reflect the inhibition of water stress on grassland photosynthesis better than NDVI and EVI during drought in 2007 and 2017. The reduc-tions in NDVI, EVI, GOSIF and GPP in grassland increased significantly across different drought-levels, with the sharpest reductions observed during extreme drought. Under the severe and extreme drought events, the most substantial reductions in NDVI, EVI, GOSIF, and GPP were observed in the temperate steppe (TS). Moreover, the effects of different drought severity levels within the same grassland type varied, with the most significant reductions in NDVI, EVI, GOSIF and GPP observed during extreme drought. Our results provide new perspectives for developing and implementing effective strategies to address grassland carbon cycling management and climate change in Inner Mongolia.

Low-cost miniature hyperspectral and thermal cameras onboard lightweight unmanned aerial vehicles (UAV) bring new opportunities for monitoring land surface variables at unprecedented fine spatial resolution with acceptable accuracy. This research applies hyperspectral and thermal imagery from a drone to quantify upland rice growth and water use efficiency (WUE) after biochar application in a Costa Rican dry region. The field flights were conducted over two experimental groups with bamboo biochar and sugarcane biochar amendments and one control group without biochar application. Rice canopy biophysical variables were estimated by inversion of a canopy radiative transfer model on hyperspectral reflectance. Variations in gross primary production (GPP) and WUE across treatments were estimated from the normalized difference vegetation index (NDVI), canopy chlorophyll content (CCC), and evapotranspiration. We found that GPP was increased by 41.9±3.4 % when using bamboo biochar and 17.5±3.4 % when using sugarcane biochar, which was probably due to higher soil moisture in the biochar-amended plots and led to significantly higher WUE by 40.8±3.5 % in bamboo biochar and 13.4±3.5 % in sugarcane biochar. This study demonstrated the use of hyperspectral and thermal imagery from drone to provide indicators for quantifying biochar effects on tropical dry cropland by integrating with ground point samples and physical models.