Non-photosynthetic vegetation (NPV) biomass has been identified as a priority variable for upcoming spaceborne imaging spectroscopy missions, calling for a quantitative estimation of lignocellulosic plant material as opposed to the sole indication of surface coverage. Therefore, we propose a hybrid model for the retrieval of non-photosynthetic cropland biomass. The workflow included coupling the leaf optical model PROSPECT-PRO with the canopy reflectance model 4SAIL, which allowed us to simulate NPV biomass from carbon-based constituents (CBC) and leaf area index (LAI). PROSAIL-PRO provided a training database for a Gaussian process regression (GPR) algorithm, simulating a wide range of non-photosynthetic vegetation states. Active learning was employed to reduce and optimize the training data set. In addition, we applied spectral dimensionality reduction to condense essential information of non-photosynthetic signals. The resulting NPV-GPR model was successfully validated against soybean field data with normalized root mean square error (nRMSE) of 13.4% and a coefficient of determination ($R^2$) of 0.85. To demonstrate mapping capability, the NPV-GPR model was tested on a PRISMA hyperspectral image acquired over agricultural areas in the North of Munich, Germany. Reliable estimates were mainly achieved over senescent vegetation areas as suggested by model uncertainties. The proposed workflow is the first step towards the quantification of non-photosynthetic cropland biomass as a next-generation product from near-term operational missions, such as CHIME.

Recognition of invasive species and their distribution is key for managing and protecting native species within both natural and man-made ecosystems. Small woody features (SWF) represent fragmented patches or narrow linear tree features that are of high importance in intensively utilized agricultural landscapes. Simultaneously, they frequently serve as expansion pathways for invasive species such as black locust. In this study, Sentinel-2 products, combined with spatiotemporal compositing approaches, are used to address the challenge of broad area black locust mapping at a high granularity. This is accomplished by conducting a comprehensive analysis of the classification performance of various compositing approaches and multitemporal classification settings throughout four vegetation seasons. The annual, seasonal (bi-monthly), and monthly median values of cloud-masked Sentinel-2 reflectance products are aggregated and stacked into varied time-series datasets per given year. The random forest algorithm is trained and output classification maps validated based on field-based reference datasets across Danubian lowlands (Slovakia). The main results of the study proved the usefulness of spatiotemporal compositing of Sentinel-2 products for mapping black locust in small woody features across wide area. In particular, temporally aggregated monthly composites stacked to seasonal time series datasets yielded consistently high overall accuracies ranging from 89.10% to 91.47% with balanced producer’s and user’s accuracies for each year’s annual series. We presume that a similar approach could be used for a broader scale species distribution mapping, assuming they are spectrally or phenologically distinctive, as is often the case for many invasive species.

Soil respiration (Rs) is a key component of the forest carbon cycle, yet the impacts of Ailanthus altissima invasion on Rs, temperature sensitivity (Q10), and underlying drivers remain unstudied in temperate forests. This study quantified soil respiration, seasonal dynamics, and environmental sensitivity in an Ailanthus-invaded forest compared to an adjacent native forest within 30 field campaigns across 40 points over a one-year period. Directly measured field Rs was 37% higher in the native forest than the Ailanthus stand. Modeled annual cumulative Rs was 62% higher in the native forest, with the posterior difference marginally including zero (p = 0.051). Q10 values were nearly identical (1.52 vs. 1.49). Environmental drivers regulated Rs differently: Ailanthus showed joint regulation by temperature, moisture, and their interaction, whereas the native forest showed independent responses. However, smooth term comparisons confirmed distinct daily Rs dynamics between stands, reflecting different carbon allocation strategies. Laboratory basal respiration was significantly higher under Ailanthus in the late summer, indicating that the native forest's higher field Rs reflects a larger autotrophic root contribution rather than higher heterotrophic potential. These findings indicate that A. altissima invasion did not increase soil CO2 efflux. As A. altissima continues to expand its global range, its shifting belowground carbon dynamics, high net photosynthetic rate, and drought tolerance collectively drive complex alterations to the forest carbon cycle. These multifaceted impacts underscore the necessity of moving beyond a uniform-threat perspective in forestry management and control planning.

The study of global changes impact on natural ecosystems is one of the current priorities of ecological research due to their recent scale and speed. Alpine grasslands are sensitive ecosystems well-suited for investigating how ecosystem is responding to rapid environmental change. With aim to investigate the impact of increased temperature and nitrogen input on the structure and processes in an alpine ecosystem we established in 2009 a field experiment on Mt. Kráľova hoľa in Central Slovakia (https://deims.org/61c12307-2669-46c1-bf0b-94d40cc6b111). Four treatments were used: increased temperature (T), increased nitrogen input (N), combined increased temperature and nitrogen input (NT), and control (C). Each treatment included six replicates (24 plots total) arranged in a blocked design. Nitrogen addition (10 kg N ha⁻¹ yr⁻¹) was applied as NH₄NO₃ solution in five applications during the growing season, while temperature was raised using open-top chambers (OTCs) designed following ITEX standards. The research plots were established in typical, species-poor, two-layer vegetation of the subalpine zone on silicate bedrock within the Juncion trifidi alliance. Experimental manipulation of temperature and nitrogen input in permanent plots in Mt. Kráľova hoľa showed a differentiated effect of individual treatments on the biomass and structure of the plant community of alpine grasslands. The results show that both nitrogen and temperature increase significantly boosted aboveground biomass. Nitrogen addition (N) has been found to benefit mainly graminoids like Avenella flexuosa and Festuca supina, while dwarf shrubs and mosses experienced moderate biomass increases. The NT treatment resulted in further amplification of graminoid biomass, where Luzula alpinopilosa and Juncus trifidus became dominant, leading to suppression of other functional groups: it may inhibit the growth of dwarf scrub and mosses and results in lichens elimination. In contrast, warming alone (T) yielded the highest overall biomass, driven by the growth of dwarf shrubs, mosses, and lichens, even though graminoids responded modestly. These findings align with global patterns, where dominant species and functional groups play a major role in stabilizing ecosystems under changing conditions. The control treatment shows lower overall biomass than any other treatment, indicating that the experimentally increased temperature and/or nitrogen input improves environmental conditions for plant growth. The Redundancy analysis (RDA) of vegetation records shows that the control treatment (C) is closely correlated with the increased temperature treatment (T). The remaining two treatments, i.e. N- and NT treatments are negatively correlated with two former treatments. Species Avenella flexuosa, Festuca supina, Carex bigelowii and Polytrichum alpinum are positively correlated with added nitrogen treatment (N). The positive correlation with combined NT treatment exhibit Luzula alpinopilosa, Juncus trifidus, and Senecio carpaticus, while other species are negativelly correlated: Homogyne alpina, Hieracium alpinum, Cladonia spp. Species Cetraria islandica, Hypnum sp., Soldanella hungarica, Campanula alpina, Oreogeum montanum, Potentilla aurea, and Nardus stricta, are correlated with C- and T-treatments and these species are most affected by N addition. The ecosystem likely did not utilize all of the added nitrogen, with some leaching into the soil solution, as evidenced by increases in both nitrate and ammonium nitrogen in the lysimeter water. The addition of nitrogen decreased soil pH, with acidic soils becoming even more acidic, and decreased the exchange capacity of ions. There was an increase in the conductivity of lysimeter waters, indicating the leaching of ions from soil particles into the soil solution. We confirmed the leaching of basic cations calcium, magnesium, phosphorus, and potassium into the soil solution, as well as increased concentrations of aluminium, manganese, and zinc. The increase in dissolved organic carbon in the treatments with increased temperature suggests higher decomposition. The study highlights how nitrogen addition can alter community structure, including through shading effects caused by fast-growing graminoids. Understanding these interactions is key for the effective management of alpine grasslands, which face growing risks from climate change and human-driven nitrogen deposition.

Alpine grasslands belong among highly sensitive ecosystems where nutrient deposition can affect significantly soil chemistry, water quality, and vegetation dynamics and structure. To study responsiveness of alpine grassland ecosystems to increased inputs of nitrogen (N) and phosphorus (P) experimental plots were established in 2002 on an eLTER site Jalovecká dolina, Slovakia (https://deims.org/e13f1146-b97a-4bc5-9bc5-65322379a567). Since then, experimental plots have been fertilized by solution of 2, 6 and 15 g N.m².year^-1 in a form of NH₄NO₃ and by solution of 5 g P. m².year^-1 in a form of KH₂PO₄. A control has been sprayed by water of the same amount. Experimental solutions are applied three times per year during summer months. All treatments were established in five replicates. In 2009, all plots were dievided on halves, ones are still fertilized and second ones were left for recovery. Soils at the site are humic ferruginous podzols, derived from biotite granodiorite parent material with very low pH/H₂O around 3.5. Vegetation at the site belongs to the Juncion trifidi Krajina 1933 alliance and it is dominated by graminoid species, including Oreochloa disticha, Festuca supin a, Agrostris rupestris, Carex bigelowii, Juncus trifidus , and Avenella flexuosa, with lower cover of forb and dwarf shrub species, but significant layer of lichens dominated by Cetraria islandica. After 6 years of experiment we showed (Bowman et al. 2008) that increases in nitrogen deposition in the region result in a depletion of both base cations and soluble aluminium, and an increase in extractable iron concentrations. In conjunction with this, we observe a nitrogen deposition-induced reduction in the biomass of vascular plants, associated with a decrease in shoot calcium and magnesium concentrations. We suggest that this site, and potentially others in central Europe, have reached a new and potentially more toxic level of soil acidification in which aluminium release is superseded by iron release into soil water. After 20 years of experimental N and P enrichments and 13 years of recovery were done chemical analyses of soil and soil water. Chemical analyses of plant biomass will be done in near future. Soils at the site are humic ferruginous podzols, derived from biotite granodiorite parent material with very low pH/H₂O around 3.5. Comparing fertilized to recovery plots revealed that the soil and soil water pH increased only very little. The pools of NO₃^- and NH₄⁺ in soil water decreased in N recovery plots, but remained higher than in P and C plots. Soil exchangeable metals Al³⁺ and Fe²⁺ decreased slightly in N recovery plots, but Mn²⁺ elevated. Content of soil base cations Ca²⁺, Mg²⁺ and K⁺, except Na⁺, elevated in all treatment and control. The effect of increased N and P treatments on vegetation pointed out that herbs and mosses biomass significantly decrease under N15 and P (Kruskal-Wallis p < 0.001), while total biomass was notably enhanced under the P treatment (p < 0.001). Grass, bushes, mosses and lichens displayed limited responses, reflecting their slower growth rates and nutrient uptake capacities. In summary, the results demonstrate that N and P nutrient enrichment in acid alpine grasslands enhance plant productivity for fast-growing species like herbs, halt the sensitive species like lichens, and affect soil and water nutrient cycling and quality with potential for long-lasting impacts on ecosystem structure and function.