This paper investigates water repellency and soil moisture under 4 different Eucalyptus globulus plantations in Portugal. On 8 occasions over a 16-month period, measurements were made at 3 depths (surface, 0.10 and 0.20 m) at 60 points on four 10 by 18 m grids. The main results are: (i) at all sites and depths, spatial frequency of repellency (defined as percentage of repellent grid points) followed a moisture-related seasonal cycle, its amplitude being greatest for the longest established site, where surface repellency was contiguous in dry late-summer conditions, but was entirely absent after wet winter conditions; (ii) at a few points at 2 sites, repellency persisted during winter; (iii) repellency severity was dichotomously distributed regardless of season (i.e. soils were generally either wettable or highly repellent); and (iv) at the longest established site, when soil moisture was 27% soils were wettable. This may either support the existence of a ‘transition zone’, or be an artefact of the different scales of repellency and soil moisture assessments. Reasons for the observed changes in repellency and their relationship with soil moisture and antecedent rainfall are explored and soil hydrological implications discussed.

In addition to the incineration of vegetation and litter layer, fires are also responsible for the formation of a water repellent layer with significantly different severity and spatial distribution patterns following different burning intensities. Those spatial distribution patterns have an enormous influence on soil wetting patterns, and on hydrological processes at different scales. This study attempts to understand the role of water repellence severity and spatial distribution patterns on soil, slope, and catchment water processes, and on the transmission of hydrological processes between different scales. The comparison between microplot (0.24 m2), plot (16 m2), and catchment (<1.2 km2) scales shows that water repellence spatial homogeneity enhances water fluxes transfer between the different scales. In fact, the more intense the fires, the more severe and spatially uniform the soil water repellency became. For burned areas with heterogeneous soil water repellency, overland flow produced in water repellent patches infiltrated downslope at hydrophilic sites, thereby reducing superficial water fluxes at wider scales. For the more severe and homogeneous water repellent areas following forest wildfires, overland flow was enhanced downslope, increasing fast superficial water fluxes at wider scales.

The present paper studies the hydrological implications of forest fire and the associated export of nutrients as solutes at the micro-plot, plot and catchment scales immediately after fire. The use of three different spatial scales provides improved insights into the mechanisms that drive hydrological and solute movement processes as they change with time following forest fire. Rainfall simulations were performed for 1 h, right after forest fires. Plots were monitored during and after rainfall events, and catchments were instrumented continuously with water level recorders. Samples were collected weekly to determine some of the main nutrients present over a period of 14 months. At all scales, the main hydrological processes were assessed and samples collected for chemical analysis. Measurements were made at burned Pinus pinaster locations in the central region of Portugal. These are ordinarily placed in poor, shallow Humic Cambisol soils located in steep slopes. The results show that there was a rapid and widespread export of nutrients during the first 4 months following the wildfire. The amount of nutrients lost decreased gradually over those 4 months in response to the exhaustion of the ash source. After this period, nutrient peak losses occurred only in response to extreme rainfall events.

Fire induces important changes in vegetation and soil structure, which can have major impacts on overland flow generation processes, runoff amounts and erosion yields. This paper presents the results of an investigation into the impact of different fire intensities on water, sediment and solute yields. Wildfire, prescribed fire and experimental fire impacts were investigated at two scales: (1) a temporary circular bounded plot of 0.24 m ² (rainfall simulation plot); (2) a permanent bounded runoff plot of 16 m ² (natural rainfall conditions). In addition, the spatial patterns of the soil water repellency, vegetation, litter cover and stone cover for each land use and fire intensity were assessed using a transect system.The results of this study show a significant difference in the spatial distribution patterns of soil water repellency. Wildfire sites were characterized by more intense and by more spatially contiguous repellency than the experimental and prescribed fire sites. These differences have important effects on overland flow generation processes and runoff amounts. At the prescribed and experimental fire sites, the discontinuous distribution of repellency provides greater potential for water to infiltrate via non-repellent soils, whereas there are far fewer infiltration pathways at the wildfire sites because of their spatially contiguous repellency. This spatial discontinuity (alternation between hydrophobic and hydrophilic soil patches) is therefore responsible for the lower overland flow amounts, smaller erosion rates and nutrient yields at broader scales, when compared with the wildfire burned areas where soil water repellence is more intense and spatially contiguously distributed.

Water is crucial for enduring horticultural productivity, but high water-use requirements and declining water supplies with the changing climate challenge economic viability, environmental sustainability, and social justice. While the scholarly literature pertaining to water management in horticulture abounds, knowledge of practices and technologies that optimize water use is scarce. Here, we review the scientific literature relating to water requirements for horticulture crops, impacts on water resources, and opportunities for improving water- and transpiration-use efficiency. We find that water requirements of horticultural crops vary widely, depending on crop type, development stage, and agroecological region, but investigations hitherto have primarily been superficial. Expansion of the horticulture sector has depleted and polluted water resources via overextraction and agrochemical contamination, but the extent and significance of such issues are not well quantified. We contend that innovative management practices and irrigation technologies can improve tactical water management and mitigate environmental impacts. Nature-based solutions in horticulture—mulching, organic amendments, hydrogels, and the like—alleviate irrigation needs, but information relating to their effectiveness across production systems and agroecological regions is limited. Novel and recycled water sources (e.g., treated wastewater, desalination) would seem promising avenues for reducing dependence on natural water resources, but such sources have detrimental environmental and human health trade-offs if not well managed. Irrigation practices including partial root-zone drying and regulated deficit irrigation evoke remarkable improvements in water use efficiency, but require significant experience for efficient implementation. More advanced applications, including IoT and AI (e.g., sensors, big data, data analytics, digital twins), have demonstrable potential in supporting smart irrigation (focused on scheduling) and precision irrigation (improving spatial distribution). While adoption of technologies and practices that improve sustainability is increasing, their application within the horticultural industry as a whole remains in its infancy. Further research, development, and extension is called for to enable successful adaptation to climate change, sustainably intensify food security, and align with other Sustainable Development Goals.