Quantifying evapotranspiration is critical to accurately predict vegetation health, groundwater recharge, and streamflow generation. Hillslope aspect, the direction a hillslope faces, results in variable incoming solar radiation and subsequent vegetation water use that influence the timing and magnitude of evapotranspiration. Previous work in forested landscapes has shown that equator-facing slopes have higher evapotranspiration due to more direct solar radiation and higher evaporative demand. However, it remains unclear how differences in vegetation type (i.e., grasses and trees) influence evapotranspiration and water partitioning between hillslopes with opposing aspects. Here, we quantified evapotranspiration and subsurface water storage deficits between a pole- and equator-facing hillslope with contrasting vegetation types within central coastal California. Our results suggest that cooler pole-facing slopes with oak trees have higher evapotranspiration than warmer equator-facing slopes with grasses, which is counter to previous work in landscapes with singular vegetation types. Our water storage deficit calculations indicate that the pole-facing slope has a higher subsurface storage deficit and a larger seasonal dry down than the equator-facing slope. This aspect difference in subsurface water storage deficits may influence subsequent deep groundwater recharge and streamflow generation. In addition, larger root-zone storage deficits on pole-facing slopes may reduce their ability to serve as hydrologic refugia for oaks during periods of extended drought. This research provides a novel integration of field-based and remotely-sensed estimates of evapotranspiration required to properly quantify hillslope-scale water balances. These findings emphasize the importance of resolving hillslope-scale vegetation structure within Earth system models, especially in landscapes with diverse vegetation types.

Glasshouse films with adjustable light transmittance have the potential to reduce the high energy cost for greenhouse horticulture operations. Whether these films compromise the quantity and quality of light transmission for photosynthesis and crop yield, remains unclear. A “Smart Glass” film ULR-80 (SG) was applied to a high-tech greenhouse horticulture facility and two experimental trials were conducted by growing eggplant () using commercial vertical cultivation and management practices. SG blocked 85% of ultraviolet (UV), 58% of far-red, and 26% of red light, leading to an overall reduction of 19% in photosynthetically active radiation (PAR, 380 - 699 nm) and a 25% reduction in total season fruit yield. There was a 53% (season mean) reduction in short-wave radiation (385 nm to 2105 nm upward; 295 to 2685 nm downward) that generated a net reduction in heat load and water and nutrient consumption that improved energy and resource use efficiency. Eggplant adjusted to the altered SG light environment via decreased maximum light-saturated photosynthetic rates () and lower xanthophyll de-epoxidation state. The shift in light characteristics under SG led to reduced photosynthesis, which may have reduced source (leaf) to sink (fruit) carbon distribution, increased fruit abortion and decreased fruit yield, but did not affect nutritional quality. We conclude that SG increases energy and resource use efficiency, without affecting fruit quality, but the reduction in photosynthesis and eggplant yield is high. The solution is to re-engineer the SG to increase penetration of UV and PAR, while maintaining blockage of glasshouse heat gain.