Obligate seeding plants—those that are killed by fire and whose persistence depends on soil-stored seedbanks—may be particularly susceptible to indirect effects of habitat loss and fragmentation. Especially for rare species, fragmentation can create conditions that reduce the likelihood of achieving sufficient seed bank stores due to changes in the interactions of the remaining plants with their pollinators or their natural enemies such as herbivores or seed predators. Arctostaphylos morroensis (Morro Manzanita) is an endemic obligate seeder whose distribution has been reduced greatly to a small portion of coastal California in habitat that is fragmented by development. We examined the reproductive ecology of A. morroensis to determine the factors that affect seed input to the soil seed bank. In stands of different ages and percent cover of Morro Manzanita, we observed insect pollinators, and measured flower and fruit production, and rates of fruit predation over two years, hypothesizing that, based on previous literature on obligate-seeders, fruit set should be relatively high across all stands, fruit set should be resource-limited, and seed input should be relatively high. Our observations suggest that A. morroensis reproduction is dependent on pollinators, which were primarily bees. Contrary to our predictions, we found that fruit set was relatively low (averaging 10–18% over both years) at all stands and appears to be pollinator-limited. Fruit predation rates were high, with the majority of fruits in experimental trays removed in a matter of weeks. We suspect that seed input in this rare species is strongly limited by low fruit set and high seed predation.
Photovoltaic solar power generating facilities are proliferating rapidly in California and elsewhere. While this trend is welcomed for many reasons (e.g., reducing greenhouse gas emissions), these facilities also can have profound environmental impacts, particularly to local species populations. These impacts become more significant when species of conservation concern are affected. In the San Joaquin Desert region in central California, a number of conservation measures have been routinely implemented on solar facilities, and these measures have facilitated continued use of the facilities by a number of species of conservation concern. Some of the more significant measures include permeable security fences, vegetation management, movement corridors, avoiding critical features such as dens and burrows, and vehicle speed limits. Detailed studies have been conducted on San Joaquin kit foxes (Vulpes macrotis mutica) using solar facilities in the San Joaquin Desert. Demographic and ecological attributes of foxes are similar between foxes using the facilities and foxes on nearby reference sites, and values for foxes on solar sites are within the ranges of values for foxes reported from sites within core population areas. Facilitated by the conservation measures, kit foxes are using at least six facilities in the San Joaquin Desert as are a variety of other species of conservation concern. This successful model also potentially could be adapted to other ecosystems and applied to facilities in regions outside of the San Joaquin Desert, such as the Mojave Desert. Determining whether species in other regions can use photovoltaic solar facilities and identifying the most efficacious conservation measures will require time and testing, and these efforts would benefit from collaborative efforts among landowners, solar developers, natural resources agencies, researchers, and others. The San Joaquin Desert facilities and a recent demonstration facility in the Mojave Desert provide strong evidence that solar facilities can be constructed and operated in a manner that also accommodates continued use of the facilities by some species of conservation concern.
Livestock obtain forage by grazing on rangeland. In California annual rangelands, residual dry matter is commonly used to determine proper grazing levels. Rangeland forage biomass and quality can degrade dramatically during the dormant summer period. We examined 25 sites across an annual rainfall gradient (183-492 mm) over 3 contrasting rainfall yr (2015-2017) that varied from 57% to 152% of average annual precipitation. Overall fractional biomass loss was 54.4% (range = 46.5-61.5%) with greater fractional losses occurring in dry years. Biomass losses were related to the amount of peak standing crop and plant composition-both a function of annual precipitation. Fractional seasonal losses from the peak standing biomass in 2015 = 962 kg/ha (61.5% seasonal; 9.7% monthly), 2016 = 1 541 kg/ha (55.0% seasonal; 8.7%monthly) and 2017 = 1 923 kg/ha (46.5% seasonal; 7.3%, monthly). Forage quality metrics were strongly affected by summer weathering processes. Crude protein concentrations decreased by 33.6%, 27.7%, and 21.0% in 2015, 2016, and 2017, respectively. In contrast, relative concentrations of fiber and lignin (acid detergent fiber [ADF] = cellulose + lignin) and in the weathered biomass showed increases for ADF: 44.6% (2015), 32.2% (2016), and 24.1% (2017). Increased lignin varied: 3.4% in 2015, 23.9% in 2016, and 28.0% in 2017. While ADF and lignin concentrations (weathered biomass, kg/ha) increased during the weathering process, the standing stock decreased by 39.3% (ADF) and 46.6% (lignin), compared with overall weathered biomass loss of 54.4% and CP loss of 67.1%. The significant loss of aboveground biomass and forage quality as weathering processes occurred throughout the dry summer period affects livestock grazing strategies. Forage biomass and nutrient losses through the dry season should be considered when determining grazing strategies to achieve proper residual dry matter levels and nutrient supplementation regimes before the onset of the rainy season. (C) 2021 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
Golden Eagles (Aquila chrysaetos) have been identified as a potential predator of endangered San Joaquin kit foxes (Vulpes macrons mutica), but only one case of such predation has been confirmed. In a recent study on San Joaquin kit foxes, we documented 6 cases of putative predation by Golden Eagles on kit foxes and provided our evidence for each. Golden Eagle predation on kit foxes is most likely to occur in the spring when kit foxes and their pups are frequently aboveground during the day. Such predation is more likely to occur around the margins of the San Joaquin kit fox range, where suitable kit fox habitat abuts suitable nesting habitat for Golden Eagles.
We use climatic conditions that are associated with known monarch butterfly overwintering groves in California to build a Maxent model, and focus on the fine scale probability of overwintering grove occurrence in a topographically complex region of the state (Santa Barbara County). Grove locations are known from recent and historical surveys and a long-term citizen science database. The climatic niche model performs well, predicting that overwintering habitat is most likely to occur along the coast and at low elevations, as shown by empirical data. We then use climatic variables in conjunction with climate change scenarios to model the future location of overwintering habitat, and find a substantial shift in the predicted distribution. Under a plausible scenario, the probability of occurrence of overwintering habitat directly reflects elevation, with coastal regions having a reduced probability relative to today, and higher elevation sites increasing in probability. Under a more extreme scenario, high probability sites are only located along ridgelines and in mountaintop regions of the county. This predicted shift in distribution is likely to have management implications, as sites that currently lack monarchs may become critical to conservation in the future. Our results suggest that estimating the size of the western overwintering population in the future will be problematic, unless annual counts compensate for a shift in the distribution and a potential change in the number and location of occupied sites.