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Fire is crucial for maintaining species diversity and resilience in fire‐adapted shrublands of the world's Mediterranean climate zones (MCZs), which include the chaparral shrublands of the North American MCZ. Chaparral is adapted to high‐intensity burning, with relatively long intervals between fires (30–100 years) typifying undegraded conditions. Modern fire frequencies are much higher in chaparral, driven largely by high densities of human ignitions and coincidence between ignitions and severe weather conditions. This change in the fire regime has major implications for biodiversity, leading to exotic invasion, decreased ecosystem services, and potential type conversion of shrubland to grassland dominated by exotic species. We studied the impact of increased fire frequencies on the composition and abundance of herbaceous and woody species in the Interior Coast Range of northern California. Our study area is one of the most frequently burned areas in California, which allowed us to investigate higher fire frequencies than previously published in the scientific literature for California. We surveyed fifty‐four 250‐m2 plots to assess changes in plant community composition and postfire regeneration of chaparral shrubs across a wide range of fire frequencies, including plots that have burned up to six times in the past 30 years. Our findings reveal that short‐interval fires significantly reduced postfire native woody regeneration, with obligate seeding species experiencing a 99% reduction and facultative species showing an 83% reduction in regeneration in the most frequently burned plots. Moreover, the overall marginal effect of one additional fire since 1985 decreased the proportion of native species cover by 12% and both richness and Shannon diversity by 4%. Consequently, areas with higher fire recurrence supported a more structurally and botanically homogeneous landscape dominated by a homogeneous group of non‐native species. [ABSTRACT FROM AUTHOR]

Premise: To survive climate change and habitat loss, plants must rely on phenotypic changes in response to the environment, local adaptation, or migration. Understanding the drivers of intraspecific variation is critical to anticipate how plant species will respond to climate change and to inform conservation decisions. Here we explored the extent of local adaptation and phenotypic plasticity in Heteromeles arbutifolia, toyon, a species endemic to the California Floristic Province. Methods: We collected leaves from 286 individuals across toyon's range and used seeds from 37 individuals to establish experimental gardens in the northern and southern parts of toyon's range. We measured leaf functional traits of the wild‐collected leaves and functional and fitness traits of the offspring grown in the experimental gardens. We then investigated the relationships between traits and source environment. Results: Most traits we investigated responded plastically to the environment, and some traits in young seedlings were influenced by maternal effects. We found strong evidence that variation in leaf margins is a result of local adaptation to variation in temperature and temperature range. However, the source environment was not related to fitness traits or survival in the experimental gardens. Conclusions: Our findings reiterate the adaptive role of toothed leaf margins in colder and more seasonally variable environments. Additionally, we provide evidence that fitness of toyon is not dependent on where they are sourced, and thus toyon can be sourced across its range for restoration purposes. [ABSTRACT FROM AUTHOR]

Fire is a common and frequent disturbance in Mediterranean ecosystems, affecting the diversity and dynamics of native bee communities by modifying the distribution and availability of the resources that bees require to forage and nest. Previous studies have found changes in bee diversity depending on the time since the last fire, with increases in species diversity in the early stages postburn.Using a chronosequence of plots with different times since the last fire in the Mediterranean‐climate chaparral of Baja California, Mexico, we estimated changes in overall abundance, richness, diversity and species composition of the native bee community.Bee abundance and richness were higher at recently burned plots and gradually decreased, but Hill–Shannon and Hill–Simpson diversities did not change over the chronosequences. Nearby plots (in the same locality) of different stages were more similar in composition than distant plots (in different localities) of a similar stage, suggesting a spatial correlation. Plant species richness increased after fires. Bare soil was also greater on recently burned patches and may facilitate nesting resources. The number of bees was positively correlated to plant richness.Our results highlight the importance of fire as a natural disturbance structuring the bee community in the Mediterranean chaparral of Baja California.Furthermore, our results are relevant for future conservation plans since fire management (i.e., prescribed fires) could improve conditions for sustaining greater bee richness and abundance. [ABSTRACT FROM AUTHOR]

Abstract Fire is crucial for maintaining species diversity and resilience in fire‐adapted shrublands of the world's Mediterranean climate zones (MCZs), which include the chaparral shrublands of the North American MCZ. Chaparral is adapted to high‐intensity burning, with relatively long intervals between fires (30–100 years) typifying undegraded conditions. Modern fire frequencies are much higher in chaparral, driven largely by high densities of human ignitions and coincidence between ignitions and severe weather conditions. This change in the fire regime has major implications for biodiversity, leading to exotic invasion, decreased ecosystem services, and potential type conversion of shrubland to grassland dominated by exotic species. We studied the impact of increased fire frequencies on the composition and abundance of herbaceous and woody species in the Interior Coast Range of northern California. Our study area is one of the most frequently burned areas in California, which allowed us to investigate higher fire frequencies than previously published in the scientific literature for California. We surveyed fifty‐four 250‐m2 plots to assess changes in plant community composition and postfire regeneration of chaparral shrubs across a wide range of fire frequencies, including plots that have burned up to six times in the past 30 years. Our findings reveal that short‐interval fires significantly reduced postfire native woody regeneration, with obligate seeding species experiencing a 99% reduction and facultative species showing an 83% reduction in regeneration in the most frequently burned plots. Moreover, the overall marginal effect of one additional fire since 1985 decreased the proportion of native species cover by 12% and both richness and Shannon diversity by 4%. Consequently, areas with higher fire recurrence supported a more structurally and botanically homogeneous landscape dominated by a homogeneous group of non‐native species.

Background and Aims The California Floristic Province (CA-FP) is the most species-rich region of North America north of Mexico. One of several proposed hypotheses explaining the exceptional diversity of the region is that the CA-FP harbours myriad recently diverged lineages with nascent reproductive barriers. Salvia subgenus Audibertia is a conspicuous element of the CA-FP, with multiple sympatric and compatible species. Methods Using 305 nuclear loci and both organellar genomes, we reconstruct species trees, examine genomic discordance, conduct divergence-time estimation, and analyse contemporaneous patterns of gene flow and mechanical reproductive isolation. Key Results Despite strong genomic discordance, an underlying bifurcating tree is supported. Organellar genomes capture additional introgression events not detected in the nuclear genome. Most interfertility is found within clades, indicating that reproductive barriers arise with increasing genetic divergence. Species are generally not mechanically isolated, suggesting that it is unlikely to be the primary factor leading to reproductive isolation. Conclusions Rapid, recent speciation with some interspecific gene flow in conjunction with the onset of a Mediterranean-like climate is the underlying cause of extant diversity in Salvia subgenus Audibertia. Speciation has largely not been facilitated by gene flow. Its signal in the nuclear genome seems to mostly be erased by backcrossing, but organellar genomes each capture different instances of historical gene flow, probably characteristic of many CA-FP lineages. Mechanical reproductive isolation appears to be only part of a mosaic of factors limiting gene flow. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the pyrolysis of selected California foliage and estimate the energy content of the released volatiles to show the significance of the pyrolysis of foliage and its role during wildland fires. While the majority of the volatiles released during the pyrolysis of foliage later combust and promote fire propagation, studies on the energy released from combustion of these compounds are scarce. Samples of chamise (Adenostoma fasciculatum), Eastwood's manzanita (Arctostaphylos glandulosa), scrub oak (Quercus berberidifolia), hoaryleaf ceanothus (Ceanothus crassifolius), all native to southern California, and sparkleberry (Vaccinium arboreum), native to the southern U.S., were pyrolyzed at 725 °C with a heating rate of approximately 180 °C/s to mimic the conditions of wildland fires. Tar and light gases were collected and analyzed. Tar from chamise, scrub oak, ceanothus and sparkleberry was abundant in aromatics, especially phenol, while tar from manzanita was mainly composed of cycloalkenes. The four major components of light gases were CO, CO2, CH4 and H2. Estimated values for the high heating values (HHVs) of volatiles ranged between 18.9 and 23.2 (MJ/kg of biomass) with tar contributing to over 80% of the HHVs of the volatiles. Therefore, fire studies should consider the heat released from volatiles present in both tar and light gases during pyrolysis. [ABSTRACT FROM AUTHOR]

In western North America, fire regimes are shifting towards more frequent, larger, and more severe wildfire. There is concern that this will shift the vegetation type in many areas, especially on the lower, drier slopes. In northern California, mature serotinous conifers and resprouting shrub species easily regenerate in severe patches of any size. There is no consensus, however, regarding the effects of shrub competition on conifer recruitment; conifer response to shade varies with shade tolerance and abiotic factors. Many conifers and almost all chaparral shrubs are shade intolerant, and we expect shading to be the main driver of the inter-species competition between these taxa on dry low-elevation, slopes We chose to examine early post-fire regeneration of knobcone pine (Pinus attenuata), a shade intolerant serotinous conifer, because (a) as a serotinous species we could be assured of a high initial density of recruits, and (b) it is mainly found on lower-elevation slopes in a matrix of chaparral. We examined the competitive interactions of the pine and shrubs within the 2018 Carr and Delta fires at the third and fourth post-fire years, as well as at the 2008 Motion Fire at the 14th post-fire year, focusing on two measurements of shrub shading: inter-shrub porosity (% shrub cover) and intra-shrub porosity (species-specific ground-level light availability). Our response variables included recruitment success (recruits per ovulate cone) and growth (height). We only chose stands where knobcone pine was a minor pre-fire component to ensure a high density of vigorously resprouting shrubs. We found (1) there were significantly fewer pine recruits under shrubs, with the bulk of the shrub-induced mortality of knobcone pine occurring before the third growing season; (2) knobcone pine averaged about six established recruits per burned parent tree by the third year following fire; and (3), extrapolating from height reconstruction of post-fire knobcone pine regeneration from the 2008 Motion Fire, the remaining tree recruits are expected to persist and dominate the stand within a decade of the fire. We conclude that competition with shrubs on low elevation sites in northern California does have a negative effect on knobcone pine density but is insufficient to seriously impede a dramatic post-fire increase in conifer density when conifer regeneration arrives promptly following fire.

This document is a correction notice for an article titled "A live fuel moisture climatology in California." The correction addresses errors in the figures and the introduction of the original article. The corrected figures and captions are provided, and the corrected paragraph in the introduction is included. The authors apologize for the errors but state that they do not affect the scientific conclusions of the article. The original article has been updated. [Extracted from the article]

Southern California experienced unprecedented megadrought between 2012 and 2018. During this time, Malosma laurina, a chaparral species normally resilient to single‐year intense drought, developed extensive mortality exceeding 60% throughout low‐elevation coastal populations of the Santa Monica Mountains. We assessed the physiological mechanisms by which the advent of megadrought predisposed M. laurina to extensive shoot dieback and whole‐plant death. We found that hydraulic conductance of stem xylem (Ks, native) was reduced seven to 11‐fold in dieback adult and resprout branches, respectively. Staining of stem xylem vessels revealed that dieback plants experienced 68% solid‐blockage, explaining the reduction in water transport. Following Koch's postulates, persistent isolation of a microorganism in stem xylem of dieback plants but not healthy controls indicated that the causative agent of xylem blockage was an opportunistic endophytic fungus, Botryosphaeria dothidea. We inoculated healthy M. laurina saplings with fungal isolates and compared hyphal elongation rates under well‐watered, water‐deficit, and carbon‐deficit treatments. Relative to controls, we found that both water deficit and carbon‐deficit increased hyphal extension rates and the incidence of shoot dieback. Summary statement: We conclude that the ultimate cause of mortality of Malosma laurina in field populations was megadrought and that the proximal cause of mortality was the transition of endemic Botryosphaeria dothidea to an opportunistic pathogen that amplified protracted water stress through physical blockage of xylem water transport. [ABSTRACT FROM AUTHOR]

Type conversion from native shrubland to invasive annual grassland is on the rise due to global change factors such as prolonged drought and increasing fire frequency. Efforts to restore chaparral ecosystems are limited by current understanding of competitive interactions between shrub seedlings and invasive grasses as well as soil moisture requirements of chaparral seedlings. We set up a restoration experiment where we out‐planted Adenostoma fasciculatum seedlings, manipulated invasive grass density, monitored soil moisture at two depths, and tracked seedling survival and biomass. We found that higher invasive grass cover was associated with higher rates of seedling mortality but found no difference in biomass per surviving plant. Soil moisture was higher at 15 cm under the 100% weeded treatment than the 50% weeded and control treatments during January. Lower invasive cover resulted in higher richness of annual native plant species, as plots with 100% invasive removal had higher richness than 50% removal and unplanted control plots. Future restoration efforts in the chaparral will likely be more successful in increasing initial seedling establishment if invasive grass removal is included. [ABSTRACT FROM AUTHOR]

Arctostaphylos (Ericaceae) species, commonly known as manzanitas, are an invaluable fire-adapted chaparral clade in the California Floristic Province (CFP), a world biodiversity hotspot on the west coast of North America. This diverse woody genus includes many rare and/or endangered taxa, and the genus plays essential ecological roles in native ecosystems. Despite their importance in conservation management, and the many ecological and evolutionary studies that have focused on manzanitas, virtually no research has been conducted on the genomics of any manzanita species. Here, we report the first genome assembly of a manzanita species, the widespread Arctostaphylos glauca. Consistent with the genomics strategy of the California Conservation Genomics project, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises a total of 271 scaffolds spanning 547Mb, close to the genome size estimated by flow cytometry. This assembly, with a scaffold N50 of 31Mb and BUSCO complete score of 98.2%, will be used as a reference genome for understanding the genetic diversity and the basis of adaptations of both common and rare and endangered manzanita species.

Aims: Prolonged fire suppression in conifer forests of the Sierra Nevada Mountain range, California, USA, has led to ingrowth of conifer seedlings, converting the open heterogeneous structure into uniformly dense and layered forest. The threat of a stand‐replacing fire has increased because of fuel buildup in combination with rising drought and extreme heat frequency caused by climate change. With such high severity fire, there is also rising concern regarding conifer forest converting to shrublands as severe fire favors the establishment of large shrub patches altering landscape vegetation pattern and heterogeneity. However, a clear understanding of the effects of increased fire severity, size, and frequency on landscape‐scale heterogeneity and postfire patch dynamics is lacking, which is critical in implementing restoration and forest management activities. Our aim was to understand multiscale dynamics and spatial heterogeneity patterns of conifer forests and chaparral shrublands due to repeated mixed‐severity fire. Location: A mosaic of burned and unburned patches spanning the boundary of Lassen and Plumas National Forests, CA, USA. Methods: We used secondary geospatial landcover data classified by cover type before modern fires (1999) and after eight modern fires (2014). We calculated various landscape diversity and fragmentation metrics at patch and landscape scales using FRAGSTATS for comparison before and after fires. Results: At the fire severity patch scale, high‐severity fire reduced vegetation cover type heterogeneity by half, but reburning at low to moderate severity nearly doubled cover type heterogeneity. At the full landscape scale mixed‐severity fire, including all burn severities, increased vegetation cover type heterogeneity. Fragmentation indexes confirmed that fire created larger patches of shrub and fragmented patches of conifer forest. Conclusions: The effects of frequent large fire events on vegetation pattern and heterogeneity vary with the scale of analysis. Hence, heterogeneity and vegetation pattern change need to be evaluated at more than one scale to understand past and future ecological processes before prioritizing management actions for the conifer forests of the Sierra Nevada Mountain range. [ABSTRACT FROM AUTHOR]

The Cheadle Center at UCSB manages the North Campus Open Space (NCOS), which is a project that has restored 136 acres of upland and wetland habitats that existed before the area was converted into the Ocean Meadows Golf Course in the 1960s. The NCOS restoration project began in 2017 with a fine-scale grading of the site in order to recreate the salt marsh and use the excavated soil to rebuild the upland habitats to the southwest, which are now called the NCOS Mesa. In addition to re-establishing native biodiversity, a key goal of the restoration is to utilize the site as an educational, scientific, and recreational resource. This archived version of the October 2020 newsletter includes updates on Fall planting plans, a Burrowing Owl (Athene cunicularia) sighting and planned habitat enhancements, and Snowy Plover (Charadrius nivosus) habitat enhancements. The feature story focuses on Year 3 vegetation monitoring highlights.

The Cheadle Center at UCSB manages the North Campus Open Space (NCOS), which is a project that has restored 136 acres of upland and wetland habitats that existed before the area was converted into the Ocean Meadows Golf Course in the 1960s. The NCOS restoration project began in 2017 with a fine-scale grading of the site in order to recreate the salt marsh and use the excavated soil to rebuild the upland habitats to the southwest, which are now called the NCOS Mesa. In addition to re-establishing native biodiversity, a key goal of the restoration is to utilize the site as an educational, scientific, and recreational resource. This archived version of the December 2020 newsletter includes updates on the importance of not feeding wildlife, the presence of three burrowing owls (Athene cunicularia), Marsh Trail improvements, and planned removal of the Ellwood Marine Terminal tanks. The feature story focuses on bat acoustic monitoring, which has revealed a total of 8 species potentially using the space. Community photos include Hooded Merganser (Lophodytes cucullatus), Wilson’s Snipe (Gallinago delicata), Blue-gray Gnatcatcher (Poloptila caerulea), Barn Owl (Tyto alba), and White-tailed Kite (Elanus leucurus).

As climate change increases fire frequency in Mediterranean‐type shrublands, it is essential to understand the links between common postfire plant assemblages and soil nitrogen (N) and carbon (C) cycling during succession. In California chaparral, periodic fire removes shrub cover, deposits ammonium (NH4+‐N) on soils, and allows herbaceous assemblages to dominate for 3–5 years. Herbs influence soil biogeochemistry through several mechanisms, including nutrient uptake, litter decomposition, and rhizodeposition. Controlled experimental removal of select plant groups from wild assemblages can demonstrate interactions between plant groups and how plant traits influence belowground processes. In a two‐year herb‐removal experiment, we investigated the impact of N‐fixing and non‐N‐fixing herbs on soil N and C cycling. Treatments were (1) all herbs, (2) only non‐N‐fixing species, (3) only N‐fixing species, and (4) no herbs. In high‐N environments, N‐fixers were predicted to compete poorly against non‐N‐fixing neighbors. N‐fixers doubled in abundance when non‐N‐fixers were removed, but non‐N‐fixers were unaffected by N‐fixer removal. Two years after fire, no‐herbs plots had the lowest soil microbial respiration rates, and total accumulated C and N were lower than all‐herb plots. Two treatments, no‐herb and N‐fixer plots, had elevated mineral N concentrations, net N mineralization, and net nitrification in the second year of the experiment. Our findings underscore the importance of fire‐following herbs for postfire N retention and organic matter accumulation. A combination of both N‐fixing and non‐N‐fixing herbs maximized total soil C and N, although the accumulation of TC and TN in all‐herb plots was not significantly higher than in non‐N‐fixer plots. Results demonstrated the key role of non‐N‐fixing herbs in accumulating soil C and herbaceous communities for retaining N. Elevated soil nutrient availability two years postfire may contribute to the long‐term recovery of shrubs, even after herbs are no longer dominant. Future investigations should also consider the magnitude of soil microbial N retention in plots with different herb functional groups, along with the species‐specific contribution of non‐N‐fixing herbs to postfire C and N cycling. [ABSTRACT FROM AUTHOR]

Relatively mesic environments within arid regions may be important conservation targets as 'climate change refugia' for species persistence in the face of worsening drought conditions. Semi-arid southern California and the relatively mesic environments of California's Channel Islands provide a model system for examining drought responses of plants in potential climate change refugia. Most methods for detecting refugia are focused on 'exposure' of organisms to certain abiotic conditions, which fail to assess how local adaptation or acclimation of plant traits (i.e. 'sensitivity') contribute to or offset the benefits of reduced exposure. Here, we use a comparative plant hydraulics approach to characterize the vulnerability of plants to drought, providing a framework for identifying the locations and trait patterns that underlie functioning climate change refugia. Seasonal water relations, xylem hydraulic traits and remotely sensed vegetation indices of matched island and mainland field sites were used to compare the response of native plants from contrasting island and mainland sites to hotter droughts in the early 21st century. Island plants experienced more favorable water relations and resilience to recent drought. However, island plants displayed low plasticity/adaptation of hydraulic traits to local conditions, which indicates that relatively conserved traits of island plants underlie greater hydraulic safety and localized buffering from regional drought conditions. Our results provide an explanation for how California's Channel Islands function as a regional climate refugia during past and current climate change and demonstrate a physiology-based approach for detecting potential climate change refugia in other systems.

PREMISE:Flexible phenological responses of invasive plants under climate change may increase their ability to establish and persist. A key aspect of plant phenology is the timing of root production, how it coincides with canopy development and subsequent water-use. The timing of these events within species and across communities could influence the invasion process. We examined above- and belowground phenology of two species in southern California, the native shrub, Adenostoma fasciculatum, and the invasive perennial grass, Ehrharta calycina to investigate relative differences in phenology and water use. METHODS:We used normalized difference vegetation index (NDVI) to track whole-canopy activity across the landscape and sap flux sensors on individual chaparral shrubs to assess differences in aboveground phenology of both species. To determine differences in belowground activity, we used soil moisture sensors, minirhizotron imagery, and stable isotopes. RESULTS:The invasive grass depleted soil moisture earlier in the spring and produced longer roots at multiple depths earlier in the growing season than the native shrub. However, Adenostoma fasciculatum produced longer roots in the top 10 cm of soil profile in May. Aboveground activity of the two species peaked at the same time. CONCLUSIONS:The fact that Ehrharta calycina possessed longer roots earlier in the season suggests that invasive plants may gain a competitive edge over native plants through early activity, while also depleting soil moisture earlier in the season. Depletion of soil moisture earlier by E. calycina suggests that invasive grasses could accelerate the onset of the summer drought in chaparral systems, assuring their persistence following invasion.

The Cheadle Center at UCSB manages the North Campus Open Space (NCOS), which is a project that has restored 136 acres of upland and wetland habitats that existed before the area was converted into the Ocean Meadows Golf Course in the 1960s. The NCOS restoration project began in 2017 with a fine-scale grading of the site in order to recreate the salt marsh and use the excavated soil to rebuild the upland habitats to the southwest, which are now called the NCOS Mesa. In addition to re-establishing native biodiversity, a key goal of the restoration is to utilize the site as an educational, scientific, and recreational resource. This archived version of the September 2019 newsletter includes updates on weedwhacking to promote plant diversity and new mesa slope plantings. The feature story focuses on water quality monitoring results. Community photos include Red-Tailed Hawk (Buteo jamaicensis) and egrets.

Abstract As climate change increases fire frequency in Mediterranean‐type shrublands, it is essential to understand the links between common postfire plant assemblages and soil nitrogen (N) and carbon (C) cycling during succession. In California chaparral, periodic fire removes shrub cover, deposits ammonium (NH4+‐N) on soils, and allows herbaceous assemblages to dominate for 3–5 years. Herbs influence soil biogeochemistry through several mechanisms, including nutrient uptake, litter decomposition, and rhizodeposition. Controlled experimental removal of select plant groups from wild assemblages can demonstrate interactions between plant groups and how plant traits influence belowground processes. In a two‐year herb‐removal experiment, we investigated the impact of N‐fixing and non‐N‐fixing herbs on soil N and C cycling. Treatments were (1) all herbs, (2) only non‐N‐fixing species, (3) only N‐fixing species, and (4) no herbs. In high‐N environments, N‐fixers were predicted to compete poorly against non‐N‐fixing neighbors. N‐fixers doubled in abundance when non‐N‐fixers were removed, but non‐N‐fixers were unaffected by N‐fixer removal. Two years after fire, no‐herbs plots had the lowest soil microbial respiration rates, and total accumulated C and N were lower than all‐herb plots. Two treatments, no‐herb and N‐fixer plots, had elevated mineral N concentrations, net N mineralization, and net nitrification in the second year of the experiment. Our findings underscore the importance of fire‐following herbs for postfire N retention and organic matter accumulation. A combination of both N‐fixing and non‐N‐fixing herbs maximized total soil C and N, although the accumulation of TC and TN in all‐herb plots was not significantly higher than in non‐N‐fixer plots. Results demonstrated the key role of non‐N‐fixing herbs in accumulating soil C and herbaceous communities for retaining N. Elevated soil nutrient availability two years postfire may contribute to the long‐term recovery of shrubs, even after herbs are no longer dominant. Future investigations should also consider the magnitude of soil microbial N retention in plots with different herb functional groups, along with the species‐specific contribution of non‐N‐fixing herbs to postfire C and N cycling.

In this study, observations of live fuel moisture content (LFMC) for predominantly sampled fuels in six distinct regions of California were examined from 2000 to 2021. To gather the necessary data, an open-access database called the Fuel Moisture Repository (FMR), was developed. By harnessing the extensive data aggregation and query capabilities of the FMR, which draws upon the National Fuel Moisture Database, valuable insights into the live fuel moisture seasonality were obtained. Specifically, our analysis revealed a distinct downtrend in LFMC across all regions, with the exception of the two Northernmost regions. The uptrends of LFMC seen in those regions are insignificant to the general downtrend seen across all of the regions. Although the regions do not share the same trends over the temporal span of the study, from 2017 to 2021, all the regions experienced a downtrend two times more severe than the general 22-year downtrend. Further analysis of the fuel types in each of the six regions, revealed significant variability in LFMC across different fuel types and regions. To understand potential drivers of this variability, the relationship between LFMC and drought conditions was investigated. This analysis found that LFMC fluctuations were closely linked to water deficits. However, the drought conditions varied across the examined regions, contributing to extreme LFMC variability. Notably, during prolonged drought periods of 2 or more years, fuels adapted to their environment by stabilizing or even increasing their maximum and minimum moisture values, contrary to the expected continual decrease. These LFMC trends have been found to correlate to wildfire activity and the specific LFMC threshold of 79% has been proposed as trigger of an increased likelihood of large fires. By analyzing the LFMC and fire activity data in each region, we found that more optimal local thresholds can be defined, highlighting the spatial variability of the fire response to the LFMC. This work expands on existing literature regarding the connections between drought and LFMC, as well as fire activity and LFMC. The study presents a 22-year dataset of LFMC spanning the entirety of California and analyses the LFMC trends in California that haven’t been rigorously studied before.

The rise in wildfire frequency and severity across the globe has increased interest in secondary succession. However, despite the role of soil microbial communities in controlling biogeochemical cycling and their role in the regeneration of post‐fire vegetation, the lack of measurements immediately post‐fire and at high temporal resolution has limited understanding of microbial secondary succession. To fill this knowledge gap, we sampled soils at 17, 25, 34, 67, 95, 131, 187, 286, and 376 days after a southern California wildfire in fire‐adapted chaparral shrublands. We assessed bacterial and fungal biomass with qPCR of 16S and 18S and richness and composition with Illumina MiSeq sequencing of 16S and ITS2 amplicons. Fire severely reduced bacterial biomass by 47%, bacterial richness by 46%, fungal biomass by 86%, and fungal richness by 68%. The burned bacterial and fungal communities experienced rapid succession, with 5–6 compositional turnover periods. Analogous to plants, turnover was driven by "fire‐loving" pyrophilous microbes, many of which have been previously found in forests worldwide and changed markedly in abundance over time. Fungal secondary succession was initiated by the Basidiomycete yeast Geminibasidium, which traded off against the filamentous Ascomycetes Pyronema, Aspergillus, and Penicillium. For bacteria, the Proteobacteria Massilia dominated all year, but the Firmicute Bacillus and Proteobacteria Noviherbaspirillum increased in abundance over time. Our high‐resolution temporal sampling allowed us to capture post‐fire microbial secondary successional dynamics and suggest that putative tradeoffs in thermotolerance, colonization, and competition among dominant pyrophilous microbes control microbial succession with possible implications for ecosystem function. [ABSTRACT FROM AUTHOR]

Disturbance such as wildfire may create opportunities for plant communities to reorganize in response to climate change. The interaction between climate change and disturbance may be particularly important in forests, where many of the foundational plant species (trees) are long-lived and where poor initial tree establishment can result in conversion to shrub- or graminoid-dominated systems. The response of post-disturbance vegetation establishment to post-disturbance weather conditions, particularly to extreme weather, could therefore provide useful information about how forest communities will respond to climate change. We examined the effect of post-fire weather conditions on post-fire tree, shrub, and graminoid recruitment in fire-adapted forests in northern California, USA, by surveying regenerating vegetation in severely burned areas 4-5 yr after 14 different wildfires that burned between 2004 and 2012. This time period (2004-2016) encompassed a wide range of post-fire weather conditions, including a period of extreme drought. For the most common tree species, we observed little evidence of disturbance-mediated community reorganization or range shifts but instead either (1) low sensitivity of recruitment to post-fire weather or (2) weak but widespread decreases in recruitment under unusually dry post-fire conditions, depending on the species. The occurrence of a single strong drought year following fire was more important than a series of moderately dry years in explaining tree recruitment declines. Overall, however, post-fire tree recruitment patterns were explained more strongly by long-term climate and topography and local adult tree species abundance than by post-fire weather conditions. This observation suggests that surviving adult trees can contribute to a "biological inertia" that restricts the extent to which tree community composition will track changes in climate through post-disturbance recruitment. In contrast to our observations in trees, we observed substantial increases in shrub and graminoid establishment under post-fire drought, suggesting that shifts in dominance between functional groups may become more likely in a future with more frequent and intense drought.

Many plant species are likely to face population decline or even extinction in the coming century, especially those with a limited distribution and inadequate dispersal relative to the projected rates of climate change. The obligate seeding California endemic, Ceanothus perplexans is especially at risk, and depending on how climate change interacts with altered fire regimes in Southern California, certain populations are likely to be more at risk than others. To identify which areas within the species’ range might need conservation intervention, we modeled population dynamics of C. perplexans under various climate and fire regime change scenarios, focusing on spatially explicit patterns in fire frequency. We used a species distribution model to predict the initial range and potential future habitat, while adapting a density-dependent, stage-structured population model to simulate population dynamics. As a fire-adapted obligate seeder, simulated fire events caused C. perplexans seeds to germinate, but also killed all adults in the population. Our simulations showed that the total population would likely decline under any combination of climate change and fire scenario, with the species faring best at an intermediate fire return interval of around 30–50 years. Nevertheless, while the total population declines least with a 30–50 year fire return interval, the effect of individual subpopulations varies depending on spatially explicit patterns in fire simulations. Though climate change is a greater threat to most subpopulations, increased fire frequencies particularly threatened populations in the northwest of the species’ range closest to human development. Subpopulations in the mountainous southern end of the range are likely to face the sharpest declines regardless of fire. Through a combination of species distribution modeling, fire modeling, and spatially explicit demographic simulations, we can better prepare for targeted conservation management of vulnerable species affected by global change.

Isohydry (maintenance of plant water potential at the cost of carbon gain) and anisohydry (gas exchange maintenance at the cost of declining plant water status) make up two ends of a stomatal drought response strategy continuum. However, few studies have merged measures of stomatal regulation with xylem hydraulic safety strategies based on in situ field measurements. The goal of this study was to characterize the stomatal and xylem hydraulic safety strategies of woody species in the biodiverse Mediterranean-type ecosystem region of California. Measurements were conducted in situ when California was experiencing the most severe drought conditions in the past 1,200 years. We found coordination among stomatal, hydraulic, and standard leaf functional traits. For example, stem xylem vulnerability to cavitation (P50 ) was correlated with the water potential at stomatal closure (Pclose ); more resistant species had a more negative water potential at stomatal closure. The degree of isohydry-anisohydry, defined at Pclose -P50 , was correlated with the hydraulic safety margin across species; more isohydric species had a larger hydraulic safety margin. In addition, we report for the first time Pclose values below -10 MPa. Measuring these traits in a biodiverse region under exceptional drought conditions contributes to our understanding of plant drought responses.

Predator–prey interactions can be profoundly influenced by vegetation conditions, particularly when predator and prey prefer different habitats. Although such interactions have proven challenging to study for small and cryptic predators, recent methodological advances substantially improve opportunities for understanding how vegetation influences prey acquisition and strengthen conservation planning for this group. The California Spotted Owl (Strix occidentalis occidentalis) is well known as an old-forest species of conservation concern, but whose primary prey in many regions—woodrats (Neotoma spp.)—occurs in a broad range of vegetation conditions. Here, we used high-resolution GPS tracking coupled with nest video monitoring to test the hypothesis that prey capture rates vary as a function of vegetation structure and heterogeneity, with emergent, reproductive consequences for Spotted Owls in Southern California. Foraging owls were more successful capturing prey, including woodrats, in taller multilayered forests, in areas with higher heterogeneity in vegetation types, and near forest-chapparal edges. Consistent with these findings, Spotted Owls delivered prey items more frequently to nests in territories with greater heterogeneity in vegetation types and delivered prey biomass at a higher rate in territories with more forest-chaparral edge. Spotted Owls had higher reproductive success in territories with higher mean canopy cover, taller trees, and more shrubby vegetation. Collectively, our results provide additional and compelling evidence that a mosaic of large tree forest with complex canopy and shrubby vegetation increases access to prey with potential reproductive benefits to Spotted Owls in landscapes where woodrats are a primary prey item. We suggest that forest management activities that enhance forest structure and vegetation heterogeneity could help curb declining Spotted Owl populations while promoting resilient ecosystems in some regions. [ABSTRACT FROM AUTHOR]

The increased occurrences of drought and fire may be contributing to the loss of biodiverse ecosystems in Mediterranean regions. Specifically, the conversion of diverse native shrublands, such as chaparral, to non‐native annual grassland by fire is of great conservation concern in California. To avoid or slow the loss of chaparral, it is important to understand the underlying causes of landscape conversion. Studies investigating the interaction of multiple potential drivers are particularly crucial to identification of vulnerable areas of the landscape. Here we used aerial imagery to evaluate vegetation transitions between chaparral, sage scrub, grassland, and tree domination and their potential drivers within Ventura County, CA, a strongly Mediterranean climate region. We used random forest algorithms and conditional inference trees to determine the climatic, topographic, and fire‐related variables contributing most to vegetation change. Our results support that chaparral conversion to grass (27% of chaparral plots) is a result of landscape position, fire, and drought acting in tandem. In particular, lower elevation, southwest‐facing slopes that experience a postfire drought are at very high likelihood of conversion to non‐native annual grass. Additionally, our results show that these grasslands, once formed, rarely convert to other community types. Therefore, protecting shrub‐dominated areas that are most likely to convert (low elevation, more southwest‐facing slopes, and less annual precipitation) is crucial to preserving native vegetation diversity. [ABSTRACT FROM AUTHOR]

Abstract The increased occurrences of drought and fire may be contributing to the loss of biodiverse ecosystems in Mediterranean regions. Specifically, the conversion of diverse native shrublands, such as chaparral, to non‐native annual grassland by fire is of great conservation concern in California. To avoid or slow the loss of chaparral, it is important to understand the underlying causes of landscape conversion. Studies investigating the interaction of multiple potential drivers are particularly crucial to identification of vulnerable areas of the landscape. Here we used aerial imagery to evaluate vegetation transitions between chaparral, sage scrub, grassland, and tree domination and their potential drivers within Ventura County, CA, a strongly Mediterranean climate region. We used random forest algorithms and conditional inference trees to determine the climatic, topographic, and fire‐related variables contributing most to vegetation change. Our results support that chaparral conversion to grass (27% of chaparral plots) is a result of landscape position, fire, and drought acting in tandem. In particular, lower elevation, southwest‐facing slopes that experience a postfire drought are at very high likelihood of conversion to non‐native annual grass. Additionally, our results show that these grasslands, once formed, rarely convert to other community types. Therefore, protecting shrub‐dominated areas that are most likely to convert (low elevation, more southwest‐facing slopes, and less annual precipitation) is crucial to preserving native vegetation diversity.

Dieback and mortality in wildland plant species due to climate change have been on the rise in recent decades, and latent fungal pathogens might play a significant role in these events. During a severe multiyear drought, canopy dieback associated with latent pathogens in the Botryosphaeriaceae (Bot) family was observed in stands of a dominant shrub species, big berry manzanita (Arctostaphylos glauca), across chaparral landscapes in California. These fungi are significant pathogens of woody agricultural species, especially in hosts experiencing stress, and have become a threat to economically important crops worldwide. However, little is known regarding their occurrence, distribution, and impact in wildland systems. We conducted a field survey of 300 A. glauca shrubs across an elevational gradient to identify Bot species infection as it relates to (i) A glauca dieback severity and (ii) landscape variables associated with plant drought stress. Our results show that Bots are widely infecting A. glauca across the land scape, and there is a significant correlation between elevation and dieback severity. Dieback severity was significantly higher at lower elevations, suggesting that infected shrubs at lower elevations are at greater risk than those at higher elevations. Furthermore, two Bot species, Neofusicoccum australe and Botryosphaeria dothidea, were most frequently isolated, with N. australe being the most common and, based on haplotype analysis, likely the most recently introduced of the two. Our results confirm the wide distribution of latent Bot fungi in a wild shrubland system and provide valuable insight into areas of greatest risk for future shrub dieback and mortality. These findings could be particularly useful for informing future wildlands management strategies with regard to introduced latent pathogens. [ABSTRACT FROM AUTHOR]

One consequence of global change causing widespread concern is the possibility of ecosystem conversions from one type to another. A classic example of this is vegetation type conversion (VTC) from native woody shrublands to invasive annual grasslands in the biodiversity hotspot of Southern California. Although the significance of this problem is well recognized, understanding where, how much, and why this change is occurring remains elusive owing to differences in results from studies conducted using different methods, spatial extents, and scales. Disagreement has arisen particularly over the relative importance of short‐interval fires in driving these changes. Chronosequence approaches that use space for time to estimate changes have produced different results than studies of changes at a site over time. Here we calculated the percentage woody and herbaceous cover across Southern California using air photos from ~1950 to 2019. We assessed the extent of woody cover change and the relative importance of fire history, topography, soil moisture, and distance to human infrastructure in explaining change across a hierarchy of spatial extents and regions. We found substantial net decline in woody cover and expansion of herbaceous vegetation across all regions, but the most dramatic changes occurred in the northern interior and southern coastal areas. Variables related to frequent, short‐interval fire were consistently top ranked as the explanation for shrub to grassland type conversion, but low soil moisture and topographic complexity were also strong correlates. Despite the consistent importance of fire, there was substantial geographical variation in the relative importance of drivers, and these differences resulted in different mapped predictions of VTC. This geographical variation is important to recognize for management decision‐making and, in addition to differences in methodological design, may also partly explain differences in previous study results. The overwhelming importance of short‐interval fire has management implications. It suggests that actions should be directed away from imposing fires to preventing fires. Prevention can be controlled through management actions that limit ignitions, fire spread, and the damage sustained in areas that do burn. This study also demonstrates significant potential for changing fire regimes to drive large‐scale, abrupt ecological change. [ABSTRACT FROM AUTHOR]

The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low velocity fire wind tunnel where two distinct layers of fuel were constructed to represent surface and crown fuels in chaparral. Chamise, a common chaparral shrub, comprised the live crown layer. The dead fuel surface layer was constructed with excelsior (shredded wood). We developed a methodology to measure mass loss, temperature, and flame height for both fuel layers. Thermocouples placed in each layer estimated temperature. A video camera captured the visible flame. Post-processing of digital imagery yielded flame characteristics including height and flame tilt. A custom crown mass loss instrument developed in-house measured the evolution of the mass of the crown layer during the burn. Mass loss and temperature trends obtained using the technique matched theory and other empirical studies. In this study, we present detailed experimental procedures and information about the instrumentation used. The representative results for the fuel mass loss rate and temperature filed within the fuel bed are also included and discussed.

Fuel hazard reduction treatments such as prescribed fire and mastication are widely used to reduce fuel hazard. These treatments help protect people from wildfire, yet may not be mutually beneficial for people and ecosystems in areas adapted to infrequent crown fire. Short-term studies indicate that some fuel hazard reduction treatments can be detrimental to biodiversity and ecosystem function, suggesting that land managers face an acute dilemma between protecting people or ecosystems. However, the long-term ecological trajectories and fuel hazard outcomes of fuel treatments are poorly understood. Using a 13-year replicated experimental study, we evaluated how shrub cover, non-native species abundance, native species diversity, and an obligate seeder responded to fuel treatments in California’s northern chaparral. The fuel hazard reduction treatments (fire and mastication) and their seasons of implementation (fall, winter, and spring) had unique influences on plant communities. Untreated controls had continuous shrub canopy with no understory throughout the study. Recovery of shrubs after mastication was slower than recovery after fire. Ten years after treatment, shrub cover in fire treatments and spring mastications produced 1% to 2% less cover than the control, whereas fall mastications produced 8l% less cover than the control. The number of non-native plants, including non-native annual grasses, was higher after mastication treatments compared to fire treatments after 10 years. Surprisingly, mastication treatments also increased cover of an uncommon native shrub that is an obligate seeder. The season of treatment also influenced these outcomes, but to a lesser extent than treatment type. Long-term shrub species composition did not follow the trends of short-term species composition of shrub recruitment. Based on these findings, we concluded that fuel hazard reduction treatments only reduce shrub cover for approximately 10 years, and can change plant community composition, suggesting that thorough consideration of the decision to use fuel hazard reduction treatments is warranted.

Wildland conservation efforts require accurate maps of plant species distribution across large spatial scales. High-resolution species mapping is difficult in diverse, dense plant communities, where extensive ground-based surveys are labor-intensive and risk damaging sensitive flora. High-resolution satellite imagery is available at scales needed for plant community conservation across large areas, but can be cost prohibitive and lack resolution to identify species. Deep learning analysis of drone-based imagery can aid in accurate classification of plant species in these communities across large regions. This study assessed whether drone-based imagery and deep learning modeling approaches could be used to map species in complex chaparral, coastal sage scrub, and oak woodland communities. We tested the effectiveness of random forest, support vector machine, and convolutional neural network (CNN) coupled with object-based image analysis (OBIA) for mapping in diverse shrublands. Our CNN + OBIA approach outperformed random forest and support vector machine methods to accurately identify tree and shrub species, vegetation gaps, and communities, even distinguishing two congeneric shrub species with similar morphological characteristics. Similar accuracies were attained when applied to neighboring sites. This work is key to the accurate species identification and large scale mapping needed for conservation research and monitoring in chaparral and other wildland plant communities. Uncertainty in model application is associated with less common species and intermixed canopies.

Background: The oxidized low density lipoprotein (ox-LDL) contributes to inflammation and oxidative stress through the activation of macrophages under hyperglycemia contributing to the development of diabetes mellitus and to atherosclerosis. Plants are a source of effective and innocuous antioxidants. Larrea divaricata Cav. (Zygophyllaceae) is used in Argentina folk medicine for its anti-inflammatory properties. Methods: The aim of this work was to study the antioxidant and anti-inflammatory effects of the aqueous extract (AE) of L. divaricata on macrophages under glucose stimulation and on human LDL and HDL particles under free radical generators. Results: AE reduced the lipid peroxidation (17%), nitric oxide (NO) (47-50%), tumor necrosis factor-α (TNF-α) (32%) and free radicals (50%) induced by glucose on macrophages. Also prevented HDL nitration (28%), thus preserving its function and structure and inhibited LDL oxidation. The effect on the nitrosative stress was mainly driven by nordihydroguaiaretic acid (NDGA). Conclusions: These results suggest a potential usefulness of AE as an adjuvant phytotherapy in patients with diabetes mellitus and atherosclerosis. [ABSTRACT FROM AUTHOR]

Abstract Nordihydroguaiaretic acid (NDGA) is a natural product obtained by the alkaline extraction of dried plants of Larrea tridentata species. Due to the biological properties presented, such as antioxidant, anti-inflammatory, antiviral and cytotoxic capacity, this compound is being increasingly studied. In this review, it was evaluated the benefits of NDGA against different animal models. Besides that, it was found that this compound has antitumor activity similar to its synthetic derivative terameprocol in prostate tumors. The hypoglycemic effect may be evidenced by the inhibition of sugar uptake by NDGA; in obesity, studies have observed that NDGA presented a positive regulatory effect for Peroxisome proliferator-activated receptors (PPAR-α) involved in the oxidation of hepatic fatty acids and reduced the expression of lipogenic genes. Regarding its antioxidant potential, its mechanism is related to the ability to in vitro scavenging reactive substances. Although there are several studies demonstrating the benefits of using NDGA, there are also reports of its toxicity, mainly of liver damage and nephrotoxicity.

Long-term studies at Hopland Research and Extension Center find no simple answers for reducing fire risk while conserving biodiversity.

Premise: Does the seed size–seed number allocation trade‐off model apply to long‐term persistent soil seed banks? This trade‐off between seed size versus number of seeds produced is usually applied at a single population on an annual basis. Our question is how this model might apply to close relatives that produce dormant seed forming long‐term persistent soil seed banks. These two criteria allow a focus on divergent evolution of conspecifics and permits us to isolate seed size in the spectrum of life history traits that may be influencing seed traits, and on how seed size influences accumulation and persistence in the soil. Methods: In California, Arctostaphylos species only produce physiologically dormant seed that are fire‐stimulated and that vary in seed size permitting seed size–seed bank density relationship as a test of the seed size–seed number allocation model. Soil seed banks of 10 species of Arctostaphylos were sampled with fruit volumes ranging from 21–1063 mm3. Seed bank density was determined by hand extraction from soil samples. Results: We found that seed bank densities were significantly negatively related to fruit or seed size. Conclusions: Rather than an issue of allocational trade‐off between size and number, we interpret these results as reflecting seed predation and postfire seedling establishment. Seed bank densities, even after decades, generally were less than one or two‐year's seed production, suggesting intense seed predation. Burial by scatter‐hoarding rodents provided sufficient seeds deep enough for survival of fire. Variation on seed size suggests seedling establishment constraints, but it needs further research. [ABSTRACT FROM AUTHOR]

Aim: Fire regimes are shifting globally due to climate change, land management practices and population growth, putting species at risk if they are unable to adapt to more frequent or severe wildfires. While many fire‐adapted species may be able to accommodate some amount of change in fire regimes, fire‐sensitive or late‐successional species that colonize fire‐prone ecosystems between wildfires may be especially vulnerable to more frequent or severe fires. Here, we seek to understand the rate of lichen recolonization after high‐severity fires in an ecosystem that is experiencing increasing fire frequency. Location: The Inner North Coast Range of California, USA. Methods: Using a chronosequence of wildfires in a Northern California chaparral shrubland, we compare lichen communities among sites that burned 3, 13, 22, 30 and 65 years previously, as well as old‐growth chaparral sites without a recorded fire over the past century. Results: We find that lichen richness increases consistently with time since fire but begins to level off 20–30 years following fire, roughly corresponding to the closure of the shrub canopy. Some taxa and guilds were found only in old‐growth chaparral. Conclusions: Our findings highlight that fire‐intolerant organisms may be relatively slow to recolonize landscapes after high‐severity fire and that the majority of chaparral lichen taxa may be lost where fire intervals shorten to <20 years, which has already occurred in some parts of California. [ABSTRACT FROM AUTHOR]

We examined the effects of hand clearing and pile burning of chaparral on plants and wildlife on the perimeter of Pine Hill 1–2 years after clearing. Pine Hill is home to four federally listed plant species, necessitating botanical surveys prior to clearing activities to prevent harming these species. We found over 65 new locations for the listed plants. We compared vegetation within burn scars, in cleared only plots, and in intact chaparral (control) and the germination and survival of a listed species, Ceanothus roderickii (Pine Hill Ceanothus). The density of C. roderickii seedlings was far lower in the cleared, unburned treatment than in the burned treatments, while mature C. roderickii was only present in unburned treatments and mature chaparral. Intact chaparral had higher cover but lower species richness of both native and exotic species than all disturbed treatments. The cleared only treatment had almost three times the cover by exotic grasses as did the burned treatments, and cover by presumably palatable, native and exotic species, was almost twice that of the burned treatments; mature chaparral contained few palatable plants, i.e. those identified as having wildlife value by Conrad (1987). Increased availability of palatable plants in treated areas may have contributed to 3–4 times higher probabilities of detection by cameras of herbivores in treated versus intact chaparral; which may have attracted smaller predators (bobcats [Lynx rufus] and gray foxes [Urocyon cinereoargenteus]) that were positively associated with western grey squirrel (Sciurus griseus) detections. Large carnivore detections were higher in areas with higher mule deer (Odocoileus hemionus) detections. Larger animals (pumas [Puma concolor], black bears [Ursus americanus], and mule deer) were detected 2–4 times more in treated areas, likely due to the physical impediment of mature chaparral. Invasion of nonnative grasses and increased wildlife usage may have been accelerated through the creation of firebreaks; continued monitoring will investigate long-term effects.

Conservation typically has dual objectives of preserving both biodiversity and ecosystem functioning; however, management of ecosystems is challenging. To address the conservation of ecosystem functions, we 1) described the insect community associated with the decomposition of small mammal carcasses, 2) assessed correlations between insects (abundance and community composition) and landscape cover types, and 3) quantified decomposition rates of a small mammal carcass in Mediterranean shrublands and grasslands of San Diego County, CA USA. Beetle families (Silphidae, Staphylinidae, Histeridae) and a fly family (Phoridae) exhibited a negative relationship with urban land cover and a positive relationship with sage scrub within 5 km of trapping locations. Decomposition rates of a small mammal carcass also exhibited a negative correlation with the proportion of urban landscape and positive correlation with sage scrub cover. While it is expected that differing land cover composition will result in different insect communities, we demonstrated how these different communities are directly tied to ecosystem function. Insects should be a greater focus of conservation efforts due to their high level of biodiversity, integral role in many ecosystem functions, and the recent documentation of global insect declines. Studies like ours provide a way for conservation efforts to shift focus from managing individual species to preserving ecosystem functions so that management can meet their stated goals.

Woody, evergreen shrublands are the archetypal community in mediterranean‐type ecosystems, and these communities are profoundly changed when they undergo vegetation‐type conversion (VTC) to become annual, herb‐dominated communities. Recently, VTC has occurred throughout southern California chaparral shrublands, likely with changes in important ecosystem functions. The mechanisms that lead to VTC and subsequent changes to ecosystem processes are important to understand as they have regional and global implications for ecosystem services, climate change, land management, and policy. The main drivers of VTC are altered fire regimes, aridity, and anthropogenic disturbance. Some changes to ecosystem function are certain to occur with VTC, but their magnitudes are unclear, whereas other changes are unpredictable. I present two hypotheses: (1) VTC leads to warming that creates a positive feedback promoting additional VTC, and (2) altered nitrogen dynamics create negative feedbacks and promote an alternative stable state in which communities are dominated by herbs. The patterns described for California are mostly relevant to the other mediterranean‐type shrublands of the globe, which are biodiversity hotspots and threatened by VTC. This review examines the extent and causes of VTC, ecosystem effects, and future research priorities. [ABSTRACT FROM AUTHOR]