Live Oak Research Articles

Nitrogen Fertilization in Snap Bean Following a Legume in the Sandy Soils of North Florida

Despite being a legume, snap bean (Phaseolus vulgaris L.) lacks nodulation genes, restricting its ability for nitrogen (N) fixation through rhizobia, making N fertilization essential for maximizing yields. However, conventional fertilizer application may lead to N losses due to a lack of synchronization between plant uptake and N availability. A promising option could be controlled-release fertilizers (CRFs), which can be custom-formulated to synchronize nutrient release with plant growth needs, promoting efficient resource use. Field studies were conducted at the North Florida Research and Education Center-Suwannee Valley (NFREC-SV) in Live Oak, FL, during the spring of 2021 and 2022. The experiments also investigated broadcasting and banding application methods of the University of Florida’s recommended N rate (112 kg·ha−1). The experimental design comprised 10 treatments, including five N rates (0, 56, 112, 168, and 224 kg·ha−1 N) and two fertilizer sources (ammonium nitrate and CRF), applied to ‘Caprice’ in a randomized complete block design with four replications. Results showed a significant yield improvement with N fertilization vs. the zero-N control. However, no yield increase was observed beyond 56 kg·ha−1. This finding could be due to the residual N from a preceding peanut crop rotation in both years. No notable variation in quality metrics (pod length and width) occurred above the 56 kg·ha−1 threshold. The results also revealed that the choice between conventional or CRF did not exert any statistically significant differences in snap bean yield. In addition, fertilizer broadcast and banding treatments yielded the same results.

Description of a new species of Chrysonotomyia Ashmead from Houston, Texas, USA (Hymenoptera, Chalcidoidea, Eulophidae).

A new species of the genus Chrysonotomyia Ashmead, Chrysonotomyiasusbelli sp. nov., is described from the Rice University campus in Houston, Texas, USA. The species is a parasitoid emerging from Neuroterusnr.bussae galls in leaves of the southern live oak (Quercusvirginiana). This represents the 6th species described from North America north of Mexico and the first in the world known to parasitize cynipid gall wasps. This discovery hints at an entire undiscovered niche between Chrysonotomyia parasitoids, cynipid gall wasps, and oaks in the Nearctic, which is a global biodiversity hotspot for oaks and cynipids. This new species description is complemented by mtDNA-COI-barcode data and information on the natural history of this species. We record host association, phenology, and report a leaf-scanning behavior performed by females, presumably to search for host galls. Modifications to the key of New World members of the genus (Hansson 2004) are included to integrate this new species.

Response of Live Oak Regeneration to Planting Density, Fertilizer, and Mulch

Response of Live Oak Regeneration to Planting Density, Fertilizer, and Mulch

Defining the Pathobiomes Associated with Drippy Blight in Colorado and Drippy Nut in California

Drippy blight, an emergent bacterial disease of oaks, was described recently from urban oaks in the Front Range of Colorado, USA. This disease, which causes branch dieback and oozing of bacterial exudates from cankers, is caused by Lonsdalea quercina and primarily affects red oaks, with Northern red oak (Quercus rubra) the most susceptible. Drippy nut is a similar, less acute condition that exists in California, USA and affects acorns of interior live oak (Quercus wislizenii) and coastal live oak (Quercus agrifolia). The objective of this study was to compare the microbial communities of drippy blight in Colorado to those of drippy nut in California, and determine if other pathogenic fungal or bacterial taxa are associated with the diseases. Symptomatic and asymptomatic tissues were sampled in California and Colorado, and metagenomic analyses were performed to describe the fungal and bacterial communities. We found a suite of bacterial species, dominated by taxa within the genus Zymobacter, that were associated with symptomatic tissues for both drippy nut and drippy blight. L. quercina is the main pathogenic associate of both diseases. We found fungal yeasts associated with symptomatic tissues, and although not pathogens, these taxa were present in the pathobiome of drippy nut and drippy blight in California and Colorado. We did, however, identify taxa belonging to Gnomoniopsis, a known pathogen, associated with California symptomatic samples. Our study found an overlapping suite of bacterial associates of drippy blight and drippy nut, though more variation occurred within the fungal genera associated with these oak diseases.

The response of a sorghum sudangrass cover crop to residual nitrogen and its relationship with spectral sensors

AbstractA sorghum sudangrass (SSG) cover crop grown after a cash crop could take up residual nitrogen (N) before it is lost. As in‐field monitoring of SSG properties is laborious, predicting biomass and N concentrations with spectral sensors could be useful. At two sites in Live Oak, Florida, we evaluated the response of SSG to residual N from previous N fertilization and the performance of handheld and satellite sensors in estimating SSG properties. We quantified aboveground biomass, plant N, leaf greenness (NDVI), net potential N mineralization (PNM), and soil permanganate oxidizable carbon (POXC). Residual N did not affect SSG properties, PNM was highest at the highest N input rate in one site, and soil POXC was correlated with SSG properties (biomass and plant N). NDVI measured from a handheld sensor better predicted SSG properties than satellite imagery in these small plots, suggesting a greater potential to be a useful management tool.

Species-specific responses drive browsing impacts on physiological and functional traits in Quercus agrifolia and Umbellularia californica.

Herbivory is a fundamental ecological force in the evolution of plant physiological, morphological, and chemical attributes. In this study, we explored how browsing pressure by local deer populations affected leaf form and function in two California native tree species, Quercus agrifolia (coast live oak) and Umbellularia californica (California bay laurel). Specifically, we investigated how leaf and stem vascular attributes differed between browsed and non-browsed zones of each species. Browsing significantly altered traits such as leaf to phloem ratios and leaf area, but we observed few meaningful differences in leaf and stem anatomy between browsed and non-browsed material. We discuss these results in the context of leaf and stem adaptations to herbivory and water use efficiency and explore future research considerations for investigating leaf and stem vascular trait development with herbivore presence.

Drought heightens severity of diseases caused by Botryosphaeria dothidea and Cryptostroma corticale and needs to be factored in to properly assess pathogenicity or fulfill Koch’s postulates

AbstractClimate change is driving the emergence of novel tree diseases at the global scale, requiring new approaches for the formal confirmation of the pathogenicity of novel pathogens on novel hosts. At the same time, predictive models need to account for the possible effect of environmental changes and of abiotic stressors on disease severity for all diseases. By wound-inoculating Botryosphaeria dothidea on potted California coast live oaks and Cryptostroma corticale on potted silver maples, simultaneously in well-watered and in water-deprived conditions, I show that drought conditions increase the severity of disease symptoms. I also show that, by including a water-stressed treatment, I can formally prove pathogenicity and fulfill Koch’s postulates for putative pathogens that could not be confirmed in the absence of the stressor. Additionally, I show that the inclusion of data obtained in water stress conditions increases the differentiation between symptoms caused by fungal infection vs. symptoms caused by wound trauma, thus reducing the possible effect of outliers, a significant problem affecting many trials for fulfilling Koch’s postulates conducted with a limited number of replicates. The availability of comparable datasets in the presence and the absence of an abiotic stressor allows for the calculation of an Environmental Disease Component Index. Positive values of the index indicate a significant role of environmental change in disease progression and identify those pathogens that must be modeled factoring in climatic stressors. I suggest that this index may be extremely valuable for identifying pathogens likely to become emergent as climate changes.

Рост и состояние дуба черешчатого в смешанных древостоях полезащитных лесных полос

An analysis of the creation and operation of protective forest plantations at agricultural enterprises of the Central Chernozem Region allows us to assert that positive ameliorative functions are performed by those forest plantations that have good growth, high stability and longevity. Russian forestry scientists have recognized that the main species in the steppe conditions for all types of protective forest plantations is the English oak. The aim of the research has been to assess the current state of the stands in forest shelterbelts planted via different methods with the English oak as the main species. Taxation works and forest pathology research were carried out in 1997–2021 in the forest shelterbelt no. 9, established in the spring of 1989 by 2-year-old seedlings in the land-use territory of the Federal State Unitary Enterprise Experimental Production Farm “Znamya Oktyabrya” of the Talovskiy District of the Voronezh Region. It has been established that the influence of combinations of tree species in forest belts on the growth of the English oak at the age of 32 years is quite significant. As a result of competitive relations for environmental resources by fast-growing and associate species, the number of live oak trees in a continuous row planting option is 35.6...52.1 % less than in intermittent forest belt options, of their number during planting. The remaining sharply oppressed oak trees in the plantation sown in the continuous row planting way are far behind in height and stem diameter (by 0.8...7.6 m and 4.1...12.7 cm, respectively) compared to the oaks growing in the intermittent forest belts sown in a block planting way. The absence of improvement felling in the experimental plantations during their growth and formation has led to a significant number of dead oak wood and non-viable trees of this species. Moreover, the proportion of dead oak wood and non-viable trees in the forest belt sown via continuous row planting exceeds the indicator in the intermittent forest belts by 36.6...40.6 %. The number of viable oak trees in the intermittent belt options is 17.7...27.3 % higher than in the continuous row planting option, and the number of limitedly viable trees is 11.5...18.9 % higher.

Urban Forest Resilience: Assessment and Management Strategies for Stressed Trees in Diverse Environments

Variety of trees are found in both urban and wild areas; these trees are indispensable in maintaining ecosystem health and promoting human well-being. However, stressors affect the health of these trees; this makes them face management approaches. In this study, an assessment and management of five (5) different tree species at Southern University and A&M College in Baton Rouge-USA were carried out. The Southern Magnolia, Southern Red Oak, and Live Oak showed symptoms of stress, such as leaning and decay. The identified Loblolly Pine showed symptoms such as bark beetle infestations and resource competition. For each of these species, specific indicators of stress were identified and recommended management approaches. These include the installation of support systems, pruning of diseased branches, soil tillage, and pest control techniques. These practices allow the strengthening of urban forest, which ensures continued health and functioning of our ecosystems.

A test of trade-offs in dispersal and reproduction within and between a sister species pair of specialist insect herbivores.

Understanding the drivers of trade-offs among traits is vital for comprehending the evolution and maintenance of trait variation. Theoretical frameworks propose that evolutionary mechanisms governing trade-offs frequently exhibit a scale-dependent nature. However, empirical tests of whether trade-offs exhibited across various biological scales (i.e. individuals, populations, species, genera, etc.) remains scarce. In this study, we explore trade-off between dispersal and reproductive effort among sympatric sister species of wasps in the genus Belonocnema (Hymenoptera: Cynipini: Cynipidae) that form galls on live oaks: B. fossoria, which specializes on Quercus geminata, and B. treatae, which specializes on Q. virginiana. Specifically, our results suggest that B. fossoria has evolved reduced flight capability and smaller wings, but a larger abdomen and greater total reproductive effort than B. treatae, which has larger wings and is a stronger flier, but has a smaller abdomen and reduced total reproductive effort. These traits and the relationships among them remain unchanged when B. fossoria and B. treatae are transplanted and reared onto the alternative host plant, suggesting that trait divergence is genetically based as opposed to being a plastic response to the different rearing environments. However, when looking within species, we found no evidence of intraspecific trade-offs between wing length and reproductive traits within either B. fossoria or B. treatae. Overall, our results indicate that observed trade-offs in life history traits between the two gall former species are likely a result of independent adaptations in response to different environments as opposed to the amplified expression of within species intrinsic tradeoffs.

Soil carbon, nitrogen, and phosphorus storage in juniper–oak savanna: role of vegetation and geology

Abstract. Woody-plant encroachment into grasslands and savannas has been globally widespread during the past century, likely driven by interactions between grazing, fire suppression, rising atmospheric CO2, and climate change. In the southernmost US Great Plains, Ashe juniper and live oak have increased in abundance. To evaluate potential interactions between this vegetation change and the underlying soil parent material on ecosystem biogeochemistry, we quantified soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and δ13C of SOC in soils obtained from trenches passing through grassland, juniper, and oak patches on soils lying atop the respective Edwards and Buda limestone formations in central Texas. Soils on the Edwards formation are more shallow and have more rock outcropping than those on Buda. The δ13C values of SOC under grasslands was −19 ‰, whereas those under woody patches were −21 ‰ to −24 ‰, indicating that wooded areas were relatively recent components of the landscape. Compared with grasslands, areas now dominated by juniper or oak had elevated SOC, TN, and TP storage in soils lying atop Edwards limestone. In Buda soils, only oak patches had increased SOC, TN, and TP storage compared with grasslands. Woody encroachment effects on soil nutrients were higher in soils on the Edwards formation, perhaps because root and litter inputs were more concentrated in the relatively shallow layer of soil atop the Edwards bedrock. Our findings suggest that geological factors should be considered when predicting nutrient store responses in savannas following vegetation change. Given that woody encroachment is occurring globally, our results have important implications for the management and conservation of these ecosystems. The potential interactive effects between vegetation change and soil parent material on C, N, and P storage warrant attention in future studies aimed at understanding and modeling the global consequences of woody encroachment.

Restricted internal diffusion weakens transpiration-photosynthesis coupling during heatwaves: Evidence from leaf carbonyl sulphide exchange.

Increasingly frequent and intense heatwaves threaten ecosystem health in a warming climate. However, plant responses to heatwaves are poorly understood. A key uncertainty concerns the intensification of transpiration when heatwaves suppress photosynthesis, known as transpiration-photosynthesis decoupling. Field observations of such decoupling are scarce, and the underlying physiological mechanisms remain elusive. Here, we use carbonyl sulphide (COS) as a leaf gas exchange tracer to examine potential mechanisms leading to transpiration-photosynthesis decoupling on a coast live oak in a southern California woodland in spring 2013. We found that heatwaves suppressed both photosynthesis and leaf COS uptake but increased transpiration or sustained it at non-heatwave levels throughout the day. Despite statistically significant decoupling between transpiration and photosynthesis, stomatal sensitivity to environmental factors did not change during heatwaves. Instead, midday photosynthesis during heatwaves was restricted by internal diffusion, as indicated by the lower internal conductance to COS. Thus, increased evaporative demand and nonstomatal limitation to photosynthesis act jointly to decouple transpiration from photosynthesis without altering stomatal sensitivity. Decoupling offered limited potential cooling benefits, questioning its effectiveness for leaf thermoregulation in xeric ecosystems. We suggest that adding COS to leaf and ecosystem flux measurements helps elucidate diverse physiological mechanisms underlying transpiration-photosynthesis decoupling.

Georgia Library Spotlight: Live Oak Public Libraries’ Social Services Program Connects Communities with Resources

Georgia Library Spotlight: Live Oak Public Libraries’ Social Services Program Connects Communities with Resources

The role of divergent host use and geography in the evolution of habitat isolation and sexual isolation among sister species of Belonocnema gall wasps.

Ecology and geography can play important roles in the evolution of reproductive isolation across the speciation continuum, but few studies address both at the later stages of speciation. This notable gap in knowledge arises from the fact that traditional ecological speciation studies have predominantly focused on the role of ecology in initiating the speciation process, while many studies exploring the effect of geography (e.g., reinforcement) concentrate on species pairs that lack divergent ecological characteristics. We simultaneously examine the strength of habitat isolation and sexual isolation among three closely related species of Belonocnema gall-forming wasps on two species of live oaks, Quercus virginiana and Q. geminata, that experience divergent selection from their host plants and variable rates of migration due to their geographic context. We find that the strength of both habitat isolation and sexual isolation is lowest among allopatric species pairs with the same host plant association, followed by allopatric species with different host plant associations, and highest between sympatric species with different host-plant associations. This pattern suggests that divergent selection due to different host use interacts with geography in the evolution of habitat isolation and sexual isolation during the later stages of speciation of Belonocnema wasps.

Hyperspectral (VNIR-SWIR) analysis of roll front uranium host rocks and industrial minerals from Karnes and Live Oak Counties, Texas Coastal Plain

VNIR-SWIR (400–2500 nm) reflectance measurements were made on the surfaces of various cores, cuttings and sample splits of sedimentary rocks from the Tertiary Jackson Group, and Catahoula, Oakville and Goliad Formations. These rocks vary in composition and texture from mudstone and claystone to sandstone and are known host rocks for roll front uranium occurrences in Karnes and Live Oak Counties, Texas. Spectral reflectance profiles, 569 in total, were reduced to 125 representative spectral signatures, which were analyzed using the U.S. Geological Survey's (USGS) Material Identification and Characterization Algorithm (MICA). MICA uses an automated continuum-removal procedure together with a least-squares linear regression to determine the fit of observed sample spectral absorption features to those of reference mineral standards in a spectral library. The reference minerals include various clay, mica, carbonate, ferric and ferrous iron minerals and their mixtures. In addition, absorption feature band-depth analysis was done to identify rock surfaces exhibiting absorption features related to uranium and zeolite minerals, which were not included in the command files used to execute MICA.Rocks from each of the four geologic units produced broadly similar spectral signatures as a result of comparable mineral compositions, but there were some notable differences. For example, Ca- and Na-montmorillonite was matched most frequently to the spectral absorption features in 2-μm (∼2000–2500 nm) wavelengths, while goethite occurred often at 1-μm (∼400–1000 nm) wavelengths. The latter is related to limonitic iron-staining in and around oxidized zones of the uranium roll front as described in previous papers. Rocks of the Jackson Group differed from those of the Catahoula, Oakville and Goliad units in that the former exhibited spectral features we interpret as being due to the presence of lignite-bearing mudstone layers. Goliad rocks exhibit spectral features related to dolomite, gypsum, anhydrite, and an unidentified green clay mineral that is possibly glauconite. Jackson Group rocks also exhibit weak but well-resolved absorption features at 964 and 1157 nm related to either or both zeolite minerals clinoptilolite and heulandite. These zeolite minerals and a few spectra exhibiting hydrous silica absorption features are indicative of alteration of volcanic glass in tuffaceous mudstone and claystone layers. A few sample spectra exhibited strong absorption features at around 1135 nm related to the uranium mineral coffinite. Both the 1135 nm coffinite and 1157 nm zeolite absorption features overlap somewhat, potentially making them difficult to distinguish without additional hyperspectral field, laboratory or remote sensing data.The results of this study were compared to mixtures of minerals described for ore, gangue and alteration minerals in deposit models for sandstone-hosted uranium, sedimentary bentonite and sedimentary zeolite. Use of these spectra can help facilitate mapping of both waste materials from the legacy mining of the above commodities, as well as future exploration and resource assessment activities.

Diversified vegetation types on rangelands promote multiple soil‐based ecosystem services

AbstractRangelands have the potential to be provisioners of ecosystem services, including livestock products, carbon storage and greenhouse gas regulation, water and nutrient cycling, wildlife habitat, and biodiversity. Due to their vast extent and landscape heterogeneity, the degree to which different ecological components of rangelands contribute to ecosystem services can be varied. Soils are the foundation of rangeland health and associated ecosystem services. While many studies have examined the effect of grazing intensity on rangeland ecosystem services, few studies have looked at the broader rangeland landscape and how managing varying vegetation types can influence soil‐based ecosystem services. In this study, a suite of physical, chemical, and biological soil health indicators were measured in various vegetation types found within a working cattle ranch, including coastal live oak woodlands, coastal scrublands, annual grassland, and restored native perennial grassland. Based on the measured soil health indicators, results from this study show scrubland significantly diverges from other vegetation types, having higher water infiltration and plant available water, carbon stocks, and a more diverse microbial community that drives more dynamic cycling of carbon and nitrogen. Strategically maintaining scrubland on unproductive, highly erosive slopes downgradient of highly productive grassland areas could maintain forage production while protecting water quality and increasing carbon storage. These results highlight the relevance of holistically evaluating rangeland operations to assess soil function and ecosystem services and the potential risks and co‐benefits of varying vegetation types. Ultimately, process‐based linkages described here may provide a working example of how to manage ranches as functional mosaics of strategically maintained vegetation types.

Documenting Two Centuries of Change in Longleaf Pine (Pinus palustris) Forests of the Coastal Plain Province, Southeastern USA

While many tree species occur across the Coastal Plain of the southeastern United States, longleaf pine (Pinus palustris C. Lawson) savannas and woodlands once dominated this region. To quantify longleaf pine’s past primacy and trends in the Coastal Plain, we combined seven studies consisting of 255,000 trees from land surveys, conducted between 1810 and 1860 with other descriptions of historical forests, including change to the present day. Our synthesis found support that Pinus palustris predominantly constituted 77% of historical Coastal Plain trees and upland oaks (Quercus) contributed another 8%. While Pinus still dominates these forests today (58% of all trees), most are now either planted loblolly (Pinus taeda L.) or slash (Pinus elliottii Engelm.) pines. Water oak (Quercus nigra L.), live oak (Quercus virginiana Mill.), sweetgum (Liquidambar styraciflua L.), and red maple (Acer rubrum L.) have increased their proportions compared to historical surveys; both longleaf pine and upland oaks have declined to ≤5% of all trees. Our work also supports previous estimates that longleaf pine originally dominated over 25–30 million ha of Coastal Plain forests. As late as the early 1900s, longleaf pine may still have covered 20 million ha, but declined to 7.1 million ha by 1935 and dropped to 4.9 million ha by 1955. Longleaf pine’s regression continued into the mid-1990s, reaching a low of about 1.3 million ha; since then, restoration efforts have produced a modest recovery to 2.3 million ha. Two centuries of overcutting, land clearing, turpentining for chemicals, fire exclusion followed by forest densification by fire-sensitive species, and other silvicultural influences, including widespread loblolly and slash pine plantations, have greatly diminished the Coastal Plain’s once extensive open longleaf pine forests.

Laboratory quantification of firebrand generation from WUI fuels for model development

Firebrands play a critical role in the propagation of wildland fires, particularly in the wildland-urban interface (WUI). The mechanism behind fire spread by firebrands is not well understood despite being responsible for a majority of structure losses during WUI fires. This study quantifies the generation of firebrands from three typical WUI fuels (Douglas fir, eucalyptus globulus, and coast live oak) inside a laboratory-scale wind tunnel, to provide necessary data to model the spread of wildland fires into and within communities by burning embers. A comprehensive set of test conditions were considered, including the initial fuel mass, fuel moisture content, mean twig diameter, and crosswind speed. Results showed that the firebrand yields for all three fuel species were independent of the total dry mass lost, but positively correlated with the crosswind speed and negatively correlated to fuel moisture content and mean twig diameter. Meanwhile, the firebrand yields by mass of the fuels under the same test conditions have the following order: coast live oak >Douglas fir >eucalyptus globulus. Scaling analysis was performed to organize the data under different test conditions, and unique firebrand yield correlations were then obtained for each fuel species. In addition, the masses and projected areas of the firebrands for each fuel species had a linear fitting correlation, and the slope of the fitting line was positively correlated to fuel moisture content but insensitive to crosswind speed and mean twig diameter. The data and correlations disclosed in this study could be vital for future simulations of fire spread in both the wildland and WUI.

Teíchophoresis-enabled electrokinetic sample preparation and detection of calcium in natural plant samples

We present a novel upstream electrokinetic sample preparation and liquid interfacial microfluidic method to pre-concentrate, detect and quantify the concentration of a charged species, such as calcium, from a natural plant sample. We employ a new electrokinetic phenomenon, termed as “Teíchophoresis” (TPE) to preconcentrate sample calcium ions (up to a 20X increase) against a conductive wall. Using microfluidic flow, we then continuously transport the pre-concentrated calcium to a hydrodynamically streamed interfacial sensing zone where we utilize the model fluorescent chelation reaction between calcium and Calcium Green-1 (CG1) to fluorescently quantify the calcium concentration. Using a combination of finite element analysis and finite difference numerical modelling, we model the kinetics of the CG1-calcium interfacial binding and predictably validate our TPE-driven concentration results. Finally, we demonstrate the applicability of our device for real world samples by determining the calcium concentration in a tree bark extract acquired from a southern live oak and confirm our concentration results using ICP-MS.

Differential Stomatal Responses to Surface Permeability by Sympatric Urban Tree Species Advance Novel Mitigation Strategy for Urban Heat Islands

As urbanization draws more people to metropolitan areas, a steadfast increase in impervious surfaces ultimately contributes to a pronounced urban heat island effect. While city greening strategies to mitigate urban thermal effects often tout street-tree cover expansion, many plant species are susceptible to heat stress, limiting survivorship, primary productivity, and ecosystem services. Our research objective was to characterize how urban imperviousness impacted the photosynthetic traits of four sympatric tree species in Old Town La Verne, California. We found that while Camphor trees (Camphora officinarum) and Carrotwood trees (Cupaniopsis anacardioides) did not differ significantly in photosynthetic traits at sites with impervious and pervious surfaces, both Coast Live Oak trees (Quercus agrifolia) and Olive trees (Olea europaea) showed significant differences in leaf stomatal length and density. Our findings suggest that the photosynthetic traits of some exotic tree species may be less susceptible to surface permeability than either native or floristically indigenous tree species. We propose that urban greening initiatives adopt a temporal strategy for mitigating urban heat island effects, starting with an urban canopy composed of exotic trees more resilient to impervious surfaces and later transitioning to a recombinant canopy ecology of floristically relevant tree species suited for the soil permeability native to southern California.