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At least 451 records · Page 25Linked to original sources
USGS2018

Population genomic surveys for six rare plant species in San Diego County, California

San Diego County is a hotspot of biodiversity, situated at the intersection of the Baja peninsula, the California floristic province, and the desert southwest. This hotspot is characterized by a high number of rare and endemic species, which persist alongside a major urban epicenter. San Diego County has implemented a strategic management plan that identifies species, based on low numbers of occurrences or high level of threat, for which management practices are recommended. In creating a management plan for rare species, it is important to strike a balance between preserving locally adapted traits and maintaining genetic diversity, as species’ ranges fluctuate in response to a changing climate and habitat fragmentation. This project, in partnership with the San Diego Natural History Museum, aims to provide a reference point for the current status of genetic diversity of rare plant species that will inform future preservation and restoration efforts. We focused on six threatened or endangered plant species: Acanthomintha ilicifolia , Baccharis vanessae , Chloropyron maritimum ssp. maritimum , Deinandra conjugens , Dicranostegia orcuttiana , and Monardella viminea . For each species, botanists from the San Diego Natural History Museum visited all known occurrences in San Diego County and collected leaf tissue for genetic and cytological analysis. We then developed a panel of genetic markers to estimate genetic diversity and population structure. This population genetic survey provided insight into the amount of genetic differentiation across each species’ range, identified isolated occurrences potentially subject to inbreeding or genetic bottlenecks, and identified areas that are rich sources of allelic diversity. Finally, we convened a panel of experts to review results and compatible management options for each species. A summary of the management workshop is included in this report. Overall, we found low genetic differentiation among occurrences across the San Diego region for all species, with the exception of A. ilicifolia . Relative inbreeding was low and consistent across sites, and genetic diversity across sites was variable, with noted exceptions. These findings allow for a wide array of management options that are compatible with panmictic population structure in five of the six surveyed species.

California↗
USGS2016

Tolerance to multiple climate stressors: A case study of Douglas-fir drought and cold hardiness

Drought and freeze events are two of the most common forms of climate extremes which result in tree damage or death, and the frequency and intensity of both stressors may increase with climate change. Few studies have examined natural covariation in stress tolerance traits to cope with multiple stressors among wild plant populations. We assessed the capacity of coastal Douglas‐fir ( Pseudotsuga menziesii var. menziesii ), an ecologically and economically important species in the northwestern USA, to tolerate both drought and cold stress on 35 populations grown in common gardens. We used principal components analysis to combine drought and cold hardiness trait data into generalized stress hardiness traits to model geographic variation in hardiness as a function of climate across the Douglas‐fir range. Drought and cold hardiness converged among populations along winter temperature gradients and diverged along summer precipitation gradients. Populations originating in regions with cold winters had relatively high tolerance to both drought and cold stress, which is likely due to overlapping adaptations for coping with winter desiccation. Populations from regions with dry summers had increased drought hardiness but reduced cold hardiness, suggesting a trade‐off in tolerance mechanisms. Our findings highlight the necessity to look beyond bivariate trait–climate relationships and instead consider multiple traits and climate variables to effectively model and manage for the impacts of climate change on widespread species.

California, Oregon, Washington↗
USGS1996

Environmental hazards of aluminum to plants, invertebrates, fish, and wildlife

Aluminum (Al) is the third most common mineral and the most common metal in Earth’s crust, accounting for approximately 8.1% of the crust by weight. Thus, it cannot be considered a contaminant in the usual sense of the word. However, despite its near omnipresence throughout the world, Al has been of major concern as a primary limiting factor to cultivated plants for several decades. In much of the world, Al severely restricts the growth and presence of plant species. Since the late 1970s, concern about Al toxicity has spread to natural habitats, most notably forests and aquatic communities. The primary impetus for this concern has been the increased awareness of the effects of anthropogenic acidification through mine drainage, acid deposition, and other sources. The toxicity of Al is intimately associated with pH in that the metal is soluble and biologically available in acidic (pH <5.5) soils and waters but relatively innocuous in circumneutral (pH 5.5-7.5) conditions. Forest die-offs and reduced survivorship or impaired reproduction of aquatic invertebrates, fish, and amphibians have been directly connected to Al toxicity. Indirect effects on birds and mammals also have been identified. The purpose of this review is to summarize the toxic effects of Al to populations and to evaluate the potential hazards to the communities in which these populations are found.

Book chapter↗
USGS2006

When landscaping goes bad: The incipient invasion of Mahonia bealei in the southeastern United States

Woodlots are forest islands embedded within an urban matrix, and often represent the only natural areas remaining in suburban areas. Woodlots represent critical conservation areas for native plants, and are important habitat for wildlife in urban areas. Invasion by non-indigenous (NIS) plants can alter ecological structure and function, and may be especially severe in remnant forests where NIS propagule pressure is high. Woody shrubs in the Family Berberidaceae have been well documented as invaders of the forest-urban matrix in North America. Mahonia bealei (Berberidaceae) is a clonal shrub native to China, and is a popular ornamental in the Southeastern United States. Mahoni bealei is listed as "present" on some local and state floras, but almost nothing is known regarding its invasion potential in the United States. We sampled 15 woodlots in Clemson, South Carolina, to assess the invasion of M. bealei and other woody non-indigenous species (NIS). M. bealei invaded 87% of the woodlots surveyed and species richness of NIS on these woodlots varied from 5 to 14. Stepwise-multiple regression indicated that less canopy cover and older M. bealei predicted greater abundance of M. bealei , and that not all subdivisions were equally invaded (P < 0.0001; r 2 = 0.88). The impact of M. bealei on native flora and fauna may be considerable, and it is likely to continue to spread in the Southeastern United States. M. bealei should be recognized as an aggressive invader in the Southeastern United States, with the potential for negative impacts on native flora and fauna. ?? Springer 2006.

Biological Invasions↗
USGS2023

Variation in leaf reflectance spectra across the California flora partitioned by evolutionary history, geographic origin, and deep time

Evolutionary relatedness underlies patterns of functional diversity in the natural world. Hyperspectral remote sensing has the potential to detect these patterns in plants through inherited patterns of leaf reflectance spectra. We collected leaf reflectance data from across the California flora from plants grown in a common garden. Regions of the reflectance spectra vary in the depth and strength of phylogenetic signal. We also show that these differences are much greater than variation due to the geographic origin of the plant. At the phylogenetic extent of the California flora, spectral variation explained by the combination of ecotypic variation (divergent evolution) and convergent evolution of disparate lineages was minimal (3 to 7 %) but statistically significant. Interestingly, at the extent of a single genus ( Arctostaphylos ) no unique variation could be attributed to geographic origin. However, up to 18% of the spectral variation among Arctostaphylos individuals was shared between phylogeny and intraspecific variation stemming from ecotypic differences (i.e., geographic origin). Future studies could conduct more structured experiments (e.g., transplants or observations along environmental gradients) to disentangle these sources of variation and include other intraspecific variation (e.g., plasticity). We constrain broad scale spectral variability due to ecotypic sources, providing further support for the idea that phylogenetic clusters of species might be detectable through remote sensing. Phylogenetic clusters could represent a valuable dimension of biodiversity monitoring and detection.

California↗
USGS1999

Molecular aggregation of humic substances

Humic substances (HS) form molecular aggregates in solution and on mineral surfaces. Elucidation of the mechanism of formation of these aggregates is important for an understanding of the interactions of HS in soils arid natural waters. The HS are formed mainly by enzymatic depolymerization and oxidation of plant biopolymers. These reactions transform the aromatic and lipid plant components into amphiphilic molecules, that is, molecules that consist of separate hydrophobic (nonpolar) and hydrophilic (polar) parts. The nonpolar parts of the molecules are composed of relatively unaltered segments of plant polymers and the polar parts of carboxylic acid groups. These amphiphiles form membrane-like aggregates on mineral surfaces and micelle-like aggregates in solution. The exterior surfaces of these aggregates are hydrophilic, and the interiors constitute separate hydrophobic liquid-like phases.

Soil Science↗
USGS2011

Causes and implications of the correlation between forest productivity and tree mortality rates

At global and regional scales, tree mortality rates are positively correlated with forest net primary productivity (NPP). Yet causes of the correlation are unknown, in spite of potentially profound implications for our understanding of environmental controls of forest structure and dynamics and, more generally, our understanding of broad-scale environmental controls of population dynamics and ecosystem processes. Here we seek to shed light on the causes of geographic patterns in tree mortality rates, and we consider some implications of the positive correlation between mortality rates and NPP. To reach these ends, we present seven hypotheses potentially explaining the correlation, develop an approach to help distinguish among the hypotheses, and apply the approach in a case study comparing a tropical and temperate forest. Based on our case study and literature synthesis, we conclude that no single mechanism controls geographic patterns of tree mortality rates. At least four different mechanisms may be at play, with the dominant mechanisms depending on whether the underlying productivity gradients are caused by climate or soil fertility. Two of the mechanisms are consequences of environmental selection for certain combinations of life-history traits, reflecting trade-offs between growth and defense (along edaphic productivity gradients) and between reproduction and persistence (as manifested in the adult tree stature continuum along climatic and edaphic gradients). The remaining two mechanisms are consequences of environmental influences on the nature and strength of ecological interactions: competition (along edaphic gradients) and pressure from plant enemies (along climatic gradients). For only one of these four mechanisms, competition, can high mortality rates be considered to be a relatively direct consequence of high NPP. The remaining mechanisms force us to adopt a different view of causality, in which tree growth rates and probability of mortality can vary with at least a degree of independence along productivity gradients. In many cases, rather than being a direct cause of high mortality rates, NPP may remain high in spite of high mortality rates. The independent influence of plant enemies and other factors helps explain why forest biomass can show little correlation, or even negative correlation, with forest NPP.

Ecological Monographs↗
USGS2002

The flora of Oktibbeha County, Mississippi

We surveyed the flora of Oktibbeha County, Mississippi, U.S.A., from February 1994 to 1996. Occupying 118 square kilometers in east-central Mississippi, Oktibbeha County lies among 3 physiographic regions that include, from west to east, Interior Flatwoods, Pontotoc Ridge, and Black Prairie. Accordingly, the county harbors a diverse flora. Based on field work, as well as an extensive review of published literature and herbarium records at IBE and MISSA, we recorded a total of 1,148 taxa (1,125 species, 7 hybrids, 16 infraspecific taxa) belonging to 514 genera in 160 families, over 85% of all taxa documented were native. Compared to 3 other counties in east-central Mississippi, Oktibbeha County has the second largest recorded flora. The number of state-listed (endangered, threatened, or of special concern) taxa (67) documented in this survey far exceeds that reported from any other county in the region. Three introduced species, Ilex cornuta Lindl. & Paxton, Mahonia bealei (Fortune) Carrie??re, and Nandina domestica Thunb., are reported in a naturalized state for the first time from Mississippi. We also describe 16 different plant communities belonging to 5 broad habitat categories: bottomland forests, upland forests and prairies, aquatic habitats, seepage areas, and human-influenced habitats. A detailed description of the vegetation associated with each of these communities is provided.

SIDA, Contributions to Botany↗
USGS2010

Vegetation classification and distribution mapping report: Canyon de Chelly National Monument

Executive Summary: The classification and distribution mapping of the vegetation of Canyon de Chelly National Monument (CACH) and surrounding environment was accomplished through a multi-agency effort between 2003 and 2007. The National Park Service’s Southern Colorado Plateau Network facilitated the team that conducted the work, which comprised the U.S. Geological Survey’s Southwest Biological Science Center and Fort Collins Science Center, Navajo Natural Heritage Program, Northern Arizona University, and NatureServe. The project team described 48 plant communities for CACH—35 of which were described from quantitative classification based on field-relevé data collected in 2004. Five additional plant communities were based on field relevés collected in a previous study. The team derived four additional plant communities from field observations during the photointerpretation phase of the project, and field documented them during accuracy assessment. The National Vegetation Classification Standard served as a conceptual framework for assigning these plant communities to the alliance and association level. Ten of the 48 plant communities were designated “park specials”, that is, plant communities with insufficient data to describe them as new alliances or associations. The project team also developed a spatial vegetation map database representing CACH, with three different map-class schemas: base, group, and management map classes. The base map classes represented the finest level of spatial detail. Photointerpreters delineated initial polygons through manual interpretation of 2003/2004 1:12,000-scale true color aerial photography supplemented by occasional computer screen digitizing on a mosaic of digitized aerial photos. These polygons were labeled with base map classes during photointerpretation. Field visits verified interpretation concepts. The vegetation map database includes • ? 53 base map classes, which consist of associations and park specials classified with the quantitative analysis • ? additional associations noted during photointerpretation • ? non-vegetated land cover, such as infrastructure, land use, and geological land cover. The base map classes consist of 4,718 polygons in the project area. A field-based accuracy assessment of the base map classes showed the overall accuracy to be 50.8% The group map classes represent aggregations of the base map classes, approximating the group level of the National Vegetation Classification Standard, Version 2 (Federal Geographic Data Committee 2008). Terrestrial ecological systems, as described by NatureServe (Comer et al. 2003), were used as a first approximation of the group level. The project team identified 16 group map classes in this project. The overall accuracy of the group map classes was determined using the same accuracy assessment data as for the base map classes. The overall accuracy of the group representation of vegetation was 79.9%. In consultation with park staff, the team developed management map classes that consisted of park-defined groupings of base map classes and were intended to represent a balance between maintaining required accuracy and providing a focus on vegetation of particular interest or import to park managers. The 28 management map classes have an overall accuracy of 77.1%. While the main products of this project are the vegetation classification and the vegetation map database, a number of ancillary geographic information system and digital database products were also produced that can be used independently, or to augment the main products. These products include shapefiles of the location of field-collected data and relational databases of field-collected data.

Report↗
USGS2012

Introduction to emergent wetlands: Chapter A in Emergent wetlands status and trends in the northern Gulf of Mexico: 1950-2010

Throughout the past century, emergent wetlands have been declining across the Gulf of Mexico. Emergent wetland ecosystems provide a plethora of resources including plant and wildlife habitat, commercial and recreational economic activity, water quality improvement, and natural barriers against storms. As emergent wetland losses increase, so does the need for information on the causes and effects of these losses, for emergent wetland mapping, for monitoring and restoration efforts, and for increased education. The U.S. Geological Survey (USGS) and the U.S. Environmental Protection Agency’s Gulf of Mexico Program Office (EPA GMPO) are committed to providing the best science to restore, enhance, and protect these important ecosystems. The Emergent Wetlands Status and Trends Report is a continuation of the completed Seagrass Status and Trends in the Northern Gulf of Mexico Report (Handley and others, 2007), both of which serve to update the EPA GMPO Status and Trends of Emergent and Submerged Vegetated Habitats of Gulf of Mexico Coastal Waters, USA Report (Duke and Kruczynski, 1992). The Emergent Wetlands Status and Trends Report is also part of the Gulf of Mexico Alliance Ecosystems Integration and Assessment Priority Issue Team’s work plan to provide resources that will aid in the ecological and economic enhancement of the Gulf of Mexico region. The purpose of this report is to provide scientists, managers, and citizens with valuable baseline information on the status and trends of emergent wetlands along the coast of the Gulf of Mexico. The study upon which this report is based examines the emergent wetlands of eight individual estuarine areas within the northern Gulf of Mexico region and presents statewide summaries for Texas, Louisiana, Mississippi, Alabama, and Florida. Each estuarine area is detailed in vignettes that address current status and historical trends of estuarine and palustrine emergent wetlands, emergent wetlands mapping and monitoring, causes of status change, restoration and enhancement activities, background information for the study area, and the methodology employed to analyze and document the historical trends and current status of emergent wetlands. The eight individual estuarine areas examined in this report are:  Corpus Christi/ Nueces/Aransas Bays, Tex.  Galveston Bay, Tex.  Barataria/Terrebonne Bay, La.  Mississippi Delta, La.  Mississippi Sound, Miss.  Mobile Bay, Ala.  Florida Panhandle, Fla.  Tampa Bay, Fla.

Report↗
USGS1975

The geologic story of Isle Royale National Park

Isle Royale is an outstanding example of relatively undisturbed northwoods lake wilderness. But more than simple preservation of such an environment is involved in its inclusion in our National Park System. Its isolation from the mainland provides an almost untouched laboratory for research in the natural sciences, especially those studies whose very nature depends upon such isolation. One excellent example of such research is the intensive study of the predator-prey relationship of the timber wolf and moose, long sponsored by the National Park Service and Purdue University. In probably no other place in North America are the necessary ecological conditions for such a study so admirably fulfilled as on Isle Royale. The development of a natural laboratory with such conditions is ultimately dependent upon geologic processes and events that although not unique in themselves, produced in their interplay a unique result, the island archipelago as we know it today, with its hills and valleys, swamps and bogs the ecological framework of the plant and animal world. Even the most casual visitor can hardly fail to be struck by the fiordlike nature of many of the bays, the chains of fringing islands, the ridge-and-valley topography, and the linear nature of all these features. The distinctive topography of the archipelago is, of course, only the latest manifestation of geologic processes in operation since time immemorial. Fragments of geologic history going back over a billion years can be read from the rocks of the island, and with additional data from other parts of the Lake Superior region, we can fill in some of the story of Isle Royale. After more than a hundred years of study by man, the story is still incomplete. But then, geologic stories are seldom complete, and what we do know allows a deeper appreciation of one of our most naturally preserved parks and whets our curiosity about the missing fragments.

Michigan↗
USGS2024

Oil and gas development influences potential for dust emission from the Upper Colorado River Basin, USA

Wind erosion and dust emission from drylands have large consequences for ecosystem function and human health. Wind erosion is naturally reduced by soil crusting and sheltering by non-erodible roughness elements such as plants. Land uses that reduce surface roughness and disturb the soil surface can dramatically increase dust emission. Extraction of oil and gas is a common and growing land use in the western United States (US) that removes vegetation and other roughness elements for construction of well pads and unpaved access roads, resulting in thousands of small (1–4 ha), discrete patches of unprotected soil. Here, we use a satellite albedo-based model to assess the effect of oil/gas activity on surface roughness in the Uinta-Piceance Basin, an area of the Upper Colorado River Basin (UCRB) with dense oil and natural gas development and modelled how the change in surface roughness could impact aeolian sediment flux and dust emission. We also investigated how regional drought influences the response of surface roughness to well pads and access roads. Oil/gas activity reduced surface roughness and increased modelled aeolian sediment flux at the landscape scale across much of the study region, resulting in a modest increase of 10 139 kg of dust per year, which is small relative to dust loads from a single regional dust event observed in the region, but downwind impact could be significant. The magnitude of surface roughness reductions by oil/gas activity was generally consistent among land cover types. However, in parts of the basin that had high cover of annual forbs and grasses, oil/gas activity was associated with larger surface roughness and smaller potential dust emission. Drought decreased surface roughness across disturbed and undisturbed sites, but there was no interactive effect of oil/gas activity and drought on surface roughness. These results suggest that oil/gas activity may increase sediment fluxes and likely contributes to dust emission from landscapes in the UCRB. Understanding how drought and land use change contribute to dust emissions will benefit mitigation of undesirable impacts of wind erosion and dust transport.

Colorado, Utah↗
USGS2003

Dynamics of peat accumulation and marl flat formation in a calcareous fen, midwestern United States

The age and sequence of peat accumulation were investigated at a calcareous fen in northeastern Illinois, USA. The purpose of this study was to identify the processes that form and sustain marl flats, which are areas of marl or tufa substrate within the fen that contain numerous rare plant species. Geomorphic, stratigraphic, and radiocarbon evidence was used to establish the processes and chronology of peat accumulation and erosion adjacent to each marl flat. The age of the base of the peat deposit varies greatly throughout the fen, ranging from 14,679 calibrated years before present (cal. years BP) to nearly modern, indicating that colonization of the sand and gravel substrate by peat occurred throughout the period from the Late Pleistocene to present. Adjacent to one marl flat, trends in basal peat age and thickness show that peat accumulation has progressed laterally inward from both sides, suggesting that the marl flat has been infilling with peat progressively by accumulation at the margins since at least 5,370 cal. years BP or longer. A second marl flat in the fen is surrounded by older, thick peat of differing ages on either edge and is bounded by fresh scarps, indicating that the marl flat currently is expanding laterally by erosion into the preexisting peat blanket. These two examples suggest a continuously repeating process, where erosion of the accumulated peat blanket forms a marl flat, which is later covered by peat accumulation. Trends in basal peat age elsewhere in the fen suggest that other marl flats may have existed in the past that have been completely infilled with peat. This study suggests that marl flat formation is a natural process that has been occurring for millennia, continuously creating habitat for the rare plant species that occupy marl flats. There is no evidence that the marl flats at this site are indicative of anthropogenic disturbance, so that management options for these areas are limited to maintaining the quality and quantity of ground-water discharge that supports both peat formation and erosion. ?? 2003, The Society of Wetland Scientists.

Wetlands↗
USGS1984

Stable isotope compositions of gases and vegetation near naturally burning coal

Our measurements of stable isotope compositions of CO2 issuing from vents produced by naturally burning coal indicate that the coal is oxidized through a kinetic process in which groundwater is the oxidizing agent. The CO2 produced by the oxidation of the coal is extremely depleted in 13C relative to normal atmospheric CO2. The change in the ??13C value of atmospheric CO2 near the vents resulting from the burning coal was not recorded in tree rings from red cedars, but the ??13C values of some C3 and C4 type plants collected from within the area were greatly affected. Our results indicate that the ??13C values of some species of plants may be sensitive indicators of changes in the carbon isotopic composition of atmospheric CO2. ?? 1984 Nature Publishing Group.

Nature↗
USGS2026

Leveraging local species data, a global database, and an occupancy model to explore bee–plant interactions

Global declines in bee populations are threatening the ecosystem services they provide, including pollination. Many bee–plant interactions are understudied, producing an incomplete understanding of resulting ecosystem-level vulnerabilities. The last decade has generated a wealth of opportunistic data originating from natural history collection records, published ecological datasets, and citizen/community science initiatives in online databases such as Global Biotic Interactions (GloBI). Here, we explore hypotheses related to bee–plant interactions and detection processes using the GloBI database, curated checklists of bee and flowering plant species, and an occupancy model. We hypothesized that larger, social bees would visit a larger number of plant species, while smaller, solitary bees would visit fewer. We also predicted that flowers with open, bowl-like shapes would attract a greater diversity of bee visitors compared to closed shapes. Further, we hypothesized that both floral and bee traits, such as bright colors and conspicuous patterns, would increase detectability, and that different data collection methods would vary in their ability to capture bee–plant interactions. Lastly, we hypothesized that the interaction network generated by the output of the occupancy model, which accounted for imperfect bee–plant detection, would yield more interactions, thereby increasing measures of evenness and decreasing nestedness and specialization, as compared to the network generated from recorded interaction data. We found that smaller bees exhibited higher probabilities of plant interactions than larger bees, but we did not find evidence that bee sociality influenced the probability of interacting with plants. We found that blue flowers and closed (not-bowl-shaped) flowers had higher probabilities of bee-plant interaction than other flower colors or bowl-shaped flowers, respectively. We also found that larger bee size, blue flowers, bowl shapes, and community science sources were associated with higher detection probabilities of bee–plant interactions. Lastly, the interaction network generated by the occupancy model output showed higher levels of evenness, nestedness, and connectance than the network generated by the GloBI data. Our study is among the first to utilize occupancy modeling to directly model species' interactions, leverage aggregated, open-source databases and expert checklists, and highlight the influence of detection and collection biases on our understanding of ecological interactions.

California↗
USGS1995

Effects of agricultural, industrial, and municipal pollutants on wetlands and wildlife and wildlife health

Wetlands accumulate pollutants from adjacent areas through intentional discharge of sewage or industrial wastes, runoff of agricultural fertilizers and pesticides, and discharge from municipal storm drains. Coastal wetlands receive more pollutants indirectly as the endpoint for upland drainage systems and directly through petroleum spills and insect abatement. Wetlands that serve as evaporation basins during seasonally high water, especially in more arid climates, concentrate natural compounds and as well as pollutants. The ability of wetlands to be effective filtration systems for wastewater nutrients through microbial transformations, uptake by plants, and deposition of particulate matter, and the shortage of water in arid climates has resulted in revision of wetland regulations. Wetlands can now be developed for wastewater treatment and natural wetlands can be restored or converted to wastewater treatment systems. The effect of these accumulation pollutants on wetland ecology and wildlife health needs to be recognized.

Conference Paper↗
USGS2006

Vascular Plant and Vertebrate Inventory of Saguaro National Park, Rincon Mountain District

Executive Summary This report summarizes the results of the first comprehensive inventory of plants and vertebrates at the Rincon Mountain District (RMD) of Saguaro National Park, Arizona. From 2001 to 2003 we surveyed for vascular plants and vertebrates (amphibians, reptiles, birds, and mammals) at the district to document the presence of species within its boundaries. Park staff also surveyed for medium and large mammals using infrared-triggered cameras from 1999 to 2005. This report summarizes the methods and results of these two efforts. Our spatial sampling design was ambitious and was one of the first of its kind in the region to colocate study sites for vegetation and vertebrates using a stratified random design. We also chose the location of some study sites non-randomly in areas that we thought would have the highest species richness. Because we used repeatable study designs and standardized field methods, these inventories can serve as the first step in a biological monitoring program for the district. We also provide an important overview of most previous survey efforts in the district. We use data from our inventory and other surveys to compile species lists and to assess inventory completeness. With the exception of plants, our survey effort was the most comprehensive ever undertaken in the district. We recorded a total of 801 plant and vertebrate species, including 50 species not previously found in the district (Table 1) of which five (all plants) are non-native species. Based on a review of our inventory and past research at the district, there have been a total of 1,479 species of plants and vertebrates found there. We believe inventories for all taxonomic groups are nearly complete. In particular, the plant, amphibian and reptile, and mammal species lists are the most complete of any comparably large natural area of the 'sky island' region of southern Arizona and adjacent Mexico. For each taxon-specific chapter we discuss patterns of species richness and environmental determinants of these patterns. For all groups except medium and large mammals, the low elevation stratum (<4,000 feet) contained the highest species richness, after accounting for differences in survey effort among strata. This is consistent with known patterns of species richness in the sky island mountain ranges. Using data on relative abundance for plants and birds, we were able to identify a number of distinct ecological communities, which were consistent with known patterns in the sky islands. Our review of species lists and park records reveals that the district has lost species, particularly plants and mammals, in the past few decades. Because of the district's close proximity to the rapidly growing city of Tucson, there are a number of development-related threats that could cause additional species loss or decline in abundance of some species. In particular, the increasing groundwater pumping near Rincon Creek, the most species-rich area in the park, is likely to impact the unique riparian vegetation and animals of that area. We discuss this and other demands on the ecological integrity of the district. We also recommend additional inventory, monitoring, and research studies.

Open-File Report↗
USGS2015

Biodiversity influences plant productivity through niche–efficiency

The loss of biodiversity is threatening ecosystem productivity and services worldwide, spurring efforts to quantify its effects on the functioning of natural ecosystems. Previous research has focused on the positive role of biodiversity on resource acquisition (i.e., niche complementarity), but a lack of study on resource utilization efficiency, a link between resource and productivity, has rendered it difficult to quantify the biodiversity–ecosystem functioning relationship. Here we demonstrate that biodiversity loss reduces plant productivity, other things held constant, through theory, empirical evidence, and simulations under gradually relaxed assumptions. We developed a theoretical model named niche–efficiency to integrate niche complementarity and a heretofore-ignored mechanism of diminishing marginal productivity in quantifying the effects of biodiversity loss on plant productivity. Based on niche–efficiency, we created a relative productivity metric and a productivity impact index (PII) to assist in biological conservation and resource management. Relative productivity provides a standardized measure of the influence of biodiversity on individual productivity, and PII is a functionally based taxonomic index to assess individual species’ inherent value in maintaining current ecosystem productivity. Empirical evidence from the Alaska boreal forest suggests that every 1% reduction in overall plant diversity could render an average of 0.23% decline in individual tree productivity. Out of the 283 plant species of the region, we found that large woody plants generally have greater PII values than other species. This theoretical model would facilitate the integration of biological conservation in the international campaign against several pressing global issues involving energy use, climate change, and poverty.

Proceedings of the National Academy of Sciences of↗