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• 11. [Article] Soil community dynamics in sagebrush and cheatgrass-invaded ecosystems of the northern Great Basin

  Sagebrush steppe ecosystems in the Great Basin have become increasingly threatened by the proliferation of cheatgrass (Bromus tectorum L.), an invasive annual grass. Diverse sagebrush and perennial bunchgrass ...

  Citation × Citation Citation Abstract Copy Title: Soil community dynamics in sagebrush and cheatgrass-invaded ecosystems of the northern Great Basin Author: DeCrappeo, Nicole M. Sagebrush steppe ecosystems in the Great Basin have become increasingly threatened by the proliferation of cheatgrass (Bromus tectorum L.), an invasive annual grass. Diverse sagebrush and perennial bunchgrass landscapes can be converted to homogenous cheatgrass grasslands mainly through the effects of fire. Although the consequences of this conversion are well understood in the context of plant community dynamics, information on changes to soil communities has not been well documented. I characterized soil surface, microbial, and nematode community dynamics in sagebrush steppe and cheatgrass-invaded areas across the northern Great Basin. I also examined how restoration treatments, such as seeding with a low impact rangeland drill and applying herbicide or sugar to plots, affected soil communities. Soil community functional diversity and structure were alike at sites where soil pH and percent bare ground were similar. Rangeland drill seeding and associated human trampling decreased biological soil crust cover at sites with high proportions of cyanobacteria. Herbicide treatments had little effect on soil communities, but addition of sugar to plots increased carbohydrate utilization and fungal biomass of cheatgrass- invaded soils. In studying paired intact and cheatgrass-invaded sagebrush plots, I found that microbial functional diversity and community composition were different in sagebrush, bunchgrass, cheatgrass, and interspace soils. Fungal biomass and species richness were highest under sagebrush and decreased under cheatgrass. To examine how soil community shifts might affect ecosystem processes, I investigated the contribution of fungi to inorganic nitrogen (N) mineralization in sagebrush and cheatgrass rhizospheres. Results from a ¹⁵N pool dilution experiment modified with the fungal protein synthesis inhibitor cycloheximide showed that gross and net N cycling rates did not differ between control sagebrush and cheatgrass soils and that fungi were important for gross NH₄⁺ production and consumption in both soil types. However, net nitrification increased in sagebrush soils after 24 h, suggesting that when organic matter decomposition by fungi ceased bacteria became carbon limited and could no longer assimilate NH₄⁺. These studies demonstrate that cheatgrass invasion into sagebrush steppe ecosystems can bring about significant changes to soil communities and that these changes may have repercussions for ecosystem functioning in the northern Great Basin. Title: Soil community dynamics in sagebrush and cheatgrass-invaded ecosystems of the northern Great Basin Author: DeCrappeo, Nicole M. Sagebrush steppe ecosystems in the Great Basin have become increasingly threatened by the proliferation of cheatgrass (Bromus tectorum L.), an invasive annual grass. Diverse sagebrush and perennial bunchgrass landscapes can be converted to homogenous cheatgrass grasslands mainly through the effects of fire. Although the consequences of this conversion are well understood in the context of plant community dynamics, information on changes to soil communities has not been well documented. I characterized soil surface, microbial, and nematode community dynamics in sagebrush steppe and cheatgrass-invaded areas across the northern Great Basin. I also examined how restoration treatments, such as seeding with a low impact rangeland drill and applying herbicide or sugar to plots, affected soil communities. Soil community functional diversity and structure were alike at sites where soil pH and percent bare ground were similar. Rangeland drill seeding and associated human trampling decreased biological soil crust cover at sites with high proportions of cyanobacteria. Herbicide treatments had little effect on soil communities, but addition of sugar to plots increased carbohydrate utilization and fungal biomass of cheatgrass- invaded soils. In studying paired intact and cheatgrass-invaded sagebrush plots, I found that microbial functional diversity and community composition were different in sagebrush, bunchgrass, cheatgrass, and interspace soils. Fungal biomass and species richness were highest under sagebrush and decreased under cheatgrass. To examine how soil community shifts might affect ecosystem processes, I investigated the contribution of fungi to inorganic nitrogen (N) mineralization in sagebrush and cheatgrass rhizospheres. Results from a ¹⁵N pool dilution experiment modified with the fungal protein synthesis inhibitor cycloheximide showed that gross and net N cycling rates did not differ between control sagebrush and cheatgrass soils and that fungi were important for gross NH₄⁺ production and consumption in both soil types. However, net nitrification increased in sagebrush soils after 24 h, suggesting that when organic matter decomposition by fungi ceased bacteria became carbon limited and could no longer assimilate NH₄⁺. These studies demonstrate that cheatgrass invasion into sagebrush steppe ecosystems can bring about significant changes to soil communities and that these changes may have repercussions for ecosystem functioning in the northern Great Basin. Close

• 12. [Article] Genesis of some soils in the central western Cascades of Oregon

  Soils representative of several landscape units in the H. J. Andrews Experimental Forest, Western Cascade Range, were sampled, analyzed, and tentatively classified. Genetic inferences were drawn relating ...

  Citation × Citation Citation Abstract Copy Title: Genesis of some soils in the central western Cascades of Oregon Author: Brown, R. B. Soils representative of several landscape units in the H. J. Andrews Experimental Forest, Western Cascade Range, were sampled, analyzed, and tentatively classified. Genetic inferences were drawn relating soils to landscape position and other factors of soil formation. Descriptive information and nutrient capital data were provided to support ecosystem modelling efforts by the Coniferous Forest Biome study group of the U. S./International Biological Program (IBP). To meet the "nutrient capital" requirements of IBP, and to gain insight particularly into the effects of coarse fragments on soil genesis, a volumetric approach was used. Soil organic matter, total N, extractable P, exchangeable cations, free Fe oxides, and cation exchange capacity were expressed in terms of weight or equivalents per unit volume of "whole soil," defined as organic and mineral fine earth components plus pore space plus coarse fragments. The various entities, in grams or equivalents per liter of whole soil, were observed as to their variation with depth. Additional calculations showed levels of the various entities per surface meter ³ of whole soil. Soil temperature data from several sites within the Andrews Forest showed the mesic-frigid soil temperature regime boundary to fall at about the 600 m (2, 000 ft) elevation on south slopes and at about the 450 m (1, 500 ft) elevation on north slopes. The frigidcryic boundary apparently was above the 1, 500 m (4,900 ft) elevation in the Andrews Forest. A sequence of three fluvial and two colluvial soils ranging in elevation from 440 to 460 m was studied in conjunction with concurrent IBP investigations into the geomorphic history of the area The soil on a floodplain adjacent to Lookout Creek, in the sandy-skeletal, mixed, mesic family of Fluventic Hapludolls, was between 500 and 7, 000 yrs in age. The adjacent stream terrace soil, in the loamyskeletal, mixed, mesic family of Fluventic Dystrochrepts, was > 7, 000 yrs old as evidenced Mazama pumice erposi tE-; on or near the surface of the terrace. Volumetric analysis suggested that the floodplain soil had a mollic epipedon largely by virtue of its high content of coarse fragments. The coarse fragments caused a concentration of soil organic matter and recycled cations into a smaller volume of fine earth as compared with the terrace soil, which was lower in coarse fragments. An alluvial-colluvial fan emanated from an adjacent slope and lapped onto the terrace. The soil in this fan was a member of the Fluventic Eutrochrepts, loamy-skeletal, mixed, mesic. It was high in base status and moderately high in clay content, apparently because the southeast-facing source area for parent material here had experienced only shallow weathering and minimal leaching. Across Lookout Creek from these landscape units was a remnant of a high colluvial terrace emanating from a northwest-facing watershed. At the crest of this fan remnant the soil was a member of the loamy-skeletal, mixed, mesic family of Fluventic Dystrochrepts with a distinct layer of Mazama pumice at the 75 to 85 cm depth. This terrace is cut by the watershed stream, which has deposited a comparatively well sorted fan. Soils are in the coarseloamy, mixed, mesic family of Fluventic Dystrochrepts, Eight landscape units in longitudinal and transverse crosssections of upper McRae Creek valley, ranging in elevation from 800 to 1, 200 m, were chosen to study upland soil genesis. Proceeding up the valley, stage of profile development appeared to decrease, indicating a series of depositional events. Soils varied from Eutric Glossoboralfs, fine, mixed on the lowermost surface to Fluventic Dystrochrepts, fine-loamy, mixed, frigid on the next higher surface, to Fluventic Dystrochrepts, loamy-skeletal, mixed, frigid on the next higher surface, to Typic Haplumbrepts, loamy-skeletal, mixed, frigid on the backslope at the valley headwall. The two lowermost soils contrasted markedly with the two uppermost soils, being lower in content of organic matter and N, and higher in base status and clay content. The upper two soils, typical of upper valley bottom and sideslope soils in the region, were extremely low in exchangeable bases and base saturation as measured at pH 7. Compared with the two lower soils, however, these upper soils had relatively high soil: water pH values and relatively small drops in pH from soil:water to soil :KCI measurement. This may be an indication that the upper soils were higher in amorphous content. Greater pH-dependent-CEC would have caused the upper soils to exhibit unrealistically high CEO s--and thus low base saturations--when measured at pH 7. A topoclimosequence of soils on north, east (saddle), and south-facing landscape units with a single parent rock lithology was studied in the transverse valley transect. All three soils were placed tentatively in the Andic Dystrochrepts. The north-facing soil was in a medial - skeletal, frigid family, was the deepest to bedrock ( > 1 1/2 m), aria had the freshest coarse fragments of the three soils. The saddle and south-facing soils were in medial-skeletal, frigid and medial, frigid families, respectively. They were shallow ( <1 m) to saprolite bedrock, with well weathered coarse fragments in the regolith, demonstrating shallower, but apparently more intense weathering on the more exposed sites. These more exposed soils were darker in color than the north-facing soil. Soil organic matter levels were not strikingly different among the three soils. Soil N levels were significantly higher in the south-facing soil than in the east and north-facing soils. Levels of exchangeable bases, while low, were not as low in these three soils as in the upper valley bottom and backslope soils. Saprolite horizons had higher base saturations than overlying horizons. Title: Genesis of some soils in the central western Cascades of Oregon Author: Brown, R. B. Soils representative of several landscape units in the H. J. Andrews Experimental Forest, Western Cascade Range, were sampled, analyzed, and tentatively classified. Genetic inferences were drawn relating soils to landscape position and other factors of soil formation. Descriptive information and nutrient capital data were provided to support ecosystem modelling efforts by the Coniferous Forest Biome study group of the U. S./International Biological Program (IBP). To meet the "nutrient capital" requirements of IBP, and to gain insight particularly into the effects of coarse fragments on soil genesis, a volumetric approach was used. Soil organic matter, total N, extractable P, exchangeable cations, free Fe oxides, and cation exchange capacity were expressed in terms of weight or equivalents per unit volume of "whole soil," defined as organic and mineral fine earth components plus pore space plus coarse fragments. The various entities, in grams or equivalents per liter of whole soil, were observed as to their variation with depth. Additional calculations showed levels of the various entities per surface meter ³ of whole soil. Soil temperature data from several sites within the Andrews Forest showed the mesic-frigid soil temperature regime boundary to fall at about the 600 m (2, 000 ft) elevation on south slopes and at about the 450 m (1, 500 ft) elevation on north slopes. The frigidcryic boundary apparently was above the 1, 500 m (4,900 ft) elevation in the Andrews Forest. A sequence of three fluvial and two colluvial soils ranging in elevation from 440 to 460 m was studied in conjunction with concurrent IBP investigations into the geomorphic history of the area The soil on a floodplain adjacent to Lookout Creek, in the sandy-skeletal, mixed, mesic family of Fluventic Hapludolls, was between 500 and 7, 000 yrs in age. The adjacent stream terrace soil, in the loamyskeletal, mixed, mesic family of Fluventic Dystrochrepts, was > 7, 000 yrs old as evidenced Mazama pumice erposi tE-; on or near the surface of the terrace. Volumetric analysis suggested that the floodplain soil had a mollic epipedon largely by virtue of its high content of coarse fragments. The coarse fragments caused a concentration of soil organic matter and recycled cations into a smaller volume of fine earth as compared with the terrace soil, which was lower in coarse fragments. An alluvial-colluvial fan emanated from an adjacent slope and lapped onto the terrace. The soil in this fan was a member of the Fluventic Eutrochrepts, loamy-skeletal, mixed, mesic. It was high in base status and moderately high in clay content, apparently because the southeast-facing source area for parent material here had experienced only shallow weathering and minimal leaching. Across Lookout Creek from these landscape units was a remnant of a high colluvial terrace emanating from a northwest-facing watershed. At the crest of this fan remnant the soil was a member of the loamy-skeletal, mixed, mesic family of Fluventic Dystrochrepts with a distinct layer of Mazama pumice at the 75 to 85 cm depth. This terrace is cut by the watershed stream, which has deposited a comparatively well sorted fan. Soils are in the coarseloamy, mixed, mesic family of Fluventic Dystrochrepts, Eight landscape units in longitudinal and transverse crosssections of upper McRae Creek valley, ranging in elevation from 800 to 1, 200 m, were chosen to study upland soil genesis. Proceeding up the valley, stage of profile development appeared to decrease, indicating a series of depositional events. Soils varied from Eutric Glossoboralfs, fine, mixed on the lowermost surface to Fluventic Dystrochrepts, fine-loamy, mixed, frigid on the next higher surface, to Fluventic Dystrochrepts, loamy-skeletal, mixed, frigid on the next higher surface, to Typic Haplumbrepts, loamy-skeletal, mixed, frigid on the backslope at the valley headwall. The two lowermost soils contrasted markedly with the two uppermost soils, being lower in content of organic matter and N, and higher in base status and clay content. The upper two soils, typical of upper valley bottom and sideslope soils in the region, were extremely low in exchangeable bases and base saturation as measured at pH 7. Compared with the two lower soils, however, these upper soils had relatively high soil: water pH values and relatively small drops in pH from soil:water to soil :KCI measurement. This may be an indication that the upper soils were higher in amorphous content. Greater pH-dependent-CEC would have caused the upper soils to exhibit unrealistically high CEO s--and thus low base saturations--when measured at pH 7. A topoclimosequence of soils on north, east (saddle), and south-facing landscape units with a single parent rock lithology was studied in the transverse valley transect. All three soils were placed tentatively in the Andic Dystrochrepts. The north-facing soil was in a medial - skeletal, frigid family, was the deepest to bedrock ( > 1 1/2 m), aria had the freshest coarse fragments of the three soils. The saddle and south-facing soils were in medial-skeletal, frigid and medial, frigid families, respectively. They were shallow ( <1 m) to saprolite bedrock, with well weathered coarse fragments in the regolith, demonstrating shallower, but apparently more intense weathering on the more exposed sites. These more exposed soils were darker in color than the north-facing soil. Soil organic matter levels were not strikingly different among the three soils. Soil N levels were significantly higher in the south-facing soil than in the east and north-facing soils. Levels of exchangeable bases, while low, were not as low in these three soils as in the upper valley bottom and backslope soils. Saprolite horizons had higher base saturations than overlying horizons. Close

• 13. [Article] Beyond smoke and mirrors: a synthesis of fire policy and science

  Fire performs many beneficial ecosystem functions in dry forests and rangelands across much of North America. In the last century, however, the role of fire has been dramatically altered by numerous anthropogenic ...

  Citation × Citation Citation Abstract Copy Title: Beyond smoke and mirrors: a synthesis of fire policy and science Author: Deacon Williams, Cindy, Williams, Jack E., Franklin, Jerry F., Dellasala, Dominick A. Fire performs many beneficial ecosystem functions in dry forests and rangelands across much of North America. In the last century, however, the role of fire has been dramatically altered by numerous anthropogenic factors acting as root causes of the current fire crisis, including widespread logging, road building, fire suppression, habitat fragmentation, urban development, livestock grazing, and, more recently, climate change. The intensity and extent of fires in the western United States, specifically, have dramatically increased over the past several decades. Such shifts in fire behavior have triggered sweeping policy changes that were intended to prevent or contain fires but that pose significant risks to the integrity of ecosystems and the role fire historically played in shaping them. Here, we provide a social and ecological context for summarizing this special issue on fires, including general guidelines and principles for managers concerned about balancing the risks of inaction against the risks of action over extensive areas. Fundamental to our understanding of fire is the notion that it is extremely variable, has multiple causes, and requires ecological solutions that are sensitive to spatial scale and context. Therefore, forest managers must recognize that different forest types have different fire regimes and require fundamentally different fire- management policies. Furthermore, to restore or maintain ecological integrity, including the role of fire, treatments need to be tailored to site-specific conditions with an adaptive approach. We provide a conceptual framework for prioritizing fuel treatments and restoration activities in the wildlands-urban intermix versus those in wildland areas farther from human settlement. In general, the science of conservation biology has much to offer in helping to shape wildfire policy direction; however, conservation biologists must become more engaged to better ensure that policy decisions are based on sound science and that ecological risks are incorporated. Title: Beyond smoke and mirrors: a synthesis of fire policy and science Author: Deacon Williams, Cindy, Williams, Jack E., Franklin, Jerry F., Dellasala, Dominick A. Fire performs many beneficial ecosystem functions in dry forests and rangelands across much of North America. In the last century, however, the role of fire has been dramatically altered by numerous anthropogenic factors acting as root causes of the current fire crisis, including widespread logging, road building, fire suppression, habitat fragmentation, urban development, livestock grazing, and, more recently, climate change. The intensity and extent of fires in the western United States, specifically, have dramatically increased over the past several decades. Such shifts in fire behavior have triggered sweeping policy changes that were intended to prevent or contain fires but that pose significant risks to the integrity of ecosystems and the role fire historically played in shaping them. Here, we provide a social and ecological context for summarizing this special issue on fires, including general guidelines and principles for managers concerned about balancing the risks of inaction against the risks of action over extensive areas. Fundamental to our understanding of fire is the notion that it is extremely variable, has multiple causes, and requires ecological solutions that are sensitive to spatial scale and context. Therefore, forest managers must recognize that different forest types have different fire regimes and require fundamentally different fire- management policies. Furthermore, to restore or maintain ecological integrity, including the role of fire, treatments need to be tailored to site-specific conditions with an adaptive approach. We provide a conceptual framework for prioritizing fuel treatments and restoration activities in the wildlands-urban intermix versus those in wildland areas farther from human settlement. In general, the science of conservation biology has much to offer in helping to shape wildfire policy direction; however, conservation biologists must become more engaged to better ensure that policy decisions are based on sound science and that ecological risks are incorporated. Close

• 14. [Article] Towards a cohesive, holistic view of top predation: a definition, synthesis and perspective

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Authors and the Nordic Society Oikos. It is published by John Wiley & Sons, ...

  Citation × Citation Citation Abstract Copy Title: Towards a cohesive, holistic view of top predation: a definition, synthesis and perspective Author: Schmitz, Oswald J., et al., Krebs, Charles J., Ripple, William J., Sergio, Fabrizio This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Authors and the Nordic Society Oikos. It is published by John Wiley & Sons, Inc., and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291600-0706 Title: Towards a cohesive, holistic view of top predation: a definition, synthesis and perspective Author: Schmitz, Oswald J., et al., Krebs, Charles J., Ripple, William J., Sergio, Fabrizio This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Authors and the Nordic Society Oikos. It is published by John Wiley & Sons, Inc., and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291600-0706 Close

• 15. [Article] The influence of herbivore generated inputs on nutrient cycling and soil processes in a lower montane tropical rain forest of Puerto Rico

  The role of insect herbivores in the nutrient cycling dynamics of forest ecosystems remains poorly understood. Although past research in herbivory has focused primarily on the deleterious effects that ...

  Citation × Citation Citation Abstract Copy Title: The influence of herbivore generated inputs on nutrient cycling and soil processes in a lower montane tropical rain forest of Puerto Rico Author: Fonte, Steven J. The role of insect herbivores in the nutrient cycling dynamics of forest ecosystems remains poorly understood. Although past research in herbivory has focused primarily on the deleterious effects that insects can have on tree growth and mortality, the overall effects of herbivory are more complex. Herbivores have the potential to alter key ecosystem processes in a number of ways. One is by altering the flow of nutrients from the canopy to the forest floor. The studies presented here examine the effects that frass (insect excreta), greenfall (green leaf fragments) and herbivore modified throughfall, have on decomposition processes and soil nutrient dynamics. Both studies were carried out in a lower montane tropical rain forest near the El Verde Field Station, Luquillo Long-Term Ecological Research (LTER) site, Puerto Rico. The first study presented here tested the hypotheses that green leaves are of higher quality and decompose more rapidly than senesced leaves. Green and senesced leaves of four common native tree species (Dacryodes excelsa, Manilkara bidentata, Guarea guidonia and Cecropia schreberiana), were collected and analyzed for C, N, and complex C compounds. Litterbags containing green and senescent leaves of each species were placed in the field for up to 16 weeks in order to compare rates of litter decomposition. Green leaves contained significantly higher (p < 0.05) concentrations of N and lower lignin:N ratios than senescent leaves for all four species. Decomposition rates were significantly higher (p < 0.05) for green leaves compared to senescent leaves for all four species. These results demonstrate that insect herbivores may influence key ecosystem processes via the production of greenfall. The relevance of this study extends to green leaf deposition resulting from multiple sources, including high wind and rain events, as well as disturbance by larger canopy organisms. The second study tested a direct link between herbivory and soil processes. By altering levels of herbivory on a common understory plant (Piper glabrescens), using a prevalent folivore (Lamponius portoricensis), this study tested for effects of herbivory on nutrient inputs to the soil, as well as rates of litter decomposition. Enclosures were constructed around P. glabrescens individuals in the field and assigned to one of four treatments: herbivore exclusion, control, low herbivory and high herbivory. Total leaf area loss and greenfall production were measured for each plant using a sub-sample of randomly chosen leaves. Litterbags and ion exchange resin bags, placed under each plant, recorded rates of litter decomposition and the flow of NO3, NH4 and PO4 to the forest floor during this 76-day experiment. The treatments were effective in establishing a wide range of herbivory. Both the total leaf area removed and greenfall deposition demonstrated significant positive correlations (p <0.05) with NO3 transfer to the forest floor, but not with NH4 or PO4. Although decomposition rates showed no significant correlation with total leaf area losses or the greenfall component, a significant correlation was found between decay rates and frass related inputs (defined as the total leaf area removed minus the portion removed as greenfall). This study clearly demonstrates the ability of insect herbivores to alter nutrient cycling in tropical forest ecosystems and is the first study to demonstrate a direct link between herbivory and decomposition processes. These experiments provide clear evidence that insect herbivores can alter nutrient cycling and soil processes in forest systems. Such findings elucidate the need to more fully consider the effects of herbivores in both ecosystem models and management issues of tropical forest ecosystems. Title: The influence of herbivore generated inputs on nutrient cycling and soil processes in a lower montane tropical rain forest of Puerto Rico Author: Fonte, Steven J. The role of insect herbivores in the nutrient cycling dynamics of forest ecosystems remains poorly understood. Although past research in herbivory has focused primarily on the deleterious effects that insects can have on tree growth and mortality, the overall effects of herbivory are more complex. Herbivores have the potential to alter key ecosystem processes in a number of ways. One is by altering the flow of nutrients from the canopy to the forest floor. The studies presented here examine the effects that frass (insect excreta), greenfall (green leaf fragments) and herbivore modified throughfall, have on decomposition processes and soil nutrient dynamics. Both studies were carried out in a lower montane tropical rain forest near the El Verde Field Station, Luquillo Long-Term Ecological Research (LTER) site, Puerto Rico. The first study presented here tested the hypotheses that green leaves are of higher quality and decompose more rapidly than senesced leaves. Green and senesced leaves of four common native tree species (Dacryodes excelsa, Manilkara bidentata, Guarea guidonia and Cecropia schreberiana), were collected and analyzed for C, N, and complex C compounds. Litterbags containing green and senescent leaves of each species were placed in the field for up to 16 weeks in order to compare rates of litter decomposition. Green leaves contained significantly higher (p < 0.05) concentrations of N and lower lignin:N ratios than senescent leaves for all four species. Decomposition rates were significantly higher (p < 0.05) for green leaves compared to senescent leaves for all four species. These results demonstrate that insect herbivores may influence key ecosystem processes via the production of greenfall. The relevance of this study extends to green leaf deposition resulting from multiple sources, including high wind and rain events, as well as disturbance by larger canopy organisms. The second study tested a direct link between herbivory and soil processes. By altering levels of herbivory on a common understory plant (Piper glabrescens), using a prevalent folivore (Lamponius portoricensis), this study tested for effects of herbivory on nutrient inputs to the soil, as well as rates of litter decomposition. Enclosures were constructed around P. glabrescens individuals in the field and assigned to one of four treatments: herbivore exclusion, control, low herbivory and high herbivory. Total leaf area loss and greenfall production were measured for each plant using a sub-sample of randomly chosen leaves. Litterbags and ion exchange resin bags, placed under each plant, recorded rates of litter decomposition and the flow of NO3, NH4 and PO4 to the forest floor during this 76-day experiment. The treatments were effective in establishing a wide range of herbivory. Both the total leaf area removed and greenfall deposition demonstrated significant positive correlations (p <0.05) with NO3 transfer to the forest floor, but not with NH4 or PO4. Although decomposition rates showed no significant correlation with total leaf area losses or the greenfall component, a significant correlation was found between decay rates and frass related inputs (defined as the total leaf area removed minus the portion removed as greenfall). This study clearly demonstrates the ability of insect herbivores to alter nutrient cycling in tropical forest ecosystems and is the first study to demonstrate a direct link between herbivory and decomposition processes. These experiments provide clear evidence that insect herbivores can alter nutrient cycling and soil processes in forest systems. Such findings elucidate the need to more fully consider the effects of herbivores in both ecosystem models and management issues of tropical forest ecosystems. Close

• 16. [Article] Spatial heterogeneity, meta-analysis and spatial dependence : three essays on environmental valuation and spatial land management decisions

  This dissertation consists of three essays that collectively address the importance of accounting for spatial heterogeneity and spatial dependence of environmental assets and natural resources in policy ...

  Citation × Citation Citation Abstract Copy Title: Spatial heterogeneity, meta-analysis and spatial dependence : three essays on environmental valuation and spatial land management decisions Author: Bu, Meidan This dissertation consists of three essays that collectively address the importance of accounting for spatial heterogeneity and spatial dependence of environmental assets and natural resources in policy making. The first essay examines the value of different wetland ecosystem services using an expanded meta-dataset of valuation studies in North America. The purpose of this essay is to explore the sources of variation in wetland values from valuation methodology, ecosystem functions, and site-specific geographic, demographic and socio-economic characteristics. This essay used panel random effect models stratified "by study", "by state" and "by wetland site" to address the issues of correlation between wetland value estimates. Results indicated that wetland welfare measures reported by the same study and in the same wetland site are correlated. By comparing regression results and conclusions from this study with two internationally scoped meta-analysis studies, this essay found that the wetland valuation literature is not robust to regional characteristics, and wetland welfare estimates are sensitive to geographic extent. The second essay extends the first essay to investigate spatial spillover effects of wetland welfare estimates in North America. The primary purpose of the essay is to explore whether wetland values are correlated across space and what determines the correlation. The goal is accomplished by incorporating spatial econometric methods into the meta-analysis framework. The essay constructed three spatial weight matrices based on threshold distances, the ecological similarity and the economic similarity of wetland sites in the metadata. Results indicate that spatial proximity is an important predictor of wetland values regardless of wetland type and function. In part this is captured through shared contexts including resource availability and market characteristics. However, similar ecological and economic profiles are insufficient to capture shared values when transferring value estimates across spatial areas. Results from this study also raised questions on whether ecological functions and economic markets are sufficient for improving international transfers when studies are beyond geographic thresholds. The third essay incorporates spatial econometric models into a stochastic optimization framework to explore the consequences of ignoring the spatial linkage of management units in land management outcomes. The integrated framework combines an economic decision model, a spatial fire simulation model, a spotted owl population prediction model to maximize the expected post-fire and post-treatment NSO population under a budget constraint. Results from this essay inform us that ignoring spatial habitat connections leads to an underestimate of the fuel treatment disturbance and an over-estimate of the expected post-fire and post-treatment NSO population. However, the negative externality of habitat conversions depends on the degree of habitat connections. Additionally, the amount of total treatment area depends on the degree of habitat connections. The optimization outcome suggests less fuel treatment for a landscape with a higher degree of habitat connections. Moreover, the optimization outcome informs us that the spatial configuration of fuel treatment matters for the NSO population protection. Ignoring the spatial habitat connections leads to a fragmented treatment pattern and fails to protect the core NSO habitat from treatment disturbances. Title: Spatial heterogeneity, meta-analysis and spatial dependence : three essays on environmental valuation and spatial land management decisions Author: Bu, Meidan This dissertation consists of three essays that collectively address the importance of accounting for spatial heterogeneity and spatial dependence of environmental assets and natural resources in policy making. The first essay examines the value of different wetland ecosystem services using an expanded meta-dataset of valuation studies in North America. The purpose of this essay is to explore the sources of variation in wetland values from valuation methodology, ecosystem functions, and site-specific geographic, demographic and socio-economic characteristics. This essay used panel random effect models stratified "by study", "by state" and "by wetland site" to address the issues of correlation between wetland value estimates. Results indicated that wetland welfare measures reported by the same study and in the same wetland site are correlated. By comparing regression results and conclusions from this study with two internationally scoped meta-analysis studies, this essay found that the wetland valuation literature is not robust to regional characteristics, and wetland welfare estimates are sensitive to geographic extent. The second essay extends the first essay to investigate spatial spillover effects of wetland welfare estimates in North America. The primary purpose of the essay is to explore whether wetland values are correlated across space and what determines the correlation. The goal is accomplished by incorporating spatial econometric methods into the meta-analysis framework. The essay constructed three spatial weight matrices based on threshold distances, the ecological similarity and the economic similarity of wetland sites in the metadata. Results indicate that spatial proximity is an important predictor of wetland values regardless of wetland type and function. In part this is captured through shared contexts including resource availability and market characteristics. However, similar ecological and economic profiles are insufficient to capture shared values when transferring value estimates across spatial areas. Results from this study also raised questions on whether ecological functions and economic markets are sufficient for improving international transfers when studies are beyond geographic thresholds. The third essay incorporates spatial econometric models into a stochastic optimization framework to explore the consequences of ignoring the spatial linkage of management units in land management outcomes. The integrated framework combines an economic decision model, a spatial fire simulation model, a spotted owl population prediction model to maximize the expected post-fire and post-treatment NSO population under a budget constraint. Results from this essay inform us that ignoring spatial habitat connections leads to an underestimate of the fuel treatment disturbance and an over-estimate of the expected post-fire and post-treatment NSO population. However, the negative externality of habitat conversions depends on the degree of habitat connections. Additionally, the amount of total treatment area depends on the degree of habitat connections. The optimization outcome suggests less fuel treatment for a landscape with a higher degree of habitat connections. Moreover, the optimization outcome informs us that the spatial configuration of fuel treatment matters for the NSO population protection. Ignoring the spatial habitat connections leads to a fragmented treatment pattern and fails to protect the core NSO habitat from treatment disturbances. Close

• 17. [Article] Effects of spatially dispersed green-tree retention on ectomycorrhiza diversity

  The Demonstration for Ecosystem Management Options (DEMO) study originated out of the changing management priorities associated with federal forest lands in the Pacific Northwest which included an objective ...

  Citation × Citation Citation Abstract Copy Title: Effects of spatially dispersed green-tree retention on ectomycorrhiza diversity Author: Kolaczkowski, Oralia The Demonstration for Ecosystem Management Options (DEMO) study originated out of the changing management priorities associated with federal forest lands in the Pacific Northwest which included an objective to maintain mature and old-growth forest characteristics in managed stands. The DEMO project examines the effects that different levels and patterns of green tree retention have on various aspects of biodiversity including the diversity of ectomycorrhizal fungi (EMF). Ectomycorrhizal fungi play an important functional role in forest ecosystems. Ectomycorrhizal fungi are essential for nutrient uptake by the host tree, they have been shown to play a critical role in forest regeneration success, and EMF provide an important food source (in the form of sporocarps) for many small mammals. As part of the DEMO study, this thesis documents EMF diversity in the control unit (100% retention) and the spatially dispersed 40°/a basal area retention treatment (40%D). The measures of diversity studied included EMF constancy, abundance, and species richness. Constancy and abundance measures were analyzed only for the common ectomycorrhizae (EM) types. Morphological techniques for identification of the EMF were employed together with molecular techniques to achieve the finest level of identification possible. Characters used to assess morphology include mantle structures, emanating hyphae, rhizomorphs, root morphology, chemical reactions, and mantle color. Molecular techniques were used for identification purposes and for checking EM morphotype groups. Molecular techniques used included DNA extraction of the internal transcribed spacer region, polymerase chain reaction amplification, restriction fragment length polymorphism, and DNA sequencing. Significant responses to the 40%D treatment were determined by testing both pre and post EMF diversity within the treatment and by comparing changes in diversity between the control and the 40%D treatment. Overall, within the 40%D treatment, the majority of the common EMF species did not decrease significantly. A moderately significant difference was detected between the pre-treatment and post-treatment mean number of EM types per soil core (measure of species richness). This decrease in richness of about 50% in the post-treatment2 samples seems to indicate a delayed response to the treatment since the post-treatment1 samples were not different from the pre-treatment conditions. Since no dominant types were lost, the decline in richness occurred in the less common EM types. This research demonstrates that the 40%D treatment can maintain a relatively high legacy of EMF. However, there is a loss of some rare EM types and a reduction in abundance and constancy in some of the more common EM types. These results lend support for the consideration of40% dispersed green-tree retention as a silvicultural option when management goals include the maintenance of EMF diversity. Timber harvest via implementation of ecosystem-based forest management practices will require the continuing study of complex below-ground systems for the development of potential silvicultural treatments during further iterations of adaptive management. Title: Effects of spatially dispersed green-tree retention on ectomycorrhiza diversity Author: Kolaczkowski, Oralia The Demonstration for Ecosystem Management Options (DEMO) study originated out of the changing management priorities associated with federal forest lands in the Pacific Northwest which included an objective to maintain mature and old-growth forest characteristics in managed stands. The DEMO project examines the effects that different levels and patterns of green tree retention have on various aspects of biodiversity including the diversity of ectomycorrhizal fungi (EMF). Ectomycorrhizal fungi play an important functional role in forest ecosystems. Ectomycorrhizal fungi are essential for nutrient uptake by the host tree, they have been shown to play a critical role in forest regeneration success, and EMF provide an important food source (in the form of sporocarps) for many small mammals. As part of the DEMO study, this thesis documents EMF diversity in the control unit (100% retention) and the spatially dispersed 40°/a basal area retention treatment (40%D). The measures of diversity studied included EMF constancy, abundance, and species richness. Constancy and abundance measures were analyzed only for the common ectomycorrhizae (EM) types. Morphological techniques for identification of the EMF were employed together with molecular techniques to achieve the finest level of identification possible. Characters used to assess morphology include mantle structures, emanating hyphae, rhizomorphs, root morphology, chemical reactions, and mantle color. Molecular techniques were used for identification purposes and for checking EM morphotype groups. Molecular techniques used included DNA extraction of the internal transcribed spacer region, polymerase chain reaction amplification, restriction fragment length polymorphism, and DNA sequencing. Significant responses to the 40%D treatment were determined by testing both pre and post EMF diversity within the treatment and by comparing changes in diversity between the control and the 40%D treatment. Overall, within the 40%D treatment, the majority of the common EMF species did not decrease significantly. A moderately significant difference was detected between the pre-treatment and post-treatment mean number of EM types per soil core (measure of species richness). This decrease in richness of about 50% in the post-treatment2 samples seems to indicate a delayed response to the treatment since the post-treatment1 samples were not different from the pre-treatment conditions. Since no dominant types were lost, the decline in richness occurred in the less common EM types. This research demonstrates that the 40%D treatment can maintain a relatively high legacy of EMF. However, there is a loss of some rare EM types and a reduction in abundance and constancy in some of the more common EM types. These results lend support for the consideration of40% dispersed green-tree retention as a silvicultural option when management goals include the maintenance of EMF diversity. Timber harvest via implementation of ecosystem-based forest management practices will require the continuing study of complex below-ground systems for the development of potential silvicultural treatments during further iterations of adaptive management. Close

• 18. [Article] Landscape features affecting genetic diversity and structure in East African ungulate species

  Habitat loss and fragmentation is a crisis affecting wildlife worldwide. In Tanzania, East Africa, a dramatic and recent (<80 years) expansion in human settlement and agriculture threatens to reduce gene ...

  Citation × Citation Citation Abstract Copy Title: Landscape features affecting genetic diversity and structure in East African ungulate species Author: Crowhurst, Rachel Selena Habitat loss and fragmentation is a crisis affecting wildlife worldwide. In Tanzania, East Africa, a dramatic and recent (<80 years) expansion in human settlement and agriculture threatens to reduce gene flow among protected areas for many species of large mammals. Wildlife linkages can mitigate population isolation, but linkage designs lacking empirical justification may be controversial and ineffective. Connectivity conservation requires an understanding of how biogeographic factors shaped gene flow prior to habitat loss or fragmentation, however the history of interaction among populations is rarely known. The goal of my study was to provide context for connectivity conservation in central and southern Tanzania by identifying landscape features that have shaped gene flow for three ungulate species with different dispersal capabilities. I investigated historical patterns of connectivity for Maasai giraffe (Giraffa camelopardalis tippelskirchi), impala (Aepyceros melampus), and eland (Tragelaphus oryx) by estimating genetic structure among four to eight protected areas per species. Genetic structure changes very slowly among large populations and thus is likely to reflect historical processes instead of recent anthropogenic influences. I collected noninvasive DNA samples and generated microsatellite genotypes at 8 to 15 loci per species, then estimated genetic diversity metrics (allelic richness, AR, and expected heterozygosity, H[subscript E]) for each population (defined by reserve). I also calculated genetic distance (F[subscript ST] and Nei's unbiased genetic distance, D[subscript hat]) and an estimate of gene flow (Nm) between all population pairs for each species. To elucidate the possible causes of genetic structure between these populations, I tested for isolation by distance and isolation by resistance based on a suite of biogeographic factors hypothesized to affect gene flow. To do this, I created GIS-based resistance surfaces that assigned different costs of movement to landscape features. I created one or more resistance surfaces for each hypothesis of landscape effect. I used circuit theory to estimate the cumulative resistance between each pair of reserves for each weighting scheme, and then performed Mantel tests to calculate the correlation between these resistances and the observed population pairwise genetic distances (D[subscript hat]). I chose the optimal resistance model for each species as the model that was most highly correlated with observed genetic patterns. To verify that the correlation of resistance models with genetic distance was not an artefact of geographic distance, I performed partial Mantel tests to calculate correlation while controlling for the effect of geographic distance. Finally, I compared historical gene flow patterns to the distribution of contemporary human activity to predict areas that are at risk of a loss of connectivity. Indices of genetic diversity were moderate for all three species and comparable to previously reported values for other savannah ungulates. Diversity (both H[subscript E] and A[subscript R]) was highest in eland and lowest in giraffe for these populations, and was not consistently correlated with reserve size as has been reported for other species in East Africa. Although patterns in genetic distance were broadly similar across all three species there were also striking differences in connectivity, highlighting the importance of cross-species comparisons in connectivity conservation. At this scale, resistance models based on slope strongly predicted population structure for all three species; distance to water was also highly correlated with genetic distance in eland. For all three species, the greatest genetic distances occurred between populations separated by the Eastern Arc Mountains, suggesting that the topography of this area has long acted as a barrier to gene flow, but this effect is present in varying degrees for each species. I observed high levels of historical gene flow between centrally located populations (Ruaha National Park and Rungwa Game Reserve) and those in the southwest (Katavi National Park and Rukwa Game Reserve). Although human settlement in this area has been low relative to other areas, the connection between the Katavi/Rukwa and Ruaha ecosystems may be threatened by increased human activity and warrants conservation. High levels of historical gene flow were also seen between reserves in the northeast (Tarangire National Park, Swagaswaga Game Reserve) and the central and southwest populations. These connections appear highly threatened due to current land use practices, and may have already suffered a loss of gene flow. Field surveys in the lands surrounding the northeastern reserves are needed to quantify current levels of connectivity and determine whether corridors could be established to maintain or restore gene flow with other reserves. Title: Landscape features affecting genetic diversity and structure in East African ungulate species Author: Crowhurst, Rachel Selena Habitat loss and fragmentation is a crisis affecting wildlife worldwide. In Tanzania, East Africa, a dramatic and recent (<80 years) expansion in human settlement and agriculture threatens to reduce gene flow among protected areas for many species of large mammals. Wildlife linkages can mitigate population isolation, but linkage designs lacking empirical justification may be controversial and ineffective. Connectivity conservation requires an understanding of how biogeographic factors shaped gene flow prior to habitat loss or fragmentation, however the history of interaction among populations is rarely known. The goal of my study was to provide context for connectivity conservation in central and southern Tanzania by identifying landscape features that have shaped gene flow for three ungulate species with different dispersal capabilities. I investigated historical patterns of connectivity for Maasai giraffe (Giraffa camelopardalis tippelskirchi), impala (Aepyceros melampus), and eland (Tragelaphus oryx) by estimating genetic structure among four to eight protected areas per species. Genetic structure changes very slowly among large populations and thus is likely to reflect historical processes instead of recent anthropogenic influences. I collected noninvasive DNA samples and generated microsatellite genotypes at 8 to 15 loci per species, then estimated genetic diversity metrics (allelic richness, AR, and expected heterozygosity, H[subscript E]) for each population (defined by reserve). I also calculated genetic distance (F[subscript ST] and Nei's unbiased genetic distance, D[subscript hat]) and an estimate of gene flow (Nm) between all population pairs for each species. To elucidate the possible causes of genetic structure between these populations, I tested for isolation by distance and isolation by resistance based on a suite of biogeographic factors hypothesized to affect gene flow. To do this, I created GIS-based resistance surfaces that assigned different costs of movement to landscape features. I created one or more resistance surfaces for each hypothesis of landscape effect. I used circuit theory to estimate the cumulative resistance between each pair of reserves for each weighting scheme, and then performed Mantel tests to calculate the correlation between these resistances and the observed population pairwise genetic distances (D[subscript hat]). I chose the optimal resistance model for each species as the model that was most highly correlated with observed genetic patterns. To verify that the correlation of resistance models with genetic distance was not an artefact of geographic distance, I performed partial Mantel tests to calculate correlation while controlling for the effect of geographic distance. Finally, I compared historical gene flow patterns to the distribution of contemporary human activity to predict areas that are at risk of a loss of connectivity. Indices of genetic diversity were moderate for all three species and comparable to previously reported values for other savannah ungulates. Diversity (both H[subscript E] and A[subscript R]) was highest in eland and lowest in giraffe for these populations, and was not consistently correlated with reserve size as has been reported for other species in East Africa. Although patterns in genetic distance were broadly similar across all three species there were also striking differences in connectivity, highlighting the importance of cross-species comparisons in connectivity conservation. At this scale, resistance models based on slope strongly predicted population structure for all three species; distance to water was also highly correlated with genetic distance in eland. For all three species, the greatest genetic distances occurred between populations separated by the Eastern Arc Mountains, suggesting that the topography of this area has long acted as a barrier to gene flow, but this effect is present in varying degrees for each species. I observed high levels of historical gene flow between centrally located populations (Ruaha National Park and Rungwa Game Reserve) and those in the southwest (Katavi National Park and Rukwa Game Reserve). Although human settlement in this area has been low relative to other areas, the connection between the Katavi/Rukwa and Ruaha ecosystems may be threatened by increased human activity and warrants conservation. High levels of historical gene flow were also seen between reserves in the northeast (Tarangire National Park, Swagaswaga Game Reserve) and the central and southwest populations. These connections appear highly threatened due to current land use practices, and may have already suffered a loss of gene flow. Field surveys in the lands surrounding the northeastern reserves are needed to quantify current levels of connectivity and determine whether corridors could be established to maintain or restore gene flow with other reserves. Close

• 19. [Article] Broad-scale patterns of invertebrate richness and community composition in temporary rivers: effects of flow intermittence

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by John Wiley ...

  Citation × Citation Citation Abstract Copy Title: Broad-scale patterns of invertebrate richness and community composition in temporary rivers: effects of flow intermittence Author: Larned, S. T., Bogan, M. T., Wood, P. J., Santos, A. N., Meyer, E. I., Datry, T., Fritz, K. M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by John Wiley & Sons, Ltd. and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-0587. Title: Broad-scale patterns of invertebrate richness and community composition in temporary rivers: effects of flow intermittence Author: Larned, S. T., Bogan, M. T., Wood, P. J., Santos, A. N., Meyer, E. I., Datry, T., Fritz, K. M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by John Wiley & Sons, Ltd. and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-0587. Close

• 20. [Article] Intercomparison of MODIS albedo retrievals and in situ measurements across the global FLUXNET network

  This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/remote-sensing-of-environment/#description. To the best of our ...

  Citation × Citation Citation Abstract Copy Title: Intercomparison of MODIS albedo retrievals and in situ measurements across the global FLUXNET network Author: Yang, Xiaoyuan, Vannan, Suresh K. Santhana, Law, Beverly E., Richardson, Andrew D., Roman, Miguel O., Moors, Eddy, Matteucci, Giorgio, Migliavacca, Mirco, Seufert, Guenther, Ciais, Philippe, Cook, Robert B., Schaaf, Crystal B., Pan, Jerry Yun, Cescatti, Alessandro, Marcolla, Barbara This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/remote-sensing-of-environment/#description. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Title: Intercomparison of MODIS albedo retrievals and in situ measurements across the global FLUXNET network Author: Yang, Xiaoyuan, Vannan, Suresh K. Santhana, Law, Beverly E., Richardson, Andrew D., Roman, Miguel O., Moors, Eddy, Matteucci, Giorgio, Migliavacca, Mirco, Seufert, Guenther, Ciais, Philippe, Cook, Robert B., Schaaf, Crystal B., Pan, Jerry Yun, Cescatti, Alessandro, Marcolla, Barbara This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/remote-sensing-of-environment/#description. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. Close