Michael A. Cairns

Root biomass allocation in the world's upland forests

Abstract Because the worlds forests play a major role in regulating nutrient and carbon cycles, there is much interest in estimating their biomass. Estimates of aboveground biomass based on well-established methods are relatively abundant; estimates of root biomass based on standard methods are much less common. The goal of this work was to determine if a reliable method to estimate root biomass density for forests could be developed based on existing data from the literature. The forestry literature containing root biomass measurements was reviewed and summarized and relationships between both root biomass density (Mg ha−1) and root:shoot ratios (R/S) as dependent variables and various edaphic and climatic independent variables, singly and in combination, were statistically tested. None of the tested independent variables of aboveground biomass density, latitude, temperature, precipitation, temperature:precipitation ratios, tree type, soil texture, and age had important explanatory value for R/S. However, linear regression analysis showed that aboveground biomass density, age, and latitudinal category were the most important predictors of root biomass density, and together explained 84% of the variation. A comparison of root biomass density estimates based on our equations with those based on use of generalized R/S ratios for forests in the United States indicated that our method tended to produce estimates that were about 20% higher.

Juvenile Coho Salmon Growth and Survival across Stream Network Seasonal Habitats

Abstract Understanding watershed-scale variation in juvenile salmonid survival and growth can provide insights into factors influencing demographics and can help target restoration and mitigation efforts for imperiled fish populations. We assessed growth, movement, and apparent overwinter survival of individually tagged juvenile coho salmon Oncorhynchus kisutch in a coastal Oregon watershed from June 2002 to June 2003 and related growth and survival parameters to stream characteristics. Fall body size of juvenile coho salmon was a good predictor of smolt size and survival, but smolt size was also influenced by overwintering location. This was due to strong spatial patterns in winter growth rates associated with residency and movement into a small intermittent tributary. Though nearly dry in midsummer, this stream supported high densities of spawning coho salmon in the fall, and juveniles rearing there exhibited relatively high growth rates and emigrated as larger smolts. Improved winter growth and surviva...

TROPICAL MEXICO'S RECENT LAND‐USE CHANGE: A REGION'S CONTRIBUTION TO THE GLOBAL CARBON CYCLE

We applied modeled biomass density estimates to changes in land use/land cover (LU/LC) statistics for the intensively impacted and highly fragmented landscape of tropical Mexico to estimate the flux of carbon (C) between terrestrial ecosystems and the atmosphere between 1977 and 1992. Biomass densities were assigned to hybrid LU/LC classes on vegetation maps produced by Mexican governmental organizations and, by dif- ferencing areas and biomass C pools, net C flux was calculated in the eight-state tropical region of southeast Mexico. These states, representing tropical Mexico, experienced a mean annual deforestation rate of nearly 559 000 ha/yr, or 1.9%, between 1977 and 1992. The total area of closed forests decreased by 26%, open/fragmented forests decreased by 31%, and agroecosystem areas increased by 64%. Total mean biomass densities ranged from a high of 265 Mg/ha in the Veracruz state tall/medium tropical evergreen forest class to a low of 12 Mg/ha in the cultivated land class (several states). We estimate that a total of 280 Tg C were released from the terrestrial biosphere during the 15-yr period covered by our study, equal to nearly 20% of the regions 1977 biomass C pool. The study region, while comprising just 24% of Mexicos surface area, contributed 36% of the net national C emissions from LU/LC change.

Carbon Flux and Patterns of Land-Use/ Land-Cover Change in the Selva Lacandona, Mexico

Abstract Based on land-use/land-cover (LU/LC) maps for the 1970s and satellite imagery for the 1990s we estimate LU/LC change and associated C fluxes in 3 subregions of the Selva Lacandona, Chiapas, Mexico. The total area of closed forest was reduced by 31%, whereas secondary forests expanded more than ninefold, secondary shrubs by almost sixfold, and cultivated land and pasture areas expanded 21% and 92%, respectively. However, the LU/LC change was not uniformly distributed over the entire study area. Total mean C densities ranged from 452 Mg C ha−1 for closed mature forests to a low of 120 Mg C ha−1 for pasture. The heavily converted areas lost an estimated 24% of their total 1976 C pools, whereas the low impacted region lost only 3%.

Coho salmon dependence on intermittent streams

In February 2006, the US Supreme Court heard cases that may affect whether intermittent streams are jurisdictional waters under the Clean Water Act. In June 2006, however, the cases were remanded to the circuit court, leaving the status of intermittent streams uncertain once again. The presence of commercial species, such as coho salmon (Oncorhynchus kisutch), can be an important consideration when determining jurisdiction. These salmon spawn in the upper portions of Oregon coastal stream networks, where intermittent streams are common. In our study of a coastal Oregon watershed, we found that intermittent streams were an important source of coho salmon smolts. Residual pools in intermittent streams provided a means by which juvenile coho could survive during dry periods; smolts that overwintered in intermittent streams were larger than those from perennial streams. Movement of juvenile coho into intermittent tributaries from the mainstem was another way in which the fish exploited the habitat and illustrates the importance of maintaining accessibility for entire stream networks. Loss of intermittent stream habitat would have a negative effect on coho salmon populations in coastal drainages, including downstream navigable waters.

Ecological and water quality consequences of nutrient addition for salmon restoration in the Pacific Northwest

Salmon runs have declined over the past two centuries in the Pacific Northwest region of North America. Reduced inputs of salmon-derived organic matter and nutrients (SDN) may limit freshwater production and thus establish a negative feedback loop affecting future generations of fish. Restoration efforts use the rationale of declining SDN to justify artificial nutrient additions, with the goal of reversing salmon decline. The forms of nutrient addition include introducing salmon carcasses, carcass analogs (processed fish cakes), or inorganic fertilizers. While evidence suggests that fish and wildlife may benefit from increases in food availability as a result of carcass additions, stream ecosystems vary in their ability to use nutrients to benefit salmon. Moreover, the practice may introduce excess nutrients, disease, and toxic substances to streams that may already exceed proposed water quality standards. Restoration efforts involving nutrient addition must balance the potential benefits of increased foo...

Influence of Summer Stream Temperatures on Black Spot Infestation of Juvenile Coho Salmon in the Oregon Coast Range

Abstract High summer water temperatures can adversely affect stream salmonids in numerous ways. The direct effects of temperature associated with increased metabolic demand can be exacerbated by other factors, including decreased resistance to disease and increased susceptibility to parasites. We quantified the occurrence of black spot infestation caused by a neascus-type trematode (family Diplostomidae) of juvenile salmonids in Oregons West Fork Smith River stream network during summer 2002 through fall 2003. The highest 7-d average of the daily maximum (ADM) temperatures was positively correlated with infestation rates in both years. We summarized the frequency and infestation severity of juvenile coho salmon Oncorhynchus kisutch by location within the network and summarized temperatures for 19 study reaches. Summer ADMs ranged from approximately 24°C near the watershed mouth to approximately 17°C in the upper reaches, while tributary ADMs ranged from approximately 16–18°C in the lower reaches to 12–17...

Use of Fish Ventilation Frequency to Estimate Chronically Safe Toxicant Concentrations

Abstract A 96-hour toxicity test with fish ventilation frequency as the response variable was developed to estimate safe zinc concentrations for steelhead Salmo gairdneri. Two Oregon steelhead strains were exposed to zinc at different water temperatures and total hardnesses (7, 12, and 17 C; 25 and 125 mg/liter as CaCO3). Ventilation frequencies enumerated from bioelectric potentials generated by buccal and opercular openings and closings showed significant increases at the highest test concentration in five of 10 tests. At 12 C and 25 mg/liter hardness, responses were detected at a zinc concentration of 144 μg/liter; the “safe” concentration determined in a chronic exposure of embryos and juveniles was between 444 and 819 μg zinc/liter. This indicates that ventilation-frequency tests are at least as sensitive as long-term toxicity tests and may be used to screen chemicals for potential harmful effects on fish.

Carbon sequestration, biological diversity, and sustainable development: Integrated forest management

Tropical deforestation provides a significant contribution to anthropogenic increases in atmospheric CO2 concentration that may lead to global warming. Forestation and other forest management options to sequester CO2 in the tropical latitudes may fail unless they address local economic, social, environmental, and political needs of people in the developing world. Forest management is discussed in terms of three objectives: carbon sequestration, sustainable development, and biodiversity conservation. An integrated forest management strategy of land-use planning is proposed to achieve these objectives and is centered around: preservation of primary forest, intensified use of nontimber resources, agroforestry, and selective use of plantation forestry.

Biodiversity and Management of Natural Resources: The Issues

Abstract The earths genetic, species, community, and landscape-level diversity is declining at an unprecedented rate because of habitat alteration. The decline of biodiversity in the aquatic environment is now recognized as a serious concern by biologists. Development and use of natural resources commonly have been practiced in an unsustainable manner. Political institutions are challenged to reconcile both the competing private and public goals and the diverse set of expectations of our natural resources, including aquatic systems. This paper defines biodiversity, identifies many of its values, and reviews causes of its decline. The major ecological, ethical, economic, social, and political issues involved in natural resource management are summarized, as are some of the expected responses of scientists and natural resource managers to the issues.