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At least 1,009 records · Page 56Linked to original sources
USGS2011

Effects of a low severity prescribed fire on water-soluble elements in ash from a cork oak (Quercus suber) forest located in the northeast of the Iberian Peninsula

Wildfire is the major disturbance in Mediterranean forests. Prescribed fire can be an alternative to reduce the amount of fuel and hence decrease the wildfire risk. However the effects of prescribed fire must be studied, especially on ash properties, because ash is an important nutrient source for ecosystem recovery. The aim of this study is to determine the effects of a low severity prescribed fire on water-soluble elements in ash including pH, electrical conductivity (EC), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), aluminum (Al), manganese (Mn), iron (Fe), zinc (Zn), silica (SiO 2 ) and total sulphur (TS). A prescribed fire was conducted in a cork oak ( Quercus suber ) (Q.S) forest located in the northeast part of the Iberian Peninsula. Samples were collected from a flat plot of 40×70 m mainly composed of Q.S and Quercus robur (Q.R) trees. In order to understand the effects of the prescribed fire on the soluble elements in ash, we conducted our data analysis on three data groups: all samples, only Q.S samples and only Q.R samples. All three sample groups exhibited a significant increase in pH, EC ( p <0.001), water-soluble Ca, Mg, Na, SiO 2 and TS and a decrease in water-soluble Mn, Fe and Zn. Differences were identified between oak species for water-soluble K, Al and Fe. In Q.S samples we registered a significant increase in the first two elements p <0.001 and p <0.01, respectively, and a non-significant impact in the third, at p <0.05. In Q.R data we identified a non-significant impact on water-soluble K and Al and a significant decrease in water-soluble Fe ( p <0.05). These differences are probably due to vegetation characteristics and burn severity. The fire induced a higher variability in the ash soluble elements, especially in Q.S samples, that at some points burned with higher severity. The increase of pH, EC, Ca, Mg, Na and K will improve soil fertility, mainly in the study area where soils are acidic. The application of this low severity prescribed fire will improve soil nutrient status without causing soil degradation and thus is considered to be a good management strategy.

Environmental Research↗
USGS2018

Conservation threats and priorities for raptors across Asia

With long coastlines and some of the world’s most important rivers, mountain ranges, high-altitude plateaus, and islands, Asia is the largest and most populous continent in the world (Lyde 1904; Spencer 1954; Population Reference Bureau 2016). Asia supports all major terrestrial ecosystems and all major climatic types (Galloway et al. 1998; Braimoh and Huang 2015). These include barren ice fields and taigas in North Asia; boreal forests and cold deserts in West, Central, and East Asia; temperate and tropical forests (wet and dry) in East and Southeast Asia; and grasslands in Central and South Asia (Udvardy 1975; Braimoh and Huang 2015). Together, the ecoregions of Asia foster some of the greatest biodiversity on Earth, including six (24%) of 25 global biodiversity hotspots (Myers et al. 2000).

Book chapter↗
USGS2012

The National Land Cover Database

The National Land Cover Database (NLCD) serves as the definitive Landsat-based, 30-meter resolution, land cover database for the Nation. NLCD provides spatial reference and descriptive data for characteristics of the land surface such as thematic class (for example, urban, agriculture, and forest), percent impervious surface, and percent tree canopy cover. NLCD supports a wide variety of Federal, State, local, and nongovernmental applications that seek to assess ecosystem status and health, understand the spatial patterns of biodiversity, predict effects of climate change, and develop land management policy. NLCD products are created by the Multi-Resolution Land Characteristics (MRLC) Consortium, a partnership of Federal agencies led by the U.S. Geological Survey. All NLCD data products are available for download at no charge to the public from the MRLC Web site: http://www.mrlc.gov.

Fact Sheet↗
USGS2025

Workshop: Nature-based solutions to ecological and economic problems caused by extreme precipitation events in the Upper Mississippi River Basin

Future climate conditions in the Upper Mississippi River Basin are projected to include many more extreme precipitation events. These intense periods of rain can lead to flooding of the Mississippi River itself, as well the small streams and rivers that feed it. This flooding presents a challenge for local communities, farmers, small businesses, river users, and the ecosystems and wildlife in the area. To reduce the damage done by these extreme rainfall events, ‘natural solutions’ are often helpful. This might include preserving forests and grasslands to absorb rainwater before it arrives at streams or restoring wetlands to slow and clean runoff water. For river and natural resource managers to adapt to future climate by using these natural solutions, however, they require accurate information about the projected increase in extreme rainfall events and the effectiveness and costs of a variety of solutions. To provide this information, researchers must understand the decisions that managers are making and the challenges they face. In this project, researchers will host a workshop to facilitate knowledge sharing between natural resource managers, climate modelers, and scientists studying natural solutions. Participants will discuss climate projections related to extreme precipitation events in the region, as well as the management implications and decision-making challenges associated with these events. These conversations will cultivate collaborative relationships between managers and researchers to address critical knowledge gaps and improve future management efforts in the Upper Mississippi River Basin.

Upper Mississippi River basin↗
USGS2020

Understanding effects of small dams on benthic metabolism and primary production in temperate forested streams

Dams can alter the chemical and physical conditions of downstream environments by increasing stream temperatures, altering nutrient limitation, reducing flow variability, and reducing fine sediment deposition. However, little is known about how fundamental stream ecosystem processes like productivity and respiration respond to dams. Nutrient diffusing substrates were installed in three dam streams and three control streams to evaluate the effect of dams on benthic gross primary productivity (GPP), respiration (R), and chlorophyll α production. Dam streams were an average of 5.6 °C warmer than control streams but GPP, R and chlorophyll α were not different between control and dam streams. Phosphorus enrichment increased heterotrophic R relative to controls (~1.8×) but not autotrophic GPP, R or chlorophyll α. Stream nutrient concentrations and nutrient limitation of heterotrophic R were similar in dam and control streams, suggesting that the dams had limited effects on nutrient transport downstream. Autotrophic GPP, R and chlorophyll α were limited by light and varied within and across streams, potentially masking our ability to detect differences caused solely by dams. Dams may alter stream ecosystem function but consideration of other factors associated with and independent of dams is critical for predicting ecosystem responses to dams.

Fundamental and Applied Limnology↗
USGS2003

Flows for floodplain forests: a successful riparian restoration

Throughout the 20th century, the Truckee River that flows from Lake Tahoe into the Nevada desert was progressively dammed and dewatered, which led to the collapse of its aquatic and riparian ecosystems. The federal designation of the endemic cui-ui sucker ( Chasmistes cujus ) as endangered prompted a restoration program in the 1980s aimed at increasing spring flows to permit fish spawning. These flows did promote cui-ui reproduction, as well as an unanticipated benefit, the extensive seedling recruitment of Fremont cottonwood ( Populus fremontii ) and sandbar willow ( Salix exigua ). Recruitment was scattered in 1983 but extensive in 1987, when the hydrograph satisfied the riparian recruitment box model that had been developed for other rivers. That model was subsequently applied to develop flow prescriptions that were implemented from 1995 through 2000 and enabled further seedling establishment. The woodland recovery produced broad ecosystem benefits, as evidenced by the return by 1998 of 10 of 19 riparian bird species whose populations had been locally extirpated or had declined severely between 1868 and 1980. The dramatic partial recovery along this severely degraded desert river offers promise that the use of instream flow regulation can promote ecosystem restoration along other dammed rivers worldwide.

California, Nevada↗
USGS2013

Restoring the Great Lakes: DOI stories of success and partnership in implementing the Great Lakes Restoration Initiative

The Great Lakes are a monumentally unique national treasure containing nearly ninety-five percent of the United States' fresh surface water. Formed by receding glaciers, the Great Lakes support a thriving, resilient ecosystem rich with fish, wildlife, and abundant natural resources. The Great Lakes also support an array of commercial uses, including shipping, and provide a source of recreation, drinking water, and other critical services that drive the economy of the region and the Nation. Regrettably, activities such as clear cutting of mature forests, over-harvesting of fish populations, industrial pollution, invasive species, and agricultural runoffs have degraded these treasured lakes over the decades creating long-term impacts to the surrounding watershed. Fortunately, the people who live, work, and recreate in the region recognize the critical importance of a healthy Great Lakes ecosystem, and have come together to support comprehensive restoration. To stimulate and promote the goal of a healthy Great Lakes region, President Obama and Congress created the Great Lakes Restoration Initiative (GLRI) in 2009. This program provides the seed money to clean up legacy pollution, restore habitats, protect wildlife, combat invasive species, and address agricultural runoff in the Great Lakes watershed. At the same time GLRI promotes public outreach, education, accountability, and partnerships.

The Great Lakes↗
USGS2007

Global impacts of conversions from natural to agricultural ecosystems on water resources: Quantity versus quality

Past land use changes have greatly impacted global water resources, with often opposing effects on water quantity and quality. Increases in rain‐fed cropland (460%) and pastureland (560%) during the past 300 years from forest and grasslands decreased evapotranspiration and increased recharge (two orders of magnitude) and streamflow (one order of magnitude). However, increased water quantity degraded water quality by mobilization of salts, salinization caused by shallow water tables, and fertilizer leaching into underlying aquifers that discharge to streams. Since the 1950s, irrigated agriculture has expanded globally by 174%, accounting for ∼90% of global freshwater consumption. Irrigation based on surface water reduced streamflow and raised water tables resulting in waterlogging in many areas (China, India, and United States). Marked increases in groundwater‐fed irrigation in the last few decades in these areas has lowered water tables (≤1 m/yr) and reduced streamflow. Degradation of water quality in irrigated areas has resulted from processes similar to those in rain‐fed agriculture: salt mobilization, salinization in waterlogged areas, and fertilizer leaching. Strategies for remediating water resource problems related to agriculture often have opposing effects on water quantity and quality. Long time lags (decades to centuries) between land use changes and system response (e.g., recharge, streamflow, and water quality), particularly in semiarid regions, mean that the full impact of land use changes has not been realized in many areas and remediation to reverse impacts will also take a long time. Future land use changes should consider potential impacts on water resources, particularly trade‐offs between water, salt, and nutrient balances, to develop sustainable water resources to meet human and ecosystem needs.

Water Resources Research↗
USGS2010

Social values for ecosystem services (SolVES): A GIS application for assessing, mapping, and quantifying the social values of ecosystem services-Documentation and user manual, version 1.0

In response to the need for incorporating quantified and spatially explicit measures of social values into ecosystem services assessments, the Rocky Mountain Geographic Science Center, in collaboration with Colorado State University, has developed a geographic information system application, Social Values for Ecosystem Services (SolVES). SolVES can be used to assess, map, and quantify the perceived social values of ecosystem services. SolVES derives a quantitative social values metric, the Value Index, from a combination of spatial and nonspatial responses to public attitude and preference surveys. SolVES also generates landscape metrics, such as average elevation and distance to water, calculated from spatial data layers describing the underlying physical environment. Using kernel density calculations and zonal statistics, SolVES derives and maps the 10-point Value Index and reports landscape metrics associated with each index value for social value types such as aesthetics, biodiversity, and recreation. This can be repeated for various survey subgroups as distinguished by their attitudes and preferences regarding public uses of the forests such as motorized recreation and logging for fuels reduction. The Value Index provides a basis of comparison within and among survey subgroups to consider the effect of social contexts on the valuation of ecosystem services. SolVES includes regression coefficients linking the predicted value (the Value Index) to landscape metrics. These coefficients are used to generate predicted social value maps using value transfer techniques for areas where primary survey data are not available. SolVES was developed, and will continue to be enhanced through future versions, as a public domain tool to enable decision makers and researchers to map the social values of ecosystem services and to facilitate discussions among diverse stakeholders regarding tradeoffs between different ecosystem services in a variety of physical and social contexts.

Open-File Report↗
USGS2025

Linking fire, food webs, and fish in stream ecosystems

As wildfire regimes shift, resource managers are concerned about potential threats to aquatic ecosystems and the species they support, especially fishes. However, predicting fish responses can be challenging because wildfires affect aquatic ecosystems via multiple pathways. Application of whole-ecosystem approaches, such as food web modeling, can act as heuristic tools that offer valuable insights that account for these different mechanisms. We applied a dynamic food web simulation model that mechanistically linked stream trophic dynamics to the myriad effects that wildfires can have on aquatic and riparian ecosystems at a local stream reach-scale. We simulated how wildfires of different severity may influence short- (months to years) and long-term (years to decades) periphyton, aquatic invertebrate, and fish biomass dynamics in forested headwater streams of the western Pacific Northwest (USA). In many cases, wildfire increased modeled periphyton, invertebrate, and fish biomass over both short- and long-time periods. However, modeled responses varied extensively in their direction (that is, positive or negative), magnitude, and duration depending on fire severity, time since fire, and trophic level. The shapes of these response trajectories were especially sensitive to predicted wildfire effects on water temperature, canopy cover, riparian shading, and instream turbidity. Model simulations suggest a single fire could result in a wide range of aquatic ecosystem responses, especially in watersheds with mixed burn severity. Our analysis highlights the utility of whole-ecosystem approaches, like food web modeling, as heuristic tools for improving our understanding of the mechanisms linking fire, food webs, and fish and for identifying contexts where fires could have deleterious impacts on fishes.

Oregon, Washington↗
USGS2025

Sequoia and Sequoiadendron: Two paleoendemic megatrees with markedly different adaptive responses to recent high-severity fires

Premise Coast redwood ( Sequoia sempervirens ) and giant sequoia ( Sequoiadendron giganteum ) are two iconic paleoendemic species with limited distributions, well known for their spectacular size. Recently, they have been exposed to high-severity crown fires, with starkly contrasting responses. Methods We used all available published literature and field observations to understand the responses to fire in an evolutionary context. Results Coast redwoods, found in California's coastal rainforests, were highly resilient to high-severity fires, with most trees surviving due to their ability to resprout from the base and trunk, though seedling regeneration was largely lacking. In contrast, giant sequoias, native to the Sierra Nevada, do not resprout, leading to significant tree mortality after very high-severity fires; they released seeds only in patches where some trees survived moderately high-severity fires. Conclusions These high-severity fires were novel events for giant sequoias, but not for coast redwoods. Fire suppression has disrupted the natural fire regime in the giant sequoia ecosystem by preventing frequent lightning-caused surface fires, resulting in high-severity fires that killed a substantial number of these giants. In coast redwood forests, infrequent but high-severity crown fires were the norm before burning by Native Americans. Frequent, low-severity burning by Native Americans over the past few hundred years was localized and 20 th -century fire suppression has returned the natural fire regime to these forests. The recent crown fires do not represent a threat to redwood conservation; however, other management goals may require emulating Native American burning practices and in some cases may be best termed cultural restoration.

American Journal of Botany↗
USGS2006

Three decades of urbanization: Estimating the impact of land-cover change on stream salamander populations

Urbanization has become the dominant form of landscape disturbance in parts of the United States. Small streams in the Piedmont region of the eastern United States support high densities of salamanders and are often the first habitats to be affected by landscape-altering factors such as urbanization. We used US Geological Survey land cover data from 1972 to 2000 and a relation between stream salamanders and land cover, established from recent research, to estimate the impact of contemporary land-cover change on the abundance of stream salamanders near Davidson, North Carolina, a Piedmont locale that has experienced rapid urbanization during this time. Our analysis indicates that southern two-lined salamander ( Eurycea cirrigera ) populations have decreased from 32% to 44% while northern dusky salamanders ( Desmognathus fuscus ) have decreased from 21% to 30% over the last three decades. Our results suggest that the widespread conversion of forest to urban land in small catchments has likely resulted in a substantial decline of populations of stream salamanders and could have serious effects on stream ecosystems.

Biological Conservation↗
USGS2026

Multi-temporal mapping and analyses of post-wildfire surface soil moisture modeled from Landsat Thermal-IR and Sentinel-1 SAR

Wildfires alter surface soil moisture by consuming vegetation and exposing the soil to increased solar radiation, increased precipitation throughfall, and reduced infiltration from soil hydrophobicity. This can affect the water balance within the watershed and, in turn, influence post-fire nutrient cycling and ecosystem succession. Modeling surface soil moisture over large areas using satellite remote sensing can aid monitoring of soil moisture patterns and dynamics. We trained a random forest regression model using an in situ soil moisture network and examined pre- and post-fire soil moisture dynamics for three wildfires that burned in 2016 and 2017 in coastal California, U.S.A. Model inputs included Sentinel-1A synthetic aperture radar (SAR) and Landsat thermal infrared imagery (TIR), which produced a high resolution (30 m) soil moisture map time series with 18–20 estimates across 2 years. An unbiased root mean square error of 0.065 and an r 2 of 0.624 indicates a good fit between the model and reference data. We found a significant interaction between treatment (wildfire or unburned) and period (before or after wildfire) by examining the modeled surface soil moisture in high-severity burned areas. Before-after control-impact metrics showed that modeled surface soil moisture was lower after each fire within wildfire areas compared to unburned controls, and overall changes in soil moisture were greater in the wildfire perimeters than unburned areas. These results demonstrate the potential of Sentinel-1 SAR and Landsat TIR data for the development of high-resolution soil moisture time series products to support monitoring and assessment of post-fire soil hydrologic conditions.

California↗
USGS2013

Significance of headwater streams and perennial springs in ecological monitoring in Shenandoah National Park

Shenandoah National Park has been monitoring water chemistry and benthic macroinvertebrates in stream ecosystems since 1979. These monitoring efforts were designed to assess the status and trends in stream condition associated with atmospheric deposition (acid rain) and changes in forest health due to gypsy moth infestations. The primary objective of the present research was to determine whether the current long-term macroinvertebrate and water-quality monitoring program in Shenandoah National Park was failing to capture important information on the status and trends in stream condition by not sufficiently representing smaller, headwater streams. The current benthic-macroinvertebrate and water-chemistry sampling designs do not include routine collection of data from streams with contributing watershed areas smaller than 100 hectares, even though these small streams represent the overwhelming proportion of total stream length in the park. In this study, we sampled headwater sites, including headwater stream reaches (contributing watershed area approximately 100 hectares (ha) and perennial springs, in the park for aquatic macroinvertebrates and water chemistry and compared the results with current and historical data collected at long-term ecological monitoring (LTEM) sites on larger streams routinely sampled as part of ongoing monitoring efforts. The larger purpose of the study was to inform ongoing efforts by park managers to evaluate the effectiveness and efficiency of the current aquatic monitoring program in light of other potential stressors (for example, climate change) and limited resources. Our results revealed several important findings that could influence management decisions regarding long-term monitoring of park streams. First, we found that biological indicators of stream condition at headwater sites and perennial springs generally were more indicative of lower habitat quality and were more spatially variable than those observed at sites on routinely monitored larger streams. We hypothesized that poorer stream condition observed in smaller streams was due to stream drying that occurs more frequently in headwater areas. We also found that biological and water-chemistry measures responded differently to landscape drivers. Variation in most biological endpoints was driven primarily by stream size and was only secondarily associated with bedrock geology. In contrast, water chemistry showed essentially the opposite pattern, with underlying geology explaining much of the variation and stream size being of secondary importance. Therefore, expanding the LTEM program to include headwater areas would yield substantially different biological information, whereas broad inferences regarding spatial patterns in water chemistry would probably not change. Although significant differences in community composition were observed among streams of different sizes, no taxa were unique to headwater sites. All taxa collected at the 45 headwater sites also had been collected at one or more LTEM sites during one or more years. This observation indicates that headwater sites in the park may be structured by biotic nestedness; consequently, focusing management efforts on preserving the species pool at the larger LTEM sites would likely result in the protection of most taxa parkwide. Finally, linkages (correlations) between water chemistry and biological measures of stream condition were signficantly stronger when assessed at the LTEM sites than when assessed at the springs or headwater sites, indicating that conditions at downstream sites may be better indicators of water-quality trends.

Virginia↗
USGS2021

Impacts of climate changes and amplified natural disturbance on global ecosystems

Natural disturbances maintain biological diversity and landscape heterogeneity and initiate ecosystem renewal and reorganization. However, the severity, frequency, and extent of many disturbances have increased substantially in recent decades as the result of anthropogenic climate change. Disturbances can be discrete, short-duration events, such as wildfires or hurricanes, or can exert persistent, cumulative stresses on an ecosystem (for example, ongoing warming of ocean or land surface temperatures). Landscape and ecosystem impacts can occur from a single disturbance, from several disturbances acting independently, or from the interactions of multiple, linked disturbances. Key, climate-related disturbances affecting global biomes and ecosystems include shifting temperature and hydrologic regimes (for example, warming surface temperatures and increasing aridity), increased frequency and magnitude of extreme events such as heatwaves, severe droughts, storms, and hurricanes, warming-induced permafrost thaw, and heightened wildfire activity and insect-caused tree mortality. For ecosystems and landscapes, the consequences of climate-amplified disturbance include forced poleward and upward movement of plant and animal species, widespread tree mortality and reduced forest productivity, changes in plant community structure and species distributions, reduced biodiversity, increased erosion, debris flows, wetland dynamism, declining sea ice extent, more frequent storm-driven tides and saltwater intrusion, and increased landscape flammability.

Book chapter↗
USGS2010

Surface elevation change and susceptibility of different mangrove zones to sea-level rise on Pacific high islands of Micronesia

Mangroves on Pacific high islands offer a number of important ecosystem services to both natural ecological communities and human societies. High islands are subjected to constant erosion over geologic time, which establishes an important source of terrigeneous sediment for nearby marine communities. Many of these sediments are deposited in mangrove forests and offer mangroves a potentially important means for adjusting surface elevation with rising sea level. In this study, we investigated sedimentation and elevation dynamics of mangrove forests in three hydrogeomorphic settings on the islands of Kosrae and Pohnpei, Federated States of Micronesia (FSM). Surface accretion rates ranged from 2.9 to 20.8 mm y −1 , and are high for naturally occurring mangroves. Although mangrove forests in Micronesian high islands appear to have a strong capacity to offset elevation losses by way of sedimentation, elevation change over 6½ years ranged from −3.2 to 4.1 mm y −1 , depending on the location. Mangrove surface elevation change also varied by hydrogeomorphic setting and river, and suggested differential, and not uniformly bleak, susceptibilities among Pacific high island mangroves to sea-level rise. Fringe, riverine, and interior settings registered elevation changes of −1.30, 0.46, and 1.56 mm y −1 , respectively, with the greatest elevation deficit (−3.2 mm y −1 ) from a fringe zone on Pohnpei and the highest rate of elevation gain (4.1 mm y −1 ) from an interior zone on Kosrae. Relative to sea-level rise estimates for FSM (0.8–1.8 mm y −1 ) and assuming a consistent linear trend in these estimates, soil elevations in mangroves on Kosrae and Pohnpei are experiencing between an annual deficit of 4.95 mm and an annual surplus of 3.28 mm. Although natural disturbances are important in mediating elevation gain in some situations, constant allochthonous sediment deposition probably matters most on these Pacific high islands, and is especially helpful in certain hydrogeomorphic zones. Fringe mangrove forests are most susceptible to sea-level rise, such that protection of these outer zones from anthropogenic disturbances (for example, harvesting) may slow the rate at which these zones convert to open water.

Ecosystems↗
USGS2020

Keystone predators govern the pathway and pace of climate impacts in a subarctic marine ecosystem

Predator loss and climate change are hallmarks of the Anthropocene yet their interactive effects are largely unknown. Here, we show that massive calcareous reefs, built slowly by the alga Clathromorphum nereostratum over centuries to millennia, are now declining because of the emerging interplay between these two processes. Such reefs, the structural base of Aleutian kelp forests, are rapidly eroding because of overgrazing by herbivores. Historical reconstructions and experiments reveal that overgrazing was initiated by the loss of sea otters, Enhydra lutris (which gave rise to herbivores capable of causing bioerosion), and then accelerated with ocean warming and acidification (which increased per capita lethal grazing by 34 to 60% compared with preindustrial times). Thus, keystone predators can mediate the ways in which climate effects emerge in nature and the pace with which they alter ecosystems.

Science↗
USGS2004

Biomass accumulation and soil nitrogen availability in an 87-year-old Populus grandidentata chronosequence

The Upper Lake States region is marked by major disturbances of fire and logging over 100 years ago that created a landscape mosaic of early successional forests. Given the intimate link between soil N availability and forest growth in this region, it is important to understand how temporal changes in soil N constrain the rate at which forest biomass accumulates following a stand-destroying disturbance. Bigtooth aspen (Populus grandidentata Michx.) currently dominates sites where primarily old-growth pine-hemlock-oak forests once thrived, which provides an opportunity to observe nearly 100 years of succession following severe disturbance. In this study, we examine the relationship between soil N availability and biomass accrual in a series of plots undergoing secondary succession following logging and burning. Our results demonstrate that total aboveground biomass and nitrogen accrual patterns are strongly and positively related on a highly disturbed, bigtooth aspen-dominated ecosystem in northern Lower Michigan. Nitrogen mineralization and nitrification were highest immediately following disturbance, and then decreased over the next approximately 20 years of succession. Following this short-term decrease, these processes increased and attained a maximum value after 70 years of forest succession. Understory biomass accumulation showed the opposite trend of nutrient availability, with highest values during the first 20 years of succession, followed by a dramatic decrease for the next 70 years. Understory biomass began to decrease as plants grew into the overstory or died. Total aboveground biomass was correlated with N mineralization (r=0.894; P=0.041) and nitrification (r=0.782; P=0.118) and appears to be increasing steadily to some maximum that has not yet been reached. ?? 2003 Elsevier B.V. All rights reserved.

Forest Ecology and Management↗