Usda Forest Service Northern Research Station

Baltimore Highlands, MD, United States

Usda Forest Service Northern Research Station

Baltimore Highlands, MD, United States
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Duan S.,The Interdisciplinary Center | Delaney-Newcomb K.,The Interdisciplinary Center | Kaushal S.S.,The Interdisciplinary Center | Findlay S.E.G.,Cary Institute of Ecosystem Studies | Belt K.T.,Usda Forest Service Northern Research Station
Biogeochemistry | Year: 2014

Leaf litter plays a critical role in regulating ecological functions in headwater forest streams, whereas the effects of leaves on water quality in urbanized streams are not fully understood. This study examined the potential importance of leaf litter for the release and transformations of organic carbon and nutrients in urban streams, and compared the effects with other types of natural organic substrates (periphyton and stream sediment). Nutrients and organic carbon were leached from senescent leaves of 6 tree species in the laboratory with deionized water, and maximal releases, leaching rate constants, composition and bioavailability of the leached dissolved organic carbon (DOC) were determined. Stream substrates (leaf debris, rocks with periphyton, and sediment) were seasonally collected from urban and forest reference streams of the NSF Baltimore Long-term Ecological Research Site and incubated with overlying stream water to estimate areal fluxes of DOC and nitrogen. Leaf litter leaching showed large ranges in maximal releases of DOC (7.0–131 mg g−1), dissolved organic nitrogen (DON; 0.07–1.39 mg g−1) and total dissolved phosphorus (TDP; 0.14–0.70 mg g−1) among tree species. DOC leaching rate constants, carbon to nitrogen ratios, and DOC bioavailability were all correlated with organic matter quality indicated by fluorescence spectroscopy. Results from substrate incubation experiments showed far higher DOC and DON release and nitrate retention with leaf debris than with sediment, or rocks with periphyton. DOC release from leaf debris was positively correlated with stream nitrate retention at residential and urban sites, with the highest values observed during the fall and lowest during the summer. This study suggests the potential importance of leaf litter quantity and quality on fostering DOC and nutrient release and transformations in urban streams. It also suggests that species-specific impacts of leaves should be considered in riparian buffer and stream restoration strategies. © 2014, Springer International Publishing Switzerland.


George A.D.,University of Missouri | Thompson F.R.,Usda Forest Service Northern Research Station | Faaborg J.,University of Missouri
Remote Sensing Letters | Year: 2015

A spatial mismatch exists between regional climate models and conditions experienced by individual organisms. We demonstrate an approach to downscaling air temperatures for site-level studies using airborne LiDAR data and remote microclimate loggers. In 2012-2013, we established a temperature logger network in the forested region of central Missouri, USA, and obtained sub-hourly meteorological measurements from a centrally located weather station. We then used linear mixed models within an information theoretic approach to evaluate hourly and seasonal effects of insolation, vegetation structure, elevation, and meteorological measurements on near-surface air temperatures. The best-supported models predicted fine-scale temperatures with high accuracy during both the winter and growing seasons. We recommend that researchers consider the scales relevant to specific applications when using our approach to develop site-specific spatio-temporal models. © 2015 Taylor & Francis.


O'Donnell K.M.,University of Missouri | Thompson F.R.,Usda Forest Service Northern Research Station | Semlitsch R.D.,University of Missouri
PLoS ONE | Year: 2015

Detectability of individual animals is highly variable and nearly always < 1; imperfect detection must be accounted for to reliably estimate population sizes and trends. Hierarchical models can simultaneously estimate abundance and effective detection probability, but there are several different mechanisms that cause variation in detectability. Neglecting temporary emigration can lead to biased population estimates because availability and conditional detection probability are confounded. In this study, we extend previous hierarchical binomial mixture models to account for multiple sources of variation in detectability. The state process of the hierarchical model describes ecological mechanisms that generate spatial and temporal patterns in abundance, while the observation model accounts for the imperfect nature of counting individuals due to temporary emigration and false absences. We illustrate our model's potential advantages, including the allowance of temporary emigration between sampling periods, with a case study of southern red-backed salamanders Plethodon serratus. We fit our model and a standard binomial mixture model to counts of terrestrial salamanders surveyed at 40 sites during 3-5 surveys each spring and fall 2010-2012. Our models generated similar parameter estimates to standard binomial mixture models. Aspect was the best predictor of salamander abundance in our case study; abundance increased as aspect became more northeasterly. Increased time-since-rainfall strongly decreased salamander surface activity (i.e. availability for sampling), while higher amounts of woody cover objects and rocks increased conditional detection probability (i.e. probability of capture, given an animal is exposed to sampling). By explicitly accounting for both components of detectability, we increased congruence between our statistical modeling and our ecological understanding of the system. We stress the importance of choosing survey locations and protocols that maximize species availability and conditional detection probability to increase population parameter estimate reliability.


Stanton R.A.,University of Missouri | Thompson F.R.,Usda Forest Service Northern Research Station | Kesler D.C.,University of Missouri
Journal of Wildlife Management | Year: 2015

Knowledge about species' responses to habitat restoration can inform subsequent management and reintroduction planning. We used repeated call-response surveys to study brown-headed nuthatch (Sitta pusilla) patch occupancy at the current limits of its apparently expanding range in an area with active habitat restoration. We fit a probit occupancy model that accounted for spatial autocorrelation using restricted spatial regression. Nuthatch occupancy was related to patch-level vegetation structure and range-extension context, i.e., latitude, but not prescribed fire history. Latitude and percent tree stocking had a negative relationship with occupancy (coefficients and 95% credible intervals: -1.07 [CI: -1.63, -0.67] and -0.63 [CI: -0.97, -0.350]). The density of recently killed and well-decayed snags had positive associations with occupancy (coefficients and 95% credible intervals: 0.57 [CI: 0.17, 1.16] and 0.37 [CI: 0.05, 0.72]). Neither grassy herbaceous cover nor percent of stocking in pine were associated with occupancy. We found that restoration efforts created suitable stand structure for brown-headed nuthatches, but many restored sites in the range-extension zone appeared to be vacant. Occupied habitats in the range-extension zone had fewer snags, less frequent fire, and more shrub cover than occupied sites where the species was established. Release from conspecific competition may have permitted nuthatches in the range-extension zone to exploit habitats that would otherwise have been marginal. Alternatively, nuthatches may be restricted to such sites although there are more suitable sites tens of kilometers away. Experimental translocations and reintroductions could determine how habitat structure and nuthatch density affect the quality of restored sites in the range-extension zone and enable those sites to achieve their biodiversity potential. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. © Published 2015. This article is a U.S. Government work and is in the public domain in the USA.


PubMed | University of Missouri and Usda Forest Service Northern Research Station
Type: Journal Article | Journal: PloS one | Year: 2015

Detectability of individual animals is highly variable and nearly always < 1; imperfect detection must be accounted for to reliably estimate population sizes and trends. Hierarchical models can simultaneously estimate abundance and effective detection probability, but there are several different mechanisms that cause variation in detectability. Neglecting temporary emigration can lead to biased population estimates because availability and conditional detection probability are confounded. In this study, we extend previous hierarchical binomial mixture models to account for multiple sources of variation in detectability. The state process of the hierarchical model describes ecological mechanisms that generate spatial and temporal patterns in abundance, while the observation model accounts for the imperfect nature of counting individuals due to temporary emigration and false absences. We illustrate our models potential advantages, including the allowance of temporary emigration between sampling periods, with a case study of southern red-backed salamanders Plethodon serratus. We fit our model and a standard binomial mixture model to counts of terrestrial salamanders surveyed at 40 sites during 3-5 surveys each spring and fall 2010-2012. Our models generated similar parameter estimates to standard binomial mixture models. Aspect was the best predictor of salamander abundance in our case study; abundance increased as aspect became more northeasterly. Increased time-since-rainfall strongly decreased salamander surface activity (i.e. availability for sampling), while higher amounts of woody cover objects and rocks increased conditional detection probability (i.e. probability of capture, given an animal is exposed to sampling). By explicitly accounting for both components of detectability, we increased congruence between our statistical modeling and our ecological understanding of the system. We stress the importance of choosing survey locations and protocols that maximize species availability and conditional detection probability to increase population parameter estimate reliability.

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