Comparison of Forest Inventory and Analysis surveys, basal area models, and fitting methods for the aspen forest type in Minnesota

The Forest Inventory and Analysis (FIA) unit of the U.S. Forest Service has collected, compiled, and made available plot data from three measurement periods (identified as 1977, 1990, and 2003, respectively) within Minnesota. Yet little if any research has compared the relative utility of these datasets for developing empirical yield models. This paper compares these and other subdatasets in the context of fitting a basal area (B) yield model to plot data from the aspen (Populus tremuloides Michx.) forest type. In addition, several models and fitting methods are compared for their applicability and stability over time. Results suggest that the three parent datasets, along with their subdatasets, provide very similar three parameter B yield model prediction capability, but as model complexity increases, variability in coefficient estimates increases between datasets. The absence of data for older aspen stands and the inherent noise within B data prevented the exact determination of an overall best model. However, the model B = b₁S^b₂(1 − exp( − b₃A)) with site index (S) and stand age (A) as predictors was found consistently among the highest in precision and stability. Additionally, nonlinear least squares and nonlinear mixed-effects fitting procedures produced similar model fits, but the latter is preferred for its potential to improve model projections. The results indicate little practical difference between datasets from different time periods and different sizes when used for fitting the models. Additionally, these results will likely extend to other states or regions with similar remeasurement data on aspen and other forest types, thus facilitating the development of other ecological models focused on forest management.     

Characteristics of aspen infected with heartrot: Implications for cavity-nesting birds

Phellinus tremulae is an important fungal decay agent common to aspen and a critical component to the cavity-nesting bird complex found in western aspen stands. Little information exists on the conditions that facilitate infection and spread of P. tremulae in aspen forests. I used Forest Inventory and Analysis (FIA) data to explore the relationships of several tree and stand characteristics to the presence and frequency of P. tremulae in aspen measured across several western states of the United States. Results suggest a strong relationship between tree age, tree diameter, and compacted crown ratio with infection frequency in trees while stand purity, canopy cover and stand age had a positive relationship with the occurrence of P. tremulae in forest stands containing aspen. Logistic regression modeling identified stand age as the only variable that increased the odds of predicting infection at the stand-level while all tree-level variables were included in the tree model. Data also show that infection rates in the study area were lower than in other parts of aspen's range, and that average size of infected trees was smaller in the study area than those reported elsewhere. These results have important implications to management of aspen for wildlife, especially for birds that use decayed aspen for nesting.     

Weighted analysis methods for mapped plot forest inventory data: Tables,regressions, maps and graphs

Weighted estimation methods for analysis of mapped plot forest inventory data are discussed. The appropriate weighting scheme can vary depending on the type of analysis and graphical display. Both statistical issues and user expectations need to be considered in these methods. A weighting scheme is proposed that balances statistical considerations and the logical expectations of users. The methods described here are being used in an online forest carbon estimation tool. Example applications are presented to demonstrate the methods.     

工业硫化钠中铁含量流动注射分析方法的研究

以硫氰酸钾做显色剂，水做载流，研究了工业硫化碱中铁含量的流动注射分析方法，并依据该产品的部颁标准分析方法的原理及对固体硫化碱样品进行标准条件的前处理，得到合格的标准待测样品溶液。而后，再结合流动注射分析方法的原理及特点，对某－甲种－级品的工业硫化钠待测样品溶液进行６次重复测定，标准误差为０．００１％，变异系数为２．２％。在较理想的条件下，着重研究了显色剂含量对吸光度的影响，待测样品溶液的注射时间，     

塿土速效磷流动注射分析研究

流动注射分析(FIA)是70年代以来发展起来的一种快速、高灵敏度、高准确度的微量分析技术,已在工农业、环境科学、医药卫生等领域中得到广泛的应用。关于土壤速效磷的FIA测定,1980年孙励敬等已作过报道,但仪器的差异和各地土壤的特点,使该法在具体实验室应用时,需作进一步的引进和探索。我们对瑞典制造的FIA5020型流动注射分析仪测磷的性能进行了研究,确定了样品浓度、进样时间、进样体积和反应管长度对分析灵敏度、准确度的影响,测定速度达每小时130样次。同时采集武功、澄城塿土样品,用Olsen法浸提,浸提液用FIA法和常规钼锑抗比色法测定速效磷,对其结果进行比较检验,以期用FIA法代替常规分析法。     

Forest productivity and tree diversity relationships depend on ecological context within mid-Atlantic and Appalachian forests (USA)

Factors influencing the relationship between ecosystem productivity and biological diversity form the basis of much ecological theory. An understanding of how productivity-diversity relationships are influenced by scale of observation and unique attributes of ecoregions may provide important insights to aid conservation planning for carbon retention and biodiversity. Here we use publically available datasets to investigate patterns of productivity-diversity and explore potential factors influencing these patterns in forests located in five mid-Atlantic and Appalachian states. We used a geographic information system (GIS) to overlay multiple publically available datasets including remotely sensed estimates of productivity from MODIS and tree diversity estimated from the forest inventory analysis (FIA) database. We evaluated productivity-diversity relationships using two scales of observation (among and within ecoregions). We also determined if productivity-diversity relationships might be related to region-wide patterns in land use, and if the relationships varied by forest type, land management zones, and along gradients of mean productivity and diversity. Productivity-diversity relationships depended on scale and varied among ecoregions, and land use was correlated with both productivity and diversity. Mountainous ecoregions were characterized by positive productivity-diversity relationships, whereas coastal ecoregions were characterized by negative productivity-diversity relationships. Forest types and management zones that were on average less productive and more diverse exhibited positive productivity-diversity relationships across stands (the most productive stands were more diverse). In contrast, ecoregions and forest types that were on average more productive and less diverse exhibited negative productivity-diversity relationships (the most productive stands were less diverse). In conclusion, regional and local ecological and anthropogenic factors likely influence productivity-diversity relationships and these relationships appear to change along gradients of productivity and diversity.     

流动注射在线消解测定水中总氮的研究

总氮(TN)是衡量水质富营养化的重要指标。传统分析方法需经过高压消解,存在操作复杂及费时的局限,且自动化程度低。流动注射分析(FIA)方法具有分析速度快、检出限低和准确度高等优势。试验结果表明,采用流动注射在线消解测定水中TN,检出限为0.015 mg/L,检测范围为0.12～10.00 mg/L,相对标准差为1.6%～4.2%,实际水样的加标回收率为98.5%～108.0%,标样测定均在保证值范围之内,能较好地满足地表水及SS含量较少的排放废水中TN监测要求。     

Patterns of exotic plant invasions in Pennsylvania’s Allegheny National Forest using intensive Forest Inventory and Analysis plots

Intensive Forest Inventory and Analysis (FIA) plot data collected in the Allegheny National Forest (ANF), Pennsylvania, between 1999 and 2006 were evaluated for their ability to predict ANF’s vulnerability to invasion by exotic plants. A total of 26 variables classified by biotic, abiotic, or disturbance characteristics were examined. Likelihood of colonization by invasive exotic and non-invasive exotic plants was analyzed using a logistic regression model. Approximately, 11% of the 449 species documented in these plots were exotic, which is higher than has been found in other northeastern forested plots. Only 1% of the ANF flora was invasive exotic plants and these were at low abundance, confirming that most invasions are still at an early stage of establishment. Sites richer in native or non-invasive exotic plants and with more alkaline soils were more likely to be invaded. Younger forests, forests with non-forest patches present, and forests rich in native species were more likely to be colonized by exotic (invasive or non-invasive) plants. Frangula alnus, which is starting to spread locally, differed from the other invasive exotic species in terms of its association with high sapling density to tree density ratios, high soil nitrogen levels, and the presence of fire. Variables representing mortality due to beech bark disease and distance to the nearest exotic planting manifested counterintuitive results. In both cases, the combined occurrence of mortality due to beech bark disease or a close (less than 500 m away) known propagule source and the presence of an invasive or non-invasive exotic plant was rare. We encourage increased use of intensive sampling for FIA in the U.S.A. and similar monitoring programs in other countries, but suggest adding a step to the plot selection phase that would allow forest-wide or regional stratified sampling of typically coarse-scale variables, such as historic or predicted defoliation or fire events, and forest or land type. A more accurate picture of the importance of disturbance variables in defining forest vulnerability to plant invasion may be achieved.     

Automated Modification of the Molybdenum Blue Colorimetric Method for Phosphorus Determination in Soil Extracts

A flow injection analysis (FIA) method capable of automation for molybdate reactive phosphorus (P) determination in soil extracts is described. Results obtained using this method in three soil extracts [calcium chloride (CaCl₂), Olsen, and Mehlich I] were the same as those provided by the manual molybdate blue colorimetric method. Linear range extending to 2 mg P L^?1, detection limits ranging from 6 to 26 µg L^?1 depending on the soil extract, and accurate recoveries from P‐spiked samples were achieved. The sensitivity of the system was around 0.3 absorbance units per mg P L^?1, and the sampling frequency was 72 samples h^?1, higher than those described for most of the flow injection methods.     

Separating effects of changes in atmospheric composition,climate and land-use on carbon sequestration of U.S. Mid-Atlantic temperate forests

Terrestrial carbon dynamics have been vastly modified because of changes in atmospheric composition, climate, and land-use. However, few studies provide a complete analysis of the factors and interactions that affect carbon dynamics over a large landscape. This study examines how changes in atmospheric composition (CO₂, O₃ and N deposition), climate and land-use affected carbon dynamics and sequestration in Mid-Atlantic temperate forests during the 20th century. We modified and applied the PnET-CN model, a well established process-based ecosystem model with a strong foundation of ecosystem knowledge from experimental studies. We validated the model results using the U.S. Forest Inventory and Analysis (FIA) data. Our results suggest that chronic changes in atmospheric chemistry over the past century markedly affected carbon dynamics and sequestration in Mid-Atlantic temperate forests, while climate change only had a minor impact although inter-annual climatic variability had a far more substantial effect. The NPP response to a century of chronic change in atmospheric composition at the regional scale was an increase of 29%, of which, 14% was from elevated CO₂, 17% from N deposition, 6% from the interaction between CO₂ and N deposition, and minus 8% from tropospheric ozone. Climate change increased NPP by only 4%. Disturbed forests had 6% lower NPP than undisturbed forests after seven decades. Regrowing forests after harvesting and natural disturbances had much greater capacity for sequestering carbon than undisturbed old-growth forests even though the newer forests had slightly lower net primary production (NPP). The modeling results indicated that N deposition was a stronger force than elevated CO₂ for increasing NPP and fast turnover tissues, while elevated CO₂ favored more sustainable carbon storage and sequestration. The model results are consistent with various experiments and observations and demonstrate a powerful approach to integrate and expand our knowledge of complex interactive effects of multiple environmental changes on forest carbon dynamics.