Russell D. Briggs

Biomass and nutrient removal by willow clones in experimental bioenergy plantations in New York State

The development of short-rotation intensive cultural (SRIC) willow systems as a source of bioenergy and bioproducts is growing in the northeastern and midwestern United States. Important data for sustainable management such as nutrient removal and nutrient use e8ciency in willow bioenergy plantations is lacking. This study reports wood biomass production, annual removal of nutrients, and nutrient use e8ciency in experimental plantings of SRIC willow and poplar at Tully, New York. E9ects of clone, fertilization, irrigation, planting density, and harvest cycle were analyzed. Annual biomass production of 15 –22 dry Mg=ha removed 75 –86, 10 –11, 27–32, 52–79 and 4 –5 kg=ha=year of N, P, K, Ca and Mg, respectively. For all the variables studied, the responses depended on clone. Fertilization and irrigation increased rates of nutrient removal by means of increased biomass production. Unlike planting density, harvest cycle signiBcantly a9ected rates of nutrient removal and nutrient use e8ciency. For clone SV1 ( Salix dasyclados), an irrigated and fertilized planting with a density of 36,960 trees=ha harvested on a 3-year rotation had the highest biomass production and nutrient use e8ciency, and the lowest rates of nutrient removal. The annual harvest cycle had the lowest nutrient use e8ciency and the highest annual removal of nutrients suggesting that this choice would be most appropriate for biomass crops that are to be used as bu9er strips to manage nutrient runo9 from agricultural Belds. An appropriate choice of clone, planting density, and harvest cycle could tailor the rates of nutrient removal and nutrient use e8ciency to match the objective of the planting. c 2001 Elsevier Science Ltd. All rights reserved.

Effect of organic amendments and slow-release nitrogen fertilizer on willow biomass production and soil chemical characteristics

Abstract Lime-stabilized sewage sludge and composted poultry manure, at a rate of 250 m 3 ha −1 each, and slow-release N fertilizer (Scotts Osmocote) at 100, 200 and 300 kg N ha −1 , were applied to plots of willow biomass crops during the first season of a three-year growth cycle. Stem biomass production was measured annually and soil chemical characteristics were assessed at the end of the growth cycle. Average annual stem biomass production was 8– 11 Mg ha −1 in slow-release N fertilized plots corresponding to a yield increase of 7–33% relative to control plots. In organically amended plots, annual stem biomass production increased by 30–38% relative to control plots. The study suggests that organically amended willows grew at a slightly faster rate than slow-release N fertilized willows. Statistically, the relationship between slow-release N application rate and stem biomass production was not highly significant; applications of slow-release N in excess of 100 kg N ha −1 provided no additional yield benefits. Differences in soil characteristics were most strongly expressed in surface soil. The pH at 0– 10 cm depth was 1 and 2 units higher on lime-stabilized sludge and composted poultry manure plots, respectively. Concentrations of soil K, P and Mg were dramatically higher in the composted poultry manure soils. The highest soil organic matter and N levels were observed in the surface horizons of organically amended soils. Utilization of organic residuals increases biomass production, provides beneficial use for wastes, reducing production costs and contributing to the sustainability of biomass production systems.

Forest floor carbon pools and fluxes along a regional climate gradient in Maine, USA

Global carbon (C) reserves in soil are large compared with atmospheric stocks (in the form of CO2 and methane), so small changes in soil C storage will have a significant effect on atmospheric CO2 concentrations. In order to better understand the consequences of global climate change, it is essential that we define how soil C storage is influenced by changes in temperature and moisture that are expected as a result of global climate change. Forest floor carbon pools and fluxes were evaluated at 16 northern hardwood sites located within four distinct climate regions (Northern, Central, Southern and Coastal) in Maine. Mean annual air temperature at the sites ranged from 2.0°C in the Northern region to 6.2°C in the Coastal region and average annual precipitation ranged from 90 cm in the Northern region to 140 cm in the Coastal region. Leaf litter mass and leaf litter C flux were not correlated with temperature indices and did not vary among regions. However, they were positively correlated with annual precipitation, suggesting that litter production was controlled, in part at least, by precipitation but not by temperature. Northern sites stored more C in the forest floor than Coastal sites, and they experienced slower decomposition rates. Because soil and vegetation characteristics of these sites were similar, we attribute these trends to differences in climate. Indeed, C turnover time was correlated with latitude and temperature indices. Slower decomposition in the Northern region was attributed to a combination of lower specific activity at temperatures below 13°C, cooler average temperatures and a shorter frost-free season. Soil respiration at each site was positively correlated with temperature and the slope of the relationship increased with latitude, indicating that the ability of the soil biota to respire C varied with climate. A predictive equation is presented that accounts for the change in slope with latitude. Because C loss through soil respiration was more sensitive to temperature than C inputs from litter, any regional warming in the next century may lead to a decrease in forest floor carbon storage. However, if precipitation increases with temperature, then litter C flux may increase and offset the increase in soil respiration.

Nitrogen mineralization of sewage sludge and composted poultry manure applied to willow in a greenhouse experiment

Abstract Nitrogen requirements for production of intensively cultured willow for use as a bioenergy crop coupled with the need for safe disposal of nutrient rich organic wastes provide an opportunity to reduce costs associated with bioenergy plantations. In order to minimize N leaching from sites treated with organic wastes, knowledge of the rate of N mineralization is needed. The objective of this study was to assess N mineralization rates of four organic residuals in a controlled greenhouse environment: composted poultry manure, composted sewage sludge, and anaerobically digested sewage sludge from two different municipalities. Thirty-six weeks after application, disappearance of the mass initially applied ranged from 20% to 50%. Gross nitrogen mineralization rate (N mass released expressed as a percentage of initially applied N) ranged from 12% to 57%. Non-composted treatments released greater amounts of nitrogen than composted treatments. Within composted treatments, net N release was estimated as 325 kg N ha −1 for poultry manure and 86 kg N ha −1 for sewage sludge. Syracuse and New York City sewage sludges, with 57% and 30% gross N release rates respectively, provided approximately 360 and 240 kg plant available N ha −1 , respectively. These estimates of N release suggest that the application rates could be halved and that sufficient N would be provided to meet crop needs and reduce leaching losses.

Indices of forest floor nitrogen status along a climate gradient in Maine, USA

Abstract Nitrogen has long been recognized as the most commonly limiting nutrient for plant production throughout the world. Yet, air pollution has created a modern chemical climate that has sometimes resulted in excess ecosystem N due to N deposition. In addition, climate warming could accelerate N cycling and N export from forested ecosystems. The result is increasing interest in understanding forest ecosystem N dynamics. This study used recently delineated climatic regions in Maine to investigate the possible influences of forest species composition, and energy and moisture gradients, on laboratory indices of forest floor N cycling. Concentrations of N and C, and potential net nitrification, potential net ammonification, and potential net N mineralization, were measured on forest floor samples from 20 sites distributed across Maine in both hardwood and softwood stands. Both forest types had nearly identical concentrations of N in the forest floor (∼1.6%), but the mean C/N ratio (28) under softwoods was significantly higher than that under hardwoods (24) due to higher concentrations of total C in soils under conifers. Forest floor N concentration was a better predictor of potential net N mineralization than was total C or C/N ratio. Although the most northerly region in this study was predictably the coldest, it was also the region with the highest values for total N and N cycling indices. Wet N deposition for the region indicates N deposition differences are not responsible for this spatial pattern, and further work is warranted to explain these results. Laboratory incubation measures of potential net N mineralization were significantly correlated with in situ annual net N mineralization, which supports the use of these techniques for forest soil N status evaluations. Most site measures of mean temperatures were negatively correlated with soil N indices indicating that warmer sites had lower rates of N cycling. Although differences existed in forest floor N characteristics between climate regions, they could not be predicted by simple relationships with temperature.

Evaluating hybrid poplar clonal growth potential in a three-year-old genetic selection field trial

Abstract Survival, growth, and insect and disease damage of 54 hybrid poplar clones were compared in a three-year-old genetic selection field trial located in the St Lawrence River Valley, near Massena, New York, USA. Clones were grouped into growth potential classes using cluster analysis and indices of total growth and canker severity. Statistical significance of growth potential classes was tested using discriminant analysis. Seven of the 54 clones examined (DN16, NM6, NE17, D51, DN38, DN55 and NE21) were recommended for additional evaluations in larger scale clone-site trials. The technique presented in this report facilitates hardwood clone performance evaluation for a wide variety of desired products.

Phosphorus concentrations in soil and subsurface water: a field study among cropland and riparian buffers.

Riparian buffers can be effective at removing phosphorus (P) in overland flow, but their influence on subsurface P loading is not well known. Phosphorus concentrations in the soil, soil solution, and shallow ground water of 16 paired cropland-buffer plots were characterized during 2004 and 2005. The sites were located at two private dairy farms in Central New York on silt and gravelly silt loams (Aeric Endoaqualfs, Fluvaquentic Endoaquepts, Fluvaquentic Eutrudepts, Glossaquic Hapludalfs, and Glossic Hapludalfs). It was hypothesized that P availability (sodium acetate extractable-P) and soil-landscape variability would affect P release to the soil solution and shallow ground water. Results showed that P availability tended to be greater in crop fields relative to paired buffer plots. Soil P was a good indicator of soil solution dissolved (<0.45 microm) molybdate-reactive P (DRP) concentrations among plots, but was not independently effective at predicting ground water DRP concentrations. Mean ground water DRP in corn fields ranged from < or =20 to 80 microg L(-1), with lower concentrations in hay and buffer plots. More imperfectly drained crop fields and buffers tended to have greater average DRP, particulate (> or =0.45 microm) reactive P (PRP), and dissolved unreactive P (DUP) concentrations in ground water. Soil organic matter and 50-cm depth soil solution DRP in buffers jointly explained 75% of the average buffer ground water DRP variability. Results suggest that buffers were relatively effective at reducing soil solution and shallow ground water DRP concentrations, but their impact on particulate and organic P in ground water was less clear.

Allometric biomass equations for tree species used in agroforestry systems in Uganda

Estimates of above-ground biomass are required for better planning, sustainable management and monitoring of changes in carbon stocks in agroforestry systems. The objective of this study was to develop and compare biomass equations for Markhamia lutea, Casuarina equisetifolia, Maesopsis eminii and Grevillea robusta grown in a linear simultaneous agroforestry system in Uganda. These species were established in single rows in the middle of fields in 1995 from four-month old seedlings. A total of 57 trees were sampled for this study, 13 for M. lutea, 12 for C. equisetifolia, 16 for M. eminii and 16 for G. robusta. Biomass values of the various tree components (stem, branches and foliage) as well as the total above-ground biomass were fitted to linear and non-linear allometric models using total height, diameter-at-breast height (DBH), crown width as predictor variables. Although both DBH and height are typically used as independent variables for predicting above-ground biomass, the addition of height in biomass equations did not significantly improve model performance for M. eminii, M. lutea and G. robusta. However, addition of height significantly increased the proportion of variation explained in above-ground biomass for C. equisetifolia, while DBH did not significantly improve the prediction of biomass. The study confirmed the need for developing species-specific biomass equations.

Inter-laboratory variation in the chemical analysis of acidic forest soil reference samples from eastern North America

Long-term forest soil monitoring and research often requires a comparison of laboratory data generated at different times and in different laboratories. Quantifying the uncertainty associated with these analyses is necessary to assess temporal changes in soil properties. Forest soil chemical properties, and methods to measure these properties, often differ from agronomic and horticultural soils. Soil proficiency programs do not generally include forest soil samples that are highly acidic, high in extractable Al, low in extractable Ca and often high in carbon. To determine the uncertainty associated with specific analytical methods for forest soils, we collected and distributed samples from two soil horizons (Oa and Bs) to 15 laboratories in the eastern United States and Canada. Soil properties measured included total organic carbon and nitrogen, pH and exchangeable cations. Overall, results were consistent despite some differences in methodology. We calculated the median absolute deviation (MAD) for each measurement and considered the acceptable range to be the median ± 2.5 × MAD. Variability among laboratories was usually as low as the typical variability within a laboratory. A few areas of concern include a lack of consistency in the measurement and expression of results on a dry weight basis, relatively high variability in the C/N ratio in the Bs horizon, challenges associated with determining exchangeable cations at concentrations near the lower reporting range of some laboratories and the operationally defined nature of aluminum extractability. Recommendations include a continuation of reference forest soil exchange programs to quantify the uncertainty associated with these analyses in conjunction with ongoing efforts to review and standardize laboratory methods.

Soil CO2 effluxes, temporal and spatial variations, and root respiration in shrub willow biomass crops fields along a 19-year chronosequence as affected by regrowth and removal treatments.

In shrub willow biomass crop (SWBC) production systems, the soil CO2 efflux (Fc) component in the carbon cycle remains poorly understood. This study assesses (i) differences of Fc rates among the 5‐, 12‐, 14‐, and 19‐year‐old SWBCs with two treatments: continuous production (regrowth) willow fields that were harvested and allowed to regrow, and willow fields that were harvested, killed, and then stools and roots were ground into the soil (removal); (ii) temporal and spatial variations of Fc rates; (iii) root respiration contributions to total Fc; and (iv) climatic variables affecting Fc. During the growing season (May to September), Fc rates showed no statistically significant differences across different ages (P = 0.664), and between treatments (P = 0.351); however, there was an interaction between age and treatment (P = 0.001). Similarly, during the dormant season (October to April), Fc rates revealed no statistically significant differences across different ages (P = 0.305) and treatment interaction with age (P = 0.097). Fc rates differed significantly (P < 0.001) among different times of the day and times of the year. Fc rates, between 00 and 1059 h, between 1100 and 1659 h, and between 1700 and 2400 h displayed consistency from May to November; however, Fc rates in these three time intervals showed significant differences (P < 0.0001). In December, Fc rates remained constant over 24 h. Fc rates demonstrated higher temporal and spatial variations among willow age classes than between regrowth and removal treatments. Temporal and spatial variations of Fc were higher during the dormant season than during the growing season. The proportion of root respiration to total Fc ranged from 18 to 33% across age classes. Fc rates showed strong association with soil and air temperatures, and relative humidity.