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Roots are important to ecosystem nutrient pools and fluxes, but they are difficult to sample for tissue analysis, especially at depth. We analyzed patterns of nutrient concentrations in live roots up to 20 mm in diameter collected from quantitative soil pits in six northern hardwood sites at the Bartlett Experimental Forest, New Hampshire, USA. Root concentrations of nitrogen (N), phosphorus (P), calcium (Ca), and magnesium (Mg) were higher in the forest floor than in the mineral soil, by 23%-61% in fine roots (0-1 mm and 1-2 mm in diameter). Using only samples collected from the O horizon to characterize roots throughout the profile resulted in an average error across all elements of 16% in estimates of root nutrient contents. Within the mineral soil, there was little difference in root nutrient concentrations with depth. There were significant patterns with root diameter: N and Mg concentrations were highest in the finest roots, while Ca concentrations peaked in the 2-5 mm diameter class. One site (C8) differed from the others in having lower N but higher P, Ca, Mg, and potassium (K) concentrations in roots. In summary, analyzing roots by site and diameter class is more important to accurate nutrient accounting than is analyzing roots from depth in the mineral soil, but roots in the forest floor and the mineral soil differ dramatically for some elements. Key words: carbon, nitrogen, phosphorus, calcium, magnesium, potassium. Les racines jouent un role important dans les flux et les reserves de nutriments des ecosystemes, mais elles sont difficiles a echantillonner pour l'analyse de tissus, surtout en profondeur. Nous avons analyse les patrons de concentration des nutriments dans des racines vivantes d'un diametre allant jusqu'a 20 mm, prelevees dans des fosses d'observation quantitative etablies dans six stations de feuillus nordiques a la foret experimentale de Bartlett, dans l'Etat du New Hampshire, aux Etats-Unis. Les concentrations racinaires d'azote (N), de phosphore (P), de calcium (Ca) et de magnesium (Mg) etaient plus elevees dans la couverture morte que dans le sol mineral, de 23 a 61 % dans les racines fines (0-1 et 1-2 mm de diametre). Le fait d'utiliser seulement les echantillons preleves dans l'horizon O pour caracteriser les racines partout dans le profil a engendre une erreur moyenne pour l'ensemble des elements de 16 % dans les estimations de la teneur en nutriments des racines. Dans le sol mineral, il y avait peu de difference dans la concentration racinaire des nutriments selon la profondeur. Il y avait cependant des patrons significatifs selon le diametre des racines: les concentrations de N et Mg etaient plus elevees dans les plus petites racines, tandis que la concentration de Ca etait la plus elevee dans la classe de diametre de 2-5 mm. Une station (C8) se demarquait des autres par des concentrations racinaires plus faibles de N mais plus elevees de P, Ca, Mg et de potassium (K). En resume, pour obtenir une evaluation juste des nutriments il est plus important d'analyser les racines par station et classe de diametre qu'en fonction de la profondeur dans le sol mineral, mais les racines dans la couverture morte et le sol mineral different grandement dans le cas de certains elements. [Traduit par la Redaction] Mots-cles: carbone, azote, phosphore, calcium, magnesium, potassium., Introduction Roots are very difficult to sample for tissue analysis compared with aboveground vegetation (Fahey et al. 2017), but they make up an important portion of ecosystem nutrient contents and [...]

Leaf litterfall represents an important nutrient flux in forests, but separating leaves by species and collecting fresh litter annually for nutrient analysis is time-consuming and expensive. To quantify the sources of variation in litterfall nutrient estimates and guide optimal allocation of research effort, we analyzed nutrient concentration (5 years) and mass (6 years) of leaf litter for nine tree species in 13 northern hardwood sites. Coefficients of variation (CVs) in nutrient concentration were higher across sites than over time within sites for most elements; phosphorus was especially variable across sites (56% CV). Thus, to estimate litterfall nutrient fluxes accurately in forests of this type, nutrient analyses should be sitespecific as well as species-specific but may not need to be repeated annually (CVs over time averaged 17% for calcium, 21% for magnesium, 28% for potassium, and 32% for phosphorus concentration). Total leaf litterfall mass varied considerably from year to year, ranging from 234 to 370 g*m [sup-2] averaged over 13 sites. We recommend that litter collectors be elevated above the ground to avoid oversampling during extreme wind events. Use of species-specific allometric equations, or even basal area, to estimate the species composition of total litter mass may obviate the need to sort litter by species. Resume: La chute de litiere de feuilles represente un flux important de nutriments dans les forets mais la separation des feuilles selon l'espece et la collecte annuelle de litiere fraiche pour analyser les nutriments coutent cher et prennent beaucoup de temps. Afin de quantifier les sources de variation des estimations des nutriments presents dans la chute de litiere et de favoriserune allocation optimale des efforts de recherche, nous avons analyse la concentration des nutriments (5 ans) et la masse de litiere de feuilles (6 ans) pour neufespeces d'arbres dans 13 stations de feuillus nordiques. Les coefficients de variation (CV) de la concentration des nutriments etaient plus eleves entre les stations qu'entre les annees dans une meme station pour la plupart des elements; le phosphore etait particulierement variable d'une station a l'autre (CV = 56%). Par consequent, pour estimer avec precision les flux de nutriments dans la chute de litiere de ce type de foret, l'analyse des nutriments devrait etre specifique a chaque station et a chaque espece mais n'a pas besoin d'etre repetee a chaque annee (le CV entre les annees atteignait en moyenne 17% pour la concentration de calcium, 21% pour le magnesium, 28% pour le potassium et 32% pour le phosphore). La masse totale de chute de litiere de feuilles variait considerablement d'annee en annee, allant en moyenne pour les 13 stations de 234 a 370 g*m [sup-2] Nous recommandons que les collecteurs de litiere soient sureleves par rapport au sol pour eviter de surechantillonner lors d'episodes de vents violents. L'utilisation d'equations allometriques propres a chaque espece, ou meme de la surface terriere, pour estimer la composition en espece de la masse totale de litiere peut eviter d'avoir a trier la litiere selon l'espece. [Traduit par la Redaction], Introduction The mass and nutrient content of leaf production and turnover are important for estimating net primary productivity and nutrient cycling budgets in forested ecosystems (Whittaker et al. 1979; Clark [...]

The aim of this study was to investigate the effects of reusable organic wastes on soil organisms, with a focus on changes in the soil food web. Bone meal, de-oiled cake, and oyster shell were applied at 5 t ha (1), and the abundance and biomass of soil organisms were measured at 4, 8, and 13 weeks after treatment in soil under eggplant cultivation. The abundance of microflora and fauna was higher in the soils treated with bone meal or de-oiled cake than in untreated soils, suggesting that soil organisms are affected by the quality of applied organic wastes. Increases in the abundance of bacterivorous nematodes were observed under treatment with bone meal or de-oiled cake, but there was little change in the abundance of predatory nematodes. A positive response of microarthropods in the Collembola and Oribatida was apparent, and these organisms are involved as secondary consumers in the soil food web, but the predaceous Gamasida were relatively unaffected. The abundance of protozoa, microbivorous nematodes, Collembola, and Oribatida was correlated with the abundance of bacteria and fungi, indicating that both bacteria- and fungi-based food webs formed. The abundance of the secondary consumers was not significantly correlated with that of the predators. The study suggested that, in the short-term, organic waste alters the primary and secondary consumers but its effect may not extend to predators. Additional keywords: Collembola, decomposition, nematode, phospholipid fatty acid, Oribatida, recycling., Introduction The disposal of organic waste from households and the food industry results in both economic cost and environmental problems. Many organic wastes contain nutrients that can be reused for [...]

Apatite is ubiquitous in igneous, metamorphic, and sedimentary rocks, although usually in trace amounts. Apatite is the primary source of P and, due to its relatively rapid dissolution rate, can be an important Ca source in noncarbonate soils. We investigated the distribution of apatite using a 1 tool [L.sup.-1] HN[O.sub.3] extraction of glacial till soils at 31 sites across the northeastern United States. Parent materials formed from crystalline silicate and clastic sedimentary rocks contained 0.2 to 41 mmol Ca [kg.sup.-1] soil and 1 to 27 mmol P [kg.sup.-1] soil; at most of these sites, the P/Ca ratio was approximately 3:5, indicating the dominance of apatite. Parent materials underlain by carbonate rocks had 3 to 16 mmol P [kg.sup.-1] soil, similar to the noncarbonate groups, but had large concentrations of easily weathered Ca (56-1890 mmol [kg.sup.-1] soil) due to the extraction of carbonates. The same extraction procedure applied to samples from the upper 30 cm of mineral soil at the same sites showed lower concentrations of both Ca and P than in the C horizon, except for a few sites where the upper soil layers probably developed in different parent materials than the current C horizon. We also measured neutral-salt-exchangeable Ca concentrations in the 10- to 20-cm depth increment. Exchangeable Ca concentrations in soils underlain by carbonate bedrock were an order of magnitude higher than in soils underlain by crystalline silicate and elastic sedimentary rocks. For this reason, the exchangeable Ca concentration in the tipper soil was correlated to the concentration of 1 tool [L.sup.-1] HN[O.sub.3] extractable Ca in the underlying soil parent material. To predict concentrations of apatite in parent materials and the concentrations of exchangeable Ca in overlying horizons in greater detail would require more specific characterization of bedrock sources.

Measuring root biomass is time consuming and prone to sampling error. We compared three different methods of measuring root biomass in six northern hardwood stands at the Bartlett Experimental Forest. We found that root coring, the most common method of root sampling, yields estimates of fine root biomass about 27% greater than the estimates based on roots sampled in soil pits. Soil compaction contributes about 10% to this difference; the other contributing factor is that cores cannot be taken through obstructions such as rocks and coarse roots. Pits are the only method allowing characterization of root distribution by depth in rocky soil. If the depth and diameter distribution of roots are not required, allometric equations, if available, provide the easiest method of estimating total root biomass. Equations developed at the nearby Hubbard Brook Experimental Forest predicted root mass measured in soil pits with a mean absolute error of 32%. Allometric equations systematically underpredicted observed soil pit root mass in the young stands, presumably because of mature root systems remaining from the previous cohort, and systematically overpredicted observed root mass in the oldest stands. Soil pits can accurately characterize roots up to about 2 cm; coarser roots are encountered too rarely to be estimated by this method. Soil cores sample only fine roots (up to 1-2-mm diameter) but are much less work than excavating soil pits. Root mass estimates made using cores are more accurate if larger diameter corers are used (5 cm rather than 2.5 cm); subsampling before picking roots can help to control labor costs in the face of larger sample sizes. Abbreviations: dbh, diameter at breast height.

Current understanding of litterfall and fine root dynamics in temperate forests is limited, even though these are the major contributors to carbon and nutrient cycling in the ecosystems. In this study, we investigated litterfall and fine root biomass and production in five deciduous and four coniferous forests at the Gwangneung Experimental Forest in Korea. We used ingrowth cores to measure fine root production and root turnover rate. The litterfall was separated into leaves, twigs, and others, and then leaves were further separated according to species. Annual litterfall mass was not significantly different between the years, 360 to 651 g m-2 in 2011 and 300 to 656 g m-2 in 2012. Annual fine root (<5 mm) production was significantly higher in 2012 (421 to 1342 g m-2) than in 2011 (99 to 872 g m-2). Annual litterfall mass was significantly different among the stands, while fine root production did not statistically differ among the stands. The average fine root turnover rate, calculated by dividing the annual fine root production by the maximum standing fine root biomass, was 1.65 for deciduous forests and 1.97 for coniferous forests. Fine root production constituted 18–44% of NPP, where NPP was the sum of woody biomass production, litterfall production, and fine root production. Belowground production was a greater fraction of NPP in more productive forests suggesting their greater carbon allocation belowground. [ABSTRACT FROM AUTHOR]