Contribution of winter processes to soil nitrogen flux in taiga forest ecosystems

We measured annual net nitrogen (N) mineralization, nitrification, and amino acid production in situ across a primary successional sequence in interior Alaska, USA. Net N mineralization per gram dry soil increased across the successional sequence, but with a sharp decline in the oldest stage (black spruce). Net N mineralization expressed per gram soil organic matter exhibited the opposite pattern, suggesting that soil organic matter quality decreases significantly across succession. Net N mineralization rates during the growing season from green-up (early May) through freeze-up (late September–early October) accounted for approximately 60% of the annual inorganic N flux, whereas the remaining N was released during the apparent dormant season. Nitrogen release during winter occurred primarily during October–January with only negligible N mineralization during early spring in stands of willow, alder, balsam poplar and white spruce. By contrast, black spruce stands exhibited substantial mineralization after snow melt during early spring. The high rates of N mineralization in late autumn through early winter coincide with high turnover of fine root biomass in these stands, suggesting that labile substrate production, rather than temperature, is a major controlling factor over N release in these ecosystems. We suggest that the convention of restricting measurements of soil processes to the growing season greatly underestimate annual flux rates of inorganic nitrogen in these high-latitude ecosystems.     

Microtopography enhances nitrogen cycling and removal in created mitigation wetlands

Natural wetlands often have a heterogeneous soil surface topography, or microtopography (MT), that creates microsites of variable hydrology, vegetation, and soil biogeochemistry. Created mitigation wetlands are designed to mimic natural wetlands in structure and function, and recent mitigation projects have incorporated MT as one way to attain this goal. Microtopography may influence nitrogen (N) cycling in wetlands by providing adjacent areas of aerobic and anaerobic conditions and by increasing carbon storage, which together facilitate N cycling and removal. This study investigated three created wetlands in the Virginia Piedmont that incorporated disking-induced MT during construction. One site had paired disked and undisked plots, allowing an evaluation of the effects of this design feature on N flux rates. Microtopography was measured using conventional survey equipment along a 1-m circular transect and was described using two indices: tortuosity (T), describing soil surface roughness and relief, and limiting elevation difference (LD), describing soil surface relief. Ammonification, nitrification, and net N mineralization were determined with in situ incubation of modified ion-exchange resin cores and denitrification potential was determined using denitrification enzyme assay (DEA). Results demonstrated that disked plots had significantly greater LD than undisked plots one year after construction. Autogenic sources of MT (e.g. tussock-forming vegetation) in concert with variable hydrology and sedimentation maintained and in some cases enhanced MT in study wetlands. Tortuosity and LD values remained the same in one wetland when compared over a two-year period, suggesting a dynamic equilibrium of MT-forming and -eroding processes at play. Microtopography values also increased when comparing the original induced MT of a one-year old wetland with MT of older created wetlands (five and eight years old) with disking-induced MT, indicating that MT can increase by natural processes over time. When examined along a hydrologic gradient, LD increased with proximity to an overflow point as a result of differential sediment deposition and erosion during flood events. Nitrification increased with T and denitrification potential increased with LD, indicating that microtopographic heterogeneity enhances coupled N fluxes. The resulting N flux patterns may be explained by the increase in oxygen availability elicited by greater T (enhancing nitrification) and by the adjacent zones of aerobic and anaerobic conditions elicited by greater LD (enhancing coupled nitrification and denitrification potential). Findings of this study support the incorporation of MT into the design and regulatory evaluation of created wetlands in order to enhance N cycling and removal.     

Successional changes in soil nitrogen availability,non-symbiotic nitrogen fixation and carbon/nitrogen ratios in southern Chilean forest ecosystems

Vast areas of southern Chile are now covered by second-growth forests because of fire and logging. To study successional patterns after moderate-intensity, anthropogenic fire disturbance, we assessed differences in soil properties and N fluxes across a chronosequence of seven successional stands (2–130 years old). We examined current predictions of successional theory concerning changes in the N cycle in forest ecosystems. Seasonal fluctuations of net N mineralization (N_min) in surface soil and N availability (N_a; N_a=NH ₄ ⁺ –N+NO ₃ ^– –N) in upper and deep soil horizons were positively correlated with monthly precipitation. In accordance with theoretical predictions, stand age was positively, but weakly related to both N_a (r ²=0.282, P<0.001) and total N (N_tot; r ²=0.192, P<0.01), and negatively related to soil C/N ratios (r ²=0.187, P<0.01) in surface soils. A weak linear increase in soil N_min (upper plus deep soil horizons) was found across the chronosequence (r ²=0.124, P<0.022). N_min occurred at modest rates in early successional stands, suggesting that soil disturbance did not impair microbial processes. The relationship between N fixation (N_fix) in the litter layer and stand age best fitted a quadratic model (r ²=0.228, P<0.01). In contrast to documented successional trends for most temperate, tropical and Mediterranean forests, non-symbiotic N_fix in the litter layer is a steady N input to unpolluted southern temperate forests during mid and late succession, which may compensate for hydrological losses of organic N from old-growth ecosystems.     

Stoichiometry of biological nitrogen transformations in wetlands and other ecosystems

The stoichiometric equations of ammonification, nitrification and denitrification have demonstrated that the nitrogen cycle in nature is rather complicated. The mechanisms of biological nitrogen transformations are very important for analysis, design, operation and optimal control of natural ecosystems or engineered systems for nitrogen removal, and accurate stoichiometric equations can help in the maintenance of these environments. In this study, the new stoichiometric equations of intermediate nitrification, and heterotrophic and autotrophic denitrification with sulfur as the electron donor have been developed and discussed. The parameter values of f(s) (the fraction of electron donor coupled to cell synthesis) in stoichiometric equations of nitrification and denitrification are calculated according to experimental results implied in previously reported stoichiometric equations. Some new stoichiometric relationships of nitrification and denitrification, such as the O(2) demand for nitrifications, chemical oxygen demand/N ratios and the yield coefficients for denitrifications have been established. The pathway steps of nitrification and denitrification have been discussed.     

Interspecies differences in the preference of ammonium and nitrate in vascular plants

Three solution experiments were performed to test the importance of NH ₄ ⁺ versus NO ₃ ^- +NH ₄ ⁺ to growth of 23 wild-forest and open-land species, using field-relevant soil solution concentrations at pH 4.5. At N concentrations of 1–200 M growth increased with increasing N supply in Carex pilulifera, Deschampsia flexuosa, Elymus caninus and Bromus benekenii. Geum urbanum was the most N demanding species and had little growth below 200 M. The preference for NH ₄ ⁺ or NO ₃ ^- +NH ₄ ⁺ was tested also at pH 4.0; no antagonism was found between NH ₄ ⁺ and H⁺, as indicated by similar relative growth in both of the N treatments at both pH levels. Growth in solution with NH ₄ ⁺ relative to NO ₃ ^- +NH ₄ ⁺ , 200 M, was negatively related to the mean pH of the field occurrence of the species tested; acid-tolerant species grew equally well with only NH ₄ ⁺ as with NO ₃ ^- +NH ₄ ⁺ (Oxalis acetosella, Carex pilulifera, Festuca gigantea, Poa nemoralis, Deschampsia flexuosa, Stellaria holostea, Rumex acetosella), while species of less acid soils were favoured by NO ₃ ^- +NH ₄ ⁺ (Urtica dioica, Ficaria verna, Melandrium rubrum, Aegopodium podagraria, Geum urbanum, Bromus benekenii, Sanguisorba minor, Melica ciliata, Silene rupestris, Viscaria vulgaris, Plantago lanceolata). Intermediate species were Convallaria majalis, Elymus caninus, Hordelymus europaeus and Milium effusum. No antagonism between NH ₄ ⁺ and Ca²⁺, Mg²⁺ and K⁺ was indicated by the total uptake of the elements during the experiment.     

Seasonal rate of nitrate reduction in two temperate forest soils

Rainfall and throughfall chemistry beneath Sitka spruce of four ages were determined for a one year period. Throughfall beneath the older stands was consistently much more acid than rainfall. The H-ion flux was more than twice that in rainfall. Throughfall beneath the younger stands was only slightly more acid than rainfall, but the throughfall H-ion flux was considerbly less than in rainfall because the canopy intercepted a large proportion of rainfall. Concentrations and fluxes of other major cations and anions were greater in throughfall than precipitation for all crop ages.     

A comparative kinetic analysis of nitrate and ammonium influx in two early-successional tree species of temperate and boreal forest ecosystems

Root NO₃ ^? and NH₄ ⁺ influx systems of two early‐successional species of temperate (trembling aspen: Populus tremuloides Michx.) and boreal (lodgepole pine: Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest ecosystems were characterized. NO₃ ^? and NH₄ ⁺ influxes were biphasic, consisting of saturable high‐affinity (HATS) and constitutive non‐saturable low‐affinity transport systems (LATS) that were evident at low and relatively high N concentrations, respectively. NO₃ ^? influx via HATS was inducible (IHATS); nitrate pre‐treatment resulted in 8–10‐fold increases in the V_max for influx in both species. By contrast, HATS for NH₄ ⁺ were entirely constitutive. In both species, V_max values for NH₄ ⁺ influx were higher than those for NO₃ ^? uptake; the differences were larger in pine (6‐fold) than aspen (1·8‐fold). In aspen, the K_m for NH₄ ⁺ influx by HATS was approximately 3‐fold higher than for IHATS NO₃ ^? influx, while in pine the K_m for IHATS NO₃ ^? influx was approximately 3‐fold higher than for NH₄ ⁺ influx. The aspen IHATS for NO₃ ^? influx appeared to be more efficient than that of pine (V_max values for aspen being approximately 10‐fold higher and K_m values being approximately 13‐fold lower than for pine). By contrast, only small differences in values for the NH₄ ⁺ HATS were evident between the two species. The kinetic parameters observed here probably result from adaptations to the N availabilities in their respective natural habitats; these may contribute to the distribution and niche separation of these species.     

Presence of Nitrosospira cluster 2 bacteria corresponds to N transformation rates in nine acid Scots pine forest soils

The relation between environmental factors and the presence of ammonia-oxidising bacteria (AOB), and its consequences for the N transformation rates were investigated in nine Scots pine (Pinus sylvestris L.) forest soils. In general, the diversity in AOB appears to be strikingly low compared to other ecosystems. Nitrosospira cluster 2, as determined by temporal temperature gradient electrophoresis and sequencing, was the only sequence cluster detected in the five soils with high nitrification rates. In the four soils with low nitrification rates, AOB-like sequences could not be detected. Differences in nitrification rates between the forest soils correlated to soil C/N ratio (or total N) and atmospheric N deposition.     

Methane uptake rates in Japanese forest soils depend on the oxidation ability of topsoil, with a new estimate for global methane uptake in temperate forest

To clarify the reason for the higher CH₄ uptake rate in Japanese forest soils, twenty-seven sites were established for CH₄ flux measurement. The first order rate constant for CH₄ uptake was also determined using soil core incubation at 14 sites. The CH₄ uptake rate had a seasonal fluctuation, high in summer and low in winter, and the rate correlated with soil temperature at 17 sites. The annual CH₄ uptake rates ranged from 2.7 to 24.8 kg CH₄ ha⁻¹ y⁻¹ (the average of these rates was 9.7 or 10.9 kg CH₄ ha⁻¹ y⁻¹, depending on method of calculation), which is somewhat higher than the uptake rates reported in previous literature. The averaged CH₄ uptake rate correlated closely with the CH₄ oxidation rate of the topsoil (0–5 cm) in the study sites. The CH₄ oxidation constant of the topsoil was explained by a multiple regression model using total pore volume of the soil, nitrate content, and C/N ratio (p < 0.05, R ² = 0.684). This result and comparison with literature data suggest that the high CH₄ uptake rate in Japanese forest soils depends on the high porosity probably due to volcanic ash parent materials. According to our review of the literature, the CH₄ uptake rate in temperate forests in Europe is significantly different from that in Asia and North America. A new global CH₄ uptake rate in temperate forests was estimated to be 5.4 Tg y⁻¹ (1 SE is 1.1 Tg y⁻¹) on a continental basis.     

Soil nitrogen dynamics in a holm oak forest

Soil nitrogen (N) dynamics were studied in a dense, holm oak (Quercus ilex ssp. ilex) stand in the Montseny mountains to determine annual and seasonal patterns of N availability and uptake in an undisturbed Mediterranean forest on acidic soil. Soil mineral N content, net N mineralization (NNM), and net nitrification (NN) were determined by monthly sampling at two soil depths followed by in situ incubation in polyethylene bags. NNM per unit of soil mass was much higher at 0–5 cm than at 5–20 cm (annual means 24 and 2.5 mg N/kg, respectively) but on an area basis NNM was similar at both depths. A total of 80 kg N/ha/yr were mineralized from the first 20 cm of soil. NN amounted to only 9% of the annual NNM (7.5 kg N/ha/yr) and it occurred only in the upper 5 cm. NNM was maximum in June and July, while the NN peaked in May. Despite favourable soil temperature and moisture, NNM was negative in autumn because of microbial immobilization. Seasonal and depth variations of NNM appeared to be controlled more by substrate quality than by organic matter quantity, temperature or moisture. NN was not limited by ammonium availability. Calculated N uptake amounted to 91 kg/ha yr, peaking in June and July. The investigated stand showed a moderately high N availability, but ammonium was the major form of mineral N supply for holm oak.     

Nitrogen uptake and regeneration (ammonium regeneration,nitrification and photoproduction) in waters of the West Florida Shelf prone to blooms of Karenia brevis

The West Florida Shelf (WFS) encompasses a range of environments from inshore estuarine to offshore oligotrophic waters, which are frequently the site of large and persistent blooms of the toxic dinoflagellate, Karenia brevis. The goals of this study were to characterize the nitrogen (N) nutrition of plankton across the range of environmental conditions on the WFS, to quantify the percentage of the plankton N demand met through in situ N regeneration, and to determine whether planktonic N nutrition changes when high concentrations of Karenia are present. In the fall of 2007, 2008, and 2009 we measured ambient nutrient concentrations and used stable isotope techniques to measure rates of primary production and uptake rates of inorganic N (ammonium, NH₄⁺, and nitrate, NO₃⁻), and organic N and carbon (C; urea and amino acids, AA) in estuarine, coastal, and offshore waters, as well as coastal sites with Karenia blooms present. In parallel, we also measured rates of in situ N regeneration – NH₄⁺ regeneration, nitrification, and photoproduction of NH₄⁺, nitrite and AA. Based on microscope observations, ancillary measurements, and previous monitoring history, Karenia blooms sampled represented three bloom stages – initiation in 2008, maintenance in 2007, and late maintenance/stationary phase in 2009. Nutrient concentrations were highest at estuarine sampling sites and lowest at offshore sites. Uptake of NH₄⁺ and NO₃⁻ provided the largest contribution to N nutrition at all sites. At the non-Karenia sites, in situ rates of NH₄⁺ regeneration and nitrification were generally sufficient to supply these substrates equal to the rates at which they were taken up. At Karenia sites, NO₃⁻ was the most important N substrate during the initiation phase, while NH₄⁺ was the most important N form used during bloom maintenance and stationary phases. Rates of NH₄⁺ regeneration were high but insufficient (85 ± 36% of uptake) to support the measured NH₄⁺ uptake at all the Karenia sites although nitrification rates far exceeded uptake rates of NO₃⁻. Taken together our results support the “no smoking gun” nutrient hypothesis that there is no single nutrient source or strategy that can explain Karenia's frequent dominance in the waters where it occurs. Consistent with other papers in this volume, our results indicate that Karenia can utilize an array of inorganic and organic N forms from a number of N sources.     

The insect assemblage in water filled tree-holes in a European temperate deciduous forest: community composition reflects structural,trophic and physicochemical factors

(1) A study of the metazoan community occurring in water-filled tree-holes in southern Germany has been performed to determine the relationships among the key species of arthropods found within the community and a range of structural, physical and chemical factors, using multivariate techniques. (2) Four animal species were sufficiently common to allow identification of the preferred environments for their larvae. The aedine mosquito, Aedes geniculatus, prefers shallow open tree-holes with relatively little leaf litter even though these may represent less permanent water-bodies. The scirtid beetle, Prionocyhon serricornis, occurs in larger, deeper holes with greater amounts of leaf litter and a more predictable aquatic environment, although open water is not a requisite. Larvae of the orthocladiine chironomid, Metriocnemus cavicola, favours shallow more open tree-holes with higher litter content but with sufficient open water to ensure an adequate oxygen supply. The eristaline syrphid, Myatropa florea, favours shallow, open tree-holes with low litter content. (3) There is no evidence that interspecific interactions affect the distribution or abundance of any of these species. (4) The autecological results are discussed in light of those available for phytotelm dwellers elsewhere. The food-web overall may be interpreted as so simple that it is driven by ‘bottom-up’ environmental factors with no part played by those community-level ‘top-down’ processes that may be adduced for more complex, multi-trophic level webs occurring elsewhere. No “processing chain commensalism” could be found in the arthropod community of the temperate German deciduous tree-hole dwellers. Handling editor: K. Martens     

Nitrate reductase activity and growth response of forest species to ammonium and nitrate sources of nitrogen

Summary Three tree species,Eucalyptus regnans (F. Muell.),E. obliqua (L'Herit.),Pinus radiata (D. Don) were grown in sand culture with different proportions of nitrate and ammonium. Nitrate Reductase Activity (NRA) was induced in root tissue of all species and in leaf tissue of the eucalypts. An increasing proportion of nitrate resulted in increasing NRA in all species and hence NRA alone is no indication of N-preference. The highest NRA was found withE. regnans, a result which has also been obtained in the mature forest. The growth ofE. regnans was least with NH₄ ⁺ alone, whereas that ofE. obliqua was least with NO₃ ^– alone. The soils of matureE. regnans forest have a high potential for nitrification while those ofE. obliqua forest show little nitrification. Thus the preference for particular N sources shown by seedlings in culture is supported by related properties of mature forests. It is postulated however, that the inducibility of a high level of RNA in seedlings is more likely a result of a preference for NO₃ ^– than a cause.     

Urbanization and fragmentation have opposing effects on soil nitrogen availability in temperate forest ecosystems

Nitrogen (N) availability relative to plant demand has been declining in recent years in terrestrial ecosystems throughout the world, a phenomenon known as N oligotrophication. The temperate forests of the northeastern U.S. have experienced a particularly steep decline in bioavailable N, which is expected to be exacerbated by climate change. This region has also experienced rapid urban expansion in recent decades that leads to forest fragmentation, and it is unknown whether and how these changes affect N availability and uptake by forest trees. Many studies have examined the impact of either urbanization or forest fragmentation on nitrogen (N) cycling, but none to our knowledge have focused on the combined effects of these co-occurring environmental changes. We examined the effects of urbanization and fragmentation on oak-dominated (Quercus spp.) forests along an urban to rural gradient from Boston to central Massachusetts (MA). At eight study sites along the urbanization gradient, plant and soil measurements were made along a 90 m transect from a developed edge to an intact forest interior. Rates of net ammonification, net mineralization, and foliar N concentrations were significantly higher in urban than rural sites, while net nitrification and foliar C:N were not different between urban and rural forests. At urban sites, foliar N and net ammonification and mineralization were higher at forest interiors compared to edges, while net nitrification and foliar C:N were higher at rural forest edges than interiors. These results indicate that urban forests in the northeastern U.S. have greater soil N availability and N uptake by trees compared to rural forests, counteracting the trend for widespread N oligotrophication in temperate forests around the globe. Such increases in available N are diminished at forest edges, however, demonstrating that forest fragmentation has the opposite effect of urbanization on coupled N availability and demand by trees.     

Response of coastal phytoplankton to ammonium and nitrate pulses: seasonal variations of nitrogen uptake and regeneration

Seasonal variation in uptake and regeneration of ammonium and nitrate in a coastal lagoon was studied using ¹⁵N incorporation in particulate matter and by measuring changes in particulate nitrogen. Uptake and regeneration rates were two orders of magnitude lower in winter than in summer. Summer uptake values were 2.8 and 2.2 mol N.l^–1.d^–1 for ammonium and nitrate, respectively. Regeneration rates were 2.9 and 2.1 mol N.l^–1.d^–1 for ammonium and nitrate respectively. Regeneration/uptake ratios were often below one, indicating that water column processes were not sufficient to satisfy the phytoplankton nitrogen demand. This implies a role of other sources of nitrogen, such as macrofauna (oysters and epibionts) and sediment. Phytoplankton was well adapted to the seasonal variations in resources, with mixotrophic dinoflagellates dominant in winter, and fast growing diatoms in summer. In winter and spring, ammonium was clearly preferred to nitrate as a nitrogen source, but nitrate was an important nitrogen source in summer because of high nitrification rates. Despite low nutrient levels, the high rates of nitrogen regeneration in summer as well as the simultaneous uptake of nitrate and ammonium allow high phytoplankton growth rates which in turn enable high oyster production.     

Plant macro-remains from a rock shelter in the temperate forests of southern Chile

The study of plant macro-remains from archaeological sites provides substantial information on the activities occurring in a settlement and living conditions during its occupation. This article reports the plant macro-remains (charred seeds and wood charcoal) recovered from a rock shelter in the temperate forests of southern Chile (Latitude 39°S). The main goal of the study was to assess the potential of these remains to indicate collection, use and consumption of plant resources available in this ecosystem by hunter-gatherer groups during the Holocene. Remains from three cultural periods were collected using wet sieving and flotation techniques. Macro-botanical remains found in the rock shelter represented a variety of native trees, shrubs and herbs, both native and introduced. Charred seeds included 19 plant taxa, divided into three groups according to their source: collected foods, including pulses (1 species) and grains (3 taxa, 1 probably cultivated); seeds introduced with food items, including fruit stones and nutshells from several native shrubs and trees; seeds introduced with non-food items, mainly from tree species with no evident use. Wood charcoal fragments represented 28 different native taxa (26 dicotyledons, 1 monocotyledon and 1 gymnosperm), none with a specific identifiable use. Analysis of seed remains indicated the use of grains and, to some extent, collection of fruits and nuts over summer and autumn. The analysis of dispersed charcoal fragments and those accumulated in hearths were especially useful to describe the vegetation surrounding the rock shelter, infer successional events, and identify taxa undetectable in the seed record.     

五种温带森林土壤微生物生物量碳氮的时空格局

土壤微生物是森林生态系统中的重要分解者,在碳和氮循环中起着重要作用,同时也是对环境变化的敏感指示者。采用氯仿熏蒸浸提法测定了我国东北地区5种温带森林土壤微生物生物量碳(Cmic)和氮(Nmic)的季节动态及其在土壤中的垂直变化。结果表明:林型之间Cmic和Nmic差异显著(P0.01)。落叶松林、红松林、蒙古栎林、杨桦林、硬阔叶林的Cmic的变化范围依次为:278937mgkg-1、2181020mgkg-1、313891mgkg-1、5101092mgkg-1、4401911mgkg-1;其Nmic的变化范围依次为:1872mgkg-1、18103mgkg-1、2495mgkg-1、43125mgkg-1、40208mgkg-1。所有林型的Cmic和Nmic均随土壤深度的增加而下降。Cmic和Nmic基本上呈现出生长季开始之前下降、生长季结束时上升、其中出现12个峰值的季节变化格局,但峰值大小和出现时间随林型和土壤层次而变。010cm土层的Cmic和Nmic季节变化较大。Cmic和Nmic与凋落叶量、土壤有机碳含量和土壤总氮含量呈显著正相关。Cmic与土壤含水量呈正相关,而与土壤温度呈负相关。不同林型凋落物数量和组成、土壤理化性质的差异是导致其土壤微生物生物量时空格局差异的主要因素。     

Exploring the functional significance of forest diversity: A new long-term experiment with temperate tree species (BIOTREE)

Effects of biodiversity on ecosystem functioning have been mainly studied in experiments that artificially create gradients in grassland plant diversity. Woody species were largely excluded from these early experiments, despite the ecological and socioeconomic importance of forest ecosystems. We discuss conceptual aspects of mechanistically driven research on the biodiversity–ecosystem functioning relationship in forests, including the comparison of scientific approaches like ‘observational studies’, ‘removal experiments’, and ‘synthetic-assemblage experiments’. We give a short overview on the differences between herbaceous and forest ecosystems, focusing on canopy characteristics, and the possibilities for individual versus population-based investigations.We present detailed information about the first large-scale, multisite and long-term biodiversity–ecosystem functioning experiment with tree species of temperate forests (BIOTREE – BIOdiversity and ecosystem processes in experimental TREE stands). At three sites of differing geology and local climate, we planted 200,000 saplings on a total area of 70 ha. At two sites, diversity gradients were established by varying the number of tree species (BIOTREE-SPECIES). At a third site, only functional diversity at a constant level of tree species richness was manipulated by selecting mixtures that differ in the functional trait values of the corresponding species (BIOTREE-FD). Additional experimental treatments at the subplot level include silvicultural management options, the addition of subdominant species, and the reduction of genetic diversity. Response variables focus on productivity, biogeochemical cycles and carbon sequestration, and resource use complementarity.We explore the use of different measures of functional diversity for a posteriori classifications of functional richness and their use in the analysis of our tree diversity experiment. The experiment is thought to provide a long-term research platform for a variety of scientific questions related to forest biodiversity and ecosystem processes.