Wet Sites Research Articles

Florida’s fiery subtropical grasslands: Growth forms, belowground organs, and post-fire recovery strategies

Fire-adaptive traits in plants of tropical and subtropical grassy ecosystems have been the subject of considerable global research, but only recently studied in pyrogenic Florida subtropical grasslands. Plant growth forms, belowground organs, and post-fire recovery strategies were studied for 198 grassland specialists in peninsular Florida. Community types (dry-mesic, mesic, wet-mesic, and wet) were sampled with 1m2 plots along the edaphic-hydrologic gradient and the association between these variables and fire-related plant traits was tested using fourth-corner analysis. Caulescent herbs (43), cespitose graminoids (27), and rosette herbs (31) are the most common growth forms among species sampled. Plants with epigeogenous and hypogeogenous rhizomes dominate the sample plots, including matrix graminoids, shrub geoxyles, and an acaulescent rhizomatous fire-resilient palm (Serenoa repens). Most species (163; 82%) exhibit resprouting, including 30 facultative resprouters and 133 obligate resprouters. All woody rhizomatous species are obligate resprouters, and 35 ephemeral herbaceous species are obligate reseeders. Community type was a better predictor of species abundances than hydrology, however, hydrology was significantly associated with species traits measured, particularly rhizome texture, with woody rhizomes prevalent in all but the wet sites. Belowground organs (xylopodia, geoxylic suffructices) and growth form were associated with frequent fire and phylogeny, suggesting fire regime as a driver of community phylogenetic diversity. Persistence, rapid resilience and co-occurrence of geoxyles align Florida subtropical grasslands with other global geoxyle grasslands. The old-growth, pyrogenic grassy ecosystems of peninsular Florida are the center of geoxyle diversification on the southeastern US coastal plain.

Abiotic correlates with diversity and distinctiveness in Sunshine Coast heathlands: Moisture, volcanic landscapes and patterned mounds

AbstractThe ongoing management and protection of conservation areas can be informed by understanding factors that affect the integrity of these communities. Abiotic factors associated with diversity and phylogenetic dispersion within communities, as well as distinctiveness between communities, may potentially be impacted by climate change or changes in hydrology due to urbanization. This study used a range of diversity metrics, along with nominal and quantitative abiotic data, to examine correlates with diversity patterns in the Sunshine Coast heathlands, ecosystems under threat from urban development. Metrics for 80 heathland sites over a variety of substrates, moisture levels and topographic factors were compared using univariate and multivariate statistics. Moisture is a key abiotic factor correlated with the diversity and distinctiveness of heath, and also with higher phylogenetic dispersion of moist and wet sites, indicating possible refuges. Vegetation composition patterns were distinct in the heaths on Tertiary and Triassic rocky volcanic substrates, with the overlapping composition of heath on other substrates, confirming the tolerance of many heath species to a variety of substrates. Patterned natural ‘mounds’ and ‘trenches’ were associated with phylogenetic evenness and are possible refugia. Multivariate analysis had a weak positive correlation of environmental factors with vegetation and phylogenetic composition, emphasizing the complexity of correlates with diversity for the heathlands. This study suggests that both the management of hydrological changes and protection of potential refugial areas are likely to be critical in maintaining the integrity and diversity of the Sunshine Coast heathlands.

Phyllosphere to Ferment: Site Conditions Structure Cacao Pod and Fermentation Microbiomes in Hawaiʻi

Microbial fermentation is crucial to the development of flavors in cacao-based products, but how the abiotic environment and pod surface microbiomes can contribute to these different sensory profiles is underdeveloped. To better understand the connections between environment, plant variety, associated pod phyllosphere microbiomes, and the fermentation microbiome, we characterized the fungi and bacteria on pod surfaces and early fermentations of two cacao varieties across wet and dry sites on the island of O‘ahu, Hawai‘i. We showed that site (and the environmental conditions linked to those sites) significantly influenced the microbiomes of both the pod phyllosphere and fermentations but did not significantly explain the differences between cacao varieties. Certain taxa of bacteria and fungi seemingly prefer the wet Kualoa Ranch site compared with the drier Urban Garden Center Site. Rare members of the pod phyllosphere communities became highly enriched during fermentation, where basidiomycetous yeasts ( Filobasidium sp., Hannaella zeae, Rhodotorula mucilaginosa, R. paludigena, and Sporobolomyces carnicolor) became dominant at the wet site, and both ascomycetous and basidiomycetous yeasts ( Hyphopichia burtonii, Meyerozyma sp., Yamadazyma phyllophila, Filobasidium sp., Kwoniella heveanensis, R. mucilaginosa, Sporobolomyces sp., and S. carnicolor) became dominant at the dry site. The agricultural production site where cacao plants are grown should be considered carefully because it is likely important in structuring microbes that are present on pod surfaces and the microbes (mostly yeasts) that will be carried forward into fermentation. These yeasts may contribute to the development of the unique fruity or floral flavors in chocolates produced in Hawai‘i. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

No effect of snow on shrub xylem traits: Insights from a snow-manipulation experiment on Disko Island, Greenland

Widespread shrubification across the Arctic has been generally attributed to increasing air temperatures, but responses vary across species and sites. Wood structures related to the plant hydraulic architecture may respond to local environmental conditions and potentially impact shrub growth, but these relationships remain understudied. Using methods of dendroanatomy, we analysed shrub ring width (RW) and xylem anatomical traits of 80 individuals of Salix glauca L. and Betula nana L. at a snow manipulation experiment in Western Greenland. We assessed how their responses differed between treatments (increased versus ambient snow depth) and soil moisture regimes (wet and dry). Despite an increase in snow depth due to snow fences (28–39 %), neither RW nor anatomical traits in either species showed significant responses to this increase. In contrast, irrespective of the snow treatment, the xylem specific hydraulic conductivity (Ks) and earlywood vessel size (LA95) for the study period were larger in S. glauca (p < 0.1, p < 0.01) and B. nana (p < 0.01, p < 0.001) at the wet than the dry site, while both species had larger vessel groups at the dry than the wet site (p < 0.01). RW of B. nana was higher at the wet site (p < 0.01), but no differences were observed for S. glauca. Additionally, B. nana Ks and LA95 showed different trends over the study period, with decreases observed at the dry site (p < 0.001), while for other responses no difference was observed. Our results indicate that, taking into account ontogenetic and allometric trends, hydraulic related xylem traits of both species, along with B. nana growth, were influenced by soil moisture. These findings suggest that soil moisture regime, but not snow cover, may determine xylem responses to future climate change and thus add to the heterogeneity of Arctic shrub dynamics, though more long-term species- and site- specific studies are needed.

Drivers of wood decay in tropical ecosystems: Termites versus microbes along spatial, temporal and experimental precipitation gradients

Abstract Models estimating decomposition rates of dead wood across space and time are mainly based on studies carried out in temperate zones where microbes are dominant drivers of decomposition. However, most dead wood biomass is found in tropical ecosystems, where termites are also important wood consumers. Given the dependence of microbial decomposition on moisture with termite decomposition thought to be more resilient to dry conditions, the relative importance of these decomposition agents is expected to shift along gradients in precipitation that affect wood moisture. Here, we investigated the relative roles of microbes and termites in wood decomposition across precipitation gradients in space, time and with a simulated drought experiment in tropical Australia. We deployed mesh bags with non‐native pine wood blocks, allowing termite access to half the bags. Bags were collected every 6 months (end of wet and dry seasons) over a 4‐year period across five sites along a rainfall gradient (ranging from savanna to wet sclerophyll to rainforest) and within a simulated drought experiment at the wettest site. We expected microbial decomposition to proceed faster in wet conditions with greater relative influence of termites in dry conditions. Consistent with expectations, microbial‐mediated wood decomposition was slowest in dry savanna sites, dry seasons and simulated drought conditions. Wood blocks discovered by termites decomposed 16–36% faster than blocks undiscovered by termites regardless of precipitation levels. Concurrently, termites were 10 times more likely to discover wood in dry savanna compared with wet rainforest sites, compensating for slow microbial decomposition in savannas. For wood discovered by termites, seasonality and drought did not significantly affect decomposition rates. Taken together, we found that spatial and seasonal variation in precipitation is important in shaping wood decomposition rates as driven by termites and microbes, although these different gradients do not equally impact decomposition agents. As we better understand how climate change will affect precipitation regimes across the tropics, our results can improve predictions of how wood decomposition agents will shift with potential for altering carbon fluxes. Read the free Plain Language Summary for this article on the Journal blog.

Restoring forest structure, biodiversity and ecosystem function in the West African humid tropics: secondary versus plantation forests

Deforestation and forest degradation in the tropics has resulted in the depletion of vital forest resources and services, the near eradication of suitable habitats for forest fauna and flora, and the impoverishment of human populations reliant on forest ecosystems. The rapid and concerning pace of deforestation in tropical regions calls for urgent and pragmatic steps to tackle the root causes and rehabilitate or restore degraded and deforested landscapes. The aim of the study was to evaluate the effectiveness of old, unmanaged forest plantations compared to similar-aged secondary forests in restoring forest stand structure, floristics and diversity of vascular plants, and important ecological functions with reference to neighbouring primary forests. In addition, timber value was estimated and compared among the three forest types. The research was conducted across 11 sites within Ghana's moist and wet climatic/forest zones. Systematic random sampling of 93 plots each measuring 20m × 20m with nested subplots measuring 5m x 5m for saplings and 2m x 2m for ground vegetation was undertaken. Forty-two years after establishment and/or abandonment, both the plantation and secondary forests showed structural attributes comparable to those of the primary forests. Nevertheless, the plantation recorded much higher bole volume and basal area compared to the secondary forests. The secondary, plantation and primary forests exhibited considerable overlap in terms of floral composition, with the presence of several rare and restricted-range species. A significant proportion of primary forest vascular plant species, namely 60% and 77%, were identified in the secondary and plantation forests, respectively. The diversity of plant species, as quantified by the Shannon-Wiener Diversity Index (H') and Simpson Index (S), showed no significant variation between primary (H'=3.07, S = 0.91) and secondary (H'=2.95, S = 0.87) or plantation (H'=2.85, S = 0.87) forests. Generally, the primary and secondary forests exhibited higher species richness than the plantations. The mean above-ground carbon stocks of the plantations (159.7 ± 14.3 Mg ha-1 ) was found to be similar to that of the primary forests (173.0 ± 25.1 Mg ha-1 ), but both were much higher than the secondary forests (103.4 ± 12.0 Mg ha-1 ). Soil pH levels in the wet sites were much lower, ranging from 4.2 to 4.6, compared to moist sites, which had pH levels ranging from 4.6 to 5.4. Soil physicochemical properties, carbon stocks, fertility, microbial activity, and litter decomposition measurements across the different forest types within the climatic zones were similar. Nevertheless, significant differences were observed between climatic zones. Contrary to results of earlier tropical studies, we observed higher litter decomposition rates in the moist compared to the wet zone, which experiences higher annual rainfall, especially for the recalcitrant carbon fraction of the litter. Relatedly, soil microbial biomass and microbial population were significantly greater in the moist compared to the wet zone. Mean soil carbon stocks (0 - 50 cm) was significantly higher in the wet (106.8 Mg ha-1 ) compared to the moist (56.9 Mg ha-1 ), with mean site values ranging from 51.16 Mg ha-1 to 122.84 Mg ha-1 . The mean timber stumpage value of plantations was $8577 per hectare, compared to primary and secondary forests, which were $3112 and $1870 per hectare, respectively. Tropical forest plantations established on long rotations under low-intensity management regimes, and secondary forests can evolve into forest systems that exhibit structural complexity, floristic diversity, ecological functionality, and self-sustainability, akin to primary forests. Such forest plantations and secondary forests constitute viable pathways for the restoration of deforested landscapes and climate change mitigation, while potentially providing landowners with moderate financial returns through selective timber harvesting.

The impact of drying on the structure and photosynthesis of boreal peatland vegetation

Boreal peatlands harbour large stores of carbon as peat below their surfaces. Climate change is expected to cause drying in northern peatlands, which will in turn impact the carbon balance of these ecosystems that is maintained by high water tables and the hydrologically sensitive plants growing there. This study aims to quantify how vegetation will be structured (I) and photosynthesize (II, III) in a future climate as emulated by long-term water level drawdown (WLD). To do this, changes in the vegetation and its photosynthesis after WLD are linked, and the response of Sphagnum mosses to periodic drought is investigated. Field measurements were done at a long-term WLD field experiment that contained a rich (mesotrophic) fen, a poor (oligotrophic) fen and a bog (ombrotrophic) site. Measurements included vegetation surveys from existing permanent sample plots and leaf-level carbon dioxide exchange measurements. For an experiment in controlled conditions peatland surface cores from this field experiment were transported to a greenhouse where the photosynthesis of lawn Sphagna during and after an experimental periodic drought was measured. The field study revealed that the response of peatland vegetation to WLD depend on peatland type. The species composition in the rich fen was the most impacted by WLD, while the bog vegetation demonstrated stability. Similarly, large increases in photosynthesis occurred following WLD on the vascular plant-covered rich fen, while changes were negligible on the Sphagnum-carpeted bog. The vegetation on the two fens shifted from an open sedge-, or sedge and Sphagnum-dominated ecosystem, to a tree-dominated ecosystem. Canopy development following WLD further accelerated vegetation changes by shading and sheltering the understorey vegetation. Vascular plants were the most likely to increase productivity from WLD as they are best suited to utilize the nutrients made available by peat mineralization, while Sphagnum moss photosynthesis was impacted little. The greenhouse study revealed that lawn Sphagnum mosses exposed to long-term WLD were more vulnerable to drought compared to those from wet sites. Large capitula typical to fen Sphagnum species appeared to be beneficial for surviving periodic drought. This work demonstrated that climate change as emulated by long-term WLD will have a large impact on the vegetation composition of northern peatlands and increase photosynthetic function of these ecosystems, fens in particular. To better predict climate feedbacks from these changes, carbon dynamics including peatland vegetation dynamics should be updated in global process models. Future research to better understand the tipping point of different peatland types after WLD in different climatic regions will help us to predict changes in these diverse and globally important systems.

Growth data of outlying plantations allows benchmarking the tolerance to climate extremes and drought stress in the European larch.

Plantations located outside the species distribution area represent natural experiments to assess tree tolerance to climate variability. Climate change amplifies warming-related drought stress but also leads to more climate extremes. We studied plantations of the European larch (Larix decidua), a conifer native to central and eastern Europe, in northern Spain. We used climate, drought and tree-ring data from four larch plantations including wet (Valgañón, site V; Santurde, site S), intermediate (Ribavellosa, site R) and dry (Santa Marina, site M) sites. We aimed to benchmark the larch tolerance to climate and drought stress by analysing the relationships between radial growth increment (hereafter growth), climate data (temperature, precipitation, radiation) and a drought index. Basal area increment (BAI) was the lowest in the driest site M (5.2 cm2 yr-1; period 1988-2022), followed by site R (7.5 cm2 yr-1), with the youngest and oldest and trees being planted in M (35 years) and R (150 years) sites. BAI peaked in the wettest sites (V; 10.4 cm2 yr-1; S, 10.8 cm2 yr-1). We detected a sharp BAI reduction (30% of the regional mean) in 2001 when springto-summer conditions were very dry. In the wettest V and S sites, larch growth positively responded to current March and June-July radiation, but negatively to March precipitation. In the R site, high April precipitation enhanced growth. In the driest M site, warm conditions in the late prior winter and current spring improved growth, but warm-sunny conditions in July and dry-sunny conditions in August reduced it. Larch growth positively responded to spring-summer wet conditions considering short (1-6 months) and long (9-24 months) time scales in dry (site M) and wet-intermediate (sites S and R) sites, respectively. Larch growth is vulnerable to drought stress in dry slow-growing plantations, but also to extreme spring wet-cloudy events followed by dry-hot conditions in wet fast-growing plantations.

The alien Chinese windmill palm (Trachycarpus fortunei) impacts forest vegetation and regeneration on the southern slope of the European Alps

AbstractQuestionsDoes the non‐native evergreen Chinese windmill palm (Trachycarpus fortunei) affect native plant community and forest regeneration in deciduous forests? Are effects modulated by soil moisture? What are the implications for forest management and nature conservation?LocationBroadleaved deciduous low‐elevation forests on the southern slope of the Alps across the Swiss–Italian border region.MethodsWe compared the native herbaceous and woody plant composition, species richness, Shannon diversity and abundance at ten deciduous forest sites on two moisture conditions (six mesic–moist sites and four mesic–dry sites). Each site consisted of three plots measuring 400 m2 along a gradient of T. fortunei presence, ranging from “dominant”, to “present but not dominant” to “absent”.ResultsIn mesic–moist forests with high densities of T. fortunei, species richness and Shannon diversity of native plants and recruiting woody species in the herb and shrub layers were significantly reduced compared to similar sites where T. fortunei is absent or not dominant. However, in mesic–dry forests these variables did not differ between palm‐invaded and uninvaded plots. The abundance of recruiting woody individuals did not differ between plots invaded by palms and uninvaded control plots in either forest type.ConclusionsWe expect detrimental consequences for plant diversity in mesic–moist alluvial forests with high T. fortunei densities and few detrimental consequences in the more widespread non‐alluvial forests. We recommend multifaceted management, including targeted eradication in alluvial forests identified as hotspots of native plant diversity, accompanied by hands‐off management of T. fortunei in non‐alluvial forests, recognizing the ongoing and inevitable “laurophyllisation”; a biome shift toward mixed‐evergreen forest that may increase ecosystem climate resilience under ongoing climatic warming.

Growth Responses to Climate and Drought in Relict Cork Oak Populations as a Benchmark of the Species Tolerance

We still lack information on the long-term growth responses to climate of relict tree populations, which often persist in topoclimatic refugia. To fill that research gap, we studied three relict cork oak (Quercus suber) populations located in northern Spain using dendrochronology. The sites were subjected to humid (Zarautz), continental (Bozoó) and xeric (Sestrica) climate conditions. Cool–wet conditions during the current spring enhanced growth in Bozoó and Sestrica, whereas wet conditions in the previous October enhanced growth in Zarautz. In this site, growth also increased in response to dry conditions in the prior winter linked to high North Atlantic Oscillation indices. Correlations between the precipitation summed from the previous September to the current May peaked at the driest site (Sestrica). The strongest growth responses to drought severity were also found at this site, where growth negatively responded to 9-month early-summer droughts, followed by the continental Bozoó site, where growth was constrained by 1-month July droughts. Growth declined in response to 6-month January droughts in the wettest site (Zarautz), where cork oak was vulnerable to previous late-summer to autumn drought stress. Despite warmer and drier spring conditions that would negatively impact cork oak at the Bozoó and Sestrica sites, trees from these populations could tolerate further aridity.

Movement ecology and minimum density estimates of red foxes in wet grassland habitats used by breeding wading birds

The red fox (Vulpes vulpes) is a widely distributed generalist meso-predator implicated in declines of wading bird populations. In the wet grassland habitats where waders breed, wildlife managers work to mitigate fox predation risk to waders during the nesting period through lethal and non-lethal control methods. However, limited knowledge on fox movement ecology in these habitats makes it difficult to design effective management strategies. We used GPS telemetry to understand fox home range size, daily activity and movement patterns, and how these metrics may vary among wet grassland sites with different management. We caught and GPS-tagged 35 foxes in the March–June wader nesting period on two wet grassland sites in central southern England; Britford during 2016/17 and Somerley during 2018/19. We estimated home range areas from location data using local convex hulls, and from these estimates we derived the minimum fox density at each site and year. Daily activity patterns and movement behaviour of each fox were obtained using both telemetry and trail camera data. Mean fox home range area at Britford (0.21 km2, SE = 0.025) was significantly smaller than at Somerley (0.68 km2, SE = 0.067), and estimated minimum densities were around four times higher (Britford = 10.6 foxes/km2, Somerley = 2.4 foxes/km2). Foxes were more active and moved faster during twilight and night hours, but both telemetry and camera data indicate they were also active for one-third of daylight hours. Distances moved per day were variable between foxes but generally smaller at Britford. We also found evidence for dispersal during spring, with movements of up to 19 km per day. Home ranges at both wet grassland sites were smaller than comparable sites elsewhere. These indicated foxes were living at exceptionally high densities at Britford, where there is no fox control, increased food availability and where waders no longer breed. Spatio-temporal movement patterns were closely related to home range metrics, with higher levels of fox activity at Somerley, where home ranges were larger. The movements of itinerant and dispersing foxes during the nesting period suggests that lethal control would need to be very intensive to be effective. The likely anthropogenic food subsidy of fox density at Britford suggests that controlling access to similar food resources would help reduce predation pressure on breeding waders.

The fate of rice crop residues and context-dependent greenhouse gas emissions: Model-based insights from Eastern India

Crop residue burning is a common practice in many parts of the world that causes air pollution and greenhouse gas (GHG) emissions. Regenerative practices that return residues to the soil offer a ‘no burn’ pathway for addressing air pollution while building soil organic carbon (SOC). Nevertheless, GHG emissions in rice-based agricultural systems are complex and difficult to anticipate, particularly in production contexts with highly variable hydrologic conditions.Here we predict long-term net GHG fluxes for four rice residue management strategies in the context of rice-wheat cropping systems in Eastern India: burning, soil incorporation, livestock fodder, and biochar. Estimations were based on a combination of Tier 1, 2, and 3 modelling approaches, including 100-year DNDC simulations across three representative soil hydrologic categories (i.e., dry, median, and wet).Overall, residue burning resulted in total direct GHG fluxes of 2.5, 6.1, and 8.7 Mg CO2-e in the dry, median, and wet hydrologic categories, respectively. Relative to emissions from burning (positive values indicate an increase) for the same dry to wet hydrologic categories, soil incorporation resulted in a −0.2, 1.8, or 3.1 Mg CO2-e change in emissions whereas use of residues for livestock fodder increased emissions by 2.0, 2.1, or 2.3 Mg CO2-e. Biochar reduced emissions relative to burning by 2.9 Mg CO2-e in all hydrologic categories. This study showed that the production environment has a controlling effect on methane and, therefore, net GHG balance. For example, wetter sites had 2.8–4.0 times greater CH4 emissions, on average, than dry sites when rice residues were returned to the soil. To effectively mitigate burning without undermining climate change mitigation goals, our results suggest that geographically-target approaches should be used in the rice-based systems of Eastern India to incentivize the adoption of regenerative ‘no burn’ residue management practices.

Probing the interplay of biophysical constraints and photosynthesis to model tree growth

Tree growth is a key uncertainty in projections of forest productivity and the global carbon cycle. While global vegetation models commonly represent tree growth as a carbon assimilation (source)-driven process, accumulating evidence points toward widespread non-photosynthetic (sink) limitations. Notably, growth biophysical potential, defined as the upper-limit to tree growth imposed by temperature and turgor constraints on cell division, has been suggested to be a potent driver of observed decoupling between tree growth and photosynthesis. Understanding the interplay between biophysical potential and photosynthesis and how to accommodate it parsimoniously in models remains a challenge.Here, we use a soil-plant-atmosphere continuum model together with a regional network of forest structure and annual, radial tree growth observations extending over three decades to simulate tree photosynthesis and biophysical potential along an aridity gradient and across five tree species in NE Spain. We then apply a linear modelling framework to quantify the relative importance of photosynthesis, biophysical potential and their interactions to predict annual tree growth along the aridity gradient.Overall similar relative importance of photosynthesis and biophysical potential was underlain by strong variations with climate, photosynthesis being more relevant at wet sites and biophysical potential at dry sites. Observed spatial and temporal trends further suggested that tree growth is primarily limited by biophysical potential under dry conditions and that disregarding it could lead to underestimating tree growth decline with increased aridity under climate change.Our results support the idea that biophysical potential is an important component of sink limitations to tree radial growth. Its representation in vegetation models could accommodate spatially and temporally dynamic source-sink limitations on tree growth.

Shifts in internal stem damage along a tropical precipitation gradient and implications for forest biomass estimation.

Woody biomass is a large carbon store in terrestrial ecosystems. In calculating biomass, tree stems are assumed to be solid structures. However, decomposer agents such as microbes and insects target stem heartwood, causing internal wood decay which is poorly quantified. We investigated internal stem damage across five sites in tropical Australia along a precipitation gradient. We estimated the amount of internal aboveground biomass damaged in living trees and measured four potential stem damage predictors: wood density, stem diameter, annual precipitation, and termite pressure (measured as termite damage in downed deadwood). Stem damage increased with increasing diameter, wood density, and termite pressure and decreased with increasing precipitation. High wood density stems sustained less damage in wet sites and more damage in dry sites, likely a result of shifting decomposer communities and their differing responses to changes in tree species and wood traits across sites. Incorporating stem damage reduced aboveground biomass estimates by > 30% in Australian savannas, compared to only 3% in rainforests. Accurate estimates of carbon storage across woody plant communities are critical for understanding the global carbon budget. Future biomass estimates should consider stem damage in concert with the effects of changes in decomposer communities and abiotic conditions.

Increases in understory plant cover and richness persist following restoration treatments inPinus ponderosaforests

AbstractA combination of forest thinning followed by prescribed burning is widely applied in the western United States to increase ecosystem resistance and resilience to disturbances. Understory plant community responses may be driven by both management treatments and climatic factors. Thus, responses to treatments during a 20‐year megadrought have implications for the role of management in fostering adaptive capacity to climate change.We used a network of five sites (600 plots) spanning an environmental gradient in ponderosa pine (Pinus ponderosa) forests of the American Southwest, an ecosystem that is broadly distributed and actively managed throughout the western United States. We used repeated long‐term monitoring data to quantify plant community responses to treatment 1–5‐, 6–10‐ and &gt;10‐year post‐implementation. Specifically, we focussed on the effects of treatment and abiotic conditions on native and non‐native plant cover and species richness and the proportion of native species with northern (cool‐mesic) biogeographic affinities.Overall, thinning and prescribed burning nearly doubled native cover and increased native species richness by about 50% relative to untreated controls. These effects persisted for over a decade after treatment, even under the influence of significant and persistent drought. Cover and richness were also greater on intermediate to wet sites. Finally, native species with northern biogeographic affinities were reduced for up to 5 years after treatment relative to those with southern (warm‐xeric) affinities, and in dry years, indicating that both management and interannual climate variability may foster shifts to plant communities that are more resilient to a warming climate.Synthesis and applications. In ponderosa pine forests of the American Southwest, tree thinning followed by prescribed burning will generally promote restoration goals of increasing resilience to climate change by enhancing the diversity and abundance of native understory plant species, even during a persistent 20‐year megadrought.

Response of CO2 and CH4 emissions from Arctic tundra soils to a multifactorial manipulation of water table, temperature and thaw depth

Significant uncertainties persist concerning how Arctic soil tundra carbon emission responds to environmental changes. In this study, 24 cores were sampled from drier (high centre polygons and rims) and wetter (low centre polygons and troughs) permafrost tundra ecosystems. We examined how soil CO2 and CH4 fluxes responded to laboratory-based manipulations of soil temperature (and associated thaw depth) and water table depth, representing current and projected conditions in the Arctic. Similar soil CO2 respiration rates occurred in both the drier and the wetter sites, suggesting that a significant proportion of soil CO2 emission occurs via anaerobic respiration under water-saturated conditions in these Arctic tundra ecosystems. In the absence of vegetation, soil CO2 respiration rates decreased sharply within the first 7 weeks of the experiment, while CH4 emissions remained stable for the entire 26 weeks of the experiment. These patterns suggest that soil CO2 emission is more related to plant input than CH4 production and emission. The stable and substantial CH4 emission observed over the entire course of the experiment suggests that temperature limitations, rather than labile carbon limitations, play a predominant role in CH4 production in deeper soil layers. This is likely due to the presence of a substantial source of labile carbon in these carbon-rich soils. The small soil temperature difference (a median difference of 1 °C) and a more substantial thaw depth difference (a median difference of 6 cm) between the high and low temperature treatments resulted in a non-significant difference between soil CO2 and CH4 emissions. Although hydrology continued to be the primary factor influencing CH4 emissions, these emissions remained low in the drier ecosystem, even with a water table at the surface. This result suggests the potential absence of a methanogenic microbial community in high-centre polygon and rim ecosystems. Overall, our results suggest that the temperature increases reported for these Arctic regions are not responsible for increases in carbon losses. Instead, it is the changes in hydrology that exert significant control over soil CO2 and CH4 emissions.

Identifying biomass yield potential of tetra‐, hexa‐, and octoploid prairie cordgrass populations grown on marginal lands

AbstractAs the demand for renewable energy sources with reduced carbon emissions to the atmosphere increases, bioenergy crops remain an attractive alternative to fossil fuels. Another appeal of bioenergy crops is the potential utilization of marginal lands not suitable for food crops. Prairie cordgrass is a perennial warm‐season polyploid grass species that is considered a bioenergy crop that also exhibits a high tolerance for salinity and flooding. The ploidy level of prairie cordgrass has previously been suggested to correlate with agronomic traits. However, little is known about the agricultural performance of prairie cordgrass on marginal lands and if a correlation of ploidy level and stress tolerance exists. In this experiment, the productivity of tetra‐, hexa‐, and octoploids was investigated when grown on three different marginal sites, including waterlogged, saline, and low‐nutrient gravelly soils. Here, we found that prairie cordgrass populations annually produced dry biomass on a wet marginal site comparable to normal cropland. However, the productivity was remarkedly decreased at both a salt‐affected site and a limestone mine reclamation site. We were unable to conclude that different ploidy levels affected the biomass yield of prairie cordgrass grown under abiotic stress. However, there was a differential response of populations to various types of marginal sites. These results indicate potential genetic resources for developing breeding targets and identifying mechanisms of abiotic stress tolerance. Moreover, we highlight the need to generate diverse ploidy levels of prairie cordgrass in the same genetic backgrounds for future testing.

Enhanced efficiency urea fertilizers and timing effects on N2O emissions from spring wheat production in Manitoba

AbstractOpportunities exist to reduce nitrous oxide (N2O) emissions from nitrogen (N) fertilizers using enhanced efficiency fertilizers (EEFs) and managing application timing. This study examined (1) application timing (fall/spring) and (2) fertilizer N source on N2O emissions, yield, and N uptake of Canadian hard red spring wheat (Triticum aestivum L.) in Southern Manitoba. Fertilizer N sources included granular urea and four EEF products: (1) polymer‐coated urea (environmentally smart nitrogen [ESN]); (2) urea plus nitrification inhibitor (eNtrench); (3) urea plus urease inhibitor (Limus); and (4) urea plus nitrification and urease inhibitor (SuperU). Nitrification‐inhibited products most consistently reduced N2O emissions while maintaining productivity. Compared to urea alone, urea + eNtrench was most effective in reducing cumulative N2O emissions by 47%–64% at four of six site‐years. SuperU reduced N2O emissions by 37%–57% at three of six site‐years. ESN and urea + Limus did not affect emissions in most years. Wheat yield, protein, and N uptake were unaffected by N source in five of six site‐years. Compared to spring, fall application gave greater N2O emissions by 33%–67% at three of six site‐years due to spring‐thaw emissions. Fall was inferior to spring application in wetter site years with lower yield, protein, and N uptake. Overall, nitrification‐inhibited products—either alone or with a urease inhibitor—are a promising tool to reduce N2O emissions while maintaining wheat productivity in Manitoba. However, given that there were few consistent increases in yield or protein, the additional cost of the inhibitors will be a barrier to adoption.

CLASSIFICATION OF DWARF PINE COMMUNITIES IN THE NORTH OF THE KORYAK DISTRICT (KAMCHATKA TERRITORY)

A detailed geobotanical characteristic of Siberian dwarf-pine (Pinus pumila (Pall.) Regel) communities of the north of the Koryak District is presented. The vegetation classification based on 83 relevés has been elaborated using main principles and classification methods of Russian dominant-determinant approach. As the result 10 associations, 10 subassociations and 9 variants classified within 5 association groups were revealed. The peculiarities of their species composition, community structure, ecology and geographical distribution were characterized. Using soil characteristics, several types of sites were recognized. It was shown that mesophytic moss-rich dwarf-pine shrubs (Pinetum pumilae hylocomiosum) were closely connected to the mean values of soil moisture and soil fertility of the sites. Rhododendron-rich dwarf-pine communities (subass. Pinetum pumilae rhododendroso aurei–hylocomiosum) adjoined them but they usually occurred on higher altitudes. Lichen-rich dwarf-pine shrubs (Pinetum pumilae fruticuloso–cladinosum) occupied the driest and poorest sites at the upper border of dwarf-shrub altitudinal belt (350–400 m a.s.l.). The dwarf-shrub-rich Siberian dwarf-pine communities (ass. group Pineta pumilae fruticulosa) were closely connected to rather dry and poor sites. In wet sites with shallow groundwater, Sphagnum-rich dwarf-pine communities (Pinetum pumilae sphagnosum girgensohnii) were found. Cloudberry-rich dwarf-pine shrubs (subass. Pinetum pumilae chamaemori–rubosum) adjoined them but mainly occurred on the peat hillock of palsas. The variation in the species composition and structure of communities are determined by their position in the relief and the density of the dwarf-pine layer. With a similar density of dwarf-pine, Sphagnum-rich dwarf-pine communities form in the foothills, and lichen-rich dwarf-pine shrubs form in mountains. The species diversity and the abundance of the subordinate layers are significantly reduced at the maximum density of the dwarf-pine; so poor-herb dwarf-pine communities (Pineta pumilae oligoherbosa) are formed.

Waterlogging may reduce chemical soil C stabilization in forested peatlands

Boreal forested peatlands are globally significant carbon (C) pools where soil water-table level largely controls decomposition rate. Here we aimed to investigate the contrarian hypothesis that waterlogging conditions do not lead to increased C stabilization in a forested peatland. We studied how waterlogging affects root and soil chemistry, fungal biomass and necromass, C pools, soil enzyme activities and fungal community composition in Pinus sylvestris rhizosphere. Samples were collected from 0–10 cm, 10–20 cm and 20–30 cm soil layers in a controlled-environment experiment with waterlogging and control treatments and in two forested peatland sites, wetter and drier. Tannin content, live fungal biomass, enzyme activities, and chemically stable SOC content and its proportion of total SOC content were generally lower in waterlogged than control treatment in the experiment, and lower in the wetter than the drier site. The proportion of ectomycorrhizal fungi was higher in the drier than the wetter site in the deepest soil layer studied, 20–30 cm. In the wetter site, chemically stable SOC content and proportion of ericoid mycorrhizal fungi were highest in topsoil that contained more roots than deeper soil layers. In conclusion, forested peatlands possess specific root-related chemical SOC stabilization mechanisms, and, consequently, waterlogging makes their SOC more vulnerable due to decreased chemical C stabilization via root-microbial interactions and lowering root production.