Dry Sites Research Articles

Canopy structure and understorey light availability in Nothofagus and podocarp-broadleaf stands in a New Zealand forest

ABSTRACT The ability of some ectomycorrhizal fungi to access organic sources of nitrogen is known to influence decomposition, nitrogen mineralisation and soil carbon storage. The consequences for aboveground ecosystem structure and processes are less well-documented. We used the LAI-2200C Plant Canopy Analyzer to compare leaf area index and understorey light availability of ectomycorrhizal Nothofagus stands and arbuscular mycorrhizal podocarp-broadleaf stands growing on similar soils at a dry forest site in the Wairarapa district of New Zealand’s North Island. N. solandri was the sole overstorey tree in the three Nothofagus stands, and the ericaceous shrub Leucopogon fasciculatus was prominent in the understorey. The three podocarp-broadleaf stands were more diverse and more varied, the major contributors to basal area being Elaeocarpus dentatus, Hedycarya arborea, Cyathea dealbata, Carpodetus serratus and Dacrydium cupressinum. Leaf area index of Nothofagus stands averaged one unit lower (4.04) than that of neighbouring podocarp-broadleaf stands (5.11). Average light availability under Nothofagus stands (3.6–4.9%) was twice that beneath podocarp-broadleaf stands (1.6–2.1%). The lower leaf area index, greater light transmittance, and monodominance of Nothofagus stands probably reflects suppression of arbuscular mycorrhizal species by ectomycorrhizal short-circuiting of the nitrogen cycle. This study expands the evidence of positive feedback mechanisms stabilising ectomycorrhizal dominance in some forests.

A drought year favored drier‐adapted origins over local origins in a reciprocal transplant experiment along a rainfall gradient

When plant populations show local adaptation along climatic gradients, climate change may displace them from their current fitness optima. Unclear is whether foreign genotypes originating from sites that approximate future climatic conditions can attain higher fitness and support existing populations, because foreign genotypes may lack important adaptations to other local conditions besides climate. We conducted a fully reciprocal transplant experiment with the winter annual Biscutella didyma across four sites along a steep natural rainfall gradient in Israel. It experienced an exceptional drought event that approximated future climatic conditions. This unique opportunity allowed to test whether genotypes transplanted from drier sites outperform local genotypes under a drier climate. The four population origins showed consistent clines in germination fraction, phenology, and vegetative biomass that suggest local adaptation along the rainfall gradient. In terms of fitness (survival, seed number), however, local origins were outperformed by genotypes originating from the next‐drier site along the gradient. Our results suggest that the experienced drought conditions favored origins from drier conditions over local origins despite local biotic interactions. Genotypes originating from drier sites may thus support existing populations and reduce their vulnerability to climate change. Moreover, we conceptualize under which conditions foreign genotypes may benefit local populations in general, which adds to clarify the importance of local adaptation to climatic and nonclimatic factors for populations under climate change.

Challenges and risks of Serbian spruce (Picea omorika [pančić] purk.) in the time of climate change – a literature review

Abstract Serbian spruce (Picea omorika [Pančić] Purk.) is a Balkan endemic coniferous species, the expansion of which is restricted by limited knowledge. This literature review paper compiles findings from 176 scientific papers and presents a summary of research results that pertain to the Serbian spruce potential in general, with a specific focus on European forests from 1951 to 2022. It summarizes the importance of its taxonomy, biological and ecological characteristics, site demands, production and silviculture, risks and pests, as well as the potential of this tree species in relation to global climate change. Serbian spruce is very resistant to the negative effect of air pollution and extreme heat waves compared to other spruce species, especially the most economically important spruce species in Europe– Norway spruce (Picea abies [L.] Karst.). Moreover, its radial growth shows highly balanced annual increments, and the density and technical parameters of the wood are comparable with Norway spruce. On the other hand, the highest weakness may be the limited genetic variability. Despite its rather limited natural range, Serbian spruce can be considered one of the most adaptable spruces to anthropogenic factors and climate change, and a valuable tree species for urban landscapes. Its production potential of wood on acidic, dry and extreme sites makes it attractive for forestry, through its introduction.

Climatic variations along an aridity gradient drive significant trait intraspecific variability in Mediterranean plant species

Drought represents one of the main sources of stress for plants in the Mediterranean region, and climate change is further escalating this stress. Plants can employ several response strategies to cope with stress, reflected in the adoption of specific Plant Functional Traits (PFTs). Trait-based approaches commonly meet three issues: they may overlook Intraspecific Variability (ITV), they could focus on large spatial scales, or they could focus on few traits. Here we present evidence that it’s possible to observe ITV in morphological and anatomical trait syndromes between three local populations of Phillyrea latifolia, Pistacia lentiscus, and Quercus ilex, distributed along an aridity gradient. Thicker, physiologically expensive leaves and lower heights found in the drier sites mainly conform to drought-resistance strategies, while trait spectra from Cistus salviifolius were found not to vary significantly across sites. Thus, the amount of ITV observable at a local scale varies between species. We conclude that climate can easily drive a significant amount of ITV for several species, reflected in their trait spectra, among plant populations that are geographically close to each other. This highlights the importance of local environmental variability and implies that different populations hailing from nearby sites might respond differently to climate change.

Ring data provide management clues and pinpoint climate drivers of growth in two species of miombo trees (Brachystegia spiciformis, Julbernardia paniculata)

Tree-ring studies are still lacking in tropical African forests. This is the case in the seasonally dry miombo forests located in Southern Africa. In the Angolan miombo, subject to intense charcoal exploitation, tree-ring data is urgently needed to estimate the age at which the minimum permitted cutting diameter is reached. Further, climate-growth relationships must be also investigated to understand how major miombo tree species respond to climate constraints and teleconnections such as the El Niño Southern Oscillation (ENSO). To achieve both aims, we studied radial growth data of two miombo tree legume species (Brachystegia spiciformis, Julbernardia paniculata) in wet (Bailundo) and dry (Caála) Angolan sites using dendrochronological methods. Both species have diffuse porous wood and conspicuous ring boundaries delimited by terminal parenchyma in latewood. Sampled individuals had ages (at 1.3 m) between 28 and 34 years with ring widths ranging 3.8–4.3 and 5.5–6.0 mm in dry and wet sites, respectively. In the wet (dry) site, Brachystegia and Julbernardia reached maximum diameter increment rates of 1.05–1.32 (0.74–0.91) cm yr−1 at an age of 12 (14−20) years. Both species took 12–15 years to reach a minimum cutting diameter of 15 cm. The growth variability among conspecific individuals was lower in the dry (mean standard error, 1.4 cm) than in the wet site (mean standard error, 2.7 cm). We also found that wet conditions from November to February, often linked to El Niño events, enhanced growth for both species, with greater growth consistency among individuals and higher sensitivity to climate found in the dry site. This information may help to estimate the optimal age for minimum cutting diameter that guarantees the sustainable use of charcoal and fuelwood.

Anatomical and isotopic traits in grapevine wood rings record environmental variability

Summary In the Mediterranean region, prolonged droughts affect the growth and reproductive cycles of grapevine. Changes in the physiological processes of grapevine, consequent to variations in environmental factors or cultivation management, are recorded in wood anatomical and isotopic traits in grapevine stems. In this study, we measured the anatomical traits and stable carbon isotope content in the annual rings of Vitis vinifera L. subsp. vinifera ‘Falanghina’ in four vineyards located in southern Italy, characterised by different water availability. The aim was to investigate how wood anatomical traits respond to interannual climatic variations according to local conditions. Wood cores were taken from the stem of the grapevines and subjected to both microscopy and carbon stable isotope analyses to quantify functional wood anatomical traits, such as vessel size and frequency, and the intrinsic water-use efficiency of the grapevine. Wood traits were correlated with data on precipitation and temperature. The results showed that the plants at the four vineyards were characterised by differences in wood structure influencing the grapevine’s physiology under different conditions of water availability. Overall, the analyses showed that the grapevines at the wetter sites developed wood traits, e.g., wide vessels, which favour the efficiency of water flow, while at the drier sites, they developed plant traits, e.g., small vessels, which favour safety against embolism. However, the robustness of such main trends is trait-specific and is influenced by interannual climatic variability.

Moisture stress limits radial mixing of non-structural carbohydrates in sapwood of trembling aspen.

Dynamics in non-structural carbohydrate (NSC) pools may underlie observed drought legacies in tree growth. We assessed how aridity influences the dynamics of different-aged NSC pools in tree sapwood at two sites with differing climate conditions ('wet' vs. 'dry') that also experienced widespread regional drought five years earlier. We used an incubation method to measure radiocarbon (Δ14C) in CO2 respired from Populus tremuloides (aspen) tree rings to evaluate NSC storage and mixing patterns, coupled with measurements of NSC (soluble sugars, starch) concentrations and respired δ13C-CO2. At a wet site, CO2 respired from rings formed during 1962-1967 was only ~ 11years old, suggesting deep sapwood mixing of NSCs as starch. At a dry site, total NSC was about one-third of wet site totals, maximum ages in deep rings were lower, and ages more rapidly increased in shallow rings then plateaued. These results suggest historically shallower mixing and/or relatively higher consumption of NSCs under dry conditions. Both sites, however, had similar aged NSC (<1yr) in the most recent six rings, indicative of deep radial mixing following relatively wet conditions during the sampling year. We suggest significant differences in NSC mixing among sites are driven by moisture stress, where aridity reduces NSC reserves and restricts the depth of radial mixing. However, dynamic climate conditions in the southwestern US resulted in more complex radial patterns of sapwood NSC age than previously described. We suggest a novel conceptual framework to understand how moisture variability might influence the dynamics of NSC mixing in the sapwood.

Evaluation of the ECOSSE Model for Estimating Soil Respiration from Eight European Permanent Grassland Sites

This study used the ECOSSE model (v. 5.0.1) to simulate soil respiration (Rs) fluxes estimated from ecosystem respiration (Reco) for eight European permanent grassland (PG) sites with varying grass species, soils, and management. The main aim was to evaluate the strengths and weaknesses of the model in estimating Rs from grasslands, and to gain a better understanding of the terrestrial carbon cycle and how Rs is affected by natural and anthropogenic drivers. Results revealed that the current version of the ECOSSE model might not be reliable for estimating daily Rs fluxes, particularly in dry sites. The daily estimated and simulated Rs ranged from 0.95 to 3.1 g CO2-C m−2, and from 0.72 to 1.58 g CO2-C m−2, respectively. However, ECOSSE could still be a valuable tool for predicting cumulative Rs from PG. The overall annual relative deviation (RD) value between the cumulative estimated and simulated annual Rs was 11.9%. Additionally, the model demonstrated accurate simulation of Rs in response to grass cutting and slurry application practices. The sensitivity analyses and attribution tests revealed that increased soil organic carbon (SOC), soil pH, temperature, reduced precipitation, and lower water table (WT) depth could lead to increased Rs from soils. The variability of Rs fluxes across sites and years was attributed to climate, weather, soil properties, and management practices. The study suggests the need for additional development and application of the ECOSSE model, specifically in dry and low input sites, to evaluate the impacts of various land management interventions on carbon sequestration and emissions in PG.

Long-term changes in forest response to extreme atmospheric dryness.

Atmospheric dryness, as indicated by vapor pressure deficit (VPD), has a strong influence on forest greenhouse gas exchange with the atmosphere. In this study, we used long-term (10-30 years) net ecosystem productivity (NEP) measurements from 60 forest sites across the world (1003 site-years) to quantify long-term changes in forest NEP resistance and NEP recovery in response to extreme atmospheric dryness. We tested two hypotheses: first, across sites differences in NEP resistance and NEP recovery of forests will depend on both the biophysical characteristics (i.e., leaf area index [LAI] and forest type) of the forest as well as on the local meteorological conditions of the site (i.e., mean VPD of the site), and second, forests experiencing an increasing trend in frequency and intensity of extreme dryness will show an increasing trend in NEP resistance and NEP recovery over time due to emergence of long-term ecological stress memory. We used a data-driven statistical learning approach to quantify NEP resistance and NEP recovery over multiple years. Our results showed that forest types, LAI, and median local VPD conditions explained over 50% of variance in both NEP resistance and NEP recovery, with drier sites showing higher NEP resistance and NEP recovery compared to sites with less atmospheric dryness. The impact of extreme atmospheric dryness events on NEP lasted for up to 3 days following most severe extreme events in most forests, indicated by an NEP recovery of less than 100%. We rejected our second hypothesis as we found no consistent relationship between trends of extreme VPD with trends in NEP resistance and NEP recovery across different forest sites, thus an increase in atmospheric dryness as it is predicted might not increase the resistance or recovery of forests in terms of NEP.

Does shading and ground cover of moss and litter improve germination and establishment of Betula pendula Roth, Salix caprea L. and Populus tremula L. seedlings during drought stress in climate change? – A greenhouse study

The climate change is leading to a significant increase in temperatures and dry periods in spring, for example in parts of middle and north Europe. Thus, the important factor for tree growth, the water availability, decreases on forest sites. It is to be expected that the successful establishment of pioneer tree species as pre-forests on large damaged areas will considerable be limited in the future. The phases of germination and establishment are the most dangerous phase in the life of trees. In this greenhouse study, we tested how different microsite conditions (open soil, moss and litter cover as well as different shading) under reduced water availability influence establishment success and growth of Betula pendula, Populus tremula and Salix caprea.The initial high germination success were reduced to 14%, 7% and 12% for Populus tremula, Salix caprea and Betula pendula, respectively, and the growth were significantly slower when the relevant soil water resource was just above the permanent wilting point. Therefore, in the first year the germination and establishment is linked to persistent moist conditions. If the soil dries out during germination, e.g. if there is no watering for more than 3 weeks, all seedlings died. Equivalent germination microsites (shading or ground cover) with comparable possible seedling densities to the moist open soil does not exist under water stress. Although moss and litter cover retain longer soil moisture under extremely dry conditions and guarantee significantly better seedling development than on open soil, initially significantly fewer seeds germinate on these substrate types.Radiation shows no influence on germination and seedling survival. The seedlings are able to survive radiation conditions of 3% and 27% of open area radiation. This makes establishment possible under (remaining) light canopy, at the edge of damaged areas or in small islands of remaining shelter trees on damaged areas. However, radiation had a significant effect on growth. With increasing radiation, shoot lengths and above ground biomasses are higher and the root collar diameter larger.Overall, Betula pendula is the most drought stress resistant of the tested tree species. While Populus tremula and Salix caprea already had problems establishing themselves on dry sites, the problem will become more serious under climate change. The lack of moist, vegetation-free open soils will result in a significant reduction of establishment success for tested pioneer tree species in climate change.

Convergent morphology and anatomy in the microphyllous leaves of selected heathland Myrtaceae and Asteraceae

Key messageWe examined leaves of a suite of microphyllous woody plants and describe a little-known form of leaf peltation for the first time and also investigate strongly reflexed leaves in two distantly related lineages.Plants cope with a range of environmental conditions, especially related to water relations, and have developed an array of physiological and structural solutions to maintain a functional water balance. There has been considerable recent work on physiological solutions to water deficit but little attention paid to leaf characteristics. In many species there is a change in leaf form from seedlings to adults. We examine such changes in several small-leaved species from the distantly related Asteraceae and Myrtaceae, some of which develop micropeltate or reflexed leaves as adults. All are native to dry or seasonally dry sites. Three major morphological groups were recognised as follows: (1) leaves erect, nonpeltate and scale-like (Ozothamnus hookeri), (2) leaves erect and peltate (Phaenocoma prolifera, Regelia inops), (3) Leaves reflexed (Olearia lepidophylla, Ozothamnus scutellifolius, Ozothamnus reflexifolius, Melaleuca diosmifolia). The microphyllous peltation in P. prolifera and R. inops in the absence of a meristematic fusion/bridge differs from typically peltate leaves. These small-leaved taxa occur in open, high light environments which are very different from the mesic, shaded understorey habitats of typical peltate-leaved plants. Many small-leaved species have leaves closely appressed to the stem and often with recurved margins. The erect leaves are functionally similar to reflexed leaves. Environmental filtering leads to superficially similar plant forms that may have somewhat different ontological origins. Such morphological forms are examples of convergent evolution in distantly related species but within each family are likely phylogenetically related.

Strong latitudinal gradient in temperature-growth coupling near the treeline of the Canadian subarctic forest

Boreal forests are experiencing severe climatic changes that vary widely across the broad geographic distribution of the biome. The changes are greatest near the subarctic treeline where trees often exhibit high climatic sensitivity because climatic conditions approach the limits of their physiological tolerance. Despite the importance of subarctic boreal forests, the lack of field-acquired growth data remains a critical issue that limits the generalization of forest productivity models across the entire boreal biome. Using tree-ring chronologies from remote stands distributed along three latitudinal gradients ranging from 65 to 102°W, we investigated recent trends in black spruce growth and their relationships with recent climate warming near the subarctic treeline in eastern Canada. Our results show a generally positive effect of temperature and a negative effect of precipitation, both indicating that black spruce growth is temperature-limited near its northern range limit. However, we observed a strong gradient in temperature-growth coupling within a small latitudinal gradient (about one degree of latitude), where strong temperature constraints appear limited to the northernmost, coldest stands. Moreover, the positive growth response to temperature decreased from wetter to dryer sites and climate-growth coupling declined over the study period in the driest sites. These results suggest that the growth increase associated with warmer temperature may be limited by reduced precipitation and potential moisture limitation. Lastly, our results suggest that acute climatic events have the potential to induce abrupt shifts in tree climate-growth relationships. Such results indicate that the expected beneficial effect of warming on high latitude tree growth may be less generalized and more complex than previously thought in northeastern Canada, perhaps due to factors other than temperature, which might confound the climate-growth coupling southwards. Thus, our results highlight the need for a better understanding of additional growth drivers in these poorly studied regions and for physiologically informed definitions of acute climatic events, in order to refine broad-scale forest productivity modeling.

Targeted irrigation expands scope for winter cereal production in water-limited areas of California's San Joaquin Valley

CONTEXTEfforts to achieve groundwater sustainability in California's San Joaquin Valley will entail substantial pumping reductions, and much irrigated cropland may become newly fallowed. Winter crops grown under water-limited conditions could offer an alternative to fallowing, but their viability may be limited by variable rainfall and high crop failure rates. OBJECTIVEThe first objective of this study was to evaluate how small (100–200 mm), targeted irrigation events impact crop establishment, forage and grain yields, and the resulting economic and agronomic water productivity of winter wheat at 4 sites in the San Joaquin Valley. Additionally, we assessed the probability of producing economically viable forage yields across the region based on historical precipitation totals combined with 0, 100, or 200 mm of supplemental irrigation. METHODSWe used APSIM to run 20-yr simulations of winter wheat establishment and productivity under historical weather conditions at four groundwater dependent sites in California's San Joaquin Valley. For each site, we simulated wheat productivity (biomass and grain) under three irrigation scenarios (no irrigation, 100 mm, or 200 mm) and three sowing dates (mid-October, mid-November, and mid-December). We applied model outputs to calculations of economic and agronomic water productivity, and used the modeled relationship between soft dough biomass yield and total water input (precipitation plus irrigation) to determine the likelihood of a successful wheat crop in any given year across the region. RESULTS AND CONCLUSIONSWe found that two 100 mm applications of irrigation applied at times of critical soil water depletion decreased crop failure rates from 45% of years to 0% of years at the driest site. Economic water productivity was highest when wheat was harvested for forage at the soft dough stage, and agronomic water productivity of soft dough forage was highest with supplemental irrigation and early planting. Given the precipitation requirements to achieve economically viable soft dough-stage forage yields, the addition of 100 mm of irrigation in a single event expanded the potential cropping area to 11% (126,356 ha) of groundwater dependent cropland in the region, while 200 mm of irrigation expanded the potential cropping area to 100% (1,109,888 ha) of cropland. SIGNIFICANCEThese results suggest that small, targeted supplemental irrigation events could greatly expand the scope for water-limited winter forage production in the San Joaquin Valley. Such an approach could serve as an alternative to land fallowing in areas transitioning away from irrigated summer crops where appropriate technological and policy mechanisms are in place.

Decomposition and elemental release of leaf litter in Kandelia obovata mangrove forests under different sea level rise scenarios

Leaf litter decomposition is an important source of carbon and nutrients to mangrove soil and fauna, and adjacent costal ecosystems. Mangrove forests are extremely sensitive to sea level rise which may affect leaf litter decomposition. Seasonal decomposition and elemental release (i.e., carbon, nitrogen and phosphorous) of leaf litter were investigated at three Kandelia obovata mangrove sites with different tidal elevations, such as RSL (rising sea level) 0 cm, RSL 40 cm and RSL 80 cm, simulating the sea level rise scenarios by 0 cm, 40 cm and 80 cm, respectively. Half-time (T50) of leaf litter decomposition was 31.4 d in spring, 17.3 d in summer, 15.1 d in autumn and 35.1 d in winter. Mean decomposition rate and dry weight loss rate of leaf litter at site RSL 0 cm were obviously higher than values at sites RSL 80 cm and RSL 40 cm, with annual mean T50 values of 21.4 d, 30.7 d and 30.3 d at sites RSL0 cm, RSL 40 cm and RSL 80 cm, respectively. Elemental releases of leaf litter were very similar to dry weight loss rate and site RSL 0 cm had significantly higher elemental releases. These indicated that sea level rise will decrease decomposition and elemental release of mangrove leaf litter.

Weeds as Indicators of Soil Conditions in Lawns and Landscapes

The purpose of this publication is to provide examples of weeds commonly found under certain environmental conditions. While weeds can be an indicator of a certain condition, some weed species can thrive in many different environments and are indicated in the following tables with an asterisk. For example, spotted spurge (Euphorbia maculata) can be indicative of a dry site, but it will grow and spread very well in sites that are over-irrigated also. The presence of one or two weed species is not necessarily diagnostic to a specific cultural problem, but heavy infestations or the presence of multiple species that prefer a particular condition could indicate that cultural practices should be altered.

Root trait variation along water gradients in the Cape Floristic Region

AbstractQuestionsRoots are responsible for essential plant functions including water uptake. However, the extent to which root traits (size and structure) determine plant presence in water‐limited environments is still poorly understood. Here we investigated how root traits vary across water availability gradients within a dry South African biome.LocationSouth Africa.MethodsWe measured six below‐ground (root) and eight above‐ground (leaf + stem) traits of 124 individuals of nine dominant woody shrub species from wetter and drier sites (600–700 vs 250–300 mm annual precipitation) in the Fynbos biome of the Cape Floristic Region. Within sites, we sampled from recently burnt and unburnt/more mature vegetation and at three locations along topographical gradients.ResultsDrier regions showed greater maximum rooting depth, length, root dry matter content and root to shoot ratio. These trait patterns were consistent at an intraspecific level, along locally drier topographical locations and in post‐fire environments. Roots accounted for significant whole‐plant trait variation. Additionally, in drier conditions, we found increased root allocation deviating from expected global allometric relationships. Our study also demonstrates that the combination of fire and drought in the driest locations results in poor above‐ground vegetation recovery in terms of plant size, cover and individual counts with only resprouters persisting.ConclusionsOur research suggests that root investment in Fynbos shrubs will likely be key for coping with a drier and warmer future and should be a focus of more research for dryland biomes.

Roles of lower-side leaf trichomes in diffusion resistance and gas-exchange characteristics across environmental gradients in Metrosideros polymorpha.

Leaf trichomes on the lower leaf surface are common in many plant species, especially those grown under dry and/or low-temperature conditions; however, their adaptive significance remains unclear. Lower-side leaf trichomes can directly decrease gas fluxes through increased gas-diffusion resistance but can indirectly increase gas fluxes through increased leaf temperature owing to increased heat-diffusion resistance. We examined whether the combined direct and indirect effects of trichome resistance increase photosynthetic rates and water-use efficiency (WUE) using Metrosideros polymorpha Gaud., which varies widely in the masses of lower-side non-glandular leaf trichomes across various environments on the Hawaiian Islands. We employed both field surveys, including ecophysiological measurements at five elevation sites, and simulation analyses to predict the gas-exchange rates of leaves with various trichome-layer thicknesses across a wide range of environmental conditions. Field surveys showed that the trichome-layer thickness was the largest at the coldest and driest site and the thinnest at the wettest site. Field surveys, experimental manipulations and simulation analyses demonstrated that leaf trichomes significantly increased leaf temperature owing to the increased heat resistance. Simulation analyses showed that the effect of leaf trichomes on heat resistance was much larger than that on gas-flux resistance. Leaf trichomes can increase daily photosynthesis only in cold dry areas by increasing the leaf temperature. However, the increased leaf temperature with leaf trichomes resulted in a consistent decrease in the daily WUE at all elevation sites. The magnitudes of trichome effects on gas-exchange rates were associated with the temperature difference across the elevational gradient, the strong light intensity in Hawaii, the leaf-size variation and the conservative stomatal behavior of M. polymorpha as well as the trichome-layer thickness. In summary, the lower-side leaf trichomes in M. polymorpha can be beneficial for carbon assimilation in low-temperature environments but not for water conservation in most environments in terms of diffusion resistance.

Plant macro-remains from a large middle Neolithic settlement in SE Poland – Internal diversification and possible status of the settlers

The Mozgawa site, covering area of ca. 40 ha, is located in the loess area in SE Poland. It belongs to large settlements of the Middle Neolithic Funnel Beaker culture (TRB) and was occupied ca. 3600–3200 BCE. The aim of the research was to assess the role of plants in the life of the settlers, including domesticated and wild food resources as well as possibilities of non-alimentary use of herbal plants. The connection of two types of plant macroremains, namely seeds/fruits and wood charcoal, found in three different parts of the site was done to evaluate possibility of spatial palaeoeconomic differentiation between the sectors of the settlement. The site is exceptional among the other TRB dry sites studied due to high quantities of flax seeds and pulses, namely lentil, although the most numerous were wheat remains, mostly emmer grains. The high number of charred seeds of gromwell, the crop weed but also a source of purple dye, which was linked to flax seeds in statistical analysis, could suggest production of purple or red textiles at the site. High significance of textile production can be supported by discovery of a broad spectrum of utensils, representing all chaîne opératoire stages. Nonetheless, there are no convincing archaeological premises according specialisation of textile production at the settlement. Taking into account the proportions of main groups of plants among the three studied parts of the site, some differences were noticed, which could indicate the diversification of past activities at the settlement. The detailed study of other categories of findings and exact spatial–temporal scheme of settlement development are necessary to confirm this diversification and assess whether it mirrors higher material and social status of people living in the central part of the settlement than those living in the NW and SE parts.

Complexity and Predictability of Daily Actual Evapotranspiration Across Climate Regimes

AbstractEstimation of actual evapotranspiration (ETa) is challenging due to its complex interactions with surrounding environments; thus, understanding the complexity and predictability of ETa along with its influencing factors is essential to improve ETa estimation. Based on the FLUXNET and ChinaFLUX datasets, we first examined whether daily ETa exhibited chaotic behaviors, and then investigated how daily ETa complexity and predictability varied across climate regimes and ecosystems using the chaos theory. The results of recurrence plot and correlation dimension (CD) analysis suggested the existence of chaotic behaviors in daily ETa, implying the system controlling ETa processes was deterministic with a limited number of controlling variables. The recurrence quantification analysis further revealed a varying degree of complexity for ETa processes (e.g., determinism‐DET with a range from 0.01% to 40.7%) across the sites. Specifically, daily ETa featured stronger deterministic properties (e.g., higher DET and lower CD values) and thus higher predictability in humid and arid regions; whereas, higher degrees of daily ETa complexity emerged in sub‐humid and semi‐arid regions due to more complex interactions with environmental factors. Moreover, primary environmental controls on daily ETa complexity varied with climatic and land surface conditions. Results showed that energy and water supplies along with average daily temperature and relative humidity were the primary controls on the ETa complexity across the sites, while leaf area index also played an important role at drier sites. As a first attempt, this study provides additional avenues to understand the complexity of ETa processes from a global perspective using the chaos theory.

Ratio of In Situ CO2 to CH4 Production and Its Environmental Controls in Polygonal Tundra Soils of Samoylov Island, Northeastern Siberia

AbstractArctic warming causes permafrost thaw and accelerates microbial decomposition of soil organic matter (SOM) to carbon dioxide (CO2) and methane (CH4). The determining factors for the ratio between CO2 and CH4 formation are still not well understood due to scarce in situ measurements, particularly in remote Arctic regions. We quantified the CO2:CH4 ratios of SOM decomposition in wet and dry tundra soils by using CO2 fluxes from clipped plots and in situ CH4 fluxes from vegetated plots. At the water‐saturated site, CO2:CH4 ratios decreased sharply from 95 at beginning of July to about 10 in August and September with a median of 12.2 (7.70–17.1; 25%–75% quartiles) over the whole vegetation period. When considering CH4 oxidation, estimated to reduce in situ CH4 fluxes by 10%–31%, even lower CO2:CH4 ratios were calculated (median 10.9–8.41). Active layer depth and soil temperature were the main factors controlling these ratios. Methane production was associated with subsoil (40 cm) temperature, while heterotrophic respiration was related to topsoil (5 cm) temperatures. As expected, CO2:CH4 ratios were substantially higher at the dry site (median 373, 292–500, 25%–75% quartiles). Both tundra types lost carbon preferentially in form of CO2, and CH4‐C represented only 0.27% of the dry tundra total carbon loss and 6.91% of the wet tundra total carbon loss. The current study demonstrates the dynamic of in situ CO2:CH4 ratios from SOM decomposition and will help improve simulations of future CO2 and CH4 fluxes from thawing tundra soils.