Stable Isotopes Reveal the Drivers of Post-Wildfire Natural Regeneration of Interior Douglas-Fir Seedlings in British Columbia.

Wildfires are increasing in frequency and severity due to climate change, posing challenges to forest ecosystems, including the southern interior of British Columbia, Canada. Interior Douglas-fir () is a species of great cultural, ecological, and economic importance, necessitating the investigation of post-wildfire regeneration amidst this changing wildfire regime. This study examines interior Douglas-fir seedling regeneration across three burn severity levels (low, moderate, high) 5 years post-wildfire at a site in interior British Columbia.

Mistletoe-induced carbon, water and nutrient imbalances are imprinted on tree rings.

Mistletoes are xylem-tapping hemiparasites that rely on their hosts for water and nutrient uptake. Thus, they impair tree performance in the face of environmental stress via altering the carbon and water relations and nutritional status of trees. To improve our understanding of physiological responses to mistletoe and ongoing climate change, we investigated radial growth, stable carbon and oxygen isotopic signals, and elemental composition of tree rings in silver fir (Abies alba Mill.

Evaluation of the trade-off between water use efficiency and nutrient use efficiency in two semiarid coniferous tree species growing on an organic amended metalliferous mine tailing substrate.

We evaluated the ecophysiological responses of two semiarid coniferous tree species, Pinus halepensis and Tetraclinis articulata, growing on a nutrient-poor metalliferous mine tailings substrate to organic amendments (biochar and/or organic municipal waste). The trees were grown in mesocosms under irrigated conditions for 20 months. Then, a comprehensive characterization of soil and plant parameters (including stable isotopes) was carried out.

Tight coupling between leaf δ C and N content along leaf ageing in the N -fixing legume tree black locust (Robinia pseudoacacia L.).

N -fixing legumes can strongly affect ecosystem functions by supplying nitrogen (N) and improving the carbon-fixing capacity of vegetation. Still, the question of how their leaf-level N status and carbon metabolism are coordinated along leaf ageing remains unexplored. Leaf tissue carbon isotopic composition (δ C) provides a useful indicator of time-integrated intrinsic water use efficiency (WUEi).

Higher leaf nitrogen content is linked to tighter stomatal regulation of transpiration and more efficient water use across dryland trees.

The least-cost economic theory of photosynthesis shows that water and nitrogen are mutually substitutable resources to achieve a given carbon gain. However, vegetation in the Sahel has to cope with the dual challenge imposed by drought and nutrient-poor soils. We addressed how variation in leaf nitrogen per area (N ) modulates leaf oxygen and carbon isotopic composition (δ O, δ C), as proxies of stomatal conductance and water-use efficiency, across 34 Sahelian woody species.

The role of nutritional impairment in carbon-water balance of silver fir drought-induced dieback.

Rear-edge populations at the xeric distribution limit of tree species are particularly vulnerable to forest dieback triggered by drought. This is the case of silver fir (Abies alba) forests located in Southwestern Europe. While silver fir drought-induced dieback patterns have been previously explored, information on the role played by nutritional impairment is lacking despite its potential interactions with tree carbon-water balances.

The Economics Spectrum Drives Root Trait Strategies in Mediterranean Vegetation.

Extensive research efforts are devoted to understand fine root trait variation and to confirm the existence of a belowground root economics spectrum (RES) from acquisitive to conservative root strategies that is analogous to the leaf economics spectrum (LES). The economics spectrum implies a trade-off between maximizing resource acquisition and productivity or maximizing resource conservation and longevity; however, this theoretical framework still remains controversial for roots. We compiled a database of 320 Mediterranean woody and herbaceous species to critically assess if the classic economics spectrum theory can be broadly extended to roots.

Contrasting Responses of Arbuscular Mycorrhizal Fungal Families to Simulated Climate Warming and Drying in a Semiarid Shrubland.

We carried out a 4-year manipulative field experiment in a semiarid shrubland in southeastern Spain to assess the impacts of experimental warming (W), rainfall reduction (RR), and their combination (W + RR) on the composition and diversity of arbuscular mycorrhizal fungal (AMF) communities in rhizosphere soil of H. syriacum and G. struthium shrubs using single-molecule real-time (SMRT) DNA sequencing.

Lower relative abundance of ectomycorrhizal fungi under a warmer and drier climate is linked to enhanced soil organic matter decomposition.

The aboveground impacts of climate change receive extensive research attention, but climate change could also alter belowground processes such as the delicate balance between free-living fungal decomposers and nutrient-scavenging mycorrhizal fungi that can inhibit decomposition through a mechanism called the Gadgil effect. We investigated how climate change-induced reductions in plant survival, photosynthesis and productivity alter soil fungal community composition in a mixed arbuscular/ectomycorrhizal (AM/EM) semiarid shrubland exposed to experimental warming (W) and/or rainfall reduction (RR). We hypothesised that increased EM host plant mortality under a warmer and drier climate might decrease ectomycorrhizal fungal (EMF) abundance, thereby favouring the proliferation and activity of fungal saprotrophs.

Vertical decoupling of soil nutrients and water under climate warming reduces plant cumulative nutrient uptake, water-use efficiency and productivity.

Warming-induced desiccation of the fertile topsoil layer could lead to decreased nutrient diffusion, mobility, mineralization and uptake by roots. Increased vertical decoupling between nutrients in topsoil and water availability in subsoil/bedrock layers under warming could thereby reduce cumulative nutrient uptake over the growing season. We used a Mediterranean semiarid shrubland as model system to assess the impacts of warming-induced topsoil desiccation on plant water- and nutrient-use patterns.

Nutrient limitation determines the suitability of a municipal organic waste for phytomanaging metal(loid) enriched mine tailings with a pine-grass co-culture.

The suitable phytomanaging of mine tailings not only requires an improvement of soil fertility but also the assessment of the biotic interactions between the selected plant species. This study aimed to evaluate the effect of an organic amendment on the response of two plant species of contrasting habit, a tree, Pinus halepensis and a grass, Piptatherum miliaceum growing on a metal(loid)-contaminated substrate collected from mine tailings. Pots containing single plant individuals or their combination, with and without organic amendment (at 10% rate), were established and grown in a greenhouse for 13 months.

Poor plant performance under simulated climate change is linked to mycorrhizal responses in a semiarid shrubland.

Warmer and drier conditions associated with ongoing climate change will increase abiotic stress for plants and mycorrhizal fungi in drylands worldwide, thereby potentially reducing vegetation cover and productivity and increasing the risk of land degradation and desertification. Rhizosphere microbial interactions and feedbacks are critical processes that could either mitigate or aggravate the vulnerability of dryland vegetation to forecasted climate change.We conducted a four-year manipulative study in a semiarid shrubland in the Iberian Peninsula to assess the effects of warming (~2.

Importance of intra- and interspecific plant interactions for the phytomanagement of semiarid mine tailings using the tree species Pinus halepensis.

The objective of this work was to evaluate the effects of plant interactions (intra- and interspecific) on the growth and metal(loid) uptake of the tree species Pinus halepensis to determine its suitability for the phytomanagement of semiarid mine tailings. The pioneer tailings colonizer grass Piptatherum miliaceum was selected for assessing interspecific interactions. The experiment was conducted following a pot experimental design employing mine tailings soil.

Nurse plants transfer more nitrogen to distantly related species.

Plant facilitative interactions enhance co-occurrence between distant relatives, partly due to limited overlap in resource requirements. We propose a different mechanism for the coexistence of distant relatives based on positive interactions of nutrient sharing. Nutrients move between plants following source-sink gradients driven by plant traits that allow these gradients to establish.

Metal(loid) allocation and nutrient retranslocation in Pinus halepensis trees growing on semiarid mine tailings.

The goal of this study was to evaluate internal metal(loid) cycling and the risk of metal(loid) accumulation in litter from Pinus halepensis trees growing at a mine tailing disposal site in semiarid Southeast Spain. Internal nutrient retranslocation was also evaluated in order to gain insight into the ability of pine trees to cope with the low-fertility soil conditions at the tailings. We measured metal(loid) concentrations in the foliage (young and old needles), woody stems and fresh leaf litter of pine trees growing on tailings.

Usefulness of pioneer vegetation for the phytomanagement of metal(loid)s enriched tailings: grasses vs. shrubs vs. trees.

The goal of this work was to assess the selection of the most suitable combination of plant species for the phytomanagement of mine tailings, by comparing among different plant life-forms (grasses, shrubs and trees). A comparison on induced rhizosphere changes generated by four plant species (the grass Piptatherum miliaceum, the shrub Helichrysum decumbens, and the trees, Pinus halepensis and Tetraclinis articulata) and high density vegetation patches (fertility islands) at a mine tailing located at Southeast Spain and the description of their physiological status employing stable isotopes analyses were carried out. The edaphic niches for plant growth were determined by salinity, organic matter and total soil nitrogen while metal(loid)s concentrations played a minor role.

Isotopes reveal contrasting water use strategies among coexisting plant species in a Mediterranean ecosystem.

Variation in the stable carbon and oxygen isotope composition (δ13C, Δ18O) of co-occurring plant species may reflect the functional diversity of water use strategies present in natural plant communities. We investigated the patterns of water use among 10 coexisting plant species representing diverse taxonomic groups and life forms in semiarid southeast Spain by measuring their leaf δ13C and Δ18O, the oxygen isotope ratio of stem water and leaf gas exchange rates. Across species, Δ18O was tightly negatively correlated with stomatal conductance (gs), whereas δ13C was positively correlated with intrinsic water use efficiency (WUEi).

Stand structure modulates the long-term vulnerability of Pinus halepensis to climatic drought in a semiarid Mediterranean ecosystem.

We investigated whether stand structure modulates the long-term physiological performance and growth of Pinus halepensis Mill. in a semiarid Mediterranean ecosystem. Tree radial growth and carbon and oxygen stable isotope composition of latewood (δ(13)C(LW) and δ(18)O(LW), respectively) from 1967 to 2007 were measured in P.

No tillage affects the phosphorus status, isotopic composition and crop yield of Phaseolus vulgaris in a rain-fed farming system.

Background: Conservation tillage promotes the accretion of soil organic matter and often leads to improved soil fertility and moisture availability. However, few studies have looked at the physiological response of crop plants to different tillage practices. It was therefore hypothesised that measuring the nutrient concentrations and stable isotope composition (δ(13)C, δ(18)O, δ(15)N) of shoots could help evaluate the physiological response of common bean (Phaseolus vulgaris L.

Efflux of hydraulically lifted water from mycorrhizal fungal hyphae during imposed drought.

Apart from improving plant and soil water status during drought, it has been suggested that hydraulic lift (HL) could enhance plant nutrient capture through the flow of mineral nutrients directly from the soil to plant roots, or by maintaining the functioning of mycorrhizal fungi. We evaluated the extent to which the diel cycle of water availability created by HL covaries with the efflux of HL water from the tips of extramatrical (external) mycorrhizal hyphae, and the possible effects on biogeochemical processes. Phenotypic mycorrhizal fungal variables, such as total and live hyphal lengths, were positively correlated with HL efflux from hyphae, soil water potential (dawn), and plant response variables (foliar (15)N).

Common mycorrhizal networks provide a potential pathway for the transfer of hydraulically lifted water between plants.

Plant roots may be linked by shared or common mycorrhizal networks (CMNs) that constitute pathways for the transfer of resources among plants. The potential for water transfer by such networks was examined by manipulating CMNs independently of plant roots in order to isolate the role(s) of ectomycorrhizal (EM) and arbuscular mycorrhizal fungal (AMF) networks in the plant water balance during drought (soil water potential -5.9 MPa).

Water transfer via ectomycorrhizal fungal hyphae to conifer seedlings.

Little is known about water transfer via mycorrhizal hyphae to plants, despite its potential importance in seedling establishment and plant community development, especially in arid environments. Therefore, this process was investigated in the study reported in this paper in laboratory-based tripartite mesocosms containing the shrub Arctostaphylos viscida (manzanita) and young seedlings of sugar pine (Pinus lambertiana) and Douglas-fir (Pseudotsuga menziesii). The objectives were to determine whether water could be transported through mycorrhizal symbionts shared by establishing conifers and A.

Water source partitioning among trees growing on shallow karst soils in a seasonally dry tropical climate.

The sources of water used by woody vegetation growing on karst soils in seasonally dry tropical regions are little known. In northern Yucatan (Mexico), trees withstand 4-6 months of annual drought in spite of the small water storage capacity of the shallow karst soil. We hypothesized that adult evergreen trees in Yucatan tap the aquifer for a reliable supply of water during the prolonged dry season.

Differential response of delta13C and water use efficiency to arbuscular mycorrhizal infection in two aridland woody plant species.

During a revegetation field experiment in Southeast Spain, we measured foliar carbon isotope ratios (delta13C) and gas exchange parameters in order to evaluate the influence of arbuscular mycorrhizal (AM) infection on the water use efficiency (WUE) of two semiarid woodland species. WUE during drought was significantly enhanced by inoculation with Glomus intraradices in Olea europaea ssp sylvestris, but not in Rhamnus lycioides. While Olea is a long-lived, slow-growing evergreen tree with a conservative water use strategy, Rhamnus is a drought-deciduous shrub with a shorter lifespan; these differences may explain their dissimilar patterns of physiological response to inoculation with the same AM fungus.