Browsing by Subject "drought"

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  • Trotsiuk, Volodymyr; Hartig, Florian; Cailleret, Maxime; Babst, Flurin; Forrester, David I.; Baltensweiler, Andri; Buchmann, Nina; Bugmann, Harald; Gessler, Arthur; Gharun, Mana; Minunno, Francesco; Rigling, Andreas; Rohner, Brigitte; Stillhard, Jonas; Thurig, Esther; Waldner, Peter; Ferretti, Marco; Eugster, Werner; Schaub, Marcus (2020)
    The response of forest productivity to climate extremes strongly depends on ambient environmental and site conditions. To better understand these relationships at a regional scale, we used nearly 800 observation years from 271 permanent long-term forest monitoring plots across Switzerland, obtained between 1980 and 2017. We assimilated these data into the 3-PG forest ecosystem model using Bayesian inference, reducing the bias of model predictions from 14% to 5% for forest stem carbon stocks and from 45% to 9% for stem carbon stock changes. We then estimated the productivity of forests dominated by Picea abies and Fagus sylvatica for the period of 1960-2018, and tested for productivity shifts in response to climate along elevational gradient and in extreme years. Simulated net primary productivity (NPP) decreased with elevation (2.86 +/- 0.006 Mg C ha(-1) year(-1) km(-1) for P. abies and 0.93 +/- 0.010 Mg C ha(-1) year(-1) km(-1) for F. sylvatica). During warm-dry extremes, simulated NPP for both species increased at higher and decreased at lower elevations, with reductions in NPP of more than 25% for up to 21% of the potential species distribution range in Switzerland. Reduced plant water availability had a stronger effect on NPP than temperature during warm-dry extremes. Importantly, cold-dry extremes had negative impacts on regional forest NPP comparable to warm-dry extremes. Overall, our calibrated model suggests that the response of forest productivity to climate extremes is more complex than simple shift toward higher elevation. Such robust estimates of NPP are key for increasing our understanding of forests ecosystems carbon dynamics under climate extremes.
  • Gedefaw, Melakeneh G.; Geli, Hatim M. E.; Abera, Temesgen (2021)
    Rangelands provide significant socioeconomic and environmental benefits to humans. However, climate variability and anthropogenic drivers can negatively impact rangeland productivity. The main goal of this study was to investigate structural and productivity changes in rangeland ecosystems in New Mexico (NM), in the southwestern United States of America during the 1984-2015 period. This goal was achieved by applying the time series segmented residual trend analysis (TSS-RESTREND) method, using datasets of the normalized difference vegetation index (NDVI) from the Global Inventory Modeling and Mapping Studies and precipitation from Parameter elevation Regressions on Independent Slopes Model (PRISM), and developing an assessment framework. The results indicated that about 17.6% and 12.8% of NM experienced a decrease and an increase in productivity, respectively. More than half of the state (55.6%) had insignificant change productivity, 10.8% was classified as indeterminant, and 3.2% was considered as agriculture. A decrease in productivity was observed in 2.2%, 4.5%, and 1.7% of NM's grassland, shrubland, and ever green forest land cover classes, respectively. Significant decrease in productivity was observed in the northeastern and southeastern quadrants of NM while significant increase was observed in northwestern, southwestern, and a small portion of the southeastern quadrants. The timing of detected breakpoints coincided with some of NM's drought events as indicated by the self-calibrated Palmar Drought Severity Index as their number increased since 2000s following a similar increase in drought severity. Some breakpoints were concurrent with some fire events. The combination of these two types of disturbances can partly explain the emergence of breakpoints with degradation in productivity. Using the breakpoint assessment framework developed in this study, the observed degradation based on the TSS-RESTREND showed only 55% agreement with the Rangeland Productivity Monitoring Service (RPMS) data. There was an agreement between the TSS-RESTREND and RPMS on the occurrence of significant degradation in productivity over the grasslands and shrublands within the Arizona/NM Tablelands and in the Chihuahua Desert ecoregions, respectively. This assessment of NM's vegetation productivity is critical to support the decision-making process for rangeland management; address challenges related to the sustainability of forage supply and livestock production; conserve the biodiversity of rangelands ecosystems; and increase their resilience. Future analysis should consider the effects of rising temperatures and drought on rangeland degradation and productivity.
  • Salmon, Yann; Torres-Ruiz, Jose M.; Poyatos, Rafael; Martinez-Vilalta, Jordi; Meir, Patrick; Cochard, Herve; Mencuccini, Maurizio (2015)
    Understanding physiological processes involved in drought-induced mortality is important for predicting the future of forests and for modelling the carbon and water cycles. Recent research has highlighted the variable risks of carbon starvation and hydraulic failure in drought-exposed trees. However, little is known about the specific responses of leaves and supporting twigs, despite their critical role in balancing carbon acquisition and water loss. Comparing healthy (non-defoliated) and unhealthy (defoliated) Scots pine at the same site, we measured the physiological variables involved in regulating carbon and water resources. Defoliated trees showed different responses to summer drought compared with non-defoliated trees. Defoliated trees maintained gas exchange while non-defoliated trees reduced photosynthesis and transpiration during the drought period. At the branch scale, very few differences were observed in non-structural carbohydrate concentrations between health classes. However, defoliated trees tended to have lower water potentials and smaller hydraulic safety margins. While non-defoliated trees showed a typical response to drought for an isohydric species, the physiology appears to be driven in defoliated trees by the need to maintain carbon resources in twigs. These responses put defoliated trees at higher risk of branch hydraulic failure and help explain the interaction between carbon starvation and hydraulic failure in dying trees.
  • Ahopelto, Lauri; Veijalainen, Noora; Guillaume, Joseph H. A.; Keskinen, Marko; Marttunen, Mika; Varis, Olli (MDPI, 2019)
    Sustainability 2019, 11, 1548
    Severe droughts can affect water security even in countries with ample water resources. In addition, droughts are estimated to become more frequent in several regions due to changing climate. Drought affects many socio-economic sectors (e.g., agriculture, water supply, and industry), as it did in 2018 in Finland. Understanding the basin-wide picture is crucial in drought management planning. To identify vulnerable and water stressed areas in Finland, a water use-to-availability analysis was executed with a reference drought. Water stress was analyzed with the Water Depletion Index WDI. The analysis was executed using national water permits and databases. To represent a severe but realistic drought event, we modelled discharges and runoffs from the worst drought of the last century in Finland (1939–1942). The potential for performing similar analyses in data scarce contexts was also tested using estimates from global models as a screening tool. The results show that the South and Southwest of Finland would have problems with water availability during a severe drought. The most vulnerable areas would benefit from drought mitigation measures and management plans. These measures could be incorporated into the EU River Basin Management Plans.
  • Freitas, Aline A.; Drumond, Anita; Carvalho, Vanessa S. B.; Reboita, Michelle S.; Silva, Benedito C.; Uvo, Cintia B. (MDPI AG, 2022)
    Atmosphere
    The São Francisco River Basin (SFRB) is one of the main watersheds in Brazil, standing out for generating energy and consumption, among other ecosystem services. Hence, it is important to identify hydrological drought events and the anomalous climate patterns associated with dry conditions. The Standard Precipitation Index (SPI) for 12 months was used to identify hydrological drought episodes over SFRB 1979 and 2020. For these episodes, the severity, duration, intensity, and peak were obtained, and SPI-1 was applied for the longest and most severe episode to identify months with wet and dry conditions within the rainy season (Nov–Mar). Anomalous atmospheric and oceanic patterns associated with this episode were also analyzed. The results revealed the longest and most severe hydrological drought episode over the basin occurred between 2012 and 2020. The episode over the Upper portion of the basin lasted 103 months. The results showed a deficit of monthly precipitation up to 250 mm in the southeast and northeast regions of the country during the anomalous dry months identified through SPI-1. The dry conditions observed during the rainy season of this episode were associated with an anomalous high-pressure system acting close to the coast of Southeast Brazil, hindering the formation of precipitating systems.
  • Nikinmaa, Laura (Helsingin yliopisto, 2017)
    The physiological effects of drought on trees has been studied excessively but many of them remain unclear. In this thesis I studied tree sugar dynamics under drying-wetting cycle as well as the role of soil hydraulic conductivity on how trees experience drought. I experimented with five Norway spruce seedlings in October and November 2016. The seedlings were in water after which they were put in to PEG solution of -0.5 MPa for 24 h and then transferred back to water. Sugar samples were taken from liquids, needles and roots once for every phase. Osmolality samples were taken from current year needles and water potential samples were taken from current year needles and roots every half an hour during day time. Continuous gas exchange measurements were done with Walz GFS-3000. There was no change in osmolality and no significant change in photosynthesis or transpiration rate. For sugar concentrations there was significant increase of non-structural carbohydrates in needles and significant decrease in roots. There was no change in sugar concentration in liquid. Overall impression was that trees did not suffer much from the PEG treatment. The results supported my hypothesis that changes in soil hydraulic conductivity are more important to effects of drought than changes in soil water potential.
  • Khazaei, Hamid; Santanen, Arja; Street, Kenneth; Stoddard, Frederick L. (2019)
    Among grain legumes, faba bean is reputed to be relatively sensitive to drought stress. Epicuticular wax (ECW) quantity is considered as an important drought adaptation strategy in plant species. This study aimed to define variation in leaf ECW concentration as a drought-adaptive trait in 197 faba bean accessions under well-watered conditions. The relationship between ECW and stomatal characteristics was also investigated. Highly significant differences were found in the ECW concentration, which ranged from 0.680 to 2.104 mg/dm(2). No relationships were found between ECW and any measure of stomatal morphology and function. This study provides evidence of the wide variation in ECW in faba bean germplasm, which is independent of stomatal characteristics and leaf water content. This variation may allow the genetic improvement of ECW as a drought-adaptive character in faba bean breeding programs aiming at the economical use of water.
  • Singh, Jaswinder; Cameron, Erin; Reitz, Thomas; Schädler, Martin; Eisenhauer, Nico (2021)
    Abstract The impacts of climate change on biodiversity can be modulated by other changing environmental conditions, e.g. induced by land-use change. The potential interactive effects of climate change and land use have rarely been studied for soil organisms. To test the effects of changing climatic conditions and land use on soil invertebrates, we examined earthworm communities across different seasons in different grassland-use types (intensively managed grassland, extensively managed meadow, and extensively managed sheep pasture).We predicted that the strength of climate change effects would vary with season and land use. Overall, extracted earthworm populations showed the strongest variations in response to the season, indicating major differences in activity patterns and extraction efficiency, while climate change and different grassland-use types had fewer and weaker effects. Future climate, characterized by slightly higher precipitation in spring and fall but a strong reduction during the summer, had positive effects on the abundance of extracted adult earthworms in spring but then reduced the abundance of active earthworms across the remaining seasons. In contrast, the total biomass of juveniles tended to be consistently lower under future climate conditions. Earthworm species responded differently to the climate change and different grassland management types, and these species-specific responses further varied strongly across seasons. Intensive grassland management had negative effects, due to plant community composition, while sheep grazing favoured earthworm populations, due to dung deposition. There were only limited interactive effects between climate and land use, which thus did not support our main hypothesis. Nevertheless, these results highlight the complex and context-dependent responses of earthworm communities and activity patterns to climate change, with potential consequences for long-term population dynamics and crucial ecosystem functions. This article is protected by copyright. All rights reserved.
  • Truchy, Amélie; Sarremejane, Romain; Muotka, Timo; Mykrä, Heikki; Angeler, David G.; Lehosmaa, Kaisa; Huusko, Ari; Johnson, Richard K.; Sponseller, Ryan A.; McKie, Brendan G. (Wiley Online Library, 2020)
    Global Change Biology 26 6 (2020)
    Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post-drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (a) algal biomass accrual; (b) microbial respiration; and (c) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An 8-day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal dieback began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short-term droughts can have extended consequences for stream ecosystems in the world's vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms.
  • Truchy, Amélie; Sarremejane, Romain; Muotka, Timo; Mykrä, Heikki; Angeler, David G.; Lehosmaa, Kaisa; Huusko, Ari; Johnson, Richard K.; Sponseller, Ryan A.; McKie, Brendan G. (Wiley, 2020)
    Global Change Biology 26 6 (2020)
    Ongoing climate change is increasing the occurrence and intensity of drought episodes worldwide, including in boreal regions not previously regarded as drought prone, and where the impacts of drought remain poorly understood. Ecological connectivity is one factor that might influence community structure and ecosystem functioning post-drought, by facilitating the recovery of sensitive species via dispersal at both local (e.g. a nearby habitat patch) and regional (from other systems within the same region) scales. In an outdoor mesocosm experiment, we investigated how impacts of drought on boreal stream ecosystems are altered by the spatial arrangement of local habitat patches within stream channels, and variation in ecological connectivity with a regional species pool. We measured basal ecosystem processes underlying carbon and nutrient cycling: (a) algal biomass accrual; (b) microbial respiration; and (c) decomposition of organic matter, and sampled communities of aquatic fungi and benthic invertebrates. An 8-day drought event had strong impacts on both community structure and ecosystem functioning, including algal accrual, leaf decomposition and microbial respiration, with many of these impacts persisting even after water levels had been restored for 3.5 weeks. Enhanced connectivity with the regional species pool and increased aggregation of habitat patches also affected multiple response variables, especially those associated with microbes, and in some cases reduced the effects of drought to a small extent. This indicates that spatial processes might play a role in the resilience of communities and ecosystem functioning, given enough time. These effects were however insufficient to facilitate significant recovery in algal growth before seasonal dieback began in autumn. The limited resilience of ecosystem functioning in our experiment suggests that even short-term droughts can have extended consequences for stream ecosystems in the world's vast boreal region, and especially on the ecosystem processes and services mediated by algal biofilms.
  • Lopez, Jose Gutierrez; Tor-Ngern, Pantana; Oren, Ram; Kozii, Nataliia; Laudon, Hjalmar; Hasselquist, Niles J. (2021)
    Trees in northern latitude ecosystems are projected to experience increasing drought stress as a result of rising air temperatures and changes in precipitation patterns in northern latitude ecosystems. However, most drought-related studies on high-latitude boreal forests (>50 degrees N) have been conducted in North America, with few studies quantifying the response in European and Eurasian boreal forests. Here, we tested how daily whole-tree transpiration (Q, Liters day(-1)) and Q normalized for mean daytime vapor pressure deficit (Q(DZ), Liters day(-1) kPa(-1)) were affected by the historic 2018 drought in Europe. More specifically, we examined how tree species, size, and topographic position affected drought response in high-latitude mature boreal forest trees. We monitored 30 Pinus sylvestris (pine) and 30 Picea abies (spruce) trees distributed across a topographic gradient in northern Sweden. In general, pine showed a greater Q(DZ) control compared to spruce during periods of severe drought (standardized precipitation-evapotranspiration index: SPEI <-1.5), suggesting that the latter are more sensitive to drought. Overall, Q(DZ) reductions (using non-drought Q(DZ) as reference) were less pronounced in larger trees during severe drought, but there was a species-specific pattern: Q(DZ) reductions were greater in pine trees at high elevations and greater in spruce trees at lower elevations. Despite lower Q(DZ) during severe drought, drought spells were interspersed with small precipitation events and overcast conditions, and Q(DZ) returned to pre-drought conditions relatively quickly. This study highlights unique species-specific responses to drought, which are additionally driven by a codependent interaction among tree size, relative topographic position, and unique regional climate conditions.
  • Gao, Yao (2016)
    Finnish Meteorological Institute Contributions 124
    Interactions between the land surface and climate are complex as a range of physical, chemical and biological processes take place. Changes in the land surface or the climate can affect the water, energy and carbon cycles in the Earth system. This thesis discusses a number of critical issues that concern land-atmospheric interactions in the boreal zone, which is characterised by vast areas of peatlands, extensive boreal forests and a long snow cover period. Regional climate modelling and land surface modelling were used as the main tools for this study, in conjunction with observational data for evaluation. First, to better describe the present-day land cover in the regional climate model, we introduced an up-to-date and high-resolution land cover map to replace the inaccurate and outdated default land cover map for Fennoscandia. Second, in order to provide background information for future forest anagement actions for climate change mitigation, we studied the biogeophysical effects on the regional climate of peatland forestation, which has been the dominant land cover change in Finland over the last century. Moreover, climate variability can influence the land surface. Although drought is uncommon in northern Europe, an extreme drought occurred in the summer of 2006 in Finland, and induced visible drought symptoms in boreal forests. Thus, we assessed a set of drought indicators with drought impact data in boreal forests in Finland to indicate summer drought in boreal forests. Finally, the impacts of summer drought on water use efficiency of boreal Scots pine forests were studied to gain a deeper understanding of carbon and water dynamics in boreal forest ecosystems. In summary, the key findings of this thesis include: 1) the updated land cover map led to a slight decrease in biases of the simulated climate conditions. It is expected that the model performance could be improved by further development in model physics. 2) Peatland forestation in Finland can induce a warming effect in the spring of up to 0.43 K and a slight cooling effect in the growing season of less than 0.1 K due to decreased surface albedo and increased evapotranspiration, respectively. Corresponding to spring warming, the snow clearance day was advanced by up to 5 days over a 15-year mean. 3) The soil moisture index SMI was the most capable of the assessed drought indicators in capturing the spatial extent of observed forest damage induced by the extreme drought in 2006 in Finland. Thus, a land surface model capable of reliable predictions of regional soil moisture is important in future drought predictions in the boreal zone. 4) The inherent water use efficiency (IWUE) showed an increase during drought at the ecosystem level, and IWUE was found to be more appropriate than the ecosystem water use efficiency (EWUE) in indicating the impacts of drought on ecosystem functioning. The combined effects of soil moisture drought and atmospheric drought on stomatal conductance have to be taken into account in land surface models at the global scale when simulating the drought effects on plant functioning.
  • Junttila, Samuli; Kaasalainen, Sanna; Vastaranta, Mikko; Hakala, Teemu; Nevalainen, Olli; Holopainen, Markus (2015)
    Global warming is posing a threat to the health and condition of forests as the amount and length of biotic and abiotic disturbances increase. Most methods for detecting disturbances and measuring forest health are based on multi- and hyperspectral imaging. We conducted a test with spruce and pine trees using a hyperspectral Lidar instrument in a laboratory to determine the capability of combined range and reflectance measurements to investigate forest health. A simple drought treatment was conducted by leaving the harvested trees outdoors without a water supply for 12 days. The results showed statistically significant variation in reflectance after the drought treatment for both species. However, the changes differed between the species, indicating that drought-induced alterations in spectral characteristics may be species-dependent. Based on our results, hyperspectral Lidar has the potential to detect drought in spruce and pine trees.
  • Salmon, Yann; Lintunen, Anna; Dayet, Alexia; Chan, Tommy; Dewar, Roderick; Vesala, Timo; Holtta, Teemu (2020)
    Photosynthetic rate is concurrently limited by stomatal limitations and nonstomatal limitations (NSLs). However, the controls on NSLs to photosynthesis and their coordination with stomatal control on different timescales remain poorly understood. According to a recent optimization hypothesis, NSLs depend on leaf osmotic or water status and are coordinated with stomatal control so as to maximize leaf photosynthesis. Drought and notching experiments were conducted on Pinus sylvestris, Picea abies, Betula Pendula and Populus tremula seedlings in glasshouse conditions to study the dependence of NSLs on leaf osmotic and water status, and their coordination with stomatal control, on timescales of minutes and weeks, to test the assumptions and predictions of the optimization hypothesis. Both NSLs and stomatal conductance followed power-law functions of leaf osmotic concentration and leaf water potential. Moreover, stomatal conductance was proportional to the square root of soil-to-leaf hydraulic conductance, as predicted by the optimization hypothesis. Though the detailed mechanisms underlying the dependence of NSLs on leaf osmotic or water status lie outside the scope of this study, our results support the hypothesis that NSLs and stomatal control are coordinated to maximize leaf photosynthesis and allow the effect of NSLs to be included in models of tree gas-exchange.
  • Fang, Keyan; Frank, David; Zhao, Yan; Zhou, Feifei; Seppä, Heikki (2015)
    Investigations of climate-growth interactions can shed light on the response of forest growth to climate change and the dendroclimatic reconstructions. However, most existing studies in the climatically important Tibetan Plateau (TP) and surrouding regions focus on linear growth responses to environmental variation. Herein we investigated both the linear and the nonlinear climate-growth interactions for 152 tree-ring chronologies in the TP and vicinity. Weintroduced the boosted regression tree (BRT) technique to study the nonlinear climate-growth relationships by pooling several sites with similar climate-growth relationships to mitigate potential biases due to the shortness of the instrumental records. Across most of the TP and surroundings, tree growth is stressed by drought. The warming induced drought has been evidenced by the strong interactions between temperature and precipitation in the BRT analyses. The drought stress on forest growth is particularly conspicuous for a hydrological year over much of the Northern TP and surroundings. The BRT analyses indicate the compensation effect of moisture prior to the growing season for the moisture deficit in the early growing season in May to July, when most of the ring-width formation occurs.
  • Kasimir, Å; He, H.; Jansson, P-E; Lohila, A.; Minkkinen, K. (2021)
    Nutrient-rich peat soils have previously been demonstrated to lose carbon despite higher photosynthesis and litter production compared to nutrient-poor soils, where instead carbon accumulates. To understand this phenomenon, we used a process-oriented model (CoupModel) calibrated on data from two closely located drained peat soil sites in boreal forests in Finland, Kalevansuo and Lettosuo, with different soil C/N ratios. Uncertainty-based calibrations were made using eddy-covariance data (hourly values of net ecosystem exchange) and tree growth data. The model design used two forest scenarios on drained peat soil, one nutrient-poor with dense moss cover and another with lower soil C/N ratio with sparse moss cover. Three vegetation layers were assumed: conifer trees, other vascular plants, and a bottom layer with mosses. Adding a moss layer was a new approach, because moss has a modified physiology compared to vascular plants. The soil was described by three separate soil organic carbon (SOC) pools consisting of vascular plants and moss litter origin and decomposed organic matter. Over 10 years, the model demonstrated a similar photosynthesis rate for the two scenarios, 903 and 1,034 g C m(-2) yr(-1), for the poor and rich site respectively, despite the different vegetation distribution. For the nutrient-rich scenario more of the photosynthesis produce accumulated as plant biomass due to more trees, while the poor site had abundant moss biomass which did not increase living aboveground biomass to the same degree. Instead, the poor site showed higher litter inputs, which compared with litter from vascular plants had low turnover rates. The model calibration showed that decomposition rate coefficients for the three SOC pools were similar for the two scenarios, but the high quantity of moss litter input with low decomposability for the nutrient poor scenario explained the major difference in the soil carbon balance. Vascular plant litter declined with time, while SOC pools originating from mosses accumulated with time. Large differences between the scenarios were obtained during dry spells where soil heterotrophic respiration doubled for the nutrient-rich scenario, where vascular plants dominated, owing to a larger water depletion by roots. Where moss vegetation dominated, the heterotrophic respiration increased by only 50% during this dry period. We suggest moss vegetation is key for carbon accumulation in the poor soil, adding large litter quantities with a resistant quality and less water depletion than vascular plants during dry conditions.
  • Aakala, Tuomas; Pasanen, Leena; Helama, Samuli; Vakkari, Ville; Drobyshev, Igor; Seppa, Heikki; Kuuluvainen, Timo; Stivrins, Normunds; Wallenius, Tuomo; Vasander, Harri; Holmstrom, Lasse (2018)
    Forest fires are a key disturbance in boreal forests, and characteristics of fire regimes are among the most important factors explaining the variation in forest structure and species composition. The occurrence of fire is connected with climate, but earlier, mostly local-scale studies in the northern European boreal forests have provided little insight into fire-climate relationship before the modern fire suppression period. Here, we compiled annually resolved fire history, temperature, and precipitation reconstructions from eastern Fennoscandia from the mid-16th century to the end of the 19th century, a period of strong human influence on fires. We used synchrony of fires over the network of 25 fire history reconstructions as a measure of climatic forcing on fires. We examined the relationship between fire occurrence and climate (summer temperature, precipitation, and a drought index summarizing the influence of variability in temperature and precipitation) across temporal scales, using a scale space multiresolution correlation approach and Bayesian inference that accounts for the annually varying uncertainties in climate reconstructions. At the annual scale, fires were synchronized during summers with low precipitation, and most clearly during drought summers. A scale-derivative analysis revealed that fire synchrony and climate varied at similar, roughly decadal scales. Climatic variables and fire synchrony showed varying correlation strength and credibility, depending on the climate variable and the time period. In particular, precipitation emerged as a credible determinant of fire synchrony also at these time scales, despite the large uncertainties in precipitation reconstruction. The findings explain why fire occurrence can be high during cold periods (such as from the mid-17th to early-18th century), and stresses the notion that future fire frequency will likely depend to a greater extent on changes in precipitation than temperature alone. We showed, for the first time, the importance of climate as a decadal-scale driver of forest fires in the European boreal forests, discernible even during a period of strong human influence on fire occurrence. The fire regime responded both to anomalously dry summers, but also to decadal-scale climate changes, demonstrating how climatic variability has shaped the disturbance regimes in the northern European boreal forests over various time scales.
  • Salgado, Ana; DiLeo, Michelle; Saastamoinen, Marjo (2020)
    1. Understanding species' habitat preferences are crucial to predict organisms' responses to the current climate crisis. In many insects, maternal habitat selection for oviposition essentially determines offspring performance. Whether future changes in climatic conditions may generate mismatches between oviposition preference and offspring performance, when mothers continue to prefer microhabitats that might threaten offspring survival, is an open question. 2. To address this gap, we tested if oviposition preferences of the Glanville fritillary butterfly Melitaea cinxia females put offspring at risk when plants are under drought stress conditions. Mainly, we focus on identifying the microhabitat determinants for oviposition and the variation of conditions experienced by the sessile offspring, using field observations from 12 populations collected over 2015–2018. These data are combined with 10 years of larval nest and precipitation data to understand within-population patterns of habitat selection. We tested whether the preferred microhabitats maximized the extended larval performance (i.e. overwinter survival). 3. We found that females preferentially oviposited in microhabitats with higher host plant abundance and higher proportion of host plants with signs of drought stress. In most years, larval nests had higher survival in these drought-stressed microhabitats. However, in an extremely dry year, only two nests survived over the summer. 4. Our results highlight that a failure to shift habitat preference under extreme climate conditions may have drastic consequences for the survival of natural populations under changing climatic conditions.
  • Muktadir, Md Abdul; Adhikari, Kedar Nath; Merchant, Andrew; Belachew, Kiflemariam; Vandenberg, Albert; Stoddard, Fred; Khazaei, Hamid (2020)
    Grain legumes are commonly used for food and feed all over the world and are the main source of protein for over a billion people worldwide, but their production is at risk from climate change. Water deficit and heat stress both significantly reduce the yield of grain legumes, and the faba bean is considered particularly susceptible. The genetic improvement of faba bean for drought adaptation (water deficit tolerance) by conventional methods and molecular breeding is time-consuming and laborious, since it depends mainly on selection and adaptation in multiple sites. The lack of high-throughput screening methodology and low heritability of advantageous traits under environmental stress challenge breeding progress. Alternatively, selection based on secondary characters in a controlled environment followed by field trials is successful in some crops, including faba beans. In general, measured features related to drought adaptation are shoot and root morphology, stomatal characteristics, osmotic adjustment and the efficiency of water use. Here, we focus on the current knowledge of biochemical and physiological markers for legume improvement that can be incorporated into faba bean breeding programs for drought adaptation.
  • Aserse, Aregu; Markos, Daniel; Getachew, Genet; Yli-Halla, Markku; Lindström, Kristina (2020)
    While pulses are staple food-legumes in Ethiopia, their productivity is low due to low soil fertility. Elite rhizobial strains that significantly increased shoot dry weight and nitrogen (N) contents of common beans and soybeans in greenhouse were selected for two-year field trials to evaluate their effect on yields of the pulses in the field. Each pulse had six treatments, namely four rhizobial inoculants, uninoculated control, and synthetic N fertilizer. In the drought-affected year 2015, inoculated pulses tolerated moisture stress better than non-inoculated controls. Inoculation was conducive to higher or equivalent yields compared to synthetic N fertilizer. At Halaba, bean inoculated with strain HAMBI3562 gave the highest grain yield (1500 ± 81 kg ha−1; mean±SE) while the control yielded only 653 ± 22 kg ha−1. At Boricha, HAMBI3570 gave a grain yield (640 ± 35 kg ha−1) comparable to synthetic N. When rainfall was optimal in 2016, inoculation with HAMBI3562 and HAMBI3570 gave grain yields (around 4300 kg ha−1) equivalent to synthetic N. With soybean, strain HAMBI3513 produced consistently higher or comparable biomass and grain yields compared to synthetic N. In conclusion, HAMBI3562 and HAMBI3570 for beans and HAMBI3513 for soybeans can serve as inoculants for areas having similar conditions as the test areas.