The importance of monsoon precipitation for foundation tree species across the semiarid Southwestern U.S.

Forest dynamics in arid and semiarid regions are sensitive to water availability, which is becoming increasingly scarce as global climate changes. The timing and magnitude of precipitation in the semiarid southwestern U.S. (“Southwest”) has changed since the 21st century began. The region is projected to become hotter and drier as the century proceeds, with implications for carbon storage, pest outbreaks, and wildfire resilience. Our goal was to quantify the importance of summer monsoon precipitation for forested ecosystems across this region. We developed an isotope mixing model in a Bayesian framework to characterize summer (monsoon) precipitation soil water recharge and water use by three foundation tree species (Populus tremuloides [aspen], Pinus edulis [piñon], and Juniperus osteosperma [Utah juniper]). In 2016, soil depths recharged by monsoon precipitation and tree reliance on monsoon moisture varied across the Southwest with clear differences between species. Monsoon precipitation recharged soil at piñon-juniper (PJ) and aspen sites to depths of at least 60 cm. All trees in the study relied primarily on intermediate to deep (10-60 cm) moisture both before and after the onset of the monsoon. Though trees continued to primarily rely on intermediate to deep moisture after the monsoon, all species increased reliance on shallow soil moisture to varying degrees. Aspens increased reliance on shallow soil moisture by 13% to 20%. Utah junipers and co-dominant ñons increased their reliance on shallow soil moisture by about 6% to 12%. Nonetheless, approximately half of the post-monsoon moisture in sampled piñon (38-58%) and juniper (47-53%) stems could be attributed to the monsoon. The monsoon contributed lower amounts to aspen stem water (24-45%) across the study area with the largest impacts at sites with recent precipitation. Therefore, monsoon precipitation is a key driver of growing season moisture that semiarid forests rely on across the Southwest. This monsoon reliance is of critical importance now more than ever as higher global temperatures lead to an increasingly unpredictable and weaker North American Monsoon

Local political marketing in the context of the conservative party

Local political marketing can be defined as marketing related strategy, activities, and tactics implemented by a political party in a local geographic constituency, in order to attempt to maximise aggregate potential voter satisfaction, and therefore maximise total number of votes and electoral support in the constituency. Through 12 in-depth interviews with Local Constituency Party representatives from the Conservative Party, the study found that local political marketing was acknowledged by a majority of respondents although this was not unequivocal, and was frequently conflated with campaigning. Local political marketing was associated with: visual identity, language/messages, values, image, communication devices, awareness raising, data management and targeting, and simplification. The support from higher levels of the party in local political marketing was varied across constituencies. There was evidence of growing coordination /influence by higher levels of the party in local political marketing. However, this tended to be in seats judged as ‘winnable’

Altered climate memory characterizes tree growth during forest dieback

© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Warming temperatures and droughts are driving widespread forest dieback and growth decline worldwide. In forests experiencing dieback, declining trees may exhibit altered climate memory of growth, indicative of physiological impairment. Thus, we evaluated climate-growth responses of trees in four drought-disturbed forests dominated either by gymnosperms (Abies alba, Pinus sylvestris) or angiosperms (Fagus sylvatica, Quercus humilis) in Northern Spain, where we compared responses of declining (heavily defoliated) and non-declining (slightly or not defoliated) trees. To disentangle the effects of forest dieback and past climate on tree growth, we applied the stochastic antecedent modeling (SAM) framework to annual tree-ring widths to quantify climatic memory. Declining trees had lower recent growth than non-declining conspecifics. All species responded positively to precipitation and temperature, independent of their vigor class, except for declining silver fir (A. alba) and European beech (F. sylvatica) individuals, which showed a negative effect of warmer temperatures on growth. Declining trees of these two species were also more sensitive to recent temperature and precipitation conditions, whilst climatic conditions further into the past were more important for non-declining trees. Silver fir and European beech from both vigor classes were also coupled to climate conditions during markedly different seasons, with dry summer conditions particularly affecting declining trees. Declining and non-declining Scots pine (P. sylvetris) and pubescent oak (Q. humilis) trees did not show different responses to past climate. While drought-triggered dieback differentially impacted silver fir and European beech individuals, Scots pine and pubescent oak trees suffered from a chronic process of loss in tree growth and vigor. Our results highlight the differences in climate sensitivity and climate memory of tree growth in forests experiencing ongoing dieback.We acknowledge funding provided by projects FUNDIVER (CGL2015–69186-C2–1-R and CGL2015–69186-C2–2-R projects) and FORMAL (RTI2018–096884-B-C31 and RTI2018–096884-B-C32) from the Spanish Ministry of Science and Innovation. We thank the interest and guidance of J.M. Vadillo and Estella forest guards (Navarra Govt.) and the help in the field and the lab of M. Colangelo. We acknowledge the E-OBS dataset from the EU-FP6 project UERRA (http://www.uerra.eu) and the Copernicus Climate Change Service, and the data providers in the ECAD project (https://www.ecad.eu). K. Ogle acknowledges the support of the National Science Foundation, Advances in Biological Informatics program (grant #1458867).Peer reviewe

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’), which also experienced widespread regional drought 5 years earlier. We used an incubation method to measure the radiocarbon (Δ14C) in CO2 respired from Populus tremuloides Michx. (aspen) tree rings to evaluate NSC storage and mixing patterns, coupled with measurements of NSC (soluble sugars and starch) concentrations and respired δ13C-CO2. At a wet site, CO2 respired from rings formed during 1962–67 was only ~11 years old, suggesting deep sapwood mixing of NSCs as starch. At a dry site, the 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 and 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 (\u3c 1 year) in the most recent six rings, indicative of deep radial mixing following relatively wet conditions during the sampling year. We suggest that the 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 south-western USA 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

Gross primary production responses to warming, elevated CO 2 , and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland

Determining whether the terrestrial biosphere will be a source or sink of carbon (C) under a future climate of elevated CO2 (eCO2) and warming requires accurate quantification of gross primary production (GPP), the largest flux of C in the global C cycle. We evaluated 6 years (2007–2012) of flux-derived GPP data from the Prairie Heating and CO2 Enrichment (PHACE) experiment, situated in a grassland in Wyoming, USA. The GPP data were used to calibrate a light response model whose basic formulation has been successfully used in a variety of ecosystems. The model was extended by modeling maximum photosynthetic rate (Amax) and light-use efficiency (Q) as functions of soil water, air temperature, vapor pressure deficit, vegetation greenness, and nitrogen at current and antecedent (past) timescales. The model fits the observed GPP well (R2 = 0.79), which was confirmed by other model performance checks that compared different variants of the model (e.g. with and without antecedent effects). Stimulation of cumulative 6-year GPP by warming (29%, P = 0.02) and eCO2 (26%, P = 0.07) was primarily driven by enhanced C uptake during spring (129%, P = 0.001) and fall (124%, P = 0.001), respectively, which was consistent across years. Antecedent air temperature (Tairant) and vapor pressure deficit (VPDant) effects on Amax (over the past 3–4 days and 1–3 days, respectively) were the most significant predictors of temporal variability in GPP among most treatments. The importance of VPDant suggests that atmospheric drought is important for predicting GPP under current and future climate; we highlight the need for experimental studies to identify the mechanisms underlying such antecedent effects. Finally, posterior estimates of cumulative GPP under control and eCO2 treatments were tested as a benchmark against 12 terrestrial biosphere models (TBMs). The narrow uncertainties of these data-driven GPP estimates suggest that they could be useful semi-independent data streams for validating TBMs.This material is based upon work supported by the US Department of Agriculture, Agricultural Research Service Climate Change, Soils & Emissions Program, USDA-CSREES Soil Processes Program (#2008-35107-18655), US Department of Energy Office of Science (BER), through the Terrestrial Ecosystem Science program (#DE-SC0006973), and the Western Regional Center of the National Institute for Climatic Change Research, and by the National Science Foundation (DEB#1021559). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. We thank D. LeCain, J.A. Morgan, J. Heisler-White, A. Brennan, S. Bachman, Y. Sorokin, T.J. Zelikova, D. Blumenthal, K. Mueller, and numerous others for assistance in data collection and operation of PHACE facilities, and B. Yang for use of his gap-filled meteorological data at the site. We also thank D. Kinsman for his helpful comments on the discussion sectio

The importance of monsoon precipitation for foundation tree species across the semiarid Southwestern U.S.

Abstract Forest dynamics in arid and semiarid regions are sensitive to water availability, which is becoming increasingly scarce as global climate changes. The timing and magnitude of precipitation in the semiarid southwestern U.S. (“Southwest”) has changed since the 21st century began. The region is projected to become hotter and drier as the century proceeds, with implications for carbon storage, pest outbreaks, and wildfire resilience. Our goal was to quantify the importance of summer monsoon precipitation for forested ecosystems across this region. We developed an isotope mixing model in a Bayesian framework to characterize summer (monsoon) precipitation soil water recharge and water use by three foundation tree species (Populus tremuloides [aspen], Pinus edulis [piñon], and Juniperus osteosperma [Utah juniper]). In 2016, soil depths recharged by monsoon precipitation and tree reliance on monsoon moisture varied across the Southwest with clear differences between species. Monsoon precipitation recharged soil at piñon-juniper (PJ) and aspen sites to depths of at least 60 cm. All trees in the study relied primarily on intermediate to deep (10–60 cm) moisture both before and after the onset of the monsoon. Though trees continued to primarily rely on intermediate to deep moisture after the monsoon, all species increased reliance on shallow soil moisture to varying degrees. Aspens increased reliance on shallow soil moisture by 13% to 20%. Utah junipers and co-dominant ñons increased their reliance on shallow soil moisture by about 6% to 12%. Nonetheless, approximately half of the post-monsoon moisture in sampled piñon (38–58%) and juniper (47–53%) stems could be attributed to the monsoon. The monsoon contributed lower amounts to aspen stem water (24–45%) across the study area with the largest impacts at sites with recent precipitation. Therefore, monsoon precipitation is a key driver of growing season moisture that semiarid forests rely on across the Southwest. This monsoon reliance is of critical importance now more than ever as higher global temperatures lead to an increasingly unpredictable and weaker North American Monsoon