Carlos A. Gonzalez-Benecke

Water availability and genetic effects on water relations of loblolly pine (Pinus taeda) stands.

The effect of water availability on water relations of 11-year-old loblolly pine stands was studied over two growing seasons in material from two contrasting seed sources. Increasing soil water availability via irrigation increased transpiration rate, and maximum daily transpiration rate on irrigated plots was similar for both seasons, reaching values of 4.3 mm day(-)(1). Irrigation also changed soil water extraction patterns. In the rain-fed control plots, 73% of the average daily transpiration was extracted from the upper 0.75 m of the soil profile. Under irrigated conditions, 92% of transpired water was extracted from the upper 0.75 m of soil, with 79% of transpired water coming from the upper 0.35 m of the profile; only 10% of total transpiration in this treatment was extracted from the soil below 1 m. There was an irrigation x seed source interaction in the response of canopy conductance to water vapor (G(C)) to vapor pressure deficit (D). Under water-limited conditions, trees from the South Carolina seed source (SC) had stronger stomatal control than trees from the Florida seed source (FL), but this difference was not present when water was not limiting. The transpiration-induced water potential gradient from roots to shoots (DeltaPsi) was relatively constant across treatments (P = 0.52) and seed sources (P = 0.72), averaging 0.75 MPa. This reflects strong stomatal control that maintains relatively constant DeltaPsi but at the same time allows leaf water potential (Psi(l)) to fluctuate dramatically in synchrony with soil water potential (Psi(s)). The two seed sources evaluated also showed differences in foliar N and delta(13)C, possibly reflecting differences in adaptation to ambient humidity and water availability regimes in their respective ranges. These differences among seed sources under different water availability scenarios may be informative to natural resource managers and breeders as they design tree improvement and genetic deployment programs for future climate scenarios. For example, the increased stomatal control of SC under decreased soil moisture availability may make this taxon a more conservative deployment choice than FL under future, drier climate scenarios but perhaps at the risk of lower productivity.

Estimating Pinus palustris tree diameter and stem volume from tree height, crown area and stand-level parameters

Accurate and efficient estimation of forest growth and live biomass is a critical element in assessing potential responses to forest management and environmental change. The objective of this study was to develop models to predict longleaf pine tree diameter at breast height (dbh) and merchantable stem volume (V) using data obtained from field measurements. We used longleaf pine tree data from 3,376 planted trees on 127 permanent plots located in the U.S. Gulf Coastal Plain region to fit equations to predict dbh and V as functions of tree height (H) and crown area (CA). Prediction of dbh as a function of H improved when CA was added as an additional independent variable. Similarly, predictions of V based on H improved when CA was included. Incorporation of additional stand variables such as age, site index, dominant height, and stand density were also evaluated but resulted in only small improvements in model performance. For model testing we used data from planted and naturally-regenerated trees located inside and outside the geographic area used for model fitting. Our results suggest that the models are a robust alternative for dbh and V estimations when H and CA are known on planted stands with potential for naturally-regenerated stands, across a wide range of ages. We discuss the importance of these models for use with metrics derived from remote sensing data.

Hydraulic architecture and tracheid allometry in mature Pinus palustris and Pinus elliottii trees

Pinus palustris Mill. (longleaf pine, LL) and Pinus elliottii Engelm. var. elliottii (slash pine, SL) frequently co-occur in lower coastal plain flatwoods of the USA, with LL typically inhabiting slightly higher and better-drained microsites than SL. The hydraulic architecture and tracheid dimensions of roots, trunk and branches of mature LL and SL trees were compared to understand their role in species microsite occupation. Root xylem had higher sapwood-specific hydraulic conductivity (k(s)) and was less resistant to cavitation compared with branches and trunk sapwood. Root k(s) of LL was significantly higher than SL, whereas branch and trunk k(s) did not differ between species. No differences in vulnerability to cavitation were observed in any of the organs between species. Across all organs, there was a significant but weak trade-off between water conduction efficiency and safety. Tracheid hydraulic diameter (D(h)) was strongly correlated with k(s) across all organs, explaining >73% of the variation in k(s). In contrast, tracheid length (L(t)) explained only 2.4% of the variability. Nevertheless, for trunk xylem, k(s) was 39.5% higher at 20 m compared with 1.8 m; this increase in k(s) was uncorrelated with D(h) and cell-wall thickness but was strongly correlated with the difference in L(t). Tracheid allometry markedly changed between sapwood of roots, trunks and branches, possibly reflecting different mechanical constraints. Even though vulnerability to cavitation was not different for sapwood of roots, branches or the trunks of LL and SL, higher sapwood to leaf area ratio and higher maximum sapwood-specific hydraulic conductivity in roots of LL are functional traits that may provide LL with a competitive advantage on drier soil microsites.

Imputation of individual Longleaf Pine (Pinus palustris Mill.) Tree attributes from field and LiDAR data

Abstract Light Detection and Ranging (LiDAR) has demonstrated potential for forest inventory at the individual-tree level. The aim in this study was to predict individual-tree height (Ht; m), basal area (BA; m2), and stem volume (V; m3) attributes, imputing Random Forest k-nearest neighbor (RF k-NN) and individual-tree-level-based metrics extracted from a LiDAR-derived canopy height model (CHM) in a longleaf pine (Pinus palustris Mill.) forest in southwestern Georgia, United States. We developed a new framework for modeling tree-level forest attributes that comprise 3 steps: (i) individual tree detection, crown delineation, and tree-level-based metrics computation from LiDAR-derived CHM; (ii) automatic matching of LiDAR-derived trees and field-based trees for a regression modeling step using a novel algorithm; and (iii) RF k-NN imputation modeling for estimating tree-level Ht, BA, and V and subsequent summarization of these metrics at the plot and stand levels. RMSDs for tree-level Ht, BA, and V were 2.96%, 58.62%, and 8.19%, respectively. Although BA estimation accuracy was poor because of the longleaf pine growth habitat, individual-tree locations, Ht, and V were estimated with high accuracy, especially in low-canopy-cover conditions. Future efforts based on the findings could help improve the estimation accuracy of individual-tree-level attributes such as BA.

Automated quantification of intra-annual density fluctuations using microdensity profiles of mature Pinus taeda in a replicated irrigation experiment

Key messageWe developed a new automated method to use wood microdensity profiles to detect and quantify intra-annual wood density fluctuations in earlywood of pine trees.AbstractWe developed a new, automated method to use X-ray wood microdensity profiles to detect and quantify intra-annual density fluctuations within the earlywood region (IADFe) of each annual growth ring. The method quantifies the number and area of IADFe by detecting variations in wood density beyond the limits of “normal” values observed during periods without environmental stress. As a case study, we examined the effect of water availability and water stress associated with the formation of IADFe in irrigated and non-irrigated 11-year-old loblolly pine trees. As expected, non-irrigated trees formed significantly more IADFe than irrigated trees. Strong relationships were observed between IADFe formation (as a proportion of total earlywood area or as the number of IADFe formed each year) and the minimum monthly Palmer Drought Severity Index for the earlywood growing season (February to July). When compared against visual detection, the number of IADFe detected optically was significantly fewer than the number detected with densitometry. This difference likely comes from the higher resolution and more objective criteria that confidently detected and counted more very small IADFe than was possible optically at 10× magnification. The method to detect and quantify IADFe described in this study can allow climate analysis in long-lived species prone to producing intra-annual growth zones and false rings.

Forest regeneration in changing environments

Successfully regenerating young forests following harvesting or natural disturbances is the first principle of sustainable forest management. Whether regeneration practices are successful or not can have substantial long-term effects on future stand dynamics, management options, and whether overall goals are achieved. Continuously adapting forest regeneration practices to changing societal needs, human and natural disturbances, policies, markets, technologies and climate, presents recurring challenges and opportunities to successfully managing forests around the globe. Therefore, testing new methods for regenerating forests is vital for meeting current and future forest management goals and ensuring the overall sustainability of forests. Advancing the science and practice of forest regeneration and early stand management requires a regular exchange of information about new concepts, scientific methodologies, and technologies among forest researchers and managers. From July 11–13, 2017 an international conference entitled Forest Regeneration in Changing Environments was held at Oregon State University in Corvallis, OR, USA. The goal of the conference was to bring forest researchers and practitioners together to share the latest research findings related to forest regeneration and early stand dynamics in changing environments around the globe. Nearly 90 registered participants from more than 25 countries made over 70 scientific presentations. A proceedings from the conference (Wagner et al. 2017) with abstracts from all presentations was provided at the meeting and is available at: https ://www.iufro .org/downl oad/file/27365 /1434/10104 -20115 -corva llis1 7-abstr acts_pdf/. The conference was jointly sponsored and organized by Oregon State University’s College of Forestry, Purdue University’s Department of Forestry and Natural Resources, and the University of Idaho’s Department of Forest, Rangeland and Fire Sciences.

Predicting climate change impacts on southern pines productivity in SE United States using physiological process based model 3-PG

T are approximately 82 million ha of timberland and more than 13 million ha of southern pine plantations in the southeastern United States. In this region, slash pine (Pinus elliottii Engelm. var. elliottii) and loblolly pine (Pinus taeda L.) are the most important species, accounting for more than 90% of the planted seedlings in the US. The physiological-process based model, 3-PG (physiological process predicting growth), has been widely applied to estimate the effects of management, climate and site characteristics on different stand level attributes such as stem volume growth, biomass dynamics or water use efficiency. This model uses species-specific physiological traits in conjunction with empirical treeand stand-level dynamics attributes to quantify stand growth and dynamics. Recently, the model was parameterized for loblolly and slash pine stands. The model was validated against a large number studies and operational plots across the natural range of distribution of both species. In this study, we used the model to estimate the impact of future climate change scenarios (using RCP 4.5 and 8.5) on stand dynamics and productivity in SE United States.T occurrence of dry & wet events causes major adverse impacts in the Canadian Prairies. In the past, dry events, which are typically agricultural and/or hydrological droughts, have been common in the region. At least five major drought episodes have occurredin the Canadian Prairies during the past 120 years. These include multi-year droughts in the 1890s, 1910s, 1930s, late 1950s to early 1960s, 1980s, 1999-2005, 2009-10. The years 2001-2004 resulted in one of the largest area multi-year drought. Almost half of the agricultural prairies were in severe drought or worse during 2001. For the older droughts of the 1900 to 1950 period, the 1930s were the largest multi-year droughts, and 1961 and 1919 were the single-year severe droughts that covered the largest area. According to Bonsal et al. (2011), some of the major droughts have migrated into the Canadian Prairies from the United States Great Plains, including the 1999-2005 drought. This means that it is important to monitor the northern US droughts for expansion or migration into Canada.In the future, the frequency of both droughts and intense precipitation areexpected to increase. In fact, the review by Wheaton et al. (2013) found that (i) multi-year droughts (e.g., 5 to 10 years, or so) would occur more than twice as often forthe period to 2100; (ii) they would come with more evaporative power and be more intense as they will have much higher temperatures and much longer warm seasons; and (iii) they would cover much more area than even the across-Canada drought of 2001-2002. Droughts of such magnitudes would have devastating impacts on the Prairies, economically, environmentally, and socially, particularly on those industries where weather is a major determining factor to their survival and performance. One such industry is agriculture. It is the contention of this paper that estimation of impacts of the past droughts has been limited in scope, and may have underestimated these impacts. This under-estimation may be a result of several reasons: (i) Past studies have typically measured these impacts for only the drought period. In reality a drought would affect some of the enterprises (such as livestock production) that take several years to completely result in an economic gain to the producers. (ii) Although private costs of the people impacted by droughts are measured, the macro-level changes causing hardships to people and businesses are not measured. (iii) Droughts may impact ecological goods and services which can then affect the society at large. (iv) Loss to human capital through stress, sickness, and loss of employment as well as other changes that lead to lost productivity are typically not included. (v) Fiscal costs to the governments and their resulting impact on other programs have not been estimated. (vi) Economic hardships to smaller communities and people living therein have also not been addressed. We recommend that future investigations attempt to redress these deficiencies in the method of estimation of social, environmental and economic impacts of droughts. Impacts of the recent severe droughts in the US Plains and Canadian Prairies are reminders that current adaptation can be improved.T like other countries is impacted by climate change and climate variability. Floods and drought are the two major extreme climate events in Tanzania. In recent years (2009-2011), heavy rains accompanied with strong winds have left thousands of people displaced and without food. Heavy rains and floods have resulted into loss of life, livestock and crops; an increase in vector and water-borne diseases; food shortages, internal displacement, and increased disease transmissions, damage to properties, destruction of the environment and economy. On the other hand, six droughts have occurred between 1980-2008 where 7.96 million people were affected, resulting into famine, loss of life, crop failure, lower water availability and quality and electricity rationing. In the Kilimanjaro region, reductions of ice cap and reported glacier vertical retreat have been observed on Mount Kilimanjaro. During the past three to five decades, there has been a steady increase in temperature with decreasing water levels in Lakes in various parts of the country. Rise in sea levels has been experienced, with Islands of Maziwe and Fungu la Nyani been submerged due to rise in sea level. Among others, this paper describes climate change in Tanzania in detail and its impacts to natural ecosystems.R evolution of computers in last decades provides complicating atmospheric models with detailing vertical profiles, accounting for irregular clouds in wide spectral ranges. Numerical algorithms for calculating radiative characteristics with maximal exactness and minimization of uncertainty are usually applied. There are many different computer codes including look-up tables with aerosols characteristics, water vapor, atmosphere conditions in different latitudes, continental and sea conditions, and seasons. Sophisticated approaches for calculating optical parameters are based on scattering and radiative transfer theories. It is very useful for applied problems. However the analysis of separate factors influence on atmospheric radiative characteristics without of considering all possible variations of the whole totality is often necessary for many research problems. For that case the simple models of homogeneous (for the clear atmosphere) and two or three layer atmosphere (for cloudy cases) allow operative varying considered atmospheric optical parameters and provide result that hardly contributes to complicate models and clearly elucidateaninteractions between of key atmospheric parameters and radiative characteristics. Two-stream methods of radiative transfer theory ensure an acceptable exactness for calculating integral (over viewing directions) radiative characteristics (irradiance and radiative divergences). Asymptotic formulas are also effective for fast and transparent calculation in case of the cloud atmosphere. A simplest optical model is accepted of the homogeneous clear atmosphere including ozone absorption in UV ranges, molecular scattering, and four variants of the aerosol content at selected shortwave wavelength. In cloud case three variants of extended cloud layer are added. Radiative characteristics together with heating rate are calculated and presented in this study. Results of optical parameters retrieved from observation of solar radiation in the atmosphere and radiative characteristics are compared with simple modelling.