Influence of Residual Basal Area on Longleaf Pine (<i>Pinus palustris</i>Mill.) First Year Germination and Establishment under Selection Silviculture

Even-aged silvicultural methods have been successfully used to manage longleaf pine (Pinus palustris Mill.) forests for wood production;however, successful use of uneven-aged methods to manage this ecosystem is less well documented. In this study, the effects of varying levels of residual basal area (RBA) (9.2, 13.8, and 18.4 m2·ha-1) on longleaf pine germination and establishment under selection silviculture marked using the Proportional-B method were observed. In addition to RBA, photosynthetically active radiation (PAR) was measured, and the relationships between light penetration, germination, and growth were examined. The study found an inverse relationship between RBA and the number of germinants, but the mortality of germinants was not influenced by RBA. PAR also had a significant positive effect on germination, but, did not affect mortality of germinants. In addition, RBA and PAR had no effect on mortality or growth of planted seedlings. Continued monitoring of seedling recruitment into the stand will be required to determine the efficacy of the system. However, nothing in the first year data suggests that this approach will not be successful in sustaining an uneven-aged stand.

Current Standing of Longleaf Pine Trees under Climate Change

Climate change poses many risks to economically and ecologically crucial species.Longleaf pine(Pinus palustris Mill.)trees are keystone species that were once dominant across the southeastern United States,but now occupy less than 5%of their historic range and are thus classified as endangered.Here we review the current status and challenges facing longleaf pine trees,what is known on how changing climate will impact longleaf growth and reproduction,and gaps in the literature that are important to address.We found that many fundamental aspects of longleaf pine growth and reproduction are understood.However,these systems are complex,and not all is known about each factor that influences the relationship between climate,growth,and reproductive output.Additionally,long-term data sets capable of examining all relevant factors in these relationships do not currently exist.To fill necessary gaps,we recommend a joint approach between using readily available data sets and establishing new long-term monitoring plots targeted to collect data on missing or poorly understood conditions.This review provides a clue from an ecological complexity perspective to understand and manage longleaf pine forests under climate change.

Influence of climate fluctuations on Pinus palustris growth and drought resilience

The longleaf pine(Pinus palustris Mill.)ecosystem is an endangered ecosystem in the southeastern USA,and efforts to restore the species are ongoing.However,in recent decades,the region has experienced drastic fluctuations between wet and dry growing season conditions from year to year,and it is not fully understood how these fluctuations have influenced the growth of P.palustris.To address this topic,we cored P.palustris trees in woodlands of southwest Georgia and used dendrochronology techniques to determine how climate fluctuations have influenced the growth and drought resilience of P.palustris.We also cored slash pine(Pinus elliottii Engelm.)trees in the same woodlands to compare growth between species.While P.palustris growth was less impacted by adverse climate conditions compared to P.elliottii,the strength of correlations between P.palustris growth and temperature,precipitation,and Palmer Drought Severity Index(PDSI)changed over time.In recent decades,climate conditions during the growing season became more influential on P.palustris growth than the previous year's conditions.This is concerning given that drought severity during the growing season has been increasing.Our results also indicate that P.palustris was less resilient to droughts during the 2000s and 2010s than to those of the 1950s.Under this new climate paradigm,our results suggest that P.palustris might be more susceptible to growth reductions and less resistant to droughts than once expected.This work highlights the importance of understanding the impact of novel climate conditions on P.palustris and has implications for restoration efforts,such as using silvicultural treatments that reduce tree vulnerability to drought(e.g.,thinning)and promote other climate-adapted species in mixture with P.palustris.

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, predic- tions 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.

优良园林绿化树种长叶暗椤引种培育初报

在普文试验林场ITTO中心苗圃对珍稀优良园林绿化树种—长叶暗椤进行生物及生态学特性、苗木培育技术、栽培技术以及生长状况等方面的引种栽培研究,结果表明,长叶暗椤可作为优良的园林绿化树种在云南省广大热区推广应用。

长叶松优良家系的体胚发生研究

以长叶松优良家系20-820、20-803、20-822、20-805、20-825不同采收期的大配子体为外植体,选用针叶树体细胞胚胎发生专利培养基AL、TX、LP、DS分别与AL、TX、LP培养基激素组合及无激素组合形成16种体胚诱导培养基,开展家系、专利基本培养基、球果采收期对长叶松体细胞胚胎发生率影响的研究。结果表明:诱导体胚最理想的球果采收期为7月16日和24日,即合子胚发育第1、2阶段,参试的5个家系间的胚性胚柄细胞团(ESM)诱导率不存在显著差异,基本培养基、激素组合2因素对ESM诱导率有极显著影响,LP基本培养基与TX激素组合最适宜诱导长叶松体胚,其体胚诱导率为28%。