Since only a small area of Guyana's forest can be effectively protected and because timber harvesting is an important source of income, logged forests will play an important role in the conservation of biodiversity in Guyana. Selective logging, in which only a few trees per hectare are harvested and after which forest remains available, is potentially a good way to utilise the forest without destroying it. In Guyana hard wood from selective logging is an important source of income. As in other tropical countries, sustainable forest management should result in sustained timber yields over long periods of time to provide lasting revenues and to secure livelihoods, while on the other hand also diversity should be conserved as much as possible. To be able to define criteria for sustainable forest management, information on the long-term effects of logging is needed.

Selective logging creates openings in the forest canopy, which results in increased light availability in the forest understorey. As a consequence of this increased light availability some tree species (the pioneers) are able to grow much faster. On the long term this may result in changes in species composition of the forest. The aim of the investigations described in this thesis was to determine the long-term effects of logging on tree population dynamics, forest composition and tree diversity and to evaluate the sustainability of alternative forest management scenarios for both future timber yields and biodiversity conservation. To investigate these long-term effects, a field study was done in logged and non-logged forests in Guyana and additionally a forest simulation model was developed to evaluate different management scenarios. This population dynamics model simulates growth, mortality and recruitment of trees and makes projections of forest composition and available hard wood in the course of decades.

The results of the field study showed that increased light availability after logging is especially advantageous for pioneer species. The abundance of inherently slow growing tree species decreased, but recovered again in the course of years after logging. Model simulations showed, however, that selective logging did not severely affect forest composition. Even in simulations of the most intensive way of logging (12 trees ha-1, every 25 years) forest composition remained rather intact. This is probably due to the fact that in forests in central Guyana, pioneer species are very rare and thus will not easily dominate the forest after logging. After logging once using high harvest intensities of 12 trees ha-1, it took, however, more than 100 years before harvestable timber volumes were comparable again with a baseline (non-logging) situation. For slow growing tree species it even took more than 160 years after logging before the abundance of stems was comparable again with the baseline situation. Projected recovery periods were, however, substantially longer than the currently in Guyana advised length of felling cycle of 60 years. Highest total timber yields were achieved if trees were harvested every 25 years using high harvest intensities. At the same time this approach also resulted in a fast depletion of the available commercial timber volumes in the forest and thus reduced timber yields. The results of the investigations in this thesis can be used to determine criteria for sustainable forest management in Guyana.

/pdf/long-term-responses-of-populations-and-communities-of-trees-15p1l2b06m.pdf

Long-term responses of populations and communities of trees to selective logging in tropical rain forests in Guyana

Tropical rainforests in Guyana are characterised by small-scale disturbance regimes. As a result, tree communities are dominated by shade-tolerant climax species that are adapted to these low and infrequent disturbance events, while pioneers are hardly present. Selective logging in these forests increases the disturbance intensity and was expected to affect population dynamics of different species differently and to change species composition and increase diversity conform the predictions of the intermediate disturbance hypothesis (IDH) for forests with low disturbance intensity. We studied the responses in population dynamics of saplings (2-5 cm DBH) and poles (5-20 cm DBH) of three functional groups (pioneer, long-lived pioneer and climax) to logging in plots in Pibiri, Central Guyana. Additionally we examined effects of logging on functional group composition and tree diversity in Pibiri (6 years data) and Northwest Guyana (5 years data) in plots with harvest intensities ranging from 0 (control) to 16 trees ha. The classification of species into three functional groups was based on their wood density and seed mass. Wood density is shown to be a good predictor of a species’ potential maximum growth rate. In Pibiri, 6 years after logging light conditions were still positively related to harvest intensity. All groups showed increased growth rates with increased light availability. In the higher light classes the growth rates of pioneer poles and saplings were higher than for the other two groups. Especially, highly increased recruitment rates (47% yr) in high light climate resulted in fast net population gain rates for pioneer saplings (44 % yr) in high light conditions. In the Northwest, the abundance of pioneer saplings increased from 1% to 7% in logged plots and of pioneer poles from 2% to 8%, while in Pibiri only pioneer saplings increased from 0% to 6.2% with increasing harvest intensity. In all cases the increased relative abundance of pioneers was at the expense of relative abundances of climax species. In both forest areas, tree α-diversity of saplings, as measured by Fisher’s α, significantly increased with increasing harvest intensity. The results of this study are consistent with the predictions of the IDH for forests at the low intensity end of the disturbance range. Logging increased light availability and created more suitable habitat conditions for successful regeneration of pioneer species that were previously virtually absent. From the trends that we found we made predictions for longer-term effects of logging. Long-term monitoring studies or studies with simulation models are needed to test further hypotheses on the longterm effects of logging.

Responses of tree populations and forest composition to selective logging in Guyana.

The Relationships of Wood-, Gas- and Water Fractions of Tree Stems to Performance and Life History Variation in Tropical Trees

COPYRIGHT © 2022 Prior. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. TYPE Opinion PUBLISHED 19 October 2022 DOI 10.3389/fendo.2022.893889

/pdf/adaptive-reversible-hypothalamic-reproductive-suppression-2m1bien7.pdf

Adaptive, reversible, hypothalamic reproductive suppression: More than functional hypothalamic amenorrhea

http://ctfs.si.edu/Public/pdfs/King_Davies_Noor_2006_JForEcolMgnmt.pdf

Growth and mortality are related to adult tree size in a Malaysian mixed dipterocarp forest

Temporal changes in species diversity, composition, and plant functional types after logging in a Bornean rain forest.

Abstract   During the SARS-COV2 pandemic (COVID-19) many studies have examined changes in women's stress, depression/anxiety, reproduction, plus post-vaccination cycle/flow changes1. Although there are retrospective basal temperature data2, we lack menstrual cycle and ovulation information during the pandemic. This analysis compared two independent, similar-design, convenience/community-based, single-cycle cohort studies 13 years apart: Menstruation Ovulation Study (MOS3, n=301, 2007-8) and MOS2 (n=112) during the pandemic. With MOS as a control, and given evidence subclinicalovulatory disturbances (SOD; short luteal phase/anovulatory menstrual cycles of normal lengths) occur before changed cycle lengths4 5, we hypothesized MOS2 would have increased SOD but similar cycle lengths as MOS. Methods In both studies, recruitment of menstruating women ages 19-35 years, not using systemic or combined hormonal contraceptives (CHC) used posters/eblasts/social media. In MOS, ovulation was assessed by 3-fold increased follicular (FP)-to-luteal (LP/premenstrual) urinary progesterone (PdG); in MOS2, by validated Quantitative Basal Temperature© (QBT)6 7 (normal LP=10+ days). We performed the same interviewer-administered (CaMos©) questionnaire for demographics, SES, and reproduction, measured anthropomorphic variables, plus collected daily Menstrual Cycle Diary© (Diary) for all. FP and LP/premenstrual PdG or salivary progesterone (Ps) samples were respectively collected. Participants in MOS2 were not different from MOS in: average age 29, menarche age 12.5, BMI 24, living situation and education (≥75% university graduates). Cohorts also differed: MOS2 women were less likely to to be White (56% vs 76%), work fulltime, ever use CHC (68% vs 79%) or to be parous (8% vs 20%); they were younger at starting CHC (17.9 vs 18.6 years). Results MOS2 and MOS had similar cycle (30.3 vs 29.9 days, P =.306) and flow lengths (median 6.0 days; P=.055). MOS2 recorded significantly more SOD cycles (>50% anovulatory) vs MOS3 (63% vs 10%; P<.001). MOS2 Diary analyses by Principal Components Analysis showed significantly increased anxiety/depression/frustration (negative moods) and "outside stresses" plus sleep problems and headaches vs MOS (all P<.001). Discussion This is the first evidence that ovulatory disturbances without cycle length changes may be associated with the multidimensional stresses women experience during the pandemic. Increased SOD may also relate to greater nulliparity, younger CHC teen use and more non-White women in MOS2, as well higher prevalence of negative moods, outside stresses and sleep problems. Salivary progesterone, cortisol and estradiol levels remain pending. Prevalent SOD cycles, if persistent/recurrent, risk increased infertility, bone loss5, early heart attacks, and breast and endometrial cancers8. In this 'experiment of nature,' the pandemic was associated with disturbed ovulation rather than menstrual cycles. 1Edelman AB Ob Gyn 2022; 2Nguyen JK PLOS ONE 2021; 3Prior JC IJERPH 2018; 4Prior JC NEJM 1990; 5Li D Epidiol Rev 2014; 6Prior JC Clin Invest. Med 1990; 7Bedford JL Eur J ObGyn Reprod Biol 2009; 8Prior JC DDDM 2020. Presentation: Sunday, June 12, 2022 12:15 p.m. - 12:30 p.m.

/pdf/or15-6-epidemic-of-subclinical-ovulatory-disturbances-during-ndypiv9p.pdf

OR15-6 Epidemic of Subclinical Ovulatory Disturbances During SARS-COV2 Pandemic—an Experiment of Nature

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Temporal changes in species diversity, composition, and plant functional types after logging in a Bornean rain forest.

OR15-6 Epidemic of Subclinical Ovulatory Disturbances During SARS-COV2 Pandemic—an Experiment of Nature