River Red Gum Ecological Thinning Trial Monitoring report 2018 © 2018 State of NSW and Office of Environment and Heritage With the exception of photographs, the State of NSW and Office of Environment and Heritage are pleased to allow this material to be reproduced in whole or in part for educational and non-commercial use, provided the meaning is unchanged and its source, publisher and authorship are acknowledged. Specific permission is required for the reproduction of photographs. The Office of Environment and Heritage (OEH) has compiled this report in good faith, exercising all due care and attention. No representation is made about the accuracy, completeness or suitability of the information in this publication for any particular purpose. OEH shall not be liable for any damage which may occur to any person or organisation taking action or not on the basis of this publication. Readers should seek appropriate advice when applying the information to their specific needs. All content in this publication is owned by OEH and is protected by Crown Copyright, unless credited otherwise. It is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0), subject to the exemptions contained in the licence. The legal code for the licence is available at Creative Commons. OEH asserts the right to be attributed as author of the original material in the following manner: © State of New South Wales and Office of Environment and Heritage 2018. Cover photo: Monitoring in Murray Valley National Park (Photo: Evan Curtis) Information on the ecological thinning trial can be found at: Research in the river red gum forests and Ecological thinning trial in river red gum forests Acknowledgements Collaborations with various universities were critical to implementation and analysis of the field monitoring program. In particular, Charles Sturt University provided significant support for the floristic and vegetation monitoring program in 2017–2018. An honours student at Australian Catholic University, Isobel Kerr, completed an honours thesis in 2017 on the effect of ecological thinning on bats, and also contributed to the bat data collection and analyses in 2018. Published by: Office of Environment and Heritage 59 Goulburn Street, Sydney NSW 2000 PO Box A290, Sydney South NSW 1232 Phone: +61 2 9995 5000 (switchboard) Phone: 131 555 (environment information and publications requests) Phone: 1300 361 967 (national parks, general environmental enquiries, and publications requests) Fax: +61 2 9995 5999 TTY users: phone 133 677, then ask for 131 555 Speak and listen users: phone 1300 555 727, then ask for 131 555 Email: [email protected] Website: www.environment.nsw.gov.au Report pollution and environmental incidents Environment Line: 131 555 (NSW only) or [email protected] See also www.environment.nsw.gov.au ISBN 978-1-925753-89-9 OEH 2018/0329 June 2018 Find out more about your environment at: www.environment.nsw.gov.au River Red Gum Ecological Thinning Trial: Monitoring report 2018 Contents Key results v 1 Introduction 8 1.1 Aims of the ecological thinning trial 8 1.2 Ecological thinning trial experimental design 9 1.3 Expected effects of ecological thinning treatments 11 1.4 Hypotheses 13 1.5 Ecological thinning trial implementation to date 14 1.6 This report 15 2 Methods 19 2.1 Data analysis approach 19 2.2 Bayesian estimation 19 2.3 Linear and additive models 20 2.4 Permanova 20 3 Results: Stem density 21 3.1 Stem density estimates 21 3.2 Change in stem density 21 4 Results: Tree parameters 25 4.1 Tree size class distribution 25 4.2 Live basal area 26 4.3 Tree growth rates 27 4.4 Tree mortality 29 4.5 Tree crown area 31 4.6 Tree height 33 4.7 Hollow bearing trees 34 5 Results: Recruitment 36 5.1 Germinants 36 5.2 Seedlings 37 5.3 Saplings 37 6 Results: Canopy condition 39 6.1 Tree crown extent 39 6.2 Visually assessed canopy cover 42 6.3 Remotely-sensed canopy cover 44 7 Results: Coarse woody debris 47 7.1 Coarse woody debris volume 47 7.2 Diversity of coarse woody debris size classes 49 iii River Red Gum Ecological Thinning Trial: Monitoring report 2018 8 Results: Fire risk 51 8.1 Surface fuel hazard 51 8.2 Near surface fuel hazard 54 8.3 Combined surface and near surface risk 57 8.4 Elevated fuel hazard 58 8.5 Overall fuel hazard 60 9 Results: Soil moisture 63 10 Results: Floristic composition 64 10.1 Total plant species richness and diversity 64 10.2 Native plant species 66 10.3 Exotic plant species 68 10.4 Floristic community composition 71 10.5 Threatened plant species 73 11 Results: Birds 76 11.1 Bird species richness 77 11.2 Bird species diversity 79 11.3 Bird functional guilds 81 11.4 Bird community composition 82 11.5 Individual bird species 83 12 Results: Bats 88 12.1 Overall bat activity 88 12.2 Bat guild activity 89 12.3 Individual bat species 91 13 References 93 Appendix A: Model specifications and results 94 iv River Red Gum Ecological Thinning Trial: Monitoring report 2018 Key results The key results for each monitoring variable analysed in this report are listed below. Significant effects of ecological thinning are in bold text. The number of trees removed varied across thinning treatments. Stem density The average number of stems removed due to thinning was 377 per hectare. Number of stems 10–40 centimetres diameter reduced by an average of 60% due Tree size to thinning. class Abundance of stems <10 centimetres diameter remained variable after thinning. Live basal Average reduction in live basal area due to thinning was 7 m2 per hectare. area The growth rates of larger trees (>70 centimetres diameter at breast height) Tree growth on control plots may have been faster than equivalent trees on thinning rate treatment plots, but the differences may have been pre-existing and the confidence bounds were largely overlapping. There was a slightly increased probability of tree mortality on moderately Tree thinned plots in comparison with control and heavily thinned plots, although mortality confidence bounds were wide. Tree crown No effect of thinning was detected on tree crown area. area Upper canopy tree height was lower in 2017 than 2015, but there was no effect of Tree height thinning treatment. Hollow Fewer dead hollow bearing trees were recorded in 2017 than 2015, but no effects bearing trees of thinning were detected. Germinants: These were recorded on more plots in 2017 than 2015, but there were insufficient data to model the effect of thinning on germinants. Tree Seedlings: A modest increase in the probability of occurrence of seedlings recruitment was detected for heavily thinned plots. Saplings: Thinning reduced the occurrence of saplings. Tree crown extent: No effect of thinning treatment was detected on tree crown extent. Remotely-sensed canopy cover: This was significantly lower on heavily Canopy thinned treatment plots than control plots after thinning. condition Visually assessed canopy cover: Live canopy cover declined on treatment plots between 2015 and 2017 but was stable on control plots. There was no change in the estimated dead canopy cover between survey periods or due to ecological thinning. Coarse woody debris (CWD) volume: Mean volume of coarse woody debris was higher in Site Quality 1 (SQ1) sites but was not affected by thinning treatments. Coarse woody CWD size diversity: This was lower on thinning treatment plots after debris thinning, with the effect being most marked for heavily thinned plots and in the lower site quality class (SQ2). There was a shift from larger to smaller size classes. There was no evidence of thinning treatment effects on litter depth. Mean litter depth values increased across Site Quality 1 sites. Litter No apparent effect of thinning on mean litter cover values. More sites had lower litter cover values in both control and treatment plots in 2017. v River Red Gum Ecological Thinning Trial: Monitoring report 2018 No clear effect of thinning on mean live near surface vegetation cover, although Near surface mean live cover declined on some moderately thinned plots. vegetation cover The mean cover of dead vegetation cover increased on most plots, but no effect of thinning was detected. Elevated Live elevated vegetation (saplings) reduced in thinned plots while control vegetation plots remained stable. cover No change in dead elevated vegetation cover was detected. There was no significant change in combined surface and near surface fire risk, despite a general increase in the near surface fire risk in 2017. Fuel hazard Elevated fuel hazard increased in 2017 across control and treatment plots, although this may be an artefact of the assessment method. No significant effects on overall fuel hazard were detected. Soil No effects on soil moisture were detected. moisture Native plant No significant changes in native species richness or diversity were detected. richness Native plant No effect of thinning was detected on native plant cover. cover Exotic plant Exotic plant species richness increased more on thinned plots than control richness plots. Exotic plant Total cover of exotic plant species increased on all plot types between 2015 cover and 2017, but increased on thinned plots more than control plots. Floristic Floristic composition of plots between site quality classes changed significantly assemblages between 2015 and 2017, regardless of thinning treatment. Plant Individual plant species responses were variable. species There was a significant reduction in bird species richness from 2015 to 2017 across control and treatment plots. Bird species richness The effect of thinning was uncertain as two observers recorded fewer bird species on treatment plots after thinning, and one observer saw more bird species on treatment plots after thinning.