Deadwood in logged-over Dipterocarp forests of Borneo

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Le Corum, Montpellier, 19-23 June 2016

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BSTRACTS /

ORAL PRESENTATIONS

O56-06 – S56 Towards refined carbon budgets of managed forests

Thursday 23 June / 14:30-17:00 – Einstein

Species richness and ecosystem stability control carbon use efficiency of tropical forests

NORBERT KUNERT

Max Planck Institute for Biogeochemistry, Biogeochemical Processes, 07745, Jena, Germany

Tropical forests are characterized by their high photosynthetic activity; however results from pantropical studies show that only 30% of the products from photosynthesis are allocated to new biomass compared to 50% in temperate systems. Mechanisms explaining this low carbon use efficiency (CUE) in tropical forests are still missing. I present a synthesis of studies from two tropical sites with a similar methodological set up to evaluate the ecophysiological responses of tree communities to diversity effects and forest disturbance. Xylem sap flux derived gross primary productivity (GPP) was modelled using eddy covariance data. This was done for a forest plantation with plots of varying tree species diversity in Panama and an old-growth forest with a distinct disturbance gradient in an Amazonian moist lowland forest. Information on net primary productivity (NPP) was calculated from inventory data. The multiple scale analysis provides evidence that GPP increases with tree species richness, but stays relatively stable with forest disturbance intensity. However, CUE decreases with tree species richness, but increases with forest disturbance intensity. Thus, the high diversity of tropical forests and the steady state conditions of tropical old growth forests might explain their low CUE.

O56-07 – S56 Towards refined carbon budgets of managed forests

Thursday 23 June / 14:30-17:00 – Einstein

Seeing the woods through the saplings: using wood density to assess post-disturbance recovery

of human-modified tropical forests

ERIKA BERENGUER

_{, TOBY GARDNER}

_{, JOICE FERREIRA}

_{, LUIZ ARAGÃO}

_{, RALPH MAC NALLY}

_{, JAMES THOMSON}

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IMA VIEIRA

_{, JOS BARLOW}

1_{Lancaster University, Lancaster Environment Centre, LA14YQ, Lancaster, UK}

2_{Stockholm Environment Institute, Stockholm Environment Institute, Box 24218, Stockholm, Sweden} 3_{Embrapa Amazônia Oriental, Embrapa Amazônia Oriental, 66095-100, Belém, Brazil}

4_{Instituto Nacional de Pesquisas Espaciais, Remote Sensing Division, 12227-010, São José dos Campos, Brazil} 5_{University of Canberra, Institute for Applied Ecology, ACT 2617, Bruce, Australia}

6_{Museu Paraense Emílio Goeldi, MCT, 66017-970, Belém, Brazil}

Most of the world’s humid tropical forests have already been modified by human activities such as selective logging, understory fires, and clear-felling. Despite the ubiquity of these human-modified forests, we have a limited knowledge of their potential to recover key traits linked to ecosystem functioning. Here we propose a novel approach to further our understanding of tropical forests recovery to human-driven impacts. We analyze the wood density of trees and saplings in 121 plots (0.25ha each) located across a disturbance gradient in the eastern Brazilian Amazon. Wood density (wd) is a key plant trait, closely linked to important ecosystem functions and services, such as carbon storage. Saplings respond faster to human impacts than large trees and effectively represent the future of a forest stand, thus allowing us to make valuable inferences about the future ecological state of a forest. We combined the analysis of 31,095 stems with a 22-year chronosequence of satellite imagery data and plot-level environmental variables, including recovery time of forest plots, distance to the nearest forest edge, density of lianas, the amount of surrounding forest cover, soil clay content and mean plot slope. We found that wood density of saplings in undisturbed primary forests (wd = 0.70; SE = ±0.004) is significantly higher than in disturbed primary forests (wd = 0.59; SE = ±0.007) and in secondary forests (wd = 0.58; SE = ±0.016), indicating that the human-modified forests of the future may present a different set of traits, and therefore perform a different set of functions, than the future undisturbed forests. We also found that forests located less than 130m away from human-made edges or with high density of lianas (≥900 stems per hectare) may be impeded in their recovery from disturbance or clear-felling. These results indicate that future human-modified tropical forests may hold less carbon than currently expected. We urge scientists, governments and the civil society alike to start addressing the cryptic but severe impacts of human disturbances in remaining areas of standing primary forests and regenerating secondary forests.

O56-04 – S56 Towards refined carbon budgets of managed forests

Thursday 23 June / 14:30-17:00 – Einstein

Deadwood in logged-over Dipterocarp forests of Borneo

ANDES ROZAK

_{, PLINIO SIST}

_{, ERVAN RUTISHAUSER}

1_{Indonesian Institute of Sciences (LIPI), Cibodas Botanic Gardens, 43253, Cianjur, Indonesia} 2_{AgroParisTech, 34093, Montpellier, France}

3_{Cirad, BESEF, 34398, Montpellier, France} 4_{CarboForExpert, 1211, Geneva, Switzerland}

Deadwood is an important stock of carbon in logged-over Dipterocarp forests but still remains poorly studied. Here we present the study of deadwood in logged-over Dipterocarp forests using two common approaches: plot-based approach and line-intersect-based approach.

We conducted our research in three sites which are forest logged in 2003, 2007, and 2010 within Hutansanggam Labanan Lestari (HLL) forest, a certified forest concessionaire in Indonesia. We established 1,500 m of transect line (broken down in 50 m section) for each site. As a reference, we established 47 10 m x 10 m subplot for three sites. All fallen deadwood with diameter > 10 cm were recorded. Our results shows that the mass of fallen deadwood resulted by line-intersect-based method was much higher in compare to plot-based method. The mass of fallen deadwood in plot-plot-based study (44.563 ± 9.155 Mg/ha) was significantly different with the mass of fallen deadwood in line-intersect-based study (69.587 ± 8.079 Mg/ha). Furthermore, for the variability of deadwood, both methods show consistence results which is the variability in 2003 was lower than that in 2007 and 2010.

Based on our data, in order to get coefficient of variation of 10%, we recommend the use of minimum 40 plots of 20 m x 20 m to estimate deadwood in logged-over Dipterocarp forests.

O56-05 – S56 Towards refined carbon budgets of managed forests

Thursday 23 June / 14:30-17:00 – Einstein

Effects of disturbance intensity and tree diversity on the biomass recovery of a managed tropical

forest

ANGELA L. DE AVILA

_{, MASHA T. VAN DER SANDE}

_{, CARSTEN F. DORMANN}

_{, LUCAS MAZZEI}

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ADEMIR R. RUSCHEL

_{, JOÃO O. P. DE CARVALHO}

_{, JOSÉ N. M. SILVA}

_{, LOURENS POORTER}

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MARIELOS PEÑA-CLAROS

_{, JUERGEN BAUHUS}

1_{University of Freiburg, Chair of Silviculture, 79085, Freiburg, Germany}

2_{Wageningen University, Forest Ecology and Forest Management Group, PO Box 47, 6700 AA, Wageningen, The Netherlands} 3_{University of Freiburg, Biometry and Environmental System Analysis, 79106, Freiburg, Germany}

4_{Embrapa Amazônia Oriental, Forest Management Group, Caixa Postal 48, 66095-100, Belém, Pará, Brazil}

5_{Universidade Federal Rural da Amazônia, Av. Presidente T. Neves, 2501, Montese, 66066077-53077-530, Belém, Pará, Brazil}

Sustainable forest management requires that forest ecosystem properties and processes can recover between major management-related disturbances to permit long-term ecosystem functioning. It remains, however, unclear how disturbance regimes and tree community properties influence the resilience of diverse tropical forests. In this study, we investigated how management-related disturbance intensity, remaining tree species diversity and community-mean trait composition affect recovery rates, measured as the annual increment of aboveground biomass, as a proxy for resilience. The study was conducted in a long-term experiment established in 1981 to study the effects of different management intensities and interventions on forest dynamics. The experimental site is located in the Tapajós National Forest, Pará, Brazil. Interventions comprised logging (1982), damage to trees not harvested (i.e., trees that died as an indirect result of logging) and thinning (1993 to 1994). We considered two recovery periods: post-logging (1983-1989) and post-thinning (1995-2012). Trees with diameter at breast height greater than or equal to 10 cm were measured on eight occasions in 41 plots of 0.25 ha. Remaining diversity and community-weighted mean trait values were calculated for the post-intervention censuses (i.e., 1983 and 1995). Predictors were related to biomass recovery rates using structural equation modelling. In both periods, biomass recovery rates of surviving trees increased with basal area remaining, and recovery rates of recruit trees increased with disturbance intensity. We found a weak signal for positive effects of remaining diversity and community-weighted mean trait values on recovery rates. Biomass recovery was strongly determined by disturbance intensity regarding the proportion of basal area remaining. Consequently, strong harvesting and thinning interventions should be avoided to reduce negative effects on productivity and carbon sequestration, as well as on other ecosystem functions which have not been investigated here.