Environmental and vegetation controls on the spatial variability of CH4 emission from wet-sedge and tussock tundra ecosystems in the Arctic

Aims Despite multiple studies investigating the environmental controls on CH4 fluxes from arctic tundra ecosystems, the high spatial variability of CH4 emissions is not fully understood. This makes the upscaling of CH4 fluxes from plot to regional scale, particularly challenging. The goal of this study is to refine our knowledge of the spatial variability and controls on CH4 emission from tundra ecosystems. Methods CH4 fluxes were measured in four sites across a variety of wet-sedge and tussock tundra ecosystems in Alaska using chambers and a Los Gatos CO2 and CH4 gas analyser. Results All sites were found to be sources of CH4, with northern sites (in Barrow) showing similar CH4 emission rates to the southernmost site (ca. 300 km south, Ivotuk). Gross primary productivity (GPP), water level and soil temperature were the most important environmental controls on CH4 emission. Greater vascular plant cover was linked with higher CH4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH4 emission in these tundra ecosystems. Conclusions Overall, this study provides an increased understanding of the fine scale spatial controls on CH4 flux, in particular the key role that plant cover and GPP play in enhancing CH4 emissions from tundra soils

The impact of logging on vertical canopy structure across a gradient of tropical forest degradation intensity in Borneo

Forest degradation through logging is pervasive throughout the world's tropical forests, leading to changes in the three-dimensional canopy structure that have profound consequences for wildlife, microclimate and ecosystem functioning. Quantifying these structural changes is fundamental to understanding the impact of degradation, but is challenging in dense, structurally complex forest canopies. We exploited discrete-return airborne LiDAR surveys across a gradient of logging intensity in Sabah, Malaysian Borneo, and assessed how selective logging had affected canopy structure (Plant Area Index, PAI, and its vertical distribution within the canopy). LiDAR products compared well to independent, analogue models of canopy structure produced from detailed ground-based inventories undertaken in forest plots, demonstrating the potential for airborne LiDAR to quantify the structural impacts of forest degradation at landscape scale, even in some of the world's tallest and most structurally complex tropical forests. Plant Area Index estimates across the plot network exhibited a strong linear relationship with stem basal area (R2 = 0.95). After at least 11–14 years of recovery, PAI was ~28% lower in moderately logged plots and ~52% lower in heavily logged plots than that in old-growth forest plots. These reductions in PAI were associated with near-complete lack of trees >30-m tall, which had not been fully compensated for by increasing plant area lower in the canopy. This structural change drives a marked reduction in the diversity of canopy environments, with the deep, dark understorey conditions characteristic of old-growth forests far less prevalent in logged sites. Full canopy recovery is likely to take decades. Synthesis and applications. Effective management and restoration of tropical forests requires detailed monitoring of the forest and its environment. We demonstrate that airborne LiDAR can effectively map the canopy architecture of the complex tropical forests of Borneo, capturing the three-dimensional impact of degradation on canopy structure at landscape scales, therefore facilitating efforts to restore and conserve these ecosystems

Classifying organisms and artefacts by their outline shapes

We often wish to classify objects by their shapes. Indeed, the study of shapes is an important part of many scientific fields, such as evolutionary biology, structural biology, image processing and archaeology. However, mathematical shape spaces are rather complicated and nonlinear. The most widely used methods of shape analysis, geometric morphometrics, treat the shapes as sets of points. Diffeomorphic methods consider the underlying curve rather than points, but have rarely been applied to real-world problems. Using a machine classifier, we tested the ability of several of these methods to describe and classify the shapes of a variety of organic and man-made objects. We find that one method, based on square-root velocity functions (SRVFs), outperforms all others, including a standard geometric morphometric method (eigenshapes), and that it is also superior to human experts using shape alone. When the SRVF approach is constrained to take account of homologous landmarks it can accurately classify objects of very different shapes. The SRVF method identifies a shortest path between shapes, and we show that this can be used to estimate the shapes of intermediate steps in evolutionary series. Diffeomorphic shape analysis methods, we conclude, now provide practical and effective solutions to many shape description and classification problems in the natural and human sciences.</p

From tree to plot : investigating stem CO2 efflux and its drivers along a logging gradient in Sabah, Malaysian Borneo

This study was part of the SAFE Project, the Global Ecosystems Monitoring network (gem.tropicalforests.ox.ac.uk) and Imperial College's Grand Challenges in Ecosystems and the Environment Initiative. Maliau Basin and Danum Valley Management Committees, Royal Society South East Asia Rainforest Research Partnership (SEARRP), Sabah Foundation, Benta Wawasan, the State Secretary, Sabah Chief Minister's Departments, Sabah Forestry Department, Sabah Biodiversity Council, and the Economic Planning Unit are acknowledged for their support and access to the sites in Sabah. Rostin Jantan, Rohid Kailoh, Suhaini Patik, Ampat Siliwong, Jeffry Amin, Ryan Gray, Johnny Larenus, Unding Jami, Noreen Majalap, Toby Marthews, Alexander Karolus, the Danum 50 ha plot team, Glen Reynolds, Edgar Turner, Laura Kruitbos, Lisa P. Bentley, Benjamin Blonder, Puikiat Hoo, Alexander Shenkin, Chun Xing Wong, Bernadus Bala Ola, Bill McDonald and MinSheng Khoo helped with the stem respiration and plant traits data collection and logistics. Kasia Ziemińska, Hedda Weitz and Jaime Buckingham provided laboratory support during the wood anatomy campaign.Peer reviewe

From tree to plot: : investigating stem CO2 efflux and its drivers along a logging gradient in Sabah, Malaysian Borneo

This study was part of the SAFE Project, the Global Ecosystems Monitoring network (gem.tropicalforests.ox.ac.uk) and Imperial College's Grand Challenges in Ecosystems and the Environment Initiative. Maliau Basin and Danum Valley Management Committees, Royal Society South East Asia Rainforest Research Partnership (SEARRP), Sabah Foundation, Benta Wawasan, the State Secretary, Sabah Chief Minister's Departments, Sabah Forestry Department, Sabah Biodiversity Council, and the Economic Planning Unit are acknowledged for their support and access to the sites in Sabah. Rostin Jantan, Rohid Kailoh, Suhaini Patik, Ampat Siliwong, Jeffry Amin, Ryan Gray, Johnny Larenus, Unding Jami, Noreen Majalap, Toby Marthews, Alexander Karolus, the Danum 50 ha plot team, Glen Reynolds, Edgar Turner, Laura Kruitbos, Lisa P. Bentley, Benjamin Blonder, Puikiat Hoo, Alexander Shenkin, Chun Xing Wong, Bernadus Bala Ola, Bill McDonald and MinSheng Khoo helped with the stem respiration and plant traits data collection and logistics. Kasia Ziemińska, Hedda Weitz and Jaime Buckingham provided laboratory support during the wood anatomy campaign.Peer reviewe

Forest Age Rivals Climate to Explain Reproductive Allocation Patterns in Forest Ecosystems Globally

Forest allocation of net primary productivity (NPP) to reproduction (carbon required for flowers, fruits, and seeds) is poorly quantified globally, despite its critical role in forest regeneration and a well‐supported trade‐off with allocation to growth. Here, we present the first global synthesis of a biometric proxy for forest reproductive allocation (RA) across environmental and stand age gradients from a compiled dataset of 824 observations across 393 sites. We find that ecosystem‐scale RA increases ~60% from boreal to tropical forests. Climate shows important non‐linear relationships with RA, but is not the sole predictor. Forest age effects are comparable to climate in magnitude (MAT: ß = 0.24, p = 0.021; old growth forest: ß = 0.22, p < 0.001), while metrics of soil fertility show small but significant relationships with RA (soil pH: ß = 0.07, p = 0.001; soil N: ß = −0.07, p = 0.001). These results provide strong evidence that ecosystem‐scale RA is mediated by climate, forest age, and soil conditions, and is not a globally fixed fraction of positive NPP as assumed by most vegetation and ecosystem models. Our dataset and findings can be used by modellers to improve predictions of forest regeneration and carbon cycling