Large Woody Debris Research Articles

Evaluating streamflow and temperature effects on Bull Trout migration and survival with linear spatial capture–recapture models

AbstractObjectiveIn the U.S. Pacific Northwest, climate change is increasing air temperatures, decreasing warm season (April–September) streamflow, and increasing cool season (October–March) streamflow. Warmer water temperatures may alter conditions for migratory coldwater fishes like the Bull Trout Salvelinus confluentus. Consequently, an understanding of Bull Trout migration and survival is critical for species conservation and restoration. In the Salmon River basin, Idaho, 1992 and 1993 transpired to be two of the most opposing extreme years among the past three decades for warm season water temperature and streamflow. These extremes provided a unique opportunity to retrospectively compare Bull Trout survival and migration under potential climate change scenarios.MethodsWe evaluated prespawning and postspawning migrations and survival of fluvial Bull Trout that were radio‐tagged and tracked from 1992 to 1994. We used a Cormack–Jolly–Seber linear spatial capture–recapture model to simultaneously model the migration and survival of radio‐tagged prespawn (n = 58) and postspawn (n = 23) Bull Trout among weeks and river reaches with streamflow, water temperature, and habitat covariates.ResultMost individual prespawning migrations were similar among tagged fish, whereas postspawn fish adopted multiple migration and overwintering strategies. Movements of prespawn Bull Trout were larger when (1) weekly average daily maximum streamflow increased and (2) weekly average daily maximum water temperature increased. The model estimated that at least 52% of spawners survived to spawning, and mean weekly prespawning apparent survival was higher in the low‐streamflow year (1992) than in the year with higher and more variable streamflow (1993). Survival of 1992–1994 fish during the 38‐week postspawning period was intermediate to that in the prespawning period. Detections of prespawn Bull Trout were generally higher at sites with more complex habitats, less large woody debris, and fewer undercut banks.ConclusionWe found that the prespawn life stage can represent a shorter time frame (14–18 weeks) with increased mortality compared to the longer postspawning period (38 weeks). Bull Trout apparent survival increased with lower streamflow variability, indicating that expected future changes in climate may adversely affect Bull Trout.

Evaluating the context dependency of large river nursery habitats for fishes in the lower Red River catchment

AbstractBoth fine‐ and coarse‐scale physicochemical conditions affect the quantity and quality of nursery habitats within riverine ecosystems. Nursery habitats in large, braided, and sandbed streams such as the lower Red River of Oklahoma, Texas, and Arkansas are not well described and likely vary among species. Identification of nursery habitats is important for developing proper conservation and management actions. We used an occupancy model framework to determine how hierarchical habitat factors related to the occupancy of 38 juvenile fish species. Our findings indicate that large river nursery habitats can generally be defined by reaches with off‐channel slackwater habitat, having deep pools but shallow thalweg depths, typically located further away from dams, and with low percentages of limestone lithology. Species within the same genera often exhibited variable relationships with river slope, amount of large woody debris, channel shape, discharge, and position of reaches within the stream network. Our results indicate important species‐specific relationships that define nursery habitats, indicating an important context dependency of nursery habitats even within fishes that are taxonomically similar. If the goal is to improve recruitment by native fishes, then consideration of the important species‐specific differences would be beneficial if improvements are made to nursery habitats. Moreover, careful consideration of the effects of dam operations will help maintain proper connectivity to off‐channel habitats important in downriver portions of the river network.

Juvenile salmonid abundance in a diamictic semi‐fluvial stream in Norway—does stream bed shelter beat large woody debris?

AbstractThis study investigates the effect of large woody debris (LWD) on the abundance of juvenile Atlantic salmon (Salmo salar, L.) and anadromous brown trout (Salmo trutta, L.) in semi‐alluvial side channels of the river Aurlandselva (Norway) using point electrofishing and microhabitat mapping. Not the presence of LWD, but stream bed shelter availability and the distance to spawning grounds affected the fish abundance (fish/point), independent of other habitat components. LWD showed only an effect on fish abundance when in interaction with other habitat components. This discrepancy can be explained by the availability of cavities in the shelter‐rich coarse substrate which provide sufficient cover and territory for juvenile fish at the given carrying capacity of river Aurlandselva. Whilst LWD may be most effective to provide shelter in lowland streams (bed slope <0.005), maintaining or restoring shelter‐rich coarse substrates should be considered a key priority in steeper salmonid rivers and associated semi‐fluvial streams.

Channel-reach morphometric analysis on a headwater stream in a low-mountainous region: a case study from Mecsek Hills

Small catchments in mountainous regions affect downstream rivers as a primary source of sediment supply and also generate flash swasfloods, especially during extreme events. These floods have significantly shaped the catchments of small streams in the Mecsek Hills and some rural areas over the past two decades. However, there has been no previous study examining the hydromorphology of headwater catchments in low mountain environments in Hungary. The present study was meant to investigate the fundamental hydrogeomorphological properties of a first-order catchment. A customary and detailed GIS survey of 50-metre sections was aimed at deciphering flash flood vulnerability and geomorphic interrelations within a micro watershed. We found moderate susceptibility to flash floods compared to the whole Mecsek Hills. Stable large woody debris jams were identified during the field survey as major geomorphic channel features functioning as natural barriers which drive channel evolution and reduce flood hazards.

A call to action: The need for evaluation of carbon storage by lacustrine large woody debris

Abstract Global climate change and the push to develop Natural Climate Solutions have increased urgency around the need to quantify, capture, and store carbon to reduce atmospheric concentrations of carbon dioxide—but we may be overlooking a potentially important, long‐term carbon sink. Carbon stored in large woody debris (LWD) in lakes is largely missing from local and global carbon budgets. Waterlogged LWD may remain relatively intact in cold, low‐oxygen hypolimnetic regions for decades to centuries, while LWD buried in lake‐bottom sediments may store carbon for millennia. We postulate that lacustrine LWD may be an important component of local and global carbon budgets, and modern land‐use effects (deforestation, agriculture, stream flow changes) may be reducing inputs of LWD into long‐term lacustrine carbon pools. Quantifying lacustrine LWD, particularly in large lakes, is logistically challenging, resulting in a data gap in carbon budgets. Here, we propose that new aerial and underwater technologies be employed to map and quantify littoral LWD and deposits of sunken and buried LWD to estimate carbon storage and the role of lacustrine LWD in regional and global carbon cycling.

Central Valley anadromous salmonid habitat suitability criteria

Habitat suitability criteria (HSC) are a key information source used in designing habitat restoration projects. Many site-specific HSC have been developed in the Central Valley of California for various life stages of anadromous salmonids. Substantial differences between the HSC can be due to watershed characteristics and the methods used to develop the HSC. Spawning HSC generally have optimum depths of 0.3–1 m, optimum velocities of 0.3–1 m/s, and substrate sizes ranging from 25–100 mm. Optimum conditions for fry are generally shallow (less than 0.5 m) and slow (less than 0.1 m/s) with woody cover. Juvenile salmonids use deeper (0.5–1 m) and faster (up to 0.4 m/s) conditions than fry but are similar to fry in their preference for woody cover. HSC developed by the U.S. Fish and Wildlife Service on the Yuba River are recommended for evaluating habitat restoration projects on larger rivers, while HSC developed on Clear Creek are recommended for evaluating habitat restoration projects on smaller Central Valley streams. A key limitation of existing HSC is that they were only developed for in-channel conditions; fishery benefits of floodplain restoration projects are best quantified using total wetted area. Optimal HSC values are most useful in the initial design of habitat restoration projects, while flow-habitat relationships for existing versus proposed conditions can be useful in identifying needed design refinements, such as adding large woody debris.

THE EFFECT OF ANCHORED LARGE WOODY DEBRIS ON BEACH MORPHOLOGY: A PHYSICAL MODEL STUDY

As the demand for nature-based coastal protection methods increases globally, there remains a stringent need to develop evidence-based design guidance for many of these methods and techniques. Anchored Large Woody Debris (LWD) has been used as an economical method of coastal protection for several decades and has, more recently, gained notoriety as a nature-based approach. Existing design guidance, however, is both limited and not significantly rooted in academic research. This paper presents results from the first experimental study related to coastal protection using LWD. Gravel beach response to various LWD configurations were tested at a large scale based on site characteristics and LWD design characteristics made by the authors during the previous field investigation phase of this research project. Tests were also conducted to assess experiment repeatability, sensitivity to test duration, sensitivity to wave height, wave period, and relative water level, and influence of log roughness. The LWD placement elevation relative to the still water level was found to be strongly linked to the beach morphological response and a theoretical relationship was developed between LWD elevation and sediment volume change. LWD design configurations which included LWD below the still water level, such as the Benched configuration, were found to be most effective at stabilizing the beach profile. To realize potential benefits of coastal protection using LWD, significant additional research is needed on the topic, including studies focused on how to best anchor LWD structures and a wider variety of parameters (hydrodynamic conditions and placement techniques).

Characterizing the Importance of Porosity of Large Woody Debris Accumulations at Single Bridge Piers on Localized Scour

AbstractThe accumulation of large woody debris (LWD) at bridge piers is a serious hazard to the structural integrity of bridges across watercourses worldwide. The exacerbated scour that can directly result from LWD accumulations can lead to major structural damage or even catastrophic collapse. Recent research has led to empirical equations to estimate the scour depth for given LWD accumulation size; however these are mostly based on experimental tests with prismatic and impervious solid LWD accumulations, ignoring field observations that have shown that accumulations are neither impervious nor prismatic but are porous with inverted conical shapes. In this study, we therefore investigate the effects of porous LWD accumulations having shapes commonly observed in the field on scour holes. Results reveal that LWD size and shape, and flow characteristics are the primary factors influencing the erosion of sediments at the base of bridge piers. However, the porosity of accumulations is also observed to have a considerable effect on the size and maximum depth of scour holes. In particular, porous LWD reduce the maximum scour depth by up to 50% (and on average in the range of 5%–25%) relative to the respective solid impervious accumulation. The results shown in this study also provide a practical tool for arriving at more realistic and less conservative estimates of scour depths at bridge piers when affected by LWD accumulations.

Large wood supports Elwha revegetation by reducing ungulate browsing

IntroductionThe increasing number of dams approaching obsolescence drives a need for knowledge about riparian restoration associated with dam removal. Restoring woody vegetation on exposed reservoir beds following dam removal is essential to stabilizing sediment, reconnecting riverine and terrestrial systems, and providing future sources of shade, nutrients, and wood. Revegetation after dam removal on many rivers can be challenging due to rapidly drying sediment, low sediment nutrient content, and heavy ungulate browse pressure. Revegetation in Elwha River restoration, the largest dam removal to date, used large woody debris (LWD) to mitigate moisture and nutrient limitation but ungulate browsing has constrained woody plant growth in many coarse sediment deposits. We evaluated potential for LWD to reduce ungulate browsing following Elwha dam removal.MethodsWe studied LWD mitigation of browsing in the largest former reservoir and a comparable valley upriver with a natural floodplain. We measured browse intensity in randomly located plots stratified by four levels of LWD extent, from no LWD to complete LWD enclosure.ResultsLWD reduced browse intensity four-fold in the former reservoir, but only in plots fully surrounded by LWD. Partial LWD enclosure provided little browse reduction. We obtained similar results in the upriver valley, where browse intensity was somewhat lower except within wood clusters. Wood-mediated browse reduction was slightly greater in the former reservoir than in the upriver valley. Protection from browse was greatest for plant species preferred by ungulates.DiscussionThese results suggest forest restoration after dam removal can be expedited by surrounding young trees with large logs. Planting within LWD clusters or placing LWD clusters in restoration sites can facilitate establishment of forest islands in strategic locations. These forest islands can support dispersal of seeds and marine derived nutrients, reconnect established forest to the river, and potentially advance restoration by decades.

The influence of large woody debris on post-wildfire debris flow sediment storage

Abstract. Debris flows transport large quantities of water and granular material, such as sediment and wood, and this mixture can have devastating effects on life and infrastructure. The proportion of large woody debris (LWD) incorporated into debris flows can be enhanced in forested areas recently burned by wildfire because wood recruitment into channels accelerates in burned forests. In this study, using four small watersheds in the Gila National Forest, New Mexico, which burned in the 2020 Tadpole Fire, we explored new approaches to estimate debris flow velocity based on LWD characteristics and the role of LWD in debris flow volume retention. To understand debris flow volume model predictions, we examined two models for debris flow volume estimation: (1) the current volume prediction model used in US Geological Survey debris flow hazard assessments and (2) a regional model developed to predict the sediment yield associated with debris-laden flows. We found that the regional model better matched the magnitude of the observed sediment at the terminal fan, indicating the utility of regionally calibrated parameters for debris flow volume prediction. However, large wood created sediment storage upstream from the terminal fan, and this volume was of the same magnitude as the total debris flow volume stored at the terminal fans. Using field and lidar data we found that sediment retention by LWD is largely controlled by channel reach slope and a ratio of LWD length to channel width between 0.25 and 1. Finally, we demonstrated a method for estimating debris flow velocity based on estimates of the critical velocity required to break wood, which can be used in future field studies to estimate minimum debris flow velocity values.

Post-Wildfire Debris Flow and Large Woody Debris Transport Modeling from the North Complex Fire to Lake Oroville

The increase in wildfires across much of Western United States has a significant impact on the water quantity, water quality, and sediment and large woody debris transport (LWD) within the watershed of reservoirs. There is a need to understand the volume and fate of LWD transported by post-wildfire debris flows to the Lake Oroville Reservoir, north of Sacramento, California. Here, we combine debris flow modeling, hydrologic and hydraulic modeling, and large woody debris transport modeling to assess how much LWD is transported from medium and small watersheds to Lake Oroville. Debris flow modeling, triggered by a 50-year rainfall intensity, from 13 watersheds, transported 1073 pieces (1579.7 m3) of LWD to the mainstem river. Large woody debris transport modeling was performed for 1-, 2-, 5-, 25-, 50-, 100-, and 500-year flows. The transport ratio increased with discharge as expected. LWD is transported to the reservoir during a 2-year event with a transport ratio of 25% with no removal of LWD and 9% with removal of LWD greater than the cross-section width. The 500-year event produced transport ratios of 58% and 46% in our two sub scenarios.

Probabilistic risk assessment framework for predicting large woody debris accumulations and scour near bridges

The accumulation of waterborne large woody debris is a critical issue facing bridges spanning active waterways. In addition to collision forces, drift buildup constricts flow, producing increased hydraulic pressures and exacerbating scour, the cause of nearly one-third of bridge failures. Accurate methods of predicting debris generation, transport, entrapment, and dimensions are consequently necessary to improve public safety, bridge designs, and informed decision-making. However, debris buildup characteristics are site-specific, varying with the regional vegetative, hydraulic, topographical, and geotechnical properties. As sufficient data on these properties is limited to create empirical predictive models, a probabilistic physics-based framework incorporating the risk assessment of local vegetation to estimate debris accumulation and scour is developed. Based on the upstream tree, soil, weather, and river conditions, fragility assessment of the riparian trees from landslides and windthrow is conducted to estimate the probability of debris generation and subsequent entrapment. The framework is demonstrated in a case study of a bridge in Vermont subject to Hurricane Irene. Sensitivity analysis is conducted to quantify the importance of various contributing factors, including slope, rainfall, wind gust, flow rate, and pier geometry. The experimental results highlight the importance of including the debris accumulation in the scour projections.

Field Measurements and Modelling of Vessel-Generated Waves and Caused Bank Erosion—A Case Study at the Sabine–Neches Waterway, Texas, USA

The Sabine–Neches Waterway (SNWW) is home to the largest commercial port of the United States military and of the refineries that produce 60% of the nation’s commercial jet fuel. The deposited sediments from bank erosion due to wake wash result in frequent dredging to keep the waterway operational. This study investigates vessel-generated waves and their impacts on bank erosion. Surface wave data at Golden Pass and the City of Port Arthur Park dock were measured using a 1 MHz Aquadopp Profiler. Bank properties such as soil strengths were measured and soil samples were collected. Acceptable predictive models for estimating the maximum wave heights caused by vessels sailing through the SNWW were developed and validated with recorded data. Vessel-generated waves are found to produce enough shear forces to mobilize bed sediments and cause bank erosion. The bed erosion rate increases with an increase in wave height or a decrease in water depth. Bank and bank toe erosion occurs at both monitoring locations. Bank stability and toe erosion model (BSTEM) results suggest that potential bank protection options are large woody debris and riprap at Port Arthur. However, other stronger stabilization methods are required at Golden Pass.

Interaction of Various Ecological Factors on Benthic Macroinvertebrate and River Health

River health is an aspect that goes beyond river cleanliness. This is because a clean river does not necessarily have life in it but a healthy river do. The ecological component is a factor that affects aquatic life which at the same time describes the level of river health. To answer this question, a study to identify the relationship between ecological factors and aquatic life with river health was conducted. This study was conducted in Sungai Mengkibol, Sungai Madek and Sungai Dengar in Johor. There were a total of five sampling sites, three for impact stations and two as reference stations, including one highland station. Total of seven elements namely ecological indices, physico-chemical water quality, river riparian, canopy cover, large woody debris (LWD), river discharge and substrate composition were measured and analyzed. Surber net measuring 500 micron mesh size combined with a rectangular quadrate of 30 cm x 30 cm (0.09 m2) were used to sample the benthic macro-invertebrate. Chi-square test was performed to determine the association level between one variable with another, meanwhile Pearson’s R value was analyzed to determine the correlation level either it is strong or weak. The results show that, all river ecological components have a significant correlation to the benthic macroinvertebrate ecological indices, however the association was varies. Based on the chi-square test, Pearson’s value, p and Pearson’s R value, the interplay (interaction) of various ecological factors on aquatic life forms and river health was produced with various p-value<0.05 and R-value is more than 0.5. It can be suggested that the ecological indices for benthic macroinvertebrates can be used as an indicator to assess river health.

Using continuous surveys to evaluate precision and bias of inferences from design-based reach-scale sampling of stream habitat

Accurately estimating stream channel characteristics is essential for managing and restoring populations and aquatic ecosystems. Reach-based sampling designs have been used extensively to collect fisheries related data; however, few studies have examined accuracy and precision of scaling up reach-based sampling designs to stream habitat assessments. Here, we used continuous habitat surveys across multiple reaches to census stream attributes in tributaries in the upper Lewis River, Washington and better understand the potential bias and precision of reach-based designs. We used these continuous data to create simulated outcomes from three different random sampling designs. We found precision of estimates of stream-level habitat attributes (large woody debris, residual pool depth, and grain size) increased with the number of reaches sampled (i.e., sampling intensity); however, effort needed to achieve reasonable precision (coefficient of variation = 0.20) varied across streams, attributes, and designs. Bias (i.e., estimate—the truth) was relatively low, but also varied across streams and attributes. Our findings illustrate the challenges of using reach-based designs for stream-level habitat assessments and the need for novel approaches for broader data collection.

PING‐Mapper: Open‐Source Software for Automated Benthic Imaging and Mapping Using Recreation‐Grade Sonar

AbstractThe characterization of benthic habitats is essential for aquatic ecosystem science and management, but is frequently limited by waterbody visibility and depth. Recreation‐grade side‐scan sonar systems are increasingly used to aid scientific inquiries in aquatic environments due to their relative low‐cost, ease of operation, low‐weight, and ease of mounting on a variety of vessels. However, existing procedures and software for post‐processing these data are either limited, closed source, or fail on data from new sonar models, limiting the development of reproducible workflows. Here, we present PING‐Mapper, an open‐source and freely available side‐scan sonar post‐processing toolset for processing and mapping sonar recordings from popular Humminbird instruments. The modular software automatically: (a) decodes sonar recordings from any Humminbird system, (b) exports ping attributes from every sonar channel, (c) uses sonar sensor depth for water column removal, and (d) exports sonogram tiles and georectified mosaics. Sonar channels are processed in parallel for quick decoding and metadata extraction. Major processing wokflows, including georectification and image export, are optimized to scale with computing resources. The software has been extensively tested using data from several rivers of varying character and distribution of depths, but could also be used in estuarine and lacustrine environments. Usage of PING‐Mapper is illustrated in three case studies focused on mapping large woody debris, bathymetric mapping, and visual interpretation and mapping of substrates for selected reaches of the Pearl and Pascagoula river systems in Mississippi.

Large Wood Debris Contributes to Beach Ecosystems but Colombian Beachgoer’s Do Not Recognize It

Large Woody Debris (LWD) accumulation serves essential ecological functions and benefits society’s coastal ecosystems (e.g., beaches). Thus far, the ecosystem services perspective has paid little attention to LWD. Therefore, we aim to contrast social perceptions on LWD and its ecological significance in Puerto Velero beach, Caribbean, Colombia. In consequence, the contribution of LWD to the conformation and creation of Puerto Velero beach was analyzed, as well as how beachgoers perceive the importance of LWD and if they were willing to pay to remove LWD in this beach. To achieve this, a quantitative convergent approach was then proposed using GIS analysis and remote sensing to understand the contributions of LWD to the Puerto Velero beach ecosystem; and in addition, a survey was performed to determine how beachgoers perceived LWD and how they valued the phenomenon. Results indicate that LWD contributed to beach maintenance; nevertheless, most people neglected LWD values because of its lack of visual attractiveness. As such, ecosystem services targets become conflicted because people positively perceived ecosystem services provided by beaches, but they did not assign importance to the beach dynamics they deemed unattractive, regardless of their vast importance.

Experimental and Numerical Investigation of Floating Large Woody Debris Impact on a Masonry Arch Bridge

Masonry arch bridges form an essential part of existing transport infrastructure around the world, including mainland Europe and the northeastern US. Recent extreme flood events highlight that masonry arch bridges spanning watercourses are vulnerable to flood-induced hydrodynamic and debris impact loads. When the flow interacts with the bridge superstructure, with or without discrete floating debris, a complex interaction is observed. This paper presents both experimental and numerical studies to investigate this complex phenomenon, including fluid–structure and structure–structure interactions. A typical single-span masonry arch bridge and large woody debris representing a tree log are investigated. Experimental observations from a scaled hydraulic model, with and without debris in the flow, are first presented for the case where the abutment of the bridge is fully submerged. Next, the capability of the numerical method smoothed particle hydrodynamics (SPH) in simulating the hydrodynamic behaviour and debris impact observed in the experiment is discussed. Following this, both hydrodynamic and debris-induced pressure–time histories on the bridge are obtained using the SPH model. Results reveal that the debris impact leads to a significantly more localised load on the bridge compared to the situation with hydrodynamic load only.

LARGE WOODY DEBRIS ACCUMULATIONS IN THE LATE PENNSYLVANIAN TROPICS—EVOLUTIONARY SIGNAL OR TECTONO-CLIMATIC ARCHIVE?

ABSTRACTBy colonizing drylands, plants fundamentally changed continental deposition and, thus, intensified the interaction between life and sediments. Fossil large woody debris in epiclastic strata is a key archive of this environmental turnover, although its interpretation remains challenging due to taphonomic biases. We review voluminous fluvial red-bed successions with sizeable silicified trunks that characterize Middle Pennsylvanian–lower Permian strata of east-central Europe. The stratigraphic occurrence, petrography, architecture of the deposits, and the preservation and nature of the fossil wood are discussed in the context of the tectono-climatic and vegetational evolution of the central-Pangean low latitudes. The log-bearing successions are assigned to five distinct, regionally traceable stratigraphic levels between the middle Moscovian and early Asselian. Up to 20 m long, mostly decorticated trunk fragments occur isolated in more or less feldspathic channel deposits, the architectures and dimensions of which point to large-scale river systems with highly variable discharge. Wood anatomy and floodplain adpression-fossils show that the trunks were derived from cordaitaleans, conifers, and arborescent sphenopsids in more diverse, gymnosperm-dominated dryland floras. The fossil record is biased towards successions formed in large-catchment river systems and, thus, does not accurately document the genuine nature of plant-distribution patterns. Rather, the strata show that large woody debris preservation depended on fluvial style and hydrological regime, hence turning the woody deposits into climate archives. The strata elucidate the climate development in equatorial Pangea, paralleling the acme of the Late Paleozoic Ice Age.

Biodegraders of Large Woody Debris Across a Tidal Gradient in an Indonesian Mangrove Ecosystem

There has been limited research on the breakdown, recycling, and flux of carbon from large woody detritus (LWD) in mangrove forests. The breakdown of LWD is caused by guilds of terrestrial and marine biodegrading organisms that degrade wood at a range of rates and efficiencies. Spatial variations in environmental factors within mangroves affect the distribution and community of biodegrading organisms, which, in turn, impacts carbon flow and sequestration. We reveal the role of biodegrading organisms in LWD breakdown and the environmental factors that influence the distribution of biodegrading guilds within a mangrove forest in South East Sulawesi that supports a diversity of mangrove species typical of Indonesian mangrove forests, which constitute 20% of Global mangrove cover. Within the high intertidal regions, terrestrial biodegradation processes dominated upon LWD. After 12 months exposure on the forest floor, experimental wooden panels in these areas remained unchanged in mass and condition. In the low intertidal region, marine wood-boring animals belonging to the family Teredinidae were the dominant biodegraders of LWD, and their activity reduces LWD volume and speeds up the loss of LWD volume. More than 50% of the experimental wooden panels’ weight in these areas was lost after 12 months exposure on the forest floor. Although different biodegrading guilds occupy the same LWD niche, their distribution throughout the mangrove forest is influenced by inundation time. The change of biodegrading guilds within LWD between the terrestrial and the marine organisms was distinct, creating a biodegradation boundary in a distance as narrow as 1 m on the mangrove forest floor. These results are important, as rising sea levels have crucial implications for biodegrading guilds. A full understanding of factors affecting the biodegradation processes of LWD in mangrove forests is critical to accurately assess mangrove carbon stores and the fate of mangrove derived carbon.