How to Evaluate Downed Fine Woody Debris Including Logging Residues?

Volume or biomass estimates of downed woody debris are crucial for numerous applications such as forest carbon stock assessment, biodiversity assessments, and more recently for environmental evaluations of biofuel harvesting practices. Both fixed-area sampling (FAS) and line-intersect sampling (LIS) are used in forest inventories and ecological studies because they are unbiased and accurate methods. Nevertheless, most studies and inventories take into account only coarse woody debris (CWD, >10 cm in diameter), although fine woody debris (FWD) can account for a large part of the total downed biomass. We compared the LIS and FAS methods for FWD volume or biomass estimates and evaluated the influence of diameter and wood density measurements, plot number and size. We used a Test Zone (a defined surface area where a complete inventory was carried out, in addition to FAS and LIS), a Pilot Stand (a forest stand where both LIS and FAS methods were applied) and results from 10 field inventories in deciduous temperate forest stands with various conditions and amounts of FWD. Both methods, FAS and LIS, provided accurate (in trueness and precision) volume estimates, but LIS proved to be the more efficient. Diameter measurement was the main source of error: using the mean diameter, even by diameter class, led to an error for volume estimates of around 35%. On the contrary, wood density measurements can be simplified without much influence on the accuracy of biomass estimates (use of mean density by diameter class). We show that the length and number of transects greatly influences the estimates, and that it is better to apply more, shorter transects than fewer, longer ones. Finally, we determined the optimal methodology and propose a simplification of some measurements to obtain the best time-precision trade-off for FWD inventories at the stand level.

Substrate properties, forest structure and climate influences wood-inhabiting fungal diversity in broadleaved and mixed forests from Northeastern Romania

Aim of the study: The main objective of this study was to find the factors which best explains the wood-inhabiting fungal species’ richness in beech and oak-dominated forests.Area of study: We focused on broadleaved and mixed forests found in Northeastern Romania.Materials and methods: 59 plots were randomly set up in broadleaved and mixed forest stands, in which vegetation structure, composition, and topoclimatic factors were quantified along with wood-inhabiting fungal richness. Generalized linear models were used to characterize relationship between fungal diversity and biotic and abiotic factors.Main results: 374 taxa were identified, with numerous species found to cohabitate, the highest sharing being between Fine Woody Debris and Downed Coarse Woody Debris. The best predictors of total diversity were related to the substrate, management, stand structure, and macroclimate. Higher volumes of logs and large branches in various decay stages increased fungal richness. The same effect was found in diverse forests, with large snags. Macroclimate and topoclimate positively influenced diversity, through De Martonne Aridity Index and snow cover length, both indicating macrofungi preferences for higher moisture of substrate. Silvicultural interventions had an ambivalent effect to fungal diversity, phenomenon observed through stump numbers and proportion.Research highlights: Particular environmental characteristics proved significantly important in explaining different wood-inhabiting fungal richness patterns. Substrate-related variables were the most common ones found, but they were closely linked to climate and forest stand variables.Keywords: Wood-inhabiting fungi; oak, beech and coniferous forests; substrate diversity; dead wood types; coarse woody debris; fine woody debris; climatic variables.Abbreviations used:ALT, elevation; ASPI, Aspect Index; BIO1, mean annual temperature; BIO4, temperature seasonality; BIO7, annual temperature range; BIO12, annual precipitation; BIO15, precipitation seasonality; CWD, coarse woody debris; DBH, diameter at breast height; DCWD, downed coarse woody debris; DCWD_DECAY, DCWD decay diversity; DCWD_DIV, DCWD taxonomic diversity; DCWD_SV, surface-volume ratio of DCWD; DCWD_VOL, DCWD volume; DMAI, De Martonne Aridity Index; DMAI_AU, Autumn DMAI; DMAI_SP, Spring DMAI; DMAI_SU, Summer DMAI; DMAI_WI, Winter DMAI; FAI, Forestry Aridity Index; FWD, fine woody debris; L_SNAG_BA, large snag basal area; OLD_BA, basal area of old trees; POI, Positive Openness Index; RAI, Recent Activity Index; SCL, snow cover length; SLOPE, slope; SNAG_N, snag density; STUMP_N, stump density; TPI, Topographic Position Index; TREE_BA, mean basal area of trees; TREE_DIV, tree' Shannon diversity.

Distribution of dead wood volume and mass in mediterranean Fagus sylvatica L. forests in Northern Iberian Peninsula. Implications for field sampling inventory

Aim of study: The aim of this study was to 1) estimate the amount of dead wood in managed beech (Fagus sylvatica L.) stands in northern Iberian Peninsula and 2) evaluate the most appropriate volume equation and the optimal transect length for sampling downed wood.Area of study: The study area is the Aralar Forest in Navarra (Northern Iberian Peninsula).Material and methods: The amount of dead wood by component (downed logs, snags, stumps and fine woody debris) was inventoried in 51 plots across a chronosequence of stand ages (0-120 years old).Main results: The average volume and biomass of dead wood was 24.43 m3 ha-1 and 7.65 Mg ha-1, respectively. This amount changed with stand development stage [17.14 m3 ha-1 in seedling stage; 34.09 m3 ha-1 inpole stage; 22.54 m3 ha-1 in mature stage and 24.27 m3 ha-1 in regular stand in regeneration stage], although the differences were not statistically significant for coarse woody debris. However, forest management influenced the amount of dead wood, because the proportion of mass in the different components and the decay stage depended on time since last thinning. The formula based on intersection diameter resulted on the smallest coefficient of variation out of seven log-volume formulae. Thus, the intersection diameter is the preferred method because it gives unbiased estimates, has the greatest precision and is the easiest to implement in the field.Research highlights: The amount of dead wood, and in particular snags, was significantly lower than that in reserved forests. Results of this study showed that sampling effort should be directed towards increasing the number of transects, instead of increasing transect length or collecting additional piece diameters that do not increase the accuracy or precision of DWM volume estimation.Keywords: snags; downed logs; stumps; fine woody debris; beech; line intersect sampling.