Influence of forest floor vegetation on the total forest reflectance and its implications for LAI estimation using vegetation indices

Recently a simple analytic canopy bidirectional reflectance factor (BRF) model based on the spectral invariants theory was presented. The model takes into account that the recollision probability in the forest canopy is different for the first scattering than the later ones. Here this model is extended to include the forest floor contribution to the total forest BRF. The effect of the understory vegetation on the total forest BRF as well as on the simple ratio (SR) and the normalized difference (NDVI) vegetation indices is demonstrated for typical cases of boreal forest. The relative contribution of the forest floor to the total BRF was up to 69 % in the red wavelength range and up to 54 % in the NIR wavelength range. Values of SR and NDVI for the forest and the canopy differed within 10 % and 30 % in red and within 1 % and 10 % in the NIR wavelength range. The relative variation of the BRF with the azimuth and view zenith angles was not very sensitive to the forest floor vegetation. Hence, linear correlation of the modelled total BRF and the Ross-thick kernel was strong for dense forests (R2 > 0.9). The agreement between modelled BRF and satellite-based reflectance values was good when measured LAI, clumping index and leaf single scattering albedo values for a boreal forest were used as input to the model.

New species of Culex (Culiciomyia) (Diptera: Culicidae) from Talangaye Forest in Cameroon and descriptions and identification keys for males of the Afrotropical species of the subgenus

Species of Culex (Diptera: Culicidae) belonging to the subgenus Culiciomyia were collected in partially logged areas and in surrounding pristine forest (Talangaye Forest) in the Nguti Subdivision in the South-West Region of Cameroon. Mosquitoes were collected mainly by sweep netting through forest floor vegetation. Morphological species identification of African Culiciomyia relies almost exclusively on the structure of the male genitalia and the shapes of comb scales on the maxillary palpi of males. Other features of males and the habitus of females are largely indistinguishable between the species of this subgenus. In total, seven currently described species and three new species were collected in the forest. The males of the three new species are described and named as Culex apicopilosus Cornel & Mayi, sp. n., Culex lanzaroi Cornel & Mayi, sp. n. and Culex pseudosubaequalis Cornel & Mayi, sp. n. More detailed descriptions of males of the other currently known species that were collected in the Talangaye Forest and pictorial keys to the males of all Afrotropical species of Culiciomyia, including the new species, are provided.

Spatial variability of the net ecosystem production and its component fluxes across a managed boreal forest landscape in Sweden: A biometric and chamber data-based analysis

<p>A managed boreal forest landscape is a diverse successional mosaic of clear-cuts to old-growth stands of different species growing on a variety of soil types. Consequently, this high spatial heterogeneity strongly impacts the forest net ecosystem production (NEP) across the managed landscape. However, the quantification of the variability of NEP and its component fluxes across forested landscapes is currently highly uncertain due to the complex interactions between forest structure and physiological processes and their changes over time.</p> <p>Here, we assessed the spatial variability of NEP and its component fluxes during a 3-year period (2016-2018) over a boreal forest landscape (<em>ca.</em> 68 km<sup>2</sup>) located within the Krycklan catchment (64°14′N, 19°46′E) in northern Sweden. For this purpose, we selected 50 representative forest plots (10 m radius) across the catchment spanning various tree species (pine- and spruce-dominated stands) and forest age classes (from clear-cuts to old-growth forests). In each plot, forest floor CO<sub>2</sub> fluxes were manually measured with custom-made closed chambers in monthly intervals during the growing seasons 2016-2018. Measurements were carried out across natural (both light/dark measurements) and trenching/vegetation removal plots (0.45 × 0.45 m) to partition the net forest-floor exchange (NE<sub>FF</sub>) into its contributing components, i.e., gross primary production (GPP<sub>FF</sub>) and respiration (ER<sub>FF</sub>). ER<sub>FF</sub> was further separated into plant autotrophic and soil heterotrophic respiration (Ra<sub>FF</sub> and Rh<sub>FF</sub>). Plot-level biometric measurements were conducted to determine the net primary production of trees and forest floor vegetation (NPP<sub>T</sub> and NPP<sub>FF</sub>) as well as heterotrophic dead wood respiration (decomposition, Rh<sub>DW</sub>). Finally, NEP was calculated as NEP = NPP<sub>T</sub> + NPP<sub>FF</sub> – Rh<sub>FF</sub> – Rh<sub>DW</sub>.</p> <p>Our results showed that NPP<sub>T</sub> consistently increased with forest ageing, while an opposite pattern was observed for NPP<sub>FF</sub>. In general, spruce stands showed lower NPP<sub>T</sub> compared to spruce stands at each given age class. In contrast, pine stands showed consistently higher NE<sub>FF</sub>, GPP<sub>FF</sub>, ER<sub>FF</sub>, Rh<sub>FF</sub>, Ra<sub>FF</sub>, and NPP<sub>FF</sub> compared to spruce stands. The forest floor was a net CO<sub>2</sub> source, which increased with stand age due to the progressive decrease in GPP<sub>FF</sub>, while the ER<sub>FF</sub> remained similar among all the age classes. In addition, an analogous age-related pattern was observed in Rh<sub>FF</sub>. Our findings also depicted an increasing NEP with forest age from about ≈ 54±67 g C m<sup>-2</sup> yr<sup>-1</sup> during the initial stages of development (i.e., 5-30 years-old) to a maximum of ≈ 170±68 g C m<sup>-2</sup> yr<sup>-1</sup> in middle-aged stands (i.e., 60-100 years-old). Higher NEP was generally observed for pine compared to spruce stands. Interestingly, we found that the old-growth forests steadily continue to accumulate C, which is contrary to the common view that they become C neutral or sources.</p> <p>Overall, this comprehensive study improves our understanding of the spatial variability of the C balance over the heterogeneous regional forest landscape in northern Sweden, identifying tree species, forest floor vegetation and forest ageing as key drivers.</p>

Forest habitats and forest types on chernozems in south-eastern Poland

The objective of the study is the presentation of the chemical properties of forest chernozems and the features of forest habitats developed on chernozems in south-eastern Poland. The assessment of the trophic status of chernozems was presented based on the Trophic Soil Index (SIG). Moreover, the paper presents the diversity of forest vegetation on chernozems. The research covered 15 plots from the habitat inventory performed for the Mircze and Strzelce Forest Districts (SE Poland). Habitat conditions were characterised on the research plots, with particular consideration of the soil and vegetation. The analysed soils were featured by the presence of thick humus horizons and the occurrence of calcium carbonate. High SIG values confirm the eutrophic status of the analysed soils. In general, fresh and wet habitats of broadleaved forests (Lśw and Lw), as well as fresh habitats of broadleaved upland forest (Lwyżśw) develop on chernozems in Poland. They are associated with multi-species broadleaved tree stands. The conducted research indicates that, in current environmental conditions, the potential plant community is oak-hornbeam forest with predominance of oak, hornbeam, and abundant admixtures of other broadleaved species. High trophic status of the analysed chernozems is confirmed by high bonitation of tree stands and richness of forest floor vegetation.

The Errors in Visual Estimation of Plants Cover in the Context of Education of Phytosociology

In vegetation science including phytosociology, visual estimates of plant cover and point method belong to the common field method to record species composition and their abundance. Two methods were compared: Braun-Blanquet scale and point method using Levy bridge. A group of students performed measurements in five plots belonged to an oak-hornbeam forest Tilio-Carpinetum. It was revealed that there is a very high discrepancy in a observed number of species. Total mean numbers obtained are 13.4 and 31.2 for point method and Braun-Blanquet method respectively. However, there is the significant positive and medium correlation between two methods in terms of estimation of abundance of species. It can be concluded that point-method is not suitable for study of forest floor vegetation. It can be merged with other methods. Due to many repetitive measures, it can be helpful in learning of recognition of species.