Improving Estimation of Woody Aboveground Biomass of Sparse Mixed Forest over Dryland Ecosystem by Combining Landsat-8, GaoFen-2, and UAV Imagery

Sparse mixed forest with trees, shrubs, and green herbaceous vegetation is a typical landscape in the afforestation areas in northwestern China. It is a great challenge to accurately estimate the woody aboveground biomass (AGB) of a sparse mixed forest with heterogeneous woody vegetation types and background types. In this study, a novel woody AGB estimation methodology (VI-AGB model stratified based on herbaceous vegetation coverage) using a combination of Landsat-8, GaoFen-2, and unmanned aerial vehicle (UAV) images was developed. The results show the following: (1) the woody and herbaceous canopy can be accurately identified using the object-based support vector machine (SVM) classification method based on UAV red-green-blue (RGB) images, with an average overall accuracy and kappa coefficient of 93.44% and 0.91, respectively; (2) compared with the estimation uncertainties of the woody coverage-AGB models without considering the woody vegetation types (RMSE = 14.98 t∙ha−1 and rRMSE = 96.31%), the woody coverage-AGB models stratified based on five woody species (RMSE = 5.82 t∙ha−1 and rRMSE = 37.46%) were 61.1% lower; (3) of the six VIs used in this study, the near-infrared reflectance of pure vegetation (NIRv)-AGB model performed best (RMSE = 7.91 t∙ha−1 and rRMSE = 50.89%), but its performance was still seriously affected by the heterogeneity of the green herbaceous coverage. The normalized difference moisture index (NDMI)-AGB model was the least sensitive to the background. The stratification-based VI-AGB models considering the herbaceous vegetation coverage derived from GaoFen-2 and UAV images can significantly improve the accuracy of the woody AGB estimated using only Landsat VIs, with the RMSE and rRMSE of 6.6 t∙ha−1 and 42.43% for the stratification-based NIRv-AGB models. High spatial resolution information derived from UAV and satellite images has a great potential for improving the woody AGB estimated using only Landsat images in sparsely vegetated areas. This study presents a practical method of estimating woody AGB in sparse mixed forest in dryland areas.

SUBSTRATE GROUPS OF BRYOPHYTES IN THE TERRITORY OF THE ZNESINNYA REGIONAL LANDSCAPE PARK (LVIV, UKRAINE)

The article presents data on the diversity and substrate groups of bryoflora of the Znesinnya Regional Landscape Park (Znesinnya RLP), located in the city of Lviv (Western Ukraine). Based on field research carried out in the period 2015-2018 and analysis of herbarium collections, an inventory was made of the bryoflora of the Znesinnya RLP. A total of 113 species of bryoflora belonging to 66 genera, 35 families and 2 divisions are presented from the investigated area. Of these, 105 species are members of the division Bryophyta and 8 belong to Marchantiophyta. Six regionally rare species of bryophytes have been recorded, namely Pellia endiviifolia, P. epiphylla, Encalypta streptocarpa, Fissidens exilis, Cirriphyllum crassinervium and Sciurohypnum starkei. With regard to substrate preferences, epigeous species of bryophytes predominated and accounted for 89.0% of the total number of species. The largest proportion of bryophytes occurred on bare soil (46.0%), while 36.3% and 25.7% species were found on soil among herbaceous vegetation and on soil with gravel, respectively. Stony substrates were colonized by 42.5% of bryophyte species, with 19.5% of species occurring on artificial stony substrates. In addition, 24.8% of the species belonged to epixils inhabiting old stumps and logs of varying degrees of decay, and the same proportion was represented by epiphytic species of bryophytes. The smallest proportion (10.7%) of bryophytes was confined to water bodies and swampy ecotopes.

THE STATE OF THE HERBACEOUS VEGETATION OF THE ROSSOSHANSKY DISTRICT OF THE VORONEZH REGION

This article presents information about the state of the herbaceous vegetation of the Rossoshansky district of the Voronezh Region. The studies were conducted on 2 trial sites. For this purpose, the eye — measuring method of ground cover accounting was used- accounting for the abundance of individual representatives of the ground cover on the Drude scale and on the Zh. Brown-Blanquet scale. Thanks to this, it was possible to identify plant species that predominate in this area, and species that occur only in a single instance.

Climate and Management Factors Underlying Changes in Beech Forest Herbaceous Layer Plant Communities in the Polish Eastern Carpathians

The herbaceous vegetation and forest stand characteristics in European beech forests growing in the Polish part of the Eastern Carpathians have changed over the last 40 years. This has been influenced by many factors, including land-use change, forest management and climate change. This study investigates changes in forest cover and structure and the associated changes in herbaceous layer plant communities and seeks to elucidate whether and how beech forest herbaceous layer communities have been affected by climate change. The study used information from archival and current land cover maps, semi-permanent sampling plots, forest management plans for the Forest Districts of Brzozów, Lesko and Ustrzyki Dolne and meteorological weather station data compiled for three study periods of herbaceous vegetation (1970s, 2000s, 2010s). In the study area, the regular shelterwood system was changed to an irregular shelterwood system that produces stands with a complex overstorey structure. The results revealed the important role of light availability in shaping the species composition of the herbaceous layer in semi-natural Carpathian beech forests, which was strongly related to the course of management activities. An overall decrease in the number of species during the 2010s is linked to the ageing of beech forests, increased intensity of management activities in ageing stands, competition from understorey vegetation and lower soil moisture that can be linked to climate change. Our study partially supports the existing findings that more manipulative forest management systems can play an important role in countering the current and expected effects of climate change on the forest ecosystem because of the low degree of spatial differentiation of the stand’s structure (developmental stages). Therefore, foresters managing the structure of stands should strive to create a forest structure with high variability of developmental stages on a regional scale.

Pioneer annual vegetation of gravel-bed rivers: first insights on environmental drivers from three Apennine streams

A huge knowledge gap exists on riverine pioneer herbaceous vegetation. Despite its relevance in regulating the C metabolism at the catchment scale, and the triggering role in shrubs and trees establishment along riverbanks, little data is available on its environmental determinants. Indeed, most existing knowledge in this field refers to woody species or aquatic macrophytes neglecting the ecosystem relevance of ephemeral herbaceous vegetation. Focusing on three gravel bed rivers located in northern Italy (Baganza, Nure and Parma streams), the present study is aimed to evaluate the riverine ephemeral plant richness, considering both native and alien taxa, and the role of hydrogeomorphological disturbance and sediment quality in the observed richness patterns. At higher disturbance rates (e.g., larger river sizes), our data indicates a progressive decrease in overall plant richness, but also an increase in the coverage-abundance rates mainly due to alien species. This evidence confirms that variations in hydrology imply changes in pioneer plant species richness at in-stream periodically exposed sediments. More attention must be given to the vulnerability of pioneer vegetation to climate change and direct human impacts to fully understand the functioning of lotic ecosystems, especially the non-perennial ones.