Foliar nutrient and carbohydrate in Aralia elata can be modified by understory light quality in forests with different structures at Northeast China

Hongxu Wei, Xin Chen, Guoshuang Chen, Hengtian Zhao

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Many non-wood forest product (NWFP) plants are shade-obligate species, but current understanding about their foliar response to understory spectrum is quite scarce. To monitor understory light condition at large scale faces significant obstacles from heavy canopy shade and high cost of sensors arrangement. Therefore, we employed a novel methodology to meter the relative light ratio between plots under canopy and in the open-air. In this study, a number of 34 plots of natural Aralia elata populations were investigated for forest structure across six types of forests at Northeast China. Light properties of relative intensity, photosynthetic photon flux rate (PPFD), spectra in red, green, and blue wavelengths, and relative ratio of red/green, red/blue, and green/blue were measured at the height of 1.3m. Leaves of A. elata were collected to determined concentrations of nitrogen (N), phosphorus (P), starch, and soluble sugars. We found that relative blue light ratio was different among forest-types, but it had little further effect on leaf traits in A. elata. Instead, higher ratios of relative green light and green/blue depressed leaf P concentration. Increases in PPFD and light intensity promoted leaf N and P concentrations, respectively. The red/green ratio had adverse relationships with leaf P and starch concentrations in A. elata. In conclusion, due to the variation understory light condition, sites with low canopy density would benefit leaf N concentration and those with larger canopies can promote leaf starch accumulation in A. elata. 

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The Neotropical tree Ilex paraguariensis A. St. Hil. (Aquifoliaceae): pollen and seed dispersal in a fragmented landscape

Carlos Seoane, Vinicius Diaz, Paulo Kageyama, Maria Moreno, Evandro Tambarussi, Ananda Aguiar, Alexandre Sebbenn

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Ilex paraguariensis is a dioecious, Neotropical tree endemic to South America with wide cultural, economic and ecological signi cance. However, due to extensive fragmentation and deforestation throughout its natural area of occurrence, studies on gene ow and genetic diversity are needed to drive genetic conservation and improvement strategies. Based on the sampling of all adult and juvenile trees in two I. paraguariensis populations, we investigate the reali ed pollen and seed ow and dispersal distance, spatial genetic structure (SGS) and genetic diversity using microsatellite markers. We found limited genetic di erentiation between populations (G’ st = 0.033), but signi cant di erences in terms of genetic diversity (R: 4.7 vs 3.9, H 0 : 0.495 vs 0.371, H e : 0.445 vs 0.375), pollen (10 vs. 23.3%) and seed immigration (0 vs. 3.3%), mating among relatives (t r : 16 vs 30%) and biparental inbreeding (F r : 0.253 vs. 0.345). Within populations, the genetic diversity was similar between adults and juveniles, but adults presented signi cantly lower xation index than juveniles, suggesting selection against inbred individuals between juvenile and adult life stages. We also found similar mean pollen (255 vs. 293 m) and seed (385 vs. 323 m) dispersal distances within populations. Our results show that the studied populations are not genetically isolated and some mating occurs among related trees due to SGS; however, the frequency of biparental inbred individuals decrease over the life course due to inbreeding depression. These results contribute directly to species management and seed collection and inform in situ and ex situ conservation programs.

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Phytosociological approach to scree and ravine forest vegetation in Slovakia

Richard Hrivnák, Michal Slezák, Karol Ujházy, Františk Máliš, Drahoš Blanár, Mariana Ujházyová, Ján Kliment

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The aim of the study was to perform phytosociological revision of the scree and ravine forest vegetation in Slovakia in order to identify i) basic vegetation units of vegetation according to their floristic composition, and ii) to find out the main environmental gradients affecting their compositional variability. Relevés originally assigned to broadly comprehended alliance Tilio platyphylli-Acerion (974 relevés) were used for the analyses. In order to select final dataset (527 relevés), formal criteria, such as tree layer cover >50%, relevé area of 200–500 m² and presence at least two from six traditionally accepted diagnostic species of the alliance in Central Europe (Acer platanoides, Lunaria rediviva, Phyllitis scolopendrium, Polystichum aculeatum, Tilia platyphyllos and Ulmus glabra) were applied to the primal dataset. Altitude, aspect, slope, climatic characteristics (mean annual precipitation and air temperature), geological bedrock and Ellenberg indicator values (EIVs) were specified for each phytosociological relevé. We used modified TWINSPAN algorithm for classification, Detrended Correspondence Analysis (DCA) for explanation of species composition-environmental relationships, and both ANOVA corrected using modified permutation test and Mann-Whitney U-test to test environmental differences at each step of division by numerical classification. Two alliances, Melico-Tilion platyphylli and Tilio platyphylli-Acerion were distinguished with three (Aceri platanoidis-Tilietum platyphylli, Scolopendrio-Fraxinetum and Seslerio heufleranae-Quercetum petraeae) and two (Mercuriali perennis-Fraxinetum excelsioris and Lunario redivivae-Aceretum pseudoplatani) associations, respectively. Besides the floristic composition, other important factors for differentiation of the associations were altitude and related climatic characteristics. The main environmental characteristics affecting the overall compositional variability of studied forests were EIVs for light, moisture, soil reaction and temperature. The complex syntaxonomical revision identified five floristically and ecologically clearly differentiated associations, what reduced the number to almost half of previously distinguished communities from the territory of Slovakia. Moreover, presented concept is at alliance level in accordance with recent European classification approach.

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