The Responses of Light Reaction of Photosynthesis to Dynamic Sunflecks in a Typically Shade-Tolerant Species Panax notoginseng

Light is highly heterogeneous in natural conditions, and plants need to evolve a series of strategies to acclimate the dynamic light since it is immobile. The present study aimed to elucidate the response of light reaction of photosynthesis to dynamic sunflecks in a shade-tolerant species Panax notoginseng and to examine the regulatory mechanisms involved in an adaptation to the simulated sunflecks. When P. notoginseng was exposed to the simulated sunflecks, non-photochemical quenching (NPQ) increased rapidly to the maximum value. Moreover, in response to the simulated sunflecks, there was a rapid increase in light-dependent heat dissipation quantum efficiency of photosystem II (PSII) (ΦNPQ), while the maximum quantum yield of PSII under light (Fv′/Fm′) declined. The relatively high fluorescence and constitutive heat dissipation quantum efficiency of PSII (Φf,d) in the plants exposed to transient high light (400, 800, and 1,600 μmol m–2 s–1) was accompanied by the low effective photochemical quantum yield of PSII (ΦPSII) after the dark recovery for 15 min, whereas the plants exposed to transient low light (50 μmol m–2 s–1) has been shown to lead to significant elevation in ΦPSII after darkness recovery. Furthermore, PSII fluorescence and constitutive heat dissipation electron transfer rate (Jf,d) was increased with the intensity of the simulated sunflecks, the residual absorbed energy used for the non-net carboxylative processes (JNC) was decreased when the response of electron transfer rate of NPQ pathway of PSII (JNPQ) to transient low light is restricted. In addition, the acceptor-side limitation of PSI [Y(NA)] was increased, while the donor-side limitation of photosystems I (PSI) [Y(ND)] was decreased at transient high light conditions accompanied with active cyclic electron flow (CEF). Meanwhile, when the leaves were exposed to transient high light, the xanthophyll cycle (V cycle) was activated and subsequently, the JNPQ began to increase. The de-epoxidation state [(Z + A)/(V + A + Z)] was strongly correlated with NPQ in response to the sunflecks. In the present study, a rapid engagement of lutein epoxide (Lx) after the low intensity of sunfleck together with the lower NPQ contributed to an elevation in the maximum photochemical quantum efficiency of PSII under the light. The analysis based on the correlation between the CEF and electron flow devoted to Ribulose-1, 5-bisphosphate (RuBP) oxygenation (JO) indicated that at a high light intensity of sunflecks, the electron flow largely devoted to RuBP oxygenation would contribute to the operation of the CEF. Overall, photorespiration plays an important role in regulating the CEF of the shade-tolerant species, such as P. notoginseng in response to transient high light, whereas active Lx cycle together with the decelerated NPQ may be an effective mechanism of elevating the maximum photochemical quantum efficiency of PSII under light exposure to transient low light.

Effects of Light Environments on Leaf Traits and Phenotypic Plasticity of Canna indica

Canna indica L (African arrowroot), is a beneficial, multi-use tropical perennial with a worldwide distribution, but relatively unexplored. This plant has the potential to be developed as a food crop in an intercropping system, utilizing idle land under commercial plantations such as rubber or teak. This study aimed to determine the best light-growing conditions for C. indica. A completely randomized design was used with growth light as the treatment consisting of 25%, 50%, and 100% of natural light, respectively. Leaf traits, growth characteristics, and phenotypic plasticity were used to measure C. indica’s response to different treatments. The results of this study showed that C. indica grown in low light has the best growth with increased height, leaf area, root and shoot dry weights, but decreased leaf thickness, which caused the increase in specific leaf area, leaf area ratio, and leaf weight ratio, but decreased root to shoot ratio. Based on leaf traits and biomass allocation, the phenotypic plasticity index was 0.23, a typical number for shade tolerant species. These findings were the first time to be reported for C. indica. For agroforestry practices, it can be recommended that C. indica be used as an intercropping plant under tree canopies.

Ecological characteristics of the flora of the Basegi mountains (Perm krai)

В статье оценивается флора хребта Басеги по ряду экологических факторов: водному, световому режимам, богатству почв элементами минерального питания. По водному режиму наблюдается преобладание мезофитов - 53,4%. По световому режиму приблизительно равное соотношение светолюбивых (50,1%) и теневыносливых (47,5%) видов. По богатству почв элементами минерального питания явно преобладают мезотрофы - 72,5%. Территорию можно охарактеризовать, как с преобладанием умеренно увлажненных местообитаний, равным соотношением сообществ без выраженного затенения и выраженным затенением нижних ярусов, и умеренным содержанием в почвах элементов минерального питания. Аналогичная ситуация прослеживается и по высотным поясам, кроме горно-лесного пояса, где по световому режиму преобладают теневыносливые виды. The article assesses the flora of the Basegi Ridge by a number of environmental factors: water, light conditions, and the richness of soil elements with mineral nutrition. The water regime is dominated by mesophytes - 53,4%. According to the light regime, the ratio of light-loving (50,1%) and shade-tolerant (47,5%) species is approximately equal. Soils rich with mineral elements are clearly dominated by mesotrophs - 72,5%. The territory can be characterized as having a predominance of moderately moist habitats, an equal ratio of communities without pronounced shading and pronounced shading of the lower tiers, and a moderate content of mineral nutrition elements in the soils. A similar situation is observed in high-rise belt, except for the mountain-forest belt, where shade-tolerant species predominate in the light regime

Structure, composition and diversity of restored forest ecosystems on mine-spoils in South-Western Ghana

In response to national policy obligations, many mining companies in Ghana have restored/reclaimed degraded mined out sites through revegetation. The area extent of such restored areas is unknown and there is also paucity of data on success of restoration, species diversity and compositional dynamics of such restored landscapes, particularly using mixed species. This study assessed stand structure, diversity and composition dynamics of sites restored with mixed species and models species abundance distribution on these sites. Three reclaimed and one control site (adjacent natural forest) were inventoried using 27, 30 x 30 m plots on the Hwini-Butre and Benso concession of the Golden Star Wassa Limited. Overall 3057 (per 24 plots) and 150 (per 3 plots) individual trees were recorded in the overstorey of the reclaimed and control sites, respectively. In all, 31 species in 13 families occurred on the reclaimed site while 61 species in 29 families occurred on the control. Species richness, abundance and diversity were significantly lower in the reclaimed sites than the control in the overstorey (p≤0.018), mid-storey (p ≤ 0.032), and understorey (p≤ 0.031). Species composition of the reclaimed and control sites were mostly dissimilar in the overstorey, midstorey, and understorey. However, the midstorey and overstorey of the reclaimed sites showed high similarity in composition (Jaccard’s index = 0.817). Pioneer and shade-tolerant species were most dominant in the understorey of the control while only shade-tolerant species (mostly herbs and grasses) dominated the reclaimed sites. Species abundance distribution of both reclaimed and control sites followed the geometric series model, indicating that both sites are disturbed but at different intensities. It is concluded that reclamation with mixed species does not necessarily lead to rapid restoration of indigenous climax species on mine spoils. Nonetheless, it may lead to accomplishments of short-term goals of stabilizing and protecting landscapes while conditioning the sites for colonisation of the climax species.

Occurrence of Citropsis articulata in Tropical Forests in Uganda: Implication for Ex Situ Conservation

Citropsis articulata is a medicinal plant that is increasingly threatened by unsustainable methods of harvesting and habitat degradation. Owing to the fact that this plant species is highly utilized for herbal medicine and is currently restricted to a few forest reserves in Uganda, this has significant implications for ex situ conservation. Therefore, the aim of this study was to assess how physiographical factors influence the occurrence and distribution of C. articulata in the three forest reserves in Uganda, namely, Budongo, Mabira, and Kibale National Park. The study was carried out in 15 compartmental sites in each of the three forests. In each compartmental site, 4 plots of 60 m × 60 m were systematically established, and within each plot, 4 subplots each of size 20 m × 20 m were randomly setup. A total of 240 subplots were assessed for occurrence of Citropsis articulata in each forest. The results indicated a significant ( p < 0.05 ) variation in the density of C. articulata with the highest recorded in Kibale National Park. Citropsis articulata generally occurred at moderate altitudinal landscapes (overall elevation = 1200.0 ± 20.73 m) with soils that are moderately acidic (overall pH = 5.7 ± 0.10), low in salinity (overall salinity = 84.0 ± 3.84 mg/l), and moderate levels of macro- and micronutrients. Citropsis articulata was generally associated with plant communities dominated by canopy tree species of genera such as Chryosphyllum, Celtis, Markhamia, Cynometra, Lasiodiscus, Trilepisium, Funtumia, and Diospyros, thus suggesting that C. articulata is a shade-tolerant species. Establishing the ecological requirements of this plant species among other things informs the potential for ex situ production of this plant. This will not only provide alternative sources of plant harvest but also go a long way in relieving the current harvest pressures exerted on the conserved wild populations of this plant species.

The composition and diversity of natural regeneration of tree species in gaps under different intensities of forest disturbance

The positive ecological interaction between gap formation and natural regeneration has been examined but little research has been carried out on the effects of gaps on natural regeneration in forests under different intensities of disturbance. This study evaluates the composition, diversity, regeneration density and abundance of natural regeneration of tree species in gaps in undisturbed, intermittently disturbed, and disturbed forest sites. Bia Tano Forest Reserve in Ghana was the study area and three gaps each were selected in the three forest site categories. Ten circular subsampling areas of 1 m2 were delineated at 2 m spacing along north, south, east, and west transects within individual gaps. Data on natural regeneration < 350 cm height were gathered. The results show that the intensity of disturbance was disproportional to gap size. Species diversity differed significantly between undisturbed and disturbed sites and, also between intermittently disturbed and disturbed sites for Simpson’s (1-D), Equitability (J), and Berger–Parker (B–P) indices. However, there was no significant difference among forest sites for Shannon diversity (H) and Margalef richness (MI) indices. Tree species composition on the sites differed. Regeneration density on the disturbed site was significantly higher than on the two other sites. Greater abundance and density of shade-dependent species on all sites identified them as opportunistic replacements of gap-dependent pioneers. Pioneer species giving way to shade tolerant species is a natural process, thus make them worst variant in gap regeneration.

Exploring the potential of two-aged white spruce plantations for the production of sawlog volume with simulations using SORTIE-ND

The main objective for even-aged plantation (EAP) management of producing sawlog material has driven practices towards low initial planting densities and lower post thinning densities. For semi-shade tolerant species, the resulting stand density potentially leaves enough growing space for the introduction of a second cohort of trees in the understory, making it a two-aged plantation (TAP). TAP could have many silvicultural benefits, especially in sensitive areas where intensive treatments associated with EAP are incompatible with local management objectives. White spruce (Picea glauca) is a good candidate species for modeling TAP because it is the most widely planted tree species in Canada and has proven tolerance to understory planting. SORTIE-ND, a single-tree spatially explicit growth model was used to explore the yield of variable density and rotation length scenarios when each white spruce cohort is introduced mid rotation, compared to traditional even-aged management. All TAP scenarios tested produced more sawlog volume and more merchantable volume than equivalent densities of EAPs. The lowest density tested, 400 stems ha-1 planted every 35 years, had the highest sawlog yields (3.23 m3 ha-1 yr-1). Considering smaller size products changes the optimum TAP scenario but maintains the advantage over EAPs.

Long-Term Evolution of Composition and Structure after Repeated Group Selection Over Eight Decades

: In northeastern North America, group selection is frequently used in northern hardwood forests to maintain uneven-aged stand structure and promote regeneration of tree species spanning a range of shade tolerances. For this study, long-term application of group selection at the Bartlett Experimental Forest, New Hampshire, USA provided a unique opportunity to address cohort and stand level progression after 80-years of treatment. Cohort-level evolution reflected successional and developmental dynamics associated with even-aged forest systems, whereas aggregate, stand-level conditions were consistent with expectations for uneven-aged systems. As cohorts aged, diameter distributions progressed towards descending monotonic forms and species composition transitioned from shade-intolerant species to shade-tolerant species. Standing deadwood and downed woody material in cohorts followed trajectories of aging even-aged stands through time. Although American beech (Fagus grandifolia Ehrh.) was a primary species across cohorts and at the stand level, stand level regeneration included a mixture of ecologically and commercially valuable species. These long-term results offer important insights into emergent cohort and stand-level conditions and processes that may affect continued recruitment of desirable compositional and structural conditions in stands managed using group selection over numerous cutting cycles.

Mixed Forest Plantations with Native Species for Ecological Restoration in Cloud Forests of the Venezuelan Andes

Tropical cloud forests play a fundamental role in the hydrological cycle of mountain watersheds having the largest biodiversity per unit area. In Venezuela, cloud forests are subject to intense deforestation and fragmentation by farming and cattle-ranching causing soil erosion, water cycle alteration, and biodiversity loss. Reforestation projects used exotic species as Pines and Eucalyptus, native species were rarely planted by lacking knowledge on species requirements and management. We report the performance of 25 native cloud forest species differing in shade-tolerance, planted in mixed assemblies on degraded areas. Tree survival and the individual tree variables: total height, root-collar diameter, tree-slenderness, and crown-ratio were evaluated at 1, 2, 4.5 and 7 years-old. Data was analyzed with a repeated measures analysis of variance mixed model considering species shade-tolerance, light intensity at planting and age as explanatory factors. Survival was over 80%. Shade-intolerant species displayed faster height and root-collar diameter growth. Shade-tolerant species had larger crown ratios due to persistence of lower branches; whereas, shade-intolerant showed signs of crown recession at age 7. Slenderness values from age 4.5 were indicative of good trees stability and health across treatments. The positive results have motivated landowners to establish native species plantations in critical areas with our support.