Epiphytic plants responses to light and water stress.

Epiphytes are plants susceptible to the current climate change due to continuous exposure of environmental changes. In this study, we review the epiphytes responses to fluctuations in their surrounding environments. Abiotic factors such as light and water are the important contributors towards the epiphytes growth. Epiphytes might suffer from environmental stresses namely high light intensity and water deficit, affecting its growth and physiological attributes. Epiphytes use several mechanisms to counter aforementioned problems and one of it is through changes of physiological pathways. Some of the epiphytes use Crassulacean Acid Metabolism (CAM) as protection system for survival in severe environments. Future studies should include more approaches used by this plant as defense mechanisms to such stresses and more studies on leaf anatomy, leaf structure and variations in biochemical components for further understanding of the mechanisms involved

Responses of Platycerium Coronarium (Koenig.) Dev and Platycerium Bifurcatum (Cav.) c. chr. to Light and Water Stress in Nursery Enviroment

Environmental changes have enormous effects especially on plants physiology and growth. These changes will have significant impact on the growth and survival of plants in the changing of future climates. Canopy plants especially epiphytes which live in the forest canopy play an important role to their surroundings. Thus, this study was conducted to evaluate the growth and physiological response of Platycerium coronarium and Platycerium bifurcatum towards light and water stress. In light stress study, both species were grown under four treatments namely 20 μmol m-2s-1 (T1), 70 μmol m-2s-1 (T2), 200 μmol m-2s-1 (T3) and 1500 μmol m-2s-1 (T4). In water stress study, they were divided into five treatments which were watered once everyday (T1), watered to field capacity (T2), watered once in two weeks (T3), watered once in three weeks (T4) and not watered (T5). Growth responses were evaluated through the leaf length measurement, leaf area, sporotrophophyll weight, cover leaves weight, total dry weight and total leaf water content. Physiological responses were quantified by leaf gas exchange, chlorophyll fluorescence and whole plant transpiration rate. All measurements were carried out weekly for twelve weeks. Two experiments were conducted to determine whether both species were CAM plants by determining their leaf acidity and carbon 13 isotope (δ13 C) ratio. In light stress treatment, leaf length and leaf area of P. coronarium, was statistically different between treatments (p≤0.05). However, T1 had the lowest value in all growth parameters. Lowest light intensity reduces growth for this species. For P. bifurcatum, total leaf length was significantly different between treatments (p≤0.05). Higher light intensity treatment causes reduction in leaf length for this species. All leaf gas exchange parameters for P. coronarium were statistically different except for Ci (p≤0.05). However, highest light intensity (T4) reduces the Anet, D and WUE value. All treatments also had the value of Fv/Fm of healthy plant in the range from 0.82 to 0.84. P. coronarium were moderately affected in its physiological activity. For P. bifurcatum, significant differences were found for Anet, EL and WUE (p≤0.05). Highest light intensity (T4) showed lowest value in Anet. Fv/Fm in T3 and T4 were below 0.8 indicating that there was a sign of stress. P. bifurcatum was affected under high light intensity. Both species had no higher accumulation of acids at dusk compared to early morning and δ13 C showed both species are C3 plant thus suggesting that both species did not initiate CAM. In water stress treatments, total leaf length and leaf water content of P. coronarium, were significantly different for all treatments (p≤0.05). While for P. bifurcatum,significant differences were found in total leaf length, leaf area and leaf water content (p≤0.05). Higher water stress treatment (T5) reduced growth performance of both species. Anet, gs, EL, D and WUE were significantly different in all treatments of P. coronarium (p≤0.05). For P. bifurcatum, significant differences were found in Anet, gs, EL and D (p≤0.05). T5 reduced Anet,. gs and EL, however its Fv/Fm value was above 0.8 in both species. Both species was moderately affected by water stress. Higher acid accumulation was observed in early morning compared to dusk samples and all treatments were found to have C3 photosynthesis for both species. Therefore this indicates that water stress did not alter physiological pathway for both species

Stable isotope ratio (δ13C) responses of Platycerium bifurcatum at different light intensity levels

Platycerium bifurcatum is an epiphyte known as one of the common plant used for its ornamental value. Living in such environment, they were always exposed to several types of stresses such as water deficit and high light intensity. This plant is known as C3 plant and when exposed to stress environment, it might change its photosynthetic pathway to survive in harsh environment. For determination of the photosynthetic pathway used by plants, isotope screening technique was widely used. Therefore, the objective of this work was to classify the photosynthetic pathway type of P. bifurcatum through investigation of the carbon 13 isotope (δ13C) composition after they were subjected to different levels of light stress. In this study, P. bifurcatum were grown under four different Photosynthetic Active Radiation (PAR) levels which were 20 μm/m2s (T1), 70 μm/m2s (T2), 200 μm/m2s (T3) and 1500 μm/m2s (T4). All measurements were carried out after plants were subjected to 12 weeks of light stress. Two plants from each treatment were selected where two leaves from each plant were used as samples. Leaf samples were dried at 600oC for 48 hr and grounded. Plant responses were measured through its carbon isotope composition by using isotope ratio mass spectrometer. Results showed that there was no significant difference observed for both day and night samples. However, it was confirmed that all treatments were found to have C3photosynthesis in both day and night with T1 value of -27.04 ‰, T2 of -28.33 ‰, T3 of -27.82 ‰ and T4 of -25.61 ‰ at day and T1 with -28.11 ‰, T2 with -28.02 ‰, T3 with -28.50 ‰ and T4 with -27.01 ‰ at night. The results suggested that light stress does not alter the photosynthetic pathway of P.bifurcatum

Street orientation and side of the street greatly influence the microclimatic benefits street trees can provide in summer

Maintaining human thermal comfort (HTC) is essential for pedestrians because people outside can be more susceptible to heat stress and heat stroke. Modification of street microclimates using tree canopy cover can provide important benefits to pedestrians, but how beneficial and under what circumstances is not clear. On sunny summer days, microclimatic measures were made in residential streets with low and high percentages of tree canopy cover in Melbourne, Australia. Streets with east-west (E-W) and streets with north-south (N-S) orientation were repeatedly measured for air temperature, relative humidity, wind speed, solar radiation, and mean radiant temperature on both sides of the street between early morning and midafternoon. Physiological equivalent temperature was estimated to indicate HTC throughout the day. In streets with high-percentage canopy cover, air temperature, relative humidity, solar radiation, and mean radiant temperature were significantly lower than in streets with low-percentage canopy cover. The reductions in air temperature under high-percentage canopy cover were greater for E-W streets (2.1°C) than for N-S streets (0.9°C). For N-S streets, air temperature, mean radiant temperature, and solar radiation were greater on the east pavement in the early morning and greatest on the west pavement in the midafternoon. The midday thermal benefits are restricted to E-W streets, which are oriented in the same direction as the summer sun's zenith. High-percentage canopy cover reduced wind speeds but not enough to offset the other microclimate benefits. These findings can assist urban planners in designing street tree landscapes for optimal HTC in summer, especially in areas of high pedestrian density

A Review of Urban Ecosystem Services Research in Southeast Asia

Urban blue-green spaces hold immense potential for supporting the sustainability and liveability of cities through the provision of urban ecosystem services (UES). However, research on UES in the Global South has not been reviewed as systematically as in the Global North. In Southeast Asia, the nature and extent of the biases, imbalances and gaps in UES research are unclear. We address this issue by conducting a systematic review of UES research in Southeast Asia over the last twenty years. Our findings draw attention to the unequal distribution of UES research within the region, and highlight common services, scales and features studied, as well as methods undertaken in UES research. We found that while studies tend to assess regulating and cultural UES at a landscape scale, few studies examined interactions between services by assessing synergies and tradeoffs. Moreover, the bias in research towards megacities in the region may overlook less-developed nations, rural areas, and peri-urban regions and their unique perspectives and preferences towards UES management. We discuss the challenges and considerations for integrating and conducting research on UES in Southeast Asia based on its unique and diverse socio-cultural characteristics. We conclude our review by highlighting aspects of UES research that need more attention in order to support land use planning and decision-making in Southeast Asia

Predation of potential insect pests in oil palm plantations, rubber tree plantations, and fruit orchards

In human‐modified landscapes, important ecological functions such as predation are negatively affected by anthropogenic activities, including the use of pesticides and habitat degradation. Predation of insect pests is an indicator of healthy ecosystem functioning, which provides important ecosystem services, especially for agricultural systems. In this study, we compare predation attempts from arthropods, mammals, and birds on artificial caterpillars in the understory, between three tropical agricultural land‐use types: oil palm plantations, rubber tree plantations, and fruit orchards. We collected a range of local and landscape‐scale data including undergrowth vegetation structure; elevation; proximity to forest; and canopy cover in order to understand how environmental variables can affect predation. In all three land‐use types, our results showed that arthropods and mammals were important predators of artificial caterpillars and there was little predation by birds. We did not find any effect of the environmental variables on predation. There was an interactive effect between land‐use type and predator type. Predation by mammals was considerably higher in fruit orchards and rubber tree than in oil palm plantations, likely due to their ability to support higher abundances of insectivorous mammals. In order to maintain or enhance natural pest control in these common tropical agricultural land‐use types, management practices that benefit insectivorous animals should be introduced, such as the reduction of pesticides, improvement of understory vegetation, and local and landscape heterogeneity

Effects of vegetation structure on avian biodiversity in a selectively logged hill dipterocarp forest

Southeast Asian tropical rainforests are shrinking at an alarming rate largely due to anthropogenic activities such as logging and agricultural expansion. The loss of tropical rainforests from human exploitations caused devastating and irreversible impacts on avian biodiversity. The establishment of protected areas is an effective tool to mitigate further forest biodiversity loss. However, the ability of degraded rainforest to support avian biodiversity is still remain little known. Here, we assessed bird assemblages in a hill dipterocarp forest in Peninsular Malaysia which was selectively logged almost three decades ago. We examined the effects of site-level attributes, particularly vegetation structure on bird community composition, species richness and abundance of selected feeding guild groups (i.e. insectivorous, carnivorous, and frugivorous). Generally, we found that a selectively logged hill dipterocarp forest can still support a large proportion of forest birds, including those species with high conservation values. Our data also revealed that avian biodiversity was positively related to the number of fallen snags, number of standing snags, number of shrubs, number of trees with DBH < 5 cm, and elevation. In contrast, avian biodiversity was negatively linked to canopy cover percentage, number of palms, and number of trees with DBH 30–50 cm. Our findings suggest the importance of post-harvest site-level attributes management in order to improve avian biodiversity in logged hill dipterocarp forests. Above all, urgent actions are needed to incorporate hill dipterocarp forests, including those already disturbed by logging into protected area networks in Peninsular Malaysia to mitigate forest biodiversity loss

Alley-cropping system can boost arthropod biodiversity and ecosystem functions in oil palm plantations

Oil palm (Elaeis guineensis) is among the fastest expanding crops, due to high global demand for vegetable oils. Large areas of forest are converted into oil palm plantation to meet the market demand in producing countries which causes rapid decline in tropical biodiversity, including arthropods. The alley-cropping system has the potential to promote faunal biodiversity, related ecosystem services and food security in agricultural landscapes. In alley-cropping, a main crop is intercropped with a secondary crop (often a food crop), secondary crops are cultivated in the alleys in between the main crop. We compared arthropod taxonomic richness, arthropod predators and decomposers between five alley-cropping treatments (pineapple, bamboo, black pepper, cacao, bactris), where oil palm is intercropped with another species. In addition, we sampled two control treatments: monoculture oil palm, aged seven and 15 years old. A total of 50,155 arthropod individuals were recorded using pitfall trap sampling, representing 19 orders and 28 families. Fourteen orders belonging to sub-phylum Insecta, three orders from Arachnida (Araneae; Acarinae; Scorpiones) and two orders from Myriapoda (Chordeumatida; Geophilomorpha). We detected an increase in beta-diversity of oil palm production landscape. Specifically, we found that the number of arthropod orders, families and abundance were significantly greater in alley-cropping farming plots than those in monoculture plots. In addition, alley-cropping treatments contained larger numbers of predators and decomposers. Our findings suggest that the alley-cropping system can become a key management strategy to improve biodiversity and ecosystem functions within oil palm production landscapes

Challenges and considerations of applying nature-based solutions in low- and middle-income countries in Southeast and East Asia

Low- and middle-income countries in Southeast and East Asia face a range of challenges related to the rapid pace of urbanisation in the region, the scale of pollution, climate change, loss of ecosystem services and associated difficulties for ecological restoration. Possible pathways towards a more sustainable future lie in the applications of nature-based solutions (NBS). However, there is relatively little literature on the application of NBS in the region, particularly Southeast Asia. In this paper we address this gap by assessing the socio-ecological challenges to the application of NBS in the region – one of the most globally biodiverse. We first provide an overview and background on NBS and its underpinnings in biodiversity and ecosystem services. We then present a typology describing five unique challenges for the application of NBS in the region: (1) Characteristics of urbanisation; (2) Biophysical environmental and climatic context; (3) Environmental risks and challenges for restoration; (4) Human nature relationships and conflicts; and (5) Policy and governance context. Exploiting the opportunities through South-South and North-South collaboration to address the challenges of NBS in Southeast and East Asia needs to be a priority for government, planners and academics.Peer reviewe