Physiological responses of Triplaris gardneriana Wedd. seedlings (Polygonaceae) under intermittent drought

Triplaris gardneriana Wedd is a deciduous riparian tree occurring in areas with different climatic conditions in Brazil, from the rainforest to the tropical dry forest. An increase in global temperature and drought events can change the growth pattern and establishment of the species. To evaluate the effects of intermittent drought on the growth of T. gardneriana seedlings, an experiment was performed using seedlings with one month old subjected to three water treatments (daily irrigation as control, and intermittent drought through cycles of water suppression of seven (S7) and 14 days-intervals (S14) between watering. Growth, biomass production and partitioning, relative water content (RWC), the accumulation of organic solutes, protoplasmic integrity and phenotypic plasticity index (PPI) were evaluated for a better understanding about its drought tolerance level. Intermittent drought severely affected plants growth in S14 plants, showing lower plant height, number of leaves, leaf area, and dry biomass. RWC was reduced, while carbohydrates and proline contents increased in response to drought stress. Protoplasmic damage increased electrolyte leakage in plants subjected to severe stress. However, T. garderiana demonstrated moderate tolerance to water deficit. The plastic changes observed were more physiological than morphological. Therefore, T. gardneriana seems to be a moderately tolerant species to intermittent drought.

Exploring Local Riverbank Sediment Controls on the Occurrence of Preferential Groundwater Discharge Points

Groundwater discharge to rivers takes many forms, including preferential groundwater discharge points (PDPs) along riverbanks that are exposed at low flows, with multi-scale impacts on aquatic habitat and water quality. The physical controls on the spatial distribution of PDPs along riverbanks are not well-defined, rendering their prediction and representation in models challenging. To investigate the local riverbank sediment controls on PDP occurrence, we tested drone-based and handheld thermal infrared to efficiently map PDP locations along two mainstem rivers. Early in the study, we found drone imaging was better suited to locating tributary and stormwater inflows, which created relatively large water surface thermal anomalies in winter, compared to PDPs that often occurred at the sub-meter scale and beneath riparian tree canopy. Therefore, we primarily used handheld thermal infrared imaging from watercraft to map PDPs and larger seepage faces along 12-km of the fifth-order Housatonic River in Massachusetts, USA and 26-km of the Farmington River in Connecticut, USA. Overall, we mapped 31 riverbank PDPs along the Housatonic reach that meanders through lower permeability soils, and 104 PDPs along the Farmington reach that cuts through sandier sediments. Riverbank soil parameters extracted at PDP locations from the Soil Survey Geographic (SSURGO) database did not differ substantially from average bank soils along either reach, although the Farmington riverbank soils were on average 5× more permeable than Housatonic riverbank soils, likely contributing to the higher observed prevalence of PDPs. Dissolved oxygen measured in discharge water at these same PDPs varied widely, but showed no relation to measured sand, clay, or organic matter content in surficial soils indicating a lack of substantial near-surface aerobic reaction. The PDP locations were investigated for the presence of secondary bank structures, and commonly co-occurred with riparian tree root masses indicating the importance of localized physical controls on the spatial distribution of riverbank PDPs.

Riparian Tree Vegetation Diversity Salah Nama Island in Banyuasin, South Sumatera

Highlight Research:Riparian plants play an important role in maintaining the balance of an aquatic ecosystem.The diversity of riparian aquatic plants on the island of Salah Nama BanyuasinData collection on riparian plants used the quadratic transect methodThe results showed that there were 21 types of riparian aquatic plants in 16 families.The highest composition is in the Lythraceae family, namely Sonneratia acidaAbstractRiparian plants play an important role in maintaining the balance of an aquatic ecosystem. The missing plant components from a water can cause sedimentation and change the microhabitat in these waters. The purpose of the study is to determine the diversity of riparian aquatic plants on the island of Salah Nama Banyuasin. The research was conducted in August 2016, November 2016, and January 2017 at Salah Nama Island Mariana Ilir Banyuasin 1, South Sumatra. Sampling was done by using the purposive sampling method. Determination of the sampling location used GPS (Global positioning system). Observation stations consisted of 5 sampling locations. The method of taking water plants was done in exploratory way. Data collection on riparian plants used the quadratic transect method measuring 1 m x 1 m. Samples of riparian plants were taken then wrapped with newspaper or paper and put into large plastic, labeled then taken to the testing laboratory Institute Inland fisheries and extension, Palembang. The results showed that there were 21 types of riparian aquatic plants in 16 families. The highest composition is in the Lythraceae family, namely Sonneratia acida. The diversity index of aquatic plants ranges from 1 <H'<3 in the stable condition category. Based on the results of the study, the riparian plant species that dominated the most were Sonneratia sp. The conclusion that can be drawn is that the diversity of riparian plants on the island of Salah Nama is in the medium category, the dominant riparian plants are Sonneratia sp.

Characterization of Riparian Tree Communities along a River Basin in the Pacific Slope of Guatemala

Ecosystem conservation in Mesoamerica, one of the world’s biodiversity hotspots, is a top priority because of the rapid loss of native vegetation due to anthropogenic activities. Riparian forests are often the only remaining preserved areas among expansive agricultural matrices. These forest remnants are essential to maintaining water quality, providing habitats for a variety of wildlife and acting as biological corridors that enable the movement and dispersal of local species. The Acomé river is located on the Pacific slope of Guatemala. This region is heavily impacted by intensive agriculture (mostly sugarcane plantations), fires and grazing. Most of this region’s original forest is now restricted to forest remnants concentrated along the riverbank. However, the botanical composition and species diversity of the riparian communities has not been characterized. This baseline information is essential to develop restoration strategies and management plans. This study aimed to characterize the riparian tree communities along the Acomé riverbank by systematically collecting herbarium specimens and photographic material for trees over 10 cm DBH (diameter at breast height). Cluster analysis was used to identify the main riparian communities, and diversity indices were calculated for each community. A total of 115 tree species were identified, belonging to 91 genera and 43 families. The cluster analysis suggested the presence of four riparian tree communities along an altitudinal gradient. Rhizophora mangle, Cecropia obtusifolia, Guazuma ulmifolia, and Brosimum costaricanum were the dominant species of the identified communities. This research will support ongoing restoration efforts and biological connectivity plans in this region.

Climate-driven divergence in plant-microbiome interactions generates range-wide variation in bud break phenology

Soil microbiomes are rapidly becoming known as an important driver of plant phenotypic variation and may mediate plant responses to environmental factors. However, integrating spatial scales relevant to climate change with plant intraspecific genetic variation and soil microbial ecology is difficult, making studies of broad inference rare. Here we hypothesize and show: 1) the degree to which tree genotypes condition their soil microbiomes varies by population across the geographic distribution of a widespread riparian tree, Populus angustifolia; 2) geographic dissimilarity in soil microbiomes among populations is influenced by both abiotic and biotic environmental variation; and 3) soil microbiomes that vary in response to abiotic and biotic factors can change plant foliar phenology. We show soil microbiomes respond to intraspecific variation at the tree genotype and population level, and geographic variation in soil characteristics and climate. Using a fully reciprocal plant population by soil location feedback experiment, we identified a climate-based soil microbiome effect that advanced and delayed bud break phenology by approximately 10 days. These results demonstrate a landscape-level feedback between tree populations and associated soil microbial communities and suggest soil microbes may play important roles in mediating and buffering bud break phenology with climate warming, with whole ecosystem implications.