Inter- and intra-event rainfall partitioning dynamics of two typical xerophytic shrubs in the Loess Plateau of China

Rainfall is known as the main water replenishment in dryland ecosystem, and rainfall partitioning by vegetation reshapes the spatial and temporal distribution patterns of rainwater entry into the soil. The dynamics of rainfall partitioning have been extensively studied at the inter-event scale, yet very few studies have explored its finer intra-event dynamics and the relating driving factors for shrubs. Here, we conducted a concurrent in-depth investigation of rainfall partitioning at inter- and intra-event scales for two typical xerophytic shrubs (Caragana korshinskii and Salix psammophila) in the Liudaogou catchment of the Loess Plateau, China. The event throughfall (TF), stemflow (SF), and interception loss (IC) and their temporal variations within the rainfall event as well as the meteorological factors and vegetation characteristics were systematically measured during the 2014–2015 rainy seasons. The C. korshinskii had significantly higher SF percentage (9.2 %) and lower IC percentage (21.4 %) compared to S. psammophila (3.8 % and 29.5 %, respectively) (p < 0.05), but their TF percentages were not significantly different (69.4 % vs. 66.7 %). At the intra-event scale, TF and SF of S. psammophila was initiated (0.1 vs. 0.3 h and 0.7 vs. 0.8 h) and peaked (1.8 vs. 2.0 h and 2.1 vs. 2.2 h) more quickly, and TF of S. psammophila lasted longer (5.2 vs. 4.8 h), delivered more intensely (4.3 vs. 3.8 mm∙h−1), whereas SF of C. korshinskii lasted longer (4.6 vs. 4.1 h), delivered more intensely (753.8 vs. 471.2 mm∙h−1). For both shrubs, rainfall amount was the most significant factor influencing inter-event rainfall partitioning, and rainfall intensity and duration controlled the intra-event TF and SF variables. The C. korshinskii with larger branch angle, more small branches and smaller canopy area, has an advantage to produce stemflow more efficiently over S. psammophila. The S. psammophila has lower canopy water storage capacity to generate and peak throughfall and stemflow earlier, and it has larger aboveground biomass and total canopy water storage of individual plant to produce higher interception loss compared to C. korshinskii. These findings contribute to the fine characterization of shrub-dominated eco-hydrological processes, and improve the accuracy of water balance estimation in dryland ecosystem.

Automated satellite remote sensing of giant kelp at the Falkland Islands (Islas Malvinas)

Giant kelp populations that support productive and diverse coastal ecosystems at temperate and subpolar latitudes of both hemispheres are vulnerable to changing climate conditions as well as direct human impacts. Observations of giant kelp forests are spatially and temporally uneven, with disproportionate coverage in the northern hemisphere, despite the size and comparable density of southern hemisphere kelp forests. Satellite imagery enables the mapping of existing and historical giant kelp populations in understudied regions, but automating the detection of giant kelp using satellite imagery requires approaches that are robust to the optical complexity of the shallow, nearshore environment. We present and compare two approaches for automating the detection of giant kelp in satellite datasets: one based on crowd sourcing of satellite imagery classifications and another based on a decision tree paired with a spectral unmixing algorithm (automated using Google Earth Engine). Both approaches are applied to satellite imagery (Landsat) of the Falkland Islands or Islas Malvinas (FLK), an archipelago in the southern Atlantic Ocean that supports expansive giant kelp ecosystems. The performance of each method is evaluated by comparing the automated classifications with a subset of expert-annotated imagery (8 images spanning the majority of our continuous timeseries, cumulatively covering over 2,700 km of coastline, and including all relevant sensors). Using the remote sensing approaches evaluated herein, we present the first continuous timeseries of giant kelp observations in the FLK region using Landsat imagery spanning over three decades. We do not detect evidence of long-term change in the FLK region, although we observe a recent decline in total canopy area from 2017–2021. Using a nitrate model based on nearby ocean state measurements obtained from ships and incorporating satellite sea surface temperature products, we find that the area of giant kelp forests in the FLK region is positively correlated with the nitrate content observed during the prior year. Our results indicate that giant kelp classifications using citizen science are approximately consistent with classifications based on a state-of-the-art automated spectral approach. Despite differences in accuracy and sensitivity, both approaches find high interannual variability that impedes the detection of potential long-term changes in giant kelp canopy area, although recent canopy area declines are notable and should continue to be monitored carefully.

Dynamics of Spring Regrowth and Comparative Production Performance of 50 Autumn-Sown Alfalfa Cultivars in the Coastal Saline Soil of North China

Alfalfa (Medicago sativa L.) production is affected by many factors, including management practices, soil conditions, and the environmental elements of the target area. Varietal differences, in terms of agronomic performance and forage yield, among 50 alfalfa cultivars under six harvest systems following regrowth were evaluated during the growing season of 2019–2020 under non-irrigated rainfed conditions in a coastal saline-alkali soil region of North China. Days to harvesting, plant height, canopy area, growth rate, and forage yield were assessed to rank the cultivars. Furthermore, the key factor influencing the regrowth of the second year after over-wintering was identified based on the growth status before over-wintering by using the Boston Matrix method. Results showed significant (p < 0.05) differences among cultivars and harvests regarding plant height, canopy area, and forage yield. Alfalfa forage yield ranged between 24.2 t ha−1 yr−1 and 32.7 t ha−1 yr−1. The highest forage yield was obtained in cultivar Guochan No.1, and was lowest in cultivar Magnum 601. Forage yield reached the greatest values for the first harvest, and then decreased gradually and changed stably. The forage yield of the third, fourth, fifth, and sixth harvest ranged from 3.4 t ha−1 to 4.3 t ha−1 (averaged across 50 cultivars), which represented 10.8% to 15.2% of the annual total forage production. We also observed that forage yield correlated strongly, but negatively, with the growth rate. According to subordinate function value analysis, Womu No.1, WL440HQ, Weston, Surprise, and WL354HQ proved optimum cultivars for general cultivation in this coastal area. In future, development of alfalfa cultivars with improved regrowth and tolerance to heavy saline-alkali soil and early spring drought would be necessary to increase forage yield under rainfed conditions in coastal saline-alkali areas of North China.

Structure, composition and carbon stocks of woody plant community in assisted and unassisted ecological succession in a Tamaulipan thornscrub, Mexico

Background Ecological restoration is a process that helps the recovery of an ecosystem that has been degraded, damaged or destroyed. The success of restoration actions depend on the understanding of the processes, mechanisms and factors that guide vegetation dynamics. The restoration of plant communities can be made by unassisted (passive restoration, where the community recover by itself) and assisted (active restoration) ecological succession. It is imperative to know the scope of both types of activities to guide future restoration actions by evaluating the properties and functioning of the intervened communities. Methods Variance analysis of the carbon (C) stocks, basal area, canopy area, Shannon–Weaver index values, specific richness and abundance of three Tamaulipan thornscrub communities (assisted natural succession area, unassisted natural succession area and control area) was performed. Furthermore, a similarity analysis between the sampling areas using the floristic composition (abundance) was performed. Results In total, 11 families, 17 genera and 20 species of vascular plants were registered. The richness of species and abundance ranked as follows per area: assisted ecological natural succession > control > unassisted ecological natural succession. The species composition between sampling areas showed a low number of common species between plant communities. Conclusions The values of species richness, diversity, abundance, basal area, and canopy area of the assisted natural succession vegetal community was statistical similar to the control plan community. The values of C stocks showed that assisted ecological succession could recover not only structure and composition attributes but also this key ecosystem property.

Scarcity of Major Resistance Genes Against Verticillium Dahliae

Verticillium dahliae is a soil-borne fungal pathogen that causes vascular wilt disease in numerous plant species. The only described qualitative resistances against V. dahliae are the Ve1 gene and the V2 locus in tomato. These resistances have been overcome by virulent strains. We tried to identify additional resistances. Out of the methods we tested, comparing the canopy area of V. dahliae-inoculated plants with mock-inoculated plants yielded the best discriminative power in resistance tests. Out of six wild tomato accessions that were previously reported to possess some resistance, Solanum pimpinellifolium G1.1596 and S. cheesmanii G1.1615 displayed the lowest stunting and the least colonization by V. dahliae. Recombinant inbred line (RIL) populations were developed of both populations. No QTLs were identified in the G1.1596 RIL population. In the G1.1615 population, four small-effect QTLs were associated with reduced stunting. Many studies in other hosts also failed to discover major resistance genes against V. dahliae. We hypothesize that the scarcity of major resistance genes against V. dahliae is caused by its endophytic behaviour in nature. The limited damage in nature would not lead to evolutionary pressure to evolve major resistances. However, in agriculture V. dahliae can behave more pathogenic, leading to serious damage.

Evaluation of factors influencing the eradication of annual bluegrass (Poa annua L.) from Point Thomas Oasis, King George Island, Maritime Antarctica

From 2014 to 2018, we performed three on-site eradication actions of Poa annua occurring on King George Island. We aimed at (1) assessing the population response to eradication efforts, (2) evaluating the campaign success, and (3) identifying the most important factors likely to influence eradication success. The first partial eradication action reduced the initial population of around 1500 tussocks to around 1100 tussocks with less than 4 m2 canopy area. In treated locations, we observed high re-establishment where no soil removal was performed, while only a marginal recruitment where plants were removed with associated soil. In the 2017/2018 season, we recorded over 1800 tussocks, which all were subsequently removed. Performing eradication according to the prescribed scheme (plant and soil removal) should result in eradication success. We evaluate that the probability of successful eradication of the population is high because of small size and number of separate infestation sites, complete spatial and ecological isolation of infestation, high accessibility of target population, and well-known current location of infestation sites. The factors which reduce the likelihood of eradication success are long reaction time, high adaptation of the species to new environmental conditions, and high propagule longevity. Reinvasion possibility and frequent personnel changes in the eradication team resulting in varying levels of personnel awareness and experience may also negatively influence eradication success. An invasion, not managed for many years, may still be targeted, but its successful eradication depends on the “human factor”, which may drive the success of the action in opposing directions.

Performance of Seven Tea Accessions in North-central Florida: Correlations between Potential Yield and Growth Parameters over 2 Years

Tea (Camellia sinensis) is a promising new specialty crop for production in Florida. However, few data exist on the establishment phase of tea plantings in this environment and on how early growth parameters may predict yield potential. We tested seven accessions of tea grown under field conditions in north-central Florida for leaf yield and growth parameters—namely, pruned biomass, trunk diameter, trunk height, trunk width, trunk height × width, and canopy area—in the second and third years after planting. Our analyses indicated that the accession Fairhope performed best overall. Pruned biomass and trunk diameter were the best predictors for leaf yield. The harvested leaves produced good-quality black tea, with caffeine levels comparable to commercially available tea. These data indicate that nondestructive measurements of growth can be useful to assess yield potential of tea, and that regionally adapted tea accessions can be identified during the establishment stage.

EFETIVIDADE NA RESTAURAÇÃO DE FLORESTAS TROPICAIS: COMO O DESEMPENHO DIFERENCIAL DAS ESPÉCIES E O CONTEXTO ECOLÓGICO INFLUENCIAM O ESTABELECIMENTO E OCUPAÇÃO

Restaurar as florestas tropicais é essencial para enfrentar mudanças climáticas globais, manter e conservar a diversidade e os serviços ecossistêmicos. Foi analisado o estabelecimento e ocupação em três estratégias de restauração florestal (Plantio em Mudas em Área Total (PAT), Ilhas de Diversidade (ID) e Semeadura Direta (SD)) da vegetação florestal associada a cursos d’água. Foram avaliados: o número de indivíduos, intensidade de perfilhamento, biomassa acima do solo, área de copa, diâmetro e altura médios, por indivíduo, em 58 unidades amostrais (10 x 30 m) distribuídas entre as estratégias após 2,5 anos da implantação. Também foram avaliadas as principais espécies e suas similaridades entre as estratégias. A SD proporcionou maior efetividade quanto ao Número de indivíduos, Biomassa e Área de Copa, enquanto, a intensidade de perfilhamento foi maior nas ID e não houveram diferenças quanto a média de altura e diâmetro. Cada estratégia apresentou um conjunto particular de espécies de maior sucesso e as mais similares foram aquelas que utilizaram mudas (PAT e ID). A estratégia SD destacou-se no estudo, especialmente quando considerados aspectos ecológicos e custos envolvidos. As espécies contribuíram na diferenciação das estratégias, pois, proporcionaram funções ecológicas distintas que influenciam processos ecológicos em nível de comunidade e indivíduos. Palavras-chave: restauração florestal; nucleação; semeadura direta; plantio de mudas; floresta Amazônica. Effectiveness in the tropical forest restoration: how the differential performance of species and ecological context affect the establishment and occupation ABSTRACT: Restoring tropical forests is essential to address global climate change, to maintain and conserve diversity and ecosystem services. The establishment and occupation of three forest restoration strategies (Total Seedling Planting (PAT), Diversity Islands (ID) and Direct Seeding (SD)) of the forest vegetation associated with watercourses was analyzed. It were evaluated: the number of individuals, resprouting intensity, above-ground biomass, canopy area, average diameter and height, per individual, in 58 sample units (10 x 30 m) distributed among the strategies after 2.5 years of implantation. It was also evaluated the main species and their similarities between the strategies. The SD provided more effective as the number of individuals, biomass and treetop area, while the intensity of resprouting was higher in ID and there were no differences in mean height and diameter. Each strategy presented a particular set of most successful species and the most similar were those that used seedlings (PAT and ID). The highlight of the SD strategy is magnified when considering ecological perspectives, and social costs involved. The species contributed to the differentiation of strategies, because they provide distinct ecological functions that influence ecological processes at the community level and individuals. Keywords: forest restoration; nucleation; direct seeding; seedling planting; Amazon rainforest.

Growth of three types of sengon (Paraserianthes spp.) in varying planting spaces in agroforestry system

Sopacua F, Wijayanto N, Wirnas D. 2021. Growth of three types of sengon (Paraserianthes spp.) in varying planting spaces in agroforestry system. Biodiversitas 22: 4423-4430. Sengon (Paraserianthes spp.) is a fast-growing tree species that is commonly cultivated in the agroforestry system by communities in Indonesia, mainly on Java Island. Among several types of sengon, Solomon sengon is currently gaining popularity due to the fast growth in height and stem diameter. Nonetheless, the spacing layout of selected sengon types is unclear, including Solomon sengon, which yields more optimal growth. This study aimed to examine the growth of three sengon types (i.e., Solomon F2, Solomon F1, and local Kendal) in three spacing patterns, namely 1.5x1.5m, 3x1.5m, and 3x3m. This research was conducted from October 2019 to January 2020 (three months) in the Cikabayan Forest, Bogor Agricultural University, Bogor, West Java. The parameters of sengon growth observed were plant height, height growth rate, stem diameter, stem diameter growth rate, tree volume, and canopy area. Data analysis was performed using ANOVA and continued with Duncan's. The results showed that all types of sengon had optimal growth in the agroforestry system at various spacings. The growth of Solomon F2 adapted well to denser spacings (1.5x1.5m and 1.5x3m) with the highest averages in plant height, stem diameter, volume, and canopy area of ??10.50 m, 8.65 cm, 0.36 m3, and 5.39 m2. Local Kendal had optimal growth at a wider spacing (3x3m) with the highest average stem diameter, volume, and canopy area of ??8.96 cm, 0.043 m3, and 1063 m2. While Solomon F1 adapted well to the three spacings with the highest average in plant height, the growth rate of plant height, stem diameter, volume, and canopy area of ??10.05 m, 1.54 m, 8.59 cm, 0.042 m2, and 2075.30 m2. In general, it can be concluded that the Solomon F1 sengon can adapt well to narrow distances or wide distances. While Solomon F2 is more recommended to be planted at a narrower distance and Kendal local sengon is more recommended to be planted at a wider distance to get optimal growth.

Effect of Fermentation Extracts against Bemisia tabaci on Chilli Pepper (Capsicum annuum)

This experiment was aimed to determine the effects of application of fermentation extracts on the development of pepper yellow leaf curl and whitefly on chilli. Experiment arranged in a completely randomized block design with four treatments (water as control, fermentations extracts named TSNGlu, BP4, and BP4Glu). The results showed symptoms in the form of curling of young leaves. The color of the leaves was relatively green. Yellow symptoms commonly found when severe were not found in the experiment. The symptoms of severe disease are marked in yellow at the top of the leaf and remain green at the bottom. The laboratory used 350 lux (underexposed light) so the symptoms become slight. ack of light intensity made plants etiolated and could not carry out photosynthesis properly. Each experiment consisted of 4 fermentation extract treatments. Each treatment. Overall, all treatments without fermentation and also AUDPC of the disease did not significantly affect the treatment of fermented extract both the incidence and severity of the low pepper yellow leaf curl virus. The treatment by spraying did not significantly affect the population of whitefly, except at 7 days after infestation, inversely proportional to the spraying treatment by means of discharge significantly affected from 14 days after infestation. The increase in plant height spray treatment did not have a significant effect and for spraying treatment with extraction of fermentation did not significantly affect the canopy area of ​​the plant canopy.