ARTICLE | doi:10.20944/preprints201611.0140.v1
Subject: Biology And Life Sciences, Forestry Keywords: understory species; allometric biomass equation; species-specific and multispecies; temperate coniferous and broadleaved mixed forest; northeastern China
Online: 28 November 2016 (04:41:35 CET)
Understory plants are important components of forest ecosystem productivity and diversity. Compared to biomass models of overstory canopy trees, few are available for understory saplings and shrubs and therefore their roles in estimation of forest carbon pools are often ignored. In this study, we harvested 24 understory species including 4 saplings, 9 tree-like shrubs and 11 typical shrubs in coniferous and broadleaved mixed forest in northeastern China and developed the best fit allometric equations of above- and below-ground and total biomass by species-specific or multispecies using morphological measurements of basal diameter, height and crown area as independent variables. The result showed that single basal diameter, height or crown area had good explanatory power for both species-specific and multispecies (p<0.001). The best-fit models included only basal diameter in sapling and tree-like shrubs, and combinations of crown area, height, and basal diameter in typical shrubs. The logarithmic model was most desired among the 4 model forms of linear, quadratic, multiple linear and logarithmic, for species-specific and multispecies. The models we developed should help the estimation of forest ecosystem carbon stocks, especially for belowground component, and provide tools for quantification of individual species biomass of understory plants.
ARTICLE | doi:10.20944/preprints202009.0082.v1
Subject: Environmental And Earth Sciences, Environmental Science Keywords: soil erosion; land cover change; RUSLE; the northeastern
Online: 4 September 2020 (05:00:23 CEST)
Impact of land use and land cover (LULC) change on soil erosion is still imperfectly understood, especially in northeastern China (NEC). Based on the Revised Universal Loss Equation (RUSLE), the variability of soil erosion at different spatial scales following land use changes in1980, 1990, 2000, 2010, and 2017 was analyzed. The regionally spatial patterns of soil loss coincided with the topography, rainfall erosivity, soil erodibility, and use patterns, and around 45% soil loss came from arable land. Regionally, soil erosion rates increased from 1980 to 2010 and decreased from 2010 to 2017, ranging from 3.91 to 4.45 t ha-1 yr-1 with an average of 4.22 t ha-1 yr-1 in 1980-2017. The rates of soil erosion less than 1.41 t ha-1 yr-1 decreased from 1980 to 2010, and increased from 2010 to 2017, and opposite changing patterns occurred in higher erosion classes (i.e., above 5 t ha-1 yr-1). At a provincial scale, Liaoning Province experienced the highest soil erosion rate of 9.43 t ha-1 yr-1, followed by Jilin Province, the east Inner Mongolia, and Heilongjing Province. Arable land continuously increased at the expense of forest in the high-elevation and steep-slope areas from 1980 to 2010, and decreased from 2010 to 2017, resulting in increased areas with erosion rates higher than 7.05 t ha-1 yr-1. At a county scale, around 75% of the countries had soil erosion rate higher than its tolerance level. The county numbers with higher erosion rate increased in 1980-2010 and decreased in 2010- 2017, resulting from the sprawl and withdrawal of arable land. The results indicate that appropriate policies can control soil loss through limiting arable land sprawl in areas of unfavorable regions in the NEC.
ARTICLE | doi:10.20944/preprints202309.1486.v1
Subject: Environmental And Earth Sciences, Atmospheric Science And Meteorology Keywords: Northeastern South America; flash droughts; SEVIRI; NDVI; soil moisture; SPI
Online: 21 September 2023 (12:09:04 CEST)
In a 1.5°C warmer world, the Northeastern (NE) South America’s ecosystems will experience more severe droughts, associated with decreasing rainfall. The severity of flash drought events based on vegetation and surface soil moisture has not been identified over the Caatinga ecosys-tem. This study aimed to characterize the impact of flash drought events on vegetation response via soil moisture over NE South America during the first two decades of the 2000s. Three drought indices were used to characterize flash droughts: the Standardized Difference Vegetation Index (SDVI) derived from Meteosat Second Generation (MSG), the Standardized Precipitation Index (SPI) from ground-data, and the Surface Soil Moisture (SSM) product-based Soil Moisture and Ocean Salinity (SMOS). Results revealed dramatic impacts of flash drought events on vegetation dynamics that caused abrupt changes in the regional vegetation phenology. The regional patterns of flash drought events in 2012 over NE South America were identified and had a severe impact on its Caatinga-like vegetation-dependent moisture response. In 2012, anomalously long dry spells with negative rainfall anomalies in the non-rainy season and persistent on vege-tation greenness and rapidly decreased soil moisture were prominent, thus identifying NE South America to the impacts of flash drought events. Additionally, the results from the trends analysis of radiance fluxes estimated from the MSG satellites over 18 years revealed that an overall drying trend in the NE South America semiarid ecosystem during the last two decades. Here, flash drought events were identified as the conse-quent rainfall deficiency at SPI-3< −1 for a period of five consecutive weeks or more, which the soil moisture content dropping from the 40th percentile to below the 20th percentile, with the NDVI lower than 0.30 unit. These results could be useful to guide flash-droughts early warning systems in NE South America.
ARTICLE | doi:10.20944/preprints202305.2181.v1
Subject: Engineering, Civil Engineering Keywords: debris flow simulation; remote sensing; tree ring; Massflow; northeastern Tibet
Online: 31 May 2023 (07:29:40 CEST)
Rare study on quantitative relationship between energetic impact of debris flows on the intensity and duration of growth disturbances of tree rings was carried out, partly due to lack of feasible approaches and detailed field evidence. In this study, we firstly determine the age of a recent debris flow derived from historic landslide deposits at Qingyang mountain (QYM) on the northeastern Tibet plateau by dendrogeomorphic technique. We acquired the quantitative data of annual widths of tree rings in history and confirmed the influence of debris flow rather than other factors (e.g. climatic event and inset outbreaking) in disturbing the growth of tree rings in a specific year. Using the approach, we determined the age of the debris flow at QYM occurred in 1982, which was speculated to be triggered by high monthly precipitation of July in 1982. Subsequently, based on the boundaries of historic debris flow identified on remote sensing images before and after 1982 and depth-integrated continuum model, we reconstructed the process of 1982-debris flow and obtained the kinematic energy of debris flow impacting on the sampled trees. Based on the study, we observed that two growth disturbance patterns of tree rings influenced by the reconstructed 1982-debris flow were revealed including growth suppression and asymmetric growth. A raw logarithm relationship between duration (i.e. lasting time for the disturbed tree rings to recover the initial width) and intensity of growth disturbances (i.e. growth suppression ratio of disturbed tree rings) was obtained. We concluded that there is a negative exponential relationship between simulated kinematic energy of debris flow impacting on the disturbed trees and time to recover the initial width of corresponding tree rings.
ARTICLE | doi:10.20944/preprints202304.0045.v1
Subject: Environmental And Earth Sciences, Remote Sensing Keywords: Surface Urban heat island; Northeastern region; Sentinel 3; Eco-environmental spaces; Thermal comfort
Online: 4 April 2023 (12:37:09 CEST)
The Surface Urban Heat Island (UHI) is caused by the difference in temperature between the urban and its surrounding areas. However, in the scientific literature, there is no solid methodology defining urban and non-urban areas, which is essential to estimate the SUHI with greater accuracy. This study uses the official national urban areas limit, to obtain the SUHI more accurately on the nine northeastern Brazilian capitals. The land surface temperature was obtained using the Sentinel 3 satellite data for the years 2019 and 2020. Afterward, the maximum and average SUHI, and the complementary indexes were calculated, such as the Urban Thermal Field Variation Index (UTFVI) and the Thermal Discomfort Index (TDI) for the urban areas and their surrounding areas. The Maximum and Average SUHI, obtained values between 1.85 and 8.25 and -4.92 and 2.59 degree difference, respectively, proving the SUHI existence in the study areas. The UTFVI, with values between 0.010 and 0.040, expresses how bad the eco-environmental spaces of urban are. The TDI, with values between 24.61 and 28.89 ºC, expresses the population’s thermal comfort. Therefore, this study provides a better understanding of the surface UHI pioneeringly for the Brazilian Northeast Region.