Response Mechanism of Leaf Area Index and Main Nutrient Content in Mangrove Supported by Hyperspectral Data

Abstract

Mangrove is the key vegetation in the transitional zone between land and sea, and its health assessment can indicate the deep-level ecological information. The LAI and six key nutrients of mangrove were selected as quantitative evaluation indicators, and the decisive evaluation method of mangrove growth was expected. The mangrove reserve of Dongzhai Port National Nature Reserve in Hainan Province, China, was selected as the study area, with an area of 17.71 km2. The study area was divided into adjacent urban areas, aquaculture areas, and agricultural production areas, and key indicators are extracted from satellite hyperspectral data. The extraction process includes spectral data preprocessing, spectral transformation, spectral combination, spectral modeling, and precision inspection. The spatial distribution of LAI and six key nutrient components of mangrove in the study area were obtained. LAI and Chla need to calculate the index after high-order differentiation of the spectrum; MSTR and Chlb need to calculate the envelope after the second-order differential of the spectrum; TN and TP are directly changed by original or exponential spectrum; the spectral transformation method adopted by TK was homogenization after first-order differential. The results of the strength of nutrient content along the three regions show that there was no significant difference in the retrieval index of mangroves in the three regions, and the overall health level of mangroves was consistent. Chla was the key identification component of mangrove growth and health. The contents of nutrient elements with correlation coefficient exceeding 0.80 include MSTR and TK (0.98), Chla and TP (0.96), Chla and TK (0.87), MSTR and Chla (0.86), MSTR and TK (0.83), and MSTR and TP (0.81). The study quantifies the relationship between different LAI and nutrient content of mangrove leaves from the perspectives of water, leaf biology, and chemical elements, which improved our understanding of the relationship between key components during mangrove growth for the first time.

The role of topography feedbacks in enrichment of heavy metal elements in terrace type region

“…The effects of mining, transportation, rehabilitation, and soil erosion have resulted in the enrichment of these heavy metal elements in the same places (Chen et al, 2022;Giniyatullin et al, 2022) (Figure 6C). This also explains that part of the local farmland will be fallow, because the crops planted often exceed the standard of heavy metals and fail to meet the requirements of safe food (Xue et al, 2020;Chen et al, 2023).…”

Urban Vegetation Extraction from High-Resolution Remote Sensing Imagery on SD-UNet and Vegetation Spectral Features

“…In recent years, the rapid advancements in space optical remote sensing technology have greatly promoted the Earth Observation System [15] and it has emerged as a potent and impactful tool for acquiring regional and global vegetation information [16][17][18][19]. Currently, a variety of optical, hyperspectral, and radar remote sensing data have been widely utilized for vegetation extraction, such as Gaofen and ZY series data [20][21][22] from China, Sentinel series data from the European Space Agency [23][24][25], and Landsat series data from the United States [26].…”

Leaf Area Estimation by Photographing Leaves Sandwiched between Transparent Clear File Folder Sheets

“…It also determines within-and between plant shading and consequent competition [9][10][11]. At the ecosystem level, the stand leaf area or leaf area index (LAI; i.e., total leaf area per unit land area) determines the ecosystem carbon uptake rate [12][13][14], ecosystem transpiration [15,16], and CH 4 emission [17], and substantially affects environmental factors such as soil temperature [18,19]. In agriculture, leaf area has been extensively studied because it is a major determinant of crop yields [20][21][22].…”