Vegetation greenness and photosynthetic phenology in response to climatic determinants

Abstract

Vegetation phenology is a key indicator of vegetation-climate interactions and carbon sink changes in ecosystems. Therefore, it is very important to understand the temporal and spatial variability of vegetation phenology and the driving climatic determinants [e.g., temperature (Ts) and soil moisture (SM)]. Vegetation greenness and photosynthetic phenology were derived using the double logistic (DL) method to enhance vegetation index (EVI) and solar-induced chlorophyll fluorescence (SIF) spring and autumn phenology, respectively. The growing season length (GSL) of greenness phenology (about 100 days) derived EVI was longer than GSL of photosynthetic phenology (about 80 days) derived SIF. Although their overall spatiotemporal pattern trends were consistent, photosynthetic phenology varied 1.4 to 3.1 times more than greenness phenology over time. In addition, SIF-based photosynthetic phenology and EVI-based greenness phenology showed consistent factors of drivers but differed to some extent in spatial patterns and the most relevant preseason dates. Spring photosynthetic phenology was mainly influenced by pre-season mean cumulative Ts (about 90 days). However, greenness phenology was controlled by both pre-seasons mean cumulative Ts [(about 55 days) and mean cumulative SM (about 40 days)]. Autumn photosynthetic phenology was controlled by both periods’ mean cumulative Ts [(about 20 days) and SM (about 20 days)], but autumn greenness phenology was mainly influenced by pre-season mean cumulative Ts (85 days). The comparison analysis of SIF and EVI phenology helps to understand the difference between photosynthetic phenology and greenness phenology at a regional scale.

Assessing the Potential for Photochemical Reflectance Index to Improve the Relationship between Solar-Induced Chlorophyll Fluorescence and Gross Primary Productivity in Crop and Soybean

“…The intricate interplay of environmental factors (e.g., air temperature, light intensity, and water availability) have an impact on how SIF and NPQ are linked to GPP. NPQ and SIF tend to increase with PAR [45]. Low temperature may cause NPQ to increase whereas SIF may show a fall trend, provided that it does not cause damage to chlorophyll molecules [19].…”

“…Low temperature may cause NPQ to increase whereas SIF may show a fall trend, provided that it does not cause damage to chlorophyll molecules [19]. According to some studies conducted in hot environments, the NPQ rises as temperature rises but SIF exhibits the opposite pattern [45,46]. Moreover, water stress made NPQ increase and might decrease SIF [47,48].…”

Combined Effects of Meteorological Factors, Terrain, and Greenhouse Gases on Vegetation Phenology in Arid Areas of Central Asia from 1982 to 2021

“…Typically, plants commence growth when they have sufficient water. Hence, an increase in SM may delay the onset of the spring growing season because plants no longer need to grow rapidly to adapt to dry conditions [41]. Furthermore, using a SEM, temperature was determined to be the primary factor affecting the SOS.…”