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Using Vegetative Indices to Quantify Agricultural Crop Characteristics

Kokhan Svitlana, Vostokov Anatoliy

Journal of Ecological Engineering

2020

Vol. 21, nr 4

120--127

In this study, the winter wheat aboveground biomass (AGB), leaf area index (LAI) and leaf nitrogen concentration (LNC) were estimated using the vegetation indices, derived from a high spatial resolution Pleiades imagery. The AGB, LAI and LNC estimation equations were established between the selected VIs, such as NDVI, EVI and SAVI. Regression models (linear and exponential) were examined to determine the best empirical regression equations for estimating the crop characteristics. The results showed that all three vegetation indices provide the AGB, LAI and LNC estimations. The application of NDVI showed the smallest value of RMSE for the aboveground biomass estimation at stem elongation and heading of winter wheat. EVI gave the best significant estimation of LNC and showed better results to quantify winter wheat vegetation characteristics at stem elongation phase. This study demonstrated that Pleiades high spatial resolution imagery provides in-situ crop monitoring.

Variations in foliar nutrient resorption efficiency of different plant growth forms in a temperate sandy grassland

Mao W., Li Y., Cui J., Zuo X., Zhao X.

Polish Journal of Ecology

2011

Vol. 59, nr 2

355-365

Foliar nutrient resorption is an important strategy which allows leaf nutrients to be reused rather than lost with leaf fall, particularly in nutrient-poor ecosystems where even small nutrient losses can have significantly negative impacts on plant survival, competitive ability, and fitness. However, plants vary greatly in nitrogen (N) and phosphorus (P) resorption among plant growth forms during leaf senescence, which may be vital to understand the role of plant growth forms in ecosystem functioning. Green and senesced leaf N and P concentrations of 39 plant species in sandy grassland (Horqin Sand Land) of northern China were analyzed to detect variations of nutrient resorption efficiency among plant growth forms. The results showed that nitrogen resorption efficiency (NRE) ranged from 29% to 74%, with an average ([plus or minus] SD) of 50.3 [plus or minus] 11.2%, and phosphorus resorption efficiency (PRE) varied among species between 46% and 82%, with a mean ([plus or minus] SD) of 68.4 [plus or minus] 6.9%, suggesting that nutrient resorption is a vital nutrient conservation strategy in this ecosystem. In addition, NRE and PRE differed significantly among the dominant plant growth forms in this sandy grassland. NRE for N-fixing species and graminoids were significantly lower relative to NRE for shrubs and forbs, but mean PRE of graminoids was significantly higher than those of N fixers, shrubs and forbs. These data give indirect evidence that the differentiation of N and P conservation serve as an important mechanism permitting the co-existence of growth forms in arid systems.