Global Ecology and Conservation (Nov 2021)
Temporal effects of climate on vegetation trigger the response biases of vegetation to human activities
Abstract
Quantitatively distinguishing the effects of human activities and climate change on vegetation change is crucial for planning scientific vegetation management measures. Previous studies have employed the residual trend method (RESTREND) and remote sensing data to address this issue. However, the mathematical relationships between climate and remote sensing vegetation index under RESTREND are variable and not comprehensively described due to temporal effects of climate on vegetation. Using Tibetan Plateau (TP), this study investigated how the temporal effects of climate on vegetation trigger response biases of vegetation to human activities under four temporal effects (no temporal effect [No], temporal lag effect [Lag], temporal accumulation effect [Acc], and both temporal lag and temporal accumulation effects [Lagacc]). The results revealed the following. (1) The mean explanation degrees of climatic factors to vegetation growth over entire TP under No, Lag, Acc, and Lagacc effects were 0.41 ± 0.02, 0.42 ± 0.02, 0.44 ± 0.02, and 0.47 ± 0.02, respectively. Therefore, the Lagacc effect is the best temporal effect for establishing the vegetation-climate relationships. (2) Under the Lagacc effect, the temperature exhibited 1.60 ± 0.13 months lag and 4.56 ± 0.28 months accumulation on vegetation growth over entire the TP, whereas the precipitation exhibited 1.57 ± 0.16 months lag and 4.99 ± 0.31 months accumulation. Furthermore, the grids affected by the combined temporal lag and temporal accumulation effects of climatic factors accounted for 43.42–45.78% of the total grids. These indicated the temporal effects of climate on vegetation, and vegetation growth was largely affected by the combined temporal effects of climatic factors. (3) Under the Lagacc effect, 11.6% of the region experienced significant residual increase, and the slope of the residual was 22.2 × 10−4, which was primarily distributed in the north and southeast of the TP. However, the area and slope of significant residual decrease were 1.3% and 24.0 × 10−4, respectively, which were primarily distributed in the center of the TP. Furthermore, the average contributions of human activities on vegetation growth in the regions of residual significant increase and decrease were 54.5% and 55.5%, respectively. Therefore, the Lagacc effect exhibited the smallest influence area and the lowest influence degree for the contribution of human activities on vegetation growth. We thus suggest that the Lagacc effect should be fully considered when establishing the mathematical relationship between climatic factors and the vegetation index.
