Responses of Natural Vegetation to Different Stages of Extreme Drought during 2009–2010 in Southwestern China

Abstract

An extreme drought event is usually a long-term process with different stages. Although it is well known that extreme droughts that have occurred frequently in recent years can substantially affect vegetation growth, few studies have revealed the characteristics of vegetation responses for different stages of an extreme drought event. Especially, studies should address when the vegetation growth was disturbed and how it recovered through an extreme drought event. In this study, we used the Normalized Difference Vegetation Index (NDVI) and Palmer Drought Severity Index (PDSI) to evaluate the response of vegetation to different stages of a severe drought event during 2009-2010 throughout Southwestern China. The PDSI time series indicated that the drought can be divided into three stages, including an initial stage represented by moderate drought (S1), a middle stage represented by continual severe drought (S2), and a final recovery stage (S3). The results revealed that the drought during the initial stage inhibited the growth of grassland and woody savanna, however, forest growth did not decrease during the first stage of droughts, and there was even a trend towards higher NDVI values. OPEN ACCESSRemote Sens. 2015, 7 14040The continual severe drought in the middle stage inhibited growth for all vegetation types, and the woody savanna was affected most severely. In the final stage, all vegetation types underwent recovery, including the grassland that had endured the most severe drought. This study provides observational evidence and reveals that the responses of forest to the extreme drought are different from grassland and woody savanna in the different drought stages.

Spatio-Temporal Variation and Impact Factors for Vegetation Carbon Sequestration and Oxygen Production Based on Rocky Desertification Control in the Karst Region of Southwest China

“…The spatial scale at which vegetation type is measured significantly influences both the ecosystem service extent and its valuation [5,32,35]. Karst ecosystem areas are considerably fragile and heterogeneous [11], and the spatial scale needs to be taken into account in future evaluation of CSOP of this or similar regions. Second, the complex terrain in the karst area presented a challenge for deriving the spatial distribution of annual precipitation that was interpolated from climate records at 97 weather stations within and near the study area of northwest Guangxi, China.…”

“…Karst regions are characterized by thin soil depth (generally not more than 10 cm), and poor surface water retention (infiltration coefficient of 0.3-0.6 or even 0.8) [9][10][11]. A degraded karst ecosystem may recover far more slowly than other ecosystems.…”

Contrasting Responses of Planted and Natural Forests to Drought Intensity in Yunnan, China

“…According to the seasonal changes in the forests' monthly mean EVI in non-drought years, the EVI value changes with the growth of plant leaves (Figure 2b), where the maximum EVI occurs in growing season, especially July and August, for all four forest types and the minimum EVI occurs in the winter (December-March). In recent decades, several drought events with varying intensities and durations have occurred in Yunnan, especially during 2005 and 2009-2014 [32,33], which significantly affected the normal growth of both planted and natural forests. Given the extensive distribution of planted and natural forests as well as the occurrence of drought events, Yunnan Province is an ideal region for studying the responses of forests to drought, and for comparing the potentially different in responses to drought by planted and natural forests, where the overall plan of the study is summarized in Figure 3.…”

“…Climate change can affect forests in many ways, including loss of biodiversity, altitude shifts in species' ranges, and subsequent community reshuffling [1], but one of the most important direct affected the forests [30,32,33]. Thus, this is an ideal region for investigating the different responses of planted and natural forests to extreme drought conditions.…”

Stock Volume Dependency of Forest Drought Responses in Yunnan, China

“…Vegetation indexes based on remote sensing not only directly reflect changes in the growth of vegetation, but also have a high temporal and spatial resolution, and therefore can reflect the differences in the response of vegetation with different attributes to drought. This is why vegetation indexes are always used in characterizing the response of forests to drought on regional and global scales [33,38].…”