ISPRS Journal of Photogrammetry and Remote Sensing ( IF 12.7 ) Pub Date : 2019-01-03 , DOI: 10.1016/j.isprsjprs.2018.12.014 Humberto Alves Barbosa , T.V. Lakshmi Kumar , Franklin Paredes , Simon Elliott , J.G. Ayuga
The Caatinga semi-arid vegetation in Northeast region of Brazil (NEB) provides a unique opportunity for studying the vegetation in response to recurring droughts, because of its negative impacts on soil erosion. Surprisingly, however, the response of Caatinga vegetation to a recent multi-year drought across the entire semi-arid NEB has not been studied in detail. This study analyses the spatiotemporal patterns of drought impact on the Caatinga vegetation between 2008 and 2016. Yet previous research has shown that a linear relationship exists between rainfall and Caatinga vegetation at interannual timescale. Because of the strong large-scale control of precipitation, year-to-year rainfall variations have a notable degree of spatiotemporal heterogeneity in semi-arid NEB. We exploit this relationship by developing the local-to regional-scale rainfall-Normalized Difference Vegetation Index (NDVI) distribution over the Caatinga vegetation, using daily rainfall time series from in situ weather stations, and daily Meteosat Second Generation (MSG) NDVI time series. Results showed that the drought impact (2012–2015) through the rainfall deficit dynamics influenced the dynamics of vegetative drought in the Caatinga vegetation where exhibit a strong decrease in vegetation activity, contrasting with irrigated croplands that exhibit little sensitivity to drought. It is the longest, continuous drought on the historical record (1901 onwards). The severe drought year of 2012 affected more than 26% of the vegetated area in the region. Over the 2012–2016 period, the positive trend observed in vegetation greenness is largely explained by a positive trend in the rainfall over 45% of the Caatinga vegetation, with the three months lagged rainfall (R2 = 0.62 with p < 0.05). This suggests that the vegetation greenness occurs in some portions of Caatinga region is mainly due to inadequate land management practices (i.e., irrigation with poor drainage, crop planting, bush encroachment, grazing-converted, pasture, etc.) often in combination with recurring droughts.
中文翻译:
使用Meteosat-SEVIRI归一化植被指数评估Caatinga对干旱的反应(2008–2016)
巴西东北地区(NEB)的Caatinga半干旱植被,由于其对土壤侵蚀的负面影响,为研究该植被应对反复干旱提供了独特的机会。然而,令人惊讶的是,尚未详细研究整个半干旱NEB上Caatinga植被对最近多年干旱的响应。这项研究分析了干旱对Caatinga植被在2008年至2016年之间的时空分布格局。但先前的研究表明,降雨与Caatinga之间存在线性关系年际尺度上的植被。由于强大的大规模降水控制,在半干旱NEB中,逐年降雨变化具有明显的时空异质性。我们利用原地气象站的每日降雨时间序列和Meteosat第二代(MSG)的每日NDVI时间序列,通过开发Caatinga植被上的局部到区域尺度的降雨归一化植被指数(NDVI)分布,来利用这种关系。。结果表明,干旱(2012-2015年)通过降雨不足动态影响了Caatinga植物性干旱的动态。植被中植被活动明显减少的植被,而灌溉耕地对干旱几乎没有敏感性。这是历史记录上最长,持续的干旱(1901年以来)。2012年的严重干旱年份影响了该地区超过26%的植被。在2012–2016年期间,观察到的植被绿色度呈正向趋势的主要原因是Caatinga植被超过45%的降雨呈正向趋势,而三个月的降雨滞后(R 2 = 0.62,p <0.05)。这表明在Caatinga地区的某些地区发生植被绿化的主要原因是土地管理实践不充分(即,排水不畅的灌溉,农作物种植,灌木丛侵占,牧场改建,牧场等),通常与干旱反复发生相结合。