Efectos de la invasión del ligustro, Ligustrum lucidum, en la dinámica hídrica de las Yungas del noroeste Argentino

Abstract

SUMMARYArgentinean Yungas (subtropical montane forests) have high biodiversity and play a key role in regional watershed regulation. Ligustrum lucidum (glossy privet), native of China, is one of the dominant exotic tree species in secondary forests of this ecoregion. Due to its high growth rates and green foliage throughout the year -in contrast to native forests which are partially deciduous-the hypothesis is that water availability is reduced in glossy privet forests, especially during dry season (winter-spring). Six pairs of plots both in native and secondary glossy privet dominated forests in Sierra San Javier, Tucumán, Argentina were sampled. Soil moisture, by measuring both volumetric water content and water potential, and estimated productivity of different types of forests, through normalized difference vegetation index (NDVI derived from satellite imagery), were monitored. During 2011 -2012 dry seasons, soil volumetric water content in glossy privet forests was 32.5 % and 24 % lower than in native forests; while soil water potential was respectively eight and four times lower. In glossy privet forests NDVI values were 8.5 % higher than in native forests; particularly in lower altitude forests and those with a higher winter-spring water deficit. These results suggest that the glossy privet forest would be consuming more water, especially during the dry season, due to more prolonged phenology activity compared to native forests. In consequence, glossy privet invasion in Argentinean Yungas could alter water functioning of this ecosystem.Key words: forest-phenology, invasion by exotic trees, MODIS, NDVI, water consumption. RESUMENLas Yungas argentinas (bosques de montaña) tienen alta biodiversidad y un rol clave en la regulación hídrica. El ligustro (Ligustrum lucidum) es una de las especies exóticas que dominan sus bosques secundarios. Debido a sus altas tasas de crecimiento y follaje verde todo el año, se planteó la hipótesis de que la disponibilidad de agua en el suelo se reduciría en bosques de ligustro en comparación con bosques nativos, principalmente durante la época seca (invierno-primavera). Se trabajó en seis pares de parcelas de bosques nativos y bosques secundarios monodominantes de ligustro en la Sierra San Javier, Tucumán, Argentina. Se registró la humedad edáfica mediante mediciones de contenido volumétrico y potencial hídrico y se estimó la productividad de los distintos tipos de bosque mediante el índice de vegetación de diferencia normalizada (NDVI). Durante la época seca de 2011 y 2012, los suelos en ligustrales presentaron un contenido volumétrico de agua 32,5 % y 24 % y un potencial hídrico en el suelo ocho y cuatro veces menor. Se observaron mayores valores de NDVI (8,5 %) en bosques de ligustro que en bosques nativos, principalmente en las selvas localizadas a menor altura y con mayor déficit hídrico inverno-primaveral. Los resultados sugieren que el bosque de ligustro estaría consumiendo mayor cantidad de agua, sobre todo en la época seca, debido a una actividad fenológica más prolon...

A Global Review of Ligustrum Lucidum (OLEACEAE) Invasion

“…Studies assessing the variation among the year of the normalized difference vegetation index (NDVI), used as a proxy of transpiration (Zhang et al 2001), show higher values in L. lucidum – invaded forests than in native forests, particularly during the dry season, in subtropical montane forests of NW Argentina and dry forests of Central and northern Argentina (Hoyos 2007 ; Zamora Nazca et al 2014 ; Whitworth Hulse 2018 ). Zamora Nazca et al ( 2014 ) and Whitworth Hulse ( 2018 ) found that L. lucidum-invaded forests present 15% less annual average water content than adjacent native forests, and these differences increased to values of 30%, during the dry season. Deep soil water availability of small catchments is also lower in L. lucidum-invaded forest than in native forests dominated by Lithraea molleoides in dry forests of Central Argentina (Whitworth Hulse 2018 ), suggesting a reduction of groundwater recharge.…”

CONTAIN: Optimising the long-term management of invasive alien species using adaptive management

“…Finally, once the species is well established, privet may form mono-specific stands that will dominate the entire tree community of the invaded habitat. The effects of privet on native forest are evident, modifying community species composition (Ayup et al 2014) and ecosystem functions (such as nutrient turnover), and producing shifts in environmental conditions such as soil moisture and light availability (Zamora Nasca et al 2014). Additionally, privet can slowly invade the native forests without human intervention (Malizia et al 2017), because the species is dispersed not only by humans but also by native fruit-eating birds (Aragón and Groom 2003).…”

Invasion of Ligustrum lucidum (Oleaceae) in subtropical secondary forests of NW Argentina: declining growth rates of abundant native tree species

“…For example, Zamora Nasca et al. () suggested that secondary forests dominated by L. lucidum (i.e. monospecific stands) consumed more water compared to native secondary forests, especially during the dry season (winter–spring); indeed soil water content in secondary forests dominated by L. lucidum was ca.…”

“…productivity and water dynamics; Zamora Nasca et al. ). This idea is consistent with the results of Hoyos et al.…”

“…28% lower than in native secondary forests. This may result, in part, from the maintained green foliage throughout the year in contrast to native forests, which are partially deciduous (Zamora Nasca et al 2014), and from the extremely dense root system of L. lucidum (pers. obs.).…”