Convergent evapotranspiration between natural and planted forests: A case study in Loess Plateau, China

Natural and planted forests are two major forms of vegetation restoration and are often assumed to exhibit distinct evapotranspiration ( ET ) patterns. We investigated ET dynamics in a natural secondary oak forest and a nearby planted black locust forest over a ten-year period in a semiarid region. ET was estimated by the soil water budget method, canopy phenology and micrometeorological variables were concurrently monitored in both forests. The growing seasons during 2012–2021 were divided into four distinct periods based on the critical soil water storage ( SWS crit ) and the onset of the rainy season. ET of the two forests exhibited similar inter-annual variations. The seasonal dynamics of ET for both forests displayed a bimodal pattern, jointly driven by climatic and vegetation factors. As water availability improved, the responses of ET to reference evapotranspiration ( ET 0 ) strengthened in both forests. The ET amount in the natural forest exceeded that of the planted forest only in the moistest period. This difference may be attributed to contrasting root growth strategies, whereby the natural oak forest tends to use more water under moist conditions but restricts water use during severe drought. These long-term results indicate that, despite contrasting origins, natural and planted forests can converge in ET under seasonal water variations with highly variable precipitation. Such water-use adaptability may be an important factor in restoration success of the black locust and may offer potential insights for forest management in forest ecosystems with similar semiarid climates.