How did the regional water-heat distribution in oasis area vary with the different spatial patterns and structures of shelterbelt system—A case study in Ulan Buh desert oasis

Abstract

The shelterbelts system is crucial for the regional surface water and heat process, which is important for the oasis ecological environment. In this study, Ulan Buh Desert Oasis was taken as the study area. To overcome the problem of inherent water and heat difference between oases and deserts, this study divided the oasis ring structure into shelterbelt-farmland-urban zone, shrub grassland zone and desert zone. Firstly, the instant latent heat flux (LE), regarded as the link between water and heat, was estimated by the Two-Source Energy Balance (TSEB) model. Then, four landscape indexes were applied to quantify the shelterbelts spatial pattern. Finally, the Cooling Capacity Index (CCI) was proposed, and the influence of spatial pattern and shelterbelt structure on LE and CCI was explored. The results showed that, the high-LE area distribution was highly consistent with the shelterbelt system, and the LE temporal variation inside the oasis was more stable than outside. Besides, the 5 km shrub grassland combined with more than the 5 km shelterbelt near the desert area can bring about a rapid increase in the LE and generate cooling capacity. Meanwhile, in shelterbelt-farmland-urban zone, the LE was negatively correlated with patch shape regularity (SHAPE) and shelterbelt area (PLAND), and was positively correlated with the shape of the whole shelterbelt landscape (nLSI). In shrub grassland zone, the LE was negatively correlated with SHAPE and shelterbelts patches connectance (CONNECT), and was positively correlated with nLSI and PLAND. In desert zone, LE was only positively correlated with PLAND. To achieve more cooling effects, it is recommended that i) in shelterbelt-farmland-urban zone, use multi-row shelterbelt that the patches are with large area and complex shape consists of multiple belts and multiple networks (high PLAND and SHAPE), and densely clustered shelterbelt patches (low nLSI); ii) in shrub grassland zone, use the same spatial pattern as in shelterbelt-farmland-urban zone (low nLSI, high PLAND and high SHAPE), but replaced with the two-row shelterbelt; iii) in desert zone, use a large area of the two-row shelterbelt.