Continual land degradation processes adversely affect the functioning of dryland ecosystems. In recent decades, extensive afforestation activities have been undertaken in marginal lands of the semiarid northern Negev region of southern Israel to mitigate such degradation processes. However, the long-term impacts of these actions in drylands, subjected to long-term drought episodes, remain unknown. We investigated the impact of landuse change from natural lands to afforestation runoff-harvesting systems—through intensive earthworks (landforming) to establish a contour bench terrace during long-term drought—on herbaceous vegetation productivity, and assessed its temporal dynamics across the multi-aged Ambassadors’ Forest. The MODIS MOD13Q1 and MYD13Q1 maximum value composite products were used to calculate normalized difference vegetation index (NDVI) data for the hydrological years 2000 to 2020. For this study, implemented in 2021, we selected three locations within the Ambassadors’ Forest: (1) 15-year-old afforested hillslopes, (2) 11-year-old afforested hillslopes, and (3) 4-year-old afforested hillslopes. We further delineated undisturbed hillslopes near these sites as a reference treatment. We found high spatiotemporal variability in vegetation cover. Over the short term, and specifically in the first hydrological year following the establishment of the water-harvesting systems, a substantial reduction in mean annual NDVI was observed, with values ranging from 30% to 65% lower compared to the reference sites. However, the negative impact of landuse change diminished over time, suggesting that (1) self-restoration processes occurred over a longer term after landuse changes were implemented, and (2) the establishment of water-harvesting systems improve the conservation of runoff water at the hillslope. This effect was observed for the 11- and 15-year-old afforestation sites, where vegetation productivity was 8.9% and 31.0% greater, respectively, than in the respective reference sites ( p < 0.05). Although the long-term drought occurred during the construction of the water-harvesting systems, these findings are in agreement with previous studies. Specifically, this study suggests that ecological self-restoration processes in semiarid regions occur approximately a decade after runoff-harvesting systems are established through earthworks.

中文翻译：

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多龄旱地造林系统的生态水文功能

持续的土地退化过程对旱地生态系统的功能产生不利影响。近几十年来，以色列南部内盖夫北部半干旱地区的边缘土地开展了广泛的植树造林活动，以减缓这种退化过程。然而，这些行动对遭受长期干旱的旱地的长期影响仍然未知。我们调查了从自然土地到造林径流收集系统的土地利用变化——通过密集的土方工程（土地整治）在长期干旱期间建立等高台地——对草本植被生产力的影响，并评估了其在多年龄阶段的时间动态。大使森林。MODIS MOD13Q1 和 MYD13Q1 最大值复合产品用于计算 2000 年至 2020 年水文年的归一化植被指数 (NDVI) 数据。对于这项于 2021 年实施的研究，我们选择了大使森林内的三个地点：(1) 15 年的绿化山坡，(2) 11 年的绿化山坡，以及 (3) 4 年的绿化山坡。我们进一步划定了这些地点附近未受干扰的山坡作为参考处理。我们发现植被覆盖具有很高的时空变异性。在短期内，特别是在集水系统建立后的第一个水文年，观察到年平均 NDVI 大幅下降，与参考地点相比，值降低了 30% 至 65%。然而，土地利用变化的负面影响随着时间的推移而减弱，这表明：（1）土地利用变化实施后，自我恢复过程会在较长时期内发生；（2）集水系统的建立改善了径流水的保存。山坡。在 11 年和 15 年造林地点观察到了这种效应，其中植被生产力分别比各自参考地点高 8.9% 和 31.0% (p < 0.05)。尽管在集水系统建设期间发生了长期干旱，但这些发现与之前的研究结果一致。具体来说，这项研究表明，半干旱地区的生态自我恢复过程发生在通过土方工程建立径流收集系统大约十年后。