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Precipitation is a key driver of litter decomposition in arid/semiarid regions; where soils are poor in organic matter, and thus re-incorporation of litter is key for soil nutrient accumulation and soil structure. It remains unclear, though, whether litter decomposition responds symmetrically to precipitation variation (e.g., if precipitation surpluses produce a stimulatory effect of a similar magnitude, but opposite direction to inhibitory effects of precipitation deficits), and whether litter decomposition and litter nutrient dynamics in arid and semiarid ecosystems that differ in climate show similar responses to precipitation. We set up a 5-and-a-half-year experiment that manipulated rainfall along a gradient (7 treatments): increases by 20%, 40%, and 60%, background precipitation, and reductions by the same 3 percentages. We applied such experiment in two sites with different pattens of precipitation (Urat: arid; and Naiman: semiarid) in Inner Mongolia to elucidate our questions. Litter mass loss and all nutrients that we measured (carbon, nitrogen, phosphorous, potassium, plus lignin) decomposed faster at the highest level of surplus precipitation, and more slowly in the two largest precipitation reductions. This indicates that these levels of precipitation constitute thresholds (value of precipitation beyond which ecosystem function is critically altered). Litter decomposition in the semiarid site was faster and more complete, but decomposition in the direr Urat was more efficient per unit cumulative rainfall. Thus, site specific effects played an important role in decomposition. Reductions in precipitation decreased the loss of C, N, P, K, and lignin from litter; and clear precipitation thresholds in the dynamic of these nutrients in litter were observed. Overall, this indicated the importance of precipitation limitation at controlling nutrient release. Our study highlights the importance of long-term studies on litter decomposition in environments with slow decomposition rates, and the importance of taking into account mechanistic effects of water availability on decomposition. [ABSTRACT FROM AUTHOR]

As a large-scale irrigation and water conservancy project in ancient times, karez are common in Central Asia and arid regions with a history of thousands of years. Turpan, which is located in the Xinjiang Uyghur Autonomous Region, has the most extensive and concentrated distribution of karez shafts in China. There are tens of thousands of shafts, some of which are in use and are living cultural heritage. According to radiocarbon (14C) dating, some karezs are over 600 years old. The karez is of great significance to the research on geology, hydrology, oasis, climate change, and development history of karez in Turpan. With the development of the population, arable land, industrialization, and urbanization, karez systems are facing the risk of abandonment. Detailed karez distribution mapping or dynamic monitoring data are important for their management or analysis; although there are related methods, due to Turpan's large desert and "Gobi" environments, field surveys are time- and energy-consuming, and some areas are difficult to access. Precise shaft locations and distribution maps are scarce and often lack georeferencing. The distribution and preservation of karez have not yet been fully grasped. In this study, we evaluated the effectiveness of You Only Look Once version 5 (YOLOv5) in automatically detecting karez in high-resolution images of the Turpan region. We propose post-processing steps to reduce the false karez identified by YOLOv5. Our results demonstrate the feasibility of using YOLOv5 and post-processing techniques to detect karez automatically, and the detected results are sufficient to capture the linear alignment of karez. Target detection based on YOLOv5 and post-processing can greatly improve automatic shaft identification and is therefore useful for the fine mapping of karez. We also applied this method in Shanshan County (for which no detailed mapping data on karez has been obtained before) and successfully detected some karez that had not been archived before. The number of shafts in Turpan is 82,493. Through DBSCAN clustering, it was identified which karez line belonged to which shaft; the number of sections of karez that have been used is 5057, which have a total length of 2387.2 km. The karez line obtained was overlaid with the crop-land data, and the positional relationship between the karez line and the crop land was analyzed. The cultivated area is basically surrounded by karez. Our method can potentially be applied to construct an inventory for all karez shafts globally. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "A 5-and a-half-year-experiment shows precipitation thresholds in litter decomposition and nutrient dynamics in arid and semi-arid regions." The original article was published online on November 27, 2023, with Open Access under a Creative Commons Attribution 4.0 International License. However, the authors later decided to cancel Open Access, and the copyright of the article changed on December 7, 2023, to © The Author(s), under exclusive license to Springer-Verlag GmbH Germany, part of Springer Nature 2023 with all rights reserved. The publisher, Springer Nature, remains neutral regarding jurisdictional claims and institutional affiliations. The authors of the article are Hao Qu, Eduardo Medina-Roldán, Shaokun Wang, Xujun Ma, Xinyuan Wang, Xia Tang, and Liangxu Liu. [Extracted from the article]

Empirical verification of multiple states in drylands is scarce, impeding the design of indicators to anticipate the onset of desertification. Remote sensing‐derived indicators of ecosystem states are gaining new ground due to the possibilities they bring to be applied inexpensively over large areas. Remotely sensed albedo has been often used to monitor drylands due to its close relationship with ecosystem status and climate. Here, we used a space‐for‐time‐substitution approach to evaluate whether albedo (averaged from 2000 to 2016) can identify multiple ecosystem states in African drylands spanning from the Saharan desert to tropical Africa. By using latent class analysis, we found that albedo showed two states (low and high; the cut‐off level was 0.22 at the shortwave band). Potential analysis revealed that albedo exhibited an abrupt and discontinuous increase with increased aridity (1 − [precipitation/potential evapotranspiration]). The two albedo states co‐occurred along aridity values ranging from 0.72 to 0.78, during which vegetation cover exhibited a rapid, continuous decrease from ~90% to ~50%. At aridity values of 0.75, the low albedo state started to exhibit less attraction than the high albedo state. Low albedo areas beyond this aridity value were considered as vulnerable regions where abrupt shifts in albedo may occur if aridity increases, as forecasted by current climate change models. Our findings indicate that remotely sensed albedo can identify two ecosystem states in African drylands. They support the suitability of albedo indices to inform us about discontinuous responses to aridity experienced by drylands, which can be linked to the onset of land degradation. [ABSTRACT FROM AUTHOR]

• Burial depths but not species identity, had significant effect on litter mass loss. • The effects of depth depended on the time of decomposition. • Abiotic factors limiting litter mass loss switch with burial depths. Litter decomposition is an important ecosystem process and a key determinant of nutrient turnover and carbon cycling in arid and semiarid regions. Sand burial is common in arid and semiarid regions and may strongly influence litter decomposition. However, the main factors influencing litter decomposition under sand burial conditions are uncertain. We performed a litter bag experiment over 3 years to understand the effects of sand burial on litter mass loss and measured abiotic factors (light intensity, soil temperature and humidity) and initial litter traits to determine which factors most influenced litter mass losses. The leaf litters of three dominant shrubs (Artemisia halodendron , Caragana microphylla , and Salix gordejevii) in the Horqin Sandy Land of northern China were selected, and four burial depths (surface, 5 cm, 10 cm, and 20 cm) were used. The results showed that the litter from the three shrubs under the surface treatment (no burial) and at the 5 cm burial depth decomposed more rapidly than the litter that was buried at depths of 10 cm and 20 cm. This is explained because the abiotic factors on the surface and at 5 cm burial depth were conducive for the mass loss of litter. The differences in litter mass losses among the three shrubs were not significant under other burial treatments, except that A. halodendron 's litter decomposed significantly faster than litter from the other two shrubs at depths of 10 cm. Species differences in litter traits were weaker than the effects of burial depths and retrieval times on litter mass loss. The stepwise regression analysis showed that light intensity and soil temperature were the most important factors influencing the mean litter mass loss of 3 years. Therefore, we concluded that relative to the initial litter traits, abiotic factors are more able to indicate the leaf litter mass loss under sand burial conditions, and abiotic factors limiting litter mass loss switch with burial depths. [ABSTRACT FROM AUTHOR]