28 results on '"Aridity index"'
Search Results
2. Cyanobacterial and moss biocrusts shape soil nematode community in dryland mountain ecosystems with increasing aridity.
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Wang, Yanfeng, Xiao, Bo, Wang, Wanfu, Saéz-Sandino, Tadeo, and Delgado-Baquerizo, Manuel
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- 2024
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3. Climate-dependent responses of root and shoot biomass to drought duration and intensity in grasslands–a meta-analysis.
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Guasconi, Daniela, Manzoni, Stefano, and Hugelius, Gustaf
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- 2023
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4. Response of streamflow to environmental changes: A Budyko-type analysis based on 144 river basins over China.
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Li, Yanzhong, Liu, Changming, Yu, Wenjun, Tian, Di, and Bai, Peng
- Abstract
Abstract Understanding response of streamflow to environmental changes is crucial for large-scale water resources management and ecosystem restoration. There is no consensus on how environmental change influence streamflow in different regions across climate gradient, as previous studies mainly focused on a single river basin or climate region. This study analyzed the variations of aridity index and its contributions to streamflow change based on Budyko's framework approach using bias-corrected precipitation measurement, parameters-optimized potential evapotranspiration and observed streamflow in 144 basins across China. The parameter n in the Budyko type equation exhibits significant spatial heterogeneity, with larger values in the water-limited region than in the energy-limited region, which suggests more pronounced impact of basin characteristic or vegetation change on hydrological cycle. The absolute value of sensitivity coefficient in the water-limited region (−2.56) was larger than both equitant (−2.13) and energy limited region (−1.57), indicating that the streamflow was more sensitive to aridity index change in the water-limited region than in the equitant and energy-limited regions. The dominant factor affecting streamflow under energy-limited and equitant conditions is aridity index (i.e. climate change), with median relative contribution rates of 79.9% and 55.5%, respectively. In contrast, non-climatic factors dominate the variation of streamflow in the water-limited region, the effect of climate change on streamflow has been offset by other factors. This study suggests that the water management practices, such as water diversion across river basins and ecological restorations, should fully consider the differences in hydrological responses to climatic conditions. Graphical abstract Unlabelled Image Highlights • Bias correction to precipitation and optimization to a s and b s are essential for aridity index application • Streamflow is more sensitive to climate change in water-limited region than that in equitant and energy-limited region • Streamflow is dominated by climate in energy-limited and equitant regions and by other factors in water-limited region [ABSTRACT FROM AUTHOR]
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- 2019
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5. Evaluating the responses of net primary productivity and carbon use efficiency of global grassland to climate variability along an aridity gradient.
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Liu, Yangyang, Yang, Yue, Wang, Qian, Du, Xiaolong, Li, Jianlong, Gang, Chengcheng, Zhou, Wei, and Wang, Zhaoqi
- Abstract
Abstract Net primary productivity (NPP) and carbon use efficiency (CUE) are common ecological indicators for assessing the terrestrial carbon cycle. However, despite their widespread use, considerable uncertainties exist toward the response patterns of NPP and CUE to climate variability along an aridity gradient, especially for grassland ecosystems. The aridity index (AI) was calculated in this study to specify arid-humid zones across the global grassland ecosystem. The dynamics of grassland NPP, CUE, and their dependence on climate under different AI levels from 2000 to 2013 were investigated. Results showed that the NPP and CUE of grasslands demonstrated a slightly increasing trend with regional increasing precipitation in most AI zones, except for arid regions (AR) from 2000 to 2013. The NPP and CUE of grasslands exhibited a remarkable spatial heterogeneity in different AI zones. High NPP values mainly occurred in the dry and sub-humid (DSH) and humid (HU) regions of Southern Hemisphere with warm and wet climate. High CUE values were mostly found in the HU of the Northern Hemisphere with cold and wet climate. In addition, low NPP and CUE values were observed in most parts of AR and semi-AR (SAR) with hot and dry climate. Overall, the NPP and CUE of grasslands were significantly affected by precipitation at the global scale. Specifically, grassland NPP was positively correlated with the mean annual precipitation (MAP) in SAR and AR, but negatively related with the MAP in the HU region. The positive correlation between NPP and mean annual temperature (MAT) was found only for HU regions. Grassland CUE indicated a positive relation with MAP, but a negative relation was observed with MAT in all AI zones. The correlation coefficients between CUE and MAP decreased from AR to HU regions. This finding indicated that grassland CUE was highly sensitive to precipitation in dry areas, but this relationship weakened in HU ecosystems. Graphical abstract Unlabelled Image Highlights • Evaluating the responses of grassland NPP and CUE to climate variability along an aridity gradient is very significant. • The terrestrial aridity-humid zones can be specified by calculating the aridity index (AI). • The impacts of climate variability on grassland NPP and CUE varied greatly along the arid gradient. • Grassland CUE was more sensitive to precipitation in dry areas, but this relationship became weak in humid ecosystems. [ABSTRACT FROM AUTHOR]
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- 2019
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6. Environmental factors regulate soil microbial attributes and their response to drought in rangeland ecosystems.
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Toledo, Santiago, Bondaruk, Viviana F., Yahdjian, Laura, Oñatibia, Gastón R., Loydi, Alejandro, Alberti, Juan, Bruschetti, Martín, Pascual, Jesús, Peter, Guadalupe, Agüero, Walter D., Namur, Pedro R., Blanco, Lisandro, and Peri, Pablo L.
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- 2023
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7. Divergent sensitivity of vegetation to aridity between drylands and humid regions.
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Zhang, Guolong, He, Yongli, Huang, Jianping, Fu, Li, Han, Dongliang, Guan, Xiaodan, and Zhang, Beidou
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- 2023
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8. Climate-driven sapwood-specific hydraulic conductivity and the Huber value but not leaf-specific hydraulic conductivity on a global scale.
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Zhu, Li-Wei and Zhao, Ping
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- 2023
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9. Comparison of the climate indices based on the relationship between yield loss of rain-fed winter wheat and changes of climate indices using GEE model
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Ali Shabani, Abdol Rassoul Zarei, and Mohammad Reza Mahmoudi
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Time Factors ,Environmental Engineering ,Index (economics) ,010504 meteorology & atmospheric sciences ,Climate ,Climate Change ,Rain ,Yield (finance) ,Winter wheat ,Climate change ,Iran ,010501 environmental sciences ,01 natural sciences ,Gee ,Environmental Chemistry ,Aridity index ,Waste Management and Disposal ,Triticum ,0105 earth and related environmental sciences ,Annual percentage yield ,Flood myth ,Models, Theoretical ,Pollution ,Climatology ,Environmental science ,Seasons - Abstract
Climate change is one of the most important meteorological phenomena that has had a lot of impacts on different sections with different spatial scales. In recent decades, climate changes affected by various factors especially human activities have had various impacts in different sections such as melting glaciers, various flood occurrence, occurrence of different droughts and etc. UNEP aridity Index (UNEP) and Modified De-Martonne index (MDM) are two more used indices to evaluate climate conditions in various regions of the world. In this paper; 1) the temporal trend of changes in climate conditions based on UNEP and MDM indices using climatological data (from 1967 to 2017) of 16 meteorological stations using parametric and non-parametric statistical tests were evaluated 2) the accuracy of UNEP and MDM indices were compared to assess climate conditions, based on the correlation between mentioned indices and percent of annual yield loss (AYL) in rain-fed winter wheat using simple and multiple Generalizes Estimation Equation (GEE) methods (for help managers to select more suitable and more accurate index to assess climate condition). Results showed, based on UNEP and MDM indices, climate indices in 93.75% and 87.5% of stations had a decreasing trend, but decreasing trend only in 56.25% and 50% of stations were significant at 5% level (respectively). The evaluation of the accuracy of UNEP and MDM indices showed that, in all stations, |B| coefficients between calculated AYL and UNEP and MDM indices and R2 coefficients between simulated AYL using AquaCrop model and predicted AYL using simple and multiple GEE methods in UNEP aridity index were more than MDM index. So, it is recommended to use UNEP aridity index to assess the climate conditions in different regions.
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- 2019
10. Evaluating the responses of net primary productivity and carbon use efficiency of global grassland to climate variability along an aridity gradient
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Yue Yang, Jianlong Li, Zhaoqi Wang, Yangyang Liu, Xiaolong Du, Chengcheng Gang, Wei Zhou, and Qian Wang
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geography ,Environmental Engineering ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Primary production ,010501 environmental sciences ,01 natural sciences ,Pollution ,Arid ,Grassland ,Carbon cycle ,Spatial heterogeneity ,Environmental Chemistry ,Environmental science ,Aridity index ,Ecosystem ,Physical geography ,Precipitation ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
Net primary productivity (NPP) and carbon use efficiency (CUE) are common ecological indicators for assessing the terrestrial carbon cycle. However, despite their widespread use, considerable uncertainties exist toward the response patterns of NPP and CUE to climate variability along an aridity gradient, especially for grassland ecosystems. The aridity index (AI) was calculated in this study to specify arid-humid zones across the global grassland ecosystem. The dynamics of grassland NPP, CUE, and their dependence on climate under different AI levels from 2000 to 2013 were investigated. Results showed that the NPP and CUE of grasslands demonstrated a slightly increasing trend with regional increasing precipitation in most AI zones, except for arid regions (AR) from 2000 to 2013. The NPP and CUE of grasslands exhibited a remarkable spatial heterogeneity in different AI zones. High NPP values mainly occurred in the dry and sub-humid (DSH) and humid (HU) regions of Southern Hemisphere with warm and wet climate. High CUE values were mostly found in the HU of the Northern Hemisphere with cold and wet climate. In addition, low NPP and CUE values were observed in most parts of AR and semi-AR (SAR) with hot and dry climate. Overall, the NPP and CUE of grasslands were significantly affected by precipitation at the global scale. Specifically, grassland NPP was positively correlated with the mean annual precipitation (MAP) in SAR and AR, but negatively related with the MAP in the HU region. The positive correlation between NPP and mean annual temperature (MAT) was found only for HU regions. Grassland CUE indicated a positive relation with MAP, but a negative relation was observed with MAT in all AI zones. The correlation coefficients between CUE and MAP decreased from AR to HU regions. This finding indicated that grassland CUE was highly sensitive to precipitation in dry areas, but this relationship weakened in HU ecosystems.
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- 2019
11. Climate change induced declines in fuel moisture may turn currently fire-free Pyrenean mountain forests into fire-prone ecosystems
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Rubén Díaz-Sierra, Edurne Martínez del Castillo, Àngel Cunill Camprubí, Matthias M. Boer, Víctor Resco de Dios, Javier Hedo, José Antonio Bonet, Juan Martínez de Aragón, Rodrigo Balaguer-Romano, Prakash Thapa, and Marta Yebra
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Mediterranean climate ,Environmental Engineering ,Moisture ,Vapour Pressure Deficit ,Climate Change ,Climate change ,Forests ,Pollution ,Arid ,Fires ,Wildfires ,Effects of global warming ,Environmental Chemistry ,Environmental science ,Aridity index ,Precipitation ,Physical geography ,Waste Management and Disposal ,Ecosystem - Abstract
Fuel moisture limits the availability of fuel to wildfires in many forest areas worldwide, but the effects of climate change on moisture constraints remain largely unknown. Here we addressed how climate affects fuel moisture in pine stands from Catalonia, NE Spain, and the potential effects of increasing climate aridity on burned area in the Pyrenees, a mesic mountainous area where fire is currently rare. We first quantified variation in fuel moisture in six sites distributed across an altitudinal gradient where the long-term mean annual temperature and precipitation vary by 6-15 °C and 395-933 mm, respectively. We observed significant spatial variation in live (78-162%) and dead (10-15%) fuel moisture across sites. The pattern of variation was negatively linked (r = |0.6|-|0.9|) to increases in vapor pressure deficit (VPD) and in the Aridity Index. Using seasonal fire records over 2006-2020, we observed that summer burned area in the Mediterranean forests of Northeast Spain and Southern France was strongly dependent on VPD (r = 0.93), the major driver (and predictor) of dead fuel moisture content (DFMC) at our sites. Based on the difference between VPD thresholds associated with large wildfire seasons in the Mediterranean (3.6 kPa) and the maximum VPD observed in surrounding Pyrenean mountains (3.1 kPa), we quantified the "safety margin" for Pyrenean forests (difference between actual VPD and that associated with large wildfires) at 0.5 kPa. The effects of live fuel moisture content (LFMC) on burned area were not significant under current conditions, a situation that may change with projected increases in climate aridity. Overall, our results indicate that DFMC in currently fire-free areas in Europe, like the Pyrenees, with vast amounts of fuel in many forest stands, may reach critical dryness thresholds beyond the safety margin and experience large wildfires after only mild increases in VPD, although LFMC can modulate the response.
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- 2021
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12. Complex effects of moisture conditions and temperature enhanced vegetation growth in the Arid/humid transition zone in Northern China
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Danyang Ma, Yunhe Yin, and Haoyu Deng
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China ,Environmental Engineering ,Climate Change ,Temperature ,Growing season ,Climate change ,Vegetation ,Pollution ,Arid ,Humans ,Environmental Chemistry ,Environmental science ,Human Activities ,Ecosystem ,Aridity index ,Physical geography ,Precipitation ,Leaf area index ,Waste Management and Disposal - Abstract
Ecosystems in the arid/humid transition zone (AHTZ) of northern China are highly sensitive to climate change and human activities. Accurately assessing the impact of climate change on these ecosystems is important for effectively reducing the risks faced by them under future climate change. In this study, the leaf area index during the selected growing season (LAIGS) was used as an indicator for vegetation activity. After comparison different potential indicators, the growing season temperature (TGS) was used to indicate temperature, and the growing season aridity index (AIGS), which considers the regional water budget, was used to indicate moisture rather than precipitation, which is used more commonly. Correlation analysis and residual trends were used to study the influence of climatic and non-climatic factors on vegetation activity in the AHTZ from 1982 to 2016. The results for regions where LAIGS increased significantly (0.037/10 yr, 53.58% of the study area), the regions where LAIGS dominated by non-climatic factors (18.40%) was larger than areas dominated by climatic factors (9.61%). However, most (25.57%) of the regions in the selected study area were mainly driven by both climatic and non-climatic factors. In about half (49.73%) of the climate-affected regions, significant changes in LAIGS were driven jointly by TGS and AIGS. These regions were mainly in the northern and western Loess Plateau. The regions where changes were driven mainly by AIGS, and those where changes were driven mainly by TGS, each accounted for nearly a quarter of climate-affected regions (24.87% and 25.40%, respectively). The former regions were on the western Songliao Plain, the northern North China Plain, and the northern Loess Plateau, and the latter regions were in the northern Greater Khingan Mountains, on the southern North China Plain, in the western mountains of North China, and on the southern Loess Plateau.
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- 2022
13. Latitudinal patterns of leaf N, P stoichiometry and nutrient resorption of Metasequoia glyptostroboides along the eastern coastline of China
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Tonggui Wu, G. Geoff Wang, Mukui Yu, Hui Zhang, and Weihong Guo
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0106 biological sciences ,China ,Environmental Engineering ,Nitrogen ,chemistry.chemical_element ,Biology ,010603 evolutionary biology ,01 natural sciences ,Latitude ,Soil ,Nutrient ,Botany ,Environmental Chemistry ,Aridity index ,Waste Management and Disposal ,Cupressaceae ,Phosphorus ,biology.organism_classification ,Pollution ,Metasequoia glyptostroboides ,Resorption ,Plant Leaves ,chemistry ,Agronomy ,Longitude ,Stoichiometry ,010606 plant biology & botany - Abstract
Latitudinal patterns of leaf stoichiometry and nutrient resorption were not consistent among published studies, likely due to confounding effects from taxonomy (e.g., plant distribution and community composition), and environment, which is also influenced by altitude and longitude. Thus, the latitudinal patterns and environmental mechanism could be best revealed by testing a given species along a latitude gradient with similar altitude and longitude. We determined nitrogen (N) and phosphorus (P) concentrations of green (leaf) and senesced leaves (litter) from eight Metasequoia glyptostroboides forests along the eastern coastline of China, with similar altitude and longitude. Leaf N, P concentrations increased along latitude, mainly driven by mean annual temperature (MAT), mean annual precipitation (MAP), annual evaporation (AE), aridity index (AI), and annual total solar radiation (ATSR); While leaf N:P ratio was stable with no latitudinal pattern. Nitrogen resorption efficiency (NRE) increased along latitude, and was also mainly influenced by MAT, MAP, AE, and AI. Phosphorus resorption efficiency (PRE) first increased and then decreased with latitude, which was impacted by soil available P. These results indicated that only climate (such as heat, water, and light) controlled the shift in leaf stoichiometry and NRE, while soil nutrient was likely responsible for the shift in PRE along eastern China. Our findings also suggested that leaf N, P stoichiometry and NRE displayed similar latitudinal patterns at regional scale when studied for a given species (this study) or multi-species (previous studies).
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- 2018
14. The new Green Revolution: Sustainable intensification of agriculture by intercropping
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Alain Paquette, David Rivest, Jérôme Dupras, and Marc-Olivier Martin-Guay
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0106 biological sciences ,Irrigation ,Environmental Engineering ,Population ,01 natural sciences ,Agricultural economics ,Economics ,Environmental Chemistry ,Production (economics) ,Aridity index ,education ,Waste Management and Disposal ,2. Zero hunger ,education.field_of_study ,biology ,business.industry ,Agroforestry ,Intercropping ,04 agricultural and veterinary sciences ,15. Life on land ,biology.organism_classification ,Pollution ,13. Climate action ,Agriculture ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Monoculture ,business ,Green Revolution ,010606 plant biology & botany - Abstract
Satisfying the nutritional needs of a growing population whilst limiting environmental repercussions will require sustainable intensification of agriculture. We argue that intercropping, which is the simultaneous production of multiple crops on the same area of land, could play an essential role in this intensification. We carried out the first global meta-analysis on the multifaceted benefits of intercropping. The objective of this study was to determine the benefits of intercropping in terms of energetic, economic and land-sparing potential through the framework of the stress-gradient hypothesis. We expected more intercropping benefits under stressful abiotic conditions. From 126 studies that were retrieved from the scientific literature, 939 intercropping observations were considered. When compared to the same area of land that was managed in monoculture, intercrops produced 38% more gross energy (mean relative land output of 1.38) and 33% more gross incomes (mean relative land output of 1.33) on average, whilst using 23% less land (mean land equivalent ratio of 1.30). Irrigation and the aridity index in non-irrigated intercrops did not affect land equivalent ratio, thereby indicating that intercropping remains beneficial, both under stressful and non-stressful contexts concerning moisture availability. Fertilisation and intercropping patterns (rows and strips vs. mixed) did not affect land equivalent ratio. Although intercropping offers a great opportunity for intensification of existing agricultural lands, many challenges need to be tackled by experts from multiple disciplines to ensure its feasible implementation.
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- 2018
15. Determining and forecasting drought susceptibility in southwestern Iran using multi-criteria decision-making (MCDM) coupled with CA-Markov model
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Marzieh Mokarram, Ming Hu, Hamid Reza Pourghasemi, and Huichun Zhang
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Hydrology ,Environmental Engineering ,Soil salinity ,010504 meteorology & atmospheric sciences ,Soil texture ,010501 environmental sciences ,01 natural sciences ,Pollution ,Arid ,Altitude ,Evapotranspiration ,Erosion ,Environmental Chemistry ,Environmental science ,Aridity index ,Precipitation ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
Forecasting drought and determining relevant data to predict drought are an important topic for decision-makers and planners. It is critical to predicting drought in the south of Fars province, an important agricultural center in Iran located in arid and semi-arid climates. The purpose of this study was to generate a drought map in 2019 using 12 parameters: altitude, aridity index, erosion, groundwater depth, land use, PET (Potential evapotranspiration), precipitation days, precipitation, slope, soil texture, soil salinity, and distance to river, and predict drought maps in 2030 and 2040 using the cellular automata (CA)-Markov model spatially. The fuzzy method was first used to homogenize the data. Next, by evaluating each parameter, the weight of each parameter was calculated using the analytic hierarchy process (AHP), and a map of drought-prone areas was generated. The results of the fuzzy-AHP method showed that the eastern and southeastern regions of the study area were prone to drought. The four most predictive parameters in causing drought, i.e., aridity index, PET, precipitation, and soil texture, were selected using the Best search method and were then chosen as the input to determine drought mapping using the fuzzy and AHP methods. Finally, the CA-Markov model was used to predict future drought maps, and the results showed that in 2030 and 2040 the drought situation in the east and south of the study area would intensify.
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- 2021
16. Water use efficiency in terrestrial ecosystem over East Asia: Effects of climate regimes and land cover types
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Daeun Kim, Muhammad Umair, Jongjin Baik, and Minha Choi
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geography ,Environmental Engineering ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Wetland ,Land cover ,Vegetation ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,Pollution ,Water resources ,Evapotranspiration ,Environmental Chemistry ,Environmental science ,Terrestrial ecosystem ,Aridity index ,Water-use efficiency ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
Water use efficiency (WUE) is an environmental factor to account for the metabolism of terrestrial ecosystems using various climate systems and vegetation types. It is estimated by the ratio of gross primary productivity (GPP) to evapotranspiration (ET), the largest carbon and water fluxes with respect to plant respiration. In this study, the WUE was calculated using GPP and ET from the community land model version 4.0 (CLM4.0), inclusive of the prognostic carbon-nitrogen model in the community earth system model (CESM). The estimated WUE in East Asia was analyzed for climate zones, land cover types, and water- and energy-limited zones, with aridity index (AI). Spatial variations from 2001 to 2015 in annual WUE gradually increased as latitude decreased, though small year-to-year differences appeared between monthly GPP and ET. Monthly WUE was lower in summer than fall because the water loss rate in summer was higher than the carbon assimilation increase. The WUE under arid conditions (AI
- Published
- 2021
17. Complex effects of moisture conditions and temperature enhanced vegetation growth in the Arid/humid transition zone in Northern China.
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Yin, Yunhe, Deng, Haoyu, and Ma, Danyang
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- 2022
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18. Alternative biome states of African terrestrial vegetation and the potential drivers: A continental-scale study.
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Cheng, Linhai, Lu, Nan, Wang, Mengyu, Fu, Bojie, and Xu, Zhihong
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- 2021
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19. Time-scale dependent mechanism of atmospheric CO2 concentration drivers of watershed water-energy balance
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Qiang Huang, Shengzhi Huang, Guoyong Leng, Hao Wang, Jing Zhao, and Baozhu Pan
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Carbon dioxide in Earth's atmosphere ,geography ,Environmental Engineering ,Watershed ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Drainage basin ,Climate change ,Context (language use) ,Vegetation ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,Pollution ,Environmental Chemistry ,Environmental science ,Aridity index ,Hydrometeorology ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
The elevated atmospheric carbon dioxide concentration (CO2), as a key variable linking human activities and climate change, seriously affects the watershed hydrological processes. However, whether and how atmospheric CO2 influences the watershed water-energy balance dynamics at multiple time scales have not been revealed. Based on long-term hydrometeorological data, the variation of non-stationary parameter n series in the Choudhury's equation in the mainstream of the Wei River Basin (WRB), the Jing River Basin (JRB) and Beiluo River Basin (BLRB), three typical Loess Plateau regions in China, was examined. Subsequently, the Empirical Mode Decomposition method was applied to explore the impact of CO2 on watershed water-energy balance dynamics at multiple time scales. Results indicate that (1) in the context of warming and drying condition, annual n series in the WRB displays a significantly increasing trend, while that in the JRB and BLRB presents non-significantly decreasing trends; (2) the non-stationary n series was divided into 3-, 7-, 18-, exceeding 18-year time scale oscillations and a trend residual. In the WRB and BLRB, the overall variation of n was dominated by the residual, whereas in the JRB it was dominated by the 7-year time scale oscillation; (3) the relationship between CO2 concentration and n series was significant in the WRB except for 3-year time scale. In the JRB, CO2 concentration and n series were significantly correlated on the 7- and exceeding 7-year time scales, while in the BLRB, such a significant relationship existed only on the 18- and exceeding 18-year time scales. (4) CO2-driven temperature rise and vegetation greening elevated the aridity index and evaporation ratio, thus impacting watershed water-energy balance dynamics. This study provided a deeper explanation for the possible impact of CO2 concentration on the watershed hydrological processes.
- Published
- 2021
20. Climate controls on the terrestrial water balance: Influence of aridity on the basin characteristics parameter in the Budyko framework
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Subimal Ghosh, Anamitra Saha, and Jisha Joseph
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geography ,Environmental Engineering ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Global warming ,Drainage basin ,Climate change ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,Pollution ,Water balance ,Evapotranspiration ,Environmental Chemistry ,Environmental science ,Aridity index ,Hydrometeorology ,Water cycle ,Waste Management and Disposal ,0105 earth and related environmental sciences - Abstract
The terrestrial water balance can be represented by the ratio of evapotranspiration to precipitation, which is expressed as a function of the aridity index (ϕ) and the basin characteristics parameter (n) in the Budyko framework. Traditionally n is assumed to be a constant for a catchment, independent to the climatic variables and altered only by changes in land cover and human activities. Another conceptual framework, Climate Change Impact Hypotheses (CCUW), makes similar assumption of constant catchment efficiency for evapotranspiration. In this study, using Variation Infiltration Capacity (VIC) model experiments, we show that the basin characteristics parameter and catchment efficiency are influenced by aridity index, in contrast with the traditional assumption. We also examine the analytical derivation of a functional form of Budyko equation and show that the assumption of n being independent of the climate variables is not valid. Hydrologic simulations with VIC show that the influence of seasonal change in vegetation (in the form of Leaf Area Index) on n is negligible compared to that of aridity, but the intra-seasonal rainfall variability does have impacts. We demonstrate these with a case study on impact of 1.5 °C and 2 °C global warming scenarios on the terrestrial water cycle in the Ganga river basin, one of the large river basins of South Asia with multiple sub-basins. Our findings imply that, with these assumptions, classical conceptual frameworks cannot fully explain the hydrometeorological impacts of climate change. These results highlight the importance of model evaluation and assessment of model assumptions before regional impact assessment studies.
- Published
- 2020
21. Habitat-specific environmental factors regulate spatial variability of soil bacterial communities in biocrusts across northern China's drylands
- Author
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Yan-gui Su, Bing-chang Zhang, Jie Liu, Hong-mei Zhao, and Gang Huang
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China ,Environmental Engineering ,complex mixtures ,Grassland ,Soil ,parasitic diseases ,Environmental Chemistry ,natural sciences ,Aridity index ,Ecosystem ,Waste Management and Disposal ,Phylogeny ,Soil Microbiology ,Biotic component ,geography.geographical_feature_category ,Ecology ,fungi ,Pollution ,Arid ,Phylogenetic diversity ,Geography ,Habitat ,Spatial variability ,Desert Climate ,geographic locations - Abstract
Biocrusts are common biotic components in dryland ecosystems worldwide, they contain diverse soil organisms and effectively enhance soil stability and perform a series of key ecological functions. However, the geographical pattern of microbial communities in biocrusts is rarely assessed, despite it is closely related to the spatial variation of ecosystem functions in drylands. We assessed soil bacterial communities in biocrusts across four ecosystems (Gobi, desert, desert steppe and grassland) in a precipitation gradient (16–566 mm yr−1) in northern China. Bacterial OTU number and phylogenetic diversity did not linearly increase with decreasing aridity, they were significantly lower in Gobi and similar among desert, desert steppe and grassland. Soil bacterial community composition in Gobi and desert were different than those in desert steppe and grassland, and they were similar between Gobi and desert, this suggests the key role of habitat in structuring soil bacterial communities. The geographic pattern of soil bacterial communities was strongly influenced by both geographic distance and environmental factors. The first explanatory factor for the geographic variation of bacterial community dissimilarity differed among four ecosystems, being aridity in Gobi and desert, precipitation in desert steppe, and soil inorganic nitrogen in grassland. The geographic pattern of the bacterial functional group profile showed a similar pattern with community composition across four ecosystems, and the groups of containing mobile elements and gram negative bacteria were more abundant in drier habitats of Gobi and desert. Our results reveal the non-linear changes in diversity, composition and functional group of soil bacterial communities in biocrusts across the precipitation gradient from hyper-arid to semi-humid regions, and suggest that the geographic distance and habitat-specific environmental factors determine the distribution of soil bacterial communities in different ecosystems.
- Published
- 2020
22. The potential of δ2H-alkanes and δ18Osugar for paleoclimate reconstruction – A regional calibration study for South Africa
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Paul Strobel, Bruno Glaser, Michael Zech, Julian Struck, Torsten Haberzettl, Roland Zech, and Marcel Bliedtner
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Topsoil ,Environmental Engineering ,010504 meteorology & atmospheric sciences ,Phenology ,Fractionation ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,Pollution ,Evapotranspiration ,Soil water ,Paleoclimatology ,Environmental Chemistry ,Environmental science ,Aridity index ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Transpiration - Abstract
The hydrogen isotopic composition of leaf wax-derived n-alkanes (δ2Hn-alkanes) is a widely applied proxy for (paleo)climatic changes. It has been suggested that the coupling with the oxygen isotopic composition of hemicellulose-derived sugars (δ18Osugar) - an approach dubbed 'paleohygrometer' - might allow more robust and quantitative (paleo)hydrological reconstructions. However, the paleohygrometer remains to be evaluated and tested regionally. In this study, topsoil samples from South Africa, covering extensive environmental gradients, are analysed. δ2Hn-alkanes correlates significantly with the isotopic composition of precipitation (δ2Hp), whereas no significant correlation exists between δ18Osugar and δ18Op. The apparent fractionation (eapp) is the difference between δ2Hn-alkanes and δ2Hp (eapp 2H) and δ18Osugar and δ18Op (eapp 18O), respectively, and integrates i) isotopic enrichment due to soil water evaporation, ii) leaf (and xylem) water transpiration and iii) biosynthetic fractionation. We find no correlation of eapp 18O nor for eapp 2H with temperature, and no correlation of eapp 2H with potential evapotranspiration and an aridity index. By contrast, eapp 18O correlates significantly with both potential evapotranspiration and the aridity index. This highlights the strong effect of evapotranspirative enrichment on δ18Osugar. In study areas without plant predominance using Crassulacean Acid Metabolism (CAM), coupling δ18Osugar and δ2Hn-alkanes enables to reconstruct δ2Hp and δ18Op with an offset of Δδ2H = 6 ± 27‰ and Δδ18O = 0.8 ± 3.7‰, respectively, as well as relative humidity (RH) with an offset of ΔRH = 6 ± 17%. The paleohygrometer does, however, not work well for our study areas where CAM plants prevail (reconstructed δ18Op, δ2Hp and RH are off by 3.1‰, 27.2‰ and 31.7%). This probably reflects plant-specific (phenological) adaptations and/or post-photosynthetic exchange reactions related to CAM metabolism. Overall, our findings corroborate that δ2Hn-alkanes and δ18Osugar are valuable proxies, and the paleohygrometer is a promising approach for paleoclimate reconstructions in southern Africa.
- Published
- 2020
23. Watershed water-energy balance dynamics and their association with diverse influencing factors at multiple time scales
- Author
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Guoyong Leng, Pei Li, Qiang Huang, Shengzhi Huang, Hao Wang, and Jing Zhao
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Climate pattern ,geography ,Environmental Engineering ,Watershed ,Baseflow ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Drainage basin ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,Pollution ,Water resources ,Environmental Chemistry ,Environmental science ,Aridity index ,Waste Management and Disposal ,Water content ,Pacific decadal oscillation ,0105 earth and related environmental sciences - Abstract
The Budyko parameter, which controls the shape of Budyko curve, represents the superimposed impact of various periodic factors (including climatic factors, catchment characteristics, large-scale climate patterns, solar activity and anthropogenic activity) on the watershed water-energy balance dynamics. However, this superimposition is not conducive to identifying the drivers of Budyko parameter dynamics at different time scales, and thus affects parameter estimation. Here we obtain the Budyko parameter ω in the Fu’s equation (one form of the Budyko framework) for the Wei River Basin (WRB), and then adopt the Empirical Mode Decomposition method to reveal the relationships between factors and ω series at multiple time scales by considering the interplay among different influencing factors. Results indicate that (1) ω series are decomposed into 4-, 12-, 20-, exceeding 20-year time scale oscillations and a residual component with an significantly increasing trend in the mainstream of the WRB, a non-significantly decreasing trend in the Jing River Basin and Beiluo River Basin; (2) by analyzing the residual trend component, evaporation ratio, soil moisture and effective irrigated area are found to induce the significant increase of ω in the upstream of the WRB, whereas that in the middle and lower reaches is dominated by baseflow and Nino 3.4; (3) ω dynamics at the 4-year time scale is dominated by evaporation ratio, aridity index, baseflow and soil moisture; baseflow, Pacific Decadal Oscillation (PDO) and sunspots attribute to the dynamics at 12-year time scale; all the factors except baseflow and soil moisture contribute to the dynamics at 20- or exceeding 20-year time scales. The results of this study will help identify the connection between watershed water-energy balance dynamics and changing environment at multiple time scales, and also be beneficial for guiding water resources management and ecological development planning on the Loess Plateau.
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- 2020
24. Carrying capacity for vegetation across northern China drylands
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Bin Wu, Jutao Zhang, Shugao Qin, Xiuqin Wu, Yuqing Zhang, Yakun Zhu, Guodong Ding, and Yan Gao
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China ,Conservation of Natural Resources ,Biomass (ecology) ,Environmental Engineering ,010504 meteorology & atmospheric sciences ,media_common.quotation_subject ,Vegetation ,010501 environmental sciences ,01 natural sciences ,Pollution ,Desertification ,Evapotranspiration ,Environmental Chemistry ,Afforestation ,Environmental science ,Aridity index ,Biomass ,Physical geography ,Revegetation ,Leaf area index ,Waste Management and Disposal ,Ecosystem ,0105 earth and related environmental sciences ,media_common - Abstract
Revegetation and afforestation across drylands for establishing sustainable ecosystems requires a comprehensive understanding of the carrying capacity for vegetation (CCV) at the regional scale. To determine the CCV across drylands in northern China, we developed a technical framework based on two measures of leaf area index (LAI): maximum LAI (Max-LAI) and safe LAI (Safe-LAI), and their thresholds, CCVmax and CCVsafe, for six drylands (Horqin, Hulun Buir, Otindag, Mu Us, Tengger, and Junggar) using remote sensing datasets from 2000 to 2014. We also predicted dynamics of CCV of the drylands over the next decade (2015–2024) by establishing optimal prediction models based on environmental factors (temperature, precipitation, potential evapotranspiration, and elevation). According to these models, the Max-LAI threshold (range: 0.36–1.03 m2/m2) and Safe-LAI threshold (0.29–0.70 m2/m2) declined from east to west with decreases in aridity index. Under current climatic variability and anthropogenic disturbances, the CCV in most drylands would have positive increments (approximately 15%), except in the Horqin (approximately −15%) and Tengger (slight changes), during the following decade. This indicates that there is scope for improving vegetation coverage in most drylands, except in the Horqin and Tengger. Our results suggest that revegetation and ecosystem management to prevent ongoing desertification should be carried out at the regional scale. Although it does not account for biocrusts, artificially introduced vegetation, underground water, and other vegetation attributes (e.g., density and biomass), our technical framework and results might nonetheless be valuable in evaluating regional ecological security and guiding vegetation restoration of drylands across northern China.
- Published
- 2020
25. No till soil organic carbon sequestration could be overestimated when slope effect is not considered.
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Novara, Agata, Sarno, Mauro, and Gristina, Luciano
- Abstract
No tillage (NT) soil management has been considered a strategy for the implementation of environmental sustainability and a possible tool of soil organic carbon (SOC) sequestration. Considering the wide range of data on SOC change after NT application in relation to conventional tillage (CT) in different studies, further researches are needed over a diverse range of soil and climate before a proper estimation of the benefits can be provided by the NT. A data set composed of cereal cropping system studies, comparing the SOC content under CT and NT was compiled from the literature using the scientific repositories "Scopus" and "Science direct". This aims to i) discriminate and quantify the variation of SOC in relation to morphology (Flat area (FA) and Slope Area (SA)) and climates (Aridity index (Ai)); ii) provide a reliable forecast of C sequestration by NT in a specific environment. The results from collected datasets showed that SOC ratio between NT and CT was higher in sloping than flat areas and was also in correlation with the Ai. The average annual increase of SOC in NT in comparison to CT was 0.32 Mg ha−1y−1 and 0.21 Mg ha−1y−1 for SA and FA, respectively. The regression of the relative ratio (RR NT/CT) against Ai both for FA and SA showed a high statistical significance for FA. For SA the lack of significance is due to no response of the dependent variables to Ai changes and to the prevalent effect that NT has on the soil C erosion processes. These results highlighted that in SA, the SOC sequestration by NT is overestimated. These results provide concrete examples of the importance to discriminate soil morphology and climate when recommending NT soil management for soil C sequestration in order to individuate areas where NT can maximize its potentiality as a mitigation tool. Unlabelled Image • No tillage (NT) management has been considered a soil carbon sequestration tool. • A data set of studies comparing the soil C under CT and NT was compiled. • The study aimed to discriminate the C change in relation to soil morphology and climate. • Data showed an overestimation of C sequestration in slope area. • The relative SOC sequestration is inversely correlated to the aridity index. [ABSTRACT FROM AUTHOR]
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- 2021
- Full Text
- View/download PDF
26. Habitat-specific environmental factors regulate spatial variability of soil bacterial communities in biocrusts across northern China's drylands.
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Su, Yan-gui, Liu, Jie, Zhang, Bing-chang, Zhao, Hong-mei, and Huang, Gang
- Abstract
Biocrusts are common biotic components in dryland ecosystems worldwide, they contain diverse soil organisms and effectively enhance soil stability and perform a series of key ecological functions. However, the geographical pattern of microbial communities in biocrusts is rarely assessed, despite it is closely related to the spatial variation of ecosystem functions in drylands. We assessed soil bacterial communities in biocrusts across four ecosystems (Gobi, desert, desert steppe and grassland) in a precipitation gradient (16–566 mm yr−1) in northern China. Bacterial OTU number and phylogenetic diversity did not linearly increase with decreasing aridity, they were significantly lower in Gobi and similar among desert, desert steppe and grassland. Soil bacterial community composition in Gobi and desert were different than those in desert steppe and grassland, and they were similar between Gobi and desert, this suggests the key role of habitat in structuring soil bacterial communities. The geographic pattern of soil bacterial communities was strongly influenced by both geographic distance and environmental factors. The first explanatory factor for the geographic variation of bacterial community dissimilarity differed among four ecosystems, being aridity in Gobi and desert, precipitation in desert steppe, and soil inorganic nitrogen in grassland. The geographic pattern of the bacterial functional group profile showed a similar pattern with community composition across four ecosystems, and the groups of containing mobile elements and gram negative bacteria were more abundant in drier habitats of Gobi and desert. Our results reveal the non-linear changes in diversity, composition and functional group of soil bacterial communities in biocrusts across the precipitation gradient from hyper-arid to semi-humid regions, and suggest that the geographic distance and habitat-specific environmental factors determine the distribution of soil bacterial communities in different ecosystems. Unlabelled Image • Bacterial diversity and functional group pattern in biocrusts were studies in four ecosystems. • MAP, SOC and soil bulk density drove the contrasting β-diversity patterns across ecosystems. • Factors driving bacterial dissimilarity shifted from aridity index in dry ecosystems to In-N in grassland. • Bacterial dissimilarity increased slowly with geographic distance grassland than the other ecosystems. • Bacterial functional group profile was significantly different among four ecosystems. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
27. Coupling between plant nitrogen and phosphorus along water and heat gradients in alpine grassland.
- Author
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Zhou, Tian-Cai, Sun, Jian, Liu, Miao, Shi, Pei-Li, Zhang, Xu-Bo, Sun, Wei, Yang, Gang, and Tsunekawa, Atsushi
- Abstract
• Different patterns between plant nitrogen (N) and phosphorus (P) in community were detected in alpine grasslands. • The coupling between plant N and P were mediated by the water and heat availability. • Plants tend to be more flexible in their N:P stoichiometry at high variability of soil nutrient in arid environments. • Plant N and P tightly coupled at higher soil nutrient availability and less nutrient variability. The biogeochemical cycles of plant nitrogen (N) and phosphorus (P) are interlinked by ecological processes, and the N and P cycles become uncoupled in response to global change experiments. However, the complex natural hydrothermal conditions in arid, semiarid and humid grassland ecosystems may have different effects on the availability of soil nutrients and moisture and may induce different balances between the N and P cycles. Here, we evaluated how the aridity index (AI) affects the balance between N and P of alpine grassland by the collected 115 sites along water and heat availability gradients on the Tibetan Plateau. We found that AI was negatively related to the variation in the coefficients of soil total dissolved N (TDN) and soil availability of P (SAP), and positive effects of AI, TDN and SAP on the coupling of plant N and P were detected. Thus, AI was positively correlated with soil nutrients and moisture, which may favor the co-uptake of soil nutrients by plants, resulting in a small variation in plant N and P in humid environments. Conversely, in arid environments with temporally variable soil nutrients, the plants tend to be more flexible in their N:P stoichiometry. Generally, our findings suggest that plant N and P could be more strongly coupled in humid conditions than in arid environments across alpine grasslands, with potential decoupling of the N biogeochemical cycle from P in an arid environment with an asynchronous dynamic of temperature and precipitation. [ABSTRACT FROM AUTHOR]
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- 2020
- Full Text
- View/download PDF
28. Spatio-temporal transpiration patterns reflect vegetation structure in complex upland terrain.
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Metzen, Daniel, Sheridan, Gary J., Benyon, Richard G., Bolstad, Paul V., Griebel, Anne, and Lane, Patrick N.J.
- Abstract
Topography exerts control on eco-hydrologic processes via alteration of energy inputs due to slope angle and orientation. Further, water availability varies with drainage position in response to topographic water redistribution and the catena effect on soil depth and thus soil water storage capacity. Our understanding of the spatio-temporal dynamics and drivers of transpiration patterns in complex terrain is still limited by lacking knowledge of how systematic interactions of energy and moisture patterns shape ecosystem state and water fluxes and adaptation of the vegetation to these patterns. To untangle the effects of slope orientation and hillslope position on forest structure and transpiration patterns, we measured forest structure, sap flux, soil moisture, throughfall and incoming shortwave radiation along two downslope transects in a forested head water catchment in south-east Australia. Our plot locations controlled for three systematically varying drainage position levels (topographic wetness index: 5.0, 6.5 and 8.0) and two levels of energy input (aridity index: 1.2 and 1.8). Vegetation patterns were generally stronger related to drainage position than slope orientation, whereas sap velocity variations were less pronounced. However, in combination with stand sapwood area, consistent spatio-temporal transpiration patterns emerged in relation to landscape position, where slope orientation was the primary and drainage position the secondary controlling factor. On short temporal scales, radiation and vapor pressure deficit were most important in regulating transpiration rates, whereas soil water limitation only occurred on shallow soils during summer. The importance of stand structural parameters increased on longer time scales, indicating optimization of vegetation in response to the long-term hydro-climatic conditions at a given landscape position. Thus, vegetation patterns can be conceptualized as a 'time-integrated' predictor variable that captures large fractions of other factors contributing to transpiration patterns. Unlabelled Image • Annual transpiration varied up to two-fold within 200 m distance. • Slope orientation primary and drainage position secondary control of transpiration • Vegetation patterns relate more strongly to drainage position than slope orientation. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
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