Relative humidity and agricultural activities dominate wildfire ignitions in Yunnan, Southwest China: Patterns, thresholds, and implications

2018 ◽

Vol 226 (2) ◽

pp. 333-354

Author(s):

D. Jinan Seger Abid Azooz AL-Qaraghouli

Keyword(s):

Relative Humidity ◽

Geographical Distribution ◽

Climatic Factor ◽

Agricultural Activities ◽

Agricultural Crops ◽

Natural Factor ◽

Leguminous Crops ◽

Climatic Elements ◽

Climate Study

The climate is the most important natural factor affecting agriculture . the success of planting any agricultural crops depends on the nature of the climate prevailing in the area of cultivation . the most important climatic elements that have an effective effect in the cultivation of leguminous crops and the various agricultural activities that can be practiced are : Temperature , rain , wind and relative humidity . when the climatic reguirements of any crop are well – established , its cultivation is successful and profitable, and vice versa when those reguirements are not met . the study of the climatic reguirements of leguminous crops covered by the study and its balance with the available climatic potential in Erbil governorate in order to know the role of the climatic factor in the cultivation of these crops and their geographical distribution .

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Hydrogeochemical Dynamics and Response of Karst Catchment to Rainstorms in a Critical Zone Observatory (CZO), Southwest China

Frontiers in Water ◽

10.3389/frwa.2020.577511 ◽

2020 ◽

Vol 2 ◽

Author(s):

Caiqing Qin ◽

Hu Ding ◽

Si-Liang Li ◽

Fu-Jun Yue ◽

Zhong-Jun Wang ◽

...

Keyword(s):

Surface Water ◽

Southwest China ◽

Critical Zone ◽

Karst Water ◽

Agricultural Activities ◽

Carbonate Weathering ◽

Hydrogeological Conditions ◽

Surface Water And Groundwater ◽

Critical Zone Observatory ◽

Karst Catchment

Karst water is vital for local drinking and irrigation but is susceptible to contamination. Hydrochemistry, which is highly related to carbonate weathering in karst catchments, can affect water quality and respond rapidly to climate change. In order to explore hydrogeochemical sources, dynamics, and their responses to rainstorms, rainwater, throughfall, hillslope runoff, surface water, and groundwater were sampled synchronously during rainstorms at a karst Critical Zone Observatory (CZO), Southwest China. Results showed that the total dissolved solids (TDS) concentration in throughfall increased by 30.1 ± 8.0% relative to rainwater, but both throughfall and rainwater contributed little to TDS in surface water and groundwater compared with terrestrial sources. Hydrochemistry in surface water and groundwater was diluted by rainstorms but displayed chemostatic responses with different intensities to increasing discharge. This is possibly regulated by hydrogeological conditions, available sources of various solutes, and the difference between solute concentrations before and after rainstorms. Ca2+ and Mg2+ dynamics were mainly regulated by carbonate weathering, gypsum dissolution, and gypsum-induced dedolomitization (geological sources), which also affect Ca2+, Mg2+, and SO42- in deep confined groundwater draining a gypsum stratum. For HCO3-, CO2 from respiration and microbiologic activities is one dominant contributor, especially for spring. The chemostatic behaviors of NO3-, Cl−, and K+ were related to agricultural activities, especially in surface water. These controls on hydrochemistry may already exist as hillslope runoff occurs, which has be further demonstrated by principle component analysis (PCA). The heterogeneous permeability of epikarst can affect the mixture of groundwater from different sources and flowing pathways, enabling hydrochemistry at different hydrogeological conditions to display discrepant responses to rainstorms. The epikarst aquifer with high permeability is susceptible to changes in external environment, such as rainstorms and agricultural activities, increasing the potential risk of water environment problems (chronic pollution of nitrogen and high hardness of water) during a certain period. Drinking water safety thus deserves consideration in the agricultural karst catchment.

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Geochemical Behaviors of Rare Earth Elements (REEs) in Karst Soils under Different Land-Use Types: A Case in Yinjiang Karst Catchment, Southwest China

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18020502 ◽

2021 ◽

Vol 18 (2) ◽

pp. 502

Author(s):

Ruiyin Han ◽

Zhifang Xu

Keyword(s):

Rare Earth ◽

Rare Earth Elements ◽

Southwest China ◽

Secondary Forest ◽

Soil Samples ◽

Soil Profiles ◽

Agricultural Activities ◽

Soil Environment ◽

Forest Land ◽

Abandoned Cropland

The geochemical characteristics of rare earth elements (REEs) can be employed to identify the anthropogenic and natural influence on the distributions of REEs in soils. A total of 47 soil samples from the three soil profiles of the secondary forest land, abandoned cropland, and shrubland in the Yinjiang county of Guizhou province, southwest China, were collected to determine the contents and distribution of REEs in the soil environment. The total REEs (ΣREE) contents in different soil profiles are in the following sequence: secondary forest land (mean: 204.59 mg·kg−1) > abandoned cropland (mean: 186.67 mg·kg−1) > shrubland (mean: 139.50 mg·kg−1). The ratios of (La/Gd)N and (Gd/Yb)N ranged from 0.62 to 1.00 and 1.18 to 2.16, which indicated that the enrichment of the medium rare earth elements (MREEs) was more obvious than that of the light rare earth elements (LREEs) and the heavy rare earth elements (HREEs). The phenomenon could be attributed to the preferential absorption of MREEs by fine particles and the substitution of Ca2+ by MREEs. Most soil samples were characterized by the negative Ce anomalies (anomalies values: 0.30–1.10) and positive Eu anomalies (anomalies values: 0.43–2.90). The contents of REEs in the profiles of secondary forest land and shrubland were mainly regulated by soil pH and Fe contents while clay content and agricultural activities were the main controlling factors in the soil profile of abandoned cropland. This study highlights the role of agricultural activities in affecting the distributions of REEs in karst soils, which could provide some insights for the protection of the soil environment.

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Quantitative Analysis of Vegetation Dynamics in Response to Climatic Factors and Human Activities in Southwest China

10.21203/rs.3.rs-1165782/v1 ◽

2021 ◽

Author(s):

Cuiping Yang ◽

Yongqiang Wang ◽

Jiujiang Wu ◽

xiaoyi ma

Keyword(s):

Relative Humidity ◽

Time Scale ◽

Human Activities ◽

Interannual Variation ◽

Southwest China ◽

Climatic Factors ◽

Sunshine Duration ◽

Spatial And Temporal Variability ◽

Delayed Response ◽

Mean Temperature

Abstract We determined the time scale of normalized difference vegetation index (NDVI) response to drought and used trend and correlation analyses to explore the spatial and temporal variability characteristics of the NDVI and SPEI and their sensitivity to climatic factors in southwest China from 2000 to 2020. We used a partial derivative approach to calculate the contributions of six climatic factors and human activities to the interannual variation in the NDVI. The results demonstrated that from 2000 to 2020, the annual mean NDVI in southwest China showed a slight decreasing trend at a rate of 0.0001 y−1. The NDVI had the highest sensitivity to the standardized precipitation and evapotranspiration index on a 12-month time scale. The NDVI exhibited a 1-year delayed response to drought. The SPEI has the highest sensitivity to precipitation. The percentage of pixels with a positive correlation between NDVI and precipitation, mean temperature, temperature difference, mean relative humidity, mean wind speed, and sunshine duration in the study area was 31.73%, 46.81%, 35.49%, 25.76%, 39.36%, and 39.89%, respectively. The average contributions of these six climatic factors to the interannual variation of NDVI were 0.00029, 0.00046, −0.00007, 0.00007, 0.0008, and 0.00001 y−1, respectively. The NDVI had the highest sensitivity to mean temperature and the lowest sensitivity to mean relative humidity. The average contributions of climatic factors and human activities to interannual variability in southwest China were 0.00156 and 0.00012 y−1, respectively. The positive influence of climatic factors on the NDVI was stronger than that of human activities. This study provides a theoretical basis for the sustainable management of the regional ecological environment.

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