黔南州2013年和2011年两次夏季干旱对比分析

利用黔南州12个气象观测站的雨量、气温等资料,按照《贵州干旱标准》中的5 d滑动等方法分析比较2013年和2011年两次严重夏季干旱的特点:前期1—6月的降水量2 a都偏少,2011年偏少得更多;2013年入旱时间各地差异较大,干旱的时间长短不一,2011年入旱时间较集中,干旱的时间较长;干旱期间降水量2011年偏少得更多;2013年的干旱多数地区于8月结束,2011年结束于9月底。总体来说,2011年为特重夏旱年,而2013年是重夏旱年,2011年的夏旱灾害较2013年的更严重。

Analysis on the Hydrochemical Characteristics of Groundwater and the Formation Reason in Wadi Bay Area of Libya

[Objective] The research aimed to analyze the formation reason of groundwater hydrochemical characteristics in the dry valley area of Wadi Bay of Libya and provide the scientific basis for the reasonable development utilization and the environmental protection of groundwater.[Method] Took Wadi Bay area（dry valley）of Libya as the example,Piper trilinear graphic representation method,the descriptive statistics,the ion ratio coefficient method and the isotope evidence were used to systematically study the special hydrochemical characteristics of shallow groundwater in the arid climate condition in Wadi Bay area of Libya.[Result] The salt content of groundwater in the area was very high,and TDS was during 3.2-8.4 g/L.The main groundwater type was Cl·SO4-Na·Ca,then was Cl·SO4-Na·Ca·Mg.The concentrations of Cl-,Na＋ and SO2-4,etc.in the groundwater in 70 km from the sea had the remarkable variation,but the concentrations of Mn2＋,Ba2＋,Si2＋,NH＋4 and NO-3 didn＇t have the same variation phenomenon.[Conclusion] The hydrochemical characteristics of shallow groundwater didn＇t relate to the dissolution infiltration reaction,the evaporation concentration effect and human activities.The major cause was the mixing effect of salt and fresh water in the invasion process of seawater.

Woody plant encroachment may decrease plant carbon storage in grasslands under future drier conditions

Aims Woody plants are widely distributed in various grassland types along the altitudinal/climatic gradients in Xinjiang,China.Considering previously reported change in carbon(C)storage following woody plant encroachment in grasslands and the mediating effect of climate on this change,we predicted that a positive effect of woody plants on plant C storage in semiarid grasslands may revert to a negative effect in arid grasslands.We first investigated the spatial variation of aboveground C(AGC)and belowground C(BGC)storage among grassland types and then tested our prediction.Methods We measured the living AGC storage,litter C(LC)and BGC storage of plants in two physiognomic types,wooded grasslands(aboveground biomass of woody plants at least 50%)and pure grasslands without woody plants in six grassland types representing a gradient form semiarid to arid conditions across Xinjiang.Important Findings Living AGC,LC,BGC and total plant C storage increased from desert to mountain meadows.These increases could also be explained by increasing mean annual precipitation(MAP)or decreasing mean annual temperature(MAT),suggesting that grassland types indeed represented an aridity gradient.Woody plants had an effect on the plant C storage both in size and in distribution relative to pure grasslands.The direction and strength of the effect of woody plants varied with grassland types due to the mediating effect of the climate,with wetter conditions promoting a positive effect of woody plants.Woody plants increased vegetation-level AGC through their high AGC relative to herbaceous plants.However,more negative effects of woody plants on herbaceous plants with increasing aridity led to a weaker increase in the living AGC in arid desert,steppe desert and desert steppe than in the less arid other grassland types.Under greater aridity(lower MAP and higher MAT),woody plants allocated less biomass to roots and had lower BGC and had a more negative impact on herbaceous plant production,thereby reducing vegetation-level BGC in the desert,steppe desert and desert steppe.In sum,this resulted in a negative effect of woody plants on total plant C storage in the most arid grasslands in Xinjiang.As a consequence,we predict that woody plant encroachment may decrease rather than increase C storage in grasslands under future drier conditions.

Deep soil water infiltration and its dynamic variation in the shifting sandy land of typical deserts in China

Soil moisture is the key resource constraint in arid ecosystems, and has been a focus of research on restoration. However, quantitative studies on the contribution of rainfall to deep soil rainfall infiltration are lacking. In this study, we used the YWB-01 Deep Soil Infiltration Water Recorder which had been invented by ourselves to measure the quantity of rain infiltration into deep soil, 150 cm below ground, in four locations in China: Mu Us Sandy Land and Ulan Buh, Tengger, and Badan Jilin deserts over a 2-year period. We found:(1) Deep soil rainfall infiltration decreased progressively from east to west and from semiarid to arid areas, with two locations completely lacking rainfall infiltration. Heavy rain was important to deep soil infiltration in shifting sandy land of arid and semiarid areas.(2) Seasonal variation of infiltration was correlated with rainfall, with a time lag that was less apparent in areas with more rainfall.(3) For single intense rainfall events, infiltration maximums occurred 40–55 h after the rainfall, during which the infiltration rates increased rapidly before reaching a peak, and then decreased slowly. Continuous infiltration could last about 150 h. Rainfall infiltration was determined by the combined action of intensity, quantity and duration. Rainfall with low intensity, long duration, and large quantity was most favorable for deep soil infiltration. Our results can be used in water resource assessments and protection during eco-restoration in the arid and semiarid areas in China.