Redistribution process of precipitation in ecological restoration activity of Pinus sylvestris var. mongolica in Mu Us Sandy Land,China

Precipitation is the most important water resource in semi-arid regions of China. The redistribution of precipitation among atmospheric water, soil water and groundwater are related to the land surface afforested ecological system. The study took widely replanted Pinus sylvestris var. Mongolica (PSM) in Mu Us Sandy Land (MUSL) as a research object and monitored precipitation, soil moisture, sap flow, and deep soil recharge (DSR) to find out moisture distribution in shallow soil layers. Results showed that the restoration process of PSM in MUSL changed the distribution of precipitation, with part of it infiltrating downward as DSR and part of it being stored in the shallow soil. Consequently, evapotranspiration increased and DSR significantly decreased, resulting in up to 466.9 mm of precipitation returning to the atmosphere through evapotranspiration in 2016. Vegetation increased soil water storage (SWS) capacity, with maximum SWS in PSM plot and bare sandy land (BSL) being 260 mm and 197 mm per unit horizontal area, respectively in 2016. DSR decreased from 54% of precipitation in the BSL plot to 0.2% of precipitation in the PSM plot in 2016. A great portion of infiltrated water was stored in the PSM ecosystem, resulting in a time lag of infiltration to reach the deep soil layer, and the infiltration rate in the BSL plot was 11 times of that in the PSM plot. SWS decreased 16 mm and 7.6 mm per unit horizontal area over a one-year period (from March to October, non-freezing time) in 2017 and 2019, respectively. The PSM annual sap flow was maintained at a relatively constant level of 154 mm/yr. Through in-situ measurement and comparative analysis of the precipitation redistribution of the BSL plot and the PSM plot, we find that PSM can significantly reduce the shallow soil water storage and DSR. However, substantial reduction of shallow soil water storage and DSR is detrimental for the long-term development of PSM forest. Therefore, it is necessary to reduce PSM density to cut the water consumption by PSM per unit area, thus to augment the shallow SWS and DSR, which will be beneficial for the PSM to survive under extreme drought conditions in the future. This study helps us understand the role of precipitation-induced groundwater recharge in the process of vegetation restoration in semi-arid regions and explains the possible causes of PSM forest degradation.     

基于WQI法的滴水湖及入湖河道水质研究

选取2018年8月至2019年7月间滴水湖及入湖河道区域水质调查数据及月平均降水量，按照水系特征及土地利用规律将研究范围分为五个区域。采用综合水质标识指数（WQI）法，评价分析水质时空分布规律；将该地区月平均降水量与氨氮和总氮进行比较分析。结果表明，滴水湖及入湖河道的水质具有空间上的差异性，外涟河、中涟河、内涟河、入湖口为“中等”，滴水湖区水质为“良好”，从外涟河到滴水湖区的水质呈现出逐渐变好的状态；和WQI显著相关的水质参数有总氮、氨氮等；降水对氨氮和总氮具有稀释作用。水质季节变化主要影响因子为水温和降水，空间变化主要影响因子为引水水源水质和人类活动。最后，根据该区域水质特征和影响因子，提出了生物治理法、改建雨水排放管道和加强重要指标监测等治理对策。     

1960—2017年长武县气候变化特征分析

本文利用长武县气象局1960—2017年近58年气温和降水的观测数据,运用线性回归、滑动平均、Mann-Kendall突变检验等研究方法,初步研究了长武县近58年气温和降水量变化特征。结果表明：在1960—2017年间,长武县年均温明显升高,增长速率为0.18℃/10 a,并在2004年发生趋势性突变;最冷月、最热月的平均气温都显著上升,增温速率分别为0.13℃/10 a和0.06℃/10 a;1960—2017年间,长武县年降水量明显下降,下降速率为4.31 mm/10 a,未发生趋势性突变;汛期降水量整体呈波动上升趋势,上升速率为3.65 mm/10 a,汛期降水量很大,约占年降水量的82%。     

降水变化和氮沉降对荒漠草原土壤丛枝菌根真菌群落结构的影响

降水变化和氮沉降是影响植物、微生物和土壤环境变化的两个重要方面。尽管丛枝菌根（AM）真菌在陆地生态系统中起着至关重要的作用，但人们对降水变化和氮添加如何交互影响AM真菌群落仍知之甚少。本研究以短花针茅荒漠草原为研究对象，采用裂区设计，主区为自然降雨(CK)、增雨30%(W)和减雨30%(R)三个水分梯度，副区为0(N0)，30(N30)，50(N50)和100(N100) kg?hm-2?a-1 四个氮素梯度共12个处理，通过高通量测序分析了土壤中AM真菌群落的多样性和组成。结果发现，水分处理对土壤AM真菌的Alpha多样性有促进作用，氮素处理抑制了土壤AM真菌的Alpha多样性，水分增加和氮素添加的交互作用促进了AM真菌的Alpha多样性增加，并改变了土壤AM真菌群落组成。水分和氮素刺激了各功能型植物生物量的增加，氮添加使多年生杂草和半灌木、小半灌木生物量显著增加，多年生禾草生物量显著减少。此外，多型孢子菌科的相对丰度与一二年生植物和半灌木、小半灌木生物量呈显著正相关，一二年生植物和半灌木、小半灌木生物量在氮添加和增雨处理下增加。本研究证明了AM真菌群落在短期气候变化下的稳定性。此外，AM真菌在科水平上的丰度与各生活型植物地上生物量的相关性证明了地上和地下生态系统的连通性。     

基于主成分分析降水量指标预测棉铃虫百株卵量模型研究

棉铃虫是中国棉花主要害虫之一,降水量对其种群数量具重要影响。采用连续10a棉铃虫第2代和第3代的百株卵量与同期降水量指标资料,通过相关系数法筛选出10个预测第2代、第3代棉铃虫的降水量指标,采用主成分分析法建立第2代、第3代棉铃虫百株卵量的特征预测模型。检验结果表明,第2代棉铃虫的预测模型信度较好,历史符合率为70%;而第3代棉铃虫的预测模型信度较差,历史符合率为40%。由于入选因子均为前兆因子,因此,第2代棉铃虫的预测模型可用于区域棉铃虫发生程度的监测和预警研究。