基于气象因子的长三角地区农田站点土壤水分时间序列预测

以长三角3省1市为研究区,旨在构建长三角地区土壤水分长时间序列,为农业生产和遥感算法提供数据支撑。研究基于空间匹配的站点土壤水分数据和气象数据,利用主成分分析得到4个有效主成分作为线性回归和BP神经网络模型的输入因子,建立土壤水分与气象因子间的定量关系,并评估所构建模型的精度。结果表明,基于全部站点数据建立的单一BP神经网络模型优于单一线性回归模型。单一线性回归模型的R 2=0.34,RMSE=0.046 m³/m³,MAE=3.67%;而单一BP神经网络模型的训练、验证和测试3个数据集的R 2均在0.64以上,RMSE<0.043 m³/m³,MAE低于3.4%。根据逐个站点分别构建分站点的BP神经网络模型,其总体精度高于基于全部站点数据构建的单一BP神经网络模型。分站点构建的BP神经网络模型的总体精度方面,3个数据集的R 2均值在0.75以上,RMSE<0.039 m³/m³,MAE低于3%。通过对逐个站点分别构建BP神经网络模型,获得了精度较高、较稳定的土壤水分拟合结果。     

Intercropping and Crop Residue Incorporation: Effects on Soil Nutrient Status

ABSTRACT

A maize-melon mixture relayed into a cassava-soybean intercrop was established at Ibadan, Nigeria, between 1995 and 1997 in order to study the changes in soil-nutrient status, that occurred due to soybean intercropping and residue incorporation. The experiment was conducted on a Kanhaplic Haplustalf soil. Soybean was planted in drills between cassava rows after harvesting maize and melon. Soybean stover was recycled into half of the soybean plots. Cassava yield was reduced by about 16% with soybean intercropping without the residue incorporation and by about 11% with incorporation of the crop residue. Soil pH was significantly reduced from an initial 6.0 to 5.7 with soybean intercropping. Organic matter was drastically reduced from an initial 31.0 g kg^?1 to 5.3 g kg^?1 with sole cassava cropping, and to 10.1 g kg^?1 with soybean intercropping and incorporation of crop residue. Total nitrogen (N) was also significantly reduced to about 0.4 g kg^?1from an initial content of 1.8 g kg^?1, while the available phosphorus (P) was increased from 1.8 to an average of 4.0 mg kg^?1. The exchangeable potassium (K) and effective cation-exchange capacity (ECEC) were not significantly affected.     

2001-2018年西江流域水分利用效率时空变化及影响因素

[目的]探究气候变化形势下流域的碳循环和水循环相互关系,对流域的水资源科学配置有重大意义。[方法]以西江流域为例,基于2001—2018年GLASS产品中的初级生产力(GPP)和蒸散发(ET)数据,定量计算区域生态系统植被水分利用效率(WUE),利用趋势分析和偏相关分析的方法研究植被WUE时空演变特征及其影响因素。[结果]2001—2018年西江流域植被的WUE总体呈增加趋势;林地的WUE增长速率最快,草地次之,耕地最慢。从空间分布来看,WUE值从广西中部的耕地向四周逐渐升高,WUE低值还零星分布在云南东部的台地和丘陵地区;西江流域15.23%,12.12%的区域WUE分别与气温、降水呈显著正相关;11.54%的区域WUE与太阳辐射呈显著负相关;NDVI与WUE具有显著正相关性;WUE随海拔的上升呈上升—平缓—上升的趋势,在2 100 m左右,WUE出现明显波动。[结论]气候因子、NDVI、海拔、人类活动均不同程度影响西江流域植被的水分利用效率,本研究可为西南喀斯特地区石漠化治理和流域生态防护林体系的建设提供参考。     

2000-2019年关中平原城市群植被NPP时空变化及影响因素

[目的]分析和探讨关中平原城市群植被NPP的时空变化特征,揭示影响植被NPP变化的主要因素,为区域生态恢复及生态健康评估提供支持。[方法]运用趋势分析、变异系数和地理探测器等方法,分析了2000—2019年关中平原城市群植被NPP的时空变化特征与规律,并对植被NPP的影响因素进行了探测。[结果]关中平原城市群年均植被NPP值介于340.3～573.5 g C/m²,年均增长率为9.1 g C/m²,整体呈波动上升趋势,且不同地貌区NPP增长趋势相似。大部分区域植被NPP变化速率大于0,且变异系数较小,植被NPP以小幅增加为主。空间上,植被NPP南高北低,西高东低,具有明显空间分异性,是自然、社会因素共同作用的结果。植被NPP的主要影响因素为降水、地貌及≥10℃积温,但因子间的复杂耦合作用对植被NPP的影响更为显著,如降水与气温的交互作用对植被NPP的解释力达到57%以上,探测结果表明两两因子的交互作用呈现相互增强效应。[结论]关中平原城市群大部分地区植被NPP有明显增长,表明区域生态环境有较大改善。     

Limitations of farm management data in analyses of decadal changes in SOC stocks in the Danish soil-monitoring network

Changes in soil organic carbon (SOC) storage in agricultural land are an important part of the Land Use, Land-Use Change and Forestry component of national greenhouse gas emission inventories. Furthermore, as climate mitigation strategies and incentives for carbon farming are being developed, accurate estimates of SOC stocks are essential to verify any management-induced changes in SOC. Based on agricultural mineral soils in the Danish soil-monitoring network, we analysed management effects on SOC stocks using data from the two most recent surveys (2009 and 2019). Between 2009 and 2019, the average increase in SOC stock was 1.2 Mg C ha⁻¹ for 0–50 cm despite a loss of 1.2 Mg C ha⁻¹ from the topsoil (0–25 cm), stressing the importance of including deeper soil layers in soil-monitoring networks. Comparing all four national surveys (1986, 1997, 2009, 2019), the mean SOC stock of mineral soils in Denmark appears stable. The change in SOC stock between 2009 and 2019 was analysed in detail in relation to management practices as reported by farmers. We found that the effects of single management factors were difficult to isolate from co-varying factors including soil parameters and that the use of farm management data to explain changes in SOC stocks observed in soil-monitoring networks appears limited. Uncertainty in SOC stock estimates also arises from low sampling frequency and statistical challenges related to regression to the mean. However, repeated stock measurements at decadal intervals still represent a benchmark for the overall development in regional and national SOC storage, as affected by actual farm management.     

InVEST模型在市县级水源涵养功能评价中的应用——以广东省广州市为例

[目的] 评估InVEST模型应用在市县级水源涵养功能重要性评价的适用性,探析以海绵城市建设试点且高度城市化的广东省广州市水源涵养服务时空变化特征与区域差异,为区域社会经济发展、生态环境保护与恢复政策的制定提供理论依据。[方法] 利用对比分析法分别评估InVEST水源涵养评估模型与相关“指南”——《资源环境承载能力和国土空间开发适宜性评价技术“指南”》推荐模型在区域水源涵养服务相关结果评价中的精确性,并利用GIS空间分析方法分析2013—2017年广州市的水源涵养服务时空分异特征。[结果] ①基于InVEST的水源涵养评估模型评估结果精度高,水源涵养功能重要性评价结果同样符合要求。②广州市水源涵养总量呈现先升后降,总体保持一定增长的态势,高值集中在水域和东北部多林地区域,低值集中在城市中心建成区。③区域整体水源涵养功能提升,但不同行政区划和地类存在差异,行政区中海珠区、番禺区和荔湾区提升较大;地类中耕地和建设用地有所提升,林地基本不变,而草地有所减弱。④各水源涵养功能重要性分区面积比例接近,但各分区内部不同地类比例存在差异。[结论] ①基于InVEST的水源涵养评估模型相比“指南”模型准确性更高,在规划领域具有很好的应用前景。②广州市水源涵养量空间分异明显,2013—2017年整体水源涵养功能提升。     

基于GEE数据平台的北洛河流域1970-2019年土地利用结构变化特征

[目的] 探究北洛河流域土地利用时空变化及其驱动力,为该区土地资源优化、环境质量改善和水沙生态要素变化分析等提供科学依据。[方法] 基于GEE平台整理和处理北洛河流域1970—2019年间6期遥感影像数据,从时间变化、动态度、转移方向和空间分布等角度分析流域土地利用变化特征,并对其驱动因素进行探讨。[结果] 研究时段内,北洛河流域土地利用类型以耕地、林地和草地为主,数量结构从2000年前的1：1.1：0.6变化到2000年后的1：2.7：0.7。1970—2019年研究区耕地、草地和水域的减少率分别为16.6%,6.7%和0.1%,林地和建设用地的面积增加率为19.9%和1.3%。流域耕地和草地斑块趋于分散且简单化,林地斑块趋于聚集和复杂化。土地利用转移主要以耕地转林地、耕地转建设用地和草地转林地为主。流域土地利用综合动态度先增后减,2000—2010年间达最大。流域中,上游丘陵沟壑区土地利用结构变化最为显著,其次为中游的甘泉、宜君、华池、合水等县。[结论] 国家政策的演变、社会经济发展和人口增长决定了土地利用变化的方向和程度,自然因素为长期辅助影响因素。     

Soil degradation during the period 1967–1995 in Bangladesh

Long-term changes in carbon and nitrogen storage in the top 100 em layers of soils from different physiographic units in Bangladesh were evaluated using 460 soil samples from 43 profiles collected in 1967 and 1994/95. The study area consisted of ten physiographic units, viz.: Old Himalayan Piedmont Plain (OHP), Tista Floodplain (TF), Barind Tract (BT), Ganges Floodplain (GF), Madhupur Tract (MT), Brahmaputra Floodplain (BF), Meghna River and Estuarine Floodplain (MF), Surma-Kushiyara Floodplain (SKF), Northern and Eastern Piedmont Plain (NEP), and Chittagong Coastal Plain (CCP).

During the period 1967–1995, mean values of soil carbon and nitrogen declined by 16.2 t C ha^-1 and 1.38 t N ha^-1 in Bangladesh. The total carbon and nitrogen budgets showed a fall of 42.8 × 10⁶ t C and 3.36 × 10⁶ t N within the 27 y period in Bangladesh. All the physiographic units showed a decline in carbon and nitrogen contents except for BT which showed an increase of 3.76 t C ha^-1 and 0.77 t N ha^-1 for these elements. MT showed the highest decline in carbon (30.5 t C ha^-1) and nitrogen (3.25 t N ha^-1). The lowest decline in carbon was observed in SKF (7.18 t C ha^-1) while the same applied to nitrogen in GF (0.50 t N ha^-1). The other physiographic units showed a moderate decline in the contents of these elements.

Based on the land area occupied by the sampled soil series of each physiographic unit, GF showed the highest decline of 13.7×10⁶ t C and a moderate decline of 0.52 × 10⁶ t N. Decrease in the carbon level for BF was moderate (9.31 × 10⁶ t C) but the decline in the nitrogen level was the highest (0.95 × 10⁶ t N). Decrease in the amount of carbon and nitrogen stored for the other physiographic units was: OHP (0.67 × 10⁶ t C, 0.03 × 10⁶ t N), TF (2.54 × 10⁶ t C, 0.25 × 10⁶ t N), MT (4.28 × 10⁶ t C, 0.45 × 10⁶ t N), MF (6.06 × 10⁶ t C, 0.61 × 10⁶ t N), SKF (2.87×10⁶ t C, 0.24×10⁶ t N), NEP (2.68×10⁶ t C, 0.22×10⁶ t N), and CCP (0.81 × 10⁶ t C, 0.11 × 10⁶ t N). Increase in carbon and nitrogen contents was only observed in BT (0.08 × 10⁶ t C, 0.02 × 10⁶ t N).     

American Wine Society

This article describes the digitization of the Alabama Agricultural Experiment Station publications. This collection forms part of the United States Agricultural Information Network (USAIN) National Preservation Program for Agricultural Literature and the State and Local Literature Preservation Projects that are similar in scope to Cornell's Core Historic Literature of Agriculture digital collection. These are nationwide projects that seek to preserve scholarly literature in agriculture. Project planning and implementation is described, followed by a discussion of the potential usefulness of this collection and ways of promoting its use to various user groups.     

Haematological and biochemical profiles of carp blood following nitrite exposure at different concentrations of chloride

Haematological parameters of 2‐year‐old carp (Cyprinus carpio L.) were assessed to study the protective effect of chloride on the health of fish exposed to elevated nitrite concentrations. Four groups of carp were exposed to different concentrations of nitrite and chloride for 96 h (group E1: 67 mg L^?1 NO₂^?, 11 mg L^?1 Cl^?; group E2: 67 mg L^?1 NO₂^?, 100 mg L^?1 Cl^?; group E3: 0 mg L^?1 O₂^?, 100 mg L^?1 Cl^? and group C: 0 mg L^?1 NO₂^?, 11 mg L^?1 Cl^?). The main haematological response of carp to an acute exposure to nitrite (group E1) was a significant decrease (P<0.05) in haemoglobin concentrations (53.40±6.61 g L^?1), haematocrit (0.21±0.02 LL^?1), erythrocyte count (1.13±0.12 TL^?1), leucocyte count (7.1±4.19 GL^?1) and lymphocyte count (5.28±2.51 GL^?1), and a significant increase in methaemoglobin concentration (90.50±4.38%, P<0.01) and mean corpuscular haemoglobin concentration (0.27±0.2 LL^?1, P<0.05). At higher chloride concentrations (group E2), a lower nitrite toxicity was observed. In group E2 carp, methaemoglobin made up 38.32±13.30%. Erythrocytes in carp exposed to nitrite showed qualitative changes. Compared with the control group C, group E1 carp showed a significantly higher number (P<0.05) of elongated erythrocytes, with the nucleus located at one cell pole (0.519±0.388 TL^?1). All erythrocytes of group E1 carp had remarkably clear cytoplasms compared with the cytoplasm in the control group C. The biochemical values found were comparable with those found in controls. The main histological lesions were found in the gills of carp exposed to nitrite and consisted of hyperplasia and an elevated number of chloride cells.