Spatial heterogeneity distribution of soil total nitrogen and total phosphorus in the Yaoxiang watershed in a hilly area of northern China based on geographic information system and geostatistics

Soil total nitrogen (STN) and total phosphorus (STP) are important indicators of soil nutrients and the important indexes of soil fertility and soil quality evaluation. Using geographic information system (GIS) and geostatistics, the spatial heterogeneity distribution of STN and STP in the Yaoxiang watershed in a hilly area of northern China was studied. The results showed that: (1) The STN and STP contents showed a declining trend with the increase in soil depth; the variation coefficients (C_v) of STN and STP in the 0‐ to 10‐cm soil layer (42.25% and 14.77%, respectively) were higher than in the 10‐ to 30‐cm soil layer (28.77% and 11.60%, respectively). Moreover, the C_v of STN was higher than that of STP. (2) The maximum C₀/(C₀ + C₁) of STN and STP in the soil layers was less than 25%, this indicated that a strong spatial distribution autocorrelation existed for STN and STP; and the STP showed higher intensity and more stable variation than the STN. (3) From the correlation analysis, we concluded that the topographic indexes such as elevation and slope direction all influenced the spatial distribution of STN and STP (correlation coefficients were 0.688 and 0.518, respectively). (4) The overall distribution of STN and STP in the Yaoxiang watershed decreased from the northwest to the southeast. This variation trend was similar to the watershed DEM trend and was significantly influenced by vegetation and topographic factors. These results revealed the spatial heterogeneity distribution of STN and STP, and addressed the influences of forest vegetation coverage, elevation, and other topographic factors on the spatial distribution of STN and STP at the watershed scale.     

Characteristics of softwater streams in Rhode Island. III. Distribution of macrophytic vegetation in a small drainage basin

The Wood River watershed, a small well-defined drainage basin in Rhode Island was monitored seasonally for all macrophytic vegetation and various physical variables. Twenty-four segments, 20 m in length were sampled. Mean stream depth, width and current velocity increased by 3 to 8 fold from 1st- to 4th-order segments. Light penetration was positively correlated with the above variables (p < 0.05) and increased by 11 fold from the headwaters to the mouth during September when the riparian canopy was maximum. 74 subgeneric taxa of macrophytes were collected in the Wood River basin, 36% algae, 13% bryophytes, 4% vascular cryptograms and 45% angiosperms. The highest diversity occurred in the 4th-order segments throughout the year. Species numbers were positively correlated with depth, width and light penetration (p < 0.05). Vascular plants dominated all orders, but their proportion doubled from 1st- to 4th-order streams. Macrophyte cover was twice as high in the 4th-order segments in June and September as in the other orders. Macrophyte abundance was positively correlated to light penetration and negatively correlated to the ratio of nonvascular: vascular plants (p < 0.05). Two distinct clusters were found for the predominant species. The first cluster contained mostly large angiosperms, which were rooted in sediments, while the second cluster was composed of small epilithic algae and bryophytes. The moss, Fontinalis antipyretica, was the most frequent species, occurring in 51% of the samples and in all 4 orders throughout the year.     

Atmospheric deposition and solute export in giant sequoia — mixed conifer watersheds in the Sierra Nevada,California

Atmospheric depostion and stream discharge and solutes were measured for three years (September 1984 — August 1987) in two mixed conifer watersheds in Sequoia National Park, in the southern Sierra Nevada of California. The Log Creek watershed (50 ha, 2067–2397 m elev.) is drained by a perennial stream, while Tharp's Creek watershed (13 ha, 2067–2255 m elev.) contains an intermittent stream. Dominant trees in the area include Abies concolor (white fir), Sequoiadendron giganteum (giant sequoia), A. magnifica (red fir), and Pinus lambertiana (sugar pine). Bedrock is predominantly granite and granodiorite, and the soils are mostly Pachic Xerumbrepts. Over the three year period, sulfate (SO₄ ^2–), nitrate (NO₃ ^–), and chloride (Cl^–1) were the major anions in bulk precipitation with volume-weighted average concentrations of 12.6, 12.3 and 10.0 eq/1, respectively. Annual inputs of NO₃-N, NH₄-N and SO₄-S from wet deposition were about 60 to 75% of those reported from bulk deposition collectors. Discharge from the two watersheds occurs primarily during spring snowmelt. Solute exports from Log and Tharp's Creeks were dominated by HCO₃ ^–, Ca²⁺ and Na⁺, while H⁺, NO₃ ^–, NH₄ ⁺ and PO₄ ^3– outputs were relatively small. Solute concentrations were weakly correlated with instantaneous stream flow for all solutes (r² <0.2) except HCO₃ ^– (Log Cr. r² = 0.72; Tharp's Cr. r² = 0.38), Na⁺ (Log Cr. r² = 0.56; Tharp's Cr. r² = 0.47), and silicate (Log Cr. r² = 0.71; Tharp's Cr. r² = 0.49). Mean annual atmospheric contributions of NO₃-N (1.6 kg ha^–1), NH₄-N (1.7 kg ha^–1), and SO₄-S (1.8 kg ha^–1), which are associated with acidic deposition, greatly exceed hydrologic losses. Annual watershed yields (expressed as eq ha^–1) of HCO₃ ^– exceeded by factors of 2.5 to 37 the annual atmospheric deposition of H⁺.     

Stream chemistry and hydrologic pathways during snowmelt in a small watershed adjacent Lake Superior

In regions with airborne contaminants and large snowpacks, there is concern over the impact that snowmelt chemical pulses — periods of sharp increase in meltwater solute concentration — could have on aquatic resources during spring runoff. A major variable in determining such an effect is the flow path of snowmelt solutes to the stream or lake. From December 1988, to late April 1989, the quality and quantity of precipitation, snowmelt, soil solution and streamwater were measured in a 176-ha gauged watershed on the south shore of Lake Superior. The main objectives were to (1) examine the change in flow path meltwaters take to the stream during distinct winter and spring hydrologic periods, (2) quantify ecosystem-level ion budgets prior to, during, and following snowmelt, and (3) examine if streamwater chemistry might be a sensitive indicator of change in ecosystem flow paths. Prior to peak snowmelt, groundwater made up 80% of stream discharge. During peak snowmelt, the groundwater level rose to the soil surface resulting in lateral water movement through near-surface macropores and as overland flow. Near the end of snowmelt, melt-waters exerted a piston action on deeper soil solution again increasing its relative contribution to streamwater discharge. Net groundwater drawdown during the study resulted in streamwater discharge about equal to precipitation inputs. Unfrozen soils and brief mid-winter thaws resulted in steady snowmelt throughout early and mid-winter. The snowpack lost > 50% of most ions prior to the period of major snowmelt and high stream discharge in late March and early April. Snowmelt and streamwater NO₃ ^– and NH₄ pulses occurred before the period of overland flow and peak streamwater discharge (April 4–24). During overland flow, stream discharge of total N, P, DOC, and AI peaked. Nutrient budgets computed for distinct hydrologic periods were much more helpful in explaining ecosystem pathways and processes than were changes in solute concentration. For the study period, watershed base cation (C_B) discharge was 23 times input and SO₄ ^2– discharge exceeded input by 42%. H⁺ was the most strongly conserved ion with output < 0.2% of input. Also conserved were NH₄ ⁺ with only 1.4% of input leaving the ecosystem and NO₃ ^– with output equal to 9.4% of input.     

Processes regulating temporal and longitudinal variations in the chemistry of a low-order woodland stream in the Adirondack region of New York

Watershed processes influence the acid neutralizing capacity of surface waters by mediating changes in concentration of ionic solutes. Acidification of surface waters by atmospheric deposition of mineral acids and the extent to which ecosystem transformations neutralize this acidity are of particular concern. Seasonal variations in flow paths of water through soil and biological processes result in short-term changes in chemistry that may be critical to surface water ecology. In this study, we assessed longitudinal and temporal variations in the chemistry of a low-order stream, Pancake-Hall Creek, located in the west-central Adirondack region of New York. By quantifying changes in ionic solute concentration (e.g. Ca²⁺, Al^a+, SO ₄ ^2– , NO ₃ ^– ) we were able to evaluate processes responsible for short-term fluctuations in acid/base chemistry.In the headwater sites, stream water was acidic; changes in pH, acid neutralizing capacity (ANC) and Al were primarily due to seasonal variations in basic cation and NO ₃ ^– concentrations. At the downstream sites, water migrated through a large beaver impoundment and thick till resulting in higher pH, acid neutralizing capacity and basic cation concentrations, and lower concentrations of Al. Neutralization of acidity was particularly evident during the low flow summer period and coincided with retention of SO ₄ ^2– in the beaver impoundment. During the high flow non-summer (October to June) period, depressed pH and ANC, and elevated Al concentrations were observed in the downstream sites. Acidic conditions during the non-summer period were not due to the oxidation of reduced sulfur deposits (e.g. SO ₄ ^2– events) but rather the resumption of conservative SO ₄ ^2– transport through the beaver impoundment (e.g. minimal SO ₄ ^2– retention) coupled with increases in NO ₃ ^– .     

流域生态服务价值供给的补偿标准评估——以渭河流域上游为例

十九大报告明确提出,健全河流湖泊休养生息制度,建立多元化的生态补偿机制,而准确核算流域生态服务价值供给的补偿标准是建立科学的流域生态补偿机制的关键要素。对于补偿标准的核算,鲜有学者从公平的视角出发,考虑补偿标准应在生态服务价值供给的基础上剔除本地区的自身消费。首先对流域生态服务供给方的供给行为与流域生态补偿标准的评估依据进行理论探讨,提出流域生态补偿标准应以生态环境价值为依据,对生态保护行为的生态外溢环境价值进行补偿;其次,在理论分析的基础上以渭河流域为例,构建当量因子模型测算渭河上游2006—2015年供给的生态服务价值,并结合水足迹法测算并剔除2006—2015年渭河上游自身消费的生态服务价值;最后,测得渭河上游应获得的补偿标准由2006年的12.82亿元上升至2015年的44.09亿元,总体呈增长趋势,说明上游为保护流域生态环境不断付出努力,不断增加对下游的剩余生态服务价值供给。     

水土保持技术对农业产业-资源系统的耦合路径分析

水土保持技术通过对农业产业-资源系统的作用过程影响系统的耦合效果,这一过程及效果成为农户选择水土保持技术的关键点。为此,运用结构方程模型,以典型流域—县南沟流域为对象,通过对2017年130户农户调研资料的分析,揭示其作用过程和耦合路径,结果表明:水土保持技术与生态环境、农业资源、农业产业形成了一个新的耦合系统,水土保持技术对生态环境的改良和农业资源量的增加具有促进作用,对农业产业的发展具有抑制作用。但其(现阶段)作用强度较弱,(水土保持技术对三者的路径系数分别为0.13、0.08、-0.02);这是由于县南沟流域基本完成了规模化治理,故水土保持技术对农业产业-资源系统的影响的弱强度是基于水土流失治理及治理措施有效发挥基础之上的弱强度,同时隐含了现有的水土保持技术体系已不能完全满足新时代背景下生态文明建设与经济发展的需求,需要围绕水土保持内涵经营过程,以生态功能的提升为主线,筛选、集成、研发水土保持技术,形成可适化水土保持技术体系。     

Integrated assessment and changes of ecological environment in the Daning River Watershed

Based on Remote Sensing (RS), Geographical Information Systems (GIS), and the Spatial Principal Component Analysis (SPCA) method, the integrated assessment and changes in the ecological environment of Daning River Watershed are studied in this paper. The watershed is located in the Three Gorge Area in China. The result of the integrated assessment showed that level 9 had the biggest proportion in the year 1990, which was about 40%. In the year 2000, however, there were no levels with a proportion significantly bigger than the others. By comparing the assessment results in 1990 and 2000, it is discovered that the ecological environment in Daning River Watershed in 1990 was better than that in 2000. __________ Translated from Journal of Beijing Normal University (Natural Science), 2006, 42(2): 200–203 [译自: 北京师范大学学报 (自然科学版)]     

Land use/cover change and its drivers: a case in the watershed of Lake Kasumigaura, Japan

Land use/land cover (LULC) changes in the watershed (2,157 km²) of Lake Kasumigaura during 1979–1996 (Period-1: 1979–1990, Period-2: 1990–1996) were analyzed, and their socio-economic and biophysical drivers were compared using time-series, high-quality GIS datasets in order to examine the characteristics of a model forecasting the future LULC. The changes occurred over an area of more than 90 km² during the overall period at changing rates of 0.22% year⁻¹ in Period-1 and 0.25% year⁻¹ in Period-2. Forestland decreased most in both periods at changing rates of 0.45% year⁻¹ in Period-1 and 0.61% year⁻¹ in Period-2. However, predominant changing patterns differed, i.e., from forest to golf course in Period-1 and from forest to artificial field in Period-2. Particularly in Period-2, a significant LULC change was observed in an area of high population increase on the edge of an already high-population area. Relationships examined among LULC change, population, and rate of population change suggested that the urbanized area was highly resistant to LULC change, and that such change was less frequent in areas of population decline. Statistical analyses indicated that the most influential drivers for total LULC changes were population in Period-1 and distance from the Tokyo Station in Period-2. Since the change potentials differed between the periods, we could not assume a stationary process for the corresponding drivers. Somewhat low S values (indices for demonstrability) show that LULC changes in the watershed of Lake Kasumigaura occurred rather randomly, probably resulting in fragmentation of the landscape.