Runoff water management technologies for dryland agriculture on the Loess

SUMMARY

Arid and semi-arid environments undergo periodic seasonal agricultural droughts of varying extents and duration, erratic and ineffective rainfall of high intensity and short duration, with high surface runoff. High efficiency water-harvesting agriculture has been routinely used in the Loess Plateau agricultural production of China over the past 10 years. Localized habitat effect and regional water resource enrichment are the theoretical basis of high efficient water-harvesting agriculture. Features of this agricultural system are described, including: water harvesting of surface runoff from roads and collection in concrete yards on plastic sheets; water storage cellar tanks for harvesting runoff to provide life-saving/critical irrigation, with devices for water lifting and conveying such as hand pumps and pipelines; feasible methods of water use for limited supplies such as drip, hole, subsoil, and super-sheet irrigation; agronomic measures of high water use efficiency; and field micro-catchment for water harvesting and conservation to increase fallow efficiency in rainy seasons. Using the stored runoff water to irrigate the mulched winter wheat and spring corn, as well as vegetables and fruit trees, significant yield increasing and water use efficiency improvements have been achieved. Plastic mulching for increasing fallow efficiency in rainy seasons and improving yield of the next winter wheat crop have been developed and demonstrated. These techniques have provided obvious benefits in terms of soil and water conservation on slope farmland in the hill regions and remarkable effects of storing water and reducing drought in the dryland farming regions have been obtained.     

内蒙古生态环境敏感性综合评价

针对内蒙古土地沙化、土壤侵蚀、土壤盐渍化和生物多样性减少等区域自然环境演变过程中出现的生态问题,采用遥感和地理信息系统技术,构建敏感性评价指标体系与评价模型,对内蒙古生态环境敏感性进行综合研究,定量揭示研究区生态环境敏感性程度和空间分布特征.结果表明:土地沙化不敏感区、极敏感区分别占研究区面积35.9%和10.1%;土地沙化敏感性等级高的区域集中分布在内蒙古辖区内主要沙漠边缘和沙地;土壤基质多为沙粒、冬春季节多大风且植被覆盖度较低是土地容易发生沙化的主要原因.土壤侵蚀轻度、中度和高度敏感区分别占研究区面积的43.9%、30.2%和19.2%;受降水空间差异影响,土壤侵蚀敏感性等级自东南向西北呈逐步下降趋势.土壤盐渍化不敏感区、极敏感区分别占研究区面积的57.6%和14.6%,盐渍化明显地区主要分布在内蒙古西北部和东部;蒸发量远大于降水量,人类活动影响较明显,是土壤盐渍化高发的主要原因.生境不敏感、高度和极敏感区分别占研究区面积的30.5%、25.1%和10.6%,敏感性等级高的区域主要分布在大小兴安岭地区;这些区域水热条件相对较好,植被覆盖度高,物种数量较为丰富,是生物多样性重点保护区域.综合生态环境高度和极敏感区分别占研究区面积的27.9%和9.6%;敏感性等级高的区域位于内蒙古中北部,等级较低的区域位于内蒙古西北、东北和东南部.     

牡丹江中游底栖动物分布及其与栖境因子的关系

2013年秋季对牡丹江中游的3条河流(牡丹江、蛤蟆河、卧龙溪)150km河段进行大型底栖动物野外采样,共采集到大型底栖动物18种,隶属于3门5纲11目16科,其中昆虫纲(Insecta)、腹足纲(Gastropoda)和寡毛纲(Oligochaeta)物种居多.通过典范对应分析(CCA),研究大型底栖动物群落结构与主要的栖息地环境因子之间的相关关系,并通过香农-威纳(Shannon-Wiener)指数等生物多样性指数分析评价河流等级对物种多样性的影响.研究表明,流速、溶解氧、底质中的砾石含量是牡丹江中游影响大型底栖动物分布的关键栖息地环境因子,河流等级对底栖动物群落结构有一定影响,牡丹江干流底栖动物物种多样性高于支流,平均生物密度低于支流,且河流间等级差距越大,差异越显著.     

太湖流域河流及溪流大型底栖动物群落结构及影响因素

2012年10月对太湖流域93个样点大型底栖动物进行调查,分析西部丘陵水生态功能区和东部平原水生态功能区底栖动物群落结构及其与环境因子的关系.共采集到底栖动物104种,隶属4门8纲19目46科85属.各样点的底栖动物总密度差别很大,介于1.33~39080ind./m2.西部丘陵区的物种丰富度、物种多样性均高于东部平原区.东部平原区的优势种主要为铜锈环棱螺和霍甫水丝蚓等耐污种,而西部丘陵区的优势种中包括清洁种(毛翅目和蜉蝣目幼虫).相似性分析结果表明2个生态区底栖动物群落具有显著差异,铜锈环棱螺、霍甫水丝蚓、锯齿新米虾、大沼螺、苏氏尾鳃蚓等是造成2生态区之间群落结构差异的主要原因.典范对应分析结果表明影响底栖动物群落结构的主要因素为栖境多样性、营养状态及底质异质性.Goodnight-Whitley指数和BPI指数评价结果表明西部丘陵区整体处于轻污染状态,而东部平原区大部分采样点处于轻污染状态和中污染状态,部分采样点处于重污染状态.     

Evaluation and application of a three-dimensional water quality model in a shallow lake with complex morphometry

Fundamental hydrodynamic and ecological processes of a lake or reservoir could be adequately depicted by one-dimensional (1D) numerical simulation models. Whereas, lakes with significant horizontal water quality and hydrodynamic gradients due to their complex morphometry, inflow or water level fluctuations require a three-dimensional (3D) hydrodynamics and ecological analyses to accurately simulate their temporal and spatial dynamics. In this study, we applied a 3D hydrodynamic model (ELCOM) coupled with an ecological model (CAEDYM) to simulate water quality parameters in three bays of the morphologically complex Lake Minnetonka. A considerable effort was made in setting up the model and a systematic parameterization approach was adopted to estimate the value of parameters based on their published values. Model calibration covered the entire length of the simulation periods from March 29 to October 20, 2000. Sensitivity analysis identified the top parameters with the largest contributions to the sensitivity of model results. The model was next verified with the same setup and parameter values for the period of April 25 to October 10, 2005 against field data. Spatial and temporal dynamics were well simulated and model output results of water temperature (T), dissolved oxygen (DO), total phosphorus (TP) and one group of algae (Cyanobacteria) represented as chlorophyll a (Chla) compared well with an extensive field data in the bays. The results show that the use of the model along with an accurate bathymetry, a systematic calibration and corroboration (verification) process will help to analyze the hydrodynamics and geochemical processes of the morphologically complex Lake Minnetonka. An example of an ecological application of the model for Lake Minnetonka is presented by examining the effect of spatial heterogeneity on coolwater fish habitat analysis in 3D and under a scenario where horizontal spatial heterogeneity was eliminated (1D). Both analyses captured seasonal fish habitat changes and the total seasonal averages differed moderately. However, the 1D analysis did not capture local and short duration variabilities and missed suitable fish habitat variations of as much as 20%. The experiment highlighted the need for a 3D analysis in depicting ecological hot spots such as unsuitable fish habitats in Lake Minnetonka.     

Spatial memory, habitat auto-facilitation and the emergence of fractal home range patterns

Animals interact with their habitat in a manner which involves both negative and positive feedback mechanisms. We apply a specific modeling approach, “multi-scaled random walk”, for the scenario where a spatially explicit positive feedback process emerges from a combination of a spatial memory-dependent tendency to return to familiar patches and a consequently objective or subjective improvement of the quality of these patches (habitat auto-facilitation). In addition to the potential for local resource improvement from physically altering a patch, primarily known from the ecology of grazing ungulates, auto-facilitation from site fidelity may also embed more subtle subjective, individual-specific advantages from patch familiarity. Under the condition of resource superabundance, fitness gain from intra-home range patch fidelity creates a self-reinforcing use of the preferred patches on expense of a broader foraging in a priori equally favorable patches. Through this process, our simulations show that a spatially fractal dispersion of accumulated locations of the individual will emerge under the given model assumptions. Based on a conjecture that intra-home range patch fidelity depends on spatial memory we apply the multi-scaled random walk model to construct a spatially explicit habitat suitability parameter H_ij, which quantifies the dispersion of the generally most constraining resource from the individual's perspective. An intra-home range set of observed H-scores, H_obs, can then be estimated from a simple 2-scale calculation that is derived from the local dispersion of fixes. We show how the spatially explicit habitat utilization index H_obs not necessarily correlates positively with the local density fluctuations of fixes. The H-index solves some well-known problems from using the pattern of local densities of telemetry fixes - the classic utilization distribution - as a proxy variable for relative intra-home range habitat quality and resource selection. A pilot study on a set of telemetry fixes collected from a herd of free-ranging domestic sheep with overlapping summer home ranges illustrates how the H-index may be estimated and interpreted as a first-level approach towards a more extensive analysis of intra-home range habitat resource availability and patch preferences. Spatial memory in combination with site fidelity requires a modeling framework that explicitly describes the property of positive feedback mechanism under auto-facilitation in a spatio-temporally explicit manner.     

津河水系的修复对天津城市生态环境的影响

针对天津城市生态环境特点和背方城市大气污染现状,探讨了津河水系的修复对改善城市环境质量,丰富城市景观以及修复城市生态环境的重要意义。     

Promoting Large,Compact Mature Forest Patches in Harvest Scheduling Models

Spatially explicit harvest scheduling models that can promote the development of dynamic mature forest patches have been proposed in the past. This paper introduces a formulation that extends these models by allowing the total perimeter of the patches to be constrained or minimized. Test run results suggest that the proposed model can produce solutions with fewer, larger, and more compact patches. In addition, patches are more likely to be temporally connected with this formulation. Methods for identifying the tradeoffs between the net present value of the forest and the size and perimeter of the evolving patches are demonstrated for a hypothetical forest.     

近40 a秦岭生境质量时空变化特征及驱动机制

运用InVEST模型,研究秦岭生境质量时空变化及驱动机制,以期为秦岭生态文明建设与秦岭区域可持续发展提供理论依据。结果表明：秦岭土地利用方式以林地和草地为主,主要分布于中、西部,耕地与建设用地主要分布在东、南部。人类对秦岭干扰程度在2000年后开始增加,土地利用变幅超过总面积的2%。1980年、1990年、2000年、2010年、2020年,秦岭的平均生境质量（范围0—?1）分别为0.7592、0.7594、0.7586、0.7585、0.7617,均处于“较高”等级。空间分布上,秦岭生境质量中、西部等级高,而东、南部等级低。在像元尺度上,秦岭生境质量较为稳定,显著变化的区域面积仅为2.74%。显著升高的区域主要集中在西南部略阳、勉县等区县,显著降低的区域主要集中在东部的洛南、商州等区县。秦岭的生境质量表现出显著的空间集聚特征,21世纪后,秦岭高质量生境集聚区域面积扩张,低质量的生境集聚区域面积降低。土地利用程度是影响秦岭生境质量最大的驱动因子,与之呈现显著的负相关关系,且影响范围分布于全域。秦岭生境质量的降低源于人类活动引起生境威胁源——建设用地与耕地的扩张,而生境质量的升高可能源于...     

Mapping Stream Habitats with a Global Positioning System: Accuracy,Precision, and Comparison with Traditional Methods

We tested the precision and accuracy of the Trimble GeoXT™ global positioning system (GPS) handheld receiver on point and area features and compared estimates of stream habitat dimensions (e.g., lengths and areas of riffles and pools) that were made in three different Oklahoma streams using the GPS receiver and a tape measure. The precision of differentially corrected GPS (DGPS) points was not affected by the number of GPS position fixes (i.e., geographic location estimates) averaged per DGPS point. Horizontal error of points ranged from 0.03 to 2.77 m and did not differ with the number of position fixes per point. The error of area measurements ranged from 0.1% to 110.1% but decreased as the area increased. Again, error was independent of the number of position fixes averaged per polygon corner. The estimates of habitat lengths, widths, and areas did not differ when measured using two methods of data collection (GPS and a tape measure), nor did the differences among methods change at three stream sites with contrasting morphologies. Measuring features with a GPS receiver was up to 3.3 times faster on average than using a tape measure, although signal interference from high streambanks or overhanging vegetation occasionally limited satellite signal availability and prolonged measurements with a GPS receiver. There were also no differences in precision of habitat dimensions when mapped using a continuous versus a position fix average GPS data collection method. Despite there being some disadvantages to using the GPS in stream habitat studies, measuring stream habitats with a GPS resulted in spatially referenced data that allowed the assessment of relative habitat position and changes in habitats over time, and was often faster than using a tape measure. For most spatial scales of interest, the precision and accuracy of DGPS data are adequate and have logistical advantages when compared to traditional methods of measurement.