伊犁河谷土壤含盐量空间变异和格局分析

基于区域变量理论,在GPS和GIS技术支持下,通过地统计学的半变异函数和Kriging空间插值,以察布查尔县为例,定量分析伊犁河谷不同层次土壤盐分的空间异质性.结果表明:0～20 cm、20～40 cm、60～80 cm层土壤盐分的半变异函数符合球状模型,40～60 cm层符合高斯模型.不同层次土壤盐分之间的空间自相关...     

Optimizing reserve expansion for disjunct populations of San Joaquin kit fox

Expanding habitat protection is a common strategy for species conservation. We present a model to optimize the expansion of reserves for disjunct populations of an endangered species. The objective is to maximize the expected number of surviving populations subject to budget and habitat constraints. The model accounts for benefits of reserve expansion in terms of likelihood of persistence of each population and monetary cost. Solving the model with incrementally higher budgets helps prioritize sites for expansion and produces a cost curve showing funds required for incremental increases in the objective. We applied the model to the problem of allocating funds among eight reserves for the endangered San Joaquin kit fox (Vulpes macrotis mutica) in California, USA. The priorities for reserve expansion were related to land cost and amount of already-protected habitat at each site. Western Kern and Ciervo-Panoche sites received highest priority because land costs were low and moderate amounts of already-protected habitat resulted in large reductions in extinction risk for small increments of habitat protection. The sensitivity analysis focused on the impacts of kit fox reproductive success and home range in non-native grassland sites. If grassland habitat is lower quality than brushland habitat resulting in higher annual variation in reproductive success or larger home ranges, then protecting habitat at the best grassland site (Ciervo-Panoche) is not cost-efficient relative to shrubland sites (Western Kern, Antelope Plain, Carrizo Plain). Finally, results suggested that lowest priority should be given to three relatively high-cost grassland sites (Camp Roberts, Contra Costa, and Western Madera) because protecting habitat at those sites would be expensive and have little effect on the expected number of surviving kit fox populations.     

花江峡谷示范区主要经济植物病虫害及防治对策

经过野外调查与初步鉴定整理，花江峡谷喀斯特石漠化综合防治技术示范区，花椒病虫害26种，金银花病虫害3种，石榴病虫害10种，砂仁病虫害1种，葡萄病虫害3种，对主要病虫害提出相应的防治对策。     

Using occurrence records to model historic distributions and estimate habitat losses for two psammophilic lizards

Estimating historic distributions of species is a critical step in evaluating current levels of habitat loss, evaluating sites for potential restoration and reintroductions, and for conservation planning at a landscape scale. However historic distributions can be difficult to estimate objectively because substantial habitat changes may have occurred prior to comprehensive surveys. As a means to address this question, we evaluated a novel approach by creating spatial niche models for two species of psammophilic lizards. Using a partitioned Mahalanobis D² analysis and abiotic variables that were independent of anthropogenic change, we created niche models for the federally threatened Coachella Valley fringe-toed lizard (Uma inornata) and for the flat-tailed horned lizard (Phrynosoma mcallii). The niche models estimated that within the Coachella Valley there were originally 32,164 ha of potential habitat for the fringe-toed lizard and 33,502 ha of potential habitat for the horned lizard. After screening these estimates of historic habitat for current conditions that would render that potential habitat unsuitable, we calculated a 91-95% loss of potential habitat for the fringe-toed lizard and an 83-92% loss for the horned lizard. Unlike the fringe-toed lizard, the horned lizard also occurs outside the Coachella Valley. Conducting a similar analysis throughout its range would provide an objective estimate of the total habitat loss experienced by this species. This information could be used to address whether granting it federal or state protection is warranted. For species whose distributions can be modeled with abiotic variables such as soils, elevation, topography, and climate, this approach may have broad applications for resolving questions regarding their current levels of habitat loss and regional conservation planning.     

Recent changes in landscape structure and function in a mediterranean region of SW Spain (1950–1984)

Recent economic development has altered landscape structure and function of a mediterranean region in Southwestern Spain. Intensive agricultural systems have concentrated in the more fertile areas, while marginal ones have been abandoned. As a result, landscape structure has changed. Consequences of this structural change on landscape processes are discussed.     

Role of root-hairs and hyphae in adhesion of sand particles

The aggregation process in sandy soils depends on biological activity. We reported here results obtained from one sample time of: (a) adhesion of sand particles by root hairs and fungal hyphae, examined on root sections of four plant species (amaranth, Amaranthus hypochondriacus L.; Bermuda grass, Cynodon dactylon L.; maize, Zea mays L. and sunflower, Helianthus annuus L.) grown at field for 3 months; (b) root-adhering soil (RAS), root biomass (RB), and dry and water stable-aggregate fractions obtained from root:soil monoliths; and (c) arbuscular mycorrhizal colonization. Microscope observations on fine roots (<1 mm) showed that root hairs and hyphae contributed simultaneously, but not in the same proportion, to enmeshment of sand particles (20-150 μm). Hyphae contribution was considerably fewer than that of root-hairs. Maize and Bermuda grass had a higher root-hair density but a lower amount of external hyphae than those of amaranth and sunflower. Root-hairs of Bermuda grass and maize held approximately three times more sand particles than those of amaranth and sunflower (20 and 7 mm⁻¹ of root section, respectively). These results were consistent with the higher RAS:RB ratio of Bermuda grass and maize (302 and 257, respectively), than that of amaranth and sunflower (89 and 159). Intensity of mycorrhizal colonization in the whole root system was higher in maize, Bermuda grass and sunflower (range of 22.7-25%) as compared to that of amaranth (6.8%). A. hypochondriacus, considered as a non-mycorrhizal plant species, showed typical structures (vesicles, hyphae and arbuscules) in the root system. Results emphasized the preponderant role of root hairs (of grasses and dicotyledon species) in the process of soil adhesion by roots under sandy conditions (pumice and feldspath particles) and semi-arid climate.     

建设经济开发区应重视水土保持

建设经济开发区应重视水土保持刘顺勤（陕西省榆林地区水土保持监督总站，７１９０００）近年来，按照市场经济的指导思想，结合区内自然资源的开发利用，区域经济开发区在我区悄然兴起。据调查，目前全区已开发和准备开发的经济开发区１５个，其中县级以上经济开发区９个...     

泰安市小流域综合治理中的两条有效途径

泰安市小流域综合治理中的两条有效途径于洪太，谢厚国（山东省泰安市水土保持科学研究所，２７１０００）泰安市位于鲁中山区，山丘面积占总面积的６７％。由于山高石头多、水土流失严重，长期以来农业产量低而不稳，群众生活非常困难。党的十一届三中全会后，农村经济得...     

雅江河谷防沙治沙生态工程实施年限对沙地持水性能的影响

为探究雅鲁藏布江(下称"雅江")河谷阶地2种类型防沙治沙生态工程(砂生槐灌木林、杨树人工林)实施对沙地持水性能的影响,测定了该区6,12,30年生态工程样地0—30 cm土层沙地持水性能和土壤理化性质,采用模糊数学法计算了土壤质量指数,分析了沙地持水性能的影响因素,并采用多元逐步回归法确定了主要影响因素。结果表明:(1)研究区0—10 cm土层砂生槐和杨树人工林土壤饱和持水量、毛管持水量和田间持水量指标从6～30年增幅分别为5.81%～9.19%和51.47%～71.48%,杨树人工林上述持水量指标是砂生槐的1.02～1.60倍。(2)杨树人工林促进沙地0—10 cm土层机械组成、容重、孔隙度等结构变化和有机质、全氮等养分含量提高均优于砂生槐。随实施年限变化,砂生槐上述土壤指标变化整体为12年最好,杨树人工林则依次为30年10年6年。(3)2种生态工程0—30 cm土层土壤综合质量指数平均值随年限的增加呈增加趋势。相关分析和多元逐步回归分析结果表明,沙地持水性能与沙地机械组成、容重、孔隙度、有机质、全氮和全磷均呈极显著相关,其主要影响因素为毛管孔隙度、全氮和极细砂。综合可知,杨树人工林作为当地引进乔木种,其对沙地持水性能提升效果及持续作用均优于乡土种灌木砂生槐,能够很好地促进沙地恢复。研究结果可为认识区域沙地生态水文功能变化和生态工程建设提供数据参考。