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71.
Dwindling resources and fragmentation of landscapes around parks: wetlands and forest patches around Kibale National Park,Uganda 总被引:2,自引:0,他引:2
Landscapes surrounding parks in most of the developing world, while still containing considerable biodiversity, also have
rapidly growing human populations and associated agricultural development. Since the establishment of Kibale National Park
first as a Crown Forest Reserve in 1932 and later as a park in 1993 in western Uganda, most access and resource extraction
has been prohibited. The park has become nearly a complete island of forested land cover surrounded by intensive small-scale
agriculture and some large-scale tea plantations, along with a network of wetland and forest patches. As the population grows
outside the park and land becomes more scarce, remaining forests and wetlands are being used more intensively for material
resources (e.g., fuelwood, building poles) and converted to other land uses (e.g., pasture, agriculture). This study uses
both discrete and continuous data analyses of satellite imagery to examine these diminishing resource bases at the landscape
level placing the results within the social context of conservation and parks. Findings reveal that the park boundaries have
remained fairly intact whereas, the landscape surrounding the park has become increasingly fragmented. From a landscape perspective,
while the park has indeed maintained its forest cover, it has become increasingly islandized with wetland and forest patches
in the surrounding landscape becoming smaller in number and size. Those that have survived are now more isolated and even
lower productivity than in 1984, which may be a precursor to their eventual loss in this landscape. 相似文献
72.
利用1988—2016年共541幅Landsat 5 TM和Landsat 8 OLI影像,计算了极旱荒漠区中西土沟和渥洼池湿地植被(以芦苇为主)的归一化植被指数(NDVI),分别从NDVI,湿地植被面积和平均NDVI这3个方面对湿地植被特征进行分析,对敦煌阳关国家级自然保护区(以下称阳关保护区)内的渥洼池和西土沟湿地植被进行植被覆盖度估算,判断其变化。根据谷歌影像和现地调查,确定NDVI >0.1是识别西土沟和渥洼池湿地植被的最佳阈值,通过对保护区湿地植被的统计计算,研究其变化趋势。研究发现,渥洼池和西土沟的湿地植被都有明显的增加趋势。 相似文献
73.
Louise Askaer Ronnie N. Glud Michael Kühl Frants R. Lauritsen 《Soil biology & biochemistry》2010,42(12):2254-2265
The importance of soil heterogeneity for methane emission from a wetland soil is assessed by in situ point measurements of depth-specific O2 and CH4 concentrations and simultaneous soil CH4 fluxes at contrasting water levels. Profile measurements, and associated assumptions in their interpretation, were validated in a controlled mesocosm drainage and saturation experiment applying planar O2 optodes and membrane inlet mass spectrometry. Results show that peat soil is heterogeneous containing dynamic macropore systems created by both macrofauna and flora, which facilitate preferential flow of water, O2 and CH4 and vary temporally with changes in the moisture regime. The O2 content above the water table after drainage varied horizontally from 0 to 100% air saturation within few mm. Oxic zones were observed below the water level and anoxic zones were observed in layers above the water level in periods up to days after changes in the water level. This study shows that although water table position is a competent proxy of soil CH4 fluxes at larger spatio-temporal scales, it becomes inadequate at higher spatial resolution, i.e. at the scale of the soil pedon and below. High resolution O2 measurements using planar O2 optodes have great potential to enhance our understanding of the effect of the water table position on O2 dynamics on scales of several cm to mm in wetland soils. 相似文献
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75.
以扎龙自然湿地典型的芦苇沼泽生境为研究对象,分析了土壤养分与土壤微生物特性在不同土层(0~15 cm,15~30 cm)中的分布规律.结果表明,随着土层深度的增大,土壤有机质、全N、全P、水解性氮、速效钾、细菌、真菌、放线菌以及微生物量碳和氮质量分数、脲酶、酸性磷酸酶、碱性磷酸酶、过氧化氢酶、β-葡萄糖苷酶的活性均显著... 相似文献
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77.
Land usage is a strong determinant of soil microbial community composition and activity, which in turn determine organic matter decomposition rates and decomposition products in soils. Microbial communities in permanently flooded wetlands, such as those created by wetland restoration on Sacramento-San Joaquin Delta islands in California, function under restricted aeration conditions that result in increasing anaerobiosis with depth. It was hypothesized that the change from agricultural management to permanently flooded wetland would alter microbial community composition, increase the amount and reactivity of dissolved organic carbon (DOC) compounds in Delta waters; and have a predominant impact on microbial communities as compared with the effects of other environmental factors including soil type and agricultural management. Based on phospholipid fatty acid (PLFA) analysis, active microbial communities of the restored wetlands were changed significantly from those of the agricultural fields, and wetland microbial communities varied widely with soil depth. The relative abundance of monounsaturated fatty acids decreased with increasing soil depth in both wetland and agricultural profiles, whereas branched fatty acids were relatively more abundant at all soil depths in wetlands as compared to agricultural fields. Decomposition conditions were linked to DOC quantity and quality using fatty acid functional groups to conclude that restricted aeration conditions found in the wetlands were strongly related to production of reactive carbon compounds. But current vegetation may have had an equally important role in determining DOC quality in restored wetlands. In a larger scale analysis, that included data from wetland and agricultural sites on Delta islands and data from two previous studies from the Sacramento Valley, an aeration gradient was defined as the predominant determinant of active microbial communities across soil types and land usage. 相似文献
78.
为了探明杭州湾湿地植物碱蓬Suaedaeglauc0,南方碱蓬Suaed austrdis,芦苇Phragmites australis和野艾蒿Artemisia lavandulacfolia等各自生境土壤盐分高低是否和种子在盐分胁迫下的萌发能力相一致。试验比较了它们所在生境的土壤含盐量、pH值及含水率,测定了4种植物种子在不同质量浓度氯化钠(NaCl)(0~50g·L-1)溶液处理下的萌发率,并分析了土壤含盐量、pH值和含水率和20g·L-1氯化钠溶液处理的种子萌发率之间的相关性。结果表明,各物种生境土壤含盐量顺序是南方碱蓬〉碱蓬〉芦苇〉野艾蒿;土壤pH值为芦苇〉野艾蒿〉南方碱蓬和碱蓬:土壤含水率为碱蓬〉芦苇〉南方碱蓬〉野艾蒿。氯化钠溶液处理对4种种子萌发率都有显著影响,萌发率随盐分质量浓度增加而下降:同一盐分质量浓度下.萌发率高低顺序依次是碱蓬〉南方碱蓬〉芦苇〉野艾蒿。复水后氯化钠溶液处理的种子萌发率都显著提高.但不同物种萌发率高低顺序和复水前相同。相关分析表明.土壤含盐量和不同种子在20g·L-1氯化钠胁迫下的萌发率是显著相关的。这些结果表明,土壤含盐量是限制上述4种种子萌发的重要因素:4种植物的分布是和它们各自生境的盐分高低条件和种子在盐分胁迫条件下的萌发能力相关的。图2表2参17 相似文献
79.
贵州省湿地资源现状、问题及对策 总被引:1,自引:0,他引:1
该文综述了贵州省第二次湿地资源的调查范围、区划条件及其特点,针对贵州省湿地保护中存在的问题提出了相应的对策。 相似文献
80.
In the Midwestern United States, agricultural landscapes with scattered patches of fragmented forest are common. To investigate the relationship between amphibian distributions and wetland, woodlot, and landscape characteristics, we studied the pond-breeding amphibians within a 15,450-ha plot in rural north-central Ohio. We surveyed 25 woodlots and one area of continuous riparian forest for amphibians, and each surveyed woodland contained at least one temporary wetland. We used Akaike's Information Criterion (AIC) to evaluate the effectiveness of 13 a priori models in predicting total amphibian species richness, anuran richness, caudate richness, and the presence of individual species in woodlots. We identified 13 species of amphibians within the study plot, and every woodlot contained at least one amphibian species. The most important variable in predicting total amphibian and anuran species richness was hydroperiod. For caudates, woodlot edge-to-area ratio, hydroperiod, pH, and ammonia were important characteristics in predicting species richness. Woodlots within agricultural landscapes are important refuges for amphibians. 相似文献