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典型喀斯特地区石漠化景观格局对土地利用变化的响应   总被引:2,自引:0,他引:2  
冉晨  白晓永  谭秋  罗旭玲  陈欢  习慧鹏 《生态学报》2018,38(24):8901-8910
土地利用是人类活动最基本的表现形式,探讨石漠化与土地利用变化之间的响应关系,对于石漠化治理和区域的可持续发展是非常重要的。基于贵州道真县2005年、2015年LANDSAT和石漠化数据,再利用ENVI 5.3进行监督分类,将道真县土地利用分为8种类型。通过景观格局空间分析技术和3S技术,对道真县土地利用时空演变和石漠化景观格局进行综合分析,结果表明:(1) 2005—2015年间,道真县建设用地和灌木林地面积增加,大部分灌木林地由水田和旱地转化而来,其面积增加了7.51%,建设用地增加了1.30%。(2)近10年间,研究区石漠化等级间的转移表现为轻、中、重度转化为潜在石漠化,其斑块转移面积分别为11.26、38.79、2.71 km2,表明研究区石漠化景观得到了恢复,低等级石漠化斑块面积增加,降低了原有高等级石漠化斑块的优势度。(3) 2005—2015年间道真县土地利用和石漠化景观格局,多样性指数分别下降了0.6434和2.4309,均匀度指数各减少了0.0552和0.5436,分维度指数各提高了0.0061和0.0801,蔓延度指数各增加0.1751、25.5396和聚合度指数分别增加1.8688和2.9112,景观形状指数分别减少0.9812和4.536,石漠化景观格局的变化对应土地利用景观格局指数的变化,随着人们土地利用方式的改变,石漠化也发生相应的改变。通过该研究的进行,有助于提高人们对石漠化和土地利用景观格局的认识,基于景观生态学背景对石漠化治理成效进行评估,为之后的石漠化治理工作的进行及研究提供了参考。  相似文献   
3.
我国西南喀斯特地区环境容量小、生态系统变异敏感度高、灾变承受能力低,是典型的生态环境脆弱区。土壤动物是陆地生态系统的重要组成部分,对生态系统功能和稳定性具有重要的意义。通过Meta分析研究西南喀斯特地区土壤动物群落特征,得到如下结果:本区域土壤动物隶属于5门15纲31类;中小型土壤动物平均密度6.0×10~3—1.9×10~4m~(-2);中小型土壤动物密度和类群数表现为夏秋高、冬春低,土壤动物表聚性明显;喀斯特石漠化显著降低中小型土壤动物的密度和类群数量。本研究的结果表明,我国西南喀斯特地区土壤动物类群数量较为丰富,个体密度较低但可能被低估。在今后喀斯特地区生物多样性保护和脆弱生态系统的恢复工作中,应注重土壤动物群落的相关研究。  相似文献   
4.

Aim

Cheatgrass (Bromus tectorum) is notorious for creating positive feedbacks that facilitate vegetation type conversion within sagebrush steppe ecosystems in the western United States. Similar dynamics may exist in adjacent lower montane forest. However, fire‐forest‐cheatgrass dynamics have not been examined. We used species distribution modeling to answer three questions about fire and invasibility in lower montane forests: (Q1) Does fire create more suitable habitat for cheatgrass? (Q2) If so, which site attributes are altered to increase site suitability? (Q3) Does fire increase connectivity among suitable habitat and enhance spread?

Location

Shoshone National Forest, Wyoming, USA.

Methods

We measured cheatgrass presence–absence in 93 plots within Interior Douglas‐fir (Pseudotsuga menziesii var. glauca) forests. Random Forests predicted cheatgrass distribution with and without fire using nine site attributes: elevation, slope, aspect, solar radiation, annual precipitation, maximum temperature in July, minimum temperature in January, forest canopy cover and distance to nearest trail or road. Additionally, invasion pathways and spread were mapped using Circuitscape.

Results

Cheatgrass distribution was controlled by topographic and climate variables in the absence of fire. In particular, cheatgrass was most likely to occur at low elevation along dry, south‐ and east‐facing slopes. High‐severity fire increased potential cheatgrass distribution when forest canopy cover was reduced to below 30%. This process created new invasion pathways, which enhanced cheatgrass spread when modelled in Circuitscape.

Main conclusions

Our study showed that in the absence of fire, drier south‐ and east‐facing slopes at low elevation are most susceptible to cheatgrass invasion. However, high‐severity fire increased the total area susceptible to invasion—allowing cheatgrass to expand into previously unsuitable sites within lower montane forests in the western United States. These results are important for present day management and reflect that integrating responses to disturbance in species distribution models can be critical for making predictions about dynamically changing systems.
  相似文献   
5.
栖息地退化会使环境中蜥蜴的可利用食物资源发生改变。采用剖胃法对内蒙古自治区鄂尔多斯市准格尔旗和达拉特旗地区采集的草原沙蜥样本进行了食性分析。对固定沙丘、半固定沙丘和流动沙丘三类样地中77个实胃样本的652只(套)食物进行鉴定和分析的结果表明,这些食物主要为节肢动物,分为35类,隶属3纲11目32科;也在少部分个体(4.69%)的胃容物中发现少量(1.95%)植物碎片。上述三类栖息地中,草原沙蜥对蚁科、蚜科、瓢虫科、叶蝉科和茧蜂科昆虫均有较大的捕食比例;但相比固定沙区栖息地,草原沙蜥在半固定及流动沙丘中增减的食物种类均比较多,导致草原沙蜥在流动沙区与其他两类样地之间有较大的食物相异性。从固定沙丘、半固定沙丘到流动沙丘,随栖息地荒漠化程度的增加,草原沙蜥捕食食物类群的丰富度逐步减少,辛普森优势度指数相应地下降,但营养生态位宽度、香农威纳多样性指数和皮洛均匀性指数却在流动沙丘栖息地上明显增大。这表明鄂尔多斯地区的草原沙蜥是以捕食昆虫等节肢动物为主、兼食极少量植物的杂食性动物。栖息地荒漠化所致的环境变化显著地影响草原沙蜥的食物组成,使其觅食的食物种类逐步减少。  相似文献   
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7.
Mussels, barnacles, and rockweeds often form a distinct mosaic of patches on rocky intertidal shores, and it has been suggested that these communities may represent alternative community states. One way that alternative community states can arise is if early successional events are scale-dependent, but it is not known if juvenile survivorships of mussels and barnacles are, in fact, scale-dependent. Scale-dependence of barnacles (Semibalanus balanoides (L.)) and mussels (Mytilus edulis L.) was tested in the Gulf of Maine, USA. In winter 1997, clearings of 1, 2, 4 and 8 m in diameter and uncleared controls were made in stands of the rockweed Ascophyllum nodosum (L.) Le Jolis at 12 sites spread evenly across four bays on Swan's Island, ME. Summer and fall-winter survivorship of barnacles, which recruited in spring 1997, were estimated by tracking the 1997 cohort until late winter 1998. Survivorship of mussels was estimated from following the fate of transplanted juveniles over 4 days in late August 1997. Both barnacles and mussels showed better survival in 4 and 8 m clearings than in small clearings and controls. There was also significant variation in survivorship among sites. Densities of gastropods in the clearings did not reflect survivorship patterns of barnacles and mussels. Barnacle survivorship increased in fall and winter, and in large clearings was comparable to survivorship in barnacle-dominated habitats. Mussel survivorship was low in all clearing sizes suggesting that mussel beds develop slowly.  相似文献   
8.
Changes in regional climate in the Rocky Mountains over the next 100 years are expected to have significant effects on biogeochemical cycles and hydrological processes. In particular, decreased discharge and lower stream depth during summer when ultraviolet radiation (UVR) is the highest combined with greater photo-oxidation of dissolved organic materials (DOM) will significantly increase exposure of benthic communities to UVR. Communities in many Rocky Mountain streams are simultaneously exposed to elevated metals from abandoned mines, the toxicity and bioavailability of which are also determined by DOM. We integrated field surveys of 19 streams (21 sites) along a gradient of metal contamination with microcosm and field experiments conducted in Colorado, USA, and New Zealand to investigate the influence of DOM on bioavailability of heavy metals and exposure of benthic communities to UVR. Spatial and seasonal variation in DOM were closely related to stream discharge and significantly influenced heavy metal uptake in benthic organisms. Qualitative and quantitative changes in DOM resulting from exposure to sunlight increased UV-B (290–320 nm) penetration and toxicity of heavy metals. Results of microcosm experiments showed that benthic communities from a metal-polluted stream were tolerant of metals, but were more sensitive to UV-B than communities from a reference stream. We speculate that the greater sensitivity of these communities to UV-B resulted from costs associated with metal tolerance. Exclusion of UVR from 12 separate Colorado streams and from outdoor stream microcosms in New Zealand increased the abundance of benthic organisms (mayflies, stoneflies, and caddisflies) by 18% and 54%, respectively. Our findings demonstrate the importance of considering changes in regional climate and UV-B exposure when assessing the effects of local anthropogenic stressors.  相似文献   
9.
A new species,Boechera glareosa, is described and a key is provided to separate it from its apparent closest relative,B. gunnisoniana (Rollins) W. A. Weber. Twelve transfers are made fromArabis toBoechera to bring the nomenclature of Rocky Mountain region taxa in line with current DNA data.  相似文献   
10.
The introduced mussel Mytilus galloprovincialis is progressively increasing in abundance along the south coast of South Africa. Quantitative 0.1 m2 samples were collected in the mid-zone of an indigenous Perna perna mussel bed in the 1980s prior to the arrival M. galloprovincialis (12) and in the 2000s during the M. galloprovincialis invasion (16). In addition, in situ counts of M. galloprovincialis were done on eight occasions between 1993 and 2005, and in the low- and high-zones on four occasions. In the mid-zone M. galloprovincialis was absent until 1987, its mean densities were low (< 15 individuals/0.1 m2) between 1993 and 1996, but thereafter increased steadily, peaking in 2004 (at 721 individuals/0.1 m2), before declining in 2005 (331 individuals/0.1 m2). The greatest densities of M. galloprovincialis were recorded at the high-zone (1121 individuals/0.1 m2) and the smallest in the low-zone. As M. galloprovincialis numbers increased, there was an associated, but smaller decline in P. perna numbers and the overall density of mussels increased significantly (P < 0.05). No major change was recorded in the size composition of P. perna. The density of associated fauna differed significantly (P < 0.01) between sampling dates with the lowest and highest values being recorded near the ‘beginning’ (2001) and ‘end’ (2005) of the invasion period respectively. These differences were largely due to variations in the density of barnacles, and the toothed barnacle Chthamalus dentatus appeared to be the only associated faunal species that was directly affected by the M. galloprovincialis invasion, experiencing a significantly (P ≤ 0.05), but temporary decline in density and biomass values.  相似文献   
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