Restoration and Rehabilitation of Degraded Ecosystems in Arid and Semi-Arid Lands. II. Case Studies in Southern Tunisia, Central Chile and Northern Cameroon

A model of ecosystem degradation and three possible responses to it—restoration, rehabilitation, and real-location—is applied to ongoing projects in the arid mediterranean region of southern Tunisia, the subhumid mediterranean region of central Chile, and the semiarid tropical savannas of northern Cameroon. We compare both nonhuman and human determinants of ecosystem degradation processes in these contrasted regions, as well as interventions being tested in each. A number of quantifiable “vital ecosystem attributes” are used to evaluate the effects of ecosystem degradation and the experimental responses of rehabilitation on vegetation, soils and plant-soil-water relations. We argue that attempts to rehabilitate former ecosystem structure and functioning, both above- and below ground, are the best way to conserve biodiversity and insure sustainable long-term productivity in ecosystems subjected to continuous use by people in arid and semi-arid lands of “the South.” The success of such efforts, however, depends not only on elucidating the predisturbance (or slightly disturbed) structure and function of the consciously selected “ecosystem of reference,” but also on understanding and working with the socioeconomic, technical, cultural, and historical factors that caused the degradation in the first place.     

退化生态系统的恢复与管理——兼论自然保护区在其中发挥的作用

生态系统退化与人口的增加及人类的活动有直接的关系。长期以来人类对自然生态系统的掠夺性利用造成了各类生态系统的退化,即人为原因是主要的,而自然原因是次要的。在退化生态系统的治理方面,关键要减少自然生态系统恢复演替中人为的压力,而大面积的土地可借助自然力恢复,恢复后的土地可发展成自然保护区,并开展生态旅游等非直接破坏性的活动。应充分考虑到社区的发展问题,解决人的生存出路并提高他们的生活质量,从而在根本上缓解对自然生态系统的压力。本文提出了“以地养地”并借助自然力恢复退化生态系统的模式,利用各种具体例子阐明了我们的观点。最后指出了中国古代先哲关于人与自然的关系原理至今在退化生态系统的恢复中仍然有着现实的指导意义。     

退化生态系统的恢复与管理--兼论自然保护区在其中发挥的作用

生态系统退化与人口的增加及人类的活动有直接的关系。长期以来人类对自然生态系统的掠夺性利用造成了各类生态系统的退化,即人为原因是主要的,而自然原因是次要的。在退化生态系统的治理方面,关键要减少自然生态系统恢复演替中人为的压力,而大面积的土地可借助自然力恢复,恢复后的土地可发展成自然保护区,并开展生态旅游等非直接破坏性的活动。应充分考虑到社区的发展问题,解决人的生存出路并提高他们的生活质量,从而在根本上缓解对自然生态系统的压力。本文提出了“以地养地”并借助自然力恢复退化生态系统的模式,利用各种具体例子阐明了我们的观点。最后指出了中国古代先哲关于人与自然的关系原理至今在退化生态系统的恢复中仍然有着现实的指导意义。     

干旱、半干旱区生态学学术讨论会在乌鲁木齐举行

中国生态学会主持召开的“干旱、半干旱区生态学学术讨论会”于1982年10月6日至11日在新疆维吾尔自治区乌鲁木齐市举行,参加这次学术讨论会的有来自西北五省(区)(新疆、青海、甘肃、宁夏、陕西)以及内蒙古、山西、河北、北京、沈阳、上海、南京、云南等13省(区)市的70个单位的87名代表。包括动植物生态、农、林、牧、水利、气象、环保等专业。共收到论文48篇。会议分两个阶段进行。第一阶段(6日上午至8日上午)大会学术报告。有24位代表做了报告,包括动物生态、植物生态(广义)、生态平衡、人口、农业、环境保护等方面。植物生态方面有分析生态因素对作物的影响,探讨增产途径的,如陈培元(中国科学院西北水保所)的“黄土高原半干旱地区旱地小麦水分利用效率和抗旱增产途径问题”,周电辉(甘     

鹤山退化生态系统恢复过程中土壤微生物的特性

对鹤山丘陵荒坡人工植被土壤生物特性进行了研究,结果表明鹤山人工植被中土壤微生物的数量以马占相思林较高,为6.164×106g-1drysoil,接近村边次生自然林(6.323×106g-1drysoil);其次是果园和红荷木林,分别为5.115×106和4.083×106g-1drysoil;松林中微生物数量最少,仅为1.424×106g-1drysoil。土壤微生物的组成以细菌为主,占微生物总数的71.4%-87.7%,其次是放线菌,为总数的9.2%-22.7%,真菌相对较少(1.1%-9.6%)。细菌的数量与微生物总数的变化趋势相一致。人工植被中土壤微生物生物量(mgCmic(100g)-1drysoil)是马占相思林(57.11)>果园(47.79)>红荷木林(42.55)>松林(29.68),与相应的土壤有机碳(gCorgkg-1drysoil)顺序相吻合[马占相思林(16.13)>果园(13.40)>红荷木林(12.59)>松林(11.89)],与土壤生物数量的变化趋势亦相似。与1988年用同一种方法的采样分析结果相比,人工植被中微生物的总数、细菌的数量及其占微生物总数的比率均有所提高,意味着在植被恢复过程中土壤质地得到了改善,其中以马占相思林的土壤恢复速率相对较快。     

The Potential of Cephalophyllum inaequale (L. Bolus) for the Restoration of Degraded Arid Landscapes in Namaqualand, South Africa

The potential of Cephalophyllum inaequale was investigated for use in initiating ecosystem restoration in degraded landscapes of Namaqualand, South Africa. Cephalophyllum inaequale, a perennial shrub, is a member of the succulent Mesembryanthemaceae family, typical of the Succulent Karoo Biome and in particular of the Namaqualand area. A bioclimatic envelope was modeled to establish the area in which this species might feasibly be used. The regional bioclimatic potential for C. inaequale proved to be extensive, covering approximately 17,500 km². An examination of the functional role of C. inaequale showed it to facilitate early seedling survival in this community. A nearest‐neighbor study found no evidence of interspecific competition between C. inaequale and its dominant co‐occurring species, possibly due to vertical stratification of rooting structures. Cephalophyllum inaequale significantly reduced wind speed and soil erosion. Experiments to test the feasibility of propagating, reintroducing, and establishing this species showed that it easily germinates from seed, and transplanted cuttings have a high survival rate. This study demonstrates that C. inaequale has potential for use in initiating the restoration of degraded lands in South Africa .     

Restoration and Rehabilitation of Species-Rich Grassland Ecosystems in France: a Review

In France the alteration of species-rich grasslands is due mainly to agriculture and civil engineering projects (roadways, dams, ski resorts, etc.). The restoration of such ecosystems has been tested in many regions and after many sorts of degradation. According to the level of initial degradation, different responses can be envisioned. Some variations are presented of a general model of restoration and rehabilitation: (1) rejuvenation of fallow land by grazing with rustic animal breeds in wetlands or chalk grasslands in south and northwestern France, (2) restoration by recovery of extensive agricultural management in intensive agricultural areas such as the Rhône or Meuse Valleys, and (3) rehabilitation by appropriate ecological engineering carried out in grasslands degraded by intensification, ski-track, or civil engineering installations. Despite some positive results, these undertakings have not always had the expected effects and therefore should not provide alibis for the destruction of natural grasslands. In general, the success of such undertakings depends on the maintenance in the surrounding areas of protected seed source reservoirs and on the persistence of a diversified landscape pattern permitting connectivity between these seed sources and the restoration or rehabilitation sites.     

江西省不同类型退化荒山生态系统植被恢复与重建措施

对江西省 5种不同类型退化荒山生态系统进行综合治理 ,开展植被恢复与重建技术及理论研究。研究结果表明 :优选的植物组合及合理的配置并辅以工程措施是快速启动植被恢复进程 ,控制水土流失、重建退化荒山生态系统的有效措施。一林多用的树种组合 ,合理的生物体系设计和针、阔叶树种混交是改良地力 ,改善环境 ,促进退化荒山生态系统进展演替的优良途径。先进造林技术的应用和林农牧业结合的复合经营方式是提高综合治理效益 ,促进并维持生态恢复过程稳定的先决条件     

The Importance of Phytogenic Mounds (Nebkhas) for Restoration of Arid Degraded Rangelands in Northern Sinai

Abstract Natural accumulation of wind‐borne sediments within or around the canopies of plants plays an important role in the ecological and evolutionary dynamics of many coastal and desert ecosystems. The formation of such phytogenic mounds (nebkhas) creates patches that can strongly influence the spatial distribution of plant and soil resources. In land restoration of arid and semiarid environments it is important to study the potential role of such biological patchiness that may provide sites for coexistence of species with different life and growth forms. Our main objective was to test whether the nebkhas of a leguminous shrub, Retama raetam (white broom), promote restoration of herbaceous vegetation and soil in the degraded rangelands of northern Sinai. Vegetation and microclimatic and edaphic characteristics within the nebkhas, as well as within internebkha spaces, were compared for ungrazed and grazed sites. Abundance and richness of herbaceous plants were positively related to nebkha area, which explained more of the variance of abundance and richness in the grazed site than in the ungrazed one. Protection from grazing, especially on nebkhas, was associated with an increase in abundance and richness of herbaceous plants, improved soil microclimate, and increased soil fine particles and nutrient concentrations. The results suggest that management (in casu protection from grazing) of nebkhas of woody perennial shrubs changes rangeland conditions and improves the resource regulatory processes. Furthermore, nebkhas of unpalatable plants have the potential to preserve plant diversity in overgrazed plant communities, because they are effective in capturing and retaining water, soil materials, and propagules within and from nearby areas, resources that would otherwise be lost.     

A Climate-Based Approach to the Restoration of Fire-Dependent Ecosystems

Recurrent fires are integral to the function of many ecosystems worldwide. The management of fire‐frequented ecosystems requires the application of fire at the appropriate frequency and seasonality, but establishing the natural fire regime for an ecosystem can be problematic. Historical records of fires are often not available, and surrogates for past fires may not exist. We suggest that the relationship between climate and fire can provide an alternative means for inferring past fire regimes in some ecosystems.     

丛枝菌根在退化土壤恢复中的生态学作用

土壤退化 (包括土壤侵蚀、贫瘠化、盐碱化、沙化、酸化 )不仅为全球所关注 ,而且是关系到我国农业可持续发展的重大问题。全球 1.3× 10 8ｋｍ2 的总土地面积中 ,因人为原因引起的退化面积为 2 0×10 7ｋｍ2 ,这些退化土壤中 ,耕地近 5× 10 8ｈａ ,约占总耕地面积的 1/ 3。我国南方丘陵区土壤退化问题也突出 (水土流失面积 8 0× 10 7ｈａ ,养分贫瘠化 1 9×10 7ｈａ ,污染土壤 3 2× 10 6ｈａ ,酸化土壤 3 2×10 6ｈａ) ,因而探讨恢复和重建退化土壤的途径已成为该地区农业持续发展的重要内容[5] 。菌根 (ｍｙｃｏｒｒｈｉｚａ)是土…     

Evaluation of the Degraded Riparian Ecosystems in the Geum River Watershed in Korea

Riparian vegetation, an important mediator of land–water interactions, provides habitat for animals and other organisms; however, riparian vegetation zones have been altered by agricultural and urban development in Korea. This riparian vegetation survey was conducted to obtain information vital for the ecological restoration and management of the Korean Geum River ecosystem. At 100 study sites, along the Geum River, we recorded the vegetation of the Geum riparian zone. We then surveyed the riparian vegetation associations in the area and overlaid those areas corresponding to trees, shrubs, perennial herbs, annual herbs, exotic plants, cultivated lands, and damaged lands on a geographical map. We also reconstructed the cross-sectional landscape. The mean values of vegetation diversity, exotic plant area (%), annual plant area (%), and species richness were 6.47 ± 0.26, 5.44 ± 1.01, 11.98 ± 1.20, and 22.69 ± 0.93, respectively. The landscape elements of the herbaceous plants were more spread out, compared with those of the woody plants, and 23 sites were composed strictly of herbs. Our results indicate significant differences in vegetation structure among the study sites. For example, at some sites, exotic plants, cultivated lands, and damaged lands dominated the landscape comprising 25.7, 62, and 68.9%, respectively, of the area. The riparian landscape reference model suggested by these results may be applied to studies of other well-conserved riparian zones. We propose that the material pathways and transport of organisms from land to water at Geum River depend on the patchy distribution of these diverse landscape elements.     

Two-Sided Edge Effect Studies and the Restoration of Endangered Ecosystems

Edge effect is the modification of ecological patterns and processes that occur around the edge of two adjacent ecosystems. Depending on their aim, edge effect studies have adopted one of the following methodological approaches: (1) the one‐sided approach—which studies ecological patterns and processes from an edge to the interior of just one of the habitats and (2) the two‐sided approach—which studies ecological patterns and processes across the whole gradient from the interior of one habitat to the interior of the other habitat, passing through the edge zone. A database containing information on 317 published papers revealed that both methodological approaches were equally used until the end of the 1980s. During the 1990s, the question of how organisms respond to habitat destruction and fragmentation led to an abrupt increase in the number of one‐sided studies. Recently, however, two‐sided studies have become more frequent. In this review, we put forth theoretical arguments of why the two‐sided edge effect approach can produce a broader understanding of the ecological processes associated with edges. We highlight that two‐sided edge effect studies must become more experimental and predictive, focusing on the factors controlling edge dynamics. Finally, we point out that two‐sided edge effect studies have the potential to create a positive research agenda for the restoration and expansion of endangered ecosystems.     

Small-Scale Vertical Distribution of Bacterial Biomass and Diversity in Biological Soil Crusts from Arid Lands in the Colorado Plateau

We characterized, at millimeter resolution, bacterial biomass, diversity, and vertical stratification of biological soil crusts in arid lands from the Colorado Plateau. Microscopic counts, extractable DNA, and plate counts of viable aerobic copiotrophs (VAC) revealed that the top centimeter of crusted soils contained atypically large bacterial populations, tenfold larger than those in uncrusted, deeper soils. The plate counts were not always consistent with more direct estimates of microbial biomass. Bacterial populations peaked at the immediate subsurface (1–2 mm) in light-appearing, young crusts, and at the surface (0–1 mm) in well-developed, dark crusts, which corresponds to the location of cyanobacterial populations. Bacterial abundance decreased with depth below these horizons. Spatially resolved DGGE fingerprints of Bacterial 16S rRNA genes demonstrated the presence of highly diverse natural communities, but we could detect neither trends with depth in bacterial richness or diversity, nor a difference in diversity indices between crust types. Fingerprints, however, revealed the presence of marked stratification in the structure of the microbial communities, probably a result of vertical gradients in physicochemical parameters. Sequencing and phylogenetic analyses indicated that most of the naturally occurring bacteria are novel types, with low sequence similarity (83–93%) to those available in public databases. DGGE analyses of the VAC populations indicated communities of lower diversity, with most types having sequences more than 94% similar to those in public databases. Our study indicates that soil crusts represent small-scale mantles of fertility in arid ecosystems, harboring vertically structured, little-known bacterial populations that are not well represented by standard cultivation methods.