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1.
Calligonum mongolicum is a successful pioneer shrub to combat desertification, which is widely used for vegetation restoration in the desert regions of northwest China. In order to reveal the limitations to natural regeneration of C. mongolicum by asexual and sexual reproduction, following the process of sand dune stabilization, we assessed clonal shoots, seedling emergence, soil seed bank density, and soil physical characteristics in mobile and stabilized sand dunes. Controlled field and pot experiments were also conducted to assess germination and seedling emergence in different dune soil types and seed burial depths. The population density of mature C. mongolicum was significantly different after sand dune stabilization. Juvenile density of C. mongolicm was much lower in stabilized sand dunes than mobile sand dune. There was no significant difference in soil seed bank density at three soil depths between mobile and stabilized sand dunes, while the emergence of seedlings in stabilized dunes was much lower than emergence in mobile dunes. There was no clonal propagation found in stabilized dunes, and very few C. mongolicum seedlings were established on stabilized sand dunes. Soil clay and silt content, air‐filled porosity, and soil surface compaction were significantly changed from mobile sand dune to stabilized dunes. Seedling emergence of C. mongolicm was highly dependent on soil physical condition. These results indicated that changes in soil physical condition limited clonal propagation and seedling emergence of C. mongolicum in stabilized sand dunes. Seed bank density was not a limiting factor; however, poor seedling establishment limited C. mongolicum's further natural regeneration in stabilized sand dunes. Therefore, clonal propagation may be the most important mode for population expansion in mobile sand dunes. As a pioneer species C. mongolicum is well adapted to propagate in mobile sand dune conditions, it appears unlikely to survive naturally in stabilized sand dune plantations.  相似文献   

2.
Delay in seed release is found in the dune ecosystem. However, its functions have been rarely reported. We studied delayed seed release in the Agriophyllum squarrosum (Chenopodiaceae), an annual psammophyte, and the Artemisia wudanica (Asteraceae), a psammophilous subshrub in an active sand dune field in Inner Mongolia, China, to get insights into its functions in dealing with sand movement. We concluded that delay in seed release in the dune ecosystem are as follows: (1) postponing dispersal of a portion of seeds until the end of windy season and the start of growing season; (2) regulating the spatiotemporal pattern of seed bank; (3) helping psammophytes adapt to wind erosion on the active sand dune; and (4) helping psammophytes realize long-distance dispersal.  相似文献   

3.
人工固沙措施对沙丘沉积物特征及土壤养分的影响   总被引:5,自引:0,他引:5  
为探明人工铺设尼龙网状固沙措施对风沙危害的影响,以腾格里沙漠东南部人工固定沙丘、两类自然流动沙丘以及防护林的地表沉积物和结皮为研究对象,研究沙丘不同位置、不同深度沉积物的颗粒组成、土壤有机质、有效氮、有效磷、有效钾含量等养分特征。结果表明:(1)人工固定沙丘和自然流动沙丘粒度组成和土壤养分含量都存在显著差异(P<0.5),沙障的防风,固沙和土壤改良作用明显。(2)人工固定沙丘各个地貌位置沉积物粒度频率曲线均出现三峰,反映了沙障对粉尘沉积物的拦截作用,体现了沙障对土壤理化性质的改良过程;分选性随风向逐渐变差,随着粒径变细而好;偏度和峰度明显高于其他。(3)整个研究区沉积物偏碱性,影响着土壤养分含量。人工固定沙丘养分含量最高,有效氮和有机质含量均为最大,有效磷和有效钾含量略低于对比林,其粉沙物质含量与养分含量成正比。(4)人工固定沙丘的沙丘迎、背风坡均有植被分布,并覆有土壤物理结皮,沉积物粒级分配较自然发育的流动沙丘分散,养分含量增加。由此可见,沙障对沙区的土壤环境和生态环境改善具有重要的影响。  相似文献   

4.
A comparison of structure and pattern of the soil seed bank was made between active and stabilized sand dunes in northeastern Inner Mongolia, China. The objective of this paper was to determine the significance of seed bank in vegetation restoration of sand dunes. The results showed that (1) average seed density decreased from stabilized sand dune to interdune lowland of stabilized sand dune, to interdune lowland of active sand dune, and to active sand dune; (2) horizontally, along the transect from interdune lowland to ecotone and to sand dune top, a ‘V’ shaped pattern was presented in the active dune system, and a reverse ‘V’ shaped pattern in the stabilized sand dune system; (3) vertically, the proportion (accounting for the total seeds) of seeds found in 0–20 mm soil profile decreased from stabilized sand dune to interdune lowland of stabilized sand dune, to interdune lowland of active sand dune, and to active sand dune. The same order was also found in 20–50 mm and 50–100 mm soil profiles; (4) the Sokal and Sneath similarity indices in the species-composition between soil seed bank and above-ground vegetation were ranked as: the stabilized sand dune (24%) > the interdune lowland of active sand dune (21%) > the interdune lowland of stabilized sand dune (18%) > the active sand dune (5%); and (5) vegetation restoration of active sand dunes depends on the dispersal of seeds from nearby plant communities on the interdune lowlands. Much effort must be made to preserve the lowlands, as lowlands are the most important seed reservoir in the active sand dune field.  相似文献   

5.
Vegetation patterns are strongly influenced by sand mobility in desert ecosystems. However, little is known about the spatial patterns of Artemisia ordosica, a dominant shrub in the Mu Us desert of Northwest China, in relation to sand fixation. The aim of this study was to investigate and contrast the effects of sand dune stabilization on the population and spatial distribution of this desert shrub. Spatial autocorrelation, semi-variance analysis, and point-pattern analysis were used jointly in this study to investigate the spatial patterns of A. ordosica populations on dunes in Yanchi County of Ningxia, China. The results showed that the spatial autocorrelation and spatial heterogeneity declined gradually, and the distance between the clustered individuals shortened following sand dune fixation. Seedlings were more aggregated than adults in all stage of dune stabilization, and both were more aggregated on shifting sand dunes separately. Spatial associations of the seedlings with the adults were mostly positive at distances of 0–5 m in shifting sand dunes, and the spatial association changed from positive to neutral in semi-fixed sand dunes. The seedlings were spaced in an almost random pattern around the adults, and their distances from the adults did not seem to affect their locations in semi-fixed sand dunes. Furthermore, spatial associations of the seedlings with the adults were negative in the fixed sand dune. These findings demonstrate that sand stabilization is an important factor affecting the spatial patterns of A. ordosica populations in the Mu Us desert. These findings suggest that, strong association between individuals may be the mechanism to explain the spatial pattern formation at preliminary stage of dune fixation. Sand dune stabilization can change the spatial pattern of shrub population by weakening the spatial association between native shrub individuals, which may affect the development direction of desert shrubs.  相似文献   

6.
黄振英  董鸣  张淑敏 《生态学报》2005,25(2):298-303
沙鞭是鄂尔多斯高原流动沙丘上分布的多年生禾草。对位于沙层不同深度的种子萌发和幼苗出土进行了测定。结果表明 ,种子的萌发和幼苗的出土随着沙埋深度的增加而减少 ,最高的幼苗出土率来自 0 .5~ 2 .0 cm浅层沙埋的种子 ,并且沙埋的深度影响种子萌发的时间。沙埋越深 ,越多的种子不能萌发并且处于强迫休眠的状态。但是 ,当被埋较深种子上层的沙层被移走使种子位于较浅的沙层时 ,种子能够克服强迫休眠。种子的强迫休眠还能够通过改善沙层中的空气含量来克服。在自然生境中 ,沙丘的流动性能够使萌发后的幼苗整个暴露在空气中遭受干旱胁迫 ,或者萌发后的幼苗在因无后续的降雨而变干。但是 ,沙鞭在幼苗的早期具有忍受干燥 ,在下次水合后能够恢复生长的能力。幼根的长度和干燥时间影响幼苗的生长恢复率  相似文献   

7.
The rain-fed sand-binding vegetation which stabilizes the migrating desert dunes in the Shapotou area at the southeastern edge of the Tengger Desert was initiated in 1956. The shrubs initially employed were predominantly Caragana korshinskii, Hedysarum scoparium, and Artemisia ordosica, and a desert shrub ecosystem with a dwarf shrub and microbiotic soil crust cover on the stabilized sand dunes has since developed. Since 1956 the success of this effort has not only ensured the smooth operation of the Baotou–Lanzhou railway in the sand dune area but has also played an important role in the restoration of the local eco-environment; therefore, it is viewed as a successful model for desertification control and ecological restoration along the transport infrastructure in the arid desert region of China. Some of the effects of recovery from desertification and ecological restoration on soil properties are shown by the increase in the distribution of fine soil particles, organic matter, and nutrients. The physical surface structure of the stabilized sand dunes, and inorganic soil crusts formed by atmospheric dust, have also led to the gradual formation of microbiotic soil crusts. Sand dune stabilization is associated with: (1) decreased soil particle size, (2) increased total N, (3) increased thickness of microbiotic crusts, (4) increased thickness of subsoil, and (5) an increase in volumetric soil moisture in the near-surface environment. After 17 years of dune stabilization, both the number of shrubs and community biomass decreased. The number of microbes, plant species and vegetation cover, all attained a maximum after the dunes had stabilized for 40 years. There is a significant positive correlation between the fractal dimension of soil particle size distribution (PSD) and the clay content of the shallow soil profile in the desert shrub ecosystem; the longer the period of dune stabilization, the greater the soil clay content in the shallow soil profiles (0–3 cm), and the greater the fractal dimension of soil PSD. This reflects the fact that during the revegetation processes, the soil structure is better developed, especially in the upper profile. Hence, the migrating sand dune becomes more stabilized. Therefore, the fractal model can be used to describe the texture and fertility of the soil, and, along with the degree of stability of the previously migrating sand dunes, can be used as an integrated quantitative index to evaluate the revegetation practice in the sand dune areas and their stabilization.  相似文献   

8.
We compared seedling growth of four Artemisia species dominated at different habitats to determine whether interspecific seedling growth variation of a same genus in tolerance to burial can be used to explain plant distribution in the sand dune field. Interdune lowland species, Artemisia gmelinii, stabilized dune species, A. frigida, semi-stabilized dune species, A. halodendron, and active dune species, A. wudanica were selected. Seedlings grown for 3 weeks were treated at five burial depths for three burial times in pot experiments. Species from the habitats with little burial had smaller survival rate, dry weight and stem elongation speed than those from the habitats with intensive burial when buried. Furthermore, when buried, the former tended to adjust biomass allocation between shoot and root and produce adventitious buds, while the latter tended to maintain a constant root:shoot ratio and produce adventitious roots. We conclude that (1) seedlings of species with a long evolutionary history of exposure to sand burial (from the active sand dune), show quicker stem growth when buried than do seedlings of species from the habitats with little or no sand burial; (2) seedlings of species which do not change root:shoot ratio might be more tolerant of sand burial than those do; (3) seedlings of species from the habitats with intensive sand burial is prone to produce adventitious roots and seedlings of species from the habitats with little or no sand burial tend to produce adventitious buds when buried.  相似文献   

9.
Salix cheilophila Schneid. is a naturally occurring Salix species in Mu Us Sandy Land, Inner Mongolia, China. We focused on the morphological adaptability of S. cheilophila to sand dune burial. For morphological measurements, 32 S. cheilophila seedlings were removed from a community which was in the process of being buried by a shifting sand dune. Each seedling collected included the entire root system. We measured the number, length, and biomass of the adventitious roots, primary lateral roots, and taproot, and compared the morphological characteristics of the root system, including adventitious roots, for seedlings buried to various levels in the sand. The growth range of adventitious roots increased as the length of the buried portion of the main shoot increased. In addition, the total dry weight of all current-year shoots tended to increase gradually with increasing total dry weight of the adventitious roots. These results suggest that S. cheilophila tends to make use of the sedimentary sand layer that accompanies shifting sand dunes. However, there was no correlation between biomass or number of adventitious roots and the length of the buried part of the main shoot. Thus, S. cheilophila does not grow adventitious roots proportional to the buried part. These morphological characteristics of the root system, including the adventitious roots, may indicate that S. cheilophila has poor morphological adaptability to sand dune burial.  相似文献   

10.
Arenophryne rotunda is a small (2–8 g) terrestrial frog that inhabits the coastal sand dunes of central Western Australia. While sand burrowing is a strategy employed by many frog species inhabiting Australia’s semi-arid and arid zones, A. rotunda is unique among burrowing species because it lives independently of free water and can be found nocturnally active on the dune surface for relatively extended periods. Consequently, we examined the physiological factors that enable this unique frog to maintain water balance. A. rotunda was not found to have any special adaptation to reduce EWL (being equivalent to a free water surface) or rehydrate from water (having the lowest rehydration rate measured for 15 Western Australian frog species), but it was able to maintain water balance in sand of very low moisture (1–2%). Frogs excavated in the field were in dune sand of 4.4% moisture content, as a consequence of recent rain, which was more than adequate for these frogs to maintain water balance as reflected by their low plasma and urine osmotic concentrations. We suggest that in dry periods of the year, A. rotunda can achieve positive water balance by cutaneous water uptake by burrowing deeper into the substrate to where the percent water content is greater than 1.5%.  相似文献   

11.
Abstract Spinifex sericeus, a common coastal sand dune grass, typically exhibits decreased vigour in the more stabilized section of the dunes when compared with the active foredune. These differences in vigour appear to be related to different environmental conditions across the dunes such as sand burial and salt spray deposition, both generally decreasing with distance inland. An experiment following the fate of foliar and root applications of 22Na indicated that it may be taken up by the roots or the foliage and then translocated throughout the whole plant, and perhaps even extruded by the roots. Salt spray appeared to have a positive effect on the growth of S. sericeus when applied in conjunction with N and P but had no effect when N and P were not added. Adding acid-washed or non acid-washed foredune sand also resulted in a positive growth response. The results of these experiments indicate that the vigorous growth of S. sericeus on the dynamic sections of the foredunes is due to a stimulation of growth caused by sand deposition.  相似文献   

12.
Urea hydrolysis and transformations in coastal dune sands and soil   总被引:3,自引:0,他引:3  
Summary Urea hydrolysis was studied in samples taken from a coastal sand dune succession, from uncolonized sand; the rhizosphere ofAmmophila arenaria and soil from the mature dune. Comparisons were made with urea hydrolysis in a fertile loam soil. Urea was hydrolyzed in all sand and soil samples, with complete hydrolysis occurring after 6 and 3 weeks in the rhizosphere sand and dune soil compared with only 4 days in the fertile loam. A third of the added urea, however, was still present in the uncolonized sand samples 6 weeks after the beginning of the incubation period. Urea hydrolysis broadly correlated with urease activity.The liberated NH 4 + was oxidized to NO 3 –N in all samples. Urea stimulated the release of N from native organic matter in the two soils, but not sands, due presumably to the low organic matter content of the latter. Nitrite accumulated in the dune sands and soil, but not in the fertile loam.Although N-Serve (Nitrapyrin) had no effect on urea hydrolysis in any of the treated samples, it inhibited the nitrification of released NH 4 + –N. The relevance of these findings to the use of urea as a fertilizer to improve plant growth and dune stabilization is commented upon.  相似文献   

13.
The population structure and water relations ofArtemisia ordosica were studied at different stages of the sand dune fixation process. Vegetation coverage and biomass increased as the sand dune fixation process progressed. In contrast, individual growth rate decreased in the late fixation stage. On fixed sand dunes the modal age ofA. ordosica plants was higher and seedlings or saplings were rearely observed. On active sand dunes, settlement of seedlings was regulated by sand mobility; that is, seedlings were observed only when sand mobility was below 10 cm per year. Leaf transpiration was highest in active sand dunes. Stand transpiration in fixed sand dunes was lower than in semi-fixed sand dunes. These differences in transpiration were related to a decrease in soil water availability, which was affected by the increase in the aeolian fine soil component during the course of sand dune fixation. The reduction in soil water status and the cessation of sand movement were considered to be important factors in the decline of theArtemisia ordosica community.  相似文献   

14.
Pulchrasphaera macronucleata gen. et sp. nov. was isolated from a sand dune on Dauphin Island, Alabama. The distinguishing attributes of the genus include a lobed and perforate parietal chloroplast, lack of pyrenoids, and Protosiphon-type zoospores. The specific epithet calls attention to the unusually large nucleus, a character useful in distinguishing P. macronucleata from other spherical, zoospore producing members of the Chlorococcales.  相似文献   

15.
Aechmea itapoana is a new, conspicuous and distinct species from the coastal sand dune scrub of N.E. Brazil. Its possible relationships within subgenusChevaliera, toA. multiflora andA. rodriguesia are discussed.  相似文献   

16.
Question: Understanding the mechanisms underlying how habitat degradation, topography and rainfall variability interactively affect seed distribution and seedling recruitment is crucial for explaining plant community patterns and dynamics. Interactions between these major factors were studied together in a semiarid sand dune grassland. Location: Eastern Inner Mongolia, China. Methods: The study system used four sites of fixed, semifixed, semishifting and shifting sand dune grasslands, representing a gradient of habitat degradation. We investigated the density of germinable seeds deposited in the top 5 cm of soil and in situ seedling emergence (number of seedlings emerging early in the growing season) and establishment (number of plants recruited at the end of the growing season) at three topographic positions (dune top, windward and leeward sides) within each site over 2 years that differed in rainfall. Habitat characteristics (i.e. vegetation cover, plant species composition and diversity, soil moisture and nutrient availability and soil erodibility) of the four sites were also measured. Results: Habitat degradation (i.e. decreased vegetation cover and enhanced wind erosion rate) significantly reduced the size of the germinable soil seed bank. On average, germinable seed number from the high‐vegetation cover fixed dune was 36‐fold larger than the low‐vegetation cover shifting dune, and eight‐ and two‐fold larger, respectively, than the semishifting and semifixed dunes with intermediate vegetation cover. We observed within‐habitat variability in seed distribution, but among‐topographic position variation differed among habitats. Seedling recruitment showed large between‐year, and among‐ and within‐habitat variability, but these variations varied significantly depending on the response variables evaluated (i.e. initial seedling density, final plant density, emergence rate and recruitment rate). Path analysis revealed complex density‐dependent positive and negative, direct and indirect effects of germinable seed density and initial seedling density on recruitment, but the relative importance of these density‐dependent effects varied depending on habitat type and rainfall availability. Conclusion: Our results suggest that habitat degradation, microtopography and rainfall availability interact in shaping sand dune seed bank and plant community recruitment patterns and dynamics. Their effects were mainly mediated through changes in both the biotic and abiotic environment during the process of habitat deterioration.  相似文献   

17.
The increasing number of stresses on coastal dune ecosystems requires the use of more effective restoration strategies to enhance dune‐building and increase vegetation reestablishment. In this study, the use of a wheat straw as a surrogate wrack was an effective method to improve growth of spring planted Uniola paniculata (sea oats). Approximately 1,000 U. paniculata plugs were planted within 21 × 4 m plots at six replicate sites. Two weeks later, plantings were divided into 11 × 4 m subplots with half of the subplots receiving five bales of wheat straw and the remaining subplots receiving no wheat straw. This surrogate wrack layer measured approximately 10 cm in depth. Mean aboveground biomass of U. paniculata 6 months after planting with surrogate wrack was 9.25 ± 1.00 g compared with 2.18 ± 0.24 g without surrogate wrack. Number of tillers, tiller height, and basal width were also greater at the end of the first growing season for plants treated with surrogate wrack (p < 0.05). Two years after planting, significantly more inflorescences occurred and aboveground biomass (g/m2) was greater with than without surrogate wrack. Sand accumulation was notably greater with surrogate wrack (11.16 cm) than without wrack (7.78 cm) 8 months after planting (p = 0.1093). However, relative sand accumulation was significantly greater with than without surrogate wrack 2 years after planting. Increased sand accumulation suggests surrogate wrack either directly or indirectly traps more sand by creating an additional obstacle or promoting the growth of dune grasses.  相似文献   

18.
Coastal sand dunes support various ecosystem services, including storm protection and tourism. Restoration programs are often critical to preserve this ecosystem due to its fragility and high degree of degradation. Dune restoration still suffers from a general lack of knowledge of the ecological processes controlling tropical dune communities. We investigated if facilitation can increase restoration success by assisting plant survival in a Brazilian coastal dune degraded by buggies at the Environmental Protection Area of Jenipabu, RN, Brazil. We performed two field experiments on dune crest sites degraded by buggies. The first experiment tested how the presence of established vegetation and coconut mesh, mimicking soil‐stabilizing effect of vegetation, facilitates seedling survival and establishment of the early successional dominant dune plant Canavalia maritima (Fabaceae). The second experiment tested if coconut mesh and initial irrigation would allow the establishment of C. maritima outside the vegetation, using both seeds and transplants. We found that the presence of established vegetation positively affected seedling survival. Application of mesh positively affected microclimatic conditions and slightly increased survival, but only for seeds. Initial irrigation only had a small effect on transplanted seedlings survival. Nevertheless, there was extreme seedling mortality in the experiment in particular from sand burial. We conclude that restoration of these dune crests is very difficult. Facilitation by vegetation can reduce plant mortality by sand burial and desiccation, but successful restoration is likely to require a major effort involving a very high number of seedlings or seeds.  相似文献   

19.
张娟  贺学礼  赵丽莉  许伟  闫姣 《生态学报》2015,35(4):1095-1103
克隆植物,尤其是游击型克隆植物,具有很强的扩展能力,通过克隆扩展可侵入到不同生境斑块。克隆植物入侵可能会影响入侵地土壤营养状况和微生物群落。为了探明克隆植物入侵对DSE(dark septate endophytes)活动和土壤理化性质的影响,于2013年6月在克隆植物羊柴(Hedysarum laeve)和沙鞭(Psammochloa villosa)群落空地沿根状茎延伸方向设置样方,分别于6月、8月和10月在样方内分0—10、10—20、20—30、30—40、40—50 cm土层采集土样和根样,研究了不同采样时间羊柴和沙鞭群落空地DSE和土壤理化性质时空变化。结果表明,从6月到10月,随时间后延,克隆植物逐渐侵入群落空地,沙鞭入侵群落空地数和分株数高于羊柴。羊柴群落空地根系DSE定殖率随采样时间后延,逐渐降低,最大值在6月;沙鞭群落空地根系DSE定殖率随采样时间后延,逐渐升高,最大值在10月。随着克隆植物入侵,入侵地土壤中可利用的营养物质含量显著提高,羊柴入侵提高了入侵群落空地土壤碱解N、有效P和速效K含量,沙鞭入侵提高了入侵群落空地土壤碱解N和有效P含量。相关性分析表明,羊柴群落空地DSE定殖率与土壤p H值和电导率显著正相关,沙鞭群落空地DSE定殖率与土壤p H值极显著负相关,与电导率、碱解N和有效P极显著正相关。克隆植物入侵使得土壤环境更有利于克隆植物自身生长,为荒漠植被恢复提供了前提。  相似文献   

20.
The planting of sand‐binding vegetation in the Shapotou region at the southeastern edge of the Tengger Desert began in 1956. Over the past 46 years, it has not only insured the smooth operation of the Baotou–Lanzhou railway in the sand dune section but has also played an important role in the restoration of the local eco‐environment; therefore, it is viewed as a successful model for desertification control and ecological restoration along the transport line in the arid desert region of China. Long‐term monitoring and focused research show that within 4–5 years of establishment of sand‐binding vegetation, the physical surface structure of the sand dunes stabilized, and inorganic soil crusts formed by atmospheric dust gradually turned into microbiotic crusts. Among the organisms comprising these crusts are cryptogams such as desert algae and mosses. In the 46 years since establishing sand‐binding vegetation, some 24 algal species occurred in the crusts. However, only five moss species were identified, which was fewer than the species number in the crust of naturally fixed sand dunes. Other results of the planting were that near‐surface wind velocity in the 46‐year‐old vegetation area was reduced by 54.2% compared with that in the moving sand area; soil organic matter increased from 0.06% in moving sand dunes to 1.34% in the 46‐year‐old vegetation area; the main nutrients N, P, K, etc., in the desert ecosystem increased; soil physicochemical properties improved; and soil‐forming processes occurred in the dune surface layer. Overall, establishment of sand‐binding vegetation significantly impacted soil water cycles, creating favorable conditions for colonization by many herbaceous species. These herbaceous species, in turn, facilitated the colonization and persistence of birds, insects, soil animals, and desert animals. Forty‐six years later, some 28 bird species and 50 insect species were identified in the vegetated dune field. Thus, establishment of a relatively simple community of sand‐binding species led to the transformation of the relatively barren dune environment into a desert ecosystem with complex structure, composition, and function. This restoration effort shows the potential for short‐term manipulation of environmental variables (i.e., plant cover via artificial vegetation establishment) to begin the long‐term process of ecological restoration, particularly in arid climates, and demonstrates several techniques that can be used to scientifically monitor progress in large‐scale restoration projects.  相似文献   

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