Outcomes of longterm deciduous forest restoration in southwestern Ontario, Canada     

S.M McLachlan  D.R Bazely 《Biological conservation》2003,113(2):159-169

At present, forest cover in southwestern Ontario, Canada, remains at less than 5% due to intensive agricultural and urban land use. Although much of the extant forest is increasingly protected by legislation, remnants continue to be degraded by the spread of non-native plant species, overgrazing, and recreational use. Some parks in the region have adopted management programs aimed at mitigating this degradation. Over the last 35 years, cottages and roads at Point Pelée National Park have been removed and sites either passively restored (i.e. road or cottage eliminated and vegetation allowed to regenerate) or actively restored (i.e. road or cottage eliminated, exotic vegetation removed, and native species planted). In 1994 and 1995, we assessed the effectiveness of restoration by comparing the understorey plant communities in 28 restored sites with those in less disturbed reference sites. There was a significant increase (P<0.0001) in the similarity of understorey plant communities between restored and reference sites as time-since-restoration increased. Soil moisture, canopy cover, distance to continuous forest, and site-shape all significantly affected plant species composition. Former road sites recovered significantly (P<0.05) more rapidly than former cottage sites, and the former lawns of passively restored cottage sites were the slowest to recover. Five years following active restoration, non-native ruderal species continued to dominate restored sites. The observed recovery of understorey plant communities in restored sites is attributed to their proximity to natural vegetation, and its function as a seed source. In some sites, recovery is substantial and, assuming present trajectories of change are maintained, we predict that recovery could occur in many mesic sites within the next 20 years. Restoration activity facilitates forest recovery and would appear to have a valuable function in mitigating ongoing conflicts between conservation and human use in this region.  相似文献   

河南烟草连作状况调查及连作障碍解决对策研究   总被引：5，自引：0，他引：5  

陈继峰  赵松辉  蔡凯旋  刘洪源  石礼森 《中国园艺文摘》2014,(5):218-222

河南烤烟连作以4～5年为主。烤烟连作后病虫害加重,烟叶产量和品质下降等问题比较严重。目前研究认为烤烟连作障碍主要因为连作烟田矿质养分、微生物种类和数量、土壤中酶活性及自毒作用等方面发生了恶性变化,加重了烟草生产中病虫害发生,阻碍了烟株的生长发育。文章通过对目前河南烟区连作情况的调查,并结合已有的研究,从连作烟田消毒、种植模式、施肥模式、微生物菌剂修复等方面探讨了缓解乃至解决烟草连作障碍问题的措施。  相似文献   

黔中喀斯特植被不同演替阶段群落物种组成及多样性   总被引：4，自引：0，他引：4  

杨华斌  韦小丽  党伟 《山地农业生物学报》2009,28(3)

采用空间序列替代时间序列的方法,对贵州省黔中地区共23块样地进行常规群落学调查,分析了黔中喀斯特退化森林植被不同演替阶段的物种组成及多样性变化.结果表明:在草本阶段,占优势的物种是芒、地瓜藤、密毛蕨等先锋物种,灌木阶段主要物种有圆果化香、野扇花、异叶鼠李等,而乔木层主要的树种有猴樟、云南鼠刺、椤木石楠等.黔中喀斯特植被恢复趋势是向组成物种增多,多样性指数上升而生态优势度降低的方向发展,与同是喀斯特地貌的茂兰喀斯特森林植被相比,不同之处是群落的均匀度指数没有随着群落演替而增加,而是呈减小的趋势,这与黔中地区的乔灌过渡阶段、乔林阶段优势种的优势地位突出有关.  相似文献   

云雾山天然草地30年恢复演替过程中优势草种生态位动态     

史晓晓  程积民  于飞  朱仁斌  赵新宇 《草地学报》2014,22(4):677-684

为探究云雾山天然草地30年恢复演替过程中优势草种的生态位动态,通过典型样方调查,运用Levins和Pianka公式分别对封育5年、9年、14年、18年和30年天然草地的主要物种生态位进行了分析。结果表明：不同封育年限草地的物种组成与群落类型具有明显差异,阿尔泰狗哇花（Heteropappus altaicus）、大针茅（Stipa grandis）、二裂委陵菜（Potentilla bifurca）和百里香（Thymus mongolicus）4个种群生态位总宽度较大,且在5个不同封育年限草地均有出现。云雾山原建群种长芒草（Stipa bungeana）生态位宽度也较大,但在封育30年样方中未发现其分布。不同封育年限各物种生态位宽度排序和其总宽度排序并不相同,封育5年、9年和14年的草地中生态位宽度最大的分别是长芒草、甘肃蒿（Artemisia gansuensis）和猪毛蒿（A.scoparia）,封育18年和30年草地大针茅最大。随着封育年限增加,优势物种的生态位宽度出现波动,大针茅的生态位宽度随封育年限增加呈现“升-降-升”的动态变化,封育5~18年,长芒草生态位宽度变化表现为先降后升,甘青针茅（S.przewalskyi）只在封育30年样地出现,但其生态位宽度仅次于大针茅。种群间生态位重叠与不同封育年限草地种群生态位宽度无线性关系,封育9年草地种群间的生态位重叠指数均值最大,封育14年和30年草地的生态位重叠指数均值呈递增趋势。随着封育年限的增加,草地生态系统逐渐得到恢复,种间竞争也随之增加。  相似文献   

不同演替阶段沙地植物群落物种多样性研究   总被引：2，自引：2，他引：0  

姚国龙王涛  宗世祥 《中国农学通报》2009,25(24):167-170

本文采用空间换时间的研究方法,对毛乌素沙地南缘流动沙地、半固定沙地、半固定沙地与固定沙地过渡带和固定沙地内的植物群落物种多样性进行了研究。结果表明：不同演替阶段沙地内植物群落多样性呈不断增加的变化趋势,各演替阶段均有不同的植物群落和优势物种。豆科和藜科植物作为流动沙地的先锋物种,表现出较强的适应能力;禾本科和菊科植物由流动沙地到固定沙地,其种类变化较大,表明其在沙地恢复中发挥着巨大的作用;萝摩科植物可作为区分流动沙地和其它沙地类型的指示性植物;马齿苋科和紫薇科植物仅在固定沙地中出现,已成为判断固定沙地的标志性植物。除沙地恢复过程中人为播种的柠条和沙蒿外,流动沙地阶段的优势物种是沙米,半固定阶段是沙生冰草,半固定沙地与固定沙地过渡地带是老瓜头和地梢瓜,而固定沙地则为花棒和地梢瓜。因此,在沙漠化治理中应根据不同的沙地类型选择不同的植物种类。  相似文献   

Regeneration of Rocky Mountain bristlecone pine (Pinus aristata) and limber pine (Pinus flexilis) three decades after stand-replacing fires     

Jonathan D. Coop  Anna W. Schoettle 《Forest Ecology and Management》2009

Rocky Mountain bristlecone pine (Pinus aristata) and limber pine (Pinus flexilis) are important high-elevation pines of the southern Rockies that are forecast to decline due to the recent spread of white pine blister rust (Cronartium ribicola) into this region. Proactive management strategies to promote the evolution of rust resistance and maintain ecosystem function require an improved understanding of the role of disturbance on the population dynamics of both species and environmental conditions that favor seedling establishment. We examined patterns of bristlecone and limber pine regeneration across the perimeters of three, 29-year-old, high-severity burns in northern, central, and southern Colorado: Ouzel, Badger Mountain, and Maes Creek, respectively. Both species exhibited a very protracted regeneration response to these fires. Bristlecone pine regeneration was concentrated near burn edges and beneath surviving seed sources. This spatial pattern is consistent with limitations incurred by wind-dispersal, also borne out by the low occurrence of seedling clusters. Relative to unburned stands, the absolute abundance of bristlecone pine generally increased only on plots retaining some surviving trees. Limber pine regeneration pattern varied between sites: high in the burn interior at Ouzel, concentrated at burn edges at Badger, and mostly in unburned stands at Maes. Clark’s Nutcracker dispersal of limber pine in each study area was indicated by high seedling distance from possible seed sources and high frequencies of clustered stems. Except at Ouzel, the absolute abundance of limber pine decreased in burns. Across sites, establishment by both species was boosted by nearby nurse objects (rocks, fallen logs, and standing tree trunks), a relationship that extended out at least as far as the closest three such objects, usually found within 50 cm. Fire decreased the frequency of Pedicularis but increased Castilleja and Ribes species (alternate hosts of white pine blister rust), though only one species, R. cereum, was positively associated with either pine species. We conclude that regeneration of bristlecone and limber pine may benefit from natural disturbance or proactive management creating appropriately sized openings and microtopographic structure (e.g., abundant fallen logs); however, beneficial responses may require many decades to be achieved.  相似文献   

Tropical dry forest succession and the contribution of lianas to wood area index (WAI)     

G. Arturo Sánchez-Azofeifa  Margaret Kalácska  Mario Marcos do Espírito-Santo  G. Wilson Fernandes  Stefan Schnitzer 《Forest Ecology and Management》2009

The transmission and interception of light through the canopy is an important indicator of forest productivity in tropical forest ecosystems, and the amount of light that eventually reaches the forest floor is influenced by its interactions with leaves, branches, fruits, and flowers among many different canopy elements. While most studies of forest canopy light interception focus on leaf area index (LAI), very few studies have examined wood area index (WAI), which may account for a substantial component of light interception in tropical forests. The influence of lianas on the interception of light and their overall contribution to WAI is a potentially important factor, but it is generally overlooked because of its difficulty to assess. In this paper we evaluate the relative contribution that lianas have to the overall WAI and canopy openness as function of successional stage via a latitudinal comparison of sites across the Americas (Mexico, Costa Rica and Brazil). Our results suggest that lianas significantly increase WAI and decreases canopy openness. However, lianas were absent at all of our study sites where canopy openness exceeded 60%. Our data are the first to explicitly document the role of lianas in the estimation of WAI and, overall, they will contribute to better estimations of ecosystem level LAI in tropical environments, where there is a lack of data on WAI.  相似文献   

Role reversal in the stand dynamics of an angiosperm–conifer forest: Colonising angiosperms precede a shade-tolerant conifer in Afrotemperate forest     

Hylton Adie  Michael J. Lawes 《Forest Ecology and Management》2009

In mixed angiosperm–conifer forests worldwide, infrequent landscape-level catastrophic disturbances create a mosaic of persistent and different aged forest stands in the landscape with varying levels of dominance by the conifer component. In the ‘temporal stand replacement model’ (TSRM), disturbance creates conditions favouring a colonising cohort that is replaced by a suite of relatively shade-tolerant canopy species, which establish following the synchronous senescence of the pioneer canopy. In most southern hemisphere mixed angiosperm–conifer forests, with the exception of those in southern Africa, the establishing cohort is usually a large and very long-lived (550–650 years) conifer that is gradually replaced by angiosperms. As an explanation of the apparent dominance of the conifer Podocarpus latifolius, we examine the efficacy of the TSRM in mixed Afrotemperate forests where the establishing cohort is not a conifer. Forest succession in Afrotemperate forests was deterministic with the successive replacement of species determined first by their establishment success in shaded environments, and second, by their relative longevity. Several angiosperm species that were common canopy dominants established a pioneer cohort but were gradually replaced by P. latifolius, a shade-tolerant species. Continuous regeneration beneath the angiosperm canopy by P. latifolius eliminates synchronous canopy senescence, a key feature of the TSRM, as a mechanism driving the temporal replacement of canopy species. Senescing angiosperms created canopy gaps that were colonised by grasses and ferns, which suppressed canopy tree regeneration. In contrast, with continuous regeneration beneath the shaded canopy, P. latifolius gains a critical advantage over angiosperms at gap formation. Thus, in the absence of fairly large-scale natural disturbances, conifers come to dominate Afrotemperate forests. Commensurate with the latter, conifers in Podocarpus-forest were dated to approximately 320 years, more than 100 years older than the oldest P. latifolius in angiosperm-dominated forest. Tree life-history differences (shade tolerance, longevity) and the time since disturbance drive successional change from an angiosperm-dominated system to a stage dominated by P. latifolius. In general, the TSRM is a plausible explanation for the observed canopy tree structure and dynamics in mixed Afrotemperate forests. South African Afrotemperate forest is unusual among other southern hemisphere mixed angiosperm–conifer forests in that a suite of angiosperm canopy species, rather than a single conifer species, forms the colonising cohort.  相似文献   

Limited native plant regeneration in novel, exotic-dominated forests on Hawai’i   总被引：1，自引：0，他引：1  

Joseph Mascaro  Kristen K. Becklund  R. Flint Hughes  Stefan A. Schnitzer 《Forest Ecology and Management》2008,256(4):593-606

Ecological invasions are a major driver of global environmental change. When invasions are frequent and prolonged, exotic species can become dominant and ultimately create novel ecosystem types. These ecosystems are now widespread globally. Recent evidence from Puerto Rico suggests that exotic-dominated forests can provide suitable regeneration sites for native species and promote native species abundance, but this pattern has been little explored elsewhere. We surveyed 46 sites in Hawai’i to determine whether native species occurred in the understories of exotic-dominated forests. Native trees smaller than 10 cm in diameter were absent in 28 of the 46 sites and rare in the others. Natives were never the dominant understory species; in fact, they accounted for less than 10% of understory basal area at all but six sites, and less than 4% on average. Sites with native species in the understory tended to be on young lava substrate lacking human disturbance, and were mostly located close to intact, native-dominated forest stands. Even where we found some native species, however, most were survivors of past exotic encroachment into native forest, rather than products of active recolonization by native species. In contrast with successional trajectories in Puerto Rico, Hawaii's exotic-dominated forests can emerge, via invasion, without human disturbance and native Hawaiian plants are largely unable to colonize them once they appear. We suggest that a wide diversity of growth strategies among the exotic species on Hawai’i may limit the opportunities for native plants to colonize exotic-dominated forests.  相似文献   

Spatially explicit modeling of mixed-severity fire regimes and landscape dynamics     

Michael C. Wimberly  Rebecca S.H. Kennedy 《Forest Ecology and Management》2008

Simulation models of disturbance and succession are being increasingly applied to characterize landscape composition and dynamics under natural fire regimes, and to evaluate alternative management strategies for ecological restoration and fire hazard reduction. However, we have a limited understanding of how landscapes respond to changes in fire frequency, and about the sensitivity of model predictions to assumptions about successional pathways and fire behavior. We updated an existing landscape dynamics model (LADS) to simulate the complex interactions between forest dynamics, fire spread, and fire effects in dry forests of the interior Pacific Northwest. Experimental model runs were conducted on a hypothetical landscape at fire rotations ranging from 5 to 50 years. Three sensitivity analyses were carried out to explore the responses of landscape composition to (1) parameters characterizing succession and fire effects on vegetation, (2) the probability of fire spread into different successional stages, and (3) the size and spatial pattern of static fire refugia. The area of old open-canopy forests was highest at the shortest fire rotations, and was particularly sensitive to the probability of stand-replacement fire in open-canopy forests and to the fire-free period required for ingrowth to occur in open-canopy forests. The area of old closed-canopy forests increased with lengthening fire rotation, but always comprised a relatively small portion of the landscape (<10%). The area of old closed-canopy forests increased when fire spread was more rapid in open-canopy forests than in closed-canopy forests, and when the physical landscape incorporated large “fire refugia” with low fire spread rates. Old closed-canopy forests appear to comprise a relatively minor landscape component in mixed-severity fire regimes with fire rotations of 50 years or less. However, these results are sensitive to assumptions about the spatial interactions between fire spread, landscape vegetation patterns, and the underlying physical landscape.  相似文献