Sapling Regeneration Research Articles

Resilience of uneven-aged mixedwood stands altered by diameter-limit cutting and opportunities for their rehabilitation

Repeated diameter-limit cutting in mixedwood forests often leads to altered stand composition, quality, and regeneration, hence decreasing productivity and value over time. We studied the evolution of stand characteristics after diameter-limit cutting on a 15-year period, beginning from 11 to 43 years after cutting. We used 415 sample plots (200 m2) and three criteria: (i) ≥9.0 m2/ha overstory (trees ≥9.1 cm dbh [diameter at breast height, 1.3 m above ground]) acceptable growing stock (AGS, i.e. basal area of vigorous trees with sawlog potential), (ii) ≥3.0 m2/ha pole timber AGS (9.1 cm-23.0 cm dbh) and (iii) ≥60% sapling (dbh 1.1-9.0 cm) stocking of desired species. Stand initial quality was determined in function of overstory AGS at the beginning of the monitoring period: good quality (AGS≥9.0 m2/ha), impoverished (7.0≤AGS< 9.0 m2/ha), degraded (AGS <7.0 m2/ha). After 15 years, 47% of stands satisfied at least two criteria, but most stands (65%) had insufficient sapling regeneration. Stands in good quality and impoverished categories had sufficient basal area and AGS to support a new partial cutting cycle, contrary to stands in the degraded category. A conceptual model based on these three criteria is presented to guide silvicultural rehabilitation of uneven-aged mixedwood stands altered by past cutting practices.

Study on the Regeneration Probability of Understory Coniferous Saplings in the Liangshui Nature Reserve Based on Four Modeling Techniques

Forests are one of the most important natural resources for humans, and understanding the regeneration probability of undergrowth in forests is very important for future forest spatial structure and forest management. In addition, the regeneration of understory saplings is a key process in the restoration of forest ecosystems. By studying the probability of sapling regeneration in forests, we can understand the impact of different stand factors and environmental factors on sapling regeneration. This could help provide a scientific basis for the restoration and protection of forest ecosystems. The Liangshui Nature Reserve of Yichun City, Heilongjiang Province, is a coniferous and broadleaved mixed forest. In this study, we assess the regeneration probability of coniferous saplings (CRP) in natural forests in 665 temporary plots in the Liangshui Nature Reserve. Using Sentinel-1 and Sentinel-2 images provided by the European Space Agency, as well as digital elevation model (DEM) data, we calculated the vegetation index, microwave vegetation index (RVI S1), VV, VH, texture features, slope, and DEM and combined them with field survey data to construct a logistic regression (LR) model, geographically weighted logistic regression (GWLR) model, random forest (RF) model, and multilayer perceptron (MLP) model to predict and analyze the CRP value of each pixel in the study area. The accuracy of the models was evaluated with the average values of the area under the ROC curve (AUC), kappa coefficient (KAPPA), root mean square error (RMSE), and mean absolute error (MAE) verified by five-fold cross-validation. The results showed that the RF model had the highest accuracy. The variable factor with the greatest impact on CRP was the DEM. The construction of the GWLR model considered more spatial factors and had a lower residual Moran index value. The four models had higher CRP prediction results in the low-latitude and low-longitude regions of the study area, and in the high-latitude and high-longitude regions of the study area, most pixels had a CRP value of 0 (i.e., no coniferous sapling regeneration occurred).

Effect of gap size on the regeneration in Larix principis-rupprechtii plantation.

We conducted a survey on seedlings (height <1 m) and saplings (height ≥1 m, diameter at breast height <5 cm) in 20 gaps of Larix principis-rupprechtii plantations on Guandi Mountains, Shanxi to analyze regene-ration density, growth indicators, and spatial distribution of L. principis-rupprechtii seedlings and saplings under four gap sizes (<60 m2, 60-120 m2, 120-180 m2, and ≥180 m2). The results showed that growth indicators (ground diameter, height) of seedlings and saplings and regeneration density of seedlings were highest in small gaps (14-60 m2). The sapling regeneration density was highest in medium gaps (60-120 m2), and sapling density exceeded seedling density in each size category. L. principis-rupprechtii seedlings and saplings exhibited favorable regeneration in small and medium gaps, while large gaps (120-180 m2) and extra-large gaps (≥180 m2) were unfavorable for L. principis-rupprechtii regeneration. L. principis-rupprechtii seedlings and saplings were mainly distributed within the canopy projection area and along the edge of canopy gap area. Controlling gap size within the range of 14-120 m2 through artificial interventions, such as planting and thinning, could promote the regeneration of L. principis-rupprechtii.

Drivers of post-fire Nothofagus antarctica forest recovery in Tierra del Fuego, Argentina

IntroductionLarge wildfires were historically absent in the forests of Tierra del Fuego, southern Argentina. This has changed in recent decades as humans have increased ignition sources, and warmer, drier periods have fueled large, severe wildfires. As a result of its location at an extreme southern latitude, Tierra del Fuego has very low tree species diversity. One of the region's dominant tree species, Nothofagus antarctica, is believed to have traits that may make it resilient to wildfire (e.g., the ability to resprout prolifically).MethodsThis study examined post-fire N. antarctica regeneration across an environmental and time-since-fire gradient. Plots were established in burned areas (n = 160) and unburned controls (n = 32) in and around two wildfires that occurred circa 1940 and in 2019. Seedling/resprout and sapling regeneration densities, as well as site characteristics (e.g., slope) and fire-impacted variables (e.g., distance to mature live trees), were measured.ResultsSeedling and resprout densities were lower in burned plots than in controls, with this trend being exacerbated in the 2019 fire with increasing distance from mature live trees. Regeneration generally occurs in clumps and principally through sprouting from live and top-killed trees, with not all top-killed trees having resprouted. Seedling and resprout densities were most strongly impacted by time since fire, distance to mature live trees and post-fire canopy cover. Sapling densities were modulated by slope, time since fire, and distance to mature live trees.DiscussionDespite lower regeneration densities in recently burned plots and less live basal area and canopy cover in older burned plots compared to unburned controls, burned stands may be on a trajectory to recover pre-fire characteristics, although this recovery is spatially variable. However, full recovery has not occurred 80 years after the 1940's fire. Currently, these burned areas resemble grasslands or savannas. They do not provide the habitat or ecosystem services that denser forests do and may require active restoration to fully recover their pre-fire characteristics.

Controlled Burning and its Effects on Shorea robusta (Sal) Regeneration in Dhansar Block Forest, Rautahat

Fire is used as a management tool to administer a wide range of ecosystems worldwide. Forest fires in Shorea robusta (Sal-dominated) forests take the form of ground fires and mostly affect regeneration. We investigated the effect of forest fire on Sal regeneration in 42 sample plots, of which 21 were subjected to controlled burning. The results showed that species richness decreased from fire-unaffected (19) to fire-affected (10). The total density of Sal seedlings in the fire-affected sites was 3829 seedlings ha-1, while in the fire-unaffected sites were 1779 seedlings ha-1 representing an increased species dominance of Sal species in the post-fire condition. The total density of Sal saplings in the fire-affected sites was 343 seedlings ha-1, while in the fire-unaffected sites was 571 seedlings ha-1. A significant difference with a large effect size (Cohen’s d=0.97) was observed in the seedling regeneration of Sal, while no significant difference was observed in the sapling regeneration of Sal in the post-fire condition. The increment of Sal seedlings may be due to the fire-hardy silvicultural characteristics of Shorea robusta and the decline of Sal saplings may be due to stem mortality in the small diameter classes. We conclude that fire is a beneficial tool for seedling regeneration but not for plant establishment. Future research studies regarding the impact of fire intensities, soil moisture, biological disturbances, temperature, light intensity, etc. on regeneration are recommended.

Natural Forest Regeneration Changes in an Urban Natural Area Forest with White-Tailed Deer (Odocoileus virginianus) Exclusion and Felling by North American Beaver (Castor canadensis)

We examined natural regeneration changes in an urban natural area forest, the Good Woods, Cobbs Creek Park, Philadelphia, Pennsylvania, after placement of exclusion fencing to prevent white-tailed deer (Odocoileus virginianus) browsing and unplanned North American beaver (Castor canadensis) felling. Seedlings (stem dbh < 2.5 cm, stump at 15 cm < 3.0 cm), saplings (stem dbh > 2.5–10 cm, stump at 15 cm > 3.0–11 cm), and trees (stem dbh > 10 cm, stump at 15 cm > 11 cm) were surveyed in 65 permanent 10 m × 10 m plots: 6 y after fencing placement to exclude white-tailed deer and 5 mo after the start of beaver felling. Overall seedling abundance increased by 5% while sapling populations grew by 20% and the number of trees expanded by 34% after white-tailed deer exclusion. Red maple (Acer rubrum) seedlings, tulip poplar (Liriodendron tulipifera) seedlings, and red oak (Quercus rubra) saplings increased significantly while pignut hickory (Carya glabra) and white ash (Fraxinus americana) seedlings decreased significantly. Seedling and tree losses to North American beaver felling were small (<2% for all seedlings and <3% for all trees). However, beaver felling caused a greater than 60% loss of saplings for red maple, black cherry (Prunus serotina), white oak (Quercus alba), and red oak. Less than 30% of the saplings were lost for pignut hickory, white ash, and tulip poplar. Urban North American beaver preferences for native species saplings paralleled rural beaver in the eastern United States. Our results indicate white-tailed deer exclusion fencing is an effective management method for increasing natural regeneration of both seedlings and saplings in an urban natural area forest when the fencing also effectively excludes North American beaver.

Regeneration and growth of tree seedlings and saplings in created gaps of different sizes in a subtropical secondary forest in southern China

Gap-based silvicultural systems are of particular interest in secondary forest management because gaps are associated with regeneration and tree species diversity. However, whether using a range of gap sizes to influence tree regeneration is effective remains unclear. In this study, gaps of different sizes were created to determine their effects on tree regeneration and growth in a secondary Pinus massoniana Lamb. forest in Hunan Province, China. A robustly designed experiment was used with over nine years of repeated measurements. Seedling densities were highest in small gaps, and seedling diversity increased with increasing gap size. Sapling densities and diversity were highest in medium gaps. Within medium and large gaps, saplings were heterogeneously distributed along gradients from opening to closed forest canopy, suggesting gap partitioning of saplings. Emergence rates of three dominant species (Pinus massoniana Lamb, Schima superba Gardn. et Champ., and Cyclobalanopsis glauca (Thunb.) Oerst.) were roughly equal in medium gaps. Regeneration of P. massoniana and C. glauca was spatially diverse as gap sized increased. However, there was little evidence of S. superba divergence within and among gaps, which indicated differential tolerance to shade. A nonlinear mixed-effects model was used to detect effects of microenvironmental variables on diameter–biomass relations. The model suggested that gaps combined with solar radiation, soil moisture, and soil temperature had various effects on sapling biomass accumulation. For saplings with the same basal diameter, estimated average aboveground biomass of S. superba and C. glauca was highest in medium gaps, whereas that of P. massoniana was highest in large gaps. The study suggests that tree regeneration and growth requirements are often not met with a single gap size alone. In practice, a single tree/group selection with medium gaps hybrid approach may be required in subtropical secondary forests to increase regeneration and ecosystem resilience, while also considering other factors such as microenvironmental variables, shade tolerance, and others.

Assessment of Canopy Health with Drone-Based Orthoimagery in a Southern Appalachian Red Spruce Forest

Consumer-grade drone-produced digital orthoimagery is a valuable tool for conservation management and enables the low-cost monitoring of remote ecosystems. This study demonstrates the applicability of RGB orthoimagery for the assessment of forest health at the scale of individual trees in a 46-hectare plot of rare southern Appalachian red spruce forest on Whitetop Mountain, Virginia. We used photogrammetric Structure from Motion software Pix4Dmapper with drone-collected imagery to generate a mosaic for point cloud reconstruction and orthoimagery of the plot. Using 3-band RBG digital orthoimagery, we visually classified 9402 red spruce individuals, finding 8700 healthy (92.5%), 251 declining/dying (2.6%), and 451 dead (4.8%). We mapped individual spruce trees in each class and produced kernel density maps of health classes (live, dead, and dying). Our approach provided a nearly gap-free assessment of the red spruce canopy in our study site, versus a much more time-intensive field survey. Our maps provided useful information on stand mortality patterns and canopy gaps that could be used by managers to identify optimal locations for selective thinning to facilitate understory sapling regeneration. This approach, dependent mainly on an off-the-shelf drone system and visual interpretation of orthoimagery, could be applied by land managers to measure forest health in other spruce, or possibly spruce-fir, communities in the Appalachians. Our study highlights the usefulness of drone-produced orthoimagery for conservation monitoring, presenting a valid and accessible protocol for the monitoring and assessment of forest health in remote spruce, and possibly other conifer, populations. Adoption of drone-based monitoring may be especially useful in light of climate change and the possible displacement of southern Appalachian red spruce (and spruce-fir) ecosystems by the upslope migration of deciduous trees.

Beneficial effects of livestock exclusion on tree regeneration, understory plant diversity, and soil properties in semiarid forests in Iran

AbstractZagros forests in western Iran have been impacted by severe fuelwood removal, traditional agricultural systems, non‐timber products removal, and livestock grazing. These conditions have led to the forest area diminishing from 10 to 6 million hectares over the last six decades. This study was conducted to understand the consequences of livestock exclusion on understory plant diversity, forest tree regeneration, and soil physicochemical properties in semiarid forests. We selected four neighbouring areas, including those subject to livestock exclusion and to grazing, in the Zagros oak forests of Iran. Ten randomized sampling plots (400 m2) were established, and all plant species were recorded in each area. A soil physicochemical analysis indicated a significant improvement in soil nitrogen, phosphorous, potassium, and organic matter in the livestock exclusion area compared to the grazing area. The Shannon–Wiener diversity and species richness was also significantly higher in the livestock exclusion areas compared to the grazed. Grazing tolerant species like Poa bulbosa were abundant in grazing areas, while palatable and nitrogen‐fixing species disappeared. The tree regeneration rate was significantly higher in the exclusion areas compared to the grazing areas, and its values were 0.079 and 0.006 per square metre in the exclusion and grazing areas, respectively. The results of the present study provided evidence that exclusion had a significant effect on improving soil chemical properties, understory plant diversity index, and sapling regeneration. However, the regeneration rates were still low, and therefore, livestock exclusion alone may not be enough to promote forest restoration. Therefore, to better understand plant diversity and tree regeneration in the Zagros forests, livestock exclusion and other factors such as soil seed bank and socio‐economic status of people should be considered.

Effects of Korean Pine Basal Area in Mixed Broadleaved–Korean Pine Forest Stands on Its Natural Regeneration in Northeast China

Abstract Understanding the natural regeneration of Korean pine (Pinus koraiensis Sieb. et Zucc.) in mixed broadleaved–Korean pine (MBK) forests is crucial for MBK forest conservation and secondary deciduous broadleaved forest restoration. We hypothesized the ratio of Korean pine basal area (RKp) in MBK stands affected its natural regeneration. Regeneration censuses, including the height, root collar diameter, age, and growth stages (younger seedling, older seedling, smaller sapling, and taller sapling) of Korean pine, were conducted in northeast China. Results indicated the stem density and age composition of younger seedlings were positively correlated with RKp, whereas those of the saplings were negatively correlated with RKp. In the stands with lower RKp (&amp;lt;80% in Lesser Khingan Mountains [LKM]; &amp;lt;40% in Lushuihe Forestry Bureau [LFB]), individuals in all growth stages regenerated well with an age span of 65 yr. However, the regeneration of taller saplings was severely inhibited with increasing RKp (LKM: RKp ≥ 80%; LFB: RKp ≥ 40%). In summary, RKp significantly affected the natural regeneration of Korean pine in MBK forests. The basal-area thresholds limiting regeneration were found to be 80% in LKM stands and 40% in LFB stands. These basal-area thresholds provided evidence of why the zonal climax was MBK forests rather than pure Korean pine forests.

Unexpected spatial patterns of natural regeneration in typical uneven-aged mixed pine-oak forests in the Sierra Madre Occidental, Mexico

Natural forest regeneration, i.e. self-renewal of forest stands, involves the replacement of old trees by the next generation and is influenced by environmental factors. The spatial structure of tree regeneration depends on and also influences the properties of the stands themselves. Few studies have investigated spatial patterns of naturally regenerated areas in Mexican pine–oak forests, which are considered one of the world’s top 34 biodiversity hotspots. In this study, we analyzed the spatial patterns, particularly the spatial structure, in clusters of naturally regenerated trees in seven 100 × 100 m plots in the Sierra Madre Occidental (northern Mexico), in relation to three factors: slope, geographical aspect and distance between each sapling to the edge of the nearest gap in the canopy. Three indices were used to describe spatial structure and the data were analyzed by bivariate Ripley’s K(t)-functions and three-parameter and six-parameter Weibull models. The results indicate that sapling regeneration was marginal in canopy gaps. Sapling density was ten times higher under the canopy cover, close to the edge than in the gaps. On average, the first maximum number of saplings was detected inside the canopy at about 81 cm from the gap edge, forming ring-type spatial patterns around the canopy gaps. These results contrast with the gap dynamics described in many other studies. We attribute these findings to the nurse effect of trees, which ameliorate abiotic effects, such as the extreme drought that occurred in 2011 and 2012 in the study region. In covered zones close to canopy edges, thece orientation. We recommend adapting or changing the current forest management system to improve continuous forest regeneration (including adaptive silviculture). We also strongly support i) research on the effects of cattle grazing on natural regeneration in the region and ii) reduction of livestock pressure, which is essential to support forest renewal. Complementary reforestation, in addition to maintenance of the few saplings growing within the gaps, may help enhance forest regeneration. Finally, the use of alternative regeneration methods, such as an irregular group shelterwood method (Expanding Gap Silviculture “Femelschlag”), should also be considered, in order to promote natural regeneration more purposefully.

Population structure and regeneration dynamics of Firmiana major, a dominant but endangered tree species

Firmiana major (Malvaceae) is a dominant tree species endemic in arid-hot and arid-warm valleys in Southwest China. Human disturbance, mainly the use of its bark to produce rope, caused a sharp decline in F. major populations before 1980s. The plant was declared extinct in 1998 but reappeared in 2001. Knowledge of population structure, regeneration characteristics, and current threats is fundamental for its conservation and recovery. In this study, we conducted field surveys and identified fourteen F. major localities, including eleven new localities. Fewer than 4,000 individuals were present in six populations. In four populations, the recruitment of new plants was low, while the other two populations had positive regeneration of seedlings and saplings. Grazing pressure might have caused a reduction in the number of younger trees. The case found in a national nature reserve proved that in situ protection over decades was essential in restoring and regenerating F. major (Panzhihua population). Although sprouting can promote F. major regeneration, it didn’t revert the decline of the populations. The number of individuals and occupancy are highly likely to decline in the near future. Therefore, F. major falls into the Vulnerable (VU) category and should be classified as a Plant Species with Extremely Small Populations (PESEP) of China. The conservation implications and actions were introduced.

Two directions of regeneration of post-windthrow pine stands depend on the composition of the undergrowth and the soil environment

Alongside fires, windthrows are among the strongest forest disturbances, which is why research on the regeneration of windthrown forests is so important for silviculture. While there have been many studies devoted to the regeneration of windthrown boreal spruce forests, few have dealt with the regeneration of Scots pine forests in the temperate zone.In Pisz Forest (northern Poland), the State Forests administration left 475.6 ha of pine stands disturbed by windthrow for research on spontaneous ecosystem recovery, leaving all broken trees untouched. For the 11-year study (beginning in 2008, six years after the windthrow, when saplings became more abundant), 10 × 10 m research plots were established in pine stands with different classes of severity of windthrow disturbance: severely disturbed stands (canopy cover up to 30%), moderately disturbed stands (canopy cover of 40–60%) and the least disturbed stands (canopy cover of 70–90%). Each year all saplings on the plots were recorded, with measurements of their height, diameter at breast height, and changes in the percentage cover of forest floor vegetation and its species composition. Selected environmental variables were measured as well. Density of pine saplings in the severely disturbed stands was lower than in the moderately and least disturbed stands, while the density of birch saplings was higher in the moderately disturbed stands than in the least disturbed stands. Moss P. schreberi particularly favored spontaneous regeneration of pine saplings, while the nitrophilous grass D. flexuosa, overgrowing entire surfaces, impeded it. Soil cover by a litter layer alone also significantly hampered the emergence of tree saplings.An elevated content of nitrogen in the soil was conducive to rapid coverage of the area by D. flexuosa, while limiting cover by moss P. schreberi. Moss P. schreberi and shrubs V. vitis-idaea preferred soil with a high respiration rate, while grass D. flexuosa avoided it. Two directions of spontaneous regeneration of windthrown stands were shown, depending on cover by grass or mosses and on the initial content of nitrogen in the soil, which provided the basis for indicating two different forest management strategies in windthrown pine forests.

Initial regeneration success of tree species after different forestry treatments in a sessile oak-hornbeam forest

Ecological, economic, and social demands triggered a shift in the management of temperate deciduous forests from rotation forestry system towards more nature-based forest management techniques such as continuous cover forestry. However, there is insufficient knowledge on the regeneration success of different tree species—especially oaks—within this management system. Through a systematic experiment, we compared the regeneration processes of a sessile oak-hornbeam forest after gap-cutting (as an element of continuous cover forestry system) to regeneration after clear-cutting, preparation cutting, and in retention tree groups (treatments of rotation forestry system). A managed, closed, mature forest was used as control. Several different aspects of the regeneration were studied: (1) seed supply of sessile oak—Quercus petraea (Matt.) Liebl., (2) species number and abundance of the natural regeneration, (3) survival and growth of individual saplings of five tree species (sessile and Turkey oak—Quercus cerris L., hornbeam—Carpinus betulus L., beech—Fagus sylvatica L., and common ash—Fraxinus excelsior L.). The number of acorns was high in closed forest, intermediate in preparation cutting and retention tree group, low in gaps, and zero in clear-cutting. Four years after the interventions, there was no detectable treatment effect on the species number of regeneration. Survival increased in every treatment compared to control, but there was no significant difference in this measure between the differently treated sites. Height growth was highest in the gaps and clear-cuts, intermediate in preparation cuts, and lowest in retention tree groups and controls. Species with different seed dispersal mechanisms responded differently to treatments: oaks were dispersal-limited in the gaps and clear-cuts, while anemochorous species (e.g., hornbeam and manna ash) were present in every treatment. The survival and growth pattern of the particular species proved to be similar, but the intensity of the response differed: shade-tolerants (hornbeam, beech, and ash) showed better survival than oaks in most treatments, and their height growth was larger. According to our results, oak regeneration establishes successfully in oak-hornbeam forests not only in the case of rotation forestry, but also during continuous cover forestry (gap-cutting). The survival and growth of the saplings are similar in cutting areas and gaps, but keeping in mind other considerations (such as preserving forest continuity, balanced site conditions, and forest biodiversity), continuous cover forestry should be preferred.

Species composition and structure of an exotic Quercus suber stand on the island of Gran Canaria (Canary Islands)

Aim of the study: Although introduced tree species have been recognized as adversely affecting native ecosystems, conversely, some studies suggest they can facilitate recovery and promote the establishment of native plant communities. This study tests whether a native plant community is established under the closed canopies of an exotic species by analyzing regeneration and plant species composition.Area of study: Finca de Osorio, a public property of the Cabildo de Gran Canaria included in the Doramas Rural Park (Canary Islands, Spain).Main results: The results reveal that sapling regeneration is dominated by the exotic species, though some native ones are also present. The sapling regeneration community did not differ from the tree canopy composition, so, a native plant community recovery cannot be expected to occur. In addition, other introduced species were also present in the sapling composition community.Research highlights: The laurel forest of the Canary Islands is the most emblematic plant community of the Canary Island archipelago. The studied area dominated by Q. suber does not favor the regeneration of the native plant community. Thus, restoration programs will be required to enhance the native plant community and the area covered by this highly disturbed plant ecosystem on the island of Gran Canaria.Keywords: catalytic effect; invasion; laurel forest; plant community.

Foraging behaviour of snowshoe hares (Lepus americanus) in conifer forests regenerating after fire

Wildfires in conifer forests create patchy, heterogeneous landscapes. For many animal species, this post-fire variability means having to navigate quite different habitat patches to locate adequate cover and food. For snowshoe hares (Lepus americanus Erxleben, 1777), post-fire landscapes could include risky open patches, as well as dense regenerating stands rich in food and cover. We analyzed snowshoe hare tortuosity, speed of movement, and amount of browse along winter foraging pathways in unburned mature forest and in dense regenerating stands or open areas with sparse regeneration 12–13 years after the Okanagan Mountain Park fire (&gt;25 000 ha near Kelowna, British Columbia, Canada) to determine whether hares change foraging behaviour in relation to cover type. Hares moved the fastest and browsed the least in open habitats. Hares browsed most often in areas where sapling regeneration was dense; their main forage was lodgepole pine (Pinus contorta Douglas ex Loudon). No differences were found in pathway tortuosity in relation to cover type (open, regenerating, or mature patches). When hares moved slower along foraging pathways, they also moved slightly more tortuously and ate more. These results suggest that hares prefer post-fire areas with dense tree regeneration.

湖南栎类天然次生林幼树更新特征及影响因子

PDF HTML阅读 XML下载 导出引用 引用提醒 湖南栎类天然次生林幼树更新特征及影响因子 DOI: 10.5846/stxb201806061269 作者: 作者单位: 中南林业科技大学,中南林业科技大学,贵州省植物园,中南林业科技大学,中南林业科技大学,中南林业科技大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31570631）；国家林业局项目（1692016-06） Regeneration characteristics and related factors affecting saplings in Quercus spp. natural secondary forests in Hunan Province, China Author: Affiliation: Forestry College, Central South University of Forest ＆ Technology, Changsha 410004, China,,Guizhou Botanical Garden,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以湖南典型栎类天然次生林为研究对象，基于51块样地的调查数据，采用k-means聚类分析划分林分类型，研究湖南不同栎类天然次生林幼树更新特征，分析了湖南不同栎类天然次生林幼树更新指标（幼树密度、幼树平均地径、平均高以及平均冠幅）与环境因子、林分因子的相关性，旨在阐明环境因子、林分因子对幼树更新的影响，以期为湖南不同栎类天然次生林的恢复与经营管理提供理论依据。结果表明：（1）利用聚类分析可将研究区内栎类天然次生林划分为5个类型，包括甜槠锥栗混交林（CC）、亮叶水青冈多脉青冈混交林（FC）、石栎樟树混交林（LC）、枹栎甜槠混交林（QC）、青冈栎混交林（CG）。（2）不同类型栎类天然次生林更新幼树优势种分化明显，物种丰富度差异显著（P < 0.05）。5种不同栎类次生林幼树密度均未超过500株/hm2，更新情况较差；幼树数量差异显著（P < 0.05），为亮叶水青冈多脉青冈混交林 > 石栎樟树混交林 > 青冈栎混交林 > 枹栎甜槠混交林 > 甜槠锥栗混交林；生长情况差异显著（P < 0.05），为青冈栎混交林 > 亮叶水青冈多脉青冈混交林 > 枹栎甜槠混交林 > 甜槠锥栗混交林 > 石栎樟树混交林。（3）相关分析结果显示，不同类型次生林幼树更新的主要影响因子存在差异。甜槠锥栗混交林中幼树密度与腐殖质厚度呈显著负相关（P < 0.05）；幼树平均高与灌木盖度呈显著正相关（P < 0.05）；幼树平均地径与草本盖度、灌木盖度呈显著正相关（P < 0.05）。亮叶水青冈多脉青冈混交林中幼树密度与海拔、腐殖质厚度、枯落物厚度呈显著正相关（P < 0.05），与草本盖度呈极显著正相关（P < 0.01）；幼树平均地径与郁闭度呈显著负相关（P < 0.05）；幼树平均高、幼树平均冠幅与坡位呈显著正相关（P < 0.05）。石栎樟树混交林中幼树密度与坡向、土壤厚度呈显著正相关（P < 0.05），其余因子对幼树生长无显著影响。枹栎甜槠混交林中幼树密度与郁闭度、乔木密度呈极显著正相关（P < 0.01），与坡位呈显著负相关（P < 0.05）；幼树平均冠幅与坡度呈显著负相关（P < 0.05）。青冈栎混交林中幼树平均地径与土壤厚度呈显著正相关（P < 0.05），与乔木密度呈极显著正相关（P < 0.01）；幼树平均冠幅与灌木盖度呈显著正相关（P < 0.05）。 Abstract:Quercus forest is a typical forest type in Hu'nan Province, which plays an important role in water and soil conservation, and maintaining ecological stability. However, most of the natural regeneration of Quercus forest in Hunan is poor, because of limited research on Quercus regeneration mechanisms, and ineffective management. Based on field investigation data, we analyzed typical Quercus natural secondary forests in Hunan, and used k-means cluster analysis to classify forest types. In this research, we studied sapling regeneration characteristics of different Quercus natural secondary forests in Hunan and examined the correlation of the sapling regeneration index (density, average ground diameter, average height, and average crown width of saplings) with environmental and stand factors in different Quercus natural secondary forests in Hunan. This study aimed to provide a theoretical basis for the restoration and management of natural secondary forests of different Quercus species in Hunan Province. The results showed that the natural secondary forest of Quercus could be divided into five types by cluster analysis, including Castanopsis eyrie-Castanea henryi mixed forest (CC), Fagus lucida-Cyclobalanopsis multinervis mixed forest (FC), Lithocarpus glaber-Cinnamomum bodinieri mixed forest (LC), Quercus serrata-Castanopsis eyrie mixed forest (QC), and Cyclobalanopsis glauca mixed forest (CG). The dominant species and species richness of the regeneration forests of different types of Quercus secondary forests were significantly different(P < 0.05). The sapling density in five different secondary forests of Quercus was < 500 trees/hm2, and sapling regeneration was poor. The number of saplings of different Quercus secondary forests was significantly different(P < 0.05), in the order of FC > LC > CG > QC > CC. The sapling growth status in different forests was significantly different(P < 0.05), and in the sequence of CG > FC > QC > CC > LC. The results of the correlation analysis showed that there were differences in the main factors affecting sapling regeneration in different types of secondary forests. In CC, there was a significant negative correlation between the sapling density and humus thickness(P < 0.05), a significant positive correlation between the average sapling height and shrub coverage(P < 0.05), and a significant positive correlation between the average sapling basal diameter and herbaceous and shrub coverage(P < 0.05). In FC, there was a significant positive correlation between sapling density and altitude, humus thickness, and litter thickness(P < 0.05), and a very significant positive correlation with herbaceous coverage(P < 0.01), a significant negative correlation between average ground diameter and canopy density(P < 0.05), and the average sapling height and crown width were significantly positively correlated with the slope position(P < 0.05). In LC, there was a significant positive correlation between sapling density and slope direction and soil thickness(P < 0.05), whereas the other factors had no significant effect on sapling growth. In QC, sapling density was extremely positively correlated with canopy and tree density(P < 0.01), and negatively correlated with slope position(P < 0.05), and the average sapling crown width was negatively correlated with slope(P < 0.05). In CG, the average sapling diameter was significantly positively correlated with soil thickness(P < 0.05), and had an extremely significant positive correlation with tree density(P < 0.01), and the average sapling crown width was positively correlated with shrub coverage(P < 0.05). 参考文献 相似文献 引证文献

Understanding the recruitment response of juvenile Neotropical trees to logging intensity using functional traits.

Selective logging remains a widespread practice in tropical forests, yet the long-term effects of timber harvest on juvenile tree (i.e., sapling) recruitment across the hundreds of species occurring in most tropical forests remain difficult to predict. This uncertainty could potentially exacerbate threats to some of the thousands of timber-valuable tree species in the Amazon. Our objective was to determine to what extent long-term responses of tree species regeneration in logged forests can be explained by their functional traits. We integrate functional trait data for 13 leaf, stem, and seed traits from 25 canopy tree species with a range of life histories, such as the pioneer Goupia glabra and the shade-tolerant Iryanthera hostmannii, together with over 30 yr of sapling monitoring in permanent plots spanning a gradient of harvest intensity at the Paracou Forest Disturbance Experiment (PFDE), French Guiana. We anticipated that more intensive logging would increase recruitment of pioneer species with higher specific leaf area, lower wood densities, and smaller seeds, due to the removal of canopy trees. We define a recruitment response metric to compare sapling regeneration to timber harvest intensity across species. Although not statistically significant, sapling recruitment decreased with logging intensity for eight of 23 species and these species tended to have large seeds and dense wood. A generalized linear mixed model fit using specific leaf area, seed mass, and twig density data explained about 45% of the variability in sapling dynamics. Effects of specific leaf area outweighed those of seed mass and wood density in explaining recruitment dynamics of the sapling community in response to increasing logging intensity. The most intense treatment at the PFDE, which includes stand thinning of non-timber-valuable adult trees and poison-girdling for competitive release, showed evidence of shifting community composition in sapling regeneration at the 30-yr mark, toward species with less dense wood, lighter seeds, and higher specific leaf area. Our results indicate that high-intensity logging can have lasting effects on stand regeneration dynamics and that functional traits can help simplify general trends of sapling recruitment for highly diverse logged tropical forests.

Understanding the Recruitment Response of Juvenile Neotropical Trees to Logging Intensity Using Functional Traits

Selective logging remains a widespread practice in tropical forests, yet the long-term effects of timber harvest on juvenile tree (i.e., sapling) recruitment across the hundreds of species occurring in most tropical forests remain difficult to predict. This uncertainty could potentially exacerbate threats to some of the thousands of timber-valuable tree species in the Amazon. Our objective was to determine to what extent long-term responses of tree species regeneration in logged forests can be explained by their functional traits. We integrate functional trait data for 13 leaf, stem, and seed traits from 25 canopy tree species with a range of life histories, such as the pioneer Goupia glabra and the shade-tolerant Iryanthera hostmannii, together with over 30 yr of sapling monitoring in permanent plots spanning a gradient of harvest intensity at the Paracou Forest Disturbance Experiment (PFDE), French Guiana. We anticipated that more intensive logging would increase recruitment of pioneer species with higher specific leaf area, lower wood densities, and smaller seeds, due to the removal of canopy trees. We define a recruitment response metric to compare sapling regeneration to timber harvest intensity across species. Although not statistically significant, sapling recruitment decreased with logging intensity for eight of 23 species and these species tended to have large seeds and dense wood. A generalized linear mixed model fit using specific leaf area, seed mass, and twig density data explained about 45% of the variability in sapling dynamics. Effects of specific leaf area outweighed those of seed mass and wood density in explaining recruitment dynamics of the sapling community in response to increasing logging intensity. The most intense treatment at the PFDE, which includes stand thinning of non-timber-valuable adult trees and poison-girdling for competitive release, showed evidence of shifting community composition in sapling regeneration at the 30-yr mark, toward species with less dense wood, lighter seeds, and higher specific leaf area. Our results indicate that high-intensity logging can have lasting effects on stand regeneration dynamics and that functional traits can help simplify general trends of sapling recruitment for highly diverse logged tropical forests.

How Forest Gap and Elevation Shaped Abies faxoniana Rehd. et Wils. Regeneration in a Subalpine Coniferous Forest, Southwestern China

Focusing on the underlying ecological mechanisms of dominant species regeneration in forest gaps at a landscape scale can provide detailed understanding for gap-based forest management. The individual effects of forest gaps or elevation on the regeneration of Abies faxoniana Rehd. et Wils. are well known, although elucidating how gap characteristics and elevation concurrently influence regeneration remains an important challenge. In this paper, we present an explorative study using structural equation models (SEMs) to assess the direct and indirect effects of forest gaps and elevation on Abies faxoniana Rehd. et Wils. regeneration. Four of the predicted SEMs showed the following results: (1) Temperature, photosynthetic photon flux density (PPFD), soil total carbon, gap openness, shrub layer cover, herb layer cover, and moss layer thickness in forest gaps were associated with Abies faxoniana regeneration along an elevation gradient in subalpine coniferous forest. (2) Elevation had a generally negative and indirect effect on Abies faxoniana regeneration. Forest gaps positively affected regeneration when compared with non-gap plots and gap size was positively related to small tree regeneration density and the ratio of height to diameter at breast height (HD ratio) of the tallest Abies faxoniana small trees but was negatively related to Abies faxoniana sapling regeneration density. (3) In forest gaps, the Abies faxoniana sapling density and HD ratio of the tallest Abies faxoniana small trees were mainly indirectly influenced by elevation, and Abies faxoniana small tree regeneration density was directly associated with the dominance of the sapling regeneration density. In summary, Abies faxoniana regeneration was negatively and largely affected by elevation (total effect), although forest gaps enhanced Abies faxoniana regeneration by multiple pathways (direct and indirect effects).