The survival rate of Castanopsis kawakamii from seed to seedling is relatively low,leading to difficulties in the regeneration of its natural forests.Forest gaps play a vital role in plant regeneration and biodiversit...The survival rate of Castanopsis kawakamii from seed to seedling is relatively low,leading to difficulties in the regeneration of its natural forests.Forest gaps play a vital role in plant regeneration and biodiversity maintenance in forest ecosystems.Unfortunately,our understanding of the effects of gap size and within-gap position on the seed germination and radicle growth of C.kawakamii is still limited.In particular,our knowledge on the relationship between gap size and environmental factors and their influence on seed germination and radicle growth is incomplete.In the present study,we studied the influences of forest gaps and within-gap position on seed regeneration on the germination and radicle growth of an endangered species C.kawakamii in a subtropical natural forest in China.We selected three large gaps(LG,gap size above 200 m^(2)),three medium gaps(MG,gap size 50-100 m^(2)),three small gaps(SG,gap size 30-50 m^(2)),and non-gap(NG),and planted the seeds of C.kawakamii in five positions within each gap.The results showed that(1)the influence of forest gaps on seed germination rate was,from highest to lowest,medium gaps(51%),non-gap(47%),small gaps(40%)and large gaps(17%),and the seed germination rate was the highest in all positions in medium gaps,with the exception of the east position.(2)Radicle length in forest gaps was,from highest to lowest,medium gaps,small gaps,large gaps and non-gap,and it was the highest in the east,south,west and north positions of medium gaps.(3)Canopy openness(gap size)and air temperature were the main factors influencing seed germination and radicle growth of C.kawakamii.We concluded that medium-sized gaps were the most suitable for seed germination and radicle growth of C.kawakamii,and they promote the regeneration of this endangered species in the investigated natural forest.展开更多
In Korea, damaging typhoons related to climate change have increased steadily since the 1990s. Red pine （Pinus densiflora） forests in Gwangneung Forest were greatly disturbed by typhoon Kompasu in 2010. A survey was...In Korea, damaging typhoons related to climate change have increased steadily since the 1990s. Red pine （Pinus densiflora） forests in Gwangneung Forest were greatly disturbed by typhoon Kompasu in 2010. A survey was carried out to clarify differences in ground beetle （Coleoptera： Carabidae） communities between forest gaps and undamaged forests. Ground beetles were sampled using pitfall traps from early May to late October 2011. Vegetation changes, litter layer, organic matter layer, and soil conditions were also measured. A total of 1035 ground beetles of 32 species were collected. Contrary to our expectation, species richness, abundance, and community structure of the ground beetles in forest gaps were similar to those in undamaged forests. Species richness and abundance of habitat type were also similar. However, species diversity and estimated species richness in forest gaps were significantly higher than in undamaged forests. These findings suggest that forest gaps formed by a typhoon did not lead to great change in ground beetle communities.展开更多
In forest ecosystems, gap formation changes the allocation of abiotic resources and thus affects the survival and growth of understory plants. However, how tree seedling survival and growth respond to low-temperature ...In forest ecosystems, gap formation changes the allocation of abiotic resources and thus affects the survival and growth of understory plants. However, how tree seedling survival and growth respond to low-temperature events and the influencing mechanisms remain unclear. To clarify how low-temperature event limits the survival and growth of tree seedlings in the montane regions of eastern Liaoning Province, northeast China, we investigated temperature and light intensity within secondary forest gaps, and the survival and growth of Juglans mandshurica seedlings after a low-temperature event in the spring of 2014. Damage to seedlings due to low temperature sig- nificantly varied in different aspects. Seedlings in gaps on southeast-facing slopes were the most seriously damaged, followed by those in gaps on northeast-facing slopes. In contrast, seedlings in west-facing gaps and in control plots without slope aspect were not damaged. The freezing injury index for seedlings was negatively correlated with minimum temperature （r = - 0.608, P 〈 0.01）, but it was positively correlated with light intensity （r= 0.818, P 〈 0.01）. In addition, height and root collar diameter of damaged seedlings were significantly lower than those of the undamaged seedlings （P 〈 0.01） during the early growing season （April-July）, but no significant difference were observed during the late growing season （July-Oc- tober） （P 〉 0.05）. The extent of seedling damage was directly related to slope aspect. Low temperature and high light intensity were found to be the dominant factors affecting extent of damage to seedlings on southeast- and northeast-facing slopes.展开更多
Object-based classification differentiates forest gaps from canopies at large regional scale by using remote sensing data. To study the segmentation and classification processes of object-based forest gaps classificat...Object-based classification differentiates forest gaps from canopies at large regional scale by using remote sensing data. To study the segmentation and classification processes of object-based forest gaps classification at a regional scale, we sampled a natural secondary forest in northeast China at Maoershan Experimental Forest Farm.Airborne light detection and ranging(LiDAR; 3.7 points/m2) data were collected as the original data source and the canopy height model(CHM) and topographic dataset were extracted from the LiDAR data. The accuracy of objectbased forest gaps classification depends on previous segmentation. Thus our first step was to define 10 different scale parameters in CHM image segmentation. After image segmentation, the machine learning classification method was used to classify three kinds of object classes, namely,forest gaps, tree canopies, and others. The common support vector machine(SVM) classifier with the radial basis function kernel(RBF) was first adopted to test the effect of classification features(vegetation height features and some typical topographic features) on forest gap classification.Then the different classifiers(KNN, Bayes, decision tree,and SVM with linear kernel) were further adopted to compare the effect of classifiers on machine learning forest gaps classification. Segmentation accuracy and classification accuracy were evaluated by using Mo¨ller's method and confusion metrics, respectively. The scale parameter had a significant effect on object-based forest gap segmentation and classification. Classification accuracies at different scales revealed that there were two optimal scales(10 and 20) that provided similar accuracy, with the scale of 10 yielding slightly greater accuracy than 20. The accuracy of the classification by using combination of height features and SVM classifier with linear kernel was91% at the optimal scale parameter of 10, and it was highest comparing with other classification classifiers, such as SVM RBF(90%), Decision Tree(90%), Bayes(90%),or KNN(87%). The classifiers had no significant effect on forest gap classification, but the fewer parameters in the classifier equation and higher speed of operation probably lead to a higher accuracy of final classifications. Our results confirm that object-based classification can extract forest gaps at a large regional scale with appropriate classification features and classifiers using LiDAR data. We note, however, that final satisfaction of forest gap classification depends on the determination of optimal scale(s) of segmentation.展开更多
In order to improve the understanding of the role of a canopy opening/gap on the physical environments in a secondary forest in Northeastern China, a case study was conducted in and around a small irregular gap in a m...In order to improve the understanding of the role of a canopy opening/gap on the physical environments in a secondary forest in Northeastern China, a case study was conducted in and around a small irregular gap in a montane secondary forest. The secondary forest, which was severely disturbed by human beings about 50 years ago, was dominated by Quercus mongolica and Fraxinus rhynchophyllaan. Temporal variation in photosynthetic photon flux density （PPFD）, air temperature （TA） at 10 cm above the ground, soil temperature （Ts） and soil water content （SWC） at top-layer （0-15 cm） and sub-layer （15-30 cm） were measured from May to September after the second year since the formation of the small gap （the ratios of gap diameter to stand height were less than 0.5） in 2006 respectively. Results indicated that the highest value of PPFD occurred at the northern edge of the gap, particularly at the beginning of the growing season in May. On sunny days, the highest value of PPFD appeared earlier than that on overcast days. Maximum and mean values of TAwere higher in the northern part of the gap, and the minimum values of TAwere at the southern edge of the gap. Soil temperature varied obviously in the gap with the range from 1 to 8 ℃. Maximum values of Ts occurred at the northern part of the gap, which was significantly correlated with the maximum values of TA （R = 0.735, P〈0.05）. SWC was higher in the top-layer （0-15 cm） than that in sub-layer （15-30 cm）, but the difference of them was not significant （p〉0.05）, which might be attributed to the small gap size and the effects of aboveground vegetations. From these results, the maximum of PPFD in the study area occurred at the northern part of the gap, which was consistent with the results observed in north hemisphere, but the occurrence time varied with the differences of the latitudes. The highest values of air and soil temperatures also occurred in the northern part of the gap because they were affected by the radiation. However, the variation of temperature in July was different from other months due to the influence of gap size. And the values of soil water content were neither higher in the gap in the wet season nor lower in the dry season, which might be affected by the gap size and topography the gap located. The variations of light, soil and air temperatures, and soil moisture in this small irregular gap might be related to the effects of the micro-site, which affects the regeneration of plant species.展开更多
Aims Alpine forest gaps can control understory ecosystem processes by manipulating hydrothermal dynamics.Here,we aimed to test the role of alpine forest gap disturbance on total phenol loss(TPL)from the decomposing li...Aims Alpine forest gaps can control understory ecosystem processes by manipulating hydrothermal dynamics.Here,we aimed to test the role of alpine forest gap disturbance on total phenol loss(TPL)from the decomposing litter of two typical shrub species(willow,Salix paraplesia Schneid.,and bamboo,Fargesia nitida(Mitford)Keng f.).Methods We conducted a field litterbag experiment within a representative fir(Abies faxoniana Rehd.)forest based on‘gap openness treatments’(plot positions in the gap included the gap center south,gap center north,canopy edge,expanded edge and closed canopy).The TPL rate and litter surface microbial abundance(fungi and bacteria)of the two shrub species were measured during the following periods over 2 years:snow formation(SF),snow cover(SC),snow melting(ST),the early growing season(EG)and the late growing season(LG).Important Findings At the end of the study,we found that snow cover depth,freeze–thaw cycle frequency and the fungal copies g−1 to bacterial copies g−1 ratio had significant effects on litter TPL.The abundances of fungi and bacteria decreased from the gap center to the closed canopy during the SF,SC,ST and LG periods and showed the opposite trend during the EG periods.The rate of TPL among plot positions closely followed the same trend as microbial abundance during the first year of incubation.In addition,both species had higher rates of TPL in the gap center than at other positions during the first winter,first year and entire 2-year period.These findings suggest that alpine forest gap formation accelerates litter TPL,although litter TPL exhibits dual responses to gap disturbance during specific critical periods.In conclusion,reduced snow cover depth and duration during winter warming under projected climate change scenarios or as gaps vanish may slow litter TPL in alpine biomes.展开更多
Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to pre- serve bio- and...Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to pre- serve bio- and pedo-diversity, influencing nutrient cycles, and maintain- ing the complex structure of the late-successional forests. Over the last 30 years, numerous reviews have been written describing gap dynamics. Here we synthesize current understanding on gap dynamics relating to tree regeneration with particular emphasis on gap characteristics consid- ered critical to develop ecologically sustainable forest management sys- tems and to conserve native biodiversity. Specifically, we addressed the question： how do gaps influence forest structure？ From the literature re- viewed, the size of gaps induces important changes in factors such as light intensity, soil humidity and soil biological properties that influence tree species regeneration and differ in gaps of different sizes. Shade- tolerant species can colonize small gaps; shade-intolerant species need large gaps for successful regeneration. Additionally, gap dynamics differ between temperate, boreal, and tropical forests, showing the importance of climate differences in driving forest regeneration. This review summa- rizes information of use to forest managers who design cutting regimes that mimic natural disturbances and who must consider forest structure, forest climate, and the role of natural disturbance in their designs.展开更多
Many methods of restoration and rebuilding of forestry ecosystem were used, because the function of the secondary broad-leaved forests declined. one of these methods was the artificial regeneration carried out with ga...Many methods of restoration and rebuilding of forestry ecosystem were used, because the function of the secondary broad-leaved forests declined. one of these methods was the artificial regeneration carried out with gap technique in the forest. The results showed that the communities had been getting to Korean pine forests mixed with broad-leaved trees and the speed of development was much faster than before.展开更多
With the concem of regcneration, characteristics of canopy gaps in broad-leaved Korean pine forest were studied.The areas of actual gap, expanded gap and maximum gap were analyzed respectively. The species composition...With the concem of regcneration, characteristics of canopy gaps in broad-leaved Korean pine forest were studied.The areas of actual gap, expanded gap and maximum gap were analyzed respectively. The species composition, number, origin,decayed class and sizes of gap makers were studied comprehensively. The comparative studies of regencration inside and outside of canopy gap showed that the density of regeneration inside canopy gaps was 30% higher than that outside canopy gaps. The specific species regeneration response to canopy gap varied greatly. Pinus koraiensis, Picea jezoensis Frarinlis nla)ldshurica, JItghI)ls )nalJholu-i`a and Acer mono generally did not response to canopy gap disturbance. The Regeneration Importantce Valuc (RIV) of Abies nephrolepis, Ulmus Japonica increased with canopy gap disturbance. RIV of Tilia amurensis, Acer madshurica and Ulmus laciniata decreased with canopy gap disturbance. Canopy gap disturbance was not strong enough to result in the regeneration of some rpecies of shade intolerance such as Larix olgensis, Betula platyphylla.展开更多
We investigated non-structural carbohydrates（NSC） levels and components（starch,glucose,fructose and sucrose） in the leaves of three typical co-occurring forestfloor plants,moss Eurhynchium savatieri（ES）,fern Par...We investigated non-structural carbohydrates（NSC） levels and components（starch,glucose,fructose and sucrose） in the leaves of three typical co-occurring forestfloor plants,moss Eurhynchium savatieri（ES）,fern Parathelypteris nipponica（PN） and forb Aruncus sylvester（AS） in a 30-year-old Chinese pine（Pinus tabulaeformis）plantation forest on the eastern Tibetan Plateau.We also explored their responses to three gap creation treatments（control and two gap creations of 80 and 110 m2） based on NSC levels.PN had the highest leaf NSC level of the three plants,with AS second and ES lowest.Starch was the predominant component of NSC and the contents of glucose were higher than those of fructose or sucrose for all three species.The NSC level of ES in intermediate gaps was significantly higher than at control sites.PN also had higher NSC levels in both small and intermediate gaps than in control sites.But the differences between treatments were not obvious for AS.Our results suggest that ES and PN benefit from gap formation while the two species have different NSC response sensitivities to gap size,but the leaf NSC level of AS is less sensitive to the disturbance.展开更多
Picea mongolica is an endemic but endangered species in China. The spruce forest is only found in sandy forest-steppe ecotones. In this study, we examined the initial response of the quantity and refilling process of ...Picea mongolica is an endemic but endangered species in China. The spruce forest is only found in sandy forest-steppe ecotones. In this study, we examined the initial response of the quantity and refilling process of free roots in an artificial canopy gap with a diameter of 36 m in a P. mongolica forest. Under the canopy, the fine root length densities of trees, shrubs and herbs were 2,622, 864 and 3,086 m·m^- 2, respectively. The free root biomass of trees, shrubs and herbs were 148, 62 and 65 g·m^- 2, respectively. In the gap, the fine root length density of trees was 151 m·m^- 2. The mean fine root densities of shrubs and herbs in the gap were 756 and 2,568 m·m^- 2. The fine root biomass of trees, shrubs and herbs were 9, 52 and 47 g·m^- 2, respectively. Two growing seasons after the gap creation, hardly any fine tree roots were found in the middle of the gap. The living tree roots in the gap edge zone were mainly located within a 4.5 m distance from the standing trees. Indices developed to show the influence of trees on free root length density clearly revealed the effect of the vicinity of living trees on fine root length density. The root densities of shrubs and herbs did not show a clear response to gap creation despite the increase of their foliage. Our results suggest that in P mongolica forests a gap disturbance creates a distinct tree root gap and that the gap edge trees do not extend their root systems rapidly into the formed root gap.展开更多
Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and regeneration, and is an important indicator of forest management quality. The objective of this study was to compare ga...Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and regeneration, and is an important indicator of forest management quality. The objective of this study was to compare gap fraction estimates from undisturbed forests and different environments or strata of selectively logged areas. Moreover, gap fraction measurements were collected with two distinct instruments (optical canopy analyzer LAI-2000 and hemispherical photographs). Field data were collected from two sustainable forest management sites at Jamari National Forest, Rondonia State, Brazilian Amazon. Our results indicated significant differences between data acquired using these two instruments. For instance, the LAI-2000 data showed greater variation for each environment compared to hemispherical photographics data, and the data were also more sensitive to the increase in gap fraction. Small variations were found in the gap fraction means for the two study areas, and only data for the undisturbed area were significantly different. A gradient of increasing gap fraction that ranged from primary forests to log decks was observed. Furthermore, a multiple linear regression analysis determined the contribution of the selectively logged environments to decreased forest cover, confirming the observed gradient.展开更多
Since 1950, 700 plots were established in the alpine and canyon region of western Sichuan. The distribution charac-teristics and the relationships between forest succession and environmental gradients were studied. Th...Since 1950, 700 plots were established in the alpine and canyon region of western Sichuan. The distribution charac-teristics and the relationships between forest succession and environmental gradients were studied. The results showed that the main tree species were Picea and Abies in this region, and there were more than 90 forest types. Abies forests mainly dis-tributed in the middle and upper reaches of rivers and their branches, and Picea forests mainly distributed in wide valleys and on half-shaded and half-sunny slopes. The natural regeneration was poor under primitive spruce and fir forest canopy, but was good in the spruce and fire forest gap. The relationship between forest succession and vertical gradient was closely related to the relationship between forest succession procession and plant synusia under primary forests. Human activities could promote and postpone succession process. The results of expanding regeneration were often influenced by topography, vegetation and wind direction.展开更多
Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest ...Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.展开更多
基金funded by the National Natural Science Foundation of China,grant numbers 31700550 and 31770678the Nature Science Fund of the Fujian Province Science and Technology of China,grant number 2019J01367+1 种基金the Science and Technology Promotion of Project Forestry Bureau of the Fujian Province,grant number 2018TG14-2the Innovation and Technology Fund of Fujian Agriculture and Forestry University,grant number CXZX2018125.
文摘The survival rate of Castanopsis kawakamii from seed to seedling is relatively low,leading to difficulties in the regeneration of its natural forests.Forest gaps play a vital role in plant regeneration and biodiversity maintenance in forest ecosystems.Unfortunately,our understanding of the effects of gap size and within-gap position on the seed germination and radicle growth of C.kawakamii is still limited.In particular,our knowledge on the relationship between gap size and environmental factors and their influence on seed germination and radicle growth is incomplete.In the present study,we studied the influences of forest gaps and within-gap position on seed regeneration on the germination and radicle growth of an endangered species C.kawakamii in a subtropical natural forest in China.We selected three large gaps(LG,gap size above 200 m^(2)),three medium gaps(MG,gap size 50-100 m^(2)),three small gaps(SG,gap size 30-50 m^(2)),and non-gap(NG),and planted the seeds of C.kawakamii in five positions within each gap.The results showed that(1)the influence of forest gaps on seed germination rate was,from highest to lowest,medium gaps(51%),non-gap(47%),small gaps(40%)and large gaps(17%),and the seed germination rate was the highest in all positions in medium gaps,with the exception of the east position.(2)Radicle length in forest gaps was,from highest to lowest,medium gaps,small gaps,large gaps and non-gap,and it was the highest in the east,south,west and north positions of medium gaps.(3)Canopy openness(gap size)and air temperature were the main factors influencing seed germination and radicle growth of C.kawakamii.We concluded that medium-sized gaps were the most suitable for seed germination and radicle growth of C.kawakamii,and they promote the regeneration of this endangered species in the investigated natural forest.
基金supported by the Korea Forest Research Institute(Project FE 0100-2009-01,effect of climate change on forest ecosystem and adaptation of forest ecosystem)
文摘In Korea, damaging typhoons related to climate change have increased steadily since the 1990s. Red pine （Pinus densiflora） forests in Gwangneung Forest were greatly disturbed by typhoon Kompasu in 2010. A survey was carried out to clarify differences in ground beetle （Coleoptera： Carabidae） communities between forest gaps and undamaged forests. Ground beetles were sampled using pitfall traps from early May to late October 2011. Vegetation changes, litter layer, organic matter layer, and soil conditions were also measured. A total of 1035 ground beetles of 32 species were collected. Contrary to our expectation, species richness, abundance, and community structure of the ground beetles in forest gaps were similar to those in undamaged forests. Species richness and abundance of habitat type were also similar. However, species diversity and estimated species richness in forest gaps were significantly higher than in undamaged forests. These findings suggest that forest gaps formed by a typhoon did not lead to great change in ground beetle communities.
基金supported by the National Key Research and Development Program of China(2016YFC0500302)the National Nature Scientific Foundation Project of China(31200432)
文摘In forest ecosystems, gap formation changes the allocation of abiotic resources and thus affects the survival and growth of understory plants. However, how tree seedling survival and growth respond to low-temperature events and the influencing mechanisms remain unclear. To clarify how low-temperature event limits the survival and growth of tree seedlings in the montane regions of eastern Liaoning Province, northeast China, we investigated temperature and light intensity within secondary forest gaps, and the survival and growth of Juglans mandshurica seedlings after a low-temperature event in the spring of 2014. Damage to seedlings due to low temperature sig- nificantly varied in different aspects. Seedlings in gaps on southeast-facing slopes were the most seriously damaged, followed by those in gaps on northeast-facing slopes. In contrast, seedlings in west-facing gaps and in control plots without slope aspect were not damaged. The freezing injury index for seedlings was negatively correlated with minimum temperature （r = - 0.608, P 〈 0.01）, but it was positively correlated with light intensity （r= 0.818, P 〈 0.01）. In addition, height and root collar diameter of damaged seedlings were significantly lower than those of the undamaged seedlings （P 〈 0.01） during the early growing season （April-July）, but no significant difference were observed during the late growing season （July-Oc- tober） （P 〉 0.05）. The extent of seedling damage was directly related to slope aspect. Low temperature and high light intensity were found to be the dominant factors affecting extent of damage to seedlings on southeast- and northeast-facing slopes.
基金financially supported by grant from National Natural Science Foundation of China(No.31300533)
文摘Object-based classification differentiates forest gaps from canopies at large regional scale by using remote sensing data. To study the segmentation and classification processes of object-based forest gaps classification at a regional scale, we sampled a natural secondary forest in northeast China at Maoershan Experimental Forest Farm.Airborne light detection and ranging(LiDAR; 3.7 points/m2) data were collected as the original data source and the canopy height model(CHM) and topographic dataset were extracted from the LiDAR data. The accuracy of objectbased forest gaps classification depends on previous segmentation. Thus our first step was to define 10 different scale parameters in CHM image segmentation. After image segmentation, the machine learning classification method was used to classify three kinds of object classes, namely,forest gaps, tree canopies, and others. The common support vector machine(SVM) classifier with the radial basis function kernel(RBF) was first adopted to test the effect of classification features(vegetation height features and some typical topographic features) on forest gap classification.Then the different classifiers(KNN, Bayes, decision tree,and SVM with linear kernel) were further adopted to compare the effect of classifiers on machine learning forest gaps classification. Segmentation accuracy and classification accuracy were evaluated by using Mo¨ller's method and confusion metrics, respectively. The scale parameter had a significant effect on object-based forest gap segmentation and classification. Classification accuracies at different scales revealed that there were two optimal scales(10 and 20) that provided similar accuracy, with the scale of 10 yielding slightly greater accuracy than 20. The accuracy of the classification by using combination of height features and SVM classifier with linear kernel was91% at the optimal scale parameter of 10, and it was highest comparing with other classification classifiers, such as SVM RBF(90%), Decision Tree(90%), Bayes(90%),or KNN(87%). The classifiers had no significant effect on forest gap classification, but the fewer parameters in the classifier equation and higher speed of operation probably lead to a higher accuracy of final classifications. Our results confirm that object-based classification can extract forest gaps at a large regional scale with appropriate classification features and classifiers using LiDAR data. We note, however, that final satisfaction of forest gap classification depends on the determination of optimal scale(s) of segmentation.
基金This research was supported by National Natural Science Foundation of China （30671669） and ＂the 100-Young-Researcher Project＂ of Chinese,Academy of Sciences.
文摘In order to improve the understanding of the role of a canopy opening/gap on the physical environments in a secondary forest in Northeastern China, a case study was conducted in and around a small irregular gap in a montane secondary forest. The secondary forest, which was severely disturbed by human beings about 50 years ago, was dominated by Quercus mongolica and Fraxinus rhynchophyllaan. Temporal variation in photosynthetic photon flux density （PPFD）, air temperature （TA） at 10 cm above the ground, soil temperature （Ts） and soil water content （SWC） at top-layer （0-15 cm） and sub-layer （15-30 cm） were measured from May to September after the second year since the formation of the small gap （the ratios of gap diameter to stand height were less than 0.5） in 2006 respectively. Results indicated that the highest value of PPFD occurred at the northern edge of the gap, particularly at the beginning of the growing season in May. On sunny days, the highest value of PPFD appeared earlier than that on overcast days. Maximum and mean values of TAwere higher in the northern part of the gap, and the minimum values of TAwere at the southern edge of the gap. Soil temperature varied obviously in the gap with the range from 1 to 8 ℃. Maximum values of Ts occurred at the northern part of the gap, which was significantly correlated with the maximum values of TA （R = 0.735, P〈0.05）. SWC was higher in the top-layer （0-15 cm） than that in sub-layer （15-30 cm）, but the difference of them was not significant （p〉0.05）, which might be attributed to the small gap size and the effects of aboveground vegetations. From these results, the maximum of PPFD in the study area occurred at the northern part of the gap, which was consistent with the results observed in north hemisphere, but the occurrence time varied with the differences of the latitudes. The highest values of air and soil temperatures also occurred in the northern part of the gap because they were affected by the radiation. However, the variation of temperature in July was different from other months due to the influence of gap size. And the values of soil water content were neither higher in the gap in the wet season nor lower in the dry season, which might be affected by the gap size and topography the gap located. The variations of light, soil and air temperatures, and soil moisture in this small irregular gap might be related to the effects of the micro-site, which affects the regeneration of plant species.
基金supported by the National Natural Science Foundation of China(no.31570445 and 31800518).
文摘Aims Alpine forest gaps can control understory ecosystem processes by manipulating hydrothermal dynamics.Here,we aimed to test the role of alpine forest gap disturbance on total phenol loss(TPL)from the decomposing litter of two typical shrub species(willow,Salix paraplesia Schneid.,and bamboo,Fargesia nitida(Mitford)Keng f.).Methods We conducted a field litterbag experiment within a representative fir(Abies faxoniana Rehd.)forest based on‘gap openness treatments’(plot positions in the gap included the gap center south,gap center north,canopy edge,expanded edge and closed canopy).The TPL rate and litter surface microbial abundance(fungi and bacteria)of the two shrub species were measured during the following periods over 2 years:snow formation(SF),snow cover(SC),snow melting(ST),the early growing season(EG)and the late growing season(LG).Important Findings At the end of the study,we found that snow cover depth,freeze–thaw cycle frequency and the fungal copies g−1 to bacterial copies g−1 ratio had significant effects on litter TPL.The abundances of fungi and bacteria decreased from the gap center to the closed canopy during the SF,SC,ST and LG periods and showed the opposite trend during the EG periods.The rate of TPL among plot positions closely followed the same trend as microbial abundance during the first year of incubation.In addition,both species had higher rates of TPL in the gap center than at other positions during the first winter,first year and entire 2-year period.These findings suggest that alpine forest gap formation accelerates litter TPL,although litter TPL exhibits dual responses to gap disturbance during specific critical periods.In conclusion,reduced snow cover depth and duration during winter warming under projected climate change scenarios or as gaps vanish may slow litter TPL in alpine biomes.
基金supported through funds provided by Regione Calabria within the project"Robinwood Plus"-Interreg IV C
文摘Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to pre- serve bio- and pedo-diversity, influencing nutrient cycles, and maintain- ing the complex structure of the late-successional forests. Over the last 30 years, numerous reviews have been written describing gap dynamics. Here we synthesize current understanding on gap dynamics relating to tree regeneration with particular emphasis on gap characteristics consid- ered critical to develop ecologically sustainable forest management sys- tems and to conserve native biodiversity. Specifically, we addressed the question： how do gaps influence forest structure？ From the literature re- viewed, the size of gaps induces important changes in factors such as light intensity, soil humidity and soil biological properties that influence tree species regeneration and differ in gaps of different sizes. Shade- tolerant species can colonize small gaps; shade-intolerant species need large gaps for successful regeneration. Additionally, gap dynamics differ between temperate, boreal, and tropical forests, showing the importance of climate differences in driving forest regeneration. This review summa- rizes information of use to forest managers who design cutting regimes that mimic natural disturbances and who must consider forest structure, forest climate, and the role of natural disturbance in their designs.
文摘Many methods of restoration and rebuilding of forestry ecosystem were used, because the function of the secondary broad-leaved forests declined. one of these methods was the artificial regeneration carried out with gap technique in the forest. The results showed that the communities had been getting to Korean pine forests mixed with broad-leaved trees and the speed of development was much faster than before.
文摘With the concem of regcneration, characteristics of canopy gaps in broad-leaved Korean pine forest were studied.The areas of actual gap, expanded gap and maximum gap were analyzed respectively. The species composition, number, origin,decayed class and sizes of gap makers were studied comprehensively. The comparative studies of regencration inside and outside of canopy gap showed that the density of regeneration inside canopy gaps was 30% higher than that outside canopy gaps. The specific species regeneration response to canopy gap varied greatly. Pinus koraiensis, Picea jezoensis Frarinlis nla)ldshurica, JItghI)ls )nalJholu-i`a and Acer mono generally did not response to canopy gap disturbance. The Regeneration Importantce Valuc (RIV) of Abies nephrolepis, Ulmus Japonica increased with canopy gap disturbance. RIV of Tilia amurensis, Acer madshurica and Ulmus laciniata decreased with canopy gap disturbance. Canopy gap disturbance was not strong enough to result in the regeneration of some rpecies of shade intolerance such as Larix olgensis, Betula platyphylla.
基金supported by the Strategic Priority Research Program of the CAS(No.XDA05070306)the National Science&Technology Pillar Program in 12th 5-year Plan of China(No.2011BAC09B0402)
文摘We investigated non-structural carbohydrates（NSC） levels and components（starch,glucose,fructose and sucrose） in the leaves of three typical co-occurring forestfloor plants,moss Eurhynchium savatieri（ES）,fern Parathelypteris nipponica（PN） and forb Aruncus sylvester（AS） in a 30-year-old Chinese pine（Pinus tabulaeformis）plantation forest on the eastern Tibetan Plateau.We also explored their responses to three gap creation treatments（control and two gap creations of 80 and 110 m2） based on NSC levels.PN had the highest leaf NSC level of the three plants,with AS second and ES lowest.Starch was the predominant component of NSC and the contents of glucose were higher than those of fructose or sucrose for all three species.The NSC level of ES in intermediate gaps was significantly higher than at control sites.PN also had higher NSC levels in both small and intermediate gaps than in control sites.But the differences between treatments were not obvious for AS.Our results suggest that ES and PN benefit from gap formation while the two species have different NSC response sensitivities to gap size,but the leaf NSC level of AS is less sensitive to the disturbance.
基金We thank Mr. Liu Guangtian and the staff of Baiyinaobao Nature Reserve. This study was funded by the National Natural Science Foundation of China （Grant Nos. 39900019 and 30070129）. We thank Prof. Liao Liping for English corrections.
文摘Picea mongolica is an endemic but endangered species in China. The spruce forest is only found in sandy forest-steppe ecotones. In this study, we examined the initial response of the quantity and refilling process of free roots in an artificial canopy gap with a diameter of 36 m in a P. mongolica forest. Under the canopy, the fine root length densities of trees, shrubs and herbs were 2,622, 864 and 3,086 m·m^- 2, respectively. The free root biomass of trees, shrubs and herbs were 148, 62 and 65 g·m^- 2, respectively. In the gap, the fine root length density of trees was 151 m·m^- 2. The mean fine root densities of shrubs and herbs in the gap were 756 and 2,568 m·m^- 2. The fine root biomass of trees, shrubs and herbs were 9, 52 and 47 g·m^- 2, respectively. Two growing seasons after the gap creation, hardly any fine tree roots were found in the middle of the gap. The living tree roots in the gap edge zone were mainly located within a 4.5 m distance from the standing trees. Indices developed to show the influence of trees on free root length density clearly revealed the effect of the vicinity of living trees on fine root length density. The root densities of shrubs and herbs did not show a clear response to gap creation despite the increase of their foliage. Our results suggest that in P mongolica forests a gap disturbance creates a distinct tree root gap and that the gap edge trees do not extend their root systems rapidly into the formed root gap.
文摘Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and regeneration, and is an important indicator of forest management quality. The objective of this study was to compare gap fraction estimates from undisturbed forests and different environments or strata of selectively logged areas. Moreover, gap fraction measurements were collected with two distinct instruments (optical canopy analyzer LAI-2000 and hemispherical photographs). Field data were collected from two sustainable forest management sites at Jamari National Forest, Rondonia State, Brazilian Amazon. Our results indicated significant differences between data acquired using these two instruments. For instance, the LAI-2000 data showed greater variation for each environment compared to hemispherical photographics data, and the data were also more sensitive to the increase in gap fraction. Small variations were found in the gap fraction means for the two study areas, and only data for the undisturbed area were significantly different. A gradient of increasing gap fraction that ranged from primary forests to log decks was observed. Furthermore, a multiple linear regression analysis determined the contribution of the selectively logged environments to decreased forest cover, confirming the observed gradient.
基金This article was supported by State Tenth Five-Year Plan Project (2001BA510B0105) and the Project for Pioneering New Knowledge from Chinese Academy of Sciences (KZCX2-SW-319).
文摘Since 1950, 700 plots were established in the alpine and canyon region of western Sichuan. The distribution charac-teristics and the relationships between forest succession and environmental gradients were studied. The results showed that the main tree species were Picea and Abies in this region, and there were more than 90 forest types. Abies forests mainly dis-tributed in the middle and upper reaches of rivers and their branches, and Picea forests mainly distributed in wide valleys and on half-shaded and half-sunny slopes. The natural regeneration was poor under primitive spruce and fir forest canopy, but was good in the spruce and fire forest gap. The relationship between forest succession and vertical gradient was closely related to the relationship between forest succession procession and plant synusia under primary forests. Human activities could promote and postpone succession process. The results of expanding regeneration were often influenced by topography, vegetation and wind direction.
基金supported by grants from the National Basic Research Program of China(973 Program)(2012CB416906)National Nature Scientific Foundation of China(31330016)
文摘Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.
