WEST, J. B. AND L. A. DONOVAN. (Department of Plant Biology, University of Georgia, Athens, GA 30602). Effects of individual bunchgrasses on potential C and N mineralization of longleaf pine savanna soils.3 J. Torrey Bot. Soc. 131:120-125. 2004.-A recent conceptual model of grasslands in the US argues that, because of the discontinuous cover of plants in systems strongly limited by precipitation, the presence or absence of individual plants has significant effects on soil processes, with relatively small effects of species differences. In systems not strongly limited by precipitation, resource limitations are thought to vary in space and time, vegetation is more continuous, and species differences are relatively more important. We ask whether the model can be applied to grass species effects on potential net C and N mineralization in a southeastern US savanna ecosystem. These savannas have very sandy soils, strong soil resource limitations, and discontinuous plant cover, even though they receive 1200 mm yr-' rainfall. Based on the discontinuous herbaceous vegetation, an extension of the model would predict that native perennial bunchgrasses would have strong plant presence effects, and small or no species identity effects on these soil processes. Soils were sampled in a paired fashion, directly under a plant (either Aristida stricta, Schizachyrium scoparium, or Andropogon ternarius) and in adjacent unvegetated locations, and aboveground biomass was collected. Net C-min was significantly higher under plants compared to unvegetated locations, but there were also significant species identity effects, with the greatest rates observed under A. stricta. This pattern is likely explained by the greater biomass of A. stricta, because net C-min was positively related to biomass. For net N-min, there were neither plant presence nor species identity effects. There was, however, a positive relationship between net C-min and net N-min for both S. scoparium and A. ternarius soils, but not for A. stricta, suggesting a subtle, but potentially important, difference among species in their effects on N cycling. The results suggest that individual grasses have significant effects on soil processes in this system, but that the conceptual model developed for grasslands may not generalize to the effects of grasses on the soils of these savannas.
{"title":"Effects of individual bunchgrasses on potential C and N mineralization of longleaf pine savanna soils1","authors":"J. West, L. Donovan, J. Torrey","doi":"10.2307/4126913","DOIUrl":"https://doi.org/10.2307/4126913","url":null,"abstract":"WEST, J. B. AND L. A. DONOVAN. (Department of Plant Biology, University of Georgia, Athens, GA 30602). Effects of individual bunchgrasses on potential C and N mineralization of longleaf pine savanna soils.3 J. Torrey Bot. Soc. 131:120-125. 2004.-A recent conceptual model of grasslands in the US argues that, because of the discontinuous cover of plants in systems strongly limited by precipitation, the presence or absence of individual plants has significant effects on soil processes, with relatively small effects of species differences. In systems not strongly limited by precipitation, resource limitations are thought to vary in space and time, vegetation is more continuous, and species differences are relatively more important. We ask whether the model can be applied to grass species effects on potential net C and N mineralization in a southeastern US savanna ecosystem. These savannas have very sandy soils, strong soil resource limitations, and discontinuous plant cover, even though they receive 1200 mm yr-' rainfall. Based on the discontinuous herbaceous vegetation, an extension of the model would predict that native perennial bunchgrasses would have strong plant presence effects, and small or no species identity effects on these soil processes. Soils were sampled in a paired fashion, directly under a plant (either Aristida stricta, Schizachyrium scoparium, or Andropogon ternarius) and in adjacent unvegetated locations, and aboveground biomass was collected. Net C-min was significantly higher under plants compared to unvegetated locations, but there were also significant species identity effects, with the greatest rates observed under A. stricta. This pattern is likely explained by the greater biomass of A. stricta, because net C-min was positively related to biomass. For net N-min, there were neither plant presence nor species identity effects. There was, however, a positive relationship between net C-min and net N-min for both S. scoparium and A. ternarius soils, but not for A. stricta, suggesting a subtle, but potentially important, difference among species in their effects on N cycling. The results suggest that individual grasses have significant effects on soil processes in this system, but that the conceptual model developed for grasslands may not generalize to the effects of grasses on the soils of these savannas.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126913","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
endemic to North America and in the northern Rocky Mountains it occurs most abundantly in the understory of subalpine tree islands formed by Abies lasiocarpa and Picea engelmannii. This species reproduces almost entirely through apical fragment regeneration and its expansion into lower elevation sites may be dispersal limited. Mnium arizonicum was experimentally dispersed along an elevation gradient as apical fragments and colony transplants. Individual performance was expected to interact with factors that vary with elevation such as habitat characteristics and competition intensity. Habitat characteristics were assessed at the site level by detailed site mapping and at the scale of the study area by restricted-random 5 m radius plots. The interaction between M. arizonicum and Hylocomium splendens was investigated for a switch from competition to facilitation along the elevation gradient. The experimental design included six elevation classes with three replicate sites and within each site two microsites (Picea tree base and Hylocomium carpet) each with three replicate plots. At sites where M. arizonicum was most abundant, it was excluded from the smallest tree islands with higher tree densities. In the region of the study area, the occurrence of M. arizonicum was most probable around tree bases located at 2000+ m with a thin (< 3 cm) litter layer and with one or more other bryophyte species present at the same tree base. The effects of microsite (Picea base versus Hylocomium carpet) on M. arizonicum performance were clearer in both life stages than the effects of elevation. Hylocomium microsites had consistently lower regeneration of apical fragments, but higher in situ effective quantum yield of adult transplants compared with Picea bases. Within the Picea base microsites, plots at intermediate elevations (1600-1800 m) received more light and were sub-optimal in terms of fragment regeneration, fragment sprout production, and in situ effective quantum yield of adult transplants. In the study area, the ability of M. arizonicum to extend its range into lower elevation sites was limited at intermediate elevations around tree bases that had deeper litter layers at intermediate elevation sites and in Hylocomium microsites by competitive pressure from this dominant forest floor moss.
{"title":"Controls on the distribution of Mnium arizonicum along an elevation gradient in the Front Ranges of the Rocky Mountains, Alberta1","authors":"N. Cleavitt","doi":"10.2307/4126916","DOIUrl":"https://doi.org/10.2307/4126916","url":null,"abstract":"endemic to North America and in the northern Rocky Mountains it occurs most abundantly in the understory of subalpine tree islands formed by Abies lasiocarpa and Picea engelmannii. This species reproduces almost entirely through apical fragment regeneration and its expansion into lower elevation sites may be dispersal limited. Mnium arizonicum was experimentally dispersed along an elevation gradient as apical fragments and colony transplants. Individual performance was expected to interact with factors that vary with elevation such as habitat characteristics and competition intensity. Habitat characteristics were assessed at the site level by detailed site mapping and at the scale of the study area by restricted-random 5 m radius plots. The interaction between M. arizonicum and Hylocomium splendens was investigated for a switch from competition to facilitation along the elevation gradient. The experimental design included six elevation classes with three replicate sites and within each site two microsites (Picea tree base and Hylocomium carpet) each with three replicate plots. At sites where M. arizonicum was most abundant, it was excluded from the smallest tree islands with higher tree densities. In the region of the study area, the occurrence of M. arizonicum was most probable around tree bases located at 2000+ m with a thin (< 3 cm) litter layer and with one or more other bryophyte species present at the same tree base. The effects of microsite (Picea base versus Hylocomium carpet) on M. arizonicum performance were clearer in both life stages than the effects of elevation. Hylocomium microsites had consistently lower regeneration of apical fragments, but higher in situ effective quantum yield of adult transplants compared with Picea bases. Within the Picea base microsites, plots at intermediate elevations (1600-1800 m) received more light and were sub-optimal in terms of fragment regeneration, fragment sprout production, and in situ effective quantum yield of adult transplants. In the study area, the ability of M. arizonicum to extend its range into lower elevation sites was limited at intermediate elevations around tree bases that had deeper litter layers at intermediate elevation sites and in Hylocomium microsites by competitive pressure from this dominant forest floor moss.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126916","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
seedlings of the montane C. pseudophrygia and the closely related, widely distributed C. jacea revealed similar growth patterns and nearly the same damage, and therefore gave no indication that the lower altitudinal distribution limit of C. pseudophrygia may be caused by a more severe seedling herbivory. In contrast to Centaurea, the highly palatable Arnica montana seedlings were completely consumed within a few days after transplantation, irrespective of age class and without any regeneration events, supporting previous hypotheses that mollusk herbivory is a limiting factor for the geographical range of Arnica montana. In general, the results confirm that a high sampling resolution in time is of great importance to detect agespecific mortality factors in plant population studies.
{"title":"Age-specific and season-specific mollusk damage to seedlings of grassland Asteraceael","authors":"U. Scheidel, H. Bruelheide, H. Bruelheide","doi":"10.2307/4126915","DOIUrl":"https://doi.org/10.2307/4126915","url":null,"abstract":"seedlings of the montane C. pseudophrygia and the closely related, widely distributed C. jacea revealed similar growth patterns and nearly the same damage, and therefore gave no indication that the lower altitudinal distribution limit of C. pseudophrygia may be caused by a more severe seedling herbivory. In contrast to Centaurea, the highly palatable Arnica montana seedlings were completely consumed within a few days after transplantation, irrespective of age class and without any regeneration events, supporting previous hypotheses that mollusk herbivory is a limiting factor for the geographical range of Arnica montana. In general, the results confirm that a high sampling resolution in time is of great importance to detect agespecific mortality factors in plant population studies.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126915","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Kelsall, C. Hazard, D. Leopold, C. Hazard, D. Leopold, J. Torrey
KELSALL, N., C. HAZARD, AND D. J. LEOPOLD (Department of Environmental and Forest Biology, SUNY College of Environmental Science and Forestry, 1 Forestry Drive Syracuse, New York 13210). Influence of climate factors on demographic changes in the New York populations of the federally-listed Phyllitis scolopendrium (L.) Newm. var. americana J. Torrey Bot. Soc. 131:161-168. 2004.-Approximately 92% of the U.S. population of American hart's-tongue fern (Phyllitis scolopendrium var. americana) is found in Onondaga and Madison counties, New York, in 17 distinct colonies. All New York colonies have been periodically censused since 1916, though rarely in the same year. This study examines census data of the total New York population during and following the severe drought of 1999 and during the summers of 2000 and 2002. Additionally, the long-term (1922-2002) census data of seven colonies are examined relative to climate data for the same period. The total New York population has declined overall since the last previous census in 1995. No climate variables explained more than 23% of variation in population size of any growth phase. The lack of controlling, largescale climate factors suggests that the distribution of hart's-tongue fern in New York is determined mostly by the occurence of habitat capable of buffering climatic fluctuations. Future work should combine small-scale habitat and large-scale climate factors in any analysis.
KELSALL, N. C. HAZARD, AND D. J. LEOPOLD(环境与森林生物系，纽约州立大学环境科学与林业学院，1 Forestry Drive Syracuse, New York 13210)。气候因素对联邦上市的白桦纽约种群人口变化的影响Newm。美国作家j·托里·博特。Soc。131:161 - 168。2004.在美国，大约92%的美洲鹿舌蕨(Phyllitis scolopendrium var. americana)分布在纽约州的奥农达加和麦迪逊县，分布在17个不同的殖民地。自1916年以来，所有纽约殖民地都定期进行人口普查，尽管很少在同一年进行。这项研究检查了1999年严重干旱期间和之后以及2000年和2002年夏季纽约总人口的人口普查数据。此外，将七个殖民地的长期(1922-2002)人口普查数据与同期的气候数据进行了比较。自1995年上次人口普查以来，纽约总人口总体上有所下降。在任何生长阶段，气候变量都不能解释超过23%的种群大小变化。由于缺乏具有控制作用的大尺度气候因子，这表明纽约的鹿舌蕨的分布主要是由能够缓冲气候波动的栖息地的出现所决定的。未来的工作应在任何分析中结合小尺度生境和大尺度气候因子。
{"title":"Influence of climate factors on demographic changes in the New York populations of the federally-listed Phyllitis scolopendrium (L.) Newm. var. americana","authors":"N. Kelsall, C. Hazard, D. Leopold, C. Hazard, D. Leopold, J. Torrey","doi":"10.2307/4126917","DOIUrl":"https://doi.org/10.2307/4126917","url":null,"abstract":"KELSALL, N., C. HAZARD, AND D. J. LEOPOLD (Department of Environmental and Forest Biology, SUNY College of Environmental Science and Forestry, 1 Forestry Drive Syracuse, New York 13210). Influence of climate factors on demographic changes in the New York populations of the federally-listed Phyllitis scolopendrium (L.) Newm. var. americana J. Torrey Bot. Soc. 131:161-168. 2004.-Approximately 92% of the U.S. population of American hart's-tongue fern (Phyllitis scolopendrium var. americana) is found in Onondaga and Madison counties, New York, in 17 distinct colonies. All New York colonies have been periodically censused since 1916, though rarely in the same year. This study examines census data of the total New York population during and following the severe drought of 1999 and during the summers of 2000 and 2002. Additionally, the long-term (1922-2002) census data of seven colonies are examined relative to climate data for the same period. The total New York population has declined overall since the last previous census in 1995. No climate variables explained more than 23% of variation in population size of any growth phase. The lack of controlling, largescale climate factors suggests that the distribution of hart's-tongue fern in New York is determined mostly by the occurence of habitat capable of buffering climatic fluctuations. Future work should combine small-scale habitat and large-scale climate factors in any analysis.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126917","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Evans, J. Pancrudo, K. Lagrazon, Z. Kahn-Jetter, B. Litkouhi
to being separated from the plant. Bending stress (due solely to the weight of the branches) was the predominant stress (mean bending stresses were 167 and 383 kPa for 0. ficus-indica and 0. parryi var. parryi, respectively) between stem segments. Axial, shear, and torsion stresses were relatively low compared with bending stresses for both species. Data of 0. ficus-indica and 0. parryi var. parryi show that 23.6 and 25.3% of tensile portions of joints were composed of lignified xylem cells, respectively, while compressive portions of the same joints had only 10.8 and 14.7% lignified xylem cells, respectively. The relative radial positions of lignified xylem cells for compressive, tensile and lateral portions of joints for 0. ficus-indica and 0. parryi var. parryi were analyzed. In general, lignified xylem cells were closer to the external surface in tensile tissues than in compressive and lateral tissues of joints. Thus, lignified xylem cells are located in a position to provide a high level of resistance to bending. Maximum bending stresses were positively related with amounts of lignified xylem cells in joints for both species. For 0. ficus-indica the best-fit line was y = 1.48 x + 24.2 (P = 0.012) with an r2 = 0.76. For 0. parryi var. parryi, the best-fit line was y = 54.0 x - 11.7 (P = 0.01) with an r2 = 0.92. The 1.48 slope value for 0. ficus-indica was low compared with the 54.0 slope value for 0. parryi var. parryi. Large slope values for a species may reflect a greater ability of lignified xylem cells to resist stress. In five Opuntia species for which data are available, there was a strong negative relationship between slope values and joint diameter. However, high slope values occurred in species with more horizontal stem segments. Overall, these results show bending stress is the main stress between stem segments, lignified xylem cells in stem joints provide the main resistance to joint stresses, and slope values of stress versus amounts of lignified xylem cells may be related to plant morphology.
与植物分离。弯曲应力(仅由于树枝的重量)是主要应力(平均弯曲应力为167和383 kPa)。Ficus-indica和0。茎节之间的分枝(分别为分枝)。与弯曲应力相比，两种物种的轴向、剪切和扭转应力相对较低。数据为0。Ficus-indica和0。Parryi var. Parryi结果表明，同一节理的拉伸部分木质部细胞木质化比例分别为23.6%和25.3%，而压缩部分木质部细胞木质化比例分别为10.8%和14.7%。木质化木质部细胞在关节的压缩、拉伸和侧向部分的相对径向位置为0。Ficus-indica和0。对Parryi和Parryi进行了分析。总的来说，木质部细胞在关节的拉伸组织中比在压缩组织和外侧组织中更靠近外表面。因此，木质化的木质部细胞位于提供高水平抗弯曲的位置。两种植物的最大弯曲应力与关节木质部木质化细胞的数量呈正相关。为0。ficus-indica的最佳拟合线为y = 1.48 x + 24.2 (P = 0.012)， r2 = 0.76。为0。最佳拟合线为y = 54.0 x - 11.7 (P = 0.01)， r2 = 0.92。1.48的斜率值为0。与54.0坡度值相比，榕树指数较低。Parryi var, Parryi。一个物种的大斜率值可能反映木质化木质部细胞抵抗压力的能力更强。在已有资料的5种机会种中，坡值与关节直径之间存在较强的负相关关系。然而，高斜率值出现在茎段水平的物种中。总的来说，这些结果表明，弯曲应力是茎节之间的主要应力，茎节中木质化的木质部细胞提供了对关节应力的主要抵抗能力，并且应力与木质化木质部细胞数量的斜率值可能与植物形态有关。
{"title":"Compressive/tensile stresses and lignified cells as resistance components in joints of Opuntia ficus-indica and Opuntia parryi var. parryi (Cactaceae)","authors":"L. Evans, J. Pancrudo, K. Lagrazon, Z. Kahn-Jetter, B. Litkouhi","doi":"10.2307/4126912","DOIUrl":"https://doi.org/10.2307/4126912","url":null,"abstract":"to being separated from the plant. Bending stress (due solely to the weight of the branches) was the predominant stress (mean bending stresses were 167 and 383 kPa for 0. ficus-indica and 0. parryi var. parryi, respectively) between stem segments. Axial, shear, and torsion stresses were relatively low compared with bending stresses for both species. Data of 0. ficus-indica and 0. parryi var. parryi show that 23.6 and 25.3% of tensile portions of joints were composed of lignified xylem cells, respectively, while compressive portions of the same joints had only 10.8 and 14.7% lignified xylem cells, respectively. The relative radial positions of lignified xylem cells for compressive, tensile and lateral portions of joints for 0. ficus-indica and 0. parryi var. parryi were analyzed. In general, lignified xylem cells were closer to the external surface in tensile tissues than in compressive and lateral tissues of joints. Thus, lignified xylem cells are located in a position to provide a high level of resistance to bending. Maximum bending stresses were positively related with amounts of lignified xylem cells in joints for both species. For 0. ficus-indica the best-fit line was y = 1.48 x + 24.2 (P = 0.012) with an r2 = 0.76. For 0. parryi var. parryi, the best-fit line was y = 54.0 x - 11.7 (P = 0.01) with an r2 = 0.92. The 1.48 slope value for 0. ficus-indica was low compared with the 54.0 slope value for 0. parryi var. parryi. Large slope values for a species may reflect a greater ability of lignified xylem cells to resist stress. In five Opuntia species for which data are available, there was a strong negative relationship between slope values and joint diameter. However, high slope values occurred in species with more horizontal stem segments. Overall, these results show bending stress is the main stress between stem segments, lignified xylem cells in stem joints provide the main resistance to joint stresses, and slope values of stress versus amounts of lignified xylem cells may be related to plant morphology.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126912","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ST. DENIS, M. AND N. CAPPUCCINO (Department of Biology, Carleton University, Ottawa, Ontario, K1S 5B6 Canada). Reproductive biology of Vincetoxicum rossicum (Kleo.) Barb. (Asclepiadaceae), an invasive alien in Ontario. J. TORREY BOT. SOC. 131:8-15. 2004.-We investigated the reproductive biology of the alien invasive vine Vincetoxicum rossicum (Asclepiadaceae) and evaluated pollinator visitation rate in the field, evidenced by missing pollinaria, to flowers of isolated plants and those of plants in dense monocultures. Flowers in dense monocultures were visited less frequently than those on isolated plants surrounded by old-field grasses. Visited flowers were more likely to produce fruit and those fruits contained more polyembryonic seeds. However, a greenhouse experiment in which we crossor self-pollinated flowers revealed no difference in fruit set, seed production, seed weight or embryony. This suggests that the higher fruit set and greater polyembryony of visited flowers in the field was not the consequence of visitation, but may have been the result of floral visitors having chosen the most vigorous flowers. Day-old flowers emasculated in the greenhouse experiment occasionally produced a fruit, indicating that the germination of self-pollen begins the day a flower opens. The ability to produce large numbers of selfed seeds is no doubt advantageous to this highly invasive asclepiad.
ST. DENIS, M. AND N. CAPPUCCINO(卡尔顿大学生物系，渥太华，安大略省，K1S 5B6 Canada)。长春花的生殖生物学研究倒钩。(Asclepiadaceae)，一种入侵安大略省的外来植物。j·托里·博特。SOC。131:8-15。2004.-研究了外来入侵藤本植物长春花(winectoxicum rosicum, Asclepiadaceae)的生殖生物学特性，并评估了野外传粉者对孤立植物和密集单一栽培植物花的访花率(以缺失传粉者为证据)。在密集的单一栽培植物上的花被访问的频率低于那些被老草地包围的孤立植物上的花。拜访过的花更容易结出果实，果实中含有更多的多胚种子。然而，在自花授粉的温室实验中，我们发现在坐果、种子产量、种子重量或胚胎方面没有差异。这表明，田间访花的高坐果率和多胚率不是访花的结果，而可能是访花者选择了最旺盛的花的结果。在温室实验中，被阉割了一天的花偶尔会结出果实，这表明自花开花的那天起，自花花粉就开始发芽了。产生大量自交种子的能力无疑对这种高度侵入性的植物是有利的。
{"title":"Reproductive biology of Vincetoxicum rossicum (Kleo.) Barb. (Asclepiadaceae), an invasive alien in Ontario'","authors":"M. Denis, N. Cappuccino","doi":"10.2307/4126923","DOIUrl":"https://doi.org/10.2307/4126923","url":null,"abstract":"ST. DENIS, M. AND N. CAPPUCCINO (Department of Biology, Carleton University, Ottawa, Ontario, K1S 5B6 Canada). Reproductive biology of Vincetoxicum rossicum (Kleo.) Barb. (Asclepiadaceae), an invasive alien in Ontario. J. TORREY BOT. SOC. 131:8-15. 2004.-We investigated the reproductive biology of the alien invasive vine Vincetoxicum rossicum (Asclepiadaceae) and evaluated pollinator visitation rate in the field, evidenced by missing pollinaria, to flowers of isolated plants and those of plants in dense monocultures. Flowers in dense monocultures were visited less frequently than those on isolated plants surrounded by old-field grasses. Visited flowers were more likely to produce fruit and those fruits contained more polyembryonic seeds. However, a greenhouse experiment in which we crossor self-pollinated flowers revealed no difference in fruit set, seed production, seed weight or embryony. This suggests that the higher fruit set and greater polyembryony of visited flowers in the field was not the consequence of visitation, but may have been the result of floral visitors having chosen the most vigorous flowers. Day-old flowers emasculated in the greenhouse experiment occasionally produced a fruit, indicating that the germination of self-pollen begins the day a flower opens. The ability to produce large numbers of selfed seeds is no doubt advantageous to this highly invasive asclepiad.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126923","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
NORDEN, A. H. AND L. K. KIRKMAN (J. W. Jones Ecological Research Center, Rt. 2 Box 2324, Newton, GA 39870-9651). Factors controlling the fire-induced flowering response of the federally endangered Schwalbea americana L. (Scrophulariaceae). J. Torrey Bot. Soc. 131:16-22. 2004.-The fire-maintained longleaf pine ecosystem of the southeastern Coastal Plain harbors nearly 200 rare and endangered plant species, many of which depend on frequent fire for persistence. One such fire-dependent species is the federally endangered hemiparasite, Schwalbea americana L. (Scrophulariaceae). Regardless of season of burn, fire stimulates flowering and subsequent seed production in this species, but the specific mechanisms involved in this fire-induced flowering response are unknown. The purpose of this study was to determine the factors controlling the flowering response to fire. Using experimental treatments in the field and greenhouse, we examined the effect of variables associated with fire that may influence flowering of S. americana. Our field treatments included fire, shading immediately following fire, stem clipping plus competing vegetation exclusion, and mowing plus raking. Greenhouse treatments consisted of a gradient of light levels plus stem clipping. Our findings indicate that flowering, and subsequent viable seed production, is stimulated by a combination of clipping and increased light. These results suggest alternative management options for S. americana during years in which prescribed fire is not feasible. If prescribed fire is not an option, we suggest that mowing plus raking could be used as a temporary means to stimulate flowering and promote seed production and future seedling establishment.
(J. W. Jones生态研究中心，39870-9651室)。联邦濒危植物美洲雪豆(Schwalbea americana L.)火致开花响应的控制因素托里·博特。131:16-22 Soc。2004.东南沿海平原的长叶松生态系统中有近200种稀有和濒危植物，其中许多物种依赖频繁的火灾来生存。其中一种依赖火的物种是联邦濒危的半寄生虫，Schwalbea americana L.(螺旋藻科)。无论燃烧的季节如何，火都会刺激该物种的开花和随后的种子生产，但这种火诱导的开花反应的具体机制尚不清楚。本研究的目的是确定控制开花对火的反应的因素。通过田间和温室的试验处理，研究了与火有关的变量对美洲杉开花的影响。我们的田间处理包括火，火后立即遮阳，茎剪加竞争植被排除，割加耙。温室处理包括光照梯度和茎剪。我们的研究结果表明，修剪和增加光照的结合刺激了开花和随后的可存活种子生产。这些结果表明，在规定的火灾不可行的年份，美洲杉的其他管理方案。如果不能选择规定的火，我们建议割草加耙可以作为一种临时手段来刺激开花，促进种子生产和未来的幼苗建立。
{"title":"Factors controlling the fire-induced flowering response of the federally endangered Schwalbea americana L. (Scrophulariaceae)1","authors":"A. H. Norden, L. Kirkman, J. Jones, L. Kirkman","doi":"10.2307/4126924","DOIUrl":"https://doi.org/10.2307/4126924","url":null,"abstract":"NORDEN, A. H. AND L. K. KIRKMAN (J. W. Jones Ecological Research Center, Rt. 2 Box 2324, Newton, GA 39870-9651). Factors controlling the fire-induced flowering response of the federally endangered Schwalbea americana L. (Scrophulariaceae). J. Torrey Bot. Soc. 131:16-22. 2004.-The fire-maintained longleaf pine ecosystem of the southeastern Coastal Plain harbors nearly 200 rare and endangered plant species, many of which depend on frequent fire for persistence. One such fire-dependent species is the federally endangered hemiparasite, Schwalbea americana L. (Scrophulariaceae). Regardless of season of burn, fire stimulates flowering and subsequent seed production in this species, but the specific mechanisms involved in this fire-induced flowering response are unknown. The purpose of this study was to determine the factors controlling the flowering response to fire. Using experimental treatments in the field and greenhouse, we examined the effect of variables associated with fire that may influence flowering of S. americana. Our field treatments included fire, shading immediately following fire, stem clipping plus competing vegetation exclusion, and mowing plus raking. Greenhouse treatments consisted of a gradient of light levels plus stem clipping. Our findings indicate that flowering, and subsequent viable seed production, is stimulated by a combination of clipping and increased light. These results suggest alternative management options for S. americana during years in which prescribed fire is not feasible. If prescribed fire is not an option, we suggest that mowing plus raking could be used as a temporary means to stimulate flowering and promote seed production and future seedling establishment.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126924","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. rubrum, 0.7 for F. americana, vs. 0 to 0.02 for the shrubs). For the trees, but not the shrubs, both seed input and seedling emergence in the fields showed a strong relationship to seed source abundance along the field edges, using index values based on the distances from potential source plants. Results of seed augmentation experiments showed that seedling emergence was strongly limited by seed input, but secondarily by environment; more C. racemosa emerged in moister plots and more F. americana and V. dentatum under short vegetation. Once established, seedlings of the shrubs often survived better and grew faster than did the tree seedlings. As a result of net overall differences in seedling emergence and survival, the number of seeds required to get one surviving fifth-year seedling was lowest for the shrubs (20 to 35 seeds), somewhat higher for F. americana (55), and highest for A. rubrum (326).
{"title":"Colonization of old fields by trees vs. shrubs: seed dispersal and seedling establishment1","authors":"S. Gardescu, P. Marks","doi":"10.2307/4126928","DOIUrl":"https://doi.org/10.2307/4126928","url":null,"abstract":"A. rubrum, 0.7 for F. americana, vs. 0 to 0.02 for the shrubs). For the trees, but not the shrubs, both seed input and seedling emergence in the fields showed a strong relationship to seed source abundance along the field edges, using index values based on the distances from potential source plants. Results of seed augmentation experiments showed that seedling emergence was strongly limited by seed input, but secondarily by environment; more C. racemosa emerged in moister plots and more F. americana and V. dentatum under short vegetation. Once established, seedlings of the shrubs often survived better and grew faster than did the tree seedlings. As a result of net overall differences in seedling emergence and survival, the number of seeds required to get one surviving fifth-year seedling was lowest for the shrubs (20 to 35 seeds), somewhat higher for F. americana (55), and highest for A. rubrum (326).","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126928","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GRIFFITHS M. E. AND C. M. ORIANS (Department of Biology, Tufts University, Medford, MA 02155). Salt spray effects on forest succession in rare coastal sandplain heathlands: evidence from field surveys and Pinus rigida transplant experiments. J. Torrey Bot. Soc. 131: 23-31. 2004.-Coastal sandplain heathland is a rare ecosystem maintained by recurrent disturbances and chronic abiotic stress. In areas with low disturbance or stress, heathland communities are succeeded by tree species, such as Pinus rigida, that outcompete native heathland plants. We propose that salt spray is an important natural abiotic stress factor that helps to maintain heathlands near the coast by slowing tree succession. We investigated whether salt spray inhibits succession in heathlands on Martha's Vineyard, Massachusetts, by surveying natural field distributions of species and by quantifying the survival and growth of P rigida seedlings transplanted at different distances from the ocean. Tree species did not grow in areas with high salt spray and multivariate analyses identified salt spray as an important ecological factor influencing species distributions in coastal heathlands. Although transplanted P. rigida seedlings exhibited low mortality close to the ocean, they exhibited higher water stress and needle necrosis as well as inhibition of growth, suggesting that salt spray may be important in suppressing trees close to the
{"title":"Salt spray effects on forest succession in rare coastal sandplain heathlands: evidence from field surveys and Pinus rigida transplant experiments'","authors":"M. Griffiths, C. Orians, M. Griffiths","doi":"10.2307/4126925","DOIUrl":"https://doi.org/10.2307/4126925","url":null,"abstract":"GRIFFITHS M. E. AND C. M. ORIANS (Department of Biology, Tufts University, Medford, MA 02155). Salt spray effects on forest succession in rare coastal sandplain heathlands: evidence from field surveys and Pinus rigida transplant experiments. J. Torrey Bot. Soc. 131: 23-31. 2004.-Coastal sandplain heathland is a rare ecosystem maintained by recurrent disturbances and chronic abiotic stress. In areas with low disturbance or stress, heathland communities are succeeded by tree species, such as Pinus rigida, that outcompete native heathland plants. We propose that salt spray is an important natural abiotic stress factor that helps to maintain heathlands near the coast by slowing tree succession. We investigated whether salt spray inhibits succession in heathlands on Martha's Vineyard, Massachusetts, by surveying natural field distributions of species and by quantifying the survival and growth of P rigida seedlings transplanted at different distances from the ocean. Tree species did not grow in areas with high salt spray and multivariate analyses identified salt spray as an important ecological factor influencing species distributions in coastal heathlands. Although transplanted P. rigida seedlings exhibited low mortality close to the ocean, they exhibited higher water stress and needle necrosis as well as inhibition of growth, suggesting that salt spray may be important in suppressing trees close to the","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126925","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Angela T. Darwin, D. Ladd, Robert Galdins, Thomas A. Contreras, L. Fahrig
DARWIN, A.T., D. LADD, R. GALDINS, T. A. CONTRERAS AND L. FAHRIG (Dept. of Biol., Carleton University, Ottawa, ON, Canada KiS 5B6). Response of forest understory vegetation to a major ice storm. J. Torrey Bot. Soc. 131:45-52. 2004.-In January of 1998, Ottawa, Ontario was hit with a major ice storm. Detailed pre-storm vegetation data had been collected in 1997 in 164 forest interior sampling plots across a 3,000 km2 region. These data included information on shrubs/saplings, woody seeds and seedlings, herbaceous seeds and ground cover, and canopy cover. For the four growing seasons following the ice storm (1998-2001), we resampled the same 164 plots. In addition, in 1998 we estimated an ice storm damage index for each plot, and the volume of downed coarse woody debris due to the ice storm in each plot. The objectives of this paper were to examine changes in shrubs/saplings and ground vegetation in response to ice storm damage over the four-year period following the storm. Contrary to our initial expectations, we found that woody seedlings showed a large decrease in density immediately following the storm (1998). Woody seedling density recovered to pre-storm levels by 2001. We hypothesize that the decrease in woody seedling density resulted from reduced seedling germination due to lower light availability on the forest floor, which resulted from the large amount of woody debris created by the storm. We also found that shrub/sapling counts showed a large increase in 1999, most likely due to increased light to the understory, due to opening of the upper canopy. Herbaceous cover increased from 1998 to 2000, but returned to pre-storm levels the following year (2001). The between-plot variation in these understory changes was positively correlated to plot damage from the ice storm, indicating that they resulted from the storm. Overall, it appears that the forest understory plant structure is rapidly returning to pre-ice storm conditions.
{"title":"Response of forest understory vegetation to a major ice storm","authors":"Angela T. Darwin, D. Ladd, Robert Galdins, Thomas A. Contreras, L. Fahrig","doi":"10.2307/4126927","DOIUrl":"https://doi.org/10.2307/4126927","url":null,"abstract":"DARWIN, A.T., D. LADD, R. GALDINS, T. A. CONTRERAS AND L. FAHRIG (Dept. of Biol., Carleton University, Ottawa, ON, Canada KiS 5B6). Response of forest understory vegetation to a major ice storm. J. Torrey Bot. Soc. 131:45-52. 2004.-In January of 1998, Ottawa, Ontario was hit with a major ice storm. Detailed pre-storm vegetation data had been collected in 1997 in 164 forest interior sampling plots across a 3,000 km2 region. These data included information on shrubs/saplings, woody seeds and seedlings, herbaceous seeds and ground cover, and canopy cover. For the four growing seasons following the ice storm (1998-2001), we resampled the same 164 plots. In addition, in 1998 we estimated an ice storm damage index for each plot, and the volume of downed coarse woody debris due to the ice storm in each plot. The objectives of this paper were to examine changes in shrubs/saplings and ground vegetation in response to ice storm damage over the four-year period following the storm. Contrary to our initial expectations, we found that woody seedlings showed a large decrease in density immediately following the storm (1998). Woody seedling density recovered to pre-storm levels by 2001. We hypothesize that the decrease in woody seedling density resulted from reduced seedling germination due to lower light availability on the forest floor, which resulted from the large amount of woody debris created by the storm. We also found that shrub/sapling counts showed a large increase in 1999, most likely due to increased light to the understory, due to opening of the upper canopy. Herbaceous cover increased from 1998 to 2000, but returned to pre-storm levels the following year (2001). The between-plot variation in these understory changes was positively correlated to plot damage from the ice storm, indicating that they resulted from the storm. Overall, it appears that the forest understory plant structure is rapidly returning to pre-ice storm conditions.","PeriodicalId":49977,"journal":{"name":"Journal of the Torrey Botanical Society","volume":null,"pages":null},"PeriodicalIF":0.3,"publicationDate":"2004-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2307/4126927","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69302824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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