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Shenglei Fu - One of the best experts on this subject based on the ideXlab platform.
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effect of Understory fern dicranopteris dichotoma removal on substrate utilization patterns of culturable soil bacterial communities in subtropical eucalyptus plantations
Pedobiologia, 2012Co-Authors: Lixia Zhou, Jianping Wu, Shenglei FuAbstract:a b s t r a c t Although Understory vegetation is known to play an important role in driving the processes and func- tions of forest ecosystems, little is known about how Understory vegetation affects the composition and function of soil microbial communities in forest ecosystems, especially in subtropical and tropical forests. This study used the experimental removal of Understory fern (Dicranopteris dichotoma) to investigate the effect of the fern on substrate utilization patterns of culturable soil bacterial communities in two sub- tropical Eucalyptus plantations. One year after treatment, the removal of Understory fern significantly increased soil temperature by 2-3 ◦ C and retarded litter decomposition by 5.6-23.1%. However, under- story fern removal did not affect the substrate utilization pattern of soil bacterial communities. Our study provides evidence that, although Understory fern removal significantly alters soil temperature and litter decomposition rate, the disturbance caused by Understory removal one year after treatment is too weak to cause detectable changes in substrate utilization pattern of culturable soil bacterial communities in subtropical Eucalyptus plantations.
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effects of Understory removal and tree girdling on soil microbial community composition and litter decomposition in two eucalyptus plantations in south china
Functional Ecology, 2011Co-Authors: Jianping Wu, Lixia Zhou, Xiaoling Wang, Shenglei FuAbstract:Summary 1. Soil micro-organisms play important roles in ecosystems and respond quickly to environmental changes. We examined how Understory removal and tree girdling influence the composition of soil microbial community and the litter decomposition in two subtropical plantations. 2. Phospholipid fatty acids (PLFAs) analysis was used to characterize soil microbial community. Redundancy analysis and principal response curves (PRC) were used to investigate the relationships between soil microbial community and environmental factors. 3. Understory removal significantly reduced the amount of fungal PLFAs, the ratio of fungal to bacterial PLFAs, and the litter decomposition but did not affect bacterial PLFAs and total PLFAs. In contrast, tree girdling did not affect the soil microbial characteristics. The changes in soil microbial community caused by Understory removal were mainly attributed to the indirect effects such as increased soil temperature and soil NO3 ) -N availability. In addition, PRC analysis showed that the relative abundance of most PLFAs increased in response to Understory removal in the 2-year-old plantation but decreased in the 24-year-old plantation. 4. We propose that Understory plants are important components in subtropical forest ecosystems, and play different roles in maintaining soil microbial community and driving litter decomposition processes in young vs. old plantations. The functions of Understory plants should be considered in forest management and restoration. The negligible effect of tree girdling on the soil micro-organisms can be attributed to the resprouting trait and mycorrhizal interactions of Eucalyptus.
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impacts of Understory species removal and or addition on soil respiration in a mixed forest plantation with native species in southern china
Forest Ecology and Management, 2011Co-Authors: Xiaoling Wang, Lixia Zhou, Jianping Wu, Jie Zhao, Hua Chen, Shenglei FuAbstract:Abstract Although the removal or addition of Understory vegetation has been an important forest management practice in forest plantations, the effects of this management practice on soil respiration are unclear. The overall objective of this study was to measure and model soil respiration and its components in a mixed forest plantation with native species in south China and to assess the effects of Understory species management on soil respiration and on the contribution of root respiration (Rr) to total soil respiration (Rs). An experiment was conducted in a plantation containing a mixture of 30 native tree species and in which Understory plants had been removed or replaced by Cassia alata Linn. The four treatments were the control (Control), C. alata addition (CA), Understory removal (UR) and Understory removal with C. alata addition (UR + CA). Trenched subplots were used to quantify Rr by comparing Rs outside the 1-m2 trenched subplots (plants and roots present) and inside the trenched subplots (plants and roots absent) in each treatment. Annual soil respiration were modeled using the values measured for Rs, soil temperature and soil moisture. Our results indicate that Understory removal reduced Rs rate and soil moisture but increased soil temperature. Regression models revealed that soil temperature was the main factor and soil moisture was secondary. Understory manipulations and trenching increased the temperature sensitivity of Rs. Annual Rs for the Control, CA, UR and UR + CA treatments averaged 594, 718, 557 and 608 g C m−2 yr−1, respectively. UR decreased annual Rs by 6%, but CA increased Rs by about 21%. Our results also indicate that management of Understory species increased the contribution of Rr to Rs.
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impacts of litter and Understory removal on soil properties in a subtropical acacia mangium plantation in china
Plant and Soil, 2008Co-Authors: Yanmei Xiong, Zhian Li, Shenglei FuAbstract:In forest ecosystems, the effects of litter or Understory on soil properties are far from being fully understood. We conducted a study in a pure Acacia mangium Willd. plantation in southern China, by removing litter or Understory or both components and then comparing these treatments with a control (undisturbed), to evaluate their respective effects on soil physical, chemical and biological properties. In addition, a litter decomposition experiment was conducted to understand the effects of Understory on litter decomposition. Our data showed that the presence of Understory favored litter decomposition to a large extent. In 1 year, 75.2 and 37.2% of litter were decomposed in the control and Understory removal treatment (UR), respectively. Litter had a profound significance in retaining soil water and contributing to soil fertility, including organic matter (OM), available phosphorus (P) and alkali-hydrolyzable nitrogen (N), but Understory exerted less influence than litter on soil physical and chemical properties. Both litter and Understory played an important role in soil biological activity as indicated by microbial biomass carbon (MBC), while there were no significant impacts on soil exchangeable potassium (K) after either or both were removed. Contrary to our hypothesis, the effects of Understory or litter removal were not always negative. A significant soil pH increase with litter removal was a positive factor for acid soil in the studied site. Except for soil moisture, significant effects, caused by removal of litter or/and Understory, on measured soil chemical characteristics were only observed in the top 10 cm soil layer, but not in the 10–20 cm layer. Soil available P and exchangeable K contents were significantly higher in the rainy season than in the dry season, however, for the other soil properties, not substantially affected by season.
Han Y H Chen - One of the best experts on this subject based on the ideXlab platform.
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is Understory plant species diversity driven by resource quantity or resource heterogeneity
Ecology, 2010Co-Authors: Samuel F Bartels, Han Y H ChenAbstract:What maintains plant species diversity has been the subject of much debate with no general consensus. In forest ecosystems in which Understory plants account for the majority of floristic diversity, a crucial question is whether Understory plant diversity is driven by resource quantity or resource heterogeneity. This study sought to reconcile the two hypotheses in relation to their effects on Understory plant diversity in forest ecosystems. A database of studies that investigated the effects of resources on Understory plant diversity was compiled and analyzed using log-linear models. Whether resource quantity or resource heterogeneity is the determinant of Understory plant diversity in individual studies was dependent on stand successional stage(s), presence or absence of intermediate disturbance, and forest biome within which the studies were conducted. Resource quantity was found to govern species diversity in both young and mature stands, whereas resource heterogeneity dominated in old-growth stands. Resource quantity remained the important driver in both disturbed and undisturbed forests, but resource heterogeneity played an important role in disturbed forests. We argue that neither resource quantity nor heterogeneity alone structures species diversity in forest ecosystems, but rather their influences on Understory plant diversity vary with stand development and disturbances in forest ecosystems.
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fire logging and overstory affect Understory abundance diversity and composition in boreal forest
Ecological Monographs, 2008Co-Authors: Stephen A Hart, Han Y H ChenAbstract:Understory vegetation plays a critical role in boreal ecosystems. Despite this, quantitative evaluation of the factors controlling Understory vegetation abundance, diversity, and composition in the most diverse boreal forest region in North America is lacking. This study examined the dynamics of Understory vegetation of stands of fire origin and tested effects of overstory composition and logging vs. fire on the Understory vegetation dynamics in Ontario, Canada. Understory vegetation communities were sampled in 68 stands of conifer, mixed-wood, and deciduous overstory type ranging from 7 to 201 years postfire for stands of fire origin, and from 7 to 31 years for stands of logging origin. For stands of fire origin, total cover and species richness followed similar trends for the three overstory types and were highest in the intermediate-aged stands (72-90 years). Trends in cover and richness, however, differed significantly for vascular and nonvascular plant groups. Vascular cover and species richness were generally higher under deciduous stands, and lower on older stands, while nonvascular species richness was highest under conifer stands and increased with time since fire. Neither species richness nor compositional turnover was higher under mixed-wood stands; mixed-wood stands were compositionally intermediate to conifer and deciduous stands. Multivariate analysis using multiple-response permutation procedures indicated that Understory communities were compositionally distinct for all overstory types and showed no convergence with increasing time since fire. Compared with postfire stands of similar ages, post-logged stands had similar total Understory cover and richness. Vascular cover and richness, however, were higher on post-logged stands, and nonvascular cover and richness were lower. Stands of logging and fire origin were compositionally distinct for all overstory types and ages. Compositional differences appeared to be driven by higher preestablished rhizomatous species and few pyrophilic species on post-logged sites. Understory vegetation communities in the central boreal shield appear to support the intermediate disturbance hypothesis. Understory richness, however, was not negatively associated with high cover values as predicted by the intermediate disturbance hypothesis. Moreover, richness appears to be highest on sites with high light availability, suggesting that boreal Understory communities are influenced more by plant tolerances for low resources, rather than by competition.
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Understory vegetation dynamics of north american boreal forests
Critical Reviews in Plant Sciences, 2006Co-Authors: Stephen A Hart, Han Y H ChenAbstract:Understory vegetation is the most diverse and least understood component of North American boreal forests. Understory communities are important as they act as drivers of overstory succession and nutrient cycling. The objective of this review was to examine how Understory vegetation abundance, composition, and diversity change with stand development after a major stand replacing disturbance. Understory vegetation abundance and diversity increase rapidly after fire, in response to abundant resources and an influx of disturbance adapted species. The highest diversity occurs within the first 40 years following fire, and declines indefinitely thereafter as a result of decreasing productivity and increased dominance of a small number of late successional feather mosses and woody plant species. Vascular plant and bryophyte/lichen communities undergo very different successional changes. Vascular plant communities are dynamic and change more dramatically with time after fire, whereas bryophyte and lichen communiti...
Kelly A Austin - One of the best experts on this subject based on the ideXlab platform.
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plant diversity in managed forests Understory responses to thinning and fertilization
Ecological Applications, 1999Co-Authors: Sean C Thomas, Charles B Halpern, Donald A Falk, Denise A Liguori, Kelly A AustinAbstract:2 Environmental Forestry Research, Weyerhaeuser Company, Tacoma, Washington 98422 USA Abstract. Although most temperate forests are actively managed for timber production, few data exist regarding the long-term effects of forest management on Understory plant communities. We investigated the responses of Understory communities to a factorial com- bination of silvicultural-thinning and nutrient-addition treatments maintained for 12-16 yr in a set of 21-27 yr old Douglas-fir (Pseudotsuga menziesii) plantations. The four thinning levels span those used operationally (final stem densities of 494-1680 trees/ha); the two fertilization levels included a control and N addition in the form of urea at ;60 kg N·ha 21 ·yr 21 , about twice the dosage used operationally. Understory vegetation cover showed significant effects of thinning, with the highest thinning level resulting in the highest observed cover values. However, in some cases low levels of thinning resulted in a reduction in Understory cover compared to unthinned con- trols. Understory vegetation declined dramatically in response to urea fertilization, with up to a 10-fold drop in herb-layer cover in unthinned stands. Species richness showed a simpler response to treatments, increasing in response to thinning, but decreasing in response to fertilization. Examination of species-area relationships indicated that effects of thinning and fertilization on species richness were similar across the range of spatial scales examined. Tree canopy cover, assessed by means of hemispherical photograph analysis, increased with fertilization, and estimated Understory light levels decreased with fertilization, but neither showed a significant response to thinning at the time of measurement (12-16 yr after tree removal). Thus, treatment effects on Understory cover and species richness were not a simple function of canopy cover or estimated light availability. Rather, there was a weak positive relationship between estimated Understory light flux and vascular plant cover and diversity in nonfertilized plots, and no such relationship in fertilized plots. The lack of correspondence between treatment effects on canopy cover and Understory vegetation may be due to time lags in Understory response to changes in canopy cover or to treatment effects not mediated by light availability, such as physical disturbance during thinning operations and toxicity responses following application of urea fertilizer. Species-specific responses to treatments were in part predictable as a function of plant life-form and edaphic association: species affinity for high soil moisture was the best predictor of fertilization responses, while life-form was the best predictor of thinning responses, with ferns and graminoids showing the largest positive responses to thinning. The successional status and stature of Understory plant species were not significantly related to treatment responses. In sum, our results indicate that silvicultural thinning and fertilization can have large effects on Understory plant diversity and community composition. However, such effects were not a simple function of Understory light levels, and conventional ''functional types'' were of only limited value in predicting species-specific responses to silvicultural treatments.
Miina Rautiainen - One of the best experts on this subject based on the ideXlab platform.
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The impact of tree canopy structure on Understory variation in a boreal forest
Forest Ecology and Management, 2020Co-Authors: Titta Majasalmi, Miina RautiainenAbstract:Abstract Information on Understory composition and its relationships with the overstory tree canopy, especially leaf area index (LAI), is crucially needed in, e.g., modeling land-atmosphere interactions and productivity of forests. There are also several global LAI products produced from satellite data which need to be validated with ground reference data. However, to date, only scarce field data on simultaneous structural properties of under- and overstory vegetation, and tree canopy LAI, have been available in boreal forests. This paper shows how Understory composition and fractional cover of different species types varies in a boreal forest site, and how it is linked to structural properties of the tree layer. The study is based on 301 Understory plots collected in an area of ∼16 km2 around Hyytiala forestry field station, Finland (61°50′N, 24°17′E) in a southern boreal forest site. Forest Understory plot data was accompanied with measurements of both standard forest inventory variables and optically-based canopy light transmittance data. Clear differences in average species composition between different site fertility types were observed, but also large variation within each site fertility type was noted. Forest Understory composition was better correlated with structural forest canopy measures (e.g., tree canopy LAI, canopy cover, canopy openness) than with traditional forest inventory variables such as tree height or diameter. Forest canopy LAI and the fractional cover of Understory were strongly related, especially in more fertile sites. Our results highlight the role of tree canopy structural metrics as modifiers of the Understory light climate and growing conditions, also, in boreal forests.
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Seasonal Contribution of Understory Vegetation to the Reflectance of a Boreal Landscape at Different Spatial Scales
IEEE Geoscience and Remote Sensing Letters, 2013Co-Authors: Miina Rautiainen, Janne HeiskanenAbstract:The composition of Understory vegetation plays a central role in satellite-based estimation of biophysical properties of the tree layer in managed boreal forests. In this letter, we assess the contribution of Understory vegetation to the reflectance of a managed boreal forest area throughout a growing season both at stand and landscape levels. We use a time series of SPOT and Hyperion, and MODIS satellite images, and a concurrent set of ground reference. Our results show that the contribution of Understory to stand or landscape reflectance depends on tree canopy gap fractions and Understory reflectance spectra, and their seasonal development. The reflected signal from the Understory vegetation can account for more than 40% of boreal forest reflectance at stand level and for 20% at landscape level.
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Hyperspectral datasets of boreal forest Understory vegetation in Finland
2012 4th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2012Co-Authors: Miina Rautiainen, Janne Heiskanen, Matti Mõttus, Jouni PeltoniemiAbstract:The Understory layer or `forest floor' typically has a significant role in forming the spectral signal of a sparse boreal forest. However, the lack of field measurements on Understory spectra and their seasonality has restricted the development of remote sensing algorithms for phenological monitoring. This paper reviews recent efforts to establish hyperspectral databanks of forest Understory vegetation in Finland, also unique to the entire boreal zone. Both multiangular and multitemporal data sets comprising the most common Understory species have been collected. The data can be applied, for example, to separate the contributions of the tree layer and Understory to the spectral signal of a forest through radiative transfer modeling.
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seasonal reflectance dynamics of common Understory types in a northern european boreal forest
Remote Sensing of Environment, 2011Co-Authors: Miina Rautiainen, Janne Heiskanen, Matti Mõttus, Anu Akujarvi, Titta Majasalmi, Pauline StenbergAbstract:The influence of the seasonal cycle of boreal forest Understory has been noticed in global remote sensing of vegetation, especially in remote sensing of biophysical properties (e.g. leaf area index) of the tree-layer in a forest. A general problem in the validation of operationally produced global biophysical vegetation products is the lack of ground reference data on the seasonal variability of different land surface types. Currently, little is known about the spectral properties of the Understory layers of boreal forests, and even less is known about the seasonal dynamics of the spectra. In this paper, we report seasonal trajectories of Understory reflectance spectra measured in a European boreal forest. Four study sites representing different forest fertility site types were selected from central Finland. The Understory composition was recorded and its spectra measured with an ASD FieldSpec Hand-Held UV/VNIR Spectroradiometer ten times during the growing period (from May to September) in 2010. Our results show that the spectral differences between and within Understory types are the largest at the peak of the growing season in early July whereas in the beginning and end of the growing season (i.e. early May and late September, respectively) the differences between the Understory types are marginal. In general, the fertile sites had the brightest NIR spectra throughout the growing season whereas infertile types appeared darker in NIR. Our results also indicated that a mismatch in the seasonal development of Understory and tree layers does not occur in boreal forests: the Understory and tree layer vegetation develop at a similar pace in the spring (i.e. there are no or only few spring ephemerals present), and the forests with the strongest seasonal dynamics in tree canopy structure (LAI) have also the strongest dynamics in Understory spectra.
Charles B Halpern - One of the best experts on this subject based on the ideXlab platform.
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Canopy closure exerts weak controls on Understory dynamics: a 30-year study of overstory–Understory interactions
Ecological Monographs, 2013Co-Authors: Charles B Halpern, James A LutzAbstract:Stem exclusion and Understory reinitiation are commonly described, but poorly understood, stages of forest development. It is assumed that overstory trees exert strong controls on Understory herbs and shrubs during the transition from open- to closed-canopy forests, but long-term observations of this process are rare. We use long-term data from 188 plots to explore patterns and correlates of variation in Understory richness and abundance 15–45 years after clear-cut logging and burning of two experimental watersheds in western Oregon, USA. We test whether variation in the temporal dynamics of plots can be explained by topoedaphic factors that influence resource availability (insolation and soil moisture), variation in the pace and intensity of overstory development, or characteristics of the vegetation prior to canopy closure. Changes in forest structure were substantial over the study period; canopy cover increased fourfold, stem density by 75%, and bole biomass by two orders of magnitude, although trends were highly variable among individual plots. In contrast, Understory richness, foliar cover, and biomass declined only 30–40%, driven by loss of early-seral colonists, not residual forest species. Canopy closure occurred earlier on north aspects but declines in Understory biomass, reflecting loss of colonizing shrubs (without concomitant increases in forest shrubs), were limited to south aspects. In contrast, variation in effective soil moisture had little influence on the pace of decline. Temporal trends were highly asynchronous among plots: nearly 50% of plots experienced some form of decline, but >35% showed no discernible trend. Declines were more likely in plots with greater tree influence before or at peak overstory development, but also in plots with greater Understory development prior to canopy closure. Quantile regression models indicated weak relationships between Understory biomass and overstory structure at most points in time. Our long-term data support a model of Understory dynamics in which characteristics of the pre-closure vegetation are as important as overstory structure in determining the timing and nature of decline. Long-term studies are critical for elucidating patterns and processes that cannot be inferred from short-term experiments or space-for-time substitutions.
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canopy closure exerts weak controls on Understory dynamics a 30 year study of overstory Understory interactions
Ecological Monographs, 2013Co-Authors: Charles B Halpern, James A LutzAbstract:Stem exclusion and Understory reinitiation are commonly described, but poorly understood, stages of forest development. It is assumed that overstory trees exert strong controls on Understory herbs and shrubs during the transition from open- to closed-canopy forests, but long-term observations of this process are rare. We use long-term data from 188 plots to explore patterns and correlates of variation in Understory richness and abundance 15–45 years after clear-cut logging and burning of two experimental watersheds in western Oregon, USA. We test whether variation in the temporal dynamics of plots can be explained by topoedaphic factors that influence resource availability (insolation and soil moisture), variation in the pace and intensity of overstory development, or characteristics of the vegetation prior to canopy closure. Changes in forest structure were substantial over the study period; canopy cover increased fourfold, stem density by 75%, and bole biomass by two orders of magnitude, although trends were highly variable among individual plots. In contrast, Understory richness, foliar cover, and biomass declined only 30–40%, driven by loss of early-seral colonists, not residual forest species. Canopy closure occurred earlier on north aspects but declines in Understory biomass, reflecting loss of colonizing shrubs (without concomitant increases in forest shrubs), were limited to south aspects. In contrast, variation in effective soil moisture had little influence on the pace of decline. Temporal trends were highly asynchronous among plots: nearly 50% of plots experienced some form of decline, but >35% showed no discernible trend. Declines were more likely in plots with greater tree influence before or at peak overstory development, but also in plots with greater Understory development prior to canopy closure. Quantile regression models indicated weak relationships between Understory biomass and overstory structure at most points in time. Our long-term data support a model of Understory dynamics in which characteristics of the pre-closure vegetation are as important as overstory structure in determining the timing and nature of decline. Long-term studies are critical for elucidating patterns and processes that cannot be inferred from short-term experiments or space-for-time substitutions.
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plant diversity in managed forests Understory responses to thinning and fertilization
Ecological Applications, 1999Co-Authors: Sean C Thomas, Charles B Halpern, Donald A Falk, Denise A Liguori, Kelly A AustinAbstract:2 Environmental Forestry Research, Weyerhaeuser Company, Tacoma, Washington 98422 USA Abstract. Although most temperate forests are actively managed for timber production, few data exist regarding the long-term effects of forest management on Understory plant communities. We investigated the responses of Understory communities to a factorial com- bination of silvicultural-thinning and nutrient-addition treatments maintained for 12-16 yr in a set of 21-27 yr old Douglas-fir (Pseudotsuga menziesii) plantations. The four thinning levels span those used operationally (final stem densities of 494-1680 trees/ha); the two fertilization levels included a control and N addition in the form of urea at ;60 kg N·ha 21 ·yr 21 , about twice the dosage used operationally. Understory vegetation cover showed significant effects of thinning, with the highest thinning level resulting in the highest observed cover values. However, in some cases low levels of thinning resulted in a reduction in Understory cover compared to unthinned con- trols. Understory vegetation declined dramatically in response to urea fertilization, with up to a 10-fold drop in herb-layer cover in unthinned stands. Species richness showed a simpler response to treatments, increasing in response to thinning, but decreasing in response to fertilization. Examination of species-area relationships indicated that effects of thinning and fertilization on species richness were similar across the range of spatial scales examined. Tree canopy cover, assessed by means of hemispherical photograph analysis, increased with fertilization, and estimated Understory light levels decreased with fertilization, but neither showed a significant response to thinning at the time of measurement (12-16 yr after tree removal). Thus, treatment effects on Understory cover and species richness were not a simple function of canopy cover or estimated light availability. Rather, there was a weak positive relationship between estimated Understory light flux and vascular plant cover and diversity in nonfertilized plots, and no such relationship in fertilized plots. The lack of correspondence between treatment effects on canopy cover and Understory vegetation may be due to time lags in Understory response to changes in canopy cover or to treatment effects not mediated by light availability, such as physical disturbance during thinning operations and toxicity responses following application of urea fertilizer. Species-specific responses to treatments were in part predictable as a function of plant life-form and edaphic association: species affinity for high soil moisture was the best predictor of fertilization responses, while life-form was the best predictor of thinning responses, with ferns and graminoids showing the largest positive responses to thinning. The successional status and stature of Understory plant species were not significantly related to treatment responses. In sum, our results indicate that silvicultural thinning and fertilization can have large effects on Understory plant diversity and community composition. However, such effects were not a simple function of Understory light levels, and conventional ''functional types'' were of only limited value in predicting species-specific responses to silvicultural treatments.