Associate Professor at Yokohama National University (2011-) Visiting Scholar at University of Calgary (2010-2011) Assistant professor at Yokohama National University (2008-2011) Postdoc at Simon Fraser University (2005-2007) Ph.D. at Kyoto University (in 2004) M.S. at Kyoto University (in 2001)
Abstract: Question: This study evaluates historical changes in landscape structure and heterogeneity in subalpine forests. We use response to severe fires in 2001 and 2003, along with historical reconstructions to examine crown-fire effects on landscape heterogeneity and to assess, comparatively, the effects of fire exclusion management in the 20th century.
Location: Subalpine forests of Kootenay National Park (KNP) in the Canadian Rockies.
Methods: Using a landscape-level model based on a fire-origin stand age map, we reconstructed decadal burned areas within the landscape for a period of 1750â2000 (forming reconstructed landscapes). The landscape pattern was analysed for each reconstructed landscape map, and we compared landscape pattern indices (total area, number of patches, mean patch area, patch area variation, largest patch index, edge density, perimeter-area ratio, and landscape shape index) with those of the landscape in 2005 after the recent large fires.
Results: After large fires in 1926, the connectivity of the KNP landscape increased and its diversity was quite low. After the 2001 and 2003 fires, the post-fire landscape of 2005 was highly heterogeneous in terms of size, variation, edge density and the perimeter-area ratio of the remnant forest patches. Since the decline in the occurrence of large fires after 1926 reflected a period of wet weather, fuel build-up resulting from the landscape homogenization within the 20th century landscape could not be primarily attributed solely to fire exclusion. This period without fires greatly enhanced the connectivity of the late-successional forests that finally burned in 2001/2003, but the connectivity was within the historical range for these forests. The gradual increase in stand connectivity before the recent large fires may indicate that fire exclusion was less responsible than often believed for the fuel build-up in these fire-susceptible older forests.
Conclusions: The large fires at the beginning of the 21st century are within the natural range of disturbances for this landscape, and do not stand out as âhuman-induced disastersâ in their effects on landscape patterns. Such stochastic large disturbances contribute to the maintenance of highly heterogeneous landscape structure, which are important for many taxa and natural ecological processes. Identifying the future probability of such large disturbances and their ecological roles should be incorporated into the management of these dynamic, disturbance-prone systems.
Abstract: Drought occurrence and wildfire activity in subalpine forests in Kootenay National Park (KNP) of the Canadian Rockies are studied by focusing on the interannual and multi-decadal variations in climate patterns of the Pacific Ocean. The question addressed is whether broad-scale climate patterns can regulate both large fire occurrence and fire-free periods causing fuel buildups. This study compared years of large wildfire outbreaks for the subalpine forests of KNP during the last three centuries using indices of climate patterns of the Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO). PDO and ENSO were correlated with drought and fire occurrence in KNP. A positive PDOâpositive ENSO combination created extreme drought conducive to crown fires, indicating that the occurrence of high-severity wildfires in these generally moist/cool forests is strongly determined by climatic anomalies. Large fire activity is chiefly modulated by PDO compared to ENSO, because a negative PDO phase greatly decreased fire activity in the mid-twentieth century. Although this fire-free period is seemingly matched with a fire-suppression period, it may be attributable to a negative PDO, which increased precipitation in the region. This mid-century fire gap contributed to the accumulation of old forests serving as loaded fuels within the landscape and ultimately led to occurrences of crown fires as the PDO shifted to the positive phase. Thus, in addition to the fundamental importance of interannual variations in the Pacific that initiates a current-year severe drought, multi-decadal scale climate variability also influences the extent and severity of subsequent fires by modulating pre-fire landscape conditions. For fire management in subalpine areas of the Rockies, although drought occurrence is a primary concern and there are still uncertainties in the detailed changes in fire risk through the successional process, it is worth paying attention to fuel-loads of older forests in the landscape, which may lead to extensive large fires. Because the climatic teleconnection pattern is one of the main drivers of crown fire occurrence in the region in terms of creating current summer drought, and also for constructing a landscape structure prone to larger fires, more of a focus on short to long-term variations in the climate for wildfire management is needed in high-elevation forested landscapes.
Abstract: 1. Maintenance of ecological integrity and biodiversity must be based on well-grounded principles of disturbance ecology. However, non-equilibrium aspects of ecosystems, such as unpredictability, instability, and stochasticity due to various natural disturbances, have not been satisfactorily integrated into practical application. Failure to acknowledge the dynamic nature of systems will inevitably lead to unexpected changes and unachieved conservation goals.
2. This review discusses non-equilibrium ecology in terms of natural disturbances and the conservation and management of terrestrial ecosystems and landscapes.
3. Several key components, which require further ecological consideration, are specifically discussed. These include the hierarchical disturbance regime, disturbance legacy, multiple post-disturbance pathways, climate instability, spatial and temporal variability, and resilience.
4. Natural disturbance regimes are complex and difficult to define. This is because some disturbances can be nested, and they interact with other qualitatively and quantitatively different disturbances, constituting a hierarchy of natural disturbances. Large temporal and spatial perspectives are therefore required to incorporate the hierarchical context of natural disturbance regimes into regional management plans.
5. Conservation managers may often seek some kind of dynamic equilibrium based on protection of species and seral stages from extinction. However, because climate instability interrupts any shift toward an equilibrium, most terrestrial vegetation systems are inherently prone to large environmental changes and diverse disturbances, and thus, are dynamic and non-equilibrating.
6. Synthesis and applications. Resiliency is the key to conserving ecological integrity via the ability to cope with inevitable changes. As long as ecosystems are resilient and disturbances are natural, we should not impede natural shifts in disturbance regimes and resultant ecosystem changes, even if changes are abrupt and unpredictable and thus have large consequences. If ecological resilience has already been eroded by humans, it is important that resilience should be enhanced by restoring keystone features of vegetation systems to prevent disturbance-induced undesirable ecosystem degradation
Abstract: We compared the morphological and physiological characteristics of understory trees of Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes and Tsuga heterophylla (Raf.) Sarg. growing adjacent to each other in an old-growth forest in southwestern Washington State, USA. We hypothesized that, despite contrasting branching patterns and crown architectures, the two species should exhibit convergence in leaf display and photosynthetic gain per light intercepting area, because these are important properties determining their survival in the light-limited understory. The branching pattern of A. amabilis was regular (normal shoot-length distribution, less variable branching angle and bifurcation ratio), whereas that of T. heterophylla was more plastic (positively skewed shoot-length distribution, more variable branching angle and bifurcation ratio). The two species had similar shoot morphologies: number of leaves per unit shoot length and leaf to axis dry mass ratio. Leaf morphology, in contrast, was significantly different. Leaves of A. amabilis were larger and heavier than those of T. heterophylla, which resulted in lower mass-based photosynthetic rate for A. amabilis. Despite these differences, the two species had similar levels of leaf overlap and area-based photosynthetic characteristics. Needle longevity of A. amabilis was nearly twice that of T. heterophylla. The leaf N contents of current and 1-year-old leaves were lower for A. amabilis than for T. heterophylla. However, the leaf N content of A. amabilis did not change from current leaves to 6-year-old leaves, whereas that of T. heterophylla decreased with increasing leaf age. Abies amabilis had deeper crowns than T. heterophylla and retained branches with low relative growth rates. Longer branch retention may compensate for the lower branch-level assimilation rate of A. amabilis. We inferred that the convergence of leaf display and photosynthetic characteristics between A. amabilis and T. heterophylla may contribute to the persistence of both species in the understory of this forest.
Abstract: Light-related plasticity in a variety of crown morphology and within-tree characteristics was examined in sun and shade saplings of Abies amabilis Dougl. ex J. Forbes growing in two late-successional forests with different snow regimes in the Cascade Mountains of Washington, USA. Compared with sun saplings, shade saplings typically had broad flat crowns as a result of acclimation at several scales (needle, shoot, branch, crown and whole sapling). Shoots of shade saplings had a smaller needle mass per unit of stem length than shoots of sun saplings, a feature that enhances light-interception efficiency by reducing among-needle shading. The low annual rate of needle production by shade saplings was associated with a longer needle lifespan and slower needle turnover. Reduced needle production within a shoot was reflected at the branch level, with lateral branches of shade saplings having a smaller needle mass than branches of the same length of sun saplings. Reduced allocation to needles permits greater investment in branches and stems, which is necessary to support the horizontally expanding branch system characteristic of shade saplings. Mean branch age of shade saplings was significantly higher than that of sun saplings. Shade saplings had lower needle mass per unit of trunk biomass or total biomass, reflecting greater investment in the trunk as a support organ. Increased investment in support organs in shade was more evident in the snowier habitat. The observed morphological acclimation makes A. amabilis highly shade and snow-tolerant and thus able to dominate in many late-successional forests in snowy coastal mountain regions.
Abstract: Structural characteristics of Abies mariesii M.T. Mast. saplings growing in sun and shade in a snowy subalpine parkland in central Japan were assessed to infer how saplings acclimate to suppression by larger individuals in a conifer clump and to extremely snowy conditions. Sun and shade saplings produced structurally different current-year shoots, and allocated biomass to needles and stem differently. Compared with sun saplings, shoots of shade saplings had lower needle mass per unit shoot size, which indicates less dense needle packing and more effective use of the limited available light by avoiding mutual shading among needles. Biomass allocation within lateral branches also differed between sun and shade saplings. Compared with sun saplings, needle mass was a smaller proportion of total branch mass in shade saplings although shade saplings retained needles for longer, thereby compensating, in part, for their lower annual production of needles. Thus shade saplings incur a high mechanical cost to support their low-light acclimated, conspicuously flattened crowns in this snowy habitat. Suppressed saplings are an important component of the persistent conifer clumps in snowy subalpine parklands. The observed structural characteristics of A. mariesii saplings, which ensure high shade- and snow-tolerance, contribute to the dominance of the species in snowy subalpine regions in Honshu, Japan.
Abstract: Light-related plasticity of crown morphology and within-crown characteristics were investigated in understory sun and shade saplings of three codominant subalpine conifers, Abies mariesii M.T. Mast., Abies veitchii Lindl. and Picea jezoensis var. hondoensis (Mayr) Rehd. Compared with those of sun saplings, current-year shoots of shade saplings allocated less biomass to needles, resulting in less dense needle packing and hence less mutual needle shading. The proportion of lateral branch biomass in foliage was either similar in sun and shade saplings or greater in shade saplings, depending on the species, suggesting that, over the lifetime of a branch, greater needle longevity in shade compensates for reduced biomass investment in needles of current-year shoots of shade saplings. Saplings with slower-growing branches tended to have greater needle life spans, suggesting that plasticity of branch growth rate and plasticity of needle life span are interdependent. Both Abies species showed greater light-related plasticity of needle life span and branch growth than P. jezoensis. The greater shade tolerance of the Abies species derives from their broad flattened crowns with slow-growing branches. This type of crown development incurs substantial support costs, but the long needle life span of shade saplings of the Abies species compensates, at least in part, for their low annual investment in foliage, especially in the case of A. mariesii, which has a longer needle life span and slower-growing and stouter branches than A. veitchii. Compared with the Abies species, P. jezoensis had a less plastic crown morphology, and less variability of needle life span and branch growth in response to light, resulting in lower shade tolerance. However, compared with the flattened crown of Abies shade saplings, the conical crown of P. jezoensis saplings imposes a smaller support cost, making this species better adapted to rapid height growth than to survival in shade.
Abstract:
1. Maintenance of ecological integrity and biodiversity must be based on well-grounded principles of disturbance ecology. However, non-equilibrium aspects of ecosystems, such as unpredictability, instability, and stochasticity due to various natural disturbances, have not been satisfactorily integrated into practical application. Failure to acknowledge the dynamic nature of systems will inevitably lead to unexpected changes and unachieved conservation goals.
2. This review discusses non-equilibrium ecology in terms of natural disturbances and the conservation and management of terrestrial ecosystems and landscapes.
3. Several key components, which require further ecological consideration, are specifically discussed. These include the hierarchical disturbance regime, disturbance legacy, multiple post-disturbance pathways, climate instability, spatial and temporal variability, and resilience.
4. Natural disturbance regimes are complex and difficult to define. This is because some disturbances can be nested, and they interact with other qualitatively and quantitatively different disturbances, constituting a hierarchy of natural disturbances. Large temporal and spatial perspectives are therefore required to incorporate the hierarchical context of natural disturbance regimes into regional management plans.
5. Conservation managers may often seek some kind of dynamic equilibrium based on protection of species and seral stages from extinction. However, because climate instability interrupts any shift toward an equilibrium, most terrestrial vegetation systems are inherently prone to large environmental changes and diverse disturbances, and thus, are dynamic and non-equilibrating.
6. Synthesis and applications. Resiliency is the key to conserving ecological integrity via the ability to cope with inevitable changes. As long as ecosystems are resilient and disturbances are natural, we should not impede natural shifts in disturbance regimes and resultant ecosystem changes, even if changes are abrupt and unpredictable and thus have large consequences. If ecological resilience has already been eroded by humans, it is important that resilience should be enhanced by restoring keystone features of vegetation systems to prevent disturbance-induced undesirable ecosystem degradation.
