An improved canopy interception scheme into biogeochemical analysis of water fluxes in subalpine coniferous forest (Northern Italy)

To demonstrate altitudinal gradients (and resulting temperatures) that affect myxomycete biodiversity and species composition, we statistically compared myxomycete assemblages between a subalpine coniferous forest and a montane pine forest within the region of the Yatsugatake Mountains, Nagano Prefecture, Central Japan. In summer and autumn field surveys during 2003-2010, 53 myxomycete taxa (with varieties treated as species) were observed from 639 records of fruiting bodies in the subalpine forest and 32 taxa were detected from 613 records in the montane forest. There were 20 species in common between the assemblages and the percentage similarity index was 0.400. Myxomycete biodiversity was higher in the subalpine than in the montane forest. Nine myxomycete species were statistically frequent occurrences in the subalpine forest and appeared in autumn: Lamproderma columbinum, Cribraria macrocarpa, Trichia botrytis, Physarum newtonii, Diderma ochraceum, Enteridium splendens, Elaeomyxa cerifera, Trichia verrucosa, and Colloderma oculatum. Five species were restricted to appear in the subalpine forest: Cribraria purpurea, Cribraria rufa, Cribraria ferruginea, Cribraria piriformis, and Lepidoderma tigrinum. Dead wood in the subalpine forest provided a breeding habitat for specific myxomycetes that inhabit cold areas; that is those areas having geographical features of decreasing temperature and increasing elevation, such as the temperate area of Central Japan.

Modern pollen assemblages from 18 small ponds and wetlands on the spatially isolated and forested Kaibab Plateau were studied to determine how the pollen assemblages recorded vegetation patterns. Vegetation of the Plateau consists of an inner core of subalpine Picca/Abies forests, surrounded by mixed Abies/Picea/ Pseudotsuga/Pinus ponderosa forests, which are in turn surrounded by extensive Pinus ponderosa forests. The flanks of the Plateau are vegetated by Pinus edulis/Juniperus woodlands, with scattered Quercus populations. Arboreal pollen assemblages were dominated by Pinus (70-98 %), which was most abundant in the P. ponderosa forests. Picea, Abies, Pseudotsuga and Populus pollen were abundant only at sites in the mixed and subalpine conifer forests, where their combined abundance never exceeded 16% except at the site deepest in the subalpine forest (22%). Pollen percentages of Cupressaceae and Pinus Subsection Cembroides were highest in the outermost P. ponderosa forests (nearest the P. edulis/Juniperus woodlands) and in the mixed and subalpine conifer forests, where Quercus pollen was also highest. Percentage representation of the well-dispersed pollen of Quercus, Cupressaceae and Pinus Subsect. Cembroides was amplified at these latter sites by the poor pollen representation of the dominant Picca, Abies and Pseudotsuga trees. This effect is similar to that recorded in many pollen assemblages from arctic and alpine tundra regions.

Temperature of every month on both the upper and lower boundaries of sub-alpine dark conifer forests at various sites in China are estimated in terms of their distributions and temperature records. Based on these estimated data, the heat factors to influence and control the distribution and growth of sub-alpine dark conifer forests in China are discussed. It is found that the most important heat index to influence and control the distribution and growth of sub-alpine dark conifer forests is neither the mean temperature in the warmest month, nor the maximum or minimum temperatures, but monthly accumulated temperature of >0°C or monthly effective accumulated temperature of >5°C. When monthly accumulated temperature of >0°C is more than 40°C, or monthly effective accumulated temperature of >5°C is over 50°C, sub-alpine dark conifer forests cannot grow well. When monthly accumulated temperature of >5°C is less than 60°C, sub-alpine dark conifer forests can not grow at all. When monthly effective accumulated temperature of >5°C is in the range 15°C–45°C, sub-alpine dark conifer forests in China can grow well. The ecological significance of temperature in May and September, and in summer half year are discussed.

The snowshoe hare (Lepus americanus) is a habitat specialist with a broad geographic range associated with boreal and subalpine forests in North America (Hall 1981, Hodges 1999a,b). It reaches southern range limits in the Southern Rocky Mountains in northern New Mexico, USA. Here, scant and mostly anecdotal evidence suggests that it is restricted to high-elevation, subalpine conifer forests dominated by Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa; Findley et al. 1975, DeVelice et al. 1986, Pase and Brown 1994). These southwestern forests lack several plant species, including lodgepole pine (Pinus contorta), jackpine (Pinus banksiana), black spruce (Picea mariana), birch (Betula spp.), and balsam poplar (Populus balsamifera), that, in more northern latitudes, are considered important habitat elements for snowshoe hare, especially in terms of cover (Bittner and Rongstad 1982, Litvaitis et al. 1985, DeVelice et al. 1986, Ferron and Ouellet 1992, Bryant et al. 1994, Pase and Brown 1994, Moir and Fletcher 1996). Methods for managing subalpine forests for snowshoe hare in the Southern Rocky Mountains are particularly important because of a current effort to reintroduce Canada lynx (Lynx canadensis), which is a specialized predator of snowshoe hare (Hodges 1999a,b, Colorado Division of Wildlife 2002). Another leporid, the mountain cottontail (Sylvilagus nuttallii), occurs throughout the intermountain region of western North America, also reaching the southern extent of its range in the American Southwest (Hall 1981). Throughout this broad zone of sympatry, the two leporids segregate in ecological distribution with no reports of syntopy (Bittner and Rongstad 1982, Chapman et al. 1982, Chapman and Wilner 1986). The mountain cottontail typically is associated with lower-elevation sagebrush (Artemisia spp.)–dominated habitats (Orr 1940, Chapman 1975, 1999, Chapman et al. 1982). However, it is a habitat generalist and at more southern latitudes it also occurs in higher-elevation habitats including juniper (Juniperus spp.) and pinon pine (Pinus spp.) woodlands and middle-elevation montane conifer forests, which are dominated by ponderosa pine (Pinus ponderosa), white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii), and blue spruce (Picea pungens; Bailey 1931, Durrant 1952, Findley et al. 1975, Hoffmeister 1986, Fitzgerald et al. 1994, Frey and Yates 1996). Mountain cottontails also occur in subalpine conifer forest in areas of the Southwest and Southern Rocky Mountains where snowshoe hare are absent, such as the White Mountains in eastcentral Arizona and the Pikes Peak massive in central Colorado (Warren 1910, Armstrong 1972, Hoffmeister 1986). Findley et al. (1975) reported a specimen each of mountain cottontail and snowshoe hare from Goose Lake, Taos County, New Mexico, USA. This locality is at 3,542 m elevation, which is in the subalpine conifer forest zone. These records suggested that less ecological segregation between snowshoe hare and mountain cottontail might occur in the American Southwest, including the potential for local syntopy. Thus, the purpose of our study was to assess habitat use of snowshoe hare and mountain cottontail in subalpine conifer forests at their southern point of sympatry in the Southern Rocky Mountains.

Background: Recently, deer have expanded their distribution to higher altitude ranges including subalpine forests. However, culling deer and construction of deer fence in subalpine forests are difficult because of steep slopes and complex topography. Thus it is necessary to clarify the factors which are associated with debarking by deer for the effective protection of subalpine forests. In this study, we examined which factors are associated with debarking by sika deer (Cervus nippon) in subalpine coniferous forests. Methods: We conducted our survey in Minami-Alps National Park, central Japan. We established 24 10 m× 40 m plots and surveyed the occurrence of debarking on saplings >30 cm in height and <3 cm in diameter at breast height (DBH) and on trees >3 cm in DBH, as well as sapling density within each plot. Minimum distances to nearest grassland of plots were calculated (tentatively assuming grassland would attract deer and would cause high debarking pressure in the surrounding subalpine forests). Results: The mean percentage of debarked live saplings was higher than that of live trees. The mean percentage of debarked saplings which had already died was 81.6 %. Debarking of saplings increased with lower elevation, taller sapling size, and marginally increased near grassland. Sapling density was lower in plots with low basal area of conspecific trees near grassland and differed among species. Sapling density marginally decreased with decreasing elevation and increasing stand tree density. Debarking of trees was positively related to small DBH and low elevation, and marginally increased near grassland and differed among species. Conclusions: Our results suggest that tall saplings in subalpine forests of low elevation or near subalpine grassland were susceptible to debarking by deer and monitoring of these areas may permit the early detection of the impacts of deer in subalpine coniferous forests. Keywords: Abies, Cervus nippon, Debarking, Grassland, Picea, Sapling density, Subalpine region

The water balance components of Mediterranean pine trees on a steep mountain slope during two hydrologically contrasting years

Quantification of repeated gap formation events and their spatial patterns in three types of old-growth forests: Analysis of long-term canopy dynamics using aerial photographs and digital surface models

“Shimagare” or a phenomenon of blighted trees distributing in stripes is one of the characteristic features seen in the subalpine forests in Japan. The striped pattern of a group of withered trees in the subalpine forests is not only of great interest for those researchers of plant geography and plant ecology, but an important problem to be solved for the protection of nature and forest conservation. The Shimagare is uniquely observed in the subalpine coniferous forests, mainly consisting of Abies veitchii and Abies mariesii, partially mixed with Tsuga diversifolia and Picea hondoensis. The blighted forests present various shapes in the course of development, spots at the initial stage turning into arches and finally into stripes. From the fact that the Shimagare zones appear almost at the same altitude and on the slope facing in the same dierction, and further from the fact that the dead tree stripes move upward on the slope (or leeward) with the lapse of time, it is thought that the phenomenon has close relationship to the prevailing wind direction. To sum up the results of studies obtained so far on this subject, the Shimagare zone is distributed in the subalpine forests, ranging from the Kinki District to the northern part of the Kanto District in Japan; Oku-Nikko, Yatsugatake, Chichibu Koshin Kokkyo, Southern Alps, Central Alps, and Ohmine Mountains. Excepting for the Ohmine Mountains, where the lower limit of the distribution of Abies veitchii is low, this phenomenon appears at an altitude of higher than 2, 000m and mainly on the gentle slopes facing SW-SE. The investigation was carried out in the areas in the Chichibu Koshin Kokkyo Mountains, the Oku-Nikko Mountains and Akaishi Mountains by making use of aerial photographs and the field survey. Belt transects with a width of one meter for all trees with the diameter at breast height of more than 3cm were taken at a right angle at the center of the arch stripe of the Shimagare. At the same time, the height of trees, underbrush, density, and soil profiles were noted (Fig. 1). As a result of the present study, the following facts are clarified: 1) In all such mountains as stated above, the Shimagare phenomena are distributed on the gentle slopes facing SE-SW or failry flat ridge tops. It seems, therefore, that the distribution is related to the radiation, evaporation and prevailing wind direction. 2) The Shimagare strips are found only in the needle-leaved forest in sub-alpine regions. This fact, along with the movement, scale and shape of the Shimagare strips, is enough to make us believe that Abies veitchii and Abies mariesii are liable to be influenced by abrupt change of environments. 3) According to the meteorological observation carried out on the slope of Mt. Nantai, Oku-Nikko, the zone of the subalpin.e forests on the top of the mountain is characterized by the larger number of days with dense mist, frost, stronger wind, and greater cloudiness but by less precipitation than on the foot and mid-slope of the mountain. It can be said, therefore, that the relatively dry condition caused by the stronger wind on this zone might be one of the causes of the Shimagare phenomenon. 4) The soil in the Shimagare zone differs in thickness from place to place, but generally it is thin ranging from 4 to 30cm. The layer is mostly made up of humus underlain by the base rock. In the region, where the Shimagare is lacking, trees grow higher and the soil is thick. On the contrary, many trees fall dead in the Shimagare zone, probably because of the thin soil layer. 5) Comparing the prevailing wind direction estimated by the wind-shaped trees with the arrangement and shape of the Sh.imagare stripes, it was made clear that the direction of fallen trees and the direction of the movement of the Shimagare stripes have close relation to the prevailing southerly winds in spring, summer and autumn.

Dwarf bamboos impose intense resource competition in subalpine coniferous forests, and their exclusive densities have crucial impacts on tree regeneration and understory species diversity. We studied the factors influencing the distribution and growth of dwarf bamboo, Fargesia nitida, in a subalpine forest in southwest China. TWINSPAN, based on an attribute matrix, could divide the subalpine forest into 11 sub‐associations, and more clearly reflected ecological functional features of the subalpine forest than analysis based on a species matrix. TWINSPAN was also generally consistent with DCA ordination based on the attribute matrix. DCA and DCCA ordination showed relationships between the distribution of F. nitida population and environment factor. The first DCCA axis showed topography and disturbance gradients (except fallen trees and broken branches); the second DCCA axis showed canopy density and composition gradients. Stepwise multiple regression analyses showed that distribution (culm density and coverage) of F. nitida decreased significantly with landslide and slope aspect, and increased significantly with soil status. The light condition had positive effects on growth and size of bamboo. A stable environment in the northern slope and more broadleaved species dominating in canopy would increase the dwarf bamboo biomass. Thus, the disturbance regimes, the slope aspect and the BA of evergreen conifer trees can provide useful guidelines for the control and management of F. nitida populations, and in helping to understand the succession and regeneration of subalpine forest in this region.

Research Highlights: To ensure sustainable forest regeneration, it is important to clarify whether new recruits or advanced regenerants are more likely to be stripped. Therefore, the effects of bark stripping on saplings in subalpine forests with abundant saplings should be analyzed by regeneration mode, but there have been no such studies until now. Background and Objectives: I investigated the effects of bark stripping by Cervus nippon on saplings in a subalpine coniferous forest in central Japan to (1) reveal differences in bark stripping between new recruits and advanced regenerants and (2) clarify the factors affecting survivorship. Materials and Methods: A 50 m × 140 m (0.7 ha) plot was set in the old-growth subalpine coniferous forest. All trees in the plot that were ≥2 m in height were tagged, identified to species, measured diameter at breast height and recorded bark stripping by deer. These trees and new recruits were counted and measured in 2005, 2007, 2012, and 2017. I compared saplings recruited in 2007, 2012, and 2017 (“new recruits”) with existing saplings of the same size (“advanced regenerants”). Results: The density of new recruits of Abies mariesii and Tsuga diversifolia increased, whereas that of Abies veitchii decreased. The proportion of stripped saplings was greater in new recruits than in advanced regenerants, significantly so in A. veitchii, which also had the highest maximum bark stripping ratio. Factors affecting the survivorships applied by the regression tree analysis were the maximum stripping ratio of stems for the two Abies species and the initial size for the T. diversifolia. Conclusions: Bark stripping by deer was more intensive on new recruits than on advanced regenerants in a subalpine forest, and regeneration in canopy gaps might fail because of intensive bark stripping in areas overabundant in deer.

Abstract. Rice paddy fields are one of the greatest anthropogenic sources of methane (CH4), the third most important greenhouse gas after water vapour and carbon dioxide. In agricultural fields, CH4 is usually measured with the closed chamber technique, resulting in discontinuous series of measurements performed over a limited area, that generally do not provide sufficient information on the short-term variation of the fluxes. On the contrary, aerodynamic techniques have been rarely applied for the measurement of CH4 fluxes in rice paddy fields. The eddy covariance (EC) technique provides integrated continuous measurements over a large area and may increase our understanding of the underlying processes and diurnal and seasonal pattern of CH4 emissions in this ecosystem. For this purpose a Fast Methane Analyzer (Los Gatos Research Ltd.) was installed in a rice paddy field in the Po Valley (Northern Italy). Methane fluxes were measured during the rice growing season with both EC and manually operated closed chambers. Methane fluxes were strongly influenced by the height of the water table, with emissions peaking when it was above 10–12 cm. Soil temperature and the developmental stage of rice plants were also responsible of the seasonal variation on the fluxes. The measured EC fluxes showed a diurnal cycle in the emissions, which was more relevant during the vegetative period, and with CH4 emissions being higher in the late evening, possibly associated with higher water temperature. The comparison between the two measurement techniques shows that greater fluxes are measured with the chambers, especially when higher fluxes are being produced, resulting in 30 % higher seasonal estimations with the chambers than with the EC (41.1 and 31.7 g CH4 m−2 measured with chambers and EC respectively) and even greater differences are found if shorter periods with high chamber sampling frequency are compared. The differences may be a result of the combined effect of overestimation with the chambers and of the possible underestimation by the EC technique.

The patterns of biodiversity along altitudinal gradients are well-documented ecological phenomena. Community composition and structure are important factors affecting diversity patterns in plant communities. Furthermore, species diversity along altitudinal gradient differs in different layers at different scales. In this paper, we analyzed the composition and structure of communities on the northern slope of Mt. Changbai based on TWINSPAN classification. The patterns of plant diversity for tree, shrub and herb layers were described by indices of species richness, α diversity and β diversity. Four community groups characterized by different dominants in the tree layer were distinguished: (1) mixed coniferous and broad-leaved forests (700 -1065 m a.s.l.) dominated by Pinus koraiensis, Tilia amurensis, Fraxinus mandschurica, and Acer mono, including secondary birch forest (1150 m a.s.l) dominated by Betula platyphylla, which developed from natural pine and deciduous forests due to disturbance; (2) transitional forests of mixed coniferous and broad-leaved forest and sub-alpine coniferous forests (1100-1300 m a.s.l.); (3) sub-alpine coniferous forests (1300-1780 m a.s.l.) dominated by Picea jezoensis, Abies nephrolepi and Larix olgensis; and (4) alpine birch forests (1800-2000 m a.s.l.) dominated by Betula ermanii. Distribution of importance values of dominants explicitly indicated a vertical pattern of these four forest types. Frequency distribution of DBH classes suggested major forest types in Mt. Changbai were regenerating at a healthy pace. Species richness in the tree and shrub layers declined with altitude, while herb layer species richness showed no significant trend along the altitudinal gradient. With increasing altitude, α diversity, represented by the Shannon-Wiener index, decreased for both tree and shrub layers, with no clear trend for herb layer. Pielou evenness index in the three layers showed no noticeable change with increasing altitude. β diversity, indicated by the Cody index, declined with increasing altitude for all three layers.

Soil seed banks along elevational gradients in tropical, subtropical and subalpine forests in Yunnan Province, southwest China

Soil microbes are an important component of soil ecosystems that influence material circulation and are involved in the energy flow of ecosystems. The increase in atmospheric nitrogen (N) deposition affects all types of terrestrial ecosystems, including subalpine forests. In general, alpine and high-latitude ecosystems are N limited. Increased N deposition could therefore affect microbial activity and soil respiration. In this study, four levels of N addition, including CK (no N added), N1 (2 g m−2 a−1), N2 (5 g m−2 a−1), and N3 (10 g m−2 a−1), were carried out in a Sichuan redwood forest at the eastern edge of the Tibetan Plateau. The dynamics of soil respiration, major microbial groups, ecoenzymatic stoichiometry, and microbial biomass carbon and nitrogen (MBC and MBN, respectively) were investigated over a year. The results showed that N application significantly increased soil respiration (11%–15%), MBC (5%–9%), MBN (23%–34%), N-acetylglucosidase (56.40%–204.78%), and peroxidase (42.28%–54.87%) activities. The promotion of soil respiration, N-acetylglucosidase, and peroxidase was highest under the N2 treatment. The carbon, nitrogen, and phosphorus metabolism of soil microbes in subalpine forests significantly responded to N application. In the latter stages of N application, microbial metabolism changed from being N restricted to phosphorus restricted, especially under the N2 treatment. Soil bacteria (B) and gram-positive (G+) bacteria were the dominant microbial groups affecting soil respiration. Structural equation modelling indicated that N application significantly promoted soil respiration and microbial biomass, whereas the main microbial groups did not significantly respond to N application. Therefore, we conclude that short-term N addition alleviates microbial nitrogen limitation and promotes soil respiration in the subalpine forest ecosystem that accelerates soil carbon (C) and N cycling. Continuous monitoring is needed to elucidate the underlying mechanisms under long-term N deposition, which may help in forecasting C, N, and P cycling in the alpine region under global climate change.

Elevational variation in abundance of coarse woody debris in subalpine forests, central Japan