Effects Of Snowpack Research Articles

Effects of Snowpack on Vegetation Phenology in the Hulunbuir Grassland Region of China

Effects of Snowpack on Vegetation Phenology in the Hulunbuir Grassland Region of China

Effects of Snowpack, Temperature, and Disease on Demography in a Wild Population of Amphibians

Understanding the demographic consequences of interactions among pathogens, hosts, and weather conditions is critical in determining how amphibian populations respond to disease and in identifying site-specific conservation actions that can be developed to bolster persistence of amphibian populations. We investigated population dynamics in Boreal Toads (Anaxyrus boreas) relative to abiotic (fall temperatures and snowpack) and biotic (the abundance of another anuran host and disease) characteristics of the local environment in Wyoming, USA. We used capture–recapture data and a multistate model where state was treated as a hidden Markov process to incorporate disease state uncertainty and assess our a priori hypotheses. Our results indicated that snowpack during the coldest week of winter is more influential to toad survival, disease transition probabilities, and the population-level prevalence of the amphibian chytrid fungus (Batrachochytrium dendrobatidis) in the spring, than temperatures in the fall or the presence of another host. As hypothesized, apparent survival at low (i.e., <25 cm) snowpack (0.22; confidence interval [CI] = 0.15–0.31) was lower than apparent survival at high snowpack (90.65; CI = 0.50–0.78). Our findings highlight the potential for local environmental factors, like snowpack, to influence disease and host persistence, and demonstrate the ecological complexity of disease effects on population demography in natural environments. This work further emphasizes the need for improved understanding of how climate change may influence the relationships among pathogens, hosts, and their environment for wild animal populations challenged by disease.

Effect of snowpack on the soil bacteria of alpine meadows in the Qinghai-Tibetan Plateau of China

Global climate change is accompanied by changes in the amounts of ice and snow. These changes have both a direct effect on the plant community structure, primary productivity and carbon cycle and an indirect influence on the belowground ecosystem. However, the effects of changes in snowpack on the soil environment and belowground ecological processes, particularly in soil microbial communities are still poorly understood in alpine meadows. We conducted a field study of controlled snowpack in the eastern margin of the Tibetan Plateau, where five treatments were set up, named as S0, S1, S2, S3, and S4 (S1: the amount of a natural snowpack; S2, S3, and S4 were twofold, threefold, and fourfold of S1, respectively; and S0: completely removed snow). Soil physicochemical properties, soil community structure and diversity measured by 16S rRNA gene amplicons were studied. The results indicated that 1) as snowpack increased, the average soil temperature decreased, but soil moisture and soil compaction increased; 2) soil chemical properties (pH, available nitrogen, available potassium, available phosphorus, total nitrogen, total potassium, total phosphorus and total soil organic carbon) all changed as snowpack changed; and 3) increasing snowpack led to a decrease in the relative abundance of Acidobacteria, but Bacteroidetes and Actinobacteria did not decline in response to increasing snowpack. In summary, these results showed that soil bacterial communities are sensitive to changes in snowpack in alpine meadows.

雪被斑块对川西亚高山两个森林群落冬季土壤氮转化的影响

为了解气候变暖情景下雪况变化对高寒森林冬季土壤氮转化的影响，测定了川西亚高山冷杉（<em>Abies faxoniana</em>）+红桦（<em>Betula albo-sinensis</em>）混交林（MF）和冷杉次生林（SF）三类雪被斑块（浅雪被、中厚度雪被和厚雪被）内冬季土壤氮矿化特征。结果表明:经过一个冬季（2011-2012），两个森林群落土壤净氮氨化量都为负值，净氮硝化量都为正值，且净氮硝化量显著高于净氮氨化量；冬季土壤氮氨化、硝化、矿化和固持量都是中度雪被厚度最高，但各雪被斑块之间都未达到显著水平。各雪被斑块下，冷杉次生林土壤氮矿化参数都显著高于针阔混交林，但雪被斑块和林型交互作用对冬季土壤氮矿化无显著影响。这表明，该区冬季土壤氮矿化以硝化过程为主，硝化和氨化过程可能受不同微生物群落调控；短时期内，未来气候变化所导致的雪被减少对该区森林冬季土壤氮转化影响可能不明显。;A consensus in global ecology is that climate change is profoundly altering the process of terrestrial ecosystem. In particular, more and more attentions have been focused on the effects of snow pack on soil process in cold biomes recently, since climate change characterized by winter warming and extreme is changing the pattern of seasonal snow cover and freeze-thaw cycles in the high-latitude and high-altitute regions. As yet, the results concerning the effects of seasonal cover and freeze-thaw cycles on soil process remain uncertainty, and little information has been available on the effects of snow pack on soil nitrogen tansformation in the subalpine forest of western Sichuan, China. In order to deeply understand the process of soil nitrogen transformation in the subalpine forest of western Sichuan under climate change scenarios, therefore, wintertime net nitrogen mineralization, net nitrogen ammonification, net nitrogen nitrification and microbial nitrogen immobilization in soils under three depths of snowpacks (deep snowpack, middle snowpack and shallow snowpack) were measured in two subalpine forests of western Sichuan, which locates at the upper reaches of Yangtze River and the eastern Qinghai-Tibet Plateau. The top of soil columns sampled from<em> Abies faxoniana </em>+ <em>Betula albo-sinensis</em> mixed forest and secondary fir forest were closed, and then <em>in-situ</em> incubated in the forest floor under deep snowpack, middle snowpack and shallow snowpack of the corresponding forest from November 2011 to April 2012, respectively. The results indicated that wintertime soil net nitrogen ammonification ranged from -2.37mg/kg to -2.22 mg/kg under different snowpacks in the mixed forest, and from -7.73 mg/kg to -7.10 mg/kg under different snowpacks in the secondary fir forest. Wintertime soil net nitrogen nitrification varied from 71.98 mg/kg to 82.69 mg/kg under different snowpacks in the mixed forest, and from 101.56 mg/kg to 124.89 mg/kg under different snowpacks in the secondary fir forest. Net nitrogen nitrification was significantly (<em>P</em> < 0.05) higher than net nitrogen ammonification. The highest rates of soil nitrogen ammonification, nitrification, mineralization and microbial nitrogen immobilization were observed in the middle snow pack, but no significant (<em>P</em> > 0.05) differences were observed among snow packs. Meanwhile, all measured indexes in each snow pack were significantly (<em>P</em> < 0.05) higher in the secondary fir forest than those in the fir-birch mixed forest. However, the interaction of snow pack and forest type was not significant on wintertime soil nitrogen transformation. The results suggested that soil nitrogen nitrification be a major process of wintertime soil nitrogen mineralization, and the process of soil nitrogen nitrification and ammonification be regulated by different microbial communities in the subalpine forests of western Sichuan, China. The result also implies that the decline of snowpack caused by climate change, in the short-run, has little effects on soil nitrogen mineralization in our study area.

Effects of snowpack on early foliar litter humification during winter in a subalpine forest of western Sichuan

Aims Foliar litter humification is an important ecological process relating to soil carbon and nutrient budget in subalpine forest ecosystems, and the process of foliar litter humification can be affected by various snowpacks with different thicknesses in winter. However, little is known on the effects of snowpack on foliar litter humification. The objective of this study is to explore the effects of snowpack on early foliar litter humification during the first winter in subalpine forest. Methods A field litterbag experiment was conducted in a subalpine forest in southwestern China from November 2012 to April 2013. Air-dried foliar litter of fir (Abies faxoniana), cypress (Sabina saltuaria), larch (Larix mastersiana), birch (Betula albo-sinensis), willow (Salix paraplesia), and azalea (Rhododendron lapponicum) were incubated under snowpacks with varying thicknesses (deep snowpack, medium snowpack, thin snowpack, and no snowpack) due to variations in the canopy openness. Net accumulation of humus carbon, humification degrees, and humification rates were measured at snow formation, snow cover, and snow melt stage as foliar litter humification proceeded. Important findings Significant humification was observed in the six foliar litter types during the first winter regardless of the condition of snowpacks. The highest humification degree was observed in birch foliar litter (4.45%–5.67%), and the humification degrees were 1.91%–2.15%, 1.14%–2.03%, 1.06%–1.97%, 0.01%–1.25%, and 0.39%–1.21%, respectively, for fir, azalea, willow, larch, and cypress foliar litter under varying snowpacks. The net accumulation of humus carbon of all foliar litters increased at the snow formation, snow melt stage, and the whole winter, which exhibited an increasing tendency with the decrease of snow cover thickness. In contrast, net accumulation of humus carbon showed a declining trend at the snow cover stage, and significantly increased 倪祥银等: 雪被斑块对川西亚高山森林 6种凋落叶冬季腐殖化的影响 541 doi: 10.3724/SP.J.1258.2014.00050 with the decrease of snow cover thickness. In addition, correlation analysis results indicated that the humification degree was positively correlated with total nitrogen and acid-insoluble residues and negatively related to the organic carbon, total phosphorus, and waterand organic-soluble components. These results clearly suggest that foliar litter humification in subalpine forest can be enhanced by reduced snow cover in a scenario of climate warming, although the humification degree is controlled by snowpack and litter qualities at different stages of snow cover in winter.

Modeling the effects of snowpack on heterotrophic respiration across northern temperate and high latitude regions: Comparison with measurements of atmospheric carbon dioxide in high latitudes

Simulations by global terrestrial biogeochemical models (TBMs) consistently underestimate the concentration of atmospheric carbon dioxide (CO2 at high latitude monitoring stations during the non-growing season. We hypothesized that heterotrophic respiration is underestimated during the nongrowing season primarily because TBMs do not generally consider the insulative effects of snowpack on soil temperature. To evaluate this hypothesis, we compared the performance of baseline and modified versions of three TBMs in simulating the seasonal cycle of atmospheric CO2 at high latitude CO2 monitoring stations; the modified version maintained soil temperature at 0 °C when modeled snowpack was present. The three TBMs include the Carnegie-Ames-Stanford Approach (CASA), Century, and the Terrestrial Ecosystem Model (TEM). In comparison with the baseline simulation of each model, the snowpack simulations caused higher releases of CO2 between November and March and greater uptake of CO2 between June and August for latitudes north of 30° N. We coupled the monthly estimates of CO2 exchange, the seasonal carbon dioxide flux fields generated by the HAMOCC3 seasonal ocean carbon cycle model, and fossil fuel source fields derived from standard sources to the three-dimensional atmospheric transport model TM2 forced by observed winds to simulate the seasonal cycle of atmospheric CO2 at each of seven high latitude monitoring stations. In comparison to the CO2 concentrations simulated with the baseline fluxes of each TBM, concentrations simulated using the snowpack fluxes are generally in better agreement with observed concentrations between August and March at each of the monitoring stations. Thus, representation of the insulative effects of snowpack in TBMs generally improves simulation of atmospheric CO2 concentrations in high latitudes during both the late growing season and nongrowing season. These simulations highlight the global importance of biogeochemical processes during the nongrowing season in estimating carbon balance of ecosystems in northern high and temperate latitudes.

Effects of Snowpack on Timing and Abundance of Flowering in Delphinium nelsonii (Ranunculaceae): Implications for Climate Change

Delphinium nelsonii is an early-blooming herbaceous perennial of montane western North America, which we studied in dry subalpine meadows in the Colorado Rocky Mountains. We examined the effects of variation in annual snowfall between 1973 and 1989 on the timing and abundance of flowering. During years of lower snow accumulation, D. nelsonii plants experienced colder temperatures between the period of snowmelt and flowering. Also, flowering was delayed, floral production was lower, and flowering curves were more negatively skewed; damage during floral development probably occurred in years of low snowfall. If climate change results in decreased mean annual snowfall for the Rocky Mountains, then the seed production of D. nelsonii will probably be adversely affected. Decreased snowfall may also indirectly lower the seed production of later-blooming species by decreasing populations of bumblebees and hummingbirds that forage on D. nelsonii flowers. Decreased snowfall has the potential to reduce the number and relative proportions of species in the herbaceous flora in our study area.