Humid Mountainous Areas Research Articles

Patterns of human occupation during the early Holocene in the Central Ebro Basin (NE Spain) in response to the 8.2 ka climatic event

The Central Ebro River Basin (NE Spain) is the most northern area of truly semi-arid Mediterranean climate in Europe and prehistoric human occupation there has been strongly influenced by this extreme environmental condition. Modern climate conditions single out this region due to the harsh environment, characterised by the highest absolute summer temperatures of the Ebro River Basin. The Bajo Aragón region (SE Ebro River Basin) was intensively populated during the Early Holocene (9400–8200 cal yr BP) but the settlements were abandoned abruptly at around 8200 cal yr BP. We propose that this “archaeological silence” was caused by the regional impact of the global abrupt 8.2 ka cold event. Available regional paleoclimate archives demonstrate the existence of an aridity crisis then that interrupted the humid Early Holocene. That environmental crisis would have forced hunter-gatherer groups from the Bajo Aragón to migrate to regions with more favourable conditions (i.e. more humid mountainous areas) and only return in the Neolithic. Coherently, archaeological sites persist during this crisis in the nearby Iberian Range (Maestrazgo) and the North Ebro River area (Pre-Pyrenean mountains and along the northwestern Ebro Basin).

Satellite-based estimation of biomass carbon stocks for northeast China's forests between 1982 and 1999

Northeast China maintains large areas of primary forest resource and has been experiencing the largest increase in temperature over the past several decades in the country. Therefore, studying its forest biomass carbon (C) stock and the change is important to the sustainable use of forest resources and understanding of the forest C budget in China. In this study, we use forest inventory datasets for three inventory periods of 1984–1988, 1989–1993 and 1994–1998 and NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) data from 1982 to 1999, to estimate forest biomass C stock and its changes in this region over the last two decades. The averaged forest biomass C stock and C density were estimated as 2.10 Pg C (1 Pg = 10 15 g) and 44.65 Mg C ha −1 over the study period. The forest biomass C stock has increased by 7% with an annual rate of 0.0082 Pg C. The largest increase in the C density occurred in two humid mountain areas, Changbai Mountains and northern Xiaoxing’anling Mountains. Climate warming is probably the key driving force for this increase, while anthropogenic activities such as afforestation and deforestation may contribute to variations in the C stocks.

Effects of reforestation and deforestation on soil properties in humid mountainous areas: a case study in Wolong Nature Reserve, Sichuan province, China

Effects of reforestation and deforestation on soil properties in humid mountainous areas: a case study in Wolong Nature Reserve, Sichuan province, China

Effects of reforestation and deforestation on soil properties in humid mountainous areas: a case study in Wolong Nature Reserve, Sichuan province, China

Abstract. Natural secondary succession, forest planting and agricultural practices after deforestation affect soil properties in many ways. During the last 50 years, land uses have greatly changed in the mountainous areas in southwestern China as the result of deforestation and cultivation. A study was initiated in Wolong Nature Reserve, Sichuan province to elucidate the complex relationships in a humid mountainous region. Soil properties under six typical land use types (natural forest, grassland, shrub, secondary forest, cultivated land and reforested land) were compared. Significant differences between land uses were found for soil bulk density (BD), total nitrogen (TN), soil organic carbon (SOC), available phosphorus (AP) and available potassium (AK). Cultivated land had the lowest levels for most soil properties compared to other land uses and shrubland had a higher SOC, TN and available nitrogen (AN) than other land uses. Soils under grassland and shrub contained the greatest carbon mass (TC). Further studies on reforested land indicated that soil properties could be changed by length of reforestation. The SOC and TN in particular showed a linear relationship with years since reforestation. The results suggested that in an area of China where the climate favours secondary succession, ‘leave nature as it is’ is a better choice than the policy ‘change farmland to forest land ‘, especially for the mountainous regions where there is lack of labour and financial support.

Chemical weathering mechanisms and their effects on engineering properties of soft sandstone and conglomerate cemented by zeolite in a mountainous area

Sandstone and conglomerate cemented by zeolite crystals in a humid mountainous area in Japan are weathered, and also weakened or strengthened, by chemical interaction with percolating water that was originally in equilibrium with the atmosphere. Near the ground surface, carbonic acid generated by the dissolution of carbon dioxide from the atmosphere and biological activity in the soil dissolves zeolite, and thereby weakens the rocks. At the oxidation front, the base of the oxidized zone, oxygen from the atmosphere reacts with pyrite in the rock to form sulfuric acid and iron oxide and/or hydroxide. The iron oxide and/or hydroxide precipitates on zeolite surfaces, and strengthens the rocks by cementing the grains to each other. Beneath the oxidation front and extending to the dissolution front, sulfuric acid migrates downward, dissolves zeolite, and thus weakens the rocks. This weathering mechanism and the resulting changes in mechanical properties of rocks generally are to be expected in marine sandstone and conglomerate with small amounts of clay in the matrix because the most common cementing mineral is carbonate which is also easily dissolved by acid, and further because pyrite is a common rock-forming mineral in marine sedimentary rocks. The effects of chemical weathering on the mechanical properties of sandstone and conglomerate are different from those of mudstone, because the latter contains much larger amounts of clay minerals. The cementation of constituent grains by iron oxide and/or hydroxide is inhibited by clay minerals, because clay minerals have high specific surface areas, and also because large amounts of iron can be incorporated in the minerals.

A mechanism of chemical weathering of mudstone in a mountainous area

The chemical weathering of marine mudstone in humid mountainous areas of Japan is dominated by the oxidation of pyrite, a common mineral in marine sedimentary rocks. This process occurs at the oxidation front, that is the base of the oxidized zone, and sulfuric acid is formed. Chlorite is transformed into smectite due to the oxidizing and acidic conditions. As sulfuric acid migrates downward from the oxidation front, minerals are dissolved and components are leached out from the underlying dissolved zone, whose lower boundary is the dissolution front. The oxidation and dissolution fronts migrate downward as weathering progresses in mountainous areas.

Altitudinal Variation of Leaf Diffusive Conductance and Leaf Anatomy in Heliophytes of Montane New Guinea and their Interrelation with Microclimate

Summary This investigation in the humid-tropical mountains of New Guinea is part of a series of comparative studies about the altitudinal variation of physiological and anatomical leaf characteristics in different mountain regions of the world. The microscopic anatomical features and the diffusive conductance for water vapour in leaves of sclerophyll shrubs, dwarf shrubs, tussock grasses and herbs were studied in open habitats between 1,100 and 4,420 m altitude. Particular attention was directed to the Ericaceae family and the genera Rhododendron, Vaccinium and Gaultheria. The field studies were supplemented by simultaneous measurements of leaf and air temperature, air humidity and photon flux area density. The following results were obtained: As in altitudinal gradients in other mountains, plant size, leaf size and specific leaf area tend to decrease with increasing elevation. However, in contrast to the results of previous studies, maximum leaf conductance decreases with altitude in New Guinea. The diurnal variation of leaf conductance decreases. Stomatal frequency and particularly the ratio between the number of stomata and the total number of epidermal cells also decrease. The size of stomata does not change, as cell size in both epidermis and mesophyll does not reveal any significant change. The thickness of cell walls generally increases. This is most pronounced in the epidermis. Also cuticula thickness increases with altitude, but this does not lead to a lowered minimum leaf conductance. Comparing these results with those from other mountain areas it can be concluded that the leaf characteristics of plants from high altitudes can be divided at least in two groups: 1. Characteristics like size and scleromorphy of leaves, which tend to change in a similar manner in all mesic or humid mountain areas, more or less independently of the specific local climate, and are probably determined by direct or indirect effects of the mean temperature during leaf growth. 2. Characteristics whose altitudinal change is determined by climatic elements which are not generally coupled with altitude as for instance the dosis of photosynthetic active radiation received by a leaf (which drastically decreases with altitude in New Guinea). Maximum leaf conductance seems to be controlled largely by those factors. Temperature and partial pressure of CO 2 both declining similarly in all mountains, do not seem to be chief determinants for modification of leaf conductance with altitude. The study provides experimental evidence that similar altitudinal changes in the physiognomy of plants in mountain areas of different regions are not necessarily accompanied by similar physiological and anatomical alterations in the leaves.