Robert G. M. Hofstede

Impact of pine plantations on soils and vegetation in the Ecuadorian high Andes

Abstract A comparative study on the impact of pine plantations on soil and vegetation development was conducted in the Ecuadorian Andes (3000–4000 m). Pine plantations of different ages under different types of management were compared with extensively grazed páramo grassland (the most common former land use) and natural forest (the formerly dominant vegetation in much of the life zone). No general impact of plantations was found, although some tendencies were identified that show that soils under pine plantations are drier and less organic. Moreover, the vegetation under pine plantations was similar to páramo grassland, though some examples of regeneration of Andean woody species were observed, as well as examples of plantations where understory was completely lacking. We concluded that the impact of pine plantations cannot be generalized but should be evaluated case by case while care is taken in implementing plantations until more knowledge is obtained about the effects on the ecosystem as a whole, especially considering their ecological importance.

Upper forest line reconstruction in a deforested area in northern Ecuador based on pollen and vegetation analysis

Pollen analysis of a 150-cm-long core from Pantano de Pecho (0°20′S, 78°37′W) at 3870 m altitude in the Ecuadorian paramo documents altitudinal migrations and the composition of the upper forest line prior to deforestation. Four successive radiocarbon dates of 293 ± 41 14 C y BP, 498 ± 40 14 C y BP, 626 ± 33 14 C y BP, and 729 ± 44 14 C y BP show that the record includes the last c. 730 radiocarbon y, corresponding to the last c. 660 calendar years (cal y BP). The natural upper forest line was at a minimum altitude of 3400-3500 m between c. AD 1290 to 1315 (zone 1), from c. AD 1315 to 1350 at 3500-3600 m (zone 2), from c. AD 1350 to 1640 at 3600-3700 m (zone 3), from c. AD 1640 to c. 1765 at 3750 m (zone 4), and from c. AD 1765 to the present at 3700-3650 m (zone 5). The most important taxa were Alnus, Hedyosmum, Miconia, other Melastomataceae, Gunnera and Solanaceae. Since c. AD 1350 Podocarpus was continuously present with low abundance, but possibly not close to the upper forest line. Rarer elements of the upper montane forest were Dodonaea, Myrsine, Weinmannia, Myrica, Myrtaceae, Sapium, Juglans, Piper, Euphorbiaceae and Rubiaceae. Human disturbance and deforestation are shown by the presence of Rumex, Spermacoce pollen and charcoal particles. We surveyed the vegetation composition from isolated forest patches located between 3650 m and 4300 m. TWINSPAN analysis indicates forest patches up to 3950 m have a similar floristic composition to closed forest below the upper forest line. We argue that this apparent similarity does not necessarily mean that the slopes between 3750 and 3950 m were covered by closed forest in the past.

The effects of grazing and burning on soil and plant nutrient concentrations in Colombian páramo grasslands

The impact of extensive livestock farming on the physical and chemical characteristics of the volcanic soils and on the nutrient status of green plant tissues of neotropical alpine grasslands (páramo) is studied. Soil and plant samples were taken over a one-year period at five sites with different agricultural (grazing and burning) management. In the undisturbed páramo ecosystem, soil moisture (50–250%) and organic matter content are high (7–27%) and decomposition (11–35% yr-1) and element concentrations are low. Low temperatures (max < 10°C) and phosphorus fixation by the soil (5 mg P g-1 soil) determine the low mineralization and turn-over rates.Multivariate analysis of laboratory results indicates that the season of sampling and the agricultural practice are the most important explanatory factors for variation of soil characteristics. After long-term heavy grazing, soils have a higher bulk density and a lower moisture content. The outcome of a litterbag experiment confirms the hypothesis of higher decomposition rates at grazed sites. In the intermediate (wet-dry) season, conditions were somewhat better for plant growth but the system remained nutrient limited.Surprisingly, no relation between soil density, moisture or carbon content and concentrations of available nutrients in the soil is found. This is supported by the rather uniform nutrient concentrations in green plant tissue among the sites. It is concluded therefore that the effect of burning and grazing on páramo soils is principally restricted to physical characteristics, and that differences in chemical characteristics of the soil do not cause differences in vegetation structure between grazed, burned and undisturbed sites.

Alpine vegetation, plant distribution, life forms, and environments in a perhumid New Zealand region: oceanic and tropical high mountain affinities.

Macro- and mesoscale patterns of the full altitudinal range (1200–2200 m) of alpine vegetation and vascular flora on Mount Armstrong, on New Zealands perhumid Southern Alps, are deduced from 41 ve...

A Broad Transition from Cloud Forest to Páramo Characterizes an Undisturbed Treeline in Parque Nacional Llanganates, Ecuador

Abstract This study aimed at investigating the vegetation pattern associated with the transition from upper northern Andean cloud forest to páramo grassland in a relatively unmodified area in Ecuadors Eastern Cordillera. Single 20 × 10 m plots were randomly placed in representative sites along an altitudinal gradient from continuously wet Andean montane cloud forest at 3400–3700 m to páramo grassland at 3900–4000 m. Also sampled was a disjunct stand of the stem-rosette Espeletia pycnophylla var. llanganatensis, some 200 km south of the limit of the otherwise continuous distribution of this genus. Several physical and chemical soil factors, including temperature at -30 cm, were determined. Visual estimates of cover in four life-form classes (trees, shrubs, herbs, ground cover) at each site revealed similarities related to their relative proximity along an elevation gradient. Stands with a tree cover were more species-rich than those without, due largely to the differential distribution of the woody flora. No abrupt discontinuity occurred in the mix of species along this gradient. Soil temperature and altitude were the most important factors of those measured to explain the variability in plant community structure and composition. There was no clear zonation evident along the altitudinal gradient, with vegetation structure and floristics displaying continuous variation. No clear upper forest limit was differentiated. The isolated presence of Espeletia in the area is discussed, but the theory about its origin remains speculative.