Upland Heath Research Articles

Monitoring of pollen rain in moss polsters and mats in view of their suitability as controls for determining the air-borne component of pollen spectra in herbivore faeces

Pollen has been extracted from six bryophyte and two lichen taxa, sampled from three habitats: upland heath, lowland bog and mixed woodland, in both west and east Scotland. The highest number of pollen taxa was recorded in bothSphagnum andThuidium; the lowest numbers of pollen taxa were recorded in two of the mosses and both lichens. For pollen rain control purposes in herbivore faecal studies, woodland species of bryophytes are not suitable due to the sheltering effects from rain provided by the overhead canopy. Open habitats such as moorland heath and bog provide polsters/mats which normally trap pollen rain more effectively for control purposes. The aim of this study was twofold: to observe the effectiveness of selected polsters and lichens as traps for pollen rain and to establish eventually, whether or not such vegetative traps could be used as controls in pollen spectra analyses of herbivore faeces for the determination of nutritional regime and habitat. From a comparison with recent studies in north west Spain of three taxa in common with Scottish samples,Polytrichum demonstrated a consistently higher number of pollen taxa trapped.Thuidium andCladonia all yielded between one and a half and three times the number of pollen taxa as in the same three bryophyte/lichen taxa sampled in Scotland. Investigation relating the pollen rain trapped in polsters to that in faecal material are continuing, and will be reported in due course.

Total, organic and extractable-P in humus and soil beneath Sitka spruce planted in pure stands and in mixture with Scots pine

Total, organic and extractable P were measured in the humus and underlying soil to 10 cm depth beneath Sitka spruce (SS) and mixed Sitka spruce and Scots pine (SS+SP) stands planted on upland heath. The humus beneath SS+SP contained significantly (p<0.01) greater amounts of total and organic-P than that in SS and the mixed stands had more effectively retained approximately 87 per cent of previously applied fertilizer-P, totalling 100 kg P ha−1, compared with 70 per cent in SS. Despite the larger amounts of total-P in the mixed plots 0.01 M CaCl2 extractable molybdate reactive phosphorus (MRP) was significantly (p<0.05) greater in SS+SP humus only during March and April. Greater concentrations of MRP were released from the humus and soil during July and August at a mean rate of 58 g P ha−1 day−1. This coincided with drying of the soil during the summer and the rate of release, attributed to death of fine roots and microorganisms, was 4 to 30 times greater than reported values for rates of net mineralization of P from forest soils.

Nutrient limitation of the long term response of heather [Calluna vulgaris (L.) Hull] to CO2 enrichment

summaryIn a 27‐month CO2‐enrichment experiment, Calluna vulgaris plants were grown on peat obtained from an upland heath in NE Scotland and given a nutrient supply which mimicked that in precipitation in the area. Three CO2 concentrations were used; ambient, +100ppm and +200ppm. Calluna showed a negative growth response to increased CO2 over the first year of treatment and a positive response by the end of the experiment. Final above–ground biomass was greatest in the enriched CO2, treatments, showing an increase of 30 °0 in + 100ppmCO2. Determination of tissue nutrient concentration, and calculation of total nutrient uptake, demonstrated that nutrient uptake did not increase with increased growth, resulting in significant dilution of elements in leaf tissue. This suggests that, in its typical, nutrient poor habitats, the growth response of Calluna to CO2 will be limited by nutrient deficiency, and will reach a maximum with a relatively small increase in CO, concentration. Flowering was advanced and extremely prolific in +100 ppm CO2 grown plants, but the ecological significance of this is uncertain. The results highlight the need for long term studies of native species on their natural soils, using lower CO2 concentrations than the usual ‘double CO2’.

Ground Beetle (Coleoptera: Carabidae) Communities on Upland Heath and Their Association with Heathland Flora

Ground beetle communities from sixty-two sites on Calluna-dominated heath within the North York Moors National Park were sampled using pitfall traps. The resulting datasets were ordinated by Detrended Correspon- dence Analysis (DECORANA) and classified by Two Way Indicator Species Analysis (TWINSPAN) and fuzzy clustering. 2. Ordination indicated that the distribution of carabid species between sites was influenced by site wetness and vegetation development. Both classifications indicated a separation between carabid species from wet sites and those from Calluna-dominated sites. Fuzzy clustering also revealed characteristic carabid communities associated with the different development phases of Calluna. 3. A good correlation was found between the fuzzy clus- tering classifications of ground beetles and plants from the same series of sites. However, knowledge of one set of data cannot be used to predict the other. 4. Results are discussed with respect to the conservation of carabid communities and current management practices prevailing within the National Park.

A comparison of the fine root component of a pure and a mixed coniferous stand

Fine roots were sampled at monthly intervals during 1984–1985 in pure plots of Sitka spruce (Piceasitchensis (Bong.) Carr.) and mixed plots of Scots pine (Pinussylvestris L.) and Sitka spruce established on an upland heath in 1969. Both types of planting had received phosphorus and potassium fertiliser but no nitrogen. The mean standing crop of live roots (&lt;2 mm diameter) in the top 5 cm of pure spruce plots was 112 g • m−2, almost double that of mixed stands (37 g • m−2 of spruce plus 20 g • m−2 of pine). Necromass was 80% of total mass in both stand types. Concentrations of nitrogen and phosphorus were greater in pure plots than in mixed plots, but fine root capital of nitrogen, phosphorus, and potassium was greater in pure spruce than in mixed plots (biomass and necromass contained 11, 2, and 5 and 45, 4, and 7 kg • ha−1 of nitrogen, phosphorus, and potassium, in pure plots, and 7, 1, and 3 and 30, 3, and 3 kg • ha−1 of nitrogen, phosphorus, and potassium in mixed plots, respectively). Production of fine roots in pure and mixed stands was estimated at 181 and 97 g • m−2•year−1 or 715 and 367 g • m−2•year−1, respectively, depending on the method of calculation. Fine roots of pure plots were highly concentrated in the top 3 cm. In mixture, spruce roots had a less extreme vertical distribution and pine roots were more evenly distributed down to 9 cm.

MYCORRHIZAL INFECTION OF BETULA PENDULA AND ACER PSEUDOPLATANUS: RELATIONSHIPS WITH SEEDLING GROWTH AND SOIL FACTORS.

Mycorrhizal infection of two-year-old seedlings of Betula pendula Roth, and Acer pseudoplatanus L. was examined in a pot experiment, in relation to several soil variables (pH, organic matter, N, P, K, Ca, Fe, and phosphatase activity), host uptake of 32 P, and plant performance (height and weight), in 25 Cumbrian soils from natural and semi-natural habitats (such as woodland, carr and upland heath). Soils were used in a fresh state to maintain indigenous mycofloras and seedlings were raised from several seed-lots to include possible ecotypic variation. Infection (incidence and intensity) of both 'immature' and 'mature' mycorrhizas was estimated. Most plants were mycorrhizal, ectomycorrhizas occuring on Betula and vesicular-arbuscular (VA) endophytes in Acer. Differences in the degree of infection between soils, but not between seed-lots, were highly significant. Infection of one or both species was highly correlated with several soil factors (pH, organic matter, phosphorus and iron), and with all the plant variables. In Betula, evidence for most of these relationships was obtained only from 'immature' mycorrhizas, suggesting early physiological activity. Mycorrhizas accounted for a small but significant proportion of the variation in growth of both hosts, and soil properties accounted for a high proportion of the variation in both the plant growth and mycorrhizal infection, as shown by multiple regression analyses. Growth of Acer appeared to have a greater influence than soil factors on the variation in VA infection. 'Beading' of Acer roots was negatively correlated with plant weight and soil phosphorus, suggesting a morphological response to P- deficiency. Possible causal relationships between hosts, fungal symbionts and soils are discussed.

An Experiment in Intensive Cultivation of an Upland Heath

Results at 30 years are reported for a cultivation experiment on an upland heath with a podzolic ironpan soil with indurated subsoil. The main species tested were Scots pine and Japanese larch and lodgepole pine, the latter two species in mixture. Cultivation included two spaced furrow ploughing treatments, two shallow complete and two deep complete ploughing treatments. For the first 8 or 10 years height growth was rapid in all treatments, with the deep complete ploughing giving greatest response. In the next 10 years height growth was much slower and the order of the treatments was temporarily reversed. At 30 years height differences between treatments are small but differences in volume production between the best and the poorest treatment are about 20 per cent. In the unplanted heathland the soil above the ironpan is frequently waterlogged and has small concentrations of oxygen; under the forest waterlogging does not occur and the soil is now well areated.

Transpiration and evaporation from heather Moorland

The energy balance of an upland heath dominated by heather (Calluna vulgaris) was measured in dry and wet weather. Median values of both transpiration and evaporation rates were ca. 2 mm hr-1. The median Bowen ratio for the dry canopy was 2.0 and for the wet canopy 0.6. On dry days the median value of the saturation deficit was only 3.8 mb and that of the climatological resistance was 30 s m-1. The bulk stomatal resistance increased from ca. 50 s m -2 in the morning to over 290 s m-1 in the afternoon with an overall median value of 110 s m-1. Transpiration from the dry canopy was controlled by a combination of small saturation deficits and large stomatal resistances. The median value of the boundary-layer resistance of the canopy was 22 s m-1 and was low partly because of a large low-level drag coefficient. Saturation deficits on wet days were close to zero and evaporation of intercepted water proceeded at close to the equilibrium rate, being largely limited by the low fluxes of available energy. The water loss from heather was compared with simulated losses from coniferous forest, herbaceous crops and grassland in the same conditions to evaluate the effects of vegetation on water loss from catchments.

Effects of Intensive Forestry Ploughing Practices on an Upland Heath Soil in South East Scotland

Effects of Intensive Forestry Ploughing Practices on an Upland Heath Soil in South East Scotland

The Effects of Cultivation Treatment on Water Potential and Soil Aeration in Wet Heathland with Special Reference to Afforestation

In Britain extensive areas of upland heath have been afforested with coniferous tree species. Most of the land acquired for this purpose is of marginal agricultural value supporting ericaceous plants or moorland grasses like Molinia on the less degraded sites. The purpose of afforestation is primarily economic. At the same time well-managed forests are ultimately of considerable amenity value. The fulfilment of both the economic and amenity roles depends upon successful establishment of the crop in what is normally an alien environment. Cultivation of the area to be afforested is a pre-requisite for success since it temporarily weakens the competitive effects of the established flora. It should also improve the drainage and aeration of the soils. The most widely used method of cultivation is deep single-furrow ploughing. An experimental modification of this method known as deep complete ploughing has also been employed (Zehetmeyer 1960). However, these traditional methods have sometimes failed to produce successful coniferous crops and have often produced plantations that were inherently unstable and liable to wind throw. This is especially true in wetter upland zones where combinations of exposure, high rainfall and high water-holding capacity of the soil have made adequate soil amelioration using traditional methods extremely difficult. One such difficult area is found in North Yorkshire where extensive afforestation has occurred on Calluna-dominated gley-podsolic soils derived from Estuarine Clays of the Middle Jurassic period. Because of these problems Weatherell (1965) established an experiment at Rosedale (map ref. NZ 765967) designed to compare tree growth achieved by traditional cultivation techniques with that of a treatment new to British forestry. The new treatment involved the construction of elevated cambered beds or 'riggs' separated by lower furrows or 'urrs'. This treatment has a structure designed to increase run-off, improve drainage and also, since the top of the rigg is elevated above the original surface, to increase the potential rooting depth available above the water table. If these objectives are achieved more successful establishment of the trees should result, followed by greater stability of the mature crop. Riggs have been extensively used in agricultural practice in the past and are still employed in afforestation programmes in Northern Europe (Barelmann 1963). The purpose of the present investigation has been to obtain a comparative assessment of the early effects of different treatments on some important soil characteristics. Emphasis has been placed on soil water potential and soil aeration since these represent the physical parameters most likely to be of importance both for tree establishment and for subsequent crop stability. While the success or failure of any treatment must ultimately

COMPARISONS OF GRASS VARIETIES FOR SURFACE SEEDING UPLAND PASTURE TYPES

A study was made of the agronomic behaviour of 18 grass varieties, surface sown, after burning an upland heath community dominated by Calluna vulgaris. Complete exposure of the soil surface, the absence of competition and favourable moisture conditions provided excellent conditions for establishment. Despite this, sward development was slower than at any other site studied, and 18 months elapsed before satisfactory sward densities, and consequently a reasonable level of production, were achieved. In contrast, white clover developed vigorously from the outset. The red fescues, cocksfoots and S170 were the most promising, while the performance of most varieties was affected by one or more hazards such as frost‐heaving and summer drought. The latter aggravated the tendency of some of the varieties to produce a profusion of flowering stems and, with few exceptions, considerably reduced the colour and vigour of the herbage.