Michael D. Morecroft

Air and soil microclimates of deciduous woodland compared to an open site

Forest microclimate has been monitored continuously for more than 3 yr at two sites in deciduous woodland at Wytham Woods, Oxford, UK. Automatic weather stations provided hourly data for wind speed, photosynthetically active radiation (PAR), vapor pressure deficit (VPD) and, in particular, temperature at different heights above the ground and at different depths in the soil. These data were compared with values from an open site at the same location. Air temperatures could be up to 3°C lower under the canopy than at the open site under sunny conditions in summer, but the differences averaged 0.6 and 0.9°C during the summer months and barely differed over winter. Effects of forest cover on soil temperatures were much greater and under the woodland they neither fell below 0°C nor rose above 20°C even at 5 mm depth, in contrast to temperatures under bare earth and grass. The temperature of a grass tussock at the soil surface under the canopy was intermediate between soil and air temperature; in comparison to grassland plants at an open site it experienced a much smaller range of temperatures. The differences between both soil and air temperature under the canopy and in the open were significantly correlated with solar radiation, presence or absence of canopy leaves and wind speed. Soil water content had no significant effect on soil temperature, partly because thermal diffusivity was relatively insensitive to it and partly because soil heat flux was small. Seasonal changes in canopy leaf cover caused a large peak of PAR under the canopy in spring prior to bud burst in trees and a much smaller one in the autumn after leaf fall. Wind speed under the canopy was also affected by the presence of leaves and was proportionally lower in summer and autumn than winter and spring.

The interactions between plant growth, vegetation structure and soil processes in semi-natural acidic and calcareous grasslands receiving long-term inputs of simulated pollutant nitrogen deposition

Regular applications of ammonium nitrate (35-140 kg N ha(-1) year(-1)) and ammonium sulphate (140 kg N ha(-1) year(-1)) to areas of acidic and calcareous grassland in the Derbyshire Peak District over a period of 6 years, have resulted in significant losses in both overall plant cover, and the abundance of individual species, associated with clear and dose-related increases in shoot nitrogen content. No overall growth response to nitrogen treatment was seen at any stage in the experiment. Phosphorus additions to the calcareous plots did however lead to significant increases in plant cover and total biomass, indicative of phosphorus limitation in this system. Clear and dose-related increases in soil nitrogen mineralization rates were also obtained, consistent with marked effects of the nitrogen additions on soil processes. High nitrification rates were seen on the calcareous plots, and this process was associated with significant acidification of the 140 kg N ha(-1) year(-1) treatments.

Protected areas facilitate species’ range expansions

The benefits of protected areas (PAs) for biodiversity have been questioned in the context of climate change because PAs are static, whereas the distributions of species are dynamic. Current PAs may, however, continue to be important if they provide suitable locations for species to colonize at their leading-edge range boundaries, thereby enabling spread into new regions. Here, we present an empirical assessment of the role of PAs as targets for colonization during recent range expansions. Records from intensive surveys revealed that seven bird and butterfly species have colonized PAs 4.2 (median) times more frequently than expected from the availability of PAs in the landscapes colonized. Records of an additional 256 invertebrate species with less-intensive surveys supported these findings and showed that 98% of species are disproportionately associated with PAs in newly colonized parts of their ranges. Although colonizing species favor PAs in general, species vary greatly in their reliance on PAs, reflecting differences in the dependence of individual species on particular habitats and other conditions that are available only in PAs. These findings highlight the importance of current PAs for facilitating range expansions and show that a small subset of the landscape receives a high proportion of colonizations by range-expanding species.

Scale‐dependent relationships between tree species richness and ecosystem function in forests

1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which represent a majority of global biomass, productivity and biodiversity.

Taxonomic homogenization of woodland plant communities over 70 years

Taxonomic homogenization (TH) is the increasing similarity of the species composition of ecological communities over time. Such homogenization represents a form of biodiversity loss and can result from local species turnover. Evidence for TH is limited, reflecting a lack of suitable historical datasets, and previous analyses have generated contrasting conclusions. We present an analysis of woodland patches across a southern English county (Dorset) in which we quantified 70 years of change in the composition of vascular plant communities. We tested the hypotheses that over this time patches decreased in species richness, homogenized, or shifted towards novel communities. Although mean species richness at the patch scale did not change, we found increased similarity in species composition among woodlands over time. We concluded that the woodlands have undergone TH without experiencing declines in local diversity or shifts towards novel communities. Analysis of species characteristics suggested that these changes were not driven by non-native species invasions or climate change, but instead reflected reorganization of the native plant communities in response to eutrophication and increasingly shaded conditions. These analyses provide, to our knowledge, the first direct evidence of TH in the UK and highlight the potential importance of this phenomenon as a contributor to biodiversity loss.

Plant Growth and Climate Change

Evidence grows daily of the changing climate and its impact on plants and animals. Plant function is inextricably linked to climate and atmospheric carbon dioxide concentration. On the shortest and smallest scales, the climate affects the plant’s immediate environment and so directly influences physiological processes. At larger scales, the climate influences species distribution and community composition, as well as the viability of different crops in managed ecosystems. Plant growth also influences the local, regional and global climate, through the exchanges of energy and gases between the plants and the air around them. Plant Growth and Climate Change examines the major aspects of how anthropogenic climate change affects plants, focusing on several key determinants of plant growth: atmospheric CO2, temperature, water availability and the interactions between these factors. The book demonstrates the variety of techniques used across plant science: detailed physiology in controlled environments; observational studies based on long-term data sets; field manipulation experiments and modelling. It is directed at advanced-level university students, researchers and professionals across the range of plant science disciplines, including plant physiology, plant ecology and crop science. It will also be of interest to earth system scientists.

Predictive systems ecology

Human societies, and their well-being, depend to a significant extent on the state of the ecosystems that surround them. These ecosystems are changing rapidly usually in response to anthropogenic changes in the environment. To determine the likely impact of environmental change on ecosystems and the best ways to manage them, it would be desirable to be able to predict their future states. We present a proposal to develop the paradigm of predictive systems ecology, explicitly to understand and predict the properties and behaviour of ecological systems. We discuss the necessary and desirable features of predictive systems ecology models. There are places where predictive systems ecology is already being practised and we summarize a range of terrestrial and marine examples. Significant challenges remain but we suggest that ecology would benefit both as a scientific discipline and increase its impact in society if it were to embrace the need to become more predictive.

Activity patterns of parent great tits Parus major feeding their young during rainfall

The influence of rainfall on the foraging patterns of Great Tit Parus major parents while feeding chicks at the nest was investigated using automated nest monitoring with electronic balances and photography. Great Tit females significantly reduced their visit rate to the nest during all rain intensities, while male feeding frequency did not significantly change. The female response was probably due to increased brooding requirements of young since the reduction in visit rate was most apparent at early nestling stages. At this time the chicks are incapable of thermoregulation and females significantly increased their nestbox occupancy time during rain. There was no indication that parents were compensating for periods of female inactivity during rainfall: there was no significant increase in visit rate following rainfall and no significant increase in prey size delivered to the nest during periods of rain. An analysis of data from six consecutive years revealed that the proportion of wet hours within the first week of the nestling period significantly influenced fledging weight in this species.

The effect of long-term nitrogen additions on the bryophyte cover of upland acidic grasslands

Abstract Regular applications of NH4NO3 (3.5–14 g N m−2 yr−l) and (NH4)2SO4 (14 g N m−2 yr−l) to areas of acidic grassland in the Derbyshire Peak District over a period of six years have resulted in marked changes in the abundance of the bryophyte species present on the site. A dose-related reduction in bryophyte cover, significant at all levels of nitrogen addition, was obtained after only one year of applications and this effect has been maintained over a further five years of treatment. (NH4)2SO4 additions at the same rate as the highest NH4NO3 input (14 g N m−2 yr−1) produced greater reductions in cover with losses of 80–95% compared with 45–55% for the 14 g NH4NO3 treatment. Soil pH measurements taken from cores collected in December 1994 showed a small reduction in the pH of the (NH4)2SO4 treated plots (4.03 compared with 4.41 for the controls), whereas the NH4NO3 treatments were unaffected. The mean stem density of the dominant bryophyte species Rhytidiadelphus squarrosus was significantly reduced at the lowest level of nitrogen addition and this was associated with marked increases in the total stem nitrogen content of this species. Pleurozium schreberi, present at much lower cover values, however showed no significant change except at the highest level of application, suggesting differential effects of the treatments on these two species. These results are indicative of significant losses in the bryophyte cover of acidic grasslands at atmospheric input rates of 5 g N m−2 yr−1 or less, and suggest that these species may be particularly at risk from the high atmospheric nitrogen deposition rates that are becoming a feature of many upland areas.

Environmental myopia: a diagnosis and a remedy.

Long-term ecological observation affords a picture of the past that uniquely informs our understanding of present and future ecological communities and processes. Without a long-term perspective, our vision is prone to environmental myopia. Long-term experiments (LTEs) in particular can reveal the mechanisms that underlie change in communities and ecosystem functioning in a way that cannot be understood by long-term monitoring alone. Despite the urgent need to know more about how climate change will affect ecosystems and their functioning, the continued existence of LTEs is extremely precarious and we believe that dedicated funds are needed to support them. A new non-profit organization called the Ecological Continuity Trust seeks to provide a solution to this problem by establishing an endowment that will be specifically earmarked to sustain LTEs as a scientific tool for the benefit of future generations.