Thursday, 9 November 2017

Outline of Invertebrate Diversity Monitoring Project - The Polyculture Study 2017

Prepared by:

1. Project Aims
The survey aims to:
1. Provide baseline data on the diversity of insect species on selected plots managed by the Balkan Ecology Project.
2. Provide ongoing monitoring of insect diversity on the surveyed plots and attempt to relate changes to plot management.
2. Survey Timings
Three surveys are planned for 2017. The first was carried out on the 2nd and 3rd of May. The second survey is planned for late June. The Final 2017 visit is planned for mid-August. The survey timings have been selected to ensure good survey coverage over late spring and summer, periods of maximum invertebrate activity. In an ideal survey extra time would be allotted in April and September/October to record early spring and autumn species. Unfortunately restraints in time and resources have limited the project to three survey visits and it is intended to carry these out when the maximum insect diversity will be recorded.
For the aim of monitoring insect diversity to be achieved repeat visits in future years will be necessary. Ideally these will take place over the same dates as the 2017 survey visits. In practice the exact date is likely to differ somewhat due to external factors, every attempt will be made to ensure that survey dates are as consistent as possible.
3. Survey Plots
3.1. Plot A: Market Garden

The Market Garden is a well established and relatively complex plot supporting a range of habitats. Roughly 2/3 of the plot area is given over to agriculture. Half of this is polyculture beds used to grow a variety of vegetable crops. The other half is a forest garden. The market garden has been divided into three sub-plots for the purposes of sampling:
Sub-plot 1 - Forest Garden: Young planted fruit trees over a mix of native grass and herb species similar to that found in the Permaculture beds. There were some more mature trees providing shade in places but much of the sub-plot was open.
Sub-plot 2 - Polyculture beds: Rows of cultivated ground for a variety of vegetables. The plots were still straw over bare soil during the May visit. There are numerous wooden growth supports present in the plots which were noticeably being utilised by dead-wood nesting bees and wasps. Between plot rows there are grassy pathways with fringes of native flora, dominated by red dead-nettle (Lamium purpureum). A pond is present at the edge of the area and is surrounded by a patch of coarse grassland with a significant herb component and numerous flowering plants. Overall, the flora in the non-cultivated areas is closest to that observed in woodland glades and rides nearby.
Sub-plot 3 - Scrub:  An area of relatively dense scrub and small trees containing a mix of species but dominated by Prunus sp. and Malus sp.. There is also a large Poplar (Populus sp) shading much of the area. The understory, where scrub was not so dense as to shade it out, was composed of grasses and woodland herbs. There is a damp area due to run-off from the neighbouring road that has been planted with Yellow Flag (Iris pseudacorus) and reed (Phragmites australis), although this is still in its infancy. Deadwood is fairly limited in this sub-plot.

3.2. Plot B: Perennial polyculture trial garden

A recently acquired plot of land composed of coarse, unimproved grassland with scattered Rose (Rosa sp.) bushes surrounded by a well established hedge dominated by Elm (Ulmus sp.) and Hawthorn (Cratageus sp.). A large mature Walnut is present in the corner of the plot. Previous management was by goat grazing. Since acquisition of the plot a reasonably sized pond has been dug, but not yet filled, and several polyculture beds have been created. This plot was divided into two sub-plots for the purposes of sampling:
Sub-plot 4 – Grassland: This is currently a homogenous area supporting coarse unimproved grassland with a relatively limited herb component. Scattered low rose (Rosa sp.) scrub was present across the plot. The most frequent flowering plant in the sub-plot during the May survey was a speedwell (Veronica sp.) which occurred in localised but dense patches throughout the sub-plot.
Sub-plot 5 – Hedgerow: The plot was surrounded on three sides by a large, mature, hedge. The principal tree species present were Elm (Ulmus sp.) and Hawthorn (Cratageus sp.). There were also significant components of smaller shrubs, predominantly bramble (Rubus sp.), blackthorn (Prunus spinosa) and rose (Rosa sp.). Although deadwood was present it was generally sparse and of small diameter.
4. Target Groups
Bulgaria is a country of great biodiversity and, compared to most Western European countries, the insect fauna is relatively poorly known. In order to ensure that identification of collected species was practical within the limited time available for the project it was necessary to select a relatively narrow set of target groups. The criteria used to identify useful groups are outlined below:
  1. The group must have a reasonably well understood ecology, preferably one directly relatable to agricultural practices, in order to allow changes in composition or diversity to be related to external factors.
  2. The group must be relatively sedentary to ensure that changes in composition or abundance are likely to be related to changes in the survey plot.
  3. Species within the group must be identifiable using available literature.
  4. The group must be well known to the surveyor (Christopher Kirby-Lambert) to ensure efficient and accurate collection and identification.
  5. The group must be abundant and reasonably diverse in the survey plots to ensure that any recorded changes in composition and diversity reflect genuine changes and are not simply sampling artefacts.
After extensive investigation of the available literature and consideration of the value and ease of recording a wide range of groups, coupled with direct experience of the plots, the following taxa were selected for monitoring:
  1. Coleoptera (beetles): This encompasses a vast range of species with widely differing ecologies, however, the basic ecological niches of many groups are well established and they have been relatively well studied in Europe. In addition the group as a whole is well known to the surveyor and many species are likely to be identifiable to species. In practice the most frequently encountered beetle group in the survey plots by a wide margin were leaf beetles (Chrysomelidae). These species are invariably phytophagous (plant-eating), feeding on living plant tissue. They are often specific to certain plant species or families and so are generally ecologically informative. Weevils (Curculionoidea) were also collected in some numbers and have similar ecological niches. Other groups of beetles collected include saproxylic species that depend on deadwood resources for larval development and tend to feed on pollen from flowers and predatory species.
  2. Hemiptera; Heteroptera: Another group that has been relatively well studied in Europe and is relatively well known to the surveyor. The Heteroptera include a wide range of families with varying ecologies. Most of those encountered were predominantly phytophagous and ranged from generalists to specialists on particular plant species.
  3. Hymenoptera; Aculeata: The aculeates include bees (Apoidea), ants (Formicidae) and a number of wasp families, all groups that are well known to the surveyor. Ants are ground or tree nesting and mostly predatory (although some European species will eat seeds). Bees feed on nectar (as adults) and pollen (as larvae) so are entirely dependent on flower resources for food. They nest variously in dead wood, bare ground and soil, and moss (many species are cuckoos, stealing the nests of the host species). Wasps are predatory and nest in a similar range of habitats as bees.
5. Survey Methodology
The field survey methodology utilises a number of widely used collection techniques that, in combination, collect species from most groups present on a site. The use of these techniques is dictated by the habitats present on each plot and roughly follows Natural England’s Common Standards Monitoring (CSM) guidelines1. These guidelines are intended for use in monitoring the quality of Sites of Special Scientific Interest (SSSI’s) in the UK. See Table 1 for a breakdown of the survey methods used on each sub-plot. The total survey time devoted to each sub-plot was the same.
The analysis component of the CSM is inapplicable in this case due to the lack of knowledge of the scarcity and ecological requirements of most Bulgarian Insect species. Analysis of the data collected is likely to be based on the calculation of diversity indices but the exact methodology will largely depend on the data collected.
5.1. Field survey techniques
Sweep netting
A lightweight folding circular aluminium frame 40 centimetres in diameter was fitted with a net bag supplied for sweep-netting by GB Nets and attached to an extending lightweight aluminium handle. Net strokes were reasonably rapid, and penetrated as far into the vegetation as possible without the stroke being seriously slowed by its resistance. A maximum of fifty sweeps (counted as single strokes of the net) was taken before examining the catch. The sample was initially examined in the net, noting or capturing large, fast-moving or readily identified species. The remaining net contents were then emptied onto a white tray, and the material in the tray examined for smaller and slower animals. 10 minutes of survey time was devoted to sweep-netting per sub-plot.
Targeted netting
Large, active, species, especially those prone to visiting flowers, resting on leaves, or with regularly visited and recognisable nests, are often most effectively recorded by netting individual animals. This is particularly effective for solitary bees and wasps, but also for some groups of flies. When utilised 30 minutes survey time per sub-plot was devoted exclusively to it. On those occasions, the net used for sweep-netting was employed
Vegetation beating
Samples were taken from tree and shrub foliage, ivy, and dense, tall herbaceous vegetation by holding a net under the foliage and tapping the branches or stems above sharply several times with a stout stick. The sweep net currently in use was most often employed for this purpose. For high vegetation and larger branches, a net with a lightweight folding frame 55 centimetres in diameter and a long bag was also used. This net has the advantage that substantial amounts of foliage can be inserted, or a substantial length of tall vegetation placed next to the net, before sampling. Material was initially examined in the net, then emptied onto a white tray for further sorting. When utilised 30 minutes survey time per sub-plot was devoted exclusively to it.
Active search
Features of significance to invertebrates which are not sampled, or not necessarily adequately sampled, by sweeping, beating or suction sampling were investigated by close examination and hand searching. Attention was particularly paid to: accumulations of plant litter; dead wood; the ground beneath wood, stones and other debris; fungal fruiting bodies; tree trunks; the undersides of plant rosettes; and bare wet ground. When utilised 30 minutes survey time per sub-plot was devoted exclusively to it.

Table 1. Distribution of sampling effort across plots. X denotes that the technique was used in the sub-plot in question.

Plot A (Market Garden)
Plot B (New Plot)

Sub-plot 1
Sub-plot 2
Sub-plot 3
Sub-plot 4
Sub-plot 5
Sweep-netting (10 mins)
Targeted netting (30 mins)


Beating (30 mins)


Active search (30 mins)
Total survey time
110 mins
110 mins
110 mins
110 mins
110 mins

6. References

Drake, C.M., Lott, D.A., Alexander, K.N.A. & Webb, J. (2007).  Surveying terrestrial and freshwater invertebrates for conservation evaluation. Natural England Research Report NERR005. Sheffield: Natural England.

No comments:

Post a Comment