Impact of Conservation Grasslands on Beneficial Insects in Adjacent Crop Fields

Kristen Tam Author

07/29/2021 Added

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Discovering the effects of native grasslands adjacent to crop fields, on beneficial insect populations.

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[00:00:02.420]Hello everyone.
[00:00:03.350]My name is Kristen Tam and I'm a rising junior
[00:00:05.920]at the University of California, Los Angeles,
[00:00:08.290]studying environmental science.
[00:00:10.310]And this summer I conducted my research
[00:00:12.510]under Dr. Julie Peterson
[00:00:14.540]on the impact of conservation grasslands
[00:00:17.410]on beneficial insects
[00:00:19.500]in regards to their location next to crop fields.
[00:00:24.730]My project focuses on the impact of native grasslands
[00:00:28.020]adjacent to these crop fields
[00:00:30.060]and the effects on beneficial insect population,
[00:00:33.060]abundance and diversity.
[00:00:35.140]Our hypothesis is that native grasslands
[00:00:37.480]will provide crucial shelter and nutrients
[00:00:39.950]for beneficial insects,
[00:00:41.820]such as lady beetles, carabids and spiders,
[00:00:44.270]which increases their possibility
[00:00:47.600]to have beneficial effects.
[00:00:49.300]First of all, you may well ask,
[00:00:51.800]why are insects important in these places?
[00:00:54.820]Well, insects are a large source of food for animals,
[00:00:58.410]such as birds.
[00:00:59.570]They can help decompose fecal waste into the soil
[00:01:03.190]and serve as predators, which eat harmful pests.
[00:01:06.300]Therefore these native grasslands
[00:01:09.380]can serve as a beneficial
[00:01:12.770]insect-pest management strategy
[00:01:15.240]to help consume harmful pests in the crop fields,
[00:01:18.150]such as Nebraska's infamous western bean cutworm.
[00:01:25.210]Native grasslands not only serve as critical habitats
[00:01:29.030]for pollinators and beneficial insects,
[00:01:31.430]but are a more water resilient source
[00:01:34.970]of biofuel input too.
[00:01:37.650]Nebraska is the second largest ethanol producer
[00:01:40.500]using more than 750 million bushels of corn per year.
[00:01:45.380]In the big picture, the study is looking at how,
[00:01:48.840]instead of solely relying upon corn as a biofuel source,
[00:01:52.640]which is non-native, annual
[00:01:54.300]and requires large sums of water and nitrogen fertilizer,
[00:01:57.810]the effects of planting native grasses adjacent to it too.
[00:02:01.920]And so this study focuses on the effects
[00:02:04.890]of native grasslands and the population density
[00:02:08.350]and diversity of the beneficial insects,
[00:02:10.540]such as lady beetles, spiders, carabids,
[00:02:12.980]bumblebees, moths and ants.
[00:02:14.590]And here we have a picture of a native grassland
[00:02:18.050]that we conducted research on
[00:02:19.930]as well as compared to the corn crop land.
[00:02:24.430]So this project has five key objectives
[00:02:27.140]to help create the holistic picture
[00:02:29.230]of arthropod abundance and diversity.
[00:02:33.670]The first are that we set up
[00:02:38.500]three sets of yellow sticky cards and pitfall traps
[00:02:42.100]in the five farms that we conducted research on,
[00:02:45.650]which we set up in three different locations,
[00:02:48.810]the grasslands, the adjacent, which was 10 meters
[00:02:52.820]in to the cropland from the edge of it,
[00:02:56.920]as well as the cropland,
[00:02:58.680]which was 10 meters away
[00:03:00.190]from the center pivot in the cropland.
[00:03:03.570]After setting up
[00:03:05.950]each of these three different survey methods,
[00:03:09.840]we left the yellow sticky cards and pitfall traps out
[00:03:14.220]for three to five days and then collected them,
[00:03:19.100]brought them back to the lab
[00:03:20.470]and they were analyzed
[00:03:21.730]for the different arthropod abundance.
[00:03:25.300]The second component was the pollinator surveys
[00:03:30.170]that we conducted to look at pollinator abundance.
[00:03:33.730]So to do this,
[00:03:35.310]I conducted a five-minute survey,
[00:03:38.700]analyzing and surveying the different pollinators
[00:03:43.280]around the grasslands, the crop and adjacent
[00:03:46.460]to see the abundance,
[00:03:47.410]as well as which species of plants they were pollinating.
[00:03:51.820]And the last two components during the collection period
[00:03:56.440]that we conducted,
[00:03:59.380]were the vegetation
[00:04:01.180]and western bean cutworms scouting surveys.
[00:04:04.260]For the vegetation, we looked at the percentage
[00:04:06.580]of forb grass, crop, bare ground and litter
[00:04:09.450]in each of the three locations,
[00:04:11.440]as well as for the western bean cutworm scouting,
[00:04:15.730]we took 15 corn stocks and the crop
[00:04:18.130]in adjacent locations looking for egg masses of this moth.
[00:04:24.080]After the data samples were collected,
[00:04:27.270]the data was inputted into Excel sheets,
[00:04:30.330]and then these sheets were,
[00:04:33.610]the data was standardized per 24 hours
[00:04:36.790]using a generalized linear mixed models
[00:04:42.018]with a negative binomial distribution in SAS
[00:04:45.750]or SAS 9.4.
[00:04:47.810]And then after running this model,
[00:04:49.690]if the least squared means had a significant P value,
[00:04:53.590]less than 0.05,
[00:04:55.960]we deemed the variables
[00:04:58.070]to be statistically significant.
[00:05:01.750]Our yellow sticky cards showcased that
[00:05:05.560]for total beneficial arthropod abundance.
[00:05:08.200]So the total sum of all the arthropods collected
[00:05:11.480]as well as for the most common individual groups,
[00:05:14.400]which were Areneae, spiders,
[00:05:17.070]and Coccinellidae, lady beetles.
[00:05:20.620]SAS showed us that there was a significant effect
[00:05:24.170]of sampling period as shown in this table below.
[00:05:30.630]Our pollinators sampling showed us that in the grasslands,
[00:05:34.700]the most common species were bumblebees,
[00:05:38.050]Lycaenidae, Pieridae,
[00:05:40.190]which are both types of butterflies and Syrphidae,
[00:05:43.730]which is a type of hoverfly.
[00:05:46.150]And that these species
[00:05:47.810]were most commonly pollinating wild alfalfa,
[00:05:50.890]thistle or yarrow.
[00:05:53.580]Our western bean cutworm scouting showed us
[00:05:57.270]that the amount of egg masses in the crop location
[00:06:00.590]was at or above the economic threshold for farmers to spray
[00:06:04.970]for the western bean cutworm,
[00:06:06.410]which is very significant while the number of egg masses
[00:06:10.480]on the adjacent crops
[00:06:11.790]were below the economic threshold.
[00:06:15.960]Our pitfall traps showcased
[00:06:18.800]that there was a significant effect of location
[00:06:23.280]on the total beneficial arthropod abundance,
[00:06:26.890]Carabidae abundance,
[00:06:28.390]as well as the Araneae abundance.
[00:06:31.390]This means that there were a larger,
[00:06:36.893]that grass versus adjacent versus cropland,
[00:06:39.710]that there were significant differences
[00:06:41.700]in the number of species per each of those.
[00:06:46.330]And in addition,
[00:06:47.163]there was a significant effect of location by period
[00:06:50.720]on the Araneae, which is showcased
[00:06:52.390]in the bottom right graph.
[00:06:55.520]For vegetation sampling,
[00:06:57.170]the grassland location was mostly comprised of grass,
[00:07:00.370]forb and litter
[00:07:01.570]while the adjacent and the crop location
[00:07:04.170]were mostly comprised of bare ground, crop and litter.
[00:07:09.090]And so we don't know what everything
[00:07:12.170]from the state of collected means,
[00:07:13.730]but here are a few important takeaways that we can conclude.
[00:07:16.990]First of all, the pitfall data
[00:07:18.310]showcases higher arthropod abundance in grasslands,
[00:07:21.660]which supports our hypothesis
[00:07:23.240]that grasslands provide critical habitats for arthropods,
[00:07:26.800]therefore increasing their abundance,
[00:07:28.440]which can lead to positive effects,
[00:07:30.170]such as consumption of harmful pests, pollination,
[00:07:32.870]and dung decomposition.
[00:07:34.880]Secondly, although the Carabidae collected
[00:07:38.000]was opposite from what we expected,
[00:07:40.410]there were more in the corn, in the crop
[00:07:43.010]and adjacent than the grasslands,
[00:07:45.160]this may well be because there is more bare ground
[00:07:48.350]in the crop and adjacent,
[00:07:49.960]which was supported by our vegetation samples.
[00:07:53.620]Finally, the higher number
[00:07:54.990]of western bean cutworm egg masses observed in the crop
[00:07:58.130]versus adjacent locations showcased that,
[00:08:03.890]there are higher levels of egg masses
[00:08:06.500]in the crop versus adjacent,
[00:08:08.890]which means that the adjacent next to the grass
[00:08:12.540]has the potential to reduce the likelihood
[00:08:14.850]that farmers may need to spray pesticides,
[00:08:18.110]further supporting
[00:08:19.960]why we should be planting more grasslands.
[00:08:23.170]This research will be,
[00:08:25.370]is just a glimpse of what,
[00:08:29.720]future scholars
[00:08:32.710]and other students will be conducting
[00:08:34.540]to collect data on the abundance of arthropods
[00:08:38.270]and the ecosystem services that they can have
[00:08:40.670]due to grasslands next to croplands.
[00:08:44.700]Thank you so much for listening.
[00:08:47.650]I would like to thank Dr. Julie Peterson
[00:08:49.700]for her mentorship and support
[00:08:51.860]in conducting this research,
[00:08:53.090]as well as the help of lab workers, Rachel, Ruby,
[00:08:58.430]Angel, Kaisa and Andrea for their help
[00:09:00.360]in my field collections as well as funding
[00:09:02.750]from the department of energy and the USDA.
[00:09:05.947]Thank you.

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Impact of Conservation Grasslands on Beneficial Insects in Adjacent Crop Fields

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