Soil Ecology and Research Group last update December 23, 2002

Los Peñasquitos Canyon Flower Field Study
July 2002

SUMMARY

During July of 2001, the Friends of Los Peñasquitos Canyon Preserve organization, hereby referred to as “Friends”, was awarded funding through the San Diego Foundation to implement an experiment testing cost effective methods in native ecosystem restoration within San Diego. The major objective was to restore lands disturbed by historical agriculture and grazing to native grassland and flower fields. The Friends and the Soil Ecology and Restoration Group (SERG) have collaborated on all tasks outlined in the grant proposal. The key focus of the experiment is to determine chemical and physical soil requirements for optimal native grassland transplant survival and growth. Analyses will examine the success of native container plant survival and growth will be compared using several treatments considered effective. Maintenance and monitoring will begin immediately following completion of transplanting and continue for two to three years. Collected data will be statistically analyzed to determine significant differences between treatments for both above ground and below ground parameters.

Two highly degraded sites within Los Peñasquitos Canyon Preserve were chosen for the experiments. The two sites together comprise a total area of approximately half an acre. Site #1 was dominated by non-native storksbill, Erodium cicutarium, while site #2 was dominated by non-native wild oat, Avena fatua.

During the spring and summer of 2001, native grass and flower seeds were collected by volunteers, students and staff within the Preserve near the proposed sites to maintain genetic integrity. The seed was germinated in SERG greenhouse facilities located at San Diego State University (SDSU) and Alliant International University (AIU) during the late summer and early fall of 2001. All site preparation activities commenced during fall of 2001 and were completed during the first months of 2002. Native plants propagated in the greenhouses were transplanted to the experimental sites during February and March of 2002. Supplemental irrigation was provided to the transplants once weekly during their first month and then twice monthly into the summer. This supplemental irrigation schedule continued through September 2002. Monitoring and maintenance began immediately following transplanting activities. Transplant survival counts were taken during June 2002. Non-native plants germinating within the experimental sites were eradicated with herbicide or pulled by hand as they became identifiable and, whenever possible, before fruiting. Three soil samples were collected at each experimental site during fall 2001 and spring 2002 for chemical analysis. Physical soil characteristics at the experimental sites are also compared. Physical soil data was collected during the spring of 2002 when soil tests were run within the experimental sites and immediately surrounding areas for comparison analysis.

The overall treatment comparison suggests several possible trends, but due to limited time results are inconclusive this year. Many transplants have grown very well and set seed. This is a positive indicator for long-term success of a restoration project. Soil strength was much reduced by surface tilling that incorporated wood shavings and compost. These characteristics will favor root development, plant growth and survival. The comparisons are made relative to overall plant survival. Because the transplanting of the propagated native seedlings took place during winter/spring 2002, insufficient time has passed to accurately report significant seedling survival data. Future data collection will be instrumental in generating significant conclusions.

BACKGROUND

There is a general, though not unanimous, agreement that grasslands were once more common in San Diego. The accounts of the early Spanish travelers, particularly Friar Juan Crespi and Friar Francisco Palou, highlight the abundant good pasture near San Diego. Quoting Crespi as he headed north from San Diego in July 1769, “We ascended a large grassy hill…and found ourselves on some broad mesas …all covered with grass… except here and there some very small oaks and chaparral". In addition, the Kumeyaay remember growing a now extinct domesticated large seeded grass that was an important food source. As Friar Palou noted in his memoirs, “The heathen live on grass seeds which they harvest in their season and make into sheaves as is usually done with wheat…”.

The dominant grass in many of these grasslands may have been purple needlegrass, Nassella pulchra (formerly Stipa pulchra), but disturbance was so complete before botanists arrived it is not known for certain. It may simply be the bunchgrass that was best adapted to survive disturbance. Purple needlegrass is favored by frequent fires and this may have made it a camp follower for the Native Californians who used fire extensively and intensively. Many other grasses, flowers, and forbs were also found in these grasslands, which some ecologists suggest were flower fields with grass -- not grasslands with flowers.

The conversion from perennial native grasses to weedy annuals was driven by fire suppression, overgrazing and agriculture. Purple needlegrass was apparently particularly abundant in bottomlands, the first areas converted to farmland. Much of the valley floor was converted to vineyards, orchards and irrigated or dryland farming quite early in San Diego history before it was abandoned and grazed some more.

For restoration purposes it is desirable to return native grasses to these degraded ecosystems by direct seeding or container planting. Direct seeding is problematic, requires considerable seed, and intensive management with herbicides or mowing. Establishing plants from containers is faster and more certain than direct seeding. The best approaches for planting native grass from containers have yet to be determined, but SERG has had good luck with container plants and treeshelters. The experiment now underway near the waterfall compares several additional treatments and variables including soil amendments, surface shaping (pits to collect rain) and fertilizer. This is a cooperative research project involving the Friends, the Soil Ecology and Restoration Group at SDSU, and the Environmental Studies Program at Alliant International University.

We expect it to provide new insight into the best way to restore these degraded plant communities from Mediterranean weeds and exotic grasses to native grasses and flowers.

INTRODUCTION

The Soil Ecology and Restoration Group (SERG), under the supervision of Professor Dave Bainbridge (AIU) and Mike Kelly (Friends), is the implementing agency for all tasks outlined under the awarded grant. Professor Dave Bainbridge created the experimental design and assisted during all stages of task completion. Amy Rusev managed the project implementation. Mike Kelly located the experimental sites, coordinated volunteer planting days, and eradicated non-native plants within the experimental sites through herbicide application.

There is very little literature available for the propagation and transplant of native bulb plant species. This experiment incorporates the dominant native grassland species purple needle grass, Nassella pulchra, and blue-eyed grass, Sisyrinchium bellum, as well as three bulb species (mariposa lily, Calochortus splendens, blue dicks, Dichelostemma capitatum ssp. capitatum, and goldenstar, Bloomeria crocea) that have typically been excluded in restoration efforts. In addition, two annual lupine species (Lupinus spp.) were propagated and outplanted to the two sites. The annual lupines were transplanted to ensure natural and direct seeding of the sites during fruiting. A major objective of this experiment is to analyze various soil treatments, including addition of amendments and physical soil manipulation, for their efficacy in improving native grassland and flower field plant species growth and survival.

The various treatments have been outlined in Table 1. Table 2 contains the codes used to refer to the various treatments types. There are 24 treatments in total being analyzed. Experimental subplots are 9 m2 and each received one treatment type. Each treatment was replicated six times for statistical purposes making a total of 144 experimental subplots. In addition to the treatments outlined below, half of the sites were “pitted” using hand tools following transplanting. This technique creates micro-topography that affects the water infiltration properties of the soil.

Table 1.
Outline of experimental treatments.

Table 2.
Code designation for each treatment type.

A brief description of the treatments follows in the order that each was applied. Following the removal of non-native plants from the experimental sites, amendment was added to those subplots receiving a “spread” or “tilled” treatment. The amendments were added as a 3-4 inch layer covering the subplot soil surface. The fertilizers were then applied to the surface of the corresponding subplots. Organic fertilizer (8-5-1) was added at a 350 lb/acre rate. Synthetic fertilizer (5-3-1) was added at a 400 lb/acre rate. The appropriate subplots were then tilled using an 11 horsepower self-propelling tiller. The tiller was too light to get a deep bite in some areas of highly degraded soils. Following the tilling, amendment was added to the surface of the subplots receiving the “tilled/spread” treatment as a 3-4 inch layer covering the subplot soil surface. Lastly, half of the subplots were hand pitted.

MATERIALS AND METHODS

Site identification and seed collection/germination

Native grassland and flower field seed was collected by AIU students as part of a restoration ecology class and SERG personnel and Friends employees during the spring and late summer of 2001 (Figure 1). The seed data is presented in Tables 3 and 4. The seed was catalogued and distributed between the greenhouse facilities at SDSU and AIU (Figure 2). The germination of this seed and the propagation of native plants commenced during late summer of 2001. Beginning in late September of 2001, the two experimental sites were identified within Los Peñasquitos Canyon Preserve.

Table 3.
Seed collected by SERG staff, students from AIU, Friends of Peñasquitos and volunteers for the Los Peñasquitos Canyon Flower Field Study.

Figure 1. AIU students collecting seed.

Figure 2. Lupine seeds being sorted.

Pre-experiment site descriptions

The eastern site (site #1) was dominated by storksbill, Erodium cicutarium, and to a much lesser extent wild oat, Avena fatua. A dense stand of wild oat, Avena fatua, surrounds site #1. The western site (site #2) was dominated by Avena fatua and exhibited signs of extensive gopher activity. A fairly dense occurrence of the native rhizomatous saltgrass, Distichlis spicata, was also present at site #2. A split rail fence constructed by the Friends surrounds site #2. Neither site #1 or #2 supported many native plant species. However, the few individuals present were flagged and avoided during all site preparation and planting activities.

Site preparation

The non-native plant species on both sites were mowed using a high weed self-propelled mower (Figures 3, 4). The resultant biomass was removed from the sites and placed in a

Figure 3. Site 1 following mowing of weeds.

Figure 4. Site 2 following mowing of weeds.

nearby area with a high density of non-native plants. The subplots within each experimental site were plotted out to be 9 m2 squares and identified by a buried marker with a number label on the northeast corner (Figure 5). The experimental treatments were assigned to subplots numbered 1-144 with random distribution using a computer statistics program. Maps were made of the experimental sites outlining each subplot’s treatment. A SERG crew ranging from 2 to 6 people implemented all treatments.

Figure 5. Subplot labeling system.

The City of San Diego Park and Recreation Department organized the delivery of approximately 30 cubic yards of Miramar city landfill compost (Figure 6). This compost is produced from the “green” waste from the municipal area surrounding the landfill. This vegetative waste is composted in windrows for 6 or more weeks to kill weed seed before it is made available to the public. The compost was distributed between the two experimental sites. In addition, SERG ordered thirty cubic yards of untreated wood shavings from A-1 Soil Aggregates that were delivered and distributed between the two experimental sites (Figure 7). Organic and chemical fertilizers were distributed to the subplots. The amendments were applied in a 3-4 inch surface layer to the sites receiving the “tilled” and “spread” treatments (Figures 8 and 9). SERG employees then tilled the corresponding half of the subplots and distributed the remaining soil amendments in a 3-4 inch surface layer to the subplots receiving the “tilled/spread” treatment according to the experimental design (Figures 10 and 11).

Figure 6. Miramar landfill mulch delivery.

Figure 7. Wood shavings delivery.

Figure 8. Application of soil amendments to experimental subplots (site 1).

Figure 9. Application of soil amendments to experimental subplots (site 2).

Figure 10. Tilling following amendment application (site 1).

Figure 11. Tilling following amendment application (site 2).

Planting

The subplots were ready for transplanting by the middle of February 2002 following completion of site preparation activities. Before transplanting the greenhouse seedlings, holes were dug to a depth of 10-14 inches and pre-watered with approximately one-third to one-half gallons of water (Figure 12). The greenhouse seedlings, carefully removed from their containers, and bulbs were transplanted to the pre-watered holes (Figures 13 and 14). Approximately half of the bulb species were transplanted to holes lined with ¾-inch chicken wire (Figure 15). Some bulbs were deposited as groups into large holes lined with the wire. A few of the bulb species received plant protectors but more often were marked with color pin flags for future monitoring and irrigating purposes. After being “tamped” in with moist surrounding soil, the transplants were watered again with approximately one-half gallon water (Figure 16). Plant protection, in the form of recycled plastic cylinders, were installed above ground around each non-bulb transplant (Figure 17). Plant basins were created around each transplant to facilitate and concentrate water delivery to the plants during natural precipitation events and supplemental irrigation (Figure 18). Following the planting, half of the sites were “pitted”, a process by which micro-topography is created in an area using hand tools. Pitting affects the water infiltration properties of the soil. SERG employees, AIU students and Friends coordinators and volunteers worked together during transplanting activities through the months of March and April 2002 (Figures 19-27). Table 5 contains all transplanting data, including details related to the various bulb treatments.

Figure 12. Prewatered transplant holes.

Figure 13. Blue dicks bulbs.

Figure 14. Greenhouse seedlings for transplanting to experimental sites.

Figure 15. Chicken wire baskets used for bulb transplant.

Figure 16. Transplants following watering.

Figure 17. Purple needle grass transplants following watering and basin creation.

Figure 18. Lupine transplant following watering and basin creation.

Figure 19. Planting activities (site 1).

Figure 20. Planting activities (site 1).

Figure 21. Volunteer planting day (site 1).

Figure 22. Volunteer planting day (site 1).

Figure 23. Volunteer planting day (site 1).

Figure 24. Volunteer planting day (site 1).

Figure 25. Planting activities at site 2.

Figure 26. Site 1 planted.

Figure 27. Site 2 planted.

Table 5.
Planting field data for the Flower Field Study.

The average number of outplantings per subplot is approximately twelve. This density is fairly representative of healthy grassland habitat.

Supplemental irrigation

Supplemental irrigation was supplied to the native plants once weekly during the first month following transplant and then continued twice monthly. This regime will continue through the month of September of 2002. Water for supplemental irrigation was most often taken from Peñasquitos Creek using a Honda water pump to fill a 180-gallon water tank (Figures 28 and 29). Using a truck, the full water tank was delivered to the transplants at the two experimental sites using pumps and hoses (Figure 30). Approximately one-half to one gallon of water was supplied to each plant during every supplemental irrigation event. This equated to using from 900 to 1080 gallons of water. Natural precipitation was monitored and if a significant rainfall event occurred, the irrigation schedule was modified to account for the natural delivery of water to the transplants.

Figure 28. Pump set-up near waterfall on supplemental irrigation day.

Figure 29. Filling water tank from Peñasquitos Creek using a pump.

Figure 30. Watering site 2 with full water tank, hoses, and pump.

Maintenance

During supplemental irrigation field days, the non-native plants germinating inside the plant protectors and within the transplant basins were hand-pulled (Figures 31 and 32). Non-native plants germinate readily around the transplants due to the availability of water through irrigation. David Bainbridge hoed the sites twice, SERG employees hand-pulled non-native plants during supplemental irrigation days, and Mike Kelly eradicated non-native plants growing between transplants through herbicide application.

During the spring of 2003, the plastic plant protectors will be removed from all transplants at the two experimental sites to avoid impeding natural plant morphology. Once the transplants have become established at the sites for over a year, herbivory should not cause plant mortality.

Figure 31. Hand-weeding experimental sites.

Figure 32. Removing plant protector in order to hand-weed.

Monitoring

Spring monitoring of the sites involved recording overall plant survival, non-native plant germination, and chemical and physical soil changes corresponding to the various treatment types. Monitoring of the Flower Field Study sites was completed during the spring and summer of 2002 and will continue during the spring annually for the next two years by Professor Dave Bainbridge and AIU students. A final report containing analyses from the monitoring results will be completed during the summer of 2004.

Transplant Survival

Because the bulb plant species did not flower this year but may have survived, below ground survival was not monitored during spring of 2002. The plant survival data used to determine the most successful treatments for the 2001/2002 year is based upon Nassella pulchra and Sisyrinchium bellum. These species are easily monitored for survivorship due to perennial above-ground structures.

Survival data relies on quantitative sampling. Each subplot was visited during spring of 2002 and each transplant was recorded as either “alive” or “dead”. If any green growth was apparent on a transplant, it was documented as being alive.

Chemical Soil Analysis

During the fall of 2001 and spring of 2002, three soil samples from each of the two experimental sites were sent to A&L Western Agricultural Laboratories in Modesto, California for “complete” analysis. Complete analysis includes examining organic matter, estimated nitrogen release, phosphorus, potassium, magnesium, calcium, sodium, soil pH, buffer pH, C.E.C, percent cation saturation, nitrate nitrogen, soluble salts, excess lime, sulfate sulfur, zinc, manganese, iron, copper and boron. The fall 2001 and spring 2002 analyses can be compared and examined for changes attributed to the experimental treatment types, removal of non-native plants, and addition of native perennial plants. Chemical soil analysis will only by presented as baseline (fall 2001) and first spring (spring 2002) values. Because soil characteristics change gradually over time, examining future soil chemical analyses will be more valuable in comparing the ultimate effects produced by the various experimental treatments.

Physical Soil Analysis

Monitoring of physical soil characteristics included analyzing and comparing soil strength, soil moisture retention, soil infiltration, and soil temperature between the various treatment plots.

Soil Strength

The treatments selected for this experiment were chosen to reflect the typical choices facing a restoration designer. An impact penetrometer provides a simple measure of integrated soil strength. A hammer drops on a pointed pin and the depth reached for each impact is recorded. This integrated measure is a useful indicator of the conditions a root tip will encounter as it tries to extend further into the soil. Measurements were made in July using the SERG impact penetrometer, three tests were done for each treatment examined and the means are used for figures. Only the more significant treatments were measured at this time. The lack of rainfall meant that little improvement would be seen on the mulch and wood shaving surface treatments. These will require rainfall and time to improve.

Soil Infiltration

The soil infiltration at the Flower Field Study sites was measured with micro-infiltrometers. These 5.7 cm acrylic tubes with cm scales are placed into a circular slot cut in the soil, sealed with an initial wetting and then filled with water. The water drop is measured every minute for 10 minutes or until the infiltrometer is dry or unreadable from debris.

Only the more distinctive treatments and controls were measured. Over time we anticipate the infiltration of the soil in the wood shaving layer and mulch layer plots will also improve significantly, but with effectively no rain this year there has been very little biological activity even at the soil/mulch interface. These will be checked in future years.

Soil Moisture Retention

In July the moisture in planting spots was measure 10 days after irrigation using a simple conductivity meter with a scale from 1, dry to 10 wet. In addition, as a visual measure, core soil samples were taken from the various treatment plots (Figures 33 and 34). The depth of moist soil was noted. This test was used to help determine the need for supplemental irrigation.

Soil Temperature

Temperatures were measured at the soil surface and at 20 cm above the surface using a digital thermometer. Temperatures were taken in the morning, but during the late afternoon they would be much more dramatic.

Figure 33. Core soil sample taken to determine moisture retention.

Figure 34. Core soil sample taken to determine moisture retention.

RESULTS

Transplant survival
During the months of May and June 2002, each treatment plot within the two Flower Field Study experimental sites was visited and every live transplant was documented. Using the planting data from the spring of 2002, all missing non-bulb plants from the subplots were considered dead. Table 6 presents the survival data for the transplants.

Table 6.
Survival data for the Flower Field Study.

Table 7 presents the survival data for the Flower Field Study transplants by treatment type.

Table 7.
Percent survival by treatment type.

Chemical Soil Analysis

Tables 8 and 9 present the baseline and first spring chemical soil analysis results.

Table 8.
Chemical soil analysis results (OM through C.E.C.).

Soil Strength

The improvements at the Flower Field Study sites are shown in Figure 35. The zero impact column reflects the free drop of the pin under the weight alone, without a drop hammer impact. Soil penetration was almost double after 20 hits. This clearly indicates a condition more conducive to increased plant survival and growth.

Incorporating the mulch into the soil appears to be more effective than simply spreading it on the surface (Figure 36). Also, the amendment type used apparently makes a difference regarding the improvement in soil strength (Figure 37).

Figure 35. Soil strength means comparison by tillage treatment.

Figure 36. Soil strength means by mulch application.

Figure 37. Soil strength means by mulch type.

Soil Moisture Retention

Soil moisture retention varied quite dramatically depending on the type of amendment used, ranging from the highest readings found on plots with sawdust spread on the surface to the lowest readings found on those plots where no mulch was added. Results are shown in Figure 38.

Figure 38. Flower field plots mean soil moisture 10 days after irrigation.

Soil Infiltration

Soil infiltration results indicate that both tilling and tilling mulch into the soil increases infiltration capabilities of the soil, thus providing increased water flow to the roots of plants. All the data was incorporated in a data series and analyzed using Superanova. The differences are presented in Table 10.

Table 10.
Soil infiltration at the Flower Field Study sites (7/02).

Soil Temperature

Soil temperature results demonstrated that the use of surface mulch decreased the large high and low temperature ranges that are found in soils without a mulch covering. The mulch acts as a buffer that moderates soil temperature. Table 11 presents the soil temperature data.

Table 11.
Soil temperature data for the Flower Field Study sites.

DISCUSSION

Because the transplants have been established at the Flower Field Study experimental sites for less than six months, the survival data will need to be analyzed in future years to produce definitive conclusions. Often, early transplant mortality can be associated to poor seedling health prior to transplanting or overexposure of the root system during transplanting activities rather than actual treatment impacts. Therefore, the survival data presented in the Results section should be considered baseline data and additional monitoring will continue over the next two years. It will be more useful for statistical purposes to analyze future monitoring results in order to find significant trends that can be attributed directly to the various treatment types.

Thus far, statistical analysis of spring monitoring 2002 data has resulted in one significant finding and several trends during the experiment’s first implementation year. The addition of organic fertilizer reduced the survival of blue-eyed grass (Sisrinchium bellum). Neither the addition of soil amendment nor pre-planting tillage seemed to be significant in affecting overall transplant survival at this point in time. Some trends were found that will be statistically reanalyzed following future monitoring. These included three observations: 1) wood shaving amendment and 2) pitting increasing purple needle grass (Nassella pulchra) survival, and 3) no amendment addition increasing blue-eyed grass survival.

The plastic plant protectors have been beneficial, particularly at experimental site #2. Transplant herbivory is common within restoration sites because the young shoots are sought after by herbivores. Two factors have contributed to the high rate of herbivory at the experimental sites: 1) the winter of 2001/2002 was unusually dry in San Diego County contributing to a scarcity of young green plants and 2) the supplemental irrigation provided to the transplants concentrated the availability of green plants within the experimental sites.

The chemical soil analysis results have shown no significant changes in soil chemistry during the first year of the experiment. Magnesium levels are very high in general and are consistent with other soil samples that have been analyzed throughout Los Peñasquitos Canyon. This is most likely a result of the intense historical agriculture that occurred in the canyon.

One of the primary goals in ecological restoration is to reduce the soil strength on degraded sites and to improve root growth and plant survival. Soil strength is a complex soil characteristic that reflects soil structure, soil composition (particularly organic matter), soil compaction and soil moisture. Agricultural operations, grazing and traffic (bicycle, foot or vehicle) can all seriously increase soil strength by degrading soil structure, increasing compaction, reducing soil organic matter, collapsing soil micro and macro-pores and limiting moisture entry into the soil.

The amendment types used affected the improvement in soil strength. Wood shavings were better than the mulch from the city. This would be expected because the particle sizes are smaller and more easily incorporated in the soil. This provides better conditions for moisture penetration and reduces reconsolidation.

The general desirability of adding organic matter as mulch in a surface layer or incorporated in the soil was confirmed through simple soil strength tests. The use of spot applications can be valuable when costs prohibit general application; however, if possible, mulch or wood shavings should be first incorporated in the soil and then added as a surface layer.

Tillage alone has been shown to reduce soil strength and improve root development and plant growth. This is why farming almost always includes primary tillage before planting. The improvements decrease relatively quickly as soil settles under the influence of rain, gravity and foot and hoof prints.

Another critical issue for degraded soils is improving infiltration of water into the deeper soils for plant root uptake, growth and long term survival. Soil structure degraded by agriculture, trails and overgrazing can lose almost all micro and macro pores and become virtually impermeable to water. One of the reasons soil treatment improves survival and growth is the improvement in soil structure and moisture capture and retention.

The soils in the two experimental sites are similar, with no statistically significant difference in controls between the east and west plots. The wood shavings and mulch incorporation are significantly better than all other treatments. Tillage alone is significantly better than the controls. Tillage alone almost doubles infiltration, although this improvement will have a limited lifetime of a few years.

The incorporation of mulch almost triples infiltration and wood shavings quadruples infiltration compared to controls. Wood shaving incorporation improves infiltration ten times over the compacted soils in the old trail segment. These dramatic improvements in moisture movement into the soil have a profound effect in improving plant survival and growth and are long lasting. The improvements in surface mulch and surface wood shavings plots will eventually fall somewhere between the controls and incorporated treatments, but only after fungi, algae and other soil organisms and insects develop and create new micro and macro-pores.

The benefits of surface and incorporated mulch and wood shavings are clear. The responses on the east and west plots were somewhat different, perhaps because the west plot has more litter and roots from the salt grass. In both cases, the plots without amendment retained only a third as much moisture as the wood shavings and mulch plots and long term survival of plants is likely to be limited.

Soil treatments can also affect soil microclimate in other ways that improve plant survival. Temperature affects soil moisture retention, plant stress and plant growth. Mulches often improve conditions for plants by reducing nighttime drops in temperature and reducing daytime heat gain and plant stress.

Even in the morning the soil temperatures with mulch or wood shavings surface layers were 4-5° C cooler. In the afternoon on a hot summer day the difference might reach 50° C. The reduced soil temperatures reduce moisture loss from the soil and the plant and reduce plant stress. This can result in improved plant survival and growth. The protective mulch or wood shavings also keeps soil temperatures warmer at night. This can also reduce stress and increase survival.

These interesting findings are extremely useful for incorporation into ecological restoration methods. Experiments such as this are invaluable in making restoration efforts more efficient and effective. As future monitoring continues, more significant conclusions can be drawn that will aid in returning degraded lands to native habitats supporting a diverse assemblage of plants and animals.