Questions: What is the accuracy and reliability of the commonly used random soil sampling methodology for predicting seedling density, species richness and composition of the emerging seedling community?
Location: Lake Kraenepoel, western Belgium.
Methods: We compared density, species composition and observed and rarefactioned species richness of the seedling community emerging on a soft water lake bed exposed after drainage with the seedling community germinating in the laboratory from random soil samples in the same plots.
Results: Seedling density did not differ between the two methods and there was a significant correlation between seedling density on the exposed lake bed and in the soil samples. This indicates that future seedling density can be reliably predicted based on soil sampling, in particular for the most abundant species. The most frequently occurring and abundant species among the seedlings in the soil samples were also the most frequent and abundant species germinating on the exposed lake bed. In contrast, species richness was much higher on the exposed lake bed than in the soil samples, and this difference was still significant for annual species after correction for differences in sampling intensity by rarefaction. We found no correlation between the number of species retrieved by the two methods. Although seedlings of rare and target species emerged on the lake bed, random soil sampling clearly failed to detect seeds of most of these species.
Conclusions: Random soil sampling at a commonly used intensity and using the standard germination conditions can accurately predict future total seedling density and the density of the most abundant species. However, the method is not reliable for predicting the probability of establishment of populations of uncommon species. When executing a seed bank study, sampling intensity and germination conditions need to be adapted to the nature and the level of detail of the research question to be answered.
Kwa nini ni muhimu kutumia mbinu ya sampuli ya udongo ya random ili kutabiri idadi ya mimea, utajiri wa spishi na muundo wa jamii ya mimea inayoibuka? Mahali: Ziwa Kraenepoel, magharibi mwa Ubelgiji. Kwa mfano, tulilinganisha wiani, muundo wa spishi na utajiri wa spishi zilizochunguzwa na kuondolewa kwa jamii ya mbegu zinazojitokeza kwenye kitanda cha ziwa la maji laini baada ya kuondolewa na jamii ya mbegu zinazozaliwa katika maabara kutoka kwa sampuli za udongo za random katika viwanja sawa. Matokeo: Wingi wa mbegu haukutofautiana kati ya mbinu mbili na kulikuwa na uhusiano mkubwa kati ya wingi wa mbegu kwenye kitanda cha ziwa kilichofunuliwa na katika sampuli za udongo. Hii inaonyesha kwamba wiani wa mbegu ya baadaye inaweza kutabiriwa kwa kuaminika kulingana na sampuli ya udongo, hasa kwa spishi nyingi zaidi. Aina ya kawaida na nyingi kati ya miche katika sampuli za udongo pia walikuwa aina ya kawaida na nyingi kuota juu ya wazi ziwa kitanda. Kwa upande mwingine, utajiri wa spishi ulikuwa juu zaidi kwenye sakafu ya ziwa kuliko katika sampuli za udongo, na tofauti hii ilikuwa bado muhimu kwa spishi za kila mwaka baada ya marekebisho ya tofauti katika nguvu ya sampuli kwa rarefaction. Hatukupata uhusiano kati ya idadi ya spishi zilizopatikana kwa njia hizo mbili. Ingawa miche ya spishi nadra na za lengo ilionekana kwenye sakafu ya ziwa, sampuli za udongo za nasibu zilishindwa wazi kugundua mbegu za spishi nyingi hizi. Kwa mfano, sampuli za udongo za random zilizochukuliwa kwa kiwango cha kawaida na kutumia hali ya kawaida ya kuota zinaweza kutabiri kwa usahihi wiani wa jumla wa mbegu za baadaye na wiani wa spishi nyingi. Hata hivyo, mbinu hiyo haitegemeki kwa kutabiri uwezekano wa kuanzishwa kwa idadi ya spishi zisizo za kawaida. Wakati wa kutekeleza utafiti wa benki ya mbegu, kiwango cha sampuli na hali ya kuota lazima ikirekebishwe kwa asili na kiwango cha undani wa swali la utafiti linaloweza kujibiwa.