Interaksi Spesies dalam Komunitas Tanaman

Transkripsi

1 Interaksi Spesies dalam Komunitas Tanaman Dr. Akhmad Rizali Materi: Pengantar Terminologi ekologis suatu sistem pertanaman: suatu komunitas yang dibentuk oleh suatu kompleks populasi tanaman, gulma, serangga, dan mikroorganisme yang saling berinteraksi Interaksi di antara populasi komunitas tanaman, dibangun dari macam interferensi yang berbeda, sehingga terbentuk karakteristik komunitas, yang disebut emergent qualities, dan hanya ada pada tingkatan komunitas Secara khusus beberapa penelitian terdahulu lebih difokuskan pada populasi tanaman daripada komunitas, yang sebenarnya itu merupakan bagian dari komunitas 1

2 Pengantar Sehingga kehilangan kemampuan mempertimbangkan untuk menggerakkan interaksi komunitas yang bermanfaat bagi sistem pertanaman Selama ini yang dipertimbangkan hanya interaksi yang merugikan (gulma, hama pemakan tumbuhan, penyakit) Pendekatan konvensional akan memperkecil interaksi dibandingkan pendekatan secara agroekologi yang mencoba untuk memahami interaksi spesies dalam konteks komunitas yang lebih besar Interferensi pada level komunitas Dua tipe interferensi : Removal hilangnya beberapa sumber daya oleh satu atau dua organisme yang saling berinteraksi Addition satu atau dua organisme menambahkan beberapa struktur atau unsur kedalam lingkungan Keuntungan pendekatan interferensi: mendapatkan pemahaman yang lengkap mengenai mekanisme interaksi Gabungan dari interferensi dapat memberikan pengaruh terhadap komunitas tanaman 2

3 Cara interferensi yang mendasari interaksi spesies dalam komunitas INTERFERENCE Addition impact Allelopathy Food source for beneficials Removal impact Competition Parasitism Herbivory Combined removal and addition Mutualism Microhabitat modification Kompleksitas dari Interaksi Interaksi yang terjadi sangat kompleks dan sulit dilihat Contoh: Grass clover 3

4 Relative dominance of grass (Lolium rigidum) and clover (Trifolium subterraneum) in relation to levels of nitrogen fertilizer Coexistence Populasi dari organisme yang memiliki kemiripan, biasanya akan berbagi habitat yang sama meskipun saling tumpang tindih niche Ecologists widely accept the idea that selection for coexistence may be the rule more than the exception Many domesticated species have evolved in polycultures Understanding mechanisms of interference that allow coexistence will help us design multiple crop communities Combine species with slightly different physiological characteristics or resource needs to promote coexistence 4

5 Mutualism 3 Types: Inhabitational one mutualist lives wholly or partly inside the other (eg. Rhizobium bacteria and leguminous plants) Exhabitational organisms are relatively independent physically, but interact directly (eg. flowering plant and its insect pollinator) Indirect interactions among a set of species modify the environment in which they all live to the benefit of the mixture; involve more than 2 species (eg. polyculture agroecosystem) Mutualism Facultative mutualisms: all members can survive alone but benefit from interaction Often mutualisms help species avoid some negative impact Increase resistance of entire system to negative impacts of pests, diseases and weeds 5

6 Mutually Beneficial Interferences at Work in Agroecosystems Beneficial Interferences of Cover Crops Beneficial Interferences of Weeds Intercropping Beneficial Interferences of Cover Crops Cover crop = plant species (usually grasses or legumes) grown in pure or mixed stands to cover the soil of the crop community for part or all of the year Green manure = cover crop tilled into the soil to add organic material Living mulch = cover crop grown directly with other crops Reduce soil erosion; improve soil structure; enhance soil fertility; suppress weeds, insects, and pathogens May be beneficial at some times while detrimental at others (see CASE STUDY rye/bellbeans) 6

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8 Beneficial Interferences of Weeds With proper management, weeds can serve role of cover crop Modification of the Cropping System Environment Control of Insect Pests by Promotion of Beneficial Insects A. Modification of the Cropping System Environment Weeds protect soil surface from erosion take up nutrients that might otherwise be leached add organic material selectively inhibit development of more noxious species through allelopathy 8

9 Control of Insect Pests by Promotion of Beneficial Insects Certain weeds should be regarded as important components of the crop community because of the positive effects they have on populations of beneficial insects Intercropping 9

10 Intercropping Two or more crops planted together may reduce need for external inputs Mostly used in the tropics Corn bean squash polyculture example growing 3 crops together gave higher total yield land equivalent ration (LER) > 1 Understanding ecological foundation of the interactions in polycultures is key to returning its prominence to agriculture Penggunaan Interaksi Spesies untuk Sustainabilitas Tantangan bagi agroecologists adalah meletakkan pemahaman ekologis ke dalam konteks sustainabilitas 10

11 Terimakasih 11